Hybrid EJ Engine Advantages

[Louisromersh]

Hi everyone,

So I know this question will bring a verity of answers just because you all have your own opinions when it comes down EJ205 vs EJ257.

But I want to know what are the advantages of building a Hybrid EJ engine with a EJ25 Short block and using EJ205 Heads?

Then is there any down falls or problems that can occur when doing this engine build combination?

Also what would be a reasonable goal for horsepower for this engine?

Thanks in advance.
Louis

[Mechie3]

Only advantage is short term money savings. People with a 2.0 want to upgrade to a 2.5 but don't want to spend $1k in 2.5 heads plus potential other changes (ECU, sensors, etc). They are more prone to detonation. Several tuners I know off refuse to tune them due to this. The best way to go is to get them CNC'd to match the head chamber to the bore if you want to keep the 2.0 heads. I forget the cost of that but it wasn't much less than going 2.5 heads.

[Buzz Skyline]

I met a guy rallycrossing one in an Impreza 2.5 RS, and it had a lot of low end torque. He claimed that was why he did it. I'm not sure I'd want any more low end torque for an 818. It's already too easy to light up the tires in my car with stock EJ205.

[Tamra]

We paid $500 to have our heads resurfaced and chamber matched to the 257 block (otherwise compression will be very high). We had lower quotes, but went with one of the most respected shops.

It lets you run an EJ205 wiring harness while upgrading the short block. I've only heard of the detonation problem when the heads aren't chamber matched. If the heads are chamber matched, tuning a hybrid motor is not a problem. It's only an issue when stock 205 heads (not chamber matched) are used, because the tuner has to tune around the extremely high compression. Even then, it isn't impossible, it just takes a more talented tuner.

[STiPWRD]

I'll be running the hybrid as well. As others have mentioned, the EJ205 heads have a smaller combustion chamber so the compression ratio will increase if you use them on an EJ257 block. I didn't get my head chambers enlarged but I am using hybrid specific forged pistons from JE that effectively do the same thing - reduce compression ratio back to 8.5:1. This is my first time building a motor so we'll see how things work out. I've heard that as long as the compression ratio is addressed and the engine is properly tuned, the hybrid is just as reliable. The advantages are greater power potential, torque and no wiring changes.

[phillig]

I'm using the same setup as STiPWRD. EJ 205 heads, JE pistons, and a new EJ257 block. Andrewtech in Gaithersburg MD built my engine for me. A great shop and even better people there. They've been a big help on my 818 project.

[longislandwrx]

The advantage for many is after a spun bearing or other failure, a brand new factory assembled Sti block can be scooped up at the dealer for cheap. a $500 master gasket set with some thick head gaskets and you are back in business.

It's not ideal but it's quick and dirty.

If you are doing a full build, you have some options, as others have said.

[rallysteve]

we built a engine for a 93 legacy track car. 2.2 turbo block, 2.5 ported and polished heads 05 RS intake, with a aLink G3 stand alone. Eagle rods and Wiseco pistons. 290hp 345 torque at a local Cobb dyno.

[Louisromersh]

Thanks all for the information I think this helps me with my planning of my build.

Thanks

[tofer9458]

Only advantage of a hybrid I know of is the fact you don't have to change wiring for the avcs so it was a easy swap in a wrx without changing much and netting you an extra .5 of displacement I personally never been a fan of the 2.5