Silver_TransAm

iTrader: (2)

My dad and I just finished putting together twin rear mount turbo setup on his 8.1L 2500HD pickup with allison trans. The turbos are turbonetics t62-1 with a .81 exhaust housing and a 5 pound wastegate spring with front mount intercooler. Well once we finally got all the small pieces together we took it for run and well.. no boost. It does make a pound or two on the shift but then goes away. What could be the problem? Are the turbos the wrong size?

hellbents10

iTrader: (10)

alot of things, start checking connections first off. Second you put the turbos in the wrong spot. They are supposed to be in the engine compartment.....j/k. All joking aside, also check your springs in the gates and make sure they are not a 3psi spring or something silly like that.

Silver_TransAm

iTrader: (2)

connections solid went over them 4 times after run and still notin. The spring is a 5 pounder for sure tested it with compressed air. What else could it be?

hellbents10

iTrader: (10)

Well as far as turbo sizing goes that would be good for about 1000-1100fwhp on that motor in conventional setup. It should make a full 5psi by 3800-4200 even with a rear mount setup on those cubes. I image we are talking stock manifolds and 2.5" pipe to the turbos? Wrapped? That motor should kick those turbos like a mule on steroids really. There has to be a leak or a problem with the gage. Is it pulling good, AFR, ignition advance???

Schantin

iTrader: (6)

Where is the wastegate referenced to? If it's the turbine itself.....your lack of boost is the FMIC. Reference needs to be AFTER the intercooler when running a rear-mount setup.

Also, ....have you checked the little things....like making sure there's not a kink in the boost gauge line?

Good luck.

Silver_TransAm

iTrader: (2)

The wastegate reference is from the output right on the compressor side of the turbo. That could be why I will check that tomorrrow. Thanks stay tuned.

Silver_TransAm

iTrader: (2)

where should the reference be at? Manifold or right before throttlebody?

veee8

iTrader: (40)

Before throttle body. Manifold has vacuum as well as boost. Some turbos have a fitting on the housing itself for this.

Silver_TransAm

iTrader: (2)

it is running off the housing right now.

Silver_TransAm

iTrader: (2)

Thanks that did it but still not making more than a pound in 1 first gear. In the upper gears at speed it pulls 4 to 5 psi. Thinking exhaust wrap or smaller housing on the exhaust side. Any suggestions?

hellbents10

iTrader: (10)

Those turbos are not the correct size for making only 5psi and less then 450whp. Its going to be very laggy. You might have to drop down as far as a .58 hot side to make boost soon enough at lower power levels.

Silver_TransAm

iTrader: (2)

My dad wants to know how much difference wraping the exhaust would help? Will boost hit sooner and by how much rpm? The truck has headers wondering if going back to stock manifolds will make a noticable difference on the truck like the cars do or should he put smaller exhaust housing? Any input suggestions or experiances would help, Thanks.

Schantin

iTrader: (6)

Yep, if you have LT's, wrapping the exhaust will help. Probably dop the "lag curve" about 400-500RPM. I can make about 3lbs in 1st gear, and 5PSI 2nd-6th gear. 3rd gear and up I'm hittin full boost by 2400-2700RPM. Exhaust is wrapped from converters back. LT's are ceramic coated Will probably take 2 50' rolls. My $0.02......wet the wrp before putting it on the car. It'll wrap better. Also wear gloves, as the fiberglass (or whatever gives it the heat resistance) will make your hands itch from handling it. Finally, spray the wrapped exhaust with DEI or similiar exhaust wrap paint. Seals the whole deal pretty well

BTW, from what I've heard going back to stock manifolds makes a big difference (less surface area). Unfortunately my wife threw my stock manifolds/ y-pipe away while I was in Iraq so I can't speak from experience........

Silver_TransAm

iTrader: (2)

Wraped the exhaust from the turbos forward about 3 feet. Also we put the stock headers back in, and will test drive tomorrow to see what the results will be. The manifold question will be answered!