Greddy guru's..need help...have a question
 

Ok so I have a built engine with the greddy kit running 509rwhp on high and 439rwhp on low boost...not very relevant but I'm running a decent amount of boost on my built engine.

When I got my car back from Sam at GTM it ran perfect...nothing wrong at all.

Fast forward about 5 months later since the retune.

Occasionally while driving I'll decide to downshift to get my rpms up (between 3k rpms-4k rpms) and when I do so my car will sound like it's hitting fuel cut. It sounds like a rapid backfire sound and my car stays put and won't accelerate at all until I let off the gas first. On other occasions I'll be going WOT for the entire gear and shift into the next gear and it will do the same...It will stutter and won't let me accelerate til I let off the gas again. I'm not a genious but it sounds almost like it's running really rich and won't accelerate. But it's odd since it's recently started doing this and my old tune never did this either. I had my car checked out by Sam a month ago and he noticed it too but said it's probably due to the E-manage Ultimate not being very good at tuning such incremental rpm's.

Anyway's it really irritates me that my car does this sort of hiccup because I've paid lots of $ and I think it's fair to expect a better engine than stock.

If you guys have any suggestions or advice please let me know. If Sam can't figure it out then I don't know what to do.

Thanks a lot,

-Anthony

hmmm.. almost sound like my story i think. read my store its tittled "Need help APS ST"

If i'm not mistaken u r running lean on a certain rpm... and not rich how ever i have a question do u have wideband on ur car?

What EMS are you running?

Wideband?

Running E-Manage Ultimate. I know it's not great but it's what I got.

Yes I have a wideband on the car but it's hard to read when i'm accelerating so fast at WOT...I suppose I can have my gf read it for me.

find an long open road and do a 4th or 5th gear pull. Or get it on a dyno and have it retuned

So you think it has to do directly with the tuning?
It's weird that it does it at different rpms though...it's not always a preset rpm that stutters...and it doesn't stutter ALL the time just sometimes.

The problem with the dyno tune is that it will run fine on the dyno but you can't simulate real life downshifts on the dyno...and the fact that it's a good $500 dyno. I know the emanage ultimate isn't great but I would imagine it could make my car run smoothly enough to not hiccup.

Thanks,

-Anthony

Mine is doing almost the exact same thing. I have a built motor and greddy kit also with the same high boost power as you. I had to have my turbos rebuilt and I just put the motor back in the car last week. It was running fine until later that day when all of a sudden it would build boost then all of a sudden stop building and the car would run really rich and backfire and just basiclly run like complete crap. I have a good tune and am using a Utec. I am going to do a boost leak test and see if maybe a pipe or clamp has come off

Also, if i watch my boost gauge and keep it out of boost it will run fine and i can run it to redline. It only acts up when i get into boost.

EDIT: Forgot to add that yesturday the car was idling at 1500 rpms with the A/C OFF. WTF!!??

So even with the rebuilt turbo's it's doing this backfire thing?

It's odd how it never happened and all of a sudden it happened one day coming back from a car show. It's weird how it only happens sometimes though which leads to me not believe it's a boost leak...I think we have the same problem kuz it does sound like sh!t when it happens. I'm sure it can be a lot of different things but I'm not sure where to even look. Keep me updated and let me know how you plan on checking for leaks. Also, what BOV are you using?

So I took it out yesterday and today and checked the A/F gauge while doing so. A/F is pretty steady through 4th gear at around 10-10.6.
It seems to wind through gears without hesitation but it's when I downshift or upshift fast that makes it backfire or sound like it's hitting the rev limiter.

If I try to downshift into 2nd gear at about 3.5k rpms like I did today, it makes that backfire sound and doesn't let the car move until I let off the gas..and then I shift up a gear to prevent it from happening again.

I then took 2nd gear to 6.4k rpms and shifted into 3rd to keep accelerating and it did it again until I let off the gas. It seems like it's dumping way too much fuel or something.

I hope someone can help me out here. I'd hate to spend more money on the tune and better EMS if it's going to do the same thing. I'd hate to spend $3500 on the V-Pro just so it doesn't do it anymore...

-Anthony

What do the AFR's look like when you are shifting then accelerating. This part is going to be very hard to watch and it would be best if you can log it on a laptop.

My car did the same when I had EU, it stopped when I went to a UTEC.

What engine management system? Have you talked to Sam? If not, I would give him a call, and I sure he can help.

Dave:
I have not. Like you mentioned, it's very hard for me or my passenger to get a good reading when I shift because it happens so fast.

Eagle:
That's very interesting...did yours do the same thing when downshifting as well? I noticed the EU isn't very smooth either when half-throttling the gas and letting off the gas sometimes. Can you send me your impressions of before and after the UTEC? That would be extremely helpful since the V-Pro would cost me over $3,500

Sharif:
I have talked to Sam like last month when he tried diagnosing it and said he tried messing with the EU for those spots but he said he kept going back and forth messing with each cell trying to correct it. He mentioned the 16-bit EU being obviously inferior to the V-Pro and recommended I upgrade. I know Sam knows his stuff but the only thing that I don't understand is how this can just change over time...because it never did this when I first got it tuned.

Stick with Sam. If anyone has the answers it will be him. Stick to one vendor. Asking opionions of different people will likely get you into more trouble.

JET

Anthony,

Don't worry it shouldnt be very hard to figure out the problem, bring the car in so we can run some diagnostic tests and find out what is going on with the car. On a side note on your last visit to us this problem did not exist, as I told you at the time there was a small rich spot I was trying to take car that I noticed on the A/F gauge but it was very minor and not really noticible as far as driveability. What ever you are expeirancing now something must have changed since then. I don't think its a tuning issue/re-tune. A tune will not change on its own unless something mechanical changes with the car such as exccesive(or lack of) fuel presure, sensor malfunction(cam,crank,o2, etc.) Keep in mind that you are running a piggy back and the factory ECU is still running the car. Any reaction from the facory ECU good or bad will change the outcome of the driveability.

sam

GT Motorsports

Well I fixed mine. Not exactly sure what the cause was, but I took down the Utec and unconnected and then reconnected everything making sure it was all tight and the car is back to normal. Also fixed a manifold leak I had caused by my AAM fuel rails contacting the lower plenum and not letting it be able to tighten down all the way.

Best of luck and hope you figure it out.

Cool. I'll give you a call in the next few days Sam. It seems to have gotten worse now and I'm not sure why but I'll deff give you a call.

Thanks,

-Anthony

Ok so no fix. Left the car at GT for a week and Sam couldn't replicate the problem...but now I drove it home and drove it around town and it's getting worse. It seems like everytime I upshift after WOT in the gear it does it... Example: I'll be going WOT in 2nd gear and shift into 3rd gear (slow or FAST shifting) and it will stutter and not let me accelerate for a second and make a backfire sound. Sam didn't charge me to look at my car and I thank him for that but this leaves me at square 1 again. I don't really wanna take it elsewhere either. I'm not sure what to do at this point or what the hell the problem is in the first place. I really don't think it's the tune because the car didn't start doing this 'til a couple months ago.

Now that I think of it I did have 2 coils go out on me when I first got the Emanage Ultimate and it did something SLIGHTLY similar until the coil finally blew and the car was running on 5 cylinders.

I suppose I could upgrade to the VPRO but I have a strong feeling that won't solve my current problem.

Someone help me out with suggestions please?

Thanks,

-Anthony