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.
I have a vs billet wheel 75mm with the 87/82 1.1 t4. 10.2 to 1, rod/piston, btr stage 2 cam, 243 headed aluminum 5.3, ls6 intake/tb (2.25" hotside, tr1245 ic, ts 50mm gate, tial 50mm bov, holley terminator, th400). Car peaks power around 6500 and drops after that. Full spool is around 3500, seems to light pretty decent. I would like to rev the car a bit higher, 7200-7500 due to gearing/speed. I talked to Viren and he thinks there is too much backpressure and its out of hotside at that RPM. Would stepping up to a vs80 or a genuine S476 get me what I want? I want to retain whatever I can for spool as its a street car.
What does the turbine specification 96/88 portray? In other turbos , say the PT7675, it's a 76mm compressor wheel and a 75mm turbine wheel. With that VS80 it's essentially a 80mm compressor and a 88mm turbine, is it not? What does that 96/88 turbine designation imply and why is it noteworthy ?
I actually have the T6 1.32 A/R slip-fit race cover version of that VS80. I'm installing it this Winter.
Originally Posted by V8EATR
I should have clarified, the VS 80 with the 96/88 1.25 t4 or the S476 with the 1.25 ar.
What does the turbine specification 96/88 portray? In other turbos , say the PT7675, it's a 76mm compressor wheel and a 75mm turbine wheel. With that VS80 it's essentially a 80mm compressor and a 88mm turbine, is it not? What does that 96/88 turbine designation imply and why is it noteworthy ?
I actually have the T6 1.32 A/R slip-fit race cover version of that VS80. I'm installing it this Winter.
to fully get the advantage of the 96mm turbine a fully devided 2 1/4 hot side with a t6 flange makes a big differance in spool and top end power. . im not saying a big turbine t4 is not an improvment but it will spool slower and the t4 is a bottleneck going into the turbine housing.
I have a vs billet wheel 75mm with the 87/82 1.1 t4. 10.2 to 1, rod/piston, btr stage 2 cam, 243 headed aluminum 5.3, ls6 intake/tb (2.25" hotside, tr1245 ic, ts 50mm gate, tial 50mm bov, holley terminator, th400). Car peaks power around 6500 and drops after that. Full spool is around 3500, seems to light pretty decent. I would like to rev the car a bit higher, 7200-7500 due to gearing/speed. I talked to Viren and he thinks there is too much backpressure and its out of hotside at that RPM. Would stepping up to a vs80 or a genuine S476 get me what I want? I want to retain whatever I can for spool as its a street car.
Need more information. Best answer is to tap your hot side and see what your back pressure is. What kind of boost are you running? trap speeds? dyno numbers? There's a lot more to a combination than turbo size... My setup had similar RPM issues and had nothing to do with backpressure or turbo size. Has more to do with the cam/intake, springs, gearing, converter...
What converter? Does it hang on the converter around 6500 and mph increases, but RPM doesn't? What happens if you take it over 6500 in 1st, 2nd? what do you shift out of 1st at? what kind of RPM drop?
If your back pressure is higher than 2:1 with your current setup I wouldn't run another T4 turbo. The tiny step up in AR isn't going to do much. The larger wheel will defiantly help, but again it's time to step up to a T6 if you are seeing "high" back pressure.
Not sure on back pressure, I'll look into putting a gauge and checking that out. Peak boost I run is 21-22, gate is about 13-15 depending on temp. It did dyno 730/634 on a dynojet on 16.5psi. Cam is a BTR stage 2, 226/231 .605/.588, BTR .660 springs, 3.55 gears, th400. The first converter was just a generic 11" unit that was very tight but was super efficient up top. I ended up with a custom 245mm unit that ended up being too loose, I'm getting it re-stalled right now. The original converter would show 150mph on the dyno at about 6800 rpm, the new converter showed 125mph so it was too sloppy. I have taken it to 7200 in first and second but feels like its nosing over which is what is showed on the dyno.
No track time yet but the car is fast (to me anyways), its pulled handily a couple 138-143 trap cars by quite a lot on the street so its making some steam. I think its got 150mph in it with the right converter. I like the response of the current setup but I would like some more rpm and some more speed out of the car. Its 99% street/highway car so I don't want it to be a lag monster. Car doesn't even have a trans brake.
Sounds pretty healthy to make 730whp on 16lbs. The T6 won't be laggy on a healthy 5.3 like that IMO. I ran the same cam on a 4.8 with the 1.32 S480 and it wasn't laggy IMO... You'll just make more power per pound all around. Being able to physically fit the thing is another story. Those 87/96 wheel 1.25 T4's are the hot ticket if you need to stay T4. The Forced inductions units have a better comp wheel design but you do pay for it. If you're stuck with a T4 you need all the help you can get.
Once you get some BP data you'll know if the turbo is the issue. Track or dyno also helps. You'll gain X amount per pound (HP or MPH) when its in its happy place. Then power drops like a rock per pound when it's not.
I'd lean towards that converter... something sounds off.
That dyno was stock compression with stock 862 heads. Now it has 243 heads with a good valve job and 10.2 vs the stock 9.6. Im sure it would make even more on the same boost with the original converter. I may just bite the bullet and get the vs80/96 1.25 t4 and give it a go. If I hate it I will sell it and only be out a few bucks.
6 Common C5 Corvette Failures and What's Involved In Repairing Them
Slideshow: From wobbling harmonic balancers to failed EBCMs, these are the issues that define long-term C5 ownership and what repairs typically involve.
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph
Slideshow: A modern Camaro transformed into a retro icon, this limited-run "Bandit" build blends nostalgia with brute force in a way few revivals manage.
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked
Slideshow: Cadillac didn't just crash the high-performance luxury vehicle party, it showed up loud, supercharged, and occasionally a little unhinged...
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes
Slideshow: A one-off sports car that looks like a vintage Italian exotic-but hides a C6 Corvette underneath-just sold for the price of a new mid-engine Corvette.
vs75 to vs80? 
