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Old 09-27-2001, 12:03 AM   #1
RS2000
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Default Should i get pistons?

I'm going to turbo my 2000 RS but would like to lower the compression before I do. I was thinking of getting custom pistons to lower it to like 8:1 so I can run higher boost. Would this be worth it or should I just keep the stock compression and only run 5psi so I don't blow my motor. Any info would be appreciated.
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Old 09-27-2001, 12:28 AM   #2
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My 5 psi high compression motor runs with a stock WRX, 6 psi pulls away clean, 8 psi keeps up with a modded WRX

8 psi on 3 cylinders (after trying 14 psi and taking out #4) was good for a 13.7@96.6 at 6,000 feet...

Keep the high compression and buy a timing retard box...

Larry
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Old 09-27-2001, 01:06 AM   #3
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I'd agree with Larry, take the money you'd spend on pistons and put that towards better engine management.

If you're really bent on running lots of boost, you'd want better management along with those new pistons anyways.
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Old 09-27-2001, 04:07 PM   #4
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If i do not get the pistons, I'm going to get a tec II or something comparable. What else should I get in addition to that and how much could I expect to pay for install and tuning of just the tec II and any extras you would recommend. Thanks for the info guys.
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Old 09-27-2001, 04:55 PM   #5
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I wouldn't buy pistons before a aftermarket ECU. You will get much more for your $ with an ECU than pistons.

If you blow up the motor however that is the time for forged pistons...don't ask how I know.

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Old 09-27-2001, 06:09 PM   #6
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I would get a dog box before pistons without it your not going to be able to run high bost anyway right?
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Old 09-27-2001, 06:45 PM   #7
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I would get pistons because the ones your car came with are frail and i know a tec 2 owner who went throught 2 sets even with his properly tunned tec 2.
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Old 09-27-2001, 07:16 PM   #8
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Bill, there are quite a few other MY00 2.5RS owners running high boost, both with and without TEC-II engine management. I wouldn't feel comfortable making a statement like that at all. I wouldn't call a slightly tweaked high-boost map from another car "properly-tuned" either. Shiv's base map for the TEC-II is much much more conservative than the one that was loaded into Mark's car, and I suspect that if he had started with that one instead and then worked upwards slowly, the engine damage might have been averted.

Installing pistons is a rather involved and expensive affair unless you are doing all the work yourself. There is plenty of hp to be found in MY00 motors, even with ~10:1 compression - just don't be greedy and have a very sensitive ear, that's all.

-Edwin
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Old 09-27-2001, 07:51 PM   #9
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I wouldn't call an engine "properly tuned" if it detonated enough to destroy two sets of pistons. Plus, he's talking about getting new pistons to lower the CR, not necessarily because the stock ones are too weak. But obviously if you go with a new set of pistons with a lower CR, you might as well get a nicer set of forged, high-strength pistons.

But just increasing the strength of the piston in a problematic engine doesn't do anything to help you. There shouldn't be detonation in the first place... so buying stronger pistons to "cope" with the detonation is not an adequate solution.
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Old 09-27-2001, 09:04 PM   #10
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Edwin I feel perfectly comfortable in saying that the my00 pistons are week having also seen non boosted ones fail. After seeing what i have i would not and i repeat not turbo a 2000 2.5 lets not fool ourselves there is no such thing as a low boost turbo that stays low boost. Lets not start a battle here more of the my00 have failed than the other style trbo or no therefore doesn't that make them seem less strong? Edwin don't make me send you the number of my00 pistons subaru of america has replaced under waranty
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Old 09-27-2001, 09:09 PM   #11
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ok, i may just scrap the whole engine build up and put in an STI Ver. V engine, trans. and ECU. What exactly would I have to due to be able to run that engine on 93 octane gas without having to add octane booster to every tank of gas. Thanks. If anyone has any other ideas for me, let me have em. I'm open to any suggestions.
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Old 09-27-2001, 09:18 PM   #12
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Bill: inquiring minds want to know! If you didn't have firsthand knowledge of the spectacular failure rates of MY00 pistons, I'd still be in denial myself.

The poor guy had to go through two sets of pistons, and the TEC-II zealots are still inclined to blame the tuner(s) instead of the engine. The first time may have been partly caused by carelessness with the gasoline quality, but the second failure occurred after extensive precautions were made to run a safe map. Aside from the extremely slim possibility of a TEC-II failure or hiccup, I saw nothing in his maps or gauge readings to indicate any impending signs of trouble. Once I look past the awkward interface and buggy software, the car does run like a champ (at least until the pistons let go).

-WaC
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Old 09-27-2001, 09:53 PM   #13
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Wayne any room behind your brickwall for one more?
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Old 09-27-2001, 10:04 PM   #14
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LOL... Wayne, I appreciate the pat on the back but you have more faith in me than I do.

We've traced the first set of pistons back to high boost (10-14psi), bad gasoline (admittedly 88 octane in a 93 tank). As for the second set, *shrug* I don't know. The gas was fine... and to the best of my knowledge there was no hardware failure. What's left?? Improper tuning on my part. I'm new at all this forced induction stuff. Give me a bored out V8 and a Holley 750 carbeurator and then we'll really have some fun. Oh, and for those of you that don't know; I have no problem sticking to my guns when I think I'm right, but when it's pretty obvious that I've screwed up, I have no problem admitting it. I do it pretty often.

Quote:
I wouldn't call a slightly tweaked high-boost map from another car "properly-tuned" either.
Edwin's probably pretty much on the nose with this one with the original set of pistons. We used an almost set of perfect maps from another MY00 and expected them to work on my MY00 with next to no modifications. Needless to say, I think this exhibits the differences between motors and efficiencies; even if they are the same build/CR.

As for the second sets, no one can find a cause. Knock sensitivity had been turned up, boost had been turned down, timing had been retarded in all zones, etc... It definitely wasn't the same maps as originally experimented with.

As for Bill's claim that the MY00 pistons are frail, well, no disrespect intended but I don't think that's the case either. I think we're seeing more failure in the latter years due to the higher compression ratio. This alone would make them more prominent to ping. I too have seen the multiple sets of pistons that are being replaced by the dealerships (Milford Subaru in particular) and it is quite numerous. I would however be interested in finding out why all 5 of my pistons broke in identical locations. Is this a weak area of the piston? I'd love to sit down and shoot the shiznit with another Mech Eng. from Subaru over a beer and figure that one out.

Bill: Where are the non-boosted MY00 pistons breaking?? I'm wondering if it's in the same zone as mine.

Will we ever know what caused this?? Probably not. So maybe we can all agree on a few things that would paint a pretty bleak picture had all the factors lined up.

1) The MY00 pistons are more prone to pinging than the MY99 due to the higher compression ratio.
2) The Tec2 has some bugs and will not adapt to every backwoods tuner who has no experience on AWD turbo-charged cars. In retrospect, I believe it is the backwoods tuner who is slowly learning to adapt to the quirks of the Tec2.
3) I like boost. Just ask Wayne. I've always loved to go fast and if it's as simple as looking at a few parameters once or twice and deciding that I can turn up the boost... I just might be guilty. Maybe my judgement was skewed and I overlooked a parameter or two... I dunno....


RS2000: Look into an EJ22T. It's a low compression closed deck block that was used in 1991-1994 Legacy Turbo's. Retail from Subaru of America for a brand spankin new shortblock is $1495.06. Talk to Bill Harvey from Exeter Subaru to see what he can do for you.

Best regards,
Fitz

Last edited by Fitz; 09-27-2001 at 10:19 PM.
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Old 09-27-2001, 11:00 PM   #15
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Bill - just telling me "look at the number of pistons replaced under warranty" doesn't say much at all. How many MY00 cars are there out there vs. MY99 cars? Quite a lot more, if I recall correctly. Wasn't it something like 2100 MY99s and 6100 MY00s? That's a factor of 3! So unless you've statistically normalized your "piston failure rate" against the total number of cars produced (namely, there are more than 3 times the number of MY00 piston failures versus MY99 failures), you're just spreading more FUD (fear, uncertainty, and doubt) around.

I'm also not sure what happened on the second set of pistons, but if the maps were conservative that time around (and without having seen them, I'm not sure just how conservative they were), even if the pistons blew, it's rather immature to just automatically blame pistons. For one thing, weren't the pistons brand new? So let's look at it:

block + original pistons = blowup
block + new pistons = blowup

Um, did anyone else check the other factors, like the block itself? It's the one variable that stayed the same throughout both engine failures, after all. If the gas changed, the tuning changed, and the pistons changed, and it still failed, isn't it time to start checking the rest of the engine? You're making the same amazing jumps in logic that Impreza RS dot com is!

I'm blaming the tuning process because it was a bit too optimistic. TEC-II or not -- do you really think that if I were to throw a turbo kit on my wagon, blindly copy all of Wayne's piggyback settings, enter them into the ITC/S-AFC/J&S, sacrifice a rabbit, and immediately take off and race the first WRX I see on the highway and proceed to blow it up, that I'd be justified in blaming my stupid EJ22's "weak pistons"? If you're willing to pay for my replacement EJ22T block afterwards, hey, I'll start placing calls and maxing out my credit cards tomorrow. sheesh...

-Edwin

ps: and no, I have never done anything to any rabbits. Actually, I like rabbits a lot and think they are quite tasty^H^H^H^H^Hcute.
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Old 09-27-2001, 11:16 PM   #16
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Quote:
block + original pistons = blowup
block + new pistons = blowup

Um, did anyone else check the other factors, like the block itself? It's the one variable that stayed the same throughout both engine failures, after all. If the gas changed, the tuning changed, and the pistons changed, and it still failed, isn't it time to start checking the rest of the engine? You're making the same amazing jumps in logic that Impreza RS dot com is!
Edwin- I think you are using the same logic as you know who, by making that statement about Mark. He and others went through the motor very carefully and spoke/reviewed the situation with many others who have replaced Subaru pistons (one who is an excellent Subaru Mechanic). I am kind of surprised, coming from someone who has had countless problems/failures and tons of help trying to diagnose them, free and expensive. I would think you would offer a more helpful type of reply (eventhough diagnosing Mark's problem is a bit off topic), instead of, it can't be the pistons, it had to be wrong tuning because you are new to the Tec-II.

Edited for a more clearly defined explaination as requested.

Paul G. (running behind brick wall, and staying there.)

Last edited by paultg; 09-27-2001 at 11:35 PM.
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Old 09-27-2001, 11:19 PM   #17
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Quote:
Originally posted by paultg

Edwin- I think you are using the same logic as you know who, by making that statement. I am kind of surprised, coming from someone who has had countless problems/failures and tons of help trying to diagnose them, free and expensive.
Well, then please explain how I'm doing so, Paul. I don't mind being corrected. But I'd like to know why.
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Old 09-28-2001, 02:52 AM   #18
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Uh guys--

There are nearly 80 TEC-II'd EJ25 running around in the US. About 20 of those are MY00 cars. And half of those, including mine, are turbocharged. As far as I know, there have only been three failures in total (among all the EJ25 cars). One was in a NON-intercooled 10psi MY99 set up. And the other two were in Mark's MY00. I don't think there are enough data points to suggest that the MY00 engine are "weaker" than earlier engines. In fact, the several other daily-driven boosted MY00 with no problems suggest otherwise.

Just my 2c,
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Old 09-28-2001, 03:43 AM   #19
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Don't forget my 00 #4 piston gave up the ghost. Cracked in the same spot as all the others. No audible detonation, 100 octane at 12 psi at 6,000 feet with good EGT and rich lean meter just right (fueled by 2 extra 480cc injectors).

One minute 12 psi, the next second only 8 psi is available, a few days later the rod knock starts...

Larry
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Old 09-28-2001, 03:43 AM   #20
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PS: at 6,000 feet that is like running 9 psi at sea-level, on 100 octane. Should be very safe.
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Old 09-28-2001, 03:53 AM   #21
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Larry-- Not when you are running additional injectors mounted at the throttle body. The Impreza manifold is completely inadequate for TBI. Terrible cylinder to cylinder fuel distribution. Cylinder 3 and 4 run much leaner than 1 and 2. And since most read a/f in the exhaust collector, all they are getting is the average of all four cylinders. Not the ideal for of fuel enrichment. And without properly controlling ignition timing, there is little hope that peak cylinder pressures are at safe levels (even without the presence of detonation). Basically a double whammo.

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Old 09-28-2001, 08:04 AM   #22
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I just feel that the design of the pistons are por since they already had a small amount of material above the ring and then subaru went and cut a valve relief right there making it worse then somehow the ej2o comes here with square reliefs again and no stupid valve relief cuts.

Shiv this isn't an anti tec2 thing because they have had piston failures in the same area with the factory ecu and no mods to the motor.

Nobody will ever agree and edwin i don't need to grab a calculator to know what i would be comfortable with..

Shiv as far as your car i am pretty confident that if i relaced my pistons with coke cand you could make the thing run safe.

Its funny for those people who have been here awhile will tell you at first nothing was safe then turbo everything and now stuff is breaking. Anyone will tell you the tranny is weak, but god forbid if you say the pistons may have a dsign problem when it comes to boost.
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Old 09-28-2001, 08:20 AM   #23
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Quote:
Originally posted by bill harvey
Shiv as far as your car i am pretty confident that if i relaced my pistons with coke cand you could make the thing run safe.
Bill, you've just made my point for me. If the tuning had been more conservative, Mark might have been able to see it coming and tune it safely. As it is, it just let go, and no one really know why for sure.

I'm not saying the pistons are strong. I'm simply saying that the engine failure didn't necessarily have to happen. It could have simply started off with less boost/retarded timing and gradually gone up. So what if Mark found that he's limited to 5psi of safe boost? At least at that point he'd have a choice as to whether to replace his pistons or not. Right now he has no choice, and that is never good, weak pistons or not!

Again, I'll repeat myself simply -- I am not talking about the pistons... The rest of this debate about pistons is still highly controversial and yes, I still don't see where your "evidence" is coming from, even after talking with Wayne on the phone for an hour last night and going over everything we both know about these engine failures (which isn't much, considering we don't work in a Subaru dealership like you), but common sense and prudence when starting to tune a car is not.

-Edwin
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Old 09-28-2001, 08:35 AM   #24
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post was edited because people who know me well, thought that my warped humor was a personal insult......

and with that i am out of the thread see you all in another thread at another time.
Cheers

Last edited by bill harvey; 09-28-2001 at 09:41 AM.
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Old 09-28-2001, 01:17 PM   #25
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Deep breath folks.... shouldn't I be the one getting upset here? It's been implied that I don't know how to build a motor, read a couple of gauges, know which pump to visit at the gas station, etc... and I'm the one still smiling.

Seriously though... Sorry we've taken over this post. It wasn't meant to happen. I'm sure... .no, actually I know for a fact that everyone that has posted here has the best of intentions and is simply attempting to help get to the bottom of this issue. No matter how diverse our opinions are, we're all still professionals. I appreciate everyone's help, regardless of how right or wrong their opinion is. Next round of drinks is on me.

Thanks again guys,
Fitz
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