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10-08-2001, 10:21 PM | #1 |
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Pinging in nearly stock WRX??
I just noticed tonight that my rex seems to be pinging now in the 5.5K to Redline range under WOT? Only mods are a TurboXS BOV, silencer removal, and a straight pipe after the last Cat. Any reason this would be happening? I was led to believe that if anything the few mods I have done would make the car run slightly richer(aka BOV) not go lean and ping. CEL light has not come on even while I can hear the noise.
James
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10-08-2001, 10:36 PM | #2 |
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#1 get the next tank of gas somewhere other than where you filled up last to eliminate that.
Then check timing, what boost it's making (guage), and fuel pressure. At least that would be my approach to it. |
10-08-2001, 10:50 PM | #3 |
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Thanks for the response
I buy nearly all my gas from the same Mobil station, maybe they simply got a bad batch?...I guess what I'll do is just go easy on it and put in some octane boost till this tank is almost gone, then refuel somewhere else. Hopefully that will solve it. Also I thought that the ECU detected knock even at inaudible levels and gave a CEL(flashing) when it did. I wonder why I wouldn't get it with such an audible knock. A definate tapping noise accompanied by slight hesitation(ECU pulling back the timing??)
James |
10-09-2001, 12:05 AM | #4 |
Dynamic Uno
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Here is my theory.
Due to your straight pipe, your boost is higher at WOT is higher than stock due to very little back pressure after the turbo. So the boost creeps up and the stock WG cannot handle all the flow. You run high boost and ping. -Alex |
10-09-2001, 04:08 AM | #5 |
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to add onto Alex's little thing there you guys are prolly already seeing winter blend fuel in your area, cause i know we are already getting it here. It may ping a littel bit till the ECU relearns the timing curve with the higher ethanol amount in the fuel it burns easier.
As far as knock, the ECU is always sensing knock, the pinging it not the knock that is harmful, it's the knock you can hear...a.k.a: Detonation. It won't flash the MIL unless there is a severe problem and it goes into limp home mode. And you'll KNOW when that happens. Jeremy |
10-09-2001, 09:28 AM | #6 |
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Get it checked out.. take it from me...
My car is in the shop now and I am getting misfires all over the place. From basically a stock car I had weird things going on with my car so.. get it checked out ASAP... doesn't hurt to do so anyway before you really start modding |
10-09-2001, 11:47 AM | #7 |
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is your car at the Subi dealership?
What did they say about your mods? Do you have a turbo back exchaust as well catless up pipe? cheers T. |
10-09-2001, 12:18 PM | #8 |
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Taking it in
Yeah, I think what I am going to do is take off the str8 pipe and put the muffler back on. If it continues to do it then, I will take it into the shop. I really don't want to be having to buy a new motor. My only thought is that it is amazing that something as minor as running a str8 pipe from the last cat(All 3 are still on the car) could cause my boost to spike to the point of detonation. I know of a few others running that same setup and not having a problem?
James |
10-09-2001, 12:18 PM | #9 | |
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the computer limits boost.
it wont let it go higher??? Quote:
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10-09-2001, 12:52 PM | #10 |
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Not quite, what Alex is saying is that you're getting so much flow with so little restriction that the stock waste gate cannot vent the pressure down to the 13-14 psi that it's *supposed* to be. The waste gate is just a purge valve designed to prevent overboost.
I agree with that, but it's probably a combination of things. You're actually going to run leaner (not richer) with these mods, b/c of the lower restriction (no exhaust, no IS). True, the non-recirculating BOV will make you run rich, but only when it's venting, which is only on trailing throttle, not at WOT. Running leaner will make you burn hotter, leading to earlier detonation. The winter gas could also have something to do with it, although I would get your car checked out. Hope this helps. Loren |
10-09-2001, 01:25 PM | #11 |
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Okay
Does a str8 pipe like the one I have flow better than a true exhaust system? It just seems weird that something as little as those two mods would lean it out to that point. Basically this means that a stock rex can't handle an exhaust and intake? Wow Subaru really tuned this car to stock with little clearance.
James |
10-09-2001, 03:47 PM | #12 |
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My theory would bad gas or an ECU problem. I ran for 2 days, yesterday and the day before, with nothing bolted after the last cat, which would be the equivalent of a straight pipe like Invidious's setup. I have a boost gauge that I monitor and there was absolutly no change in boost behavior due to that, it was just loud. Yesterday, my friend and I installed my Scoobysports downpipe and my Cobb catback (which I had taken off- also no wierd boost behavior). With the downpipe installed, and the much higher flow created by this, my boost runs a bit higher, it will spike to about 15psi and I get close to full boost in 1st gear. So there is a big difference in boost behaivor, but no pinging whatsoever. Even when more boost is caused by less backpressure, the MAF is still reading the volume of air entering the engine, and a functioning ECU should retard timing as boost increases. That's my take on it.
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10-09-2001, 05:12 PM | #13 |
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A flashing MIL indicates that a cylinder misfire was detected, which isn't the same as engine knock. There is no trouble code that means "excessive knock." Eventually, you might get an excessive EGT MIL, though. The stock knock sensor will detect knock that you can't hear. Which makes me wonder whether you're hearing knock or, because you're running without a muffler, you're now hearing some other engine sound that had previously been damped out by the muffler.
If you can, find someone with a scan tool and monitor your timing advance. That is your best indicator of whether you ECM believes it is hearing knock. Blugin wrote: "My theory would bad gas or an ECU problem." IMHO, it's conceivable, but unlikely, that he got some bad gas, which would usually also cause other symptoms. And I have no idea about how you could convince a Subaru tech that you have "an ECM problem" in the absence of a trouble code that meant "ECM malfunction." |
10-09-2001, 06:17 PM | #14 |
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even if the car was over boosting, that wouldnt be causing the knock. the ecu will correct for any boost level regardless of what it is or how its getting to that point(in low-modd'd cases like this), knocking will occur when the injectors run out of duty range for the fuel load. and since the stock injectors are good to nearly 1.5 bar, even on an upgraded turbo, that would be a boost spike of almost .5 bar, which you couldnt get even from removing ALL cats.
my suggestion(as bad as it sounds) is cyphen out your tank, and put fresh gas in. it could be some water in the tank or just a bad tank of gas. if it continues after that swap then you have a timing problem either in your ecu or ignition timing. also, the adjustment to winter fuel mix isnt going to be enough of a change to cause knock. as far as a new motor, i wouldnt worry about it. if your car got hit with a hard enough knock to do damage it would have gone into the afore mentioned "limp home mode" $.02 |
10-09-2001, 08:07 PM | #15 |
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It wouldn't hurt to add a bottle of quality octane booster. They usually will help out if water is the problem also. I'd do that and see what happens.
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