When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Sorry to burst your bubbles but I actually did some testing on this few weeks ago. -96 with cut lid and k&n filter. No additional ducts or holes.
90F day outside, I took a digital cooking thermometer and placed it in the intake ducting between maf and tb. with fully warmed engine, at idle the intake air temp was ~30 degrees hotter than ambient air.
As soon as I went over 20mph, intake air temp was only few degrees warmer than ambient air. No matter if cruising or flooring it, air temp didn't go up
that's cold enough for me, no reason to cut holes for one or two degrees.
Hi Tapio,
Thank you for your efforts. As to the veracity of your readings, I respectfully ask you to consider two points. The first is a question: Where do you think your car is getting cooled air from while underway at 20MPH? I think you'll find the major quantity of available air in the engine compartment comes through the radiator which is probably 100 degrees above ambient.
The second point comes from something called the Bernoulli effect. One aspect of the Bernoulli effect is that an increase in velocity will cause a decrease in pressure. This decrease in pressure will, most likely, cause the metal probe of your cooking thermometer to experience cooling through evaporation as the increased air flow passes over it.
In my experience, I see no way for the engine of a C4 to get cooled without providing additional ducting.
I like theory and since so do you, let's have some more. I personally don't believe that the bernoulli effect would be noticeable in this case.
with my 383 spinning 6500 with 0.8 VE, it takes in max of 600cfm.
Even if I would place the thermometer in the narrowest point of the duct (3" right after the maf-sensor), air velocity would be around 35mph. Now if you stick your thermometer with 1/8" sensor rod out of the window while driving at 35mph, how many degrees under the ambient it's going to show? I'm saying none.
What would be your preferred way of measuring so I can provide you with some data?
This is probably a stupid question, but does the temperature of the air coming into the engine really impact performance much?
Yes. The cooler the air, the denser the air/fuel charge, increasing Volumetric Efficiency (more molecules of air/fuel filling the volume of the cylinder). That's why you'll see drag racers packing their manifold with ice between runs.
I like theory and since so do you, let's have some more. I personally don't believe that the bernoulli effect would be noticeable in this case.
with my 383 spinning 6500 with 0.8 VE, it takes in max of 600cfm.
Even if I would place the thermometer in the narrowest point of the duct (3" right after the maf-sensor), air velocity would be around 35mph. Now if you stick your thermometer with 1/8" sensor rod out of the window while driving at 35mph, how many degrees under the ambient it's going to show? I'm saying none.
What would be your preferred way of measuring so I can provide you with some data?
HA!
Tapio, I don't want to have to think that hard.
Let me just ask you a simple question: Given that the air filter is forward of the shroud, an area with no ambient air flow, and...
the small open space between the front of the engine and rear of the front air dam would be a low pressure area (Bernoulli, again!), sucking the warm air coming through the radiator out the bottom of the car and...
the area on either side of the engine is subject to the heat from the exhaust manifolds...
If not from the pressure drop and evaporative cooling... Where do you suppose your TB is getting ambient temperature air from?
This is probably a stupid question, but does the temperature of the air coming into the engine really impact performance much?
Reality, not as much as people think. I believe the rule of thumb is 1% power increase for every 10deg reduction. As it has been stated already, when the car is moving, the intake temp is about the same as ambient.
Hello again. Did some testing again, this time on standing mile.
Two passes with diy ram air = cut license plate cover with dut to direct air to filter and two passes with stock license plate cover.
Same track, same day, same weather conditions.
With "cold air" cover ~161mph
with stock cover ~165mph.
You can still say what you like but at least I'm still not convinced about that ram air thing. It doesn't give you more air, it doesn't give you more power, it doesn't give you more speed.
Hello again. Did some testing again, this time on standing mile.
Two passes with diy ram air = cut license plate cover with dut to direct air to filter and two passes with stock license plate cover.
Same track, same day, same weather conditions.
With "cold air" cover ~161mph
with stock cover ~165mph.
You can still say what you like but at least I'm still not convinced about that ram air thing. It doesn't give you more air, it doesn't give you more power, it doesn't give you more speed.
Hi Tapio,
Thank you for sharing your experience! Obviously, most of us don't have that type of facility at our disposal so your experience is that much more valuable to us.
To more fully understand your results (which, you must admit, seem contrary to popular belief - mine included) could you please answer a couple of questions for us?
1. Which way was the first run, with cold air or without?
2. How much time between runs and, did outside air temp change significantly?
3. Did you time your acceleration to any given speed?
4. Do you have any pics of how you cleared the air path between the grill and the engine compartment?
5. Do you have any pics of how your cold air grill actually ducts air to your air filter?
What I did, along with pics (for general information) is found here:
What can't be seen in the photos are the "gates" I had to fabricate to keep the airflow from dispersing before it got to my engine compartment entry holes. I am assuming from your text that you actually formed or installed some sort of duct to prevent outside air losses.
Also, what's not seen in my pics (I hadn't done it yet) is I drilled out the six rivets that hold the air filter air horn in place, (facing upward toward the engine compartment). I then added a 3/4" spacer to raise the air horn, turned it around facing the incoming cool air and re-attached it to the air filter.
My SOTP Dyno tells me it makes a difference in hard accelleration, most obviously felt at the shift points. Of course, SOTP Dynos are highly unreliable and directly connected to the extent of one's labor and the price of the goods!
Seriously, I would love more information on your install and your runs. It just boggles my mind that your aerodynamic losses exceeded your cold air power increase.
i will put my theory out for debate,
i think that the air speed needs to be slow enough for it to be sucked into the air filter, if the air speed is too fast it makes it harder for the intake to draw it in,
two things make me think this,
I was watching a show on the development of the HD vrod, which is the first water cooled Harley, they had trouble getting the radiator to cool efficiently (keeping in mind the radiator is out the front in the open). the cure was to make a shroud in front of the radiator with angled louvres, this slowed the air speed down enough so that it could do its job, now I know this is a air cooling process, but,
I used to have a zzr1100 Kawasaki, and they were the first bikes fitted with a "pressurized air box", if you looked inside them they had compartments before entering the air filter, those compartments trapped and held the air just in front of the filter. this system was developed by an aircraft company that Kawasaki owned.
at the time the zzr was developed Japan had a 150 hp limit for street bikes, the zzr was rated at 152 hp, but the performance of the bike (top speed / 1/4 mile etc) was in excess to the 152 hp rating.
Now when we look at Tapio's result with the stock setup being 4 mph faster than a "ram air" it may be because the speed of the air around the filter is important, perhaps the ram air is blasting the air past the air filter too fast ?
Does the radiator and intake experience tell us that air needs to be moving slow enough to do its job , particularly on a naturally aspirated engine using an air filter ?
Did the GM engineers get the design of the boxed surround of the air filter on the Corvette right ?
Interesting. Relative to your comments about the design of the C4 air filter design... GM engineers knew how to make power. What they were struggling with was lowering emissions at the same time. Keeping engine temperatures up reduced emissions, as did reducing intake speed (reduced unburned charge going out the exhaust valves). They traded power for lower emission requirements.
I didn't have a Kawasaki ZZ1100, but I did have a Honda CBR1100XX. One trick we used to make a little more power was to block off a hot air inlet valve in the air box.
In defense of my belief that cool air, ram air, clean air, etc. increases engine power, I offer the following:
This thread definitely interests me. A few things:
*That cars HAVE used "ram air" isn't proof that it works. Many of those older ram air systems were flawed, and more for looks than anything. Ones that worked ("made" power) probably did so more b/c of cooler air intake than a round filter sitting on a carb.
*I believe that turbulence at an inlet could be more harmful than the benefit provided by "cold air". My feeling is that is what is happening with "Taplo" when using ram air. There is no other way I can think of, to explain a consistent loss of speed/power.
*I'd be curios to see the results (from Tablo) of flipping the stock air filter over and cutting the radiator shroud so it gets air from in front of the AC condenser.
Interesting. Relative to your comments about the design of the C4 air filter design... GM engineers knew how to make power. What they were struggling with was lowering emissions at the same time. Keeping engine temperatures up reduced emissions, as did reducing intake speed (reduced unburned charge going out the exhaust valves). They traded power for lower emission requirements.
I didn't have a Kawasaki ZZ1100, but I did have a Honda CBR1100XX. One trick we used to make a little more power was to block off a hot air inlet valve in the air box.
In defense of my belief that cool air, ram air, clean air, etc. increases engine power, I offer the following:
Oh and...
thanks for posting the photo's, I think they actually highlight the difference in the c4 intake , a ram air / cold air effect can work if it put directly into the intake, such as in the photos above.
The c4 intake is different in that it has an air filter in "a space" the incoming air is not trapped, it can flow past the filter. This also means that if the air is flowing faster, it is much more likely to flow past the filter.
If you look at modern efi air intakes they usually have a intake near the front (of the car) that leads into a box containing the air filter, this means the air is trapped, the unit is "sealed"
I would suggest that if you built an air intake from the front of a c4, but it lead into a sealed or boxed area around the filter you would be much more likely to gain some benefit. This is how the japanese performance bikes are set up using "pressurized" air box's.
thanks for posting the photo's, I think they actually highlight the difference in the c4 intake , a ram air / cold air effect can work if it put directly into the intake, such as in the photos above.
The c4 intake is different in that it has an air filter in "a space" the incoming air is not trapped, it can flow past the filter. This also means that if the air is flowing faster, it is much more likely to flow past the filter.
If you look at modern efi air intakes they usually have a intake near the front (of the car) that leads into a box containing the air filter, this means the air is trapped, the unit is "sealed"
I would suggest that if you built an air intake from the front of a c4, but it lead into a sealed or boxed area around the filter you would be much more likely to gain some benefit. This is how the japanese performance bikes are set up using "pressurized" air box's.
What you're suggesting becomes a "Ram Air" box at higher speeds. I had considered that but decided against it because I didn't want to have to clean or replace my air filter on a regular basis. I was just looking to give the engine the benefit of cooler air entering the intake, as you suggest, above.
Before analyzing Tapio's videos, I'd like to see some answers to the questions I posted, above. Turbulence could, of course, cause a drop in power but so, too, could a bunch of other variables at the speed he was going. Which was his "colder" run in terms of engine heat, ambient heat, etc.? What was the wind doing during his runs and, although a long shot, could increased drag from removal of the the somewhat streamlined license plate filler work against him?
It would be great if someone with the old AO Engineering Forced Air system would chime in. They could certainly speak to your suggestion, above.
I think that air, water and electricity are all like teenagers, they are lazy and will take the path of least resistance !
if air is running inside intake tubing and then comes up against the filter in a sealed unit, then it has now where else to go, except thru the filter,
if air is rushing past a air filter that is in an open space (and that filter is further contained in a plastic/metal box) then the air is not likely to slow down, and do a 90 degree turn so that it can be sucked into that filter, the air molecules will be going "smile and wave boys !" as they rush past that air filter.
There is a thread on thirdgen talking about air intakes (but more about the tubing than the filter) but there is an interesting post by cal30_sniper, he seems to know a thing or two about the movement of air, he talks about velocity of air and major and minor head loss (loss of efficiency), lower velocity results in less head loss, and air movement thru the air intake should be slower, as opposed to the intake port where velocity is important.
anyway its worth a read, the more technically minded can probably decipher it better than I can, http://www.thirdgen.org/forums/alter...-intake-3.html
I think that air, water and electricity are all like teenagers, they are lazy and will take the path of least resistance !
if air is running inside intake tubing and then comes up against the filter in a sealed unit, then it has now where else to go, except thru the filter,
if air is rushing past a air filter that is in an open space (and that filter is further contained in a plastic/metal box) then the air is not likely to slow down, and do a 90 degree turn so that it can be sucked into that filter, the air molecules will be going "smile and wave boys !" as they rush past that air filter.
There is a thread on thirdgen talking about air intakes (but more about the tubing than the filter) but there is an interesting post by cal30_sniper, he seems to know a thing or two about the movement of air, he talks about velocity of air and major and minor head loss (loss of efficiency), lower velocity results in less head loss, and air movement thru the air intake should be slower, as opposed to the intake port where velocity is important.
anyway its worth a read, the more technically minded can probably decipher it better than I can, http://www.thirdgen.org/forums/alter...-intake-3.html
Hi Blackozvet,
The reference you mention and the author of Post #117 at that site, was obviously trained in fluid dynamics. As interesting as his post is, I believe it deals almost exclusively with airflow in a pipe that has to go through a 3" restriction such as a MAF presents. His point is that "Head Losses" are significantly greater in a 3" pipe than in a 4" pipe that has to neck down for a small run through the MAF and then opens up again.
However, I must take your observations to heart. If I'm understanding your "teenagers" analogy correctly, undirected air flow, whether cold or hot, causes flow problems that can result in a loss of power. That being said, at speed, our C4's have air rushing up through the shroud, past the condenser and radiator, through the fans and then out the bottom of the car due to the lower pressure of the air running past, below the engine (the Bernoulli effect).
With the air filter's inlet in its original orientation facing up and back, I should think it's fighting for air against a flow trying to exit the engine compartment below the engine. However, that constant flow may help keep what air it does capture less turbulent. Versus my poorly engineered (though, very attractive) attempt at cooling the incoming charge.
Before analyzing Tapio's videos, I'd like to see some answers to the questions I posted, above. Turbulence could, of course, cause a drop in power but so, too, could a bunch of other variables at the speed he was going. Which was his "colder" run in terms of engine heat, ambient heat, etc.? What was the wind doing during his runs and, although a long shot, could increased drag from removal of the the somewhat streamlined license plate filler work against him?
Sorry, I was in a bit of hurry yesterday, just posted the videos and went to sleep.
Originally Posted by DrDyno
Hi Tapio,
1. Which way was the first run, with cold air or without?
2. How much time between runs and, did outside air temp change significantly?
3. Did you time your acceleration to any given speed?
4. Do you have any pics of how you cleared the air path between the grill and the engine compartment?
5. Do you have any pics of how your cold air grill actually ducts air to your air filter?
1: first two runs were with cold air, last two were with stock cover
2: there was aprox. 1 hour between the runs and outside air temp didn't change during that time. If I remember correctly it was arounf 60F, very little side wind during the day.
3:No I didn't time, I was going to time my runs using sports tracker but somehow I forgot it.
4/5 I dont have any pics right now, car is packed away for the winter, I can take pics within few weeks when I go see her.
But it's basicly 4"x3" fiberglass duct that not only takes the air in, but directs it towards the filter. I used a rubber seal on the hood to seal out the filter. I didn't want any air packing into engine compartment and making me slower.
My .2 cents are that turbulance with the cold air cover is making it less aerodynamic and that way slower. I actually had laptop hooked in for the cold air passes, just wanted to see if there's any positive pressure in the intake manifold, there wasn't. I try to see if I can still recover those log files
The reference you mention and the author of Post #117 at that site, was obviously trained in fluid dynamics. As interesting as his post is, I believe it deals almost exclusively with airflow in a pipe that has to go through a 3" restriction such as a MAF presents. His point is that "Head Losses" are significantly greater in a 3" pipe than in a 4" pipe that has to neck down for a small run through the MAF and then opens up again.
However, I must take your observations to heart. If I'm understanding your "teenagers" analogy correctly, undirected air flow, whether cold or hot, causes flow problems that can result in a loss of power. That being said, at speed, our C4's have air rushing up through the shroud, past the condenser and radiator, through the fans and then out the bottom of the car due to the lower pressure of the air running past, below the engine (the Bernoulli effect).
With the air filter's inlet in its original orientation facing up and back, I should think it's fighting for air against a flow trying to exit the engine compartment below the engine. However, that constant flow may help keep what air it does capture less turbulent. Versus my poorly engineered (though, very attractive) attempt at cooling the incoming charge.
Hi DrDyno,
even tho he was talking about air movement inside the tube, the bit about flow being greater with less velocity was interesting,
BTW i actually like the setup you have made for your car
I think what we are talking about here is strictly performance related, trying to squeeze that last bit out, and the big question is are the 'cold air' systems that we make actually worth anything.
what we need is someone to make up an enclosed unit around the filter but not being directly fed from airflow from the front of the car, and one where it is, and see what the result is, and that result would have to come from some sort of timed event (eg racing)
I havent seen a pic of Tapio's inlets , but if his 2 setups match the above , then the question has probably been answered.
Maybe the best c4 setup would be a sealed box around the inlet (most likely a 4" high flow cone filter) not being force fed from the front of the car to reduce turbulence, then thru a 4" inlet tube.
A MAP car could go straight to the TB at 4", a 3" MAF system (as we have found out) wouldnt suffer from that bottleneck.
Sorry, I was in a bit of hurry yesterday, just posted the videos and went to sleep.
1: first two runs were with cold air, last two were with stock cover
2: there was aprox. 1 hour between the runs and outside air temp didn't change during that time. If I remember correctly it was arounf 60F, very little side wind during the day.
3:No I didn't time, I was going to time my runs using sports tracker but somehow I forgot it.
4/5 I dont have any pics right now, car is packed away for the winter, I can take pics within few weeks when I go see her.
But it's basicly 4"x3" fiberglass duct that not only takes the air in, but directs it towards the filter. I used a rubber seal on the hood to seal out the filter. I didn't want any air packing into engine compartment and making me slower.
My .2 cents are that turbulance with the cold air cover is making it less aerodynamic and that way slower. I actually had laptop hooked in for the cold air passes, just wanted to see if there's any positive pressure in the intake manifold, there wasn't. I try to see if I can still recover those log files
Many thanks, Tapio! Needless to say, I am disappointed to discover that my labors may have been for naught. Originally, I just wanted my C4 to have a Grill. But, one thing led to another and soon, my SOTP Dyno kicked in to justify my efforts!
I'm still not convinced that something hasn't been gained but I'm going to have to toot my horn a little less loudly until I can figure out exactly what!
Hi DrDyno,
even tho he was talking about air movement inside the tube, the bit about flow being greater with less velocity was interesting,
BTW i actually like the setup you have made for your car
I think what we are talking about here is strictly performance related, trying to squeeze that last bit out, and the big question is are the 'cold air' systems that we make actually worth anything.
what we need is someone to make up an enclosed unit around the filter but not being directly fed from airflow from the front of the car, and one where it is, and see what the result is, and that result would have to come from some sort of timed event (eg racing)
I haven't seen a pic of Tapio's inlets , but if his 2 setups match the above , then the question has probably been answered.
Maybe the best c4 setup would be a sealed box around the inlet (most likely a 4" high flow cone filter) not being force fed from the front of the car to reduce turbulence, then thru a 4" inlet tube.
A MAP car could go straight to the TB at 4", a 3" MAF system (as we have found out) wouldn't suffer from that bottleneck.
08-21-2014, 10:37 AM
