help me out here.

there is a company saying they are seeing over double the stock rwhp at only 8psi. the set up is a gt35r on a 3.5L 5 cyl with an intercooler. stock rwhp is around 180 and they claim 390rwhp at 8psi. no cam change, no head work, no internal work. i think this motor is over 10-1 compresion. i dont know anything about the tune but lets just say it was optimized for 8psi.

i posted up that those numbers do not seem realistic but stoped short of raising the BS flag.

for my set up's it took 18psi to double the hp on a stock 4.8. it also took 18psi for me to double the hp on a camed 6.0. from everything i read it will take at least 14.7psi to double the hp on any motor.

is there ANY way those numbers could be true?

 

oh yeah, these numbers are thru a 4l60e with an unlocked converter.

 

Well double is very doubtful. If certain things were done to the tune and the kind of fuel maybe. Lets say that 3.5l has a ultra conservitave tune to begin with. Also it is dynoed with the 87 oct. it loves and has stock exhaust. Well 8 psi alone will not double the hp. But if you have really good fuel you can get some more hp with more ignition timing, also you get more by not having a restrictive intake, and the better exhaust is adding some too. In a perfect worl 8psi would be worth about a 50-60% gain in fwhp. I still do not see the numbers being right though. I would say 75% max with a good exhaust and IAT's near or below 60 degrees with good fuel and the right amount of timing.

 

Wow who built your engine Did you make the power u have in your Sig with the 408 or something else?

With 8psi my car gained 88%, but that is with the help of headers, exhaust, and cam.

The blower alone gave me 165rwhp at 8psi so i doubt the Inline 5 would double the HP with 8psi.

 

Sounds like bollocks to me - but I've been wrong before

Doubling power at 14psi is easy with a few improvements to the engine, less boost if significant improvements are made... however to double power at 8psi on a STOCK engine I've never seen happen and it defies the laws of physics at least as I understand them.

Even if the 390hp was at the flywheel it would be a stretch allowing as much as a 20% loss - that'd make it 312rwhp (few powerful cars lose anywhere near 20%) - which is still a 73% improvement...

I'd say 8psi can give at most around 66% assuming the most efficient of designs and turbo sizings, any more gain than that is coming from something else IMHO - and VERY few could get even 66% from 8psi without engine changes.

 

I have always heard, it takes 17 psi to double your engines na power.

 

In theory it takes 14.7 psi to double output.

If the only change made to the engine was the turbo system (no H/C...), I'd call absolute BS at the output being doubled with only 8 psi.

 

is this through Hahn?

 

Ir really depends, A friend trippled his factory RWHP on a 2000 V6 mustang automatic with an efficient turbo setup, and just under 20# of boost.

Boost is just a measure of restriction, see what the actual airflow is between NA and with turbo for that motor. As you start to force the air into the motor, you will become more efficient as long as you can keep the exhaust backpressure low, if your backpressure remains high, it takes a lot more 'boost' to make the same power.

Ryan

 

i'll raise the flag jim.

 

Gt35 us faurky decently sized for an inline 5. I wouldn't complete call BS becuase the GT35 flows pretty well and as long as it flows a little more than twice as much air than if it were NA it should double the HP (or close to it whenever you figure in stock tune doesn't run the motor completely efficiently because of emissions and such)

 

I'm going with the flag myself.

 

In theory it is possible that the motor took all of the additional air flow without restriction. IF that is the case the turbocharger could be pushing a ton of air and the intake manifold only seeing 8psi of positive pressure. Now, it says no cam change, no head work, no internal work, so I do not think this is likely for this particular motor.
Possible, but not probable I'd say.

 

if the motor was high compression to start off, and they are using race gas.

i'm thinking that 8psi boost on a car with 14:1 compression would have twice the increase as 8psi on a car with 7:1 if you can follow me there.

 

i dont get it. all of the math i have seen says you need to double the presure to double your hp. 14.7psi to get double the hp and that assumes a perfect world like a 100% efficient turbo and no aditional back presure from the turbo.

the only thing i see here that makes me think it could be remotly posiable would be if the stock tune is so far off that the motor is just held back at the stock 180rwhp.

 

i could see the high compresion motor gaining more hp but not a higher percentage of hp.

 

my first motor with the turbotech race kit on it (9:1) made301rwhp with headers and 630rwhp at 12psi both on 93 octane only.

thats the only leg i have to stand on in the arguement

 

in a perfect world, 14.7 psi should double your hp, but with the added heat, and draw on the motor it is not likely to see it. Like Parish said, I would look to something else as the reason, like the tuning. I still stick to my statement about 17psi to double an engines na power. Even on desktop dyno, that is almost right every time that I have played around with it.

 

I think it just means that the original tune was far from optimized.

 

Some motors will do some will not. Take for instance the pro turbo setup on a 4.6gt mustang will double the hp at 8 psi. Allthough it is the only car I have ever seen do it. Stock those car make 205-230rwhp on pump gas. Just adding the turbo system and giving it an aggresive street tune those same cars are making 430rwhp and 520rwtq on the same pump gas. I have not seen any ls1's do it as of yet.