better numbers with smaller turbo! 404ci + 76mm
12-27-2010, 01:09 PM
#22
600rwhp is pretty low for a 404cu turbo car on 12psi with a 6 speed. my setup was 200+ rwhp through the th400 at the same boost level and the th400 is 100-150rwhp less than a Manaul 6 speed
12-27-2010, 03:24 PM
#23
"What, he should be running an 88mm!" "oh theres no way a 76mm will work on that motor"
This is what everyone says to me at car meets and on the forum, but oh wait, it does work! I went from a turbonetics 78mm "hurricane" to a Precision 76mm GTS.
(NEW DYNO NUMBERS This is on a load bearing "dyno dynamics" dyno)
(OLD DYNO NUMBERS! non-load bearing dyno)
You might have seen my sticky on https://ls1tech.com/forums/forced-in...ifold-kit.html and in there I explained how i built this car to be A STREET CAR. not built for 1/4 mile times or to compete with, but to be a quick spooling street machine! I am sooooooo happy with how it turned out! On the same dyno it was previosly making 580ish rwhp and 650ish rwtq on about 13psi and now its set between 14-15psi, spools much quicker, pulls much harder, and is wayy more fun to drive!
yes an 88mm would pull better up top, but would also spool a lot slower and would be less fun for me on the street. ill prob take this to the track for fun occasionally but i dont need to be the fastest guy out there. So heres the proof that you can make good power while spooling quickly!
This is what everyone says to me at car meets and on the forum, but oh wait, it does work! I went from a turbonetics 78mm "hurricane" to a Precision 76mm GTS.
(NEW DYNO NUMBERS This is on a load bearing "dyno dynamics" dyno)
(OLD DYNO NUMBERS! non-load bearing dyno)
You might have seen my sticky on https://ls1tech.com/forums/forced-in...ifold-kit.html and in there I explained how i built this car to be A STREET CAR. not built for 1/4 mile times or to compete with, but to be a quick spooling street machine! I am sooooooo happy with how it turned out! On the same dyno it was previosly making 580ish rwhp and 650ish rwtq on about 13psi and now its set between 14-15psi, spools much quicker, pulls much harder, and is wayy more fun to drive!
yes an 88mm would pull better up top, but would also spool a lot slower and would be less fun for me on the street. ill prob take this to the track for fun occasionally but i dont need to be the fastest guy out there. So heres the proof that you can make good power while spooling quickly!
12-27-2010, 06:19 PM
#25
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Technically he could. If he got a bigger engine, or a better intercooler, or a more efficient turbo
12-27-2010, 09:18 PM
#29
The wheel design is also more efficient on the precision allowing it to flow a higher volume of air. also if you compare the inducer size and exducer size of the compressor wheels, they are pretty similar. Im by no means a turbo expert, as im sure that could be explained a little better, but that should give you an idea.
12-27-2010, 09:38 PM
#31
if the turbine area is similar, ie similar backpressure numbers, 13 psi on a 78mm = 13 psi on a 76mm = 13 psi on any turbo that is in a similar part of the efficiency island. the hp should be darn near the same
I think something else is at play here.
I think something else is at play here.
Last edited by 71 chevy; 12-27-2010 at 09:49 PM.
12-28-2010, 01:22 AM
#32
just because they are similar size wheels, doesnt mean that they flow the same. and psi means nothing, just a measurement of restriction. i know that the backpressure is actually less with this turbo.
on the previous setup, the backpressure was causing the wastegate to open prematurely... i had a 17lb spring with a boost controller turned up to keep it shut enough to make 13 psi.... bolted on the new turbo, and now that 17lb spring was actually making 17psi. I had to remove the spring in the wastegate and swap it with a 10lb to get it back to my desired boost pressure.
but above all else, im not here to argue boost theory with you. before i purchased this turbo, i was told by multiple turbo vendors that this turbo would outflow the previous one. thats just a fact.
12-28-2010, 08:30 AM
#34
so a 12" straight blade electric fans flows the same air as a 12" S-blade electric fan? not neccesarily. usually a s-blade will flow more CFM
just because they are similar size wheels, doesnt mean that they flow the same. and psi means nothing, just a measurement of restriction. i know that the backpressure is actually less with this turbo.
on the previous setup, the backpressure was causing the wastegate to open prematurely... i had a 17lb spring with a boost controller turned up to keep it shut enough to make 13 psi.... bolted on the new turbo, and now that 17lb spring was actually making 17psi. I had to remove the spring in the wastegate and swap it with a 10lb to get it back to my desired boost pressure.
but above all else, im not here to argue boost theory with you. before i purchased this turbo, i was told by multiple turbo vendors that this turbo would outflow the previous one. thats just a fact.
just because they are similar size wheels, doesnt mean that they flow the same. and psi means nothing, just a measurement of restriction. i know that the backpressure is actually less with this turbo.
on the previous setup, the backpressure was causing the wastegate to open prematurely... i had a 17lb spring with a boost controller turned up to keep it shut enough to make 13 psi.... bolted on the new turbo, and now that 17lb spring was actually making 17psi. I had to remove the spring in the wastegate and swap it with a 10lb to get it back to my desired boost pressure.
but above all else, im not here to argue boost theory with you. before i purchased this turbo, i was told by multiple turbo vendors that this turbo would outflow the previous one. thats just a fact.
the engine is a power consumer though, so at 5000 rpms your engine with your cam at your engine's VE ratio is only consuming so much air.
you could put a 106mm turbo or a 70mm turbo on it and it will consume the exact same amount of air, providing that both turbos can supply that amount of air.
the only thing that will change this is the increasing the pressure ratio at the atmosphere. so lets say that at 14.7 psi of boost your engine is making 800hp and consuming 88lbs of air, put a big aZZ turbo on it that will supply 200lbs of air and your engine will still only consume 88lbs of air. put a 90lbs turbo on it and it will still only consume 88lbs of air, which equals 800hp on your engine.
Im saying that is is quite impossible to see a 123rwhp jump in power at the same pressure level if both turbos were in an efficient range.
not arguing, just trying to find the discrepancy.
12-28-2010, 08:47 AM
#35
yes. 900-950rwhp
13psi through my current motor and turbo make more power than my old pt88mm 370cu on 22psi of boost.
with good heads(360cfm l92/ls3/afr) on your motor and a 88mm t6 turbo through a 6 speed you should hit 1000rwhp with a 6 speed at 17psi.
also i dont the title of the thread is misleading, a junk ebay 78mm of course will not out perform a nice 76mm gts. really the 76mm flows more lbs/min of air than the ebay 78mm
just to clearify, im not knocking your setup. i like the car, its very clean and looks sharp.
Last edited by cjg454ss; 12-28-2010 at 08:55 AM.
12-28-2010, 09:53 AM
#37
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The Precision billet wheel (if the op is using the billet version) brings some power over the Turbonetics wheel. If both compressors are in the sweet spot in the island at a low PR...not so much....higher psi/PR's...yep...
The Precision 75mm turbine brings a lot of power potential over the Turbonetics 68mm turbine....especially in a single turbo system. Helps out a choke point. Much lower backpressure in the Precision turbine...That's why people are starting to "crutch" single Turbonetics 68mm turbines with larger and larger turbine AR's...81's to 96's to 1.15's to custom 1.xx.
Nice results on the build. Should be a killer street and track car.
12-28-2010, 10:10 AM
#38
FormerVendor
everything else being equal, the s blade will outflow the straight blade.
the engine is a power consumer though, so at 5000 rpms your engine with your cam at your engine's VE ratio is only consuming so much air.
you could put a 106mm turbo or a 70mm turbo on it and it will consume the exact same amount of air, providing that both turbos can supply that amount of air.
the only thing that will change this is the increasing the pressure ratio at the atmosphere. so lets say that at 14.7 psi of boost your engine is making 800hp and consuming 88lbs of air, put a big aZZ turbo on it that will supply 200lbs of air and your engine will still only consume 88lbs of air. put a 90lbs turbo on it and it will still only consume 88lbs of air, which equals 800hp on your engine.
Im saying that is is quite impossible to see a 123rwhp jump in power at the same pressure level if both turbos were in an efficient range.
not arguing, just trying to find the discrepancy.
the engine is a power consumer though, so at 5000 rpms your engine with your cam at your engine's VE ratio is only consuming so much air.
you could put a 106mm turbo or a 70mm turbo on it and it will consume the exact same amount of air, providing that both turbos can supply that amount of air.
the only thing that will change this is the increasing the pressure ratio at the atmosphere. so lets say that at 14.7 psi of boost your engine is making 800hp and consuming 88lbs of air, put a big aZZ turbo on it that will supply 200lbs of air and your engine will still only consume 88lbs of air. put a 90lbs turbo on it and it will still only consume 88lbs of air, which equals 800hp on your engine.
Im saying that is is quite impossible to see a 123rwhp jump in power at the same pressure level if both turbos were in an efficient range.
not arguing, just trying to find the discrepancy.
The power was found on this car due to decreased backpressure.
A hypothetical example.
400ci LS
72mm P-trim 20psi boost 60psi backpressure
76mm GTS 20psi boost 40psi backpressure
96mm F trim 20psi boost 30psi backpressure
So as you can see a larger turbo which has more exhaust side flow allows the engine to consume more air and make more horsepower at the same boost level due to decreased backpressure. The trade off is that peak boost will be realized at a higher rpm (but it will make drastically more high rpm power)
12-28-2010, 10:58 AM
#39
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Basically all the above is incorrect.
The power was found on this car due to decreased backpressure.
A hypothetical example.
400ci LS
72mm P-trim 20psi boost 60psi backpressure
76mm GTS 20psi boost 40psi backpressure
96mm F trim 20psi boost 30psi backpressure
So as you can see a larger turbo which has more exhaust side flow allows the engine to consume more air and make more horsepower at the same boost level due to decreased backpressure. The trade off is that peak boost will be realized at a higher rpm (but it will make drastically more high rpm power)
The power was found on this car due to decreased backpressure.
A hypothetical example.
400ci LS
72mm P-trim 20psi boost 60psi backpressure
76mm GTS 20psi boost 40psi backpressure
96mm F trim 20psi boost 30psi backpressure
So as you can see a larger turbo which has more exhaust side flow allows the engine to consume more air and make more horsepower at the same boost level due to decreased backpressure. The trade off is that peak boost will be realized at a higher rpm (but it will make drastically more high rpm power)
People will say a turbo is good to X amount of horsepower so you think well I'm not making that so it must not be the turbo, not taking the turbine side of the turbo into consideration.
