C7 Z06 ?'s 15% Lower and 2.31 Upper Pulley
03-18-2018, 12:39 PM
#22
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PSI can vary based on a few factors other then just the size of the upper and lower pulley one runs, at least that is my direct experience...
my personal psi with the 15% lower and 2.31 upper was 13.1, that may seem low to some, but consider the fact that for starters, I run BBEs FULL exhaust setup, ceramic coated headers, Midpipe and Mufflers, all of which lower back pressure and create a more free flowing exhaust, thereby lowering the measured boost. Also removing both sets of cats with BBEs system lowers back pressure, and in turn boost as well.
I'll reserve full comment on what happens when you add a larger TB and open up the snout till I remove the possible factor of belt slip from the equation, which always has to be looked at when down sizing pulleys...
The common thought is that adding a larger filter/cold air induction set up and or TB/snout should add boost by freeing up air flow to the supercharger...
my personal psi with the 15% lower and 2.31 upper was 13.1, that may seem low to some, but consider the fact that for starters, I run BBEs FULL exhaust setup, ceramic coated headers, Midpipe and Mufflers, all of which lower back pressure and create a more free flowing exhaust, thereby lowering the measured boost. Also removing both sets of cats with BBEs system lowers back pressure, and in turn boost as well.
I'll reserve full comment on what happens when you add a larger TB and open up the snout till I remove the possible factor of belt slip from the equation, which always has to be looked at when down sizing pulleys...
The common thought is that adding a larger filter/cold air induction set up and or TB/snout should add boost by freeing up air flow to the supercharger...
03-18-2018, 01:05 PM
#24
Pro
Headers and no cats are the only part of your exhaust that will drop pressure. A cam/Heads will drop it a lot more. Also, 13.1 is very low for those pulleys. Shows two things, the most likely is when you spin the blower too fast it will actually compress air so inefficiently that you will lose boost and power, this is amidst already increased heat and pulled timing/detonation that lowers the power. You’ll make a lot of torque with a 2.3/15% but your peak power will drop off. If any of you follow Race Proven Motorsports, the same thing happened with Mike’s Vette on stock blower. Too much pulley, loss of boost and bad peak power.
An 18% alone should net you 15 PSI or more. RPM claims 17 PSI. Again, Headers/“Full exhaust” does not lower that number, that’s already factoring the 1-2 PSI loss from Headers.
The LT4 is a tricky engine when shooting for power on the stock blower. It’s not like the LS9 or even LSA that the more pulley you threw at it the more power you’d make up until a ceiling. It’s similar with the LT4 except the ceiling is a LOT lower. Much better results come from a more gentle approach to making power with the LT4. Less pulley and focus on porting, fuel, meth, and tuning.
You will get better drivable results with a nice pulley size, 5%, 9%, 15% or 18%, and proper fueling and supporting parts. Pulleying the **** out of the stock blower is proven to not = better results without trade offs and sometimes failure or power decrease.
An 18% alone should net you 15 PSI or more. RPM claims 17 PSI. Again, Headers/“Full exhaust” does not lower that number, that’s already factoring the 1-2 PSI loss from Headers.
The LT4 is a tricky engine when shooting for power on the stock blower. It’s not like the LS9 or even LSA that the more pulley you threw at it the more power you’d make up until a ceiling. It’s similar with the LT4 except the ceiling is a LOT lower. Much better results come from a more gentle approach to making power with the LT4. Less pulley and focus on porting, fuel, meth, and tuning.
You will get better drivable results with a nice pulley size, 5%, 9%, 15% or 18%, and proper fueling and supporting parts. Pulleying the **** out of the stock blower is proven to not = better results without trade offs and sometimes failure or power decrease.
03-18-2018, 01:36 PM
#25
to give the op an idea my setup thats a 2.175 upper and 18% lower with 2in primary headers to 3in exhaust to akrapovic mufflers with heads and cam ported blower with a 103tb with a custom 4.5in intake produces a spike of 17psi and falls down to 15.5 by redline...thats all with very little back pressure as iv freed up as much as i could...thats zr1 territory with our tiny blowers
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BigNastyZO7 (05-11-2019)
03-18-2018, 02:08 PM
#27
Team Owner
Headers and no cats are the only part of your exhaust that will drop pressure. A cam/Heads will drop it a lot more. Also, 13.1 is very low for those pulleys. Shows two things, the most likely is when you spin the blower too fast it will actually compress air so inefficiently that you will lose boost and power, this is amidst already increased heat and pulled timing/detonation that lowers the power. You’ll make a lot of torque with a 2.3/15% but your peak power will drop off. If any of you follow Race Proven Motorsports, the same thing happened with Mike’s Vette on stock blower. Too much pulley, loss of boost and bad peak power.
An 18% alone should net you 15 PSI or more. RPM claims 17 PSI. Again, Headers/“Full exhaust” does not lower that number, that’s already factoring the 1-2 PSI loss from Headers.
The LT4 is a tricky engine when shooting for power on the stock blower. It’s not like the LS9 or even LSA that the more pulley you threw at it the more power you’d make up until a ceiling. It’s similar with the LT4 except the ceiling is a LOT lower. Much better results come from a more gentle approach to making power with the LT4. Less pulley and focus on porting, fuel, meth, and tuning.
You will get better drivable results with a nice pulley size, 5%, 9%, 15% or 18%, and proper fueling and supporting parts. Pulleying the **** out of the stock blower is proven to not = better results without trade offs and sometimes failure or power decrease.
An 18% alone should net you 15 PSI or more. RPM claims 17 PSI. Again, Headers/“Full exhaust” does not lower that number, that’s already factoring the 1-2 PSI loss from Headers.
The LT4 is a tricky engine when shooting for power on the stock blower. It’s not like the LS9 or even LSA that the more pulley you threw at it the more power you’d make up until a ceiling. It’s similar with the LT4 except the ceiling is a LOT lower. Much better results come from a more gentle approach to making power with the LT4. Less pulley and focus on porting, fuel, meth, and tuning.
You will get better drivable results with a nice pulley size, 5%, 9%, 15% or 18%, and proper fueling and supporting parts. Pulleying the **** out of the stock blower is proven to not = better results without trade offs and sometimes failure or power decrease.
Bingo people push these little blowers out side the efficiency range. Two pulleys that is too much blower speed is a lot of hot air. Mine hit's 11.9 boost with stock pullies.
EVEN with 2 inch headers and Halltech and tric.
Last edited by 3 Z06ZR1; 03-18-2018 at 02:09 PM.
03-18-2018, 05:27 PM
#30
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While I agree with some of what's been said regarding too much boost, I've road raced with this combo for 25 minutes at 90+ degrees, and ran the same 165 MPH down the main straight on the first and last lap of the session, NO POWER LOSS, start to finish...
LOTS OF COOLING MODS AND METH...
The top/Black curve is when I added the 2.3 upper Pulley to the 15% lower existing pulley, holds Boost and power longer... the average pull with this full combo was 680 RWHP and 700 RWT at 13.1 pounds of steady boost.
LOTS OF COOLING MODS AND METH...
The top/Black curve is when I added the 2.3 upper Pulley to the 15% lower existing pulley, holds Boost and power longer... the average pull with this full combo was 680 RWHP and 700 RWT at 13.1 pounds of steady boost.
Last edited by jbsblownc5; 03-18-2018 at 05:31 PM.
03-18-2018, 06:09 PM
#31
Headers and no cats are the only part of your exhaust that will drop pressure. A cam/Heads will drop it a lot more. Also, 13.1 is very low for those pulleys. Shows two things, the most likely is when you spin the blower too fast it will actually compress air so inefficiently that you will lose boost and power, this is amidst already increased heat and pulled timing/detonation that lowers the power. You’ll make a lot of torque with a 2.3/15% but your peak power will drop off. If any of you follow Race Proven Motorsports, the same thing happened with Mike’s Vette on stock blower. Too much pulley, loss of boost and bad peak power.
An 18% alone should net you 15 PSI or more. RPM claims 17 PSI. Again, Headers/“Full exhaust” does not lower that number, that’s already factoring the 1-2 PSI loss from Headers.
The LT4 is a tricky engine when shooting for power on the stock blower. It’s not like the LS9 or even LSA that the more pulley you threw at it the more power you’d make up until a ceiling. It’s similar with the LT4 except the ceiling is a LOT lower. Much better results come from a more gentle approach to making power with the LT4. Less pulley and focus on porting, fuel, meth, and tuning.
You will get better drivable results with a nice pulley size, 5%, 9%, 15% or 18%, and proper fueling and supporting parts. Pulleying the **** out of the stock blower is proven to not = better results without trade offs and sometimes failure or power decrease.
An 18% alone should net you 15 PSI or more. RPM claims 17 PSI. Again, Headers/“Full exhaust” does not lower that number, that’s already factoring the 1-2 PSI loss from Headers.
The LT4 is a tricky engine when shooting for power on the stock blower. It’s not like the LS9 or even LSA that the more pulley you threw at it the more power you’d make up until a ceiling. It’s similar with the LT4 except the ceiling is a LOT lower. Much better results come from a more gentle approach to making power with the LT4. Less pulley and focus on porting, fuel, meth, and tuning.
You will get better drivable results with a nice pulley size, 5%, 9%, 15% or 18%, and proper fueling and supporting parts. Pulleying the **** out of the stock blower is proven to not = better results without trade offs and sometimes failure or power decrease.
i pullied the **** out of my setup and im making more power than any one is on the lt4 blower and we rent even finished tuning yet....mustang dyno 850 whp so far should finish around close to 900 is my guess
Last edited by srtz06; 03-18-2018 at 06:14 PM.
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jbsblownc5 (03-18-2018)
03-18-2018, 06:13 PM
#32
PSI can vary based on a few factors other then just the size of the upper and lower pulley one runs, at least that is my direct experience...
my personal psi with the 15% lower and 2.31 upper was 13.1, that may seem low to some, but consider the fact that for starters, I run BBEs FULL exhaust setup, ceramic coated headers, Midpipe and Mufflers, all of which lower back pressure and create a more free flowing exhaust, thereby lowering the measured boost. Also removing both sets of cats with BBEs system lowers back pressure, and in turn boost as well.
I'll reserve full comment on what happens when you add a larger TB and open up the snout till I remove the possible factor of belt slip from the equation, which always has to be looked at when down sizing pulleys...
The common thought is that adding a larger filter/cold air induction set up and or TB/snout should add boost by freeing up air flow to the supercharger...
my personal psi with the 15% lower and 2.31 upper was 13.1, that may seem low to some, but consider the fact that for starters, I run BBEs FULL exhaust setup, ceramic coated headers, Midpipe and Mufflers, all of which lower back pressure and create a more free flowing exhaust, thereby lowering the measured boost. Also removing both sets of cats with BBEs system lowers back pressure, and in turn boost as well.
I'll reserve full comment on what happens when you add a larger TB and open up the snout till I remove the possible factor of belt slip from the equation, which always has to be looked at when down sizing pulleys...
The common thought is that adding a larger filter/cold air induction set up and or TB/snout should add boost by freeing up air flow to the supercharger...
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jbsblownc5 (03-18-2018)
03-18-2018, 06:20 PM
#33
I'm installing this week on my 2017 auto Z06 a 15% upper pulley with the existing 9% lower the car has right now. Also adding Weapon X Heat Exchanger, Meth, Nick Williams 103mm TB and porting the snout and manifold of the supercharger.
Car already has as I said a 9% IW lower, x pipes, cat deletes, expansion tank and Halltech Intake.
Hope the car does not heat soak as you guys are speaking here on this thread. It will not have the 15% lower and 15% upper as it is stated here. So I hope I'm not on the thin line of heat soak issues.
Car already has as I said a 9% IW lower, x pipes, cat deletes, expansion tank and Halltech Intake.
Hope the car does not heat soak as you guys are speaking here on this thread. It will not have the 15% lower and 15% upper as it is stated here. So I hope I'm not on the thin line of heat soak issues.
Last edited by PRZ; 03-18-2018 at 06:22 PM.
03-18-2018, 06:45 PM
#34
I'm installing this week on my 2017 auto Z06 a 15% upper pulley with the existing 9% lower the car has right now. Also adding Weapon X Heat Exchanger, Meth, Nick Williams 103mm TB and porting the snout and manifold of the supercharger.
Car already has as I said a 9% IW lower, x pipes, cat deletes, expansion tank and Halltech Intake.
Hope the car does not heat soak as you guys are speaking here on this thread. It will not have the 15% lower and 15% upper as it is stated here. So I hope I'm not on the thin line of heat soak issues.
Car already has as I said a 9% IW lower, x pipes, cat deletes, expansion tank and Halltech Intake.
Hope the car does not heat soak as you guys are speaking here on this thread. It will not have the 15% lower and 15% upper as it is stated here. So I hope I'm not on the thin line of heat soak issues.
what is a 15% upper never heard of that
03-18-2018, 09:48 PM
#35
Pro
03-18-2018, 09:51 PM
#36
Pro
That's impressive but what are your tradeoffs? I left a clause in there to deal with this kind of a setup. There are people that do what you do and sure there cars make good power but how sustainable are they? How reliable? What trade offs do you have? Do you deal with lots of heat problems or spend your 401K on cooling mods, heat exchangers, E85, Meth, and more? Not trying to talk crap here but it just doesn't make sense to push the 1740 blower like that IMO, just put a 2300/Whipple/ProCharger on it...
03-18-2018, 10:52 PM
#37
I never dynoed the car, will be doing that in the next couple of weeks. I measure Performace by acceleration times.. 100-140 mph, as an example.
As as for the Logged boost, I read somewhere it’s not as accurate of a reading as I would get if using a gauge.
As as for the Logged boost, I read somewhere it’s not as accurate of a reading as I would get if using a gauge.
03-18-2018, 11:08 PM
#38
Burning Brakes
Thread Starter
Thanks for the continuous replies fellas, I'm learning a lot. I'm slowly thinking about just going straight for the kill and installing a Magnuson 2300 upgrade kit for $5k there are just so many options available! 
03-19-2018, 11:11 AM
#39
Pro
Do it. It's definitely worth it for the HP and cooling.
03-20-2018, 10:08 PM
#40
That's impressive but what are your tradeoffs? I left a clause in there to deal with this kind of a setup. There are people that do what you do and sure there cars make good power but how sustainable are they? How reliable? What trade offs do you have? Do you deal with lots of heat problems or spend your 401K on cooling mods, heat exchangers, E85, Meth, and more? Not trying to talk crap here but it just doesn't make sense to push the 1740 blower like that IMO, just put a 2300/Whipple/ProCharger on it...
totally understand wat you mean, i also have a lot of cooling mods done, meth e85, iv done 4-5 back to back dyno pulls with no cool down time and the hp difference from the 1st run to the 4 was 2 hp....and as far as reality goes nvr had a problem yet, as a precaution ill fresh up the blower (new bearings) about every 10k miles.
value wise its obviously not worth it spending all that money on a set up like that but i was very set on maxing out the stock bottom end with stock blower setup. an example why is the early power band of the lt4 blower gives me a nice advantage vs lets say an f1x making 950whp or even a bigger pd blower. i dunno if that makes sense or not.
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jbsblownc5 (03-20-2018)