Building my EJ257 longblock....many questions and opinions

First of all let me state that I have a complete EJ257 longblock minus the valve covers, oil pan, and manifolds.

I have all the AVCS components. However after my tuning session and talking with several great guys (LiquidForce, Doug, SS, Slowwrx) AVCS is not really needed at all. Well there goes my heads.....or is it?



The plans are as follows....
1) Mahle pistons. I dunno if I will go with the 4032 ones LiquidForce has or the 2618's. I don't think the 2618's will last long but some scares with the 4032's on Nasioc has me a little concerned. However LiquidForce has made a strong believer of me. Opinions????

2) I dunno if I am gonna throw in some rods or not. Slowwrx has stated that I don't need rods. So has many other people since I'm not gonna hit 600+ whp. However that is the next weak link in the engine. Thoughts?

3) I am HANDS down going with cams springs and retainers.

a) Here's the tough decision. I really really really want the GSC cams. However they only make cams for the STi since the website says AVCS cams. However I will not have AVCS. Well the capability will be there but I can't control it unless I go with the Hydra which I have made my mind to not deal with. I'm sticking with Ecutek and my EasyECU since I already have it and it's paid for So can I stick AVCS cams on the STi heads and still make happy power on the 35R?

b) Should I ditch the STi heads and sell them with the AVCS components for profit and use my stock WRX heads? The WRX heads flow nearly identical to the STi heads and the cams and mild porting will wake the heads up. However I will be forced to use cams other than GSC....will can I use them still?

How is my compression going to be affected with either of the head options? Pros and cons of each?


The rest is pretty straightforward.

Insight and opinions greatly appreciated. No bashing, bickering and worthless posts are NOT welcome. Lets keep this thread clean.

Thanks.

 

You can use the GSC cams in the WRX heads, you just have to plug the oil passage.

Matt

GSC dealer..

 

What's involved with plugging the passage? Any cons to doing so? Is it more beneficial for me to use my WRX heads? Will my compression be all out of whack?

I want this to be as simple as possible. It seems that stock compression motors are lasting a lot longer than the upped compression engines but that is just from the ones that have chimed in over the years.

Also if I sell the STi heads I bet with the AVCS stuff included, I can get a good chunk of the money for the cams back even without the valve covers.

 

I'd use the sti heads but ditch the cams and get GSCs. Leave all the avcs stuff hooked up. You just won't have any ecu control over the advance.

 

You just have to thread the cams and screw some plugs in, no real cons. My new motor is using WRX heads.

 

Leaving the STi heads on may be the best bet since I will have something to keep in the car while I get this engine ready.

All the AVCS stuff is in my posession but off the engine and I haven't a clue how to hook it all up.....this is gonna be fun! LOL

I may order one of those CD's off EBay that has the FSM on it.

 

Do what looks good... then if there's parts left over... it's probably wrong


I think I've seen some AVCS diagrams on NASTIOC when looking for other things... however finding them again might be an issue in itself.

 

send me a PM I'll send you a copy of the FSM, WRX or STi

 

I wish I had something to add to this thread but I'm just going to subscribe. Get the AVCS if you can. I'm not sure if the IAperformance.com AVCS harness works for USDM motors or just JDM motors but it was pretty easy to install. You'll definately need to get another ECU, I'm not sure what would work to control the AVCS, possibly an 06+ WRX ecu? I know the JDM ECUs are very finicky with regards to what year/ECU because the AVCS mechanisms themselves differ year by year.

You just got me thinking about the possibilities of wiring up your own standalone AVCS controller . . .

Seriously though, I'm not sure if the AVCS makes as much of a difference on the 2.5 but on my 2.0 its a night and day difference below 4K rpms.

 

I know AVCS helps with day to day driving but really on a 2.5L it really is just personal preference. From what I understand a GT35R on a 2.5L drives like the 18g on my 2.0L. I can definately live with that.

 

Bobby I am willing to bet the night and day difference that you feel in your car is the 9.0:1 compression the JDM motor has. I think the Version 8 engine was 9.0:1 compression. The stock USDM engine is like 8.2:1 or something close to that. Did you ever drive the JDM 2.0L without AVCS?

 

I think Will has a nice thread about plugging the cams.

 

HOW TO: (w/ pics) STI cams in WRX heads

http://forums.nasioc.com/forums/showthread.php?t=1356918&highlight=sti+cams+wrx+heads

 

IIRC the compression ratio isnt quite 9:1 but thats besides the point. To pass emissions I had SS flash my map onto my 02 USDM ECU which runs the motor perfectly albeit with no AVCS. Without AVCS the motor was noticeably laggier down low, the added displacement will counteract this. I gained a lot of respect for the AVCS system after rolling around for 500 miles without it. If you're worried about topend, AVCS advance goes to 0 beyond 6K.

If you're ever down this way again I can give you a ride and disconnect AVCS since mine is all spliced up with quick disconnects. Call up the guys at IAperformance and see if their harness will work with your car and what ECU they recommend you to run. I think some of the 2.5T motors out of FXTs or BajaXTs might have been equipped with a standard throttle instead of the DBW of STIs, I would think that an ECU from them would be able to control AVCS.

 

Even then that wouldn't do me any good and may as well get the Hydra if I wanted AVCS as my Ecutek is tied to my ECU.

 

I really would think the combination of the higher compression from the 2.0 heads paired with the higher displacement should make a huge difference down low where the AVCS would be working....I looked into it and you are right, the avcs system is tough to get working in our cars without hydra and for the little bit you gain down low, I really don't think it is worth all the issues and expense. Having looked at a lot of dyno sheets, there really doesn't seem to be a whole huge difference...maybe 20-30 torque under 3500 rpm. SS was going to try to dyno a car with and without to see what difference it made on the exact same set up, but I don't think it ever happened. Further, I think to really see the exact difference, you would have to have a map custom tuned for with and without, but it would be interesting to see!

I have decided to go with WRX heads for mine with the higher compression. Yeah, it can be bad, but I really think as long as you are conservative with the tune, it should be plenty safe. I say sell the Sti heads, get the wrx heads ported a little and get new cams. Hell, for the money you get for the Sti heads, you could probably pick up a spare set of WRX heads for like $200 and have all the work done on those while your 2.0 is in your car. Then just sell the 2.0 as a long block when you are all done with the swap and make more money on the sale of the 2.0.

 

I agree with you there Mike. It's very tempting to do what you suggested but it's also a very tough decision.

 

Hopefully SS and Doug both will chime in here with their opinions.....

 

Definately do the rods while you have it apart. They will become the weakest link no matter what pistons you go with.

 

Why didn't you?

Also LiquidForce what CR are you running right now?

 

Why is it so hard to get AVCS working on a USDM motor/ECU, when for a JDM motor you just need to splice 9 wires, or buy a $150 plug and play harness? Sorry if I seem hung up on this, it just seems like it shouldnt be as difficult as everyone is making it out to be.

 

You need an ECU capable of running it, and WRX ECUs can't do it. IIRC the US cam sprocket sensors are different design and they pickup in a different location as well. It gets whacky when you start mixing and matching heads and ECUs.

If you wanted to run 257 heads with AVCS, you either need to run a hydra/AEM, or the appropriate ECU. using a stock ECU would mean converting over to a DBW setup. its a giant PITA

 

There is that '06 STi wiring harness on here... Not sure what it would take to make it all work. I stand on my suggestion to take your longblock and make it a TopSpeed Road Race 1 (TSRR1) motor. That is:

1) block porting to spin a stock crank to 8,000 rpm all day, 8,500 for a drag pass, or a forged crank to 10k.
2) TS forged pistons
3) TS forged I-beam rods
4) special sauce ACL bearings
5) Full valvetrain
6) TSRR1 head porting
7) GSC cams

and some other stuff...

Siegel

 

To convert the wiring to use the STi ECu requires going to DBW and also requires meddling with the foot pedals and sensors and whatnot. NOT WORTH IT. I'd just as soon trade my car in and get myself a 2007 STi or ditch Subaru and get the Saturn Redline Sky.

 

Wahoo!! I think that kind of redline would make a GT35R viable on a 2.0.

 

It is not that it is so hard, it is that he would have to change his ECU thus loosing his tuning method...so that would have to be replaced, which means more money on top of more money. While he might get some back from the sale of the old ECU, it would not even be close to what it will cost to get a new one I would think. Add to that the cost of getting it to work, purchasing a JDM ecu or hydra....it gets expensive.

I am right with you there though...I just kind of did a cost benefit analysis and I came up with WRX heads with cams. It basically comes down to how much money you want to blow and what you have to work with to start with.

 

I'm with whoever said earlier to sell the STI heads and buy a spare set of WRX heads, equip them with cams and upgraded valvetrain and be done with it if you dont want AVCS. Liquidforce has proven what a good combo stock WRX heads can be with a decent cam.

 

LiquidForce has Version 6 JDM WRX heads with Version 5 STi cams or vice versa. However I think his JDM heads are identical to USDM WRX heads though.

I'm leaning hard towards selling the STi heads and getting a spare set of WRX heads.

 

I have 2 sets of wrx heads in excellent shape. Sell the sti ones for 1k+ and buy mine for 300.

 

No cracks around the spark plug threads either?

 

It would be nice I Tray got back to me......I sent him a PM inquiring.

 

I have a set that has absolutley NO cracks and on the other set there are very small cracks around the plugs. The heads with the small cracks were on my car and the cracks were there at 50k the first time I did a 2.5 swap. I ran them for another 50k before I got the new heads and never had an issue. The cracks had not grown any over that 50k miles. I would put them back on my own car without hesitation.

I will shortly have another set of heads but I don't know there condition yet.

 

LiquidForce I'll get with you as soon as I make my mind up and if/when I sell the STi heads. I think they are worth $1300 with all the AVCS components and the cam gears.

 

Bump for more in depth discussion......

 

For the power level you are making I don't see any reason to go any further than Pistons....Rods and Pistons if you want to be extra safe. I personally could care less about AVCS, for me it just isn't something I need. If I'm below 4000 rpms on a Road Course then its a warm up lap or I just screwed up.

 

At what power levels are the STi rods at danger? 550hp? 600hp?

 

Also Matt what CR is your new engine going to be?

 

Stock rods seem to fine to 600hp. Personally I wouldn't push them that far.

The CR on my 2.4 liter is about 12 to 1

 

12 to 1? :eek3: 2.4L :eek3:

I thought you used the 2.5L block? More info please? 12:1 is gonna be hard to tune for isn't it?

 

Nope the customer that wanted the 2.4 before ended up going with a 2.5 so I traded him for his 2.4 parts.

12 to 1 won't be hard to tune at all on VP import, my car will never see pump gas. If I run One Lap next year we will build another motor for the car.

Matt

 

Ah C16 gotta love it.

What is the recommend CR for a daily street car like mine. I may make my engine like LiquidForce. It's proven and reliable as this is still going to be my daily and will see many miles.

 

What is Mike running these days?

 

I would try and keep it below 9.5 to 1, Dan doesn't seem to have a problem tuning higher compression street cars. I can't speak for all tuners, maybe Scott and Doug will chime in on this as well.

 

Cobb suggested staying under 10:1 for a Subaru street car...

Siegel

 

What do you and Doug suggest running for CR? I'm thinking of 8.8 - 9.2 to 1

 

Okay so I'm going with lightly polished (basically just gonna clean up the casing flaws) WRX heads with GSC 272 cams and their recommended springs and retainers. The same Mahle pistons that LiquidForce has. Thinking of using the STi head gasket.

What's my CR going to be at? I don't want guessimates....I want proof.

 

Assuming a couple of things

I think stock head gasket thickness is 023
Dish on the Mahles is -22
WRX Heads are 49cc combustion chambers
Assuming that its a zero deck motor then the compression ratio should be
9.629809205144458 to 1

Now if you wanted to get it down to say 9 to 1 you could massage the combustion chamber to 54ccs and that would net you 9 to 1.

Head gasket thickness doesn't really change the compression ratio that much, going from a .023 to a .040 gasket will only change it from 9.629809205144458 to 1 ....to....9.613652076295265 to 1

Matt

 

That's where the problem lies. I'm hearing different things from different people. Grrrrrrrrrrr.

 

What are the other numbers you have heard.

Matt

 

Any where from 8.8CR to 9.2. Ron at Axis told me 9.2ish.