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Moderating U!
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I have been reading a lot of posts of people with aftermarket turbos running 17-20psi on their stock EJ20 motors. Does anyone know the MAXIMUM a stock OEM EJ20 can take in the amount of boost before the stock internals needs to be beefed up (Rods, Crank, Pistons)? Just wondering. Is there a mathematical equation for this as well.

Kurlee Daddee
(THE ORIGINAL)
 

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On an EJ20T motor that gets driven a decent amount, figure staying around 16psi if you do not want to have problems down the road. At levels higher than this, the engine life drops very fast.
It will do it, but it will also break.
 

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I've heard from Josh @ Cobb (who's needless to say pretty experienced in this department) that 75,000 mile reliability can be attained with good tuning and intercooling up to around 20 psi. That's pretty good reliablity for that amount of pressure. Go Subaru!;)
 

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Hmmm....Dan:

If this wasn't the exact same question as the other max boost pressure thread, I'd be pissed the you posted the exact same response :p :D

anyone feel like merging this with the other thread?
 

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I think a head gasket is more likely to pop when you talk about pushing boost pressures to extreme levels.

If you tune a high HP turbo for lower boost, then God's explanation comes into play.
 

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God said:
Boost pressure means nothing. I can run 20 PSI everyday on pump fuel with a PE turbo reliably or I can blow it up at 15 PSI with a bigger turbo. HP is what matters not PSI. MaxHP is about 450 give or take on the EJ20 block.
with stock pistons and rods, i would disagree with the 450hp thing. The australians have proven for years that reliable horsepower is closer to 350. you can get over 450 on an ej20, but not with stock internals. Somebody will do it, and more than one person will get away with it. But many australian tuners make lots of money rebuilding engines that saw over 16psi on a regular basis.
It amazes me about some of the theories that are published here as fact. We might argue about differences in new versus old ecu's and how they handle bolt-ons,
But the ej20 has been very similar in bottom end design for over 10 years. You will find that if you go on Australian forums, that people making lots of power reliably(over 350) are doing internal work.
But i am sure us americans know more, so let's all run 20psi.
I will get everyone a deal on those pistons and rods.
Getting the hole out of the block might be a little tougher.
I hope i am wrong for everybody's sake.
But if i am right, my suggestions will keep people out of the repair shop.
my .02
 

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Let's first decide if we are talkin about wheel or crank horsepower figures. God is talking crank, but I'm not sure what the 350 figure is.

"Reliable" is yet another subjective term that gets thrown around often when this question is asked. My reliable may be totally different than yours. What is reliable? 25k miles, 50k, 100k miles?

If what you claim is the limit on the EJ20 shortblock is true, then I'd guess we would have several popped motors on this board already. I for one push over 350 crank daily and have so for about the last 7k miles. When I'm on the bottle, it's well over 400 crank.

I think ALOT of it has to do with tuning.

My 2c.
 

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Is that the motor out of a BG5 that made 200 kW stock? Those respond to timing and fuel so asking max boost is kinda sidestepping the issue. IDK because I’ve not even seen one in over a decade. Isn’t stock 1,1bar?
 
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