Cooling fan considerations
09-06-2016, 05:41 PM
#1
Race Director
Thread Starter
Cooling fan considerations
This thread is meant to consolidate as much information as possible regarding cooling...and especially fans.
As cooling because a larger point of consideration with my 383 build, I've looked at the issue of cooling (especially idle heat) ever since. My car DOES have a Champion dual-row radiator -- which cools just fine w/o the A/C....AND with the A/C as long as the car is moving.
My thread on BUDGET radiators can be found here. Please know this linked thread was -- in no way -- meant to include DeWitts (or Griffin or BeCool) radiators. It's common knowledge that DeWitts is USA made and better quality. The budget thread was intended to help guide those unable to consider more expensive options. Considering cheap (and how many) C4s are on the road, I expect budget considerations to increase over time. That said, I've reached the 5-yr mark on Champion ownership and don't have any complaints. However, it's a garage-parked car with 25k on the clock since installation. I did have to purchase another drain **** as the original mini-weld failed on the drain-**** T-handle.
Now...lets consider fans.
Like others who've complained about heat -- even in cars with non-modified engines -- the C4 has it's challenges due to it's bottom-feeder air inlet. People worry about higher temps all the time. First, we should say newer engines WERE DESIGNED to run hot for the purpose of improved emissions. Main and auxilary fans were programmed (by the factory) to come on at higher temps -- like the 220's/230's. If you're not seeing temps higher than 240ish, you likely don't have a mal-functioning cooling system.
The first things to do -- if you want to maintain optimal operation -- is perform regular flushes AND cleaning of the radiator area. In short, the goal is to remove debris in front of and around the radiator. Usually, this will require removal of the top radiator housing so you can access the space BETWEEN the radiator and the A/C condenser.
The condenser LOOKS like a radiator and sits in front of it. FWIW, it cools your A/C's freon in much the same way a radiator works. When doing this, the air temp across it's fins/coils heats up. This has the same effect as driving your car on a much hotter day. The good news is the air temps still stay well below the HOT coolant in the radiator. As such, the air is still cool enough -- in relation to the coolant temp -- to pull heat off the coolant. Still, it's close enough that debris can block enough air flow to compromise it's ability to perform it's function in the hotter climates.
Air must flow across the radiator for it to work. In cooler temps AND when the car is moving, air flows across your radiator through the entrance below the C4 bumper. It should also be said that the air dams aide in this operation by diverting some of the air UPWARD into that entrance. If you have problems with cooling at speed AND your dam is missing, consider replacing it first. This is also a cold air scoop (sold aftermarket) that has been shown to provide minor assistance in this function. It should not be considered necessary for proper air flow. Most people who tried it (or built a version of their own) are happy with the additional cooling "help".
All C4's came with a main radiator. These fan(s) sit behind your radiator and pull air through it (like a ceiling fan pulls air in your windows). Some cars were optioned with the RPO "B4P" auxiliary fan . It's a second fan that sits in front of the A/C condenser PUSHING air through it. The rear, main fan(s) are shrouded. A shroud is a "wall" that extends from your fan to the edge of the radiator. The function of a shroud is to prevent air from bypassing the fan. When the car is motionless (or moving slowly), air isn't flowing through your radiator. When the fan kicks on, the shroud enables the fan to pull air from a larger surface of the radiator. When fully shrouded, air should pass across the entire network of fins.
Some will notice the shroud doesn't extend to the bottom of the radiator. Part of the reason NOT to block "non-fanned" sections of the radiator is to improve flow when the car IS MOVING. Because our cars are "bottom-feeders", air is more likely to flow across the bottom, making it a good section to leave unblocked. (In looking through this forum, it would appear that only people who race have considered another configuration than a stock shroud.)
Let's get back to the fans....
In the earliest C4s, I believe the main fan is controlled by a cylinder-head-mounted cooling switch? It's a mechanic switch with an internal "button". When it gets hot enough, the button "pops", swaps direction, and completes an internal circuit. When a ground wire (from a fan) is attached to this type of switch, it's grounded when the engine gets "hot". (This is based on a M.A.Motorworks instruction sheet I have). So you know....Coolant switch temperatures/ratings can vary. In an attempt to document several of the options, I created this thread. Take a look at it -- if you are considering another fan switch.
For later L98s and all LTx cars, the main fans are controlled by your car's computer. As such, it is possible to change the turn-on temps by altering the appropriate parm(s) in the computer code. I lowered mine to trigger around 190. (The reason I say "around 190" is that coolant temps aren't consistent throughout your engine. For L98's they are hotter in the heads and the rear. LTx cars use reverse cooling. ZR1 cars aren't something I've looked at in this regard. I have to assume they have their own spots where the coolant is hotter than others. This point is of some consideration because the purchase of an alternate coolant switch may not have the results you expect. (This is covered a bit more in the link provided above.)
L98 main fans are 16" single fans. (Correct me if that doesn't apply to all models!) Starting in 1990, fans were converted to a dual setup. I'm going to guess these are considered 11" fans. I'm also going to guess the dual fans were used on both LTx and ZR1 models.
On of the things you'll notice if you look at aftermarket fan options is dual fans pull more air than single fans. That's true even if the single fan is larger. Most aftermarket fans claim anything from 1200-3600 rpms. People often tout the use of early Taurus/Mark VII fans for cooling. DeWitt's posted an interesting comparison of these older fans -- compared to SPAL 16" and dual 11" on their website here.
The biggest thing I get out of the link is to notice amperage and performance drop -- as static pressure increases. Static pressure is resistance that's created when sitting obstructions in front of your fan -- like radiators and condensers. When you look at DeWitt's graph...and any aftermarket fan that includes specifications, you'll find yourself wondering "How much static pressure is in MY motor?" That's a good question...and likely plays a role in any alternative fan selection. One site I found claims the average static pressure is between .4 and .7 mm H20. I am unable to verify this nor should it be more than a guide -- since your specific car may vary.
In addition to static pressure, notice fan amperage. Normally the amperage is higher when the fan is capable of pulling more air. Just like an engine, it takes energy to perform mechanical motion. The more work done, the more energy it takes. Also, like engines, there are various designs that can be somewhat more efficient, but I think it's still good practice to notice power requirements when selecting a fan. This will help determine wiring (gauge) requirements, fuse requirements AND whether it's likely to out-perform your current unit.
My own observation (and digging through this forum) has led me to believe there aren't many fans that are better-than-stock. Even if you compare stock and aftermarket CFM ratings, you probably aren't looking "further down the chart" where static pressure is .4 or greater.
When you consider the construction of fans, curved blades are quieter. But each blade may pull more air via it's "cupped" design. Fans with more blades and/or "cupped/curved" area will pull more air. In one study I read, it was suggested that straight blade fans pull air through more "directionally". By contrast, curved blade fans expel air outwardly/radially. This study was done on smaller fans but still seems relevant to larger ones. (This makes me wonder if better dispersion allows air to bend around the motor better and exit through side/hood vents? IDK...I'm just posing the question.)
I like the option of a curved/quieter fan but CFMs are normally the better goal. There are a couple of SINGLE fans that tout 3000-3600 cfms. I doubt this claim due to the amperage they draw. I suspect it's more likely they pull closer to 2k CFM. If you consider my guess true, that brings them more in line with SPAL fans -- which appear to be the most prominent in aftermarket appeal.
For L98's, DeWitt's repackages and sells (what I believe to be) the best straight-blade SPAL fan. It looks like they splice on a factory end and package (include) an adapter mounting shroud. This makes for an easy installation which warrants their somewhat higher price. They also (probably) still sell the fan adapter alone. (part# SP012) It's the silver mounting flange in this DeWitt's link. Basically, you bolt a SPAL fan to this flange...which is shaped/drilled to match your factory shroud. There are lots of ways to mount a fan, but this doesn't require fabrication or imagination.
Later C4s are equipped with dual fans. DeWitts has an option for that too....though I'm unaware of any upgrade in performance compared to your stock dual fans. BTW, this means upgrade "kits" shouldn't be considered as interchangeable between early/late cars due to the conversion from single to dual fans!
Earlier, I mentioned dual fans perform better than single fans. With an increase in power for the ZR1 (and LTx) cars, I think it's likely that the extra power (heat) resulted in the change to dual fans. This too, is something I can't prove. But, it makes sense on a bottom-feeder with increasing heat production.
For people considering an upgrade to the L98 fan, a dual fan might be the best option. Before considering that option, take notice to their depth as you MAY run into the need to address clearance issues with your power steering reservoir and/or your A/C dryer (the shiney silver thing in front of your A/C).
I am considering conversion options myself. In doing so, I believe the stock L98 fan MIGHT have decent static pressure "resistance". If so, it would explain the larger-than-aftermarket motor AND why so many are disappointed with aftermarket fan selection. Even if you pick a fan advertised higher than the 11 amp, 1700 cfm stock main fan, it might not perform better when loaded behind your radiator. That's because ratings are usually with no static pressure (in free air).
(Note: I haven't confirm the L98 stock amperage/CFM either. But the figures posted are what's commonly found in this forum. I've also seen 1400 cfm posted. Considering the amperage, 1400 might be more realistic. Again, the factory motor is substantial so it probably also has good performance under load (mounted) when compared to aftermarket units nearing 2k cfm.
Again, one key is to consider amperage. SPAL has one curved blade fan rated at 45 amps (30102803HO) and another curved blade unit rated at 22 amps (30202082). 2082 lists the same "1918 cfm" as the DeWitt's conversion. PDF documentation shows the curved fan slightly higher. That might make is a better option in terms of noise and flow. The 2803HO option only shows a bump to "1953 cfm". But, on both of these fans, you may find higher flow ratings. (Don't be fooled by m/hr versus CFM ratings.) Still the PDF documentation on the 2082 (and 2036 fan likely used by DeWitts) show higher flow ratings (2360 cfm and 2470 cfm respectively). The curved blade draws a bit more power, has more substantial blades, and might have better static pressure performance? The 30102803HO fan is SPALs best upgrade option -- despite it's 1953 cfm rating. If you compare the PDF ratings, the 2803 has DOUBLE the static pressure performance at 1 mm H20 compared to the (DeWitt's?) straight-blade unit. I haven't been able to find documention on the lower-priced, curved-blade 30102082 unit, but it's probably between the two. Amperage ratings range from 22 to 26 on these fans...so that extra 2-4 amps may just be worth it -- when the fans are under load behind your radiator.
It would probably be easier if I created a picture/comparison chart to understand the paragraph above. In lieu of that, I'll try this....
Stock L98 main fan
11 amps, 1400-1700cfm (750-800 with .7 static pressure performance?)
DeWitt's L98 upgrade (straight blades with factory plug and mount kit)
21.6 amps, 2360 cfm (1180 with .7 static pressure performance)
30102082 SPAL (curved blades)
22 amps, 2470 cfm (I estimate 1300 cfm under .7 static pressure load)
30102803HO SPAL (curved blades)
49 amps (w 100 amp turn-on spike), 3310cfm no load cfm performance (~2250 cfm .7 static pressure performance)
If anyone knows the LTx ratings and wants to compare them to SPAL/DeWitt's options, let me know and I will add it to this post.
I also like the Derale 17" option (part 16217). It's a 2-spd fan offering 2400/1800 cfms....rated at 23.5/17.4 amps. I believe this fan could be mounted on the front side of the factory fan cage (after removing the L98 fan) and mounting it with spacers to the factory location. (It would probably mount best, if you had a table saw to remove the small lip on the front of the factory fan cage.)
Flex-a-lite is another manufacturer that sells some high-power options.
Dual 11" fans add quite a bit more air flow than the single options listed above. (Again, these are used on later LTx/ZR1 models. So, it's a better setup.) On SPAL's website, 11" fans flow as much as 1300cfm under load(2780cfm no load). Maybe 65-70% more than an L98 single fan?
Running amps for a dual setup total ~30A, so they are more efficient too. (You can double the CFM with less than 50% more amps.) In this thread, you'll see long-time member jfb measured the amperage of the factory dual 11" fans @ 14amps apiece.
FWIW, people HAVE put dual 11" fans in C4s that weren't originally equipped with them as shown here. C3's often used a dual setup out of the Ford Focus. It appears to be a lower-power version of the LT1/ZR1 setup -- though still higher in flow than the single 16" setup. They look to rank in the less-expensive dual 11" setups which flow 2750-2800 (zero resistance) TOTAL. (This is still higher than stock single fans AND most aftermarket single 16" fans.) It would seem likely that the DeWitt's dual 11" setup would be fairly equivalent to the late factory setup. If this is designed to go in early cars, it could be a good option too. (FYI: A tester recently showed the DeWitt's dual 11" fans to outperform stock LT1 fans by 13%).
Finally, cooling at idle can be improved through conversion to an electric waterpump. Because they use electricity, they spin at full rate even at idle. When you push water more quickly through the system (especially at idle), you'll get better heat-exchange off the water. Meziere is the brand I've seen used for the owners that have converted. There are a couple of vids on a Meziere installation on YouTube. Any high-flow waterpump should also help but electric is better for idle-heating issues.
General rule of thumb:
Overheating at speeds above 35 means you need more radiator
Overheating at idle (but not at speed) means you need more fan.
Always check for proper fan function before considering an aftermarket solution. Note: Main fans are programmed to turn-off above 35mph. They are programmed to turn on in the 220's OR when you turn-on your A/C. LTx/ZR1 owners may find their engines running cooler WITH the A/C on because the fans will run all the time.
As cooling because a larger point of consideration with my 383 build, I've looked at the issue of cooling (especially idle heat) ever since. My car DOES have a Champion dual-row radiator -- which cools just fine w/o the A/C....AND with the A/C as long as the car is moving.
My thread on BUDGET radiators can be found here. Please know this linked thread was -- in no way -- meant to include DeWitts (or Griffin or BeCool) radiators. It's common knowledge that DeWitts is USA made and better quality. The budget thread was intended to help guide those unable to consider more expensive options. Considering cheap (and how many) C4s are on the road, I expect budget considerations to increase over time. That said, I've reached the 5-yr mark on Champion ownership and don't have any complaints. However, it's a garage-parked car with 25k on the clock since installation. I did have to purchase another drain **** as the original mini-weld failed on the drain-**** T-handle.
Now...lets consider fans.
Like others who've complained about heat -- even in cars with non-modified engines -- the C4 has it's challenges due to it's bottom-feeder air inlet. People worry about higher temps all the time. First, we should say newer engines WERE DESIGNED to run hot for the purpose of improved emissions. Main and auxilary fans were programmed (by the factory) to come on at higher temps -- like the 220's/230's. If you're not seeing temps higher than 240ish, you likely don't have a mal-functioning cooling system.
The first things to do -- if you want to maintain optimal operation -- is perform regular flushes AND cleaning of the radiator area. In short, the goal is to remove debris in front of and around the radiator. Usually, this will require removal of the top radiator housing so you can access the space BETWEEN the radiator and the A/C condenser.
The condenser LOOKS like a radiator and sits in front of it. FWIW, it cools your A/C's freon in much the same way a radiator works. When doing this, the air temp across it's fins/coils heats up. This has the same effect as driving your car on a much hotter day. The good news is the air temps still stay well below the HOT coolant in the radiator. As such, the air is still cool enough -- in relation to the coolant temp -- to pull heat off the coolant. Still, it's close enough that debris can block enough air flow to compromise it's ability to perform it's function in the hotter climates.
Air must flow across the radiator for it to work. In cooler temps AND when the car is moving, air flows across your radiator through the entrance below the C4 bumper. It should also be said that the air dams aide in this operation by diverting some of the air UPWARD into that entrance. If you have problems with cooling at speed AND your dam is missing, consider replacing it first. This is also a cold air scoop (sold aftermarket) that has been shown to provide minor assistance in this function. It should not be considered necessary for proper air flow. Most people who tried it (or built a version of their own) are happy with the additional cooling "help".
All C4's came with a main radiator. These fan(s) sit behind your radiator and pull air through it (like a ceiling fan pulls air in your windows). Some cars were optioned with the RPO "B4P" auxiliary fan . It's a second fan that sits in front of the A/C condenser PUSHING air through it. The rear, main fan(s) are shrouded. A shroud is a "wall" that extends from your fan to the edge of the radiator. The function of a shroud is to prevent air from bypassing the fan. When the car is motionless (or moving slowly), air isn't flowing through your radiator. When the fan kicks on, the shroud enables the fan to pull air from a larger surface of the radiator. When fully shrouded, air should pass across the entire network of fins.
Some will notice the shroud doesn't extend to the bottom of the radiator. Part of the reason NOT to block "non-fanned" sections of the radiator is to improve flow when the car IS MOVING. Because our cars are "bottom-feeders", air is more likely to flow across the bottom, making it a good section to leave unblocked. (In looking through this forum, it would appear that only people who race have considered another configuration than a stock shroud.)
Let's get back to the fans....
In the earliest C4s, I believe the main fan is controlled by a cylinder-head-mounted cooling switch? It's a mechanic switch with an internal "button". When it gets hot enough, the button "pops", swaps direction, and completes an internal circuit. When a ground wire (from a fan) is attached to this type of switch, it's grounded when the engine gets "hot". (This is based on a M.A.Motorworks instruction sheet I have). So you know....Coolant switch temperatures/ratings can vary. In an attempt to document several of the options, I created this thread. Take a look at it -- if you are considering another fan switch.
For later L98s and all LTx cars, the main fans are controlled by your car's computer. As such, it is possible to change the turn-on temps by altering the appropriate parm(s) in the computer code. I lowered mine to trigger around 190. (The reason I say "around 190" is that coolant temps aren't consistent throughout your engine. For L98's they are hotter in the heads and the rear. LTx cars use reverse cooling. ZR1 cars aren't something I've looked at in this regard. I have to assume they have their own spots where the coolant is hotter than others. This point is of some consideration because the purchase of an alternate coolant switch may not have the results you expect. (This is covered a bit more in the link provided above.)
L98 main fans are 16" single fans. (Correct me if that doesn't apply to all models!) Starting in 1990, fans were converted to a dual setup. I'm going to guess these are considered 11" fans. I'm also going to guess the dual fans were used on both LTx and ZR1 models.
On of the things you'll notice if you look at aftermarket fan options is dual fans pull more air than single fans. That's true even if the single fan is larger. Most aftermarket fans claim anything from 1200-3600 rpms. People often tout the use of early Taurus/Mark VII fans for cooling. DeWitt's posted an interesting comparison of these older fans -- compared to SPAL 16" and dual 11" on their website here.
The biggest thing I get out of the link is to notice amperage and performance drop -- as static pressure increases. Static pressure is resistance that's created when sitting obstructions in front of your fan -- like radiators and condensers. When you look at DeWitt's graph...and any aftermarket fan that includes specifications, you'll find yourself wondering "How much static pressure is in MY motor?" That's a good question...and likely plays a role in any alternative fan selection. One site I found claims the average static pressure is between .4 and .7 mm H20. I am unable to verify this nor should it be more than a guide -- since your specific car may vary.
In addition to static pressure, notice fan amperage. Normally the amperage is higher when the fan is capable of pulling more air. Just like an engine, it takes energy to perform mechanical motion. The more work done, the more energy it takes. Also, like engines, there are various designs that can be somewhat more efficient, but I think it's still good practice to notice power requirements when selecting a fan. This will help determine wiring (gauge) requirements, fuse requirements AND whether it's likely to out-perform your current unit.
My own observation (and digging through this forum) has led me to believe there aren't many fans that are better-than-stock. Even if you compare stock and aftermarket CFM ratings, you probably aren't looking "further down the chart" where static pressure is .4 or greater.
When you consider the construction of fans, curved blades are quieter. But each blade may pull more air via it's "cupped" design. Fans with more blades and/or "cupped/curved" area will pull more air. In one study I read, it was suggested that straight blade fans pull air through more "directionally". By contrast, curved blade fans expel air outwardly/radially. This study was done on smaller fans but still seems relevant to larger ones. (This makes me wonder if better dispersion allows air to bend around the motor better and exit through side/hood vents? IDK...I'm just posing the question.)
I like the option of a curved/quieter fan but CFMs are normally the better goal. There are a couple of SINGLE fans that tout 3000-3600 cfms. I doubt this claim due to the amperage they draw. I suspect it's more likely they pull closer to 2k CFM. If you consider my guess true, that brings them more in line with SPAL fans -- which appear to be the most prominent in aftermarket appeal.
For L98's, DeWitt's repackages and sells (what I believe to be) the best straight-blade SPAL fan. It looks like they splice on a factory end and package (include) an adapter mounting shroud. This makes for an easy installation which warrants their somewhat higher price. They also (probably) still sell the fan adapter alone. (part# SP012) It's the silver mounting flange in this DeWitt's link. Basically, you bolt a SPAL fan to this flange...which is shaped/drilled to match your factory shroud. There are lots of ways to mount a fan, but this doesn't require fabrication or imagination.
Later C4s are equipped with dual fans. DeWitts has an option for that too....though I'm unaware of any upgrade in performance compared to your stock dual fans. BTW, this means upgrade "kits" shouldn't be considered as interchangeable between early/late cars due to the conversion from single to dual fans!
Earlier, I mentioned dual fans perform better than single fans. With an increase in power for the ZR1 (and LTx) cars, I think it's likely that the extra power (heat) resulted in the change to dual fans. This too, is something I can't prove. But, it makes sense on a bottom-feeder with increasing heat production.
For people considering an upgrade to the L98 fan, a dual fan might be the best option. Before considering that option, take notice to their depth as you MAY run into the need to address clearance issues with your power steering reservoir and/or your A/C dryer (the shiney silver thing in front of your A/C).
I am considering conversion options myself. In doing so, I believe the stock L98 fan MIGHT have decent static pressure "resistance". If so, it would explain the larger-than-aftermarket motor AND why so many are disappointed with aftermarket fan selection. Even if you pick a fan advertised higher than the 11 amp, 1700 cfm stock main fan, it might not perform better when loaded behind your radiator. That's because ratings are usually with no static pressure (in free air).
(Note: I haven't confirm the L98 stock amperage/CFM either. But the figures posted are what's commonly found in this forum. I've also seen 1400 cfm posted. Considering the amperage, 1400 might be more realistic. Again, the factory motor is substantial so it probably also has good performance under load (mounted) when compared to aftermarket units nearing 2k cfm.
Again, one key is to consider amperage. SPAL has one curved blade fan rated at 45 amps (30102803HO) and another curved blade unit rated at 22 amps (30202082). 2082 lists the same "1918 cfm" as the DeWitt's conversion. PDF documentation shows the curved fan slightly higher. That might make is a better option in terms of noise and flow. The 2803HO option only shows a bump to "1953 cfm". But, on both of these fans, you may find higher flow ratings. (Don't be fooled by m/hr versus CFM ratings.) Still the PDF documentation on the 2082 (and 2036 fan likely used by DeWitts) show higher flow ratings (2360 cfm and 2470 cfm respectively). The curved blade draws a bit more power, has more substantial blades, and might have better static pressure performance? The 30102803HO fan is SPALs best upgrade option -- despite it's 1953 cfm rating. If you compare the PDF ratings, the 2803 has DOUBLE the static pressure performance at 1 mm H20 compared to the (DeWitt's?) straight-blade unit. I haven't been able to find documention on the lower-priced, curved-blade 30102082 unit, but it's probably between the two. Amperage ratings range from 22 to 26 on these fans...so that extra 2-4 amps may just be worth it -- when the fans are under load behind your radiator.
It would probably be easier if I created a picture/comparison chart to understand the paragraph above. In lieu of that, I'll try this....
Stock L98 main fan
11 amps, 1400-1700cfm (750-800 with .7 static pressure performance?)
DeWitt's L98 upgrade (straight blades with factory plug and mount kit)
21.6 amps, 2360 cfm (1180 with .7 static pressure performance)
30102082 SPAL (curved blades)
22 amps, 2470 cfm (I estimate 1300 cfm under .7 static pressure load)
30102803HO SPAL (curved blades)
49 amps (w 100 amp turn-on spike), 3310cfm no load cfm performance (~2250 cfm .7 static pressure performance)
If anyone knows the LTx ratings and wants to compare them to SPAL/DeWitt's options, let me know and I will add it to this post.
I also like the Derale 17" option (part 16217). It's a 2-spd fan offering 2400/1800 cfms....rated at 23.5/17.4 amps. I believe this fan could be mounted on the front side of the factory fan cage (after removing the L98 fan) and mounting it with spacers to the factory location. (It would probably mount best, if you had a table saw to remove the small lip on the front of the factory fan cage.)
Flex-a-lite is another manufacturer that sells some high-power options.
Dual 11" fans add quite a bit more air flow than the single options listed above. (Again, these are used on later LTx/ZR1 models. So, it's a better setup.) On SPAL's website, 11" fans flow as much as 1300cfm under load(2780cfm no load). Maybe 65-70% more than an L98 single fan?
Running amps for a dual setup total ~30A, so they are more efficient too. (You can double the CFM with less than 50% more amps.) In this thread, you'll see long-time member jfb measured the amperage of the factory dual 11" fans @ 14amps apiece.
FWIW, people HAVE put dual 11" fans in C4s that weren't originally equipped with them as shown here. C3's often used a dual setup out of the Ford Focus. It appears to be a lower-power version of the LT1/ZR1 setup -- though still higher in flow than the single 16" setup. They look to rank in the less-expensive dual 11" setups which flow 2750-2800 (zero resistance) TOTAL. (This is still higher than stock single fans AND most aftermarket single 16" fans.) It would seem likely that the DeWitt's dual 11" setup would be fairly equivalent to the late factory setup. If this is designed to go in early cars, it could be a good option too. (FYI: A tester recently showed the DeWitt's dual 11" fans to outperform stock LT1 fans by 13%).
Finally, cooling at idle can be improved through conversion to an electric waterpump. Because they use electricity, they spin at full rate even at idle. When you push water more quickly through the system (especially at idle), you'll get better heat-exchange off the water. Meziere is the brand I've seen used for the owners that have converted. There are a couple of vids on a Meziere installation on YouTube. Any high-flow waterpump should also help but electric is better for idle-heating issues.
General rule of thumb:
Overheating at speeds above 35 means you need more radiator
Overheating at idle (but not at speed) means you need more fan.
Always check for proper fan function before considering an aftermarket solution. Note: Main fans are programmed to turn-off above 35mph. They are programmed to turn on in the 220's OR when you turn-on your A/C. LTx/ZR1 owners may find their engines running cooler WITH the A/C on because the fans will run all the time.
Last edited by GREGGPENN; 07-30-2022 at 09:47 PM.
09-06-2016, 05:50 PM
#2
Race Director
Thread Starter
Oh yeah...dual 11" fans add quite a bit more air flow than the single options listed above. On SPAL's website, their flow measures as much as 2700cfm per fan. You can see that would be a substantial increase. Running amps total around 30A, so they are more efficient too. (You potentially can double the CFM with another few amps.)
I think dual 12" fans would be impossible to install behind our stock radiator housing. They total a greater width.
I am likely to select the SPAL 30102308HO option. I am thinking it can easily be mounted on the inside lip of the factory fan cage. But, that will require the cross-bars to be cut out...and the SPAL mounted tabs to be removed (both done with a dremel). I would fill any (small) gap between the two with rubber gasket or black silicone. I am planning on using rivets to connect their outer (circumference) housings. Regardless of the fan I choose, I will post (with pictures) on this forum.
I should also add that I've discussed wiring considerations here.
In the linked thread above, I suggested parallel connection of the factory main and aux (B4P) circuits. Using dual relays would raise the amperage limits from 25-30 to 40+ amps. The actual rating of the factory circuit is somewhat variablel based on age/parts. From what I know, the factory wiring is 12 guage. And, the factory relays are rated at 30 amps. Both may lower with age.
Finally, the practice of parallel connection of relays to trigger a single circuit isn't favored well. That's because relays can trigger milliseconds apart -- which COULD lead to one relay seeing higher amperage/heat levels. If true, it could fail sooner and leave the remaining relay/circuit holding the entire load. This would likely blow that circuit's fusible links.
(A fusible link is a type of fuse that is a chunk of short wire. When it overloads, it melts....much the same way a fuse melts internally. They are located in your engine compartment. On an L98, they are behind the battery.)
Oh yeah....thermostats! Don't consider your thermostat anywhere in a heating issue UNLESS it's stuck closed!!!!
I think dual 12" fans would be impossible to install behind our stock radiator housing. They total a greater width.
I am likely to select the SPAL 30102308HO option. I am thinking it can easily be mounted on the inside lip of the factory fan cage. But, that will require the cross-bars to be cut out...and the SPAL mounted tabs to be removed (both done with a dremel). I would fill any (small) gap between the two with rubber gasket or black silicone. I am planning on using rivets to connect their outer (circumference) housings. Regardless of the fan I choose, I will post (with pictures) on this forum.
I should also add that I've discussed wiring considerations here.
In the linked thread above, I suggested parallel connection of the factory main and aux (B4P) circuits. Using dual relays would raise the amperage limits from 25-30 to 40+ amps. The actual rating of the factory circuit is somewhat variablel based on age/parts. From what I know, the factory wiring is 12 guage. And, the factory relays are rated at 30 amps. Both may lower with age.
Finally, the practice of parallel connection of relays to trigger a single circuit isn't favored well. That's because relays can trigger milliseconds apart -- which COULD lead to one relay seeing higher amperage/heat levels. If true, it could fail sooner and leave the remaining relay/circuit holding the entire load. This would likely blow that circuit's fusible links.
(A fusible link is a type of fuse that is a chunk of short wire. When it overloads, it melts....much the same way a fuse melts internally. They are located in your engine compartment. On an L98, they are behind the battery.)
Oh yeah....thermostats! Don't consider your thermostat anywhere in a heating issue UNLESS it's stuck closed!!!!
Last edited by GREGGPENN; 09-07-2016 at 01:38 PM.
09-06-2016, 05:59 PM
#3
Race Director
Thread Starter
I should add that the biggest reason I'm considering an option (after installing a bigger radiator and insuring my system is clean/operational), that my 383 stroker creates higher heat than factory for potential, heat-creating reasons:
Thinner cylinder walls (due to .030 overbore)
Heavier springs
Longer stroke/higher piston speed
Higher idle
Higher compression
aggressive idle ignition timing (for engine configuration)???
You'll find MOST mechanics/builders will advise trying to tweak/diagnose your factory equipment first. That's because (even with our bottom-feeders), it was designed to cool your car properly....or, maybe, just barely!
Thinner cylinder walls (due to .030 overbore)
Heavier springs
Longer stroke/higher piston speed
Higher idle
Higher compression
aggressive idle ignition timing (for engine configuration)???
You'll find MOST mechanics/builders will advise trying to tweak/diagnose your factory equipment first. That's because (even with our bottom-feeders), it was designed to cool your car properly....or, maybe, just barely!
Last edited by GREGGPENN; 09-06-2016 at 06:13 PM.
09-06-2016, 11:51 PM
#4
Team Owner
Member Since: Oct 2004
Location: altered state
Posts: 81,242
Received 3,043 Likes
on
2,602 Posts
St. Jude Donor '05
Havent had time to read teh whole thing but look into the new brushless fans they are the ticket C7 uses them. Aftermarket just bringing them out
pretty nice stuff.
pretty nice stuff.
09-07-2016, 08:27 AM
#5
Safety Car
Just a comment on my factory system, as far as I was concerned it was not even adequate for stock. My 1986 with the dual fan option on a 90 degree day with the air on sitting in park would overheat in my driveway. (And yes the system was clean)
09-08-2016, 12:31 PM
#6
Team Owner
Member Since: Oct 2004
Location: altered state
Posts: 81,242
Received 3,043 Likes
on
2,602 Posts
St. Jude Donor '05
my 89 with a perectly clean radiator would do the same never waited to see if it would boil over but moving or at idle to have it constantly creep up imo is a joke for a cooling system. The whole "its ok to run at 230 or 240" Ill never buy. Thats pretty friggin warm no thanks
09-08-2016, 01:31 PM
#7
Race Director
Thread Starter
my 89 with a perectly clean radiator would do the same never waited to see if it would boil over but moving or at idle to have it constantly creep up imo is a joke for a cooling system. The whole "its ok to run at 230 or 240" Ill never buy. Thats pretty friggin warm no thanks
Some people have said newer engines are "designed" to run at higher temps. From what I see, that's true ONLY from the stand point thermostat temps have risen from 160 (pre-catalytic converters) to the 180/195 range.
While the running temp is higher in newer cars -- for the purpose of better converter function, nothing indicates temps in the 200's are desirable. In fact, the EGR system was developed and put into place to eliminate undesireable NOx emissions that form in the 200's!
In recent years, we also saw the results of a study that showed COOLER temps resulted in more horsepower. (Hmmmm...where was THAT posted?!?!) BTW...This has been highly debated in this forum -- because it's also known that stored heat is power!
In general, early/late C4's might have similar AVERAGE engine temps. Obviously water goes through LTx heads first -- which would help LOWER cooling temps in LTx cylinder heads. To me, that confirms lowering temps are better. And, those engines use a 180-stat with better fans. Those cars RARELY see 200-deg temps.
I think it's fair to say temps SHOULD be controlled (BELOW the 200's) for maximum performance. Heat also contributes to pre-ignition. You won't know when it starts because our engines have knock-sensors that pull timing when they sense this is happening. And, less timing means less power/efficiency.
09-08-2016, 03:28 PM
#8
Team Owner
Pro Mechanic
I laugh when people try to claim that there is a "perfect, ideal, or correct" operating temp. How can that be? It can't.
It depends on the circumstances, the criteria for the engine/user, application and on and on. Lets look at a couple examples;
The LT1 has a designed operating range that spans a whopping 50*F! It has a 180 stat (and mine will drive it's temp down into the 170's at times before the stat totally closes and it heats up again)...but the fans don't turn on until 230*. So what is the "ideal/correct" temp for that engine? Somewhere between 180 and 230...and that is quite a range.
People say that cool operating temps increase bore wear. Maybe...but if it does, it is at meaningless rate, IMO. I've run cars w/160 stats. No issues, but "big deal" right? Sample of one? Boats. They all have stats to run ~160*F. not 180, not 195, not 230. Mine runs 150-160 all the time. It may heat soak up to ~180 after shut down, but plummets to 145-150 immediately on start up. It has 925 hours on it and performs as new. Boats will run right on past 2000 hours when maintained, at those "cold" temps and we all know; boats are always "going up hill" (working hard), unlike most cars.
There isn't a "correct" operating temp. The correct temp is the one that meets your and your cars criteria.
It depends on the circumstances, the criteria for the engine/user, application and on and on. Lets look at a couple examples;
The LT1 has a designed operating range that spans a whopping 50*F! It has a 180 stat (and mine will drive it's temp down into the 170's at times before the stat totally closes and it heats up again)...but the fans don't turn on until 230*. So what is the "ideal/correct" temp for that engine? Somewhere between 180 and 230...and that is quite a range.
People say that cool operating temps increase bore wear. Maybe...but if it does, it is at meaningless rate, IMO. I've run cars w/160 stats. No issues, but "big deal" right? Sample of one? Boats. They all have stats to run ~160*F. not 180, not 195, not 230. Mine runs 150-160 all the time. It may heat soak up to ~180 after shut down, but plummets to 145-150 immediately on start up. It has 925 hours on it and performs as new. Boats will run right on past 2000 hours when maintained, at those "cold" temps and we all know; boats are always "going up hill" (working hard), unlike most cars.
There isn't a "correct" operating temp. The correct temp is the one that meets your and your cars criteria.
09-08-2016, 04:29 PM
#9
Race Director
Thread Starter
You might remember it -- since you've been around the forum awhile?
Summer heat and fuel quality have been a couple of factors I've seen that have caused knock (knock counts) in my OEM engine before conversion. So, I still think the lower end of DESIGNED operating range is more "ideal".
Please don't infer I'm saying 230 is an "incorrect" temperature. As you point out, the engineers/designers allow the engine to get that high.
Last edited by GREGGPENN; 09-08-2016 at 04:33 PM.
09-08-2016, 04:40 PM
#10
Team Owner
Pro Mechanic
I hear you. I agree with you that there is potential for more power at lower head temps.
I don't recall the thread w/the temp/hp study, but in one of my cars, I was able to document faster ET's/traps at the track running 160 (and more timing) vs. 180 (and less timing due to detonation).
There have also been threads that referenced some study done by Continental engines? years ago that showed higher bore wear at lower temps. I've never been able to find documentation of that test...and even if I did, I don't feel that those tests are relevant to our engines. I've seen enough of my own results to conclude that cooler temps are in no way, detrimental. IMO, Any wear differences due to cooler operating temps are inconsequential.
I don't recall the thread w/the temp/hp study, but in one of my cars, I was able to document faster ET's/traps at the track running 160 (and more timing) vs. 180 (and less timing due to detonation).
There have also been threads that referenced some study done by Continental engines? years ago that showed higher bore wear at lower temps. I've never been able to find documentation of that test...and even if I did, I don't feel that those tests are relevant to our engines. I've seen enough of my own results to conclude that cooler temps are in no way, detrimental. IMO, Any wear differences due to cooler operating temps are inconsequential.
09-08-2016, 04:41 PM
#11
Drifting
Member Since: Oct 2006
Location: Stafford Connecticut
Posts: 1,328
Likes: 0
Received 14 Likes
on
13 Posts
Actually the reverse cooling for the LTX heads did not work out as GM intended.They found out after the fact that it caused air pockets to form in the heads resulting in uneven cooling of the heads and hot spots .As for the LTX intake it suffered from the same fuel reversion as the Mini Ram does.So they had to program the rear cylinders to run leaner and the front richer.
09-08-2016, 05:00 PM
#12
Team Owner
Pro Mechanic
Where did you learn that? The system did do what GM wanted; it contributed to meeting their performance goals of the time.
09-08-2016, 05:30 PM
#13
Drifting
Member Since: Oct 2006
Location: Stafford Connecticut
Posts: 1,328
Likes: 0
Received 14 Likes
on
13 Posts
I read Tom.Ju st like they could have stopped a lot of optispark problems by drilling a hole in the bottom to let moisture out.Car manufacturers make lots of mistakes in design all the time.It may have met there performance goals The reverse cooling still had it's problems.
09-08-2016, 05:39 PM
#14
Safety Car
Actually the reverse cooling for the LTX heads did not work out as GM intended.They found out after the fact that it caused air pockets to form in the heads resulting in uneven cooling of the heads and hot spots .As for the LTX intake it suffered from the same fuel reversion as the Mini Ram does.So they had to program the rear cylinders to run leaner and the front richer.
The point of reverse cooling was to keep the heads cool, and the fact that steam pockets were formed that caused hot spots in the heads, supports the argument that keeping the engine cool is a benefit.
09-08-2016, 05:52 PM
#15
Drifting
Member Since: Oct 2006
Location: Stafford Connecticut
Posts: 1,328
Likes: 0
Received 14 Likes
on
13 Posts
You are correct that is what a local speed shop told me last week.I thought I posted that the factory did have to compensate for fueling in my post.Keeping the heads cool does have a benefit.Just like people think that having EGR is bad when in fact it has it's benefits in fuel mileage and stopping pre detonation.
Last edited by steven mack; 09-08-2016 at 05:54 PM. Reason: add ifo
09-08-2016, 05:59 PM
#16
Team Owner
Pro Mechanic
Link? I'd be curious to read more about that too...if possible. I ask b/c I've never heard of this.
Every mechanical thing "has it's problems". 
09-08-2016, 07:01 PM
#17
Team Owner
Pro Mechanic
I did some searching, and there is definitely plenty of documentation re: steam collecting in the heads...in Gen I SBC modified to reverse flow the coolant. In THIS ARTICLE about that very modification (making a GEN I SBC reverse flow cooled), the author details GM's solution for that problem that was engineered into the Gen II engine;
"Chevrolet engineered a solution to the steam-created hot spot problem by installing vents into the cylinder heads where the steam would normally collect. The trapped steam escapes through these vents into a tube that goes into the coolant overflow reservoir. The vent opening is small enough to limit liquid flow, but still allow the steam to easily escape."
So, I'm not sure that GM found out after the fact that it caused air pockets to form in the heads.., rather it seems they were well aware of the pitfalls of that philosophy, and engineered in a solution. As I said, I'd be curious to read more about it if there is something more specific and in-depth to that system.
"Chevrolet engineered a solution to the steam-created hot spot problem by installing vents into the cylinder heads where the steam would normally collect. The trapped steam escapes through these vents into a tube that goes into the coolant overflow reservoir. The vent opening is small enough to limit liquid flow, but still allow the steam to easily escape."
So, I'm not sure that GM found out after the fact that it caused air pockets to form in the heads.., rather it seems they were well aware of the pitfalls of that philosophy, and engineered in a solution. As I said, I'd be curious to read more about it if there is something more specific and in-depth to that system.
09-08-2016, 07:25 PM
#18
Team Owner
Member Since: Oct 2004
Location: altered state
Posts: 81,242
Received 3,043 Likes
on
2,602 Posts
St. Jude Donor '05
interesting on the tuning by cyl
Have flowed a bunch of those LT1 intakes and although they will all be slightly different number 8 is horrible..like super bad. Maybe the motor cant use whats there so they didnt have to tune to its handicap?
perfect I suppose is what GM specifies moreso for emissions than anything else Id bet.
x2 on boats and hero dyno engine runs they are done at lower than normal temps for best power.
Everyones gotta do whats best for them, still run 160 stats good fans and big radiators. Maybe too many hoopties over the yrs had to gauge watch brought it on.
Have flowed a bunch of those LT1 intakes and although they will all be slightly different number 8 is horrible..like super bad. Maybe the motor cant use whats there so they didnt have to tune to its handicap?
perfect I suppose is what GM specifies moreso for emissions than anything else Id bet.
x2 on boats and hero dyno engine runs they are done at lower than normal temps for best power.
Everyones gotta do whats best for them, still run 160 stats good fans and big radiators. Maybe too many hoopties over the yrs had to gauge watch brought it on.
Last edited by cv67; 09-09-2016 at 09:03 AM.
09-08-2016, 08:07 PM
#19
Drifting
Member Since: Oct 2006
Location: Stafford Connecticut
Posts: 1,328
Likes: 0
Received 14 Likes
on
13 Posts
Tom if I remember correctly it was after the fact.Unfortunately the early LTX buyers had to pay for the over sight in engineering.Just like L98 owners had to learn about thin head castings and blown head gaskets.The LTX is long gone and the article I sight was written a long time ago.The good news is the LS motors are a great replacement.But they also had problems when they first came out.Buyers of the first ones were very upset with going through two quarts of oil in 500 miles.GM tried to follow the racing folks and use low tension oil rings.They had to fix the problem on all the new C5' s by putting stock tension oil rings in the customers Vettes.They found out the problem was caused by ring Flutter which caused the rings to loose contact with the cylinder walls.
Last edited by steven mack; 09-08-2016 at 08:26 PM. Reason: add info
The following users liked this post:
ijakie1 (08-11-2023)
09-08-2016, 08:23 PM
#20
Race Director
Thread Starter
I just read the article. Interesting. What's going on in SBC cylinder heads may explain why there was a change in dash (temp) readouts before/after a swap from smaller-ported to larger-ported gaskets...(at the rear). I'm talking about the discussion in this thread.
I especially like what a Sales Manager posted at the end of the article...to correct the author about the LT1 engine being Gen II and...why he thinks reverse-flow was abandoned. If true, it's a better explanation of reverse-flow being discontinued versus it being "a failure"!!!
Great link, Tom!
Maybe I should add another one that reminds us you can typically use more advance at 185-deg versus 205-deg. (Yes, the site is for Mustangs, but it still applies.)
I would think both links (articles) fail to mention the use of OTHER means to lower coolant temps -- and gain performance. I specifically DON'T like that reisch performance didn't mention that you'd NEED to hold temps down to their lower stats -- which would require other upgrades including: fans/radiators/waterpumps.
I'm surprised, this overall "cooling system approach" to lowering temps wasn't included at the end of the "Reverse Cooling" article. I guess they considered it "off-topic"?
I especially like what a Sales Manager posted at the end of the article...to correct the author about the LT1 engine being Gen II and...why he thinks reverse-flow was abandoned. If true, it's a better explanation of reverse-flow being discontinued versus it being "a failure"!!!
Great link, Tom!
Maybe I should add another one that reminds us you can typically use more advance at 185-deg versus 205-deg. (Yes, the site is for Mustangs, but it still applies.)
I would think both links (articles) fail to mention the use of OTHER means to lower coolant temps -- and gain performance. I specifically DON'T like that reisch performance didn't mention that you'd NEED to hold temps down to their lower stats -- which would require other upgrades including: fans/radiators/waterpumps.
I'm surprised, this overall "cooling system approach" to lowering temps wasn't included at the end of the "Reverse Cooling" article. I guess they considered it "off-topic"?