[Z Ferrari]

Heres the deal, I got my a/f gauge in and it shows im runnin all the way rich in boost, but I am detonating in third gear + at 4k rpm up. It does it when i run 6psi or more. I Dont know why, i put in a new fuel filter that was clogged really badly but that didn't help much.
I always thought detonatoin meant running lean, but my a/f gauge shows its actually running fairly rich. what else could be my problem? thanks


Scott

 

[mylesm]

could be.....

Things that effect detonation are


spark timming (if it's too advanced, you could cause detonation)
Fuel (lower octanes blow easier....)
Air temp (if your air is too hot, it will blow)


Also.. A clogged exhaste will do it too

so Make sure your timming is set to 20 BTD with the TPS in the idle posision
As I recal, your using an intercooler, and with only 6 PSI, that pretty much rules out air temp.

Make sure your exhaste is free flowing....

and if nothing seams to help, bit the bullet and buy some 94 octane gas......

also check your meter and make sure it's working... when idleing and driving, that A/F gauge should be going all over the place... if it's working properly

 

[Caezar75]

well gas octane? what is your static CR? 6pis = +1 CR .....CR > 10 = chance of detonation even with 91 octane...is the motor a stock turbo w/ dished pistons? or a shaved head? flat tops? i wouldnt run boost till you figured it out...then again that is obvious

later good luck

jon

 

[xaero]

My question is, Whats CR?

 

[zakaron 79zxt]

I can push 7-8 psi with no intercooler running 87 octane. Heck, I've run 10 psi at 3500 rpm with no detonation (I got some ping after that point though). Definately make sure that gauge is working and is grounded properly. Mylesm's right with the gauge bouncing around at cruise speed and idle. Check your plugs and see if they are blistering white, if so then it is running lean. The plugs are the tell tale sign of any engine. If you're sure the filter was clogged when you replaced it, do you know what clogged it? I mean if its gung in your tank then your fuel lines could also have build up in them.
xaero -> CR = Compression Ratio. Increasing boost raises its effective compression ratio(ie, more fuel/air mix to compress).
-zakaron

 

[spork]

well, I know I run 91 octane in my car 280zxt...and have never had it ping...plugs always look good and I can run 12 psi all day long in 100+ degree weather without an intercooler...So you've got a serious problem...I too would be looking for clogged/bent exhaust...and check your timing. Also, I know they're not cheap (but speed never is)but you might invest in an EGT gauge (exhaust gas temp). It will prove very helpful in tunning your car for peak performance.

 

[zakaron 79zxt]

Speaking of exhaust

Is your EGR valve hooked up and working properly? Without it, the temps can get very high and may lead to a ping issue as you describe. I just happened to think of it when Spork mentioned exhaust...
-zakaron