Turbo question

[nb07bcar]

I have a th04-15G turbo and I can't get the car over 5000rpm in 4th gear and 4500 rpm in 5th gear. No speed limiter. I have a 91 ka with sacf2, 460cc injectors, z32 maf, msd fuel pump, 3/8 aluminum fuel line to a custom fuel rail, front mount intercooler, msd btm retarding .5* psi. It just seems to run out of steam at those rpm. I'm at 10psi and afr is at 12 and it doesn't go anywhere. here is the turbo map of the 15G and a map of the turbo I think I might upgrade to 19T. maybe the turbo can't supply enough air?What do you guy think?

[fiznat]

Does it just run out of steam there, or does it run rough and jerk a little bit? Any popping or smoke that you can see? How much boost are you pushing?

[nb07bcar]

No poping, no smoke, it just run flat. 10psi.

[fiznat]

Is there no trouble at all winding the car out in 1st, 2nd and 3rd gears?

[nb07bcar]

1st and second gear I can run out just fine. But I only get up to 10 psi for a very short time. 3rd gear it takes awile nad it seems like I run out of power by 5500 so I shift to 4th and it takes off again.

[nb07bcar]

DO you think it might be the turbo! The maps for the 19T is a better map, but is it that much better?

[KATwo40]

I think it's turbo time for you, my friend.

Do yourself a favor and don't buy a used unit. They just suck.

What are your power goals? What type of torque line do you want to see?

The 19T looks better than the 15G for sure, but I think if I were going to buy a new turbo, I'd consider more options. You might go with the notorious T3/T04E .50 trim for the best efficiency. But, then again, it may be larger than you want.

[Nismo_Freak]

1st and second gear I can run out just fine. But I only get up to 10 psi for a very short time. 3rd gear it takes awile nad it seems like I run out of power by 5500 so I shift to 4th and it takes off again.

Sounds like you are overspinning the compressor. That will produce a ton of backpressure as well and it will make the engine gain revs very slowly. Boost pressure should also be dropping off, and you might even hear the compressor start to stall.

[KATwo40]

I duuno about overspinning. Look at the max airflow of that compressor. It's way over his peak air consumption. I just think it's a turd and it's time to replace it.

[KATwo40]

Yeah, could be a leak...I like how you thought of that. But then again, he does say that the AFR remains at 12:1, which wouldn't really be indicitave of a boost leak, right?

[Nismo_Freak]

I really dislike Mitsubishi. Their turbos, their cars, everything they do is screwy in some shape or form.

GT28RS for comparison.

[Nismo_Freak]

Sounds like a bad turbo to me.

[KATwo40]

I really dislike Mitsubishi. Their turbos, their cars, everything they do is screwy in some shape or form.

Agreed. I used to be a Mitsubishi Svc. Mgr...

[Nismo_Freak]

Agreed. I used to be a Mitsubishi Svc. Mgr...

I would have hung myself.

I had to work on Ford parts when I was at Mazda...

[nb07bcar]

The reason why I go with mitsubishi is because they come off volvo's and I can get them for real cheap. I.E. free most of the time. The 19-T will bolt on directly to the setup I have. no changing lines and all. My power goals are 250-300. I think I have everything to support that except the turbo. I would go with another turbo but it would cost me a couple of hundred which I don't have. but thanks for the input.