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Old 06-05-2004, 04:19 PM   #1
Santo Domingo 2.5 RS
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Default It Blew, I knew this was going to happen one day!

Well! yesterday I was out with some of my friends and we were doing some street racing on this open road (dont come flaming me for this now). Well Im next to my friends turbo Type R and we gun it, We just side to side, and some kid gets in the way while Im in 2nd gear, so I hitted the rev limiter for a couple of seconds because I distracted myself with the other car. The when I get in to 3rd, a couple o seconds later I feel the car loosing power and after this a big ass cloud of smoke in my rear view, I let off the gas and and the car starts hesitating, i knew it right there, so Since I live like 5 minutes from the place I come back home, the car idle goes up to 1200-1400 and the motor is shaking, like one of the pistons is death and lots of smoke is coming out of my tailpipe, well, since it was realy late I turn off the car and get in to the house, hoping to check everything out in the morning.

This morning i got up, and went to check, first i check my catchcan, I has some oil in it, maybe 2 or 3 full spoons of oil, there had never been any oil in my catchcan beafore. I checked everything and there was lots of oil around by the exhaust manifold on the passenger side. I then turned on the car, it started hesitating and the motor was shaking, lots of smoke coming out of my tailpipe and high idling, but no audible knock or any kind of extrange sound was coming from the engine. I Disconeected my PCV and lots of white smoke was coming out of it. My boost gauge is connected on cylinder No3 Intake manifold runner and i could see oil in the clear plastic tube coming out of it. After this, I tried checking for the bad piston and umplugged the sparkplug cable for piston No.3, and nothing happenned the car did not stumble down or anything like it, so I thought this was the bad piston. I did the same thing with all of the other cables and everytime I disconnected one, the engine was allmost dying and starter shaking a lot worse. After, I turned it off and got all of my sparkplugs out, the one in piston No.3 was full of oil, piston No.1 looked like burning rich and the other two looked just fine. Im thinking that this is just a case of fried piston ring, but Im not sure since none of this stuff has ever happenned to me beafore. any of you guys have any idea of what might be wrong. .

what did I get myself in to??

My setup:
T3/4 .60Ar
6:1 RRFPR
J & S Safeguard
WRX fuel pump
6.6 PSI creeping to 7 sometimes
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Old 06-05-2004, 06:16 PM   #2
8Complex

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Yup... bouncing off the rev limiter is no good. Stock rev limiter is a fuel cut, which can most definitely cause some detonation. Chances are you just blew a piece off of a piston, but I kind of question your idle up like that. Mine ran just fine when I was missing a chunk of piston.
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Old 06-05-2004, 06:57 PM   #3
Do_It_Sidewayz
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i'm willing to bet you got a nice big hole in that piston
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Old 06-05-2004, 07:36 PM   #4
Drac9
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Mine cracked a piston close to the ring land and ran just like that. Onyl way to know is to pull the motor and pull them head. Then join us in the ej22T shortblock club.
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Old 06-05-2004, 09:09 PM   #5
Santo Domingo 2.5 RS
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Ill be pulling the motor on monday, and have some pics of the disaster. If there would be hole on the piston, wouldnt it be audible? also, like 8complex said, Idont get why the high idling.

Drac9- You know I was thinking of getting the Ej22T shortblock, but I didnt think It was going to be this fast. Could you please PM some information about the swap, or anything you might think would be important, I was searching but Im not really clear on everything.
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Old 06-05-2004, 09:26 PM   #6
Drac9
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Not much to say. I used the SOHC 2000 impreza L gasket. Shortblock from a 92 Legacy. Oil pump from a 92 legacy. RS waterpump and timing belt tensioner setup. Everything bolts up fine.
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Old 06-05-2004, 10:58 PM   #7
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Wow.
Do a compression test on it.

Bring on another 2.2 Hybrid!

(Check my website for some info on the buildup)
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Old 06-06-2004, 08:01 PM   #8
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Quote:
Originally posted by 8Complex
Yup... bouncing off the rev limiter is no good. Stock rev limiter is a fuel cut, which can most definitely cause some detonation. Chances are you just blew a piece off of a piston, but I kind of question your idle up like that. Mine ran just fine when I was missing a chunk of piston.
How can a fuel cut cause detonation when there is no fuel to detonate or pre-ignite?

I've seen Fitz' motor idle like crap when the SOHC piston lightened up itself, yet ran like a champ under boost.

-WaC
Wayne
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Old 06-06-2004, 10:01 PM   #9
8Complex

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Quote:
Originally posted by wac
How can a fuel cut cause detonation when there is no fuel to detonate or pre-ignite?
Well, I have no real proof, but I'm guessing that it's possible for the ECU to see the rpm needed to initiate the cut as it is spraying the injector, and end up shutting off the injector mid-fire. Granted, I can't speak from first hand experience, but I believe it's the main reason most forced induction setups with standalones use ignition cut to rev limit, not fuel cut.
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Old 06-07-2004, 07:10 AM   #10
wac
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Quote:
Originally posted by 8Complex
Well, I have no real proof, but I'm guessing that it's possible for the ECU to see the rpm needed to initiate the cut as it is spraying the injector, and end up shutting off the injector mid-fire. Granted, I can't speak from first hand experience, but I believe it's the main reason most forced induction setups with standalones use ignition cut to rev limit, not fuel cut.
I'm pretty sure the ECU doesn't cut fuel in "mid-fire". Most ECU's use microcontrollers with PWM control registers to set and operate injector duty cycles. It would be pretty stupid for FHI to override the PWM auto-reload registers or gate the transistor output drivers to allow partial lean conditions that can lead to engine failure (and drive up warranty costs), when there are zero-cost ways of doing fuel cut at the rev limit by designing the firmware correctly.

I'd be surprised by a standalone use only ignition cut for a rev limiter. At those high rpms, the last thing you need is fuel (probably at max duty cycle) washing oil off your cylinder walls. I'd stay away from those standalones if I were you. Perhaps you're thinking about the MSD ignition-only products, where they have no control over the fueling?

-WaC
Wayne
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Old 06-07-2004, 09:14 AM   #11
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Sorry to hear that man
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Old 06-07-2004, 02:58 PM   #12
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Can we get some fotos of the damage once you tear her down?
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Old 06-07-2004, 03:06 PM   #13
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Quote:
Originally posted by wac
I'm pretty sure the ECU doesn't cut fuel in "mid-fire". Most ECU's use microcontrollers with PWM control registers to set and operate injector duty cycles. It would be pretty stupid for FHI to override the PWM auto-reload registers or gate the transistor output drivers to allow partial lean conditions that can lead to engine failure (and drive up warranty costs), when there are zero-cost ways of doing fuel cut at the rev limit by designing the firmware correctly.

I'd be surprised by a standalone use only ignition cut for a rev limiter. At those high rpms, the last thing you need is fuel (probably at max duty cycle) washing oil off your cylinder walls. I'd stay away from those standalones if I were you. Perhaps you're thinking about the MSD ignition-only products, where they have no control over the fueling?

-WaC
Wayne
Well, you're dead wrong.
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Old 06-07-2004, 03:10 PM   #14
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Quote:
Originally posted by SubaFastR
Well, you're dead wrong.
Do you have proof otherwise? Or just upset that your motor blew the same way? (curious)
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Old 06-07-2004, 03:30 PM   #15
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I've never fried a piston...ever. They call it fuel cut because they cut the fuel. With stand alone ecus, they call it a rev limiter because they don't cut fuel, they stop spark. I've worked on the TEC, Link, Hydra and ECUtech. What's your experience?
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Old 06-07-2004, 03:47 PM   #16
Santo Domingo 2.5 RS
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so I should look nowhereelse this fuel cut was the responsable for what happenned? It was not even 2 seconds I think.

And yes, Ill see if I can get some pics of the damage for you guys to see.
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Old 06-07-2004, 04:22 PM   #17
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two seconds is bad
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Old 06-07-2004, 05:27 PM   #18
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Quote:
Originally posted by SubaFastR
With stand alone ecus, they call it a rev limiter because they don't cut fuel, they stop spark. I've worked on the TEC, Link, Hydra and ECUtech. What's your experience?
That isn't really the truth... they call it a rev limiter, yes, but they give you the option to choose fuel or spark. All 4 you mentioned are "pre-packaged" standalones that I'm sure they'd turn off fuel cut if they could. I'm unsure if the options are there, but that really isn't a valid blanket statement.
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Old 06-07-2004, 08:09 PM   #19
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Default rrfpr?

Could t have something to do with the rrfpr? I have noticed that with my '00 that the "rev limiter" is pretty sloppy in the sense that if you stay with your foot planted (even for 2 secs, as indicated earlier)it is a really fast on/off phenomena as the revs fall then go up then fall, etc. Does the boost drop off when this happens? Or if not does it fluctuate a different rate than the ecu fuel cut? Since boost is controlling fuel pressure with a rrfpr- which ultimately is controlling amount of fuel in the cylinder- could it be that the nature of the rev limiter coupled with a crude fuel managment lead to a lean condition? Oh, and I have NO experience with turbo cars, just been reading and trying to throw an idea out there
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Old 06-08-2004, 01:16 AM   #20
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^^^ That is the truth, too. Never thought about that aspect, but it could very likely be something like that.
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Old 06-08-2004, 01:23 AM   #21
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Quote:
Originally posted by SubaFastR
I've never fried a piston...ever. They call it fuel cut because they cut the fuel. With stand alone ecus, they call it a rev limiter because they don't cut fuel, they stop spark. I've worked on the TEC, Link, Hydra and ECUtech. What's your experience?
actually, the tec cuts fuel.

doesnt matter tho, there is always a little fuel that gets through the cylinder without being fired when you hit a rev limiter, what do you think the flames come from?
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Old 06-08-2004, 01:27 AM   #22
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well until you tear it down its all speculation, but I would say you hitting the rev limiter for two seconds contributed to a long under fueled engine. That simply is not enough fuel + too much advance in my opinion for such a high compression motor.

Who knows if you didn't hit the fuel cut/rev cut you may not have blown that day... but maybe later on...

if you have no money... larger injectors and safc. if you got money standalone. On the stock ECU your advance close to redline is 25+
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Old 06-08-2004, 10:27 AM   #23
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in a fuel cut though, arent you eliminating fuel from the cylinder? besides the aforementioned "mid-fire cut" theory, if there is no gas to spark, there is no explosion, so i dont see how that can be a problem, you would just be sparking pure air basically which wouldnt matter.

i am prob not thinking of something but it seems like it wouldnt matter if there is no mixture to combust. it would matter if there were still fuel, and it was lean, but not if there were no fuel.

Ben
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Old 06-08-2004, 12:26 PM   #24
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My theory (FWIW)

At redline-WOT, the injectors are running pretty close to wide open. When the fuel cut occurs, all the injectors close, so fuel pressure soars. The RRFPR rapidly bleeds off fuel pressure to get back down to it's targetted fuel pressure. Meanwhile, the engine drops below redline, the injectors go wide open again... and now fuel pressure really sags. So you're getting the same injector pulsewidth, but for the first few injector events, you're getting less fuel. The RRFRP tries to build pressure back up to it's target, but Whammo, you hit the fuel cut again, and the process repeats.

Just a theory - no measurements to support this, and I'm running a stand-alone setup, so this doesn't really apply to me anyway. Just some thoughts.

_Jeff
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Old 06-08-2004, 02:56 PM   #25
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Even if fuel is cut, some is left in the head, gets pulled into the cylinder, is now lean and has the potential for det. Now, if any of you have ever had a bad coil pack, you will understand that when ignition is cut, even under high boost, the car just falls flat on it's face. So, by cutting spark progressively (one cylinder at a time) you can slowly and softly prevent over revving. As a side benefit, the fuel still being in the cylinders cools the combustion chamber further reducing the chance of det.
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