MR1JZ

Greetings from Australia!

I run an Evo 7 RS over here and we have recently switched the motor out for a built 2.3L after the old built 2L gave up the ghost a few months ago

Basic specs are as follows:

High compression 2.3L (9.8:1)
Mild head porting
Kelford 272 degree cams
GTPumps 792 Turbo with FP Stainless rear housing and Turbosmart 40mm external gate

The GTpumps 792 is a proven performer on evo's here, unfortunately I am the first person here to try it on a 2.3 with the FP housing though, a mate has tried it with a 2.55L and it made 380+ KW at the wheels

Basically the issue we are having is the turbo is very very lazy, takes ages to spool, we dont see usable power until 5K RPM which isnt really suitable or right for a high compression stroker.

Not to mention the peak power is only 302kw, which is way too low for this setup.

Dyno sheet here:



My question is where do we start looking to find this issue? Could it be a wastegate issue? The fabricator who made the screamer and dump pipe is adamant he installed the gate correctly with the ring to seal.

Any help would be appreciated!

LetsGetThisDone

iTrader: (1)

You should expect about 500rpm slower spool up and slower transient response with the single scroll housing vs a twin scroll MHI housing.

MR1JZ

Yeah I gather it will be a little bit laggier but that laggy with what I consider to be **** all top end something else is the contributing factor surely?

MR1JZ

A couple of people have suggested cam timing could be out...possible?

LetsGetThisDone

iTrader: (1)

I'm not familiar with the gt792. What size is the compressor?

Part of the issues could he you're using a turbo smart 40mm gate on a tial 38mm flange.

Which line on the graph is boost?

Erik@MIL.SPEC

iTrader: (94)

IIRC, the GT Pumps bigger turbo spooled like an FP Black and put down power like a Red. By adding the single scroll housing you're only making that worse. So you turned 4500rpm spool up into 5000 spool up.

I think that actually makes sense and lines up with what I've seen (which isn't a lot for those GT Pumps turbos).

http://www.gtpumps.com.au/

Also looks like you're not really pushing the turbo too much...~26 or 27psi

TheBoz

iTrader: (9)

Did you check all the basics.


Boost leak test
Compression test
Timing Sync - make sure 0* on the computer is 0* on the motor.
Check Timing belt to make sure all timing marks are on point.
AFR's
Timing numbers
Fuel type


More info, but check the basics first.

LetsGetThisDone

iTrader: (1)

Also, does GTP use the same turbine as FP? If they're not the same size, you're killing performance.

MR1JZ

Rear wheel is identical.

Have checked for boost leaks and found nothing.

Engine builder is 100% confident cam timing is correct

Motor was blueprinted at 9.8:1 compression, adding more boost does nothing to the peak power figure, we might have narrowed it down to a restriction in the exhaust, back on dyno next week with a straight pipe to see if that makes a difference. Will post here with the results.

MR1JZ

Not pushing the turbo yet because more boost does nothing to improve peak power, after actually giving the car a proper run on the road it feels very usable for what i want to do with it (circuit racing)

Hopefully the exhaust makes a difference, if it does I will get busy making a 4" exhaust

LetsGetThisDone

iTrader: (1)

You should not need a 4" exhaust. This is my car on an FP red with a 3 exhaust on an O2 dump. MHI twin scroll turbine housing. Something else is wrong with your car unless you had a broken muffler or collapsed catalytic converter.

MR1JZ

If it is the rear muffler restricting it then the straight pipe will resolve it but make it undrivable on the road

This is how loud it is with the muffler on the back


The idea behind a 4" exhaust would be to keep it quiet(er) whilst maintaining good exhaust flow

LetsGetThisDone

iTrader: (1)

My car has a 3" exhaust that was quite quiet until I took it to a track day lol. It has a large magnaflow muffler at the back of the car, and a resonated test pipe.
Keeping a 4" exhaust quiet is going to he hard.

Erik@MIL.SPEC

iTrader: (94)

It's been shown by lots of different testing that even a 3.5" exhaust isn't needed unless you're running super-high hp (800+).

I only mentioned boost because you had said it only made xxx hp...and most all of the stock-based turbos need lots of pressure to make good power.

Like I said before, I know those GTPumps turbos are popular in AUS and NZ, but all the plots I've seen show FP Red power with FP Black spool...and that's with an MHI housing. You have a SS housing on there which makes everything worse (spool wise).

I think a ported MHI housing would help eliminate some of your issues.

Good luck and I hope you find the issue (although I think it's the turbo).

MR1JZ

I would have liked to have gone FP red but two factors put me off

1. Cost (the usd is horrible against the AUD at the moment) A borg warner would have cost me about the same
2. Local support for the GTP, I have been able to speak to Mark about these issues over the phone, not a luxury I would have really had with an FP turbo