Engine/Transmission (1994 - 1998) Too much back pressure = low power

[BLujan]

Well I got to dyno my truck today at WINspeeds/BRG Dyno day, I was glad to finally meet some of you guys.

I was pretty by my dyno numbers 306/715. I am just straight piped for now with the stock 3 inch and i think that may have caused a problem.

As soon as we started the dyno run Adam noticed black smoke under my hood. I watched the gauges, Egt's were plasma torch hot, and my boost was down to 40 LBS. from 44. The HX-35 stayed together but it did leak exhaust from the ex. housing to manifold flange and where the turbo slips into the ex. housing.

I have never had this problem up until the dyno runs. I heard from some watchers that I had just as much smoke up front as I did out of the tailpipe. Do you think this much fuel and only 3 inch ex. created enough backpressure to leak exhaust out of these areas?

Oh, well I guess I just have to 5" to free some HP before I get a turbo, DARN!!! :-laf

Brett

 

[TReed]

I did a 309/707 with completely stock turbo and housing, #6 plate and DD2's with 4'' exhaust with 5'' stacks and no other mods. It's an Auto truck also.

 

[bmoeller]

Did you gut/remove the cat? Could be plugged.

 

[BLujan]

Yes, the cat and muffler are both gone. I know I have way too much fuel for the HX35, but that just makes it more fun to drive. Backpressure is the only thing I can come up with that would have created the exhaust leaks. I'll try some exhaust and get it back on the rollers.

Brett

 

[ChillyDog]

IMO you are not going to gain much if anything by going to a bigger exhaust because you are still going to be trying to cram all that super heated air through the stock turbo. Your main restriction is the turbo, not the exhaust. With the fueling you have you might as well bite the bullet and buy a bigger turbo. I was at 427hp/1020trq on the stock turbo but it finally caught up to me a few weeks ago when I blew the head gasket.