Turbo help!

[MichaelB2009]

I have a 5.1L stroker with a 78mm/.96 comp oil-less turbo. Went to the Dyno yesterday and I can't get the power up where it should be. The power falls off early. When the boost is increased above 14.5 psi, it misfires and the power drops off. The tuner thinks the 3" in and out on the exhaust side of the turbo is limiting the motor and causing too much back pressure. I do not have info on the cams as they were in the car when purchased, only info is stamped on them v310 000 on passenger side and v315 055 drivers side. Car is on e85 with 1600s probe industries pistons and scat crank. Car is super fun to drive but I feel like I am leaving some meat on the bone. Has anyone had an issue with this size exhaust piping at power levels 800+? Has anyone had this issue with cams? I'm lost here. Does the exhaust housing need to be larger?

 

[Hollowdweller]

I have no advice to give but hoping to here fix. Hoping to hit the 650 mark with my setup, maybe a future problem for me. Just to throw something out…my 1st thought went to spark blow out.

 

[MichaelB2009]

I know a lot of people run the hot side discharge out the fender. I really don't want to do this, as I am 43 years old and like to drive the car to work on nice days. I was really hoping to get some feedback as maybe someone had an issue with the three inch piping or someone to say, "I have 3" in/out with no issues" so I know with those numbers, I just need a cam change. Who knows, maybe this is an odd one. My plug gap is at .026, I would think that is good, but if the back pressure is too high on the cylinders, I know it will cause the same issues. I will figure it out hopefully.

 

[MrBhp]

How is your intake air routing/size? I'm sure your tuner knows better than me, but I've had the same issues with maf/undersized inlet piping.

 

[MichaelB2009]

Intake is all 3". I had an hpx, he had me install a hpx-e so I wasn't limited there.

 

[MichaelB2009]

I could go to .020 on plug gap and get some better coils maybe, and I'm thinking about an exhaust cutout on the exhaust leaving the turbo to help with flow.

 

[Pentalab]

On paper, .026" + 14.5 psi should really work. You could always try .020" to .024" and see if misfires vanish...just to rule out gap spacing issues. I'm assuming your plugs are 1 heat range colder ?

 

[07 Boss]

And depending on what plugs you are using we used to side gap the plugs to better expose the spark. This sometimes helps with misfiring.

 

[MichaelB2009]

They are 1 step colder. Znar7aix. Any recommendations for better coils? This is coil on plug.

 

[stkjock]

stick with OEM coils IMO, my car has made 900+whp w/ stock coils 24# and E85