2.5L or 2.35L?

BAC5.2 · Post by **BAC5.2** » Thu Oct 27, 2005 8:19 pm

I have the following option:

Use a Phase1 EJ25 crank and rods, and make a 2.35L closed deck block, run WRX heads with cams and a fat turbo. All of the internals of this bottom end would be forged.

OR

Do I use a stock USDM EJ257 block, with the same heads?

TurboXS made 498whp with a 2.5 block and 2.0 heads and cams.

I have either option and I can go either way.

The first option would be forged and probably stronger, but the 2.5 block is semi-closed deck so it would run cooler and probably be plenty strong.

I want to shoot for 350 to 400whp on pump gas. Power across the rev range is important too, and low end torque would be nice.

Both engines will have somewhat high compression, but I haven't figured it out just yet (Matt Monson?)

So what to do? The first option would be more expensive, but theoretically more durable.

Tell me what you think!

professor · Post by **professor** » Thu Oct 27, 2005 8:39 pm

Few builders can match factory assembly of a block. And, torque is nice in all amounts

so my vote goes for the stock block, which is about to get so much more common in case you blow one up (as those WRX young'uns begin to wreck the '06's)

93forestpearl · Post by **93forestpearl** » Thu Oct 27, 2005 9:37 pm

I thought about getting a 2.5 crank as well. I decided 2.2 liters was enough for me, which will be about 400CHP from a gt2871r. I think its hard to beat the closed deck with badass internals.

I'm gonna wait on the WRX heads, instead I'll go with the Delta cams with a 5-angle valve job.

$800 can get you Eagle rods and Wiseco pistons. The pistons only come in .020 or .040 over and have the moly coating on the skirt. I'd take pics but my stuff is all down at the machine shop right now.

When building up the bottom end, you get to pick what goes into it. You can opt for what bearings you like, whether or not to get ARP headstuds, or to spend the $100-300 on the balancing.

I guess I'm the guy that likes to do as much as I can so I either save alot of money, or just get a lot more bang for the buck. What will cost me $4-5k would cost much more were I to drop the car off and say "just make it fast" like my friend did. A T70 in a 3sgte mr2? Not for me.

The OEM ej257 shortblock would definately be the easier route. I personally don't like the idea of lots of boost on cast pistons. But I suppose it all really comes down to tuning.

legacy92ej22t · Post by **legacy92ej22t** » Thu Oct 27, 2005 10:16 pm

Hahaha, Phil, you just got done saying that your build plans were top secret in another thread and then here you are tipping your hand for everyone to see!

I vote for the EJ22T build up. Gotta keep it real mang.

BAC5.2 · Post by **BAC5.2** » Thu Oct 27, 2005 10:42 pm

Well, original plans were top secret... but I don't have millions. The original plan was scrapped when the bill tipped several thousand dollars...

dzx · Post by **dzx** » Thu Oct 27, 2005 10:59 pm

2.5L block, there is no replacement for displacement. Locally someone made 479whp on the dynojet with a 2.5 liter sti block and 2.5 sohc heads.

azn2nr · Post by **azn2nr** » Thu Oct 27, 2005 11:51 pm

257 block. hands down. im biased to that setup but it would be nice to see a 22t buildup.

how may i ask are you planning on wiring up this monster???

BAC5.2 · Post by **BAC5.2** » Fri Oct 28, 2005 12:02 am

THAT is top secret. Mainly because I don't know.

I've got some ideas, just a matter of which will yield the most power.

Matt Monson · Post by **Matt Monson** » Fri Oct 28, 2005 12:10 am

All right. So, I am thinking 2.35l, and really only for 1 reason. Keep it "original" It's the same reasoning why my RS-RA will never enter an Impreza chassis. Beyond that, I just think it is a stronger motor.

It is hard to argue with a factory assembly, but Ej257's just aren't all that unique. And while those cast pistons can support a lot of power and boost, they are delicate when it comes to detonation. I have seen 3 of them go on the dyno while tuning. Forged pistons in an Ej22t will be more forgiving to that sort of learning curve "oops"

So, what are you going to use for a turbo? To break 400whp you need a freaking huge turbo that will run you $1500-2000. And injectors in the 800cc range. 300whp is pretty easy these days, 400whp is the holy grail.

Also, some have expressed concerns about the long term viability of Ej20 heads on the Ej25. It has to do with the bore difference and that the Ej20 heads have some of their flat mating face crossing into the piston area. Using those heads will have a smaller differential in that respect and be a "safer" tune. And with the 2.2l you can pick you compression when you buy the pistons. For the kind of power you are looking to make, I would want to be down around 8:1. A stock Ej257 with Ej20 heads is in the mid 8's. Not dangerous in and of itself, but again, without a perfect tune, that's enough that you could detonate on a hot day or under some other variance from the norm...

93forestpearl · Post by **93forestpearl** » Sun Oct 30, 2005 10:06 pm

Matt, will I be asking for trouble by sticking with the stock 8.5:1 compression and shoot for about 400chp? Thats how the pistons came from Wiseco, since they stock them. I won't be going beyond that power goal untill I get out of school and get something else for a daily driver (STi).

Post by **DLC** » Sun Oct 30, 2005 10:48 pm

I like the idea of the EJ22 block with the strong bits inside, so that if/when you get to 400, you don't have to worry. Chosing your compression ratio is also important, possibly more so since you may have a LOT of tuning to do. Headroom is a good thing in that case.

Glad to see a number of really serious builds going on now.

Matt Monson · Post by **Matt Monson** » Mon Oct 31, 2005 6:03 pm

I don't think 8.5:1 is an issue, as long as you tend to your fuel and EM. A number of the factory race engines from Subaru over the years have been 8.5:1...

BAC5.2 · Post by **BAC5.2** » Mon Oct 31, 2005 7:25 pm

Matt -

What would my CR be with a 2.35 and USWRX heads? High 8's?

I'd like 8.0:1 I think.

I am going with the 2.35L, simply because it'll be bulletproof. I can throw TONS of boost at it and make some great power.

A local made 450whp on a 2.0L on race gas, and I'll be using a similar turbo.

It's possible that my car will become a rally car, so the 2.35 durability will be a nice feature.

Matt Monson · Post by **Matt Monson** » Mon Oct 31, 2005 9:05 pm

Well,
If you get your pistons from Crawford or AxisPowerRacing, you can take your pick of CR. They do a lot of 2.35l engines. IIRC, their off the shelf pistons are 8:1. They have already done all the math for you...

dwreck30 · Post by **dwreck30** » Tue Nov 01, 2005 1:22 am

What price are you looking at to do the 2.35 setup including EM and everything? What management are you going to use? Just curious.

BAC5.2 · Post by **BAC5.2** » Tue Nov 01, 2005 3:25 am

I couldn't even give a price estimate. It won't be cheap, that's for sure.

I've gotta map everything out with my boss and make sure it's all doable.

206er · Post by **206er** » Tue Nov 01, 2005 4:52 am

what turbo is good for 350-400whp? what is the neighborhood of boost required for this power?

93forestpearl · Post by **93forestpearl** » Tue Nov 01, 2005 9:48 am

I know someone who put down 380whp in his s14 with a red top. That was a gt2871r .86 trim. I might go for the .64 turbine which would have more top end, I think. The spool on the gt series is unreal. Kinda spendy though, they'll run ya $11-1200, at least that is what I've found so far. Don't forget that you'd have to change to Garrett flanges.

BAC5.2 · Post by **BAC5.2** » Tue Nov 01, 2005 3:27 pm

A Deadbolt Superzilla made 450whp in a 2.0L WRX on race gas.

Matt Monson · Post by **Matt Monson** » Tue Nov 01, 2005 7:03 pm

What's an S14 got to do with EJ power???

93forestpearl · Post by **93forestpearl** » Wed Nov 02, 2005 7:59 am

You do have a point Matt. I was just referring to the turbo flowing that much. I realize that differences in engine design will greatly affect power output, but I thought the turbo can only push so much in any any application. When plotting on a compressor map, engine style isn't a variable that is really considered, at least as far as I know.

Do I make any sense, or am I just late-night rambling?

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2.5L or 2.35L?

2.5L or 2.35L?

2.5L or 2.35L?