t25 turbo info

[marcrx5]

I hooked up my mbc on my 240sx, and set it to 14psi. The problem is at higher rpm the boost starts to fall off. I can hold 14 psi at 3500rpm all day, but at 5500rpm, it's down to about 11psi, and by redline I'm at 10psi. I was on a NICO forum searching threw old threads, and some people say the t25 can put out 14psi, others say it's too small to hold it to redline. Anybody know for sure? Also, could it have to do with our altitude? I'm about to swap out turbos, but I want to make sure there are no other problems before I do. If I get time this weekend, maybe I'll pressure check the intake just to make sure.

[HONDA GHANDI]

That sounds about normal for that motor. You have to understand that at the engines natural torque peak it will make most of its power and after that the combustion event is much shorter actually making exhaust temps fall. This in turn will drop a turbo out of its efficiency range. The 240 makes good torque down low but is choked a bit at higher revs in my experience. A larger turbo or turbine housing/wheel can help but at the cost of lag.

[Skaterkid]

The turbo on my car (about the same size as a T-25) will spike to 15 at about 3500 then fall to 10 psi and hold it to the redline. The T-25 is just too small to make 14 psi of boost at this altitude. Go down to sea level and it should hold 14 psi.

[S15SiLVia]

The T25 reaches its limits at around 12-14 psi, anymore it loses efficiency. Is this a T-25 off a red/blacktop Sr20? If you plan to go any higher, you'll need to be upgrading the turbo.

[john]

The t25 is a pretty small turbocharger, and just can't flow enough to maintain boost. Same problem on the 2g DSMs.

[STIBungy]

Consider the displacement of the motor the turbo is feeding air to. That's a big motor for such a small turbo.

[PowerSportsInc]

T-too small
;)

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[B16crxTurbo]

You may also look at your exhaust set up, depending on how free or not free flowing your exhaust is, you may be losing some boost pressure because the exhaust can't get out of the engine fast enough.

I would say otherwise, it sounds about right.

[john]

I think that's incorrect. If there's an exhaust bottleneck, the intake manifold pressure would be higher due to the inability of the head to consume what's being pushed at it.

[marcrx5]

My exhaust it 3in all the way back (except cat right now). I was thinking that, but I wanted all my problems fixed before I swap turbos. I have a gt2540 that will hopefully go on next week, so I don't care that this turbo can't put out any more power. Thanks for all the feed back, and I'll keep you guys updated on the project.