the subject says it all, only under boost (not when revving and not before 4psi of boost). i get a chattering like the turbine is hitting the housing, pending a check of the turbo for play in the wheel any other suggestions? the turbo is probably baked since i had low oil pressure for a day.

 

What octane fuel are you running?


-Ted

 

Sounds like it could be a small case of the detonations.

 

yeah... if it is a rapid "chattering" that could definately be detonation, that is the word that came to mind when I had it.

 

So you have an intake and exhaust with no real fuel mods besides the s-afc? Even with your injectors set to 100% duty I don't think that will be enough fuel. Plus its bad on the injectors.

 

did you re-wire your fuel pump? it is the best bang-for-buck fuel mod you can do. i strongly reccomend you do it. it's not hard at all. if you can hook up an amp, you can do it.

 

ive got a 3g pump in. if i was detonating this much i woulda spent the motor by now hands down.

 

Not true...my car used to detonate all the time, and my engine is still alive. It turned out to be oxygenated fuel that was the main culprit. Now that I took my FCD off, adjusted my new TPS properly, never run oxygenated gas, and had my timing adjusted, detonation is pretty much a distant memory.

 

so we thinkin tps adjustment and define oxygenated gas.. im running 93 octane. (in the midwest tho so its got ethynol)

 

That's oxygenated gas.

 

i havent had a problem with this stuff until recently

 

How do the spark plugs look?

 

just put in new ones, if my timing was already retarded and it retarsd under boost even more would that cause more detonation?

 

Can someone that had first-hand experience with both fuel-cut AND detonation please define their differences ?

I'm hitting way too much boost right now, so I'm using 99+ Oct fuel to prevent detonation, and taking it easy on the gas pedal, until I can install FD pump and S-AFC. However, when on the highway and in 5th, I encountered what can be described as "hickups", very light, just enough to notice them, 4 or 5 times. Thing is, these did not happen under full boost, but rather when in half-throttle or while deccelerating.

Anyone has a definite answer ?

 

The engine doesn't really buck during detonation like it does during fuel cut...it just has no power.

 

fuel cut is a HUGE buck (twice as bad as the notorious first gear tps sensor going bad buck) after you hit 6.8 or 8.6 psi (depending on years). detonation sounds more like a valve going on a V motor. it clatters alot and u have no power.

 

Retarded how much?&nbsp Excessive retarded ignition timing will allow fuel to burn in the exhaust pipes and sounds very close to detonation.&nbsp There is no reason to be retarding the ignition - the stock ingition maps are already pretty conservative - you might be doing more harm than good.&nbsp Put the ignition timing back to "stock" and see if this changes things...


-Ted

 

Get an AFR and/or EGT gauge - that should give you the answer.
It might be you're running too much fuel - this will cause these "hiccups".


-Ted

 

ok gu ys i hear what yer sayin, the problem is i didnt have a timing light to set the timing after the front cover job from the s4->s5 conversion, i have since fixed the problem and am flyin all the way to 18psi of boost =) thanks for the input tho. ill have dyno numbers up soon.