Engine questions, closed decks, STI's/ECU's???!!!!...

[villagehoppa]

Hi All, sorry if I'm being thick! What does closed deck engine mean? And also, If I got an engine from a WRX 02 to 05, as long as I have the loom and ECU etc, all should be ok!? Even if I purchased an STI WRX and kept the loom and ECU, I'm assuming all would be fine?? Just the engine not the complete car! Apologies if I am not understanding correctly.. Hope all the projects are coming nicely.... Cheers, J

[JeromeS13]

26527

As far as the engine/harness; as long as they match each other, it should work fine.

[villagehoppa]

Great! Thanks for that, I suppose a closed engine is best then as it's stronger? thanks for the info... J

[Pearldrummer7]

Great! Thanks for that, I suppose a closed engine is best then as it's stronger? thanks for the info... J

Yup, but if I remember correctly, it's only a closed deck on a few earlier cars, nothing today. That might be wrong, but I'm pretty sure the EJ205, EJ255, and EJ257 have open or semi open deck....

[JeromeS13]

Yup, but if I remember correctly, it's only a closed deck on a few earlier cars, nothing today. That might be wrong, but I'm pretty sure the EJ205, EJ255, and EJ257 have open or semi open deck....

From what I recall, only the EJ22 was fully closed. There is, however, a company that will modify the block and fill in the areas, making it a closed deck. Can't recall their name at the moment.

[tirod]

Closed deck means the cylinder wall is connected to the outer block. Open deck, it's free standing.

In open deck cylinders are reputedly capable of vibrating or moving under stress, like a slow speed tuning fork. That allegedly creates issues with head gasket seal that could cause failure. One modification is to install bolts to clamp the cylinder in place to keep it from moving. Others only use closed deck blocks as they are supposed to be stronger.

Because of the difference, we see a lot of open decks reportedly having blown head gaskets. Then again, they are largely all we have, so the likelihood is much higher, too. Like pushing a 5.0 Ford over 450 hp, engines have limits. From the factory's perspective, it's possible it's just casting the motor good enough, it's only a street driven car and why pay extra for more complexity when it won't make a few 10,000's difference in engine life? Plus, a running car is not a new car sale.

Like the small block Chevy, when you really look at the design, you discover decisions based on ROI, not performance. They are both far from a high performance design. We just get the induction system ramped up a bit and hand over the money.

[Pearldrummer7]

From what I recall, only the EJ22 was fully closed. There is, however, a company that will modify the block and fill in the areas, making it a closed deck. Can't recall their name at the moment.

I think you're correct. The aforementioned bolt to the cylinder wall to hold it in is relatively "common", but your best bet is a closed deck for high power. That said, you can easily make a reliable 300+hp to the wheels without much effort on these blocks as is. In my opinion that's plenty for an 1,800lb car. Cost per power, closing the deck likely isn't worth it. That said, I am no expert by any means and it's your build, so by all means find a closed deck and pop it in an 818!

[Rasmus]

To generalize, to make sure a frankenstein engine works with minimal issues make sure the heads, wiring harness, and ECU match. You can mix and match a bit between years but as long as the ECU can interpret the signal from and run the heads it's wired to, you'll have an easier time. Whatever short-block you bolt them on, the heads don't care.

[philly15]

this is correct, the ej22 is a closed deck. they did have some issues with overheating however due to the smaller cooling passage ways. however, in terms of shear durability i do believe the ej22t was the best block subaru made so far. i wouldnt worry about closed vs semi closed as much with this kind of build. most of the "issues" tirod associated with open decks arent as prevalent in subarus. the 2.0L ej205 is open, and usually have far less head gasket/rough running issues than the ej255/57 2.5L motors in the newer wrxs and the STi. i really think the 2.0L is much more smooth than the 2.5's and at some point ill be getting rid of my 2.5L for another 2.0 either an ej205 or maybe upgrading to a 207 in my 818. might even do some experimenting with the ej22t. but for this application, i dont think you have to worry about it as much.

[tirod]

Yes, in most cases it won't make a difference. What does crop up, especially with the 2.5, is how much cylinder walk contributes to the failure of head gaskets. Having just swapped in a "low" mileage EJ25 with single layer stock gaskets, it comes to mind. That issue is why used EJ25's are difficult to find in running condition, and it doesn't help that the stock SOHC motors weren't sold in the JDM. Makes older Foresters prone to scrapping out as the economic threshold is higher than just buying another.

Which is what I should have done . . .

[Pearldrummer7]

however, in terms of shear durability i do believe the ej22t was the best block subaru made so far.

Except for maybe the new FA20! Can't wait for the first person to put one of those in an 818!

[ssssly]

EJ22s and some EJ20gs are closed deck. Keep in mind though that all the closed deck engines are phase 1. But as long as you run phase 2 heads and use phase 2 sensors, the block won't matter ECU wise. The coolant crossover and PCV hard lines are also a bit different but not a big deal. Stretch a couple hoses and everything is fine. And you have to pay attention to head gasket thicknesses for what compression you want to run, because the phase 1 head compression chambers are different than the phase 2.

The biggest up side is reduced cylinder deformation under load. And the EJ20G blocks out of the STI RAs have piston oil squirters as well.

If you are trying to build a super high horse power engine then these things will benefit you. If you are going to be staying around stockfish power levels they aren't really a big deal.

Ej205 engines are open deck. 207s and 255s are semi closed. I have however seen some 703 casting semi closed come out of 06-09 wrxs. These would technically be EJ207 blocks but are sold as 205 in the states for some strange reason. They are rare and seemingly completely random, but they are out there.

Bottom line, if you are planning on staying under 400hp don't worry about it. And use MLS head gaskets either way.