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Discussion Starter · #1 ·
Subject says it all. I have a '05 Phase II block and '97 Phase I DOHC heads with the head ported/polished/increased valve lift/3 angle valve job/racing valve springs so the only thing that's left is bumping the rev limiter a bit to tap some extra power from the air flow. Will 7800-8000 rpm be safe?
 

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2006 Impreza WRX Limited
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with the stronger valve springs you shouldnt get float at those RPMs but I guess I would be more worried about the bottom end at that point... is it stock?
 

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Discussion Starter · #3 ·
Yes the bottom end is stock. This is why I'm curious. I use full synthetic oil so the rest is can the design handle it with out new internals.
 

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:stupid: I don't think the bottom ends are balanced for more than 7k on a stock EJ25...
 

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Discussion Starter · #6 ·
I'm just being objective here, are these speculations are does anyone have any real world experience and/or documentation?
 

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Well lets just say that company that build our cars...."SUBARU"...set the redline where it is for a reason. :mamoru:
 

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We all know that doesn't mean anything. :)
Well I guess it would probably be fine for a while...but who knows HOW LONG it will last at that redline...

The real questions is are you prepared to rebuild your motor when it blows up?
 

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Meany Head
2000 RSC
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Well lets just say that company that build our cars...."SUBARU"...set the redline where it is for a reason.
Except that reason might or might not have anything directly to do with the capable redline of the bottom end. It could be set at 6250 because the stock cams are so limiting in the higher revs that there is no need to go higher. 6250 could be near the limit of the stock valve train before the onset of float. To say that Subaru set the redline there for a reason is really an incomplete answer. What exactly is the "reason"?

As for 8K? I honestly have no idea on that one. Gonna need an engineer or someone who has tried it to answer that one.
 

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Except that reason might or might not have anything directly to do with the capable redline of the bottom end. It could be set at 6250 because the stock cams are so limiting in the higher revs that there is no need to go higher. 6250 could be near the limit of the stock valve train before the onset of float. To say that Subaru set the redline there for a reason is really an incomplete answer. What exactly is the "reason"?

As for 8K? I honestly have no idea on that one. Gonna need an engineer or someone who has tried it to answer that one.
Well, he said he had upgraded valve springs thus reducing the probability of float. I agree stock cams aren't going to be very good at those RPM's but even at stock redline they aren't really that great (a Delta regrind might be a good idea). But that wasn't really the question. I was just looking at the most probable next weakest link. Most likely that would be the bottom end...
 

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Rally Hopeful
1997 L White - 2004 STi WRB
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im pretty sure you will break the rods at that speed, id even be careful with forged rods at 8k
 

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You'd probably have to build your bottom end. Even the EJ20 k's which are known for having a rev limit of 8250 have been known to smuch rod bearings if you take it up that high all the time. Also, the motor isn't really good for any power past 7k RPMs is the general concencus unless you have a very aggressive cam profile which would render your car pretty much undaily-able
 

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Discussion Starter · #16 ·
yea I'm not looking to race at 7000k for extended periods of time, but I'd enjoy some extra engine use on the on ramps :)

And yes, I am willing to rebuild.
 

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yea I'm not looking to race at 7000k for extended periods of time, but I'd enjoy some extra engine use on the on ramps :)

And yes, I am willing to rebuild.
Then do it and tell us how it goes :)
 

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First, raising the rev limit does not automatically mean the person will now drive the car at that new limit whenever they get in the car. Think for a moment how much time any of you spend at the limiter before you post up such puss-matic advice.

Second, The factory limit is set quite far below the designed limits to keep drivers who make mistakes from costing them money in warrantee claims. They have to protect the motor from anything possible, be it an accidental 4th to 1st shift or a total brainfart/seizure where the motor is just floored for no apparent reason in neutral. There is plenty of room above the stock limiter.

Third, a person's reasoning for wanting a higher rev limit may extend beyond the actual question. It's actually kinda nice to know up front that the valvetrain is up to the task, and that the cams and heads will flow beyond the stock limit. If you don't really know something you shouldn't spew advice as if you did. Questions like this are one of the areas where nasioc leaves RS25 behind.


As for the question, it is safe to get up there for short periods of time. And with not a whole lotta sustained cornering force at higher rpms. If you think you might be carrying the car through sweepers at 6500-7000rpm, it would be wise to upgrade the oiling system to keep the main and rod bearings happy. Bottom end failures have been shown to primarily come from track events where high rpm and high g-loading went together for too long of time. If you're dragging the car, it's probably not as bad (for the motor). We've had our phase I EJ25 banging off the 8125rpm limiter on occasion.....usually only long enough to make it to the next corner. If it would be for anything longer than a couple seconds at a time, we'd just shift back into our powerband.
 

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I think he was talking about his car "as-is" with very basic mods... 8k is possible on any car but with what he has now I don't think it would be safe or practical.
 
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