Tuning question

[Spectre23]

First off a bit about my setup...444cc injectors running at 52 psi (just over 500cc equiv.)GT28R turbofull 3" turbo-back exhaustARC SMICQ45 MAFAFE air filterWide Band O2 sensor and Pocket ROMulator for tuning

Now, I have the stock ECU but I have remapped it a bunch. I left timing relatively stock. Fuel is adjusted to about 11.9:1 a/f ratio throughout the RPM range under full throttle. This was measured with a wideband O2 sensor with datalogging. I am currently running 12 psi boost. Around 5500 RPM I hear some detonation (I think). So I turn boost down to 8 psi. Same sound, same spot. I richen the map to about 11:1 at that point. Same sound same spot. I back off timing on the ECU about 6 degrees. Same sound same spot. I throw in some 110 octane race gas. Same sound same spot. I put new plugs in gapped to .8mm. Same sound same spot. I back off timing on the cam sensor as far as it will go. Same sound same spot only now it doesn't idle worth a crap. I increase boost to 14 psi. Same sound same spot.

So I have richened it up (already somewhat rich to begin with), backed off timing, backed of boost, run race gas. And it acts exactly the same as it did before. This makes me tend to believe it isn't detonation. But do any of you have any clue what might be doing this?

[float_6969]

Well I agree that it's not detination. The easy way to tell if it is detination is to see if the ECU is throwing any codes. (I believe the detination sensor is 34/43 (i'm dislexic, I swear;)) Can you describe the sound? Something that consistant doesn't sound like detination to me. Does it only do it at full throttle, or is it regardless of load? To be honest, if it ALWAYS does it at the same RPM, it is probabally an exhaust sheild of some sort. It'll make you feel stupid, but I hope for your sake I'm right.

[Spectre23]

Actually, I have considered the idea of the exhaust because I think mine is hitting my rear subframe or dif somewhere. But I put the car in the corner of the garage to make room for my project bB and my roommate's SR swap a couple weeks ago. So I haven't been able to test my theory yet. The sound is a rattley sound but faint like detonation. But the exhaust hitting in the rear may make it faint like that. The ECU is not throwing any codes at all.

Thanks for the help.

[boost_boy]

What does it sound like at say 2800-3200 rpm? If it is really making noise at 5500 rpm, just keep an eye on the oil pressure (If you have a gauge).

Dee

[T88lexus]

I would wacth the oil pressure. and exhaust leak, kinda high pitch sound.

if you still using a ca knock sensor .. I would suggest you swicth to s20 knock sensor.

[iliketocrash]

s20 knock sensor? and why?

[Spectre23]

What does it sound like at say 2800-3200 rpm? If it is really making noise at 5500 rpm, just keep an eye on the oil pressure (If you have a gauge).

Dee

Sorry for the slow reply. NICO never emails me anymore when people reply to my threads.

Anyway... 2800-3200 it sounds fine. The knock-like sound happens from about 4400 - 4700 rpm then comes back again about 5700 - 6000 RPM. I am using the stock CA knock sensor. I don't have an oil pressure gauge, just stock guages + a boost gauge.

[float_6969]

I've never heard anything about switching to an SR knock sensor eaither. What is the deal with that?