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Discussion Starter · #1 ·
So a little while back a was road tripping in my wrx and suddenly I had a destroyed bottom end. I was fortunate enough to break down at a tiny Subaru specialty shop. The owner set me up with a with a hybrid build and told me I didn't need to do anything else to it. The old block had been tuned but I'm noticing some pulsing and shaking and idle so I figure my next step is to get it tuned but I'm also looking for recommendations on proper upgrades moving forward. Thanks to all that read this
 

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Wait. Stop the presses.

You just installed a 2.5L bottom end into a WRX that previously had a 2.0L motor and the ECU was NOT recalibrated for the new motor???

That is very very not good!

I mean, were the injectors even updated? The tiny 440cc 2.0L injectors are not going to supply the fuel demand of the larger 2.5L motor. That's a lot of investment to very nearly commit the new motor to an early death.
 
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2004 wrx
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Discussion Starter · #3 ·
Wait. Stop the presses.

You just installed a 2.5L bottom end into a WRX that previously had a 2.0L motor and the ECU was NOT recalibrated for the new motor???

That is very very not good!

I mean, were the injectors even updated? The tiny 440cc 2.0L injectors are not going to supply the fuel demand of the larger 2.5L motor. That's a lot of investment to very nearly commit the new motor to an early death.
Alright, thank for the info. The guy that did the work told me that wasn't gonna be necessary but I thought that might be off. I'll be sure to remedy that mess right way. Thank you for saving me from catastrophe
 

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The guy that did the work...

Was he familiar with Subaru engines? There's a lot to unpack here. How did he remedy the Compression Ratio problem? Were the combustion chambers machined to match the larger bore of the 2.5L block?
 

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"Upgrades"...you mean making the engine more vulnerable to catastrophic failure....? "Old block had been tuned"....'blocks are not tuned.(other than when blue-printed) … running and complete engines are tuned. When you say 'old block' do you mean yours?...or the 'hybrid'?

Zax and Plasma rang some alarm bells for you...but again...were the injectors (let alone replaced) even cleaned? My advice is to set aside your developing mania to join the Suburu-ego community and get your car properly fixed and keep it then as stock standard as possible.

Zax wisely asked about the machining of the combustion chambers...which in high performance engines even stock standard should be 'volume' matched when on the engine...unless the engine was block height and piston matched as would be in in blue-printing. Increasing compression-ratio in turbo engines adds substantially to bearing load
and if your chambers are smaller than the original heads of the replacement block then you are increasing compression...over and above any metered boost.

I've had straight tuning even for exhaust changes priced at over $1000.00. I don't know how you are 'gonna' fix this right away because you really have to take the matter back to the engine supplier and when he shows you the door, some consumer advocacy or the court....or wear the costs...I learned my lesson with small-time specialist 'make experts' nearly 55 years ago now....and that's quite a story but not for here.... The "finale" though...somebody else he duded got to him with a motor cycle chain before I did, as he crawled out from under a car.... Fifty years later I heard, in one of those 'amazing coincidences in life' that he'd moved to Qld, had his numerous GTO's and Plymouths and other high performance yank-tanks on a property but was behind in the rent. Unresponsive to demands ...the owner acted...had all his cars towed to the tip...a fitting reward for his past sins.
 

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Discussion Starter · #6 ·
Well to start off, I'm Plasma, and the guy who made the post. I'm not great with words so I'll try to clarify some of the things I've said. When I said "the old block had been tuned" I meant the ECU had been Dyno tuned when it still had the ej20 long block in it. The upgrades I was referring too, while also intending to upgrade in terms of performance, my main focus in terms of upgrades is longevity. I researched catch vs aos, for a second I almost bought into the parallel vs serial fuel rails etc.

While the heads combustion chamber has not been machined, it does have either .51 or .051mm think head gaskets to compensate for the difference in compression ratio. I don't remember where the decimal point goes in there lol.

Because I haven't mentioned it yet, the car has 150k mile ej20 heads on it with a fresh from factory ej25 shortblock and a 07 sti drivetrain conversion.

Present day: I've learned a lot more about wrxs and the little things about these cars since I made this post. Since then I conferred with both cobb and PRE racing about the future of the car. I've been told that the machined heads are not a necessity as of right now, but in the future it would be a very good idea to get it done. So I sourced ej20 heads for a total loss crash and am waiting to send them to a shop to have them machined and ported when that time comes. The car has had pinks installed as a drop in mod at the recommendation of PRE. Recently the car was supposed to be tuned but the clutch started to slip on the Dyno so the session was rescheduled then put off due to the quarantine. I had installed a new clutch and, as I found, the car had the wrong flywheel installed as well as clutch which, while it did not do any harm, didn't do the car any favors either. So that has been corrected. I have been keeping an eye on the afr and keeping it out of high boost till it can be properly tuned, again by professional recommendation.

I do appreciate your concern, and frankly, the slight patronization was fair as at the time I made the post my head was well above the clouds in this. But, I am back the earth and fixing what I can and letting the professionals do the rest.
 
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