Hey everyone. I sometimes get a fuel cut or something when I hit about 6500 to 7000 RPM especially in 2nd gear going WOT. This especially happens when the car is relatively cold but it has also occured when the car is warmed up.

i remember when it happened first and get a loud bang from the exhaust (the kind when you get a fuel cut on a dyno), lurched a little bit (i think because the engine power is gone momentarily), and I got a check engine code. The funny thing was the code went away after a couple of days. Now when it happens, you hear a loud bang but the car kinda lurches more violently (I dont think it's the differential or clutch), stays dead for a slit second, and then when I get it back into gear it becomes alive again.

Another thing (but not too sure if it is associated) is when I am going 80-90 and boosting to 1 Bar (I use Defi BF), I can hear kind of a low freq knock sound that is consistent but goes away when I lay off boost. I added an MBC (for when I get Exede later) and I've turned down boost a litle bit. I would hit max about 24 PSI (1.5 BAR). The sound is always consistent under these conditions. Should I be worried? Thanks guys.

 

Sounds like detonation to me due to you boosting 24psi. ON pump?

 

Yes. Detonation? Give me the bad news first.

 

The BANG sounds like boost cut. But you won't know for sure until you look at the code (before it goes away, that is). And 25psi with the MBC is pushing it on 91oct. The ticking you hear at 1bar of boost doesn't sound to me like detonation. It is most likely the boost control solenoid ticking away. If you're unsure about the sounds and what they could be, pay a visit to Tuning Tech and have them take a listen.

shiv

 

Detonation goesn't go BANG. It's not detonation.

 

Thanks Shiv! Actually, it doesn't bang when it happens, it makes no real noise, it sounds like the engine gets stuck ( I remember I got popped out of gear once, isnt that strange?), then I would have to put it in gear to get the car going. I'm more worried about the sound I get when hitting 1 bar....its sounds like you were going over cracks in the pavement at high speed and when I let go of boost it stops. The popping outta gear happened just once...maybe more but I really didnt notice it. The code did pop up intially but no longer does. No codes pop up when it happens.

Laslty, not to sure if this helps any, but nowadays when I go WOT, it doesn't "sound smooth" like it used to but a litle more rough. I can't describe it any other way.

So to summarize:

fuel cut: loud bang or fiorecracker noise
boost cut: my situation?
detonation: no bang...but can still be my situation?


Thanks again everyone for your input (fingers crossed)

 

lower your boost to 21 psi and get a custom flash.... no need for you to be running 25psi on pump not even on meth or race gas...

 

To be honest, it sounds like something is mechanically loose. I'd have it looked at by Tuning Technologies. It's not something I've heard described before so trying to troubleshoot it on-line is unlikely to be successful.

Shiv

 

looks like I will dial down the MBC...hopefully the noise will go away. Flash is indeed custom...Xflash.

 

what boost where u flashed at? ...best to stick with that ...remember car was tuned for that boost...that airflow...the added boost may hurt you more than help...

 

That's a good question. i would assume it would be at 21-22. I didn't think 24 would be all that bad since people have been posting on EvoM that they boost to that level without problems.

 

you can boost to that level...but you weren't flashed to that level...and there is a reason.... crappy gas + 24/25psi = detonation, poor performance...possibly a lean condition...it may feel good for a second...but the ecu will do it's thing and compensate...by dumping fuel or cutting boost...slap in an alky kit and go back and get flashed at 23/24psi ...you'll be happy as a pig in ... u know the rest

 

thanks ryder! By the way, detonation is permanent damage to the engine? Sorry for the newb questions.

 

Detonation can cause permanent damage. But it needs to be relatively serious to do so. Never a good idea to push your luck though...

shiv

 

please dont boost 24 lbs on 91.. its not good for your health.