backfire/overboost question

[brokencpsd95tsi]

I had my car on the high boost setting today (have two stage mbc) Whenever I gave her a little gas she backfired and it was followed by a small bit of black smoke :thumbdown . Later I went for a med-throttle 5th gear run to see what boost my car was trying to hit and it was gonna try to go over 20 psi ..............

basically the question is......did I fvck something up overboosting? Or should I not be worried because I turned it down some now.

car still runs fine and all on low setting with no smoke.........

 

[91orangeGST]

we should hope not , but it very well could have. I did the same on my 91 gst and blew my head gasket, but after replaceing that and a few valves i just learned that I lost 100 psi in my number 2 cylinder! Mine went up to 25! If it isnt smoking at a low boost everything should be fine, but get a compression test on it first thing. All the cylinders shouldnt be more than 10-15 psi off! If so you have a problem! Go to a local Autozone and you can get a compression tester for $25. When you do your compression test take out all of teh spark plugs and let it turn over 4 times. You can tell every time it turns over by the jump of the needle. Good luck and post what the results are!
P.S. If the compression comes back low in one cylinder dab a little bit of oil in the spark plug hole and retry. If it goes up it means that you have a bad ring and if that is so you can run synthetic oil and it should regain compression because it is much thicker! Im running 60w in mine and its doing good! so good luck!

Kyle,

 

[FASTSPOOLINGST]

sounds like your running rich and when you are doing high rpm runs, the unspent fuel is igniting in the exhaust giving you a big ole' flame out the tail pipe.

My car did that when i had a 255 pump and no regulator when i was racing a corvette on a 50-100 pull on the interstate. .... I thought i threw a rod when it backfired.

I didn't check your mods, so i don't know what fuel set up you have. but if it's a 255, i would recommend getting a regulator to keep it stable and not overtake the stocker.

 

[brokencpsd95tsi]

well....i'm running the stock fuel system still.....

my dad (mechanic) said if it was a ring I would still be smoking... but it seems to do ok at low boost unless I get the engine real good and hot and heatsoak the intercooler then I get a little stuttering once the turbo hits full boost.

I had the stuttering problem at high boost a few weeks ago...replaced the fuel filter and turned the boost down to about 17psi and it seemed to be doing fine......

yesterday hauling azz home from work took the offramp turned off and gave her some gas at low boost and I had a little bit of the stuttering problem......

 

[FASTSPOOLINGST]

take off a piece of your UICP and see how much oil deposits are inside. Your turbo at fool boost may be flowing oil into your combustion chamber via the intake etc. Causing you only to smoke at full boost.

Basically, it could be a lot of things. You will have to start somewhere and use the process of elimination.

If you think maybe rings are bad, do a compression check on it and post the results. It may be valve seals going bad.

 

[brokencpsd95tsi]

turns out everything is ok..........

turned the boost at high boost down.......
good compression
no oil in uicp

car runnin fine......


I had turned my car down a bit at the track......then the other day before I took a friend of mine for a ride I turned it back up just a little (what I thought was just a little)....so I just basically overboosted for a sec and hit fuel cut.

cars all good and will be runnin mid to high 13's next weekend.......