Yet another High boost misfire question

[BlownZ]

Misfires above 20 psi

Bear with me...I have searched the archives, I have cured this problem 12 times. I think I know the answer...I would like your expert opinions.

Te61 Turbo set on KILL Wastegate ROD all the way In
100 Octane Unleaded
MSD 50lb injectors
Jim Testa Street Chip for 50s 19 deg. Timing I think
Ported Irons
Ported Manifold
Ruggles 210/205 cam
RJC Plate
Headers
Fuel Pressure set from 43-48 no change in problem
New Coil/Module
Checked Grounds and Positive and Neg cables...all good.
New R42 TS gapped at .035

Car runs like a raped ape....UNTIL you hit about 20-22 lbs of boost. Then it stutters, misfires, pops, farts etc.

O2s at this point from .780-.812
MAF seems to be locked at 254 as the scanmaster reads that reading from about 10lbs on up.
TPS .42 idle...4.2 WOT

Here is my theory....Is it possible that the street chip simply does not fuel the car enough to maintain boost levels this high? I get a little knock but nothing serious and the O2s are fine but at WOT they are only so good. I am curious if this chip is capable of supplying enough fuel to match the flow potential? How can I check to see if my injectors are maxed out. I had a similar problem with my 009s however that misfire was at 15lbs...I changed the coil and module at that time and misfire went away.

When the misfire went away I changed to 50s and started cranking the boost. I am going to turn the boost back down to a normal street level of 17-18 lbs and the car should run fine...it seems to only do it at the 20lb mark. Would a race chip allow me to run higher boost than this or do I need to go to an even larger set of injectors?

I have read several posts concerning MAF dropout and the Translator fixing this but if mine is locked at 254 then my misfire wouldn't be dropout would it?

Thanks in advance for your help. I know my post is long but I wanted to give all the information I could think of to save everyone from offering suggestions based on not enough information. Thanks.

 

[Intercooler]

Direct Scan will show your injector duty cycle. An EGT will help you more than an O2 in trying to tune it. I learned all about the O2 vs. an EGT up close and personal about a week ago.....get the EGT. You for sure need to know what fueling is in the chip. Good possibility the fuel in the street chip isn't enough to run 20+ PSI. I got tired of playing the chip game (poke and hope) so I switched over to a Max-Effort 16 position. By far one of the best changes I made!


BTW...I didn't see a pump listed but have you done a WOT FP test to see if it is dropping off in third gear?

 

[Joe Tiano]

my guess... is the 210-205 ruggles cam& lifters are going south....how many miles on that cam?

 

[BlownZ]

Pump is a Walbro 340 hotwired.

Camshaft has approximately 20k miles on it. Valvesprings have also been replaced. The car runs MINT at no boost, and boost up to the 21-23 psi range...I would think a bad cam would show itself elsewhere in the RPM range however I certainly do not profess to be a Turbo Buick expert. This is my first TR and I have only owned it for about a month. Rock solid vacuum readings as well.

I have not done a fuel pressure test...I don't have a gauge with a long enough hose. I am going to try and find a hose today to eliminate that possibility but I don't expect that to be the case. I would think that I would record spark knock out the Wazoo if my FP didn't rise with boost even at the 10psi mark but I don't. I barely get any knock at the 21psi mark when the misfire occurs. Fuel Filter is a week or two old.

I am leaning toward the chip. I don't think there is anything wrong with it but simply that I am asking too much of it maybe? I wonder if it simply does not have enough timing to allow 20 plus psi boost? I have installed a new 30 psi boost gauge and I am suspect of it. It shows zero boost when the stock gauge shows 4 psi. Yes I know the stocker is junk BUT the stocker matched my old gauge perfectly and even when the new gauge is showing zero..I can feel the boost...it has that very distinct sound and the engine is picking up and the car is starting to run strong...so I think the stocker is right and the aftermarket gauge is reading low. If this stays the same throughout the RPM range then my problem isn't at 20-21 psi...it would be at 24-25 psi which might change my entire problem. The gauge is an AutoMeter ultralight vacuum/boost combo up to 30 psi.

I have a race chip in the mail to see if timing is my issue and if the problem goes away then I have my answer. I do plan on changing to something like a ME chip, I was actually planning on a T-Plus with an Extender, I already have an LS1 MAF sensor. I just want to get it to run right as is before I modify it even further.

Anyone else have an opinion? I think Direct Scan is going to be the next purchase as this Scanmaster just only shows you so much, I would like to be able to log the files for review at a later time too.

 

[Chuck Leeper]

GAP??

You stated:
New R42 TS gapped at .035

IMO, U R about .003 to .005 too wide on the plug gap....BTDT

I don't think 100 octane is gonna get it at 22-25# boost. Especially w/ a street chip.
I'd suggest if you are going to run boost levels that high, the the chip be a race chip w/ the race timing and fueling in it...

My $.02 worth.. Back under my rock...

 

[BlownZ]

Chuck your suspects are mine too. I am going to regap the plugs when I get some time but I really think my culprit is simply not enough timing to run 20 plus psi. As little effort as it takes to regap though I would be silly not to at least try it.

I don't think octane is my issue as I normally don't see much KR when the misfiring occurs. It will knock sometimes when it happens and sometimes it does not. Usually when it does it is only 2-4 degrees...nothing dramatic.

I have a race chip in the mail that should show up tomorrow with 26* timing. I will try that. I just turned the boost down to 18 a few minutes ago and the car runs mint. No misfire, no knock, just speed.

If my MAF is indeed locked at 254 then this issue isn't MAF dropout is that correct? Keep it coming guys...I will take all the free advice I can get.