Hearing knock w/ 2.85 pulley and 60# injectors
06-03-2008, 02:11 PM
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Hearing knock w/ 2.85 pulley and 60# injectors
Initially I thought I heard an exhaust rattle, but it is only under load about 2.5k-4k rpms. Dealer said it was definitely fuel ping. Car has 2.85 pulley 60# injectors (professionally dyno tuned) and has good air:fuel through the rpm range and didn't see knock on the dyno. I'm looking for some suggestions because I need it to stay reliable, plus I hate hearing it in second gear when I go wot. Hopefully its just a tank of shitty gas but I always use 93 octane. I'm ordering a heat exchanger right away to lower temps, that might help. I'm looking for some other good suggestions.
06-03-2008, 03:27 PM
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I don't have the dyno sheet here but I believe the air fuel was right around or slightly below 12:1 at WOT at 7000rpm. I'll ask my tuner to look it up in the computer. As far as heat goes, I'm ordering the CX racing h/e this week.
06-03-2008, 04:04 PM
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How is the AFR through the RPM range, especially at 2.5 - 4K when you hear the pinging? 12:1 is high, 11.5:1 would be more desirable to protect against detonation especially if you don't have cooling mods. With 60# injectors you should be running low IDC so bumping up the AFR should be easy. If you arne't seeing knock on a meter, then you may not be getting actually pinging it might just be the injectors being noisey. I would definately check the AFR through the entire range though.
06-03-2008, 04:21 PM
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I'm waiting for my tuner to refres my memory on exactly what the AFR is through the range but it was a smooth line with no major fluctuations, definitely not running dangerously lean. It's not the injectors being noisy because the sound is almost like when a catalytic converter cover is about to fall off an older car and you can hear it vibrating. Its a metallic rattle type sound, not an exhaust problem either. It has a catback and cold air intake so that is at least a marginal help for IAT2s.
06-03-2008, 05:53 PM
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Correction: Confirmed that AFRs are in mid to high 11s through entire RPM range. Area, I'll have to check on the timing advance for this tune next.
Well I dumped a bottle of octane booster into a little more than 1/4 tank of gas left in the tank and did a test run. It only raises the octane rating one point but should be more concentrated in 1/4 tank. The sound is much less audible than before and is most noticeable at around 3800 rpm and can be heard faintly from 3000. But I don't know what exactly I proved, the culprit could still be bad gas but I won't know until I finish the tank and refill, and until then I'll be annoyed as hell.
Area47, it doesn't have any effect whether I stab the gas or let into it gradually when I go full throttle. Looks like I should get myself a wideband to see whats up.
Well I dumped a bottle of octane booster into a little more than 1/4 tank of gas left in the tank and did a test run. It only raises the octane rating one point but should be more concentrated in 1/4 tank. The sound is much less audible than before and is most noticeable at around 3800 rpm and can be heard faintly from 3000. But I don't know what exactly I proved, the culprit could still be bad gas but I won't know until I finish the tank and refill, and until then I'll be annoyed as hell.
Area47, it doesn't have any effect whether I stab the gas or let into it gradually when I go full throttle. Looks like I should get myself a wideband to see whats up.
Last edited by PocketRocket06; 06-03-2008 at 05:53 PM. Reason: Automerged Doublepost
06-03-2008, 06:00 PM
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definitely get a wideband. I think you are a little too lean though. You should be about 11.5 or even a tad richer when off the meth, and you need to check your timing. The heat is killing you though for sure.
06-03-2008, 06:08 PM
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06-03-2008, 06:13 PM
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I almost never beat on it and the last time it was brought to redline was on the dyno so I don't abuse her, in fact the reason I am so concerned about this is reliability. And not driving it hard doesn't solve the problems that still exist at wot. I just think it is strange that it happened so suddenly. I'll see what happens after I get the heat exchanger on and a fresh tank of gas. Thanks for all the input.
Holy posting in like 5 minutes! Jeeze guys lol. I'm sticking with the 2.85 for the summer.
Holy posting in like 5 minutes! Jeeze guys lol. I'm sticking with the 2.85 for the summer.
06-03-2008, 06:13 PM
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And I'm telling you that a 2.8 pulley with no cooling mods, isn't going to be a HUGE difference from a 2.9 pulley car with no cooling mods. How hard is that to understand? It's only .1 difference.
I'm pretty sure there isn't.
I'm pretty sure there isn't.
Last edited by ralliartist; 06-03-2008 at 06:13 PM. Reason: Automerged Doublepost
06-03-2008, 06:24 PM
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I'm referring to controlling your afr by just changing pulley sizes. Which is what someone was referring too. Which is not smart at all and doesn't quite work like that.