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Old 07-29-2001, 03:35 PM   #1
triXXXter
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Question Why turbo charge 2.0 vs 2.5?

I know this is the NA area but still it concerns our 2.5s. Why does Subaru choose to Turbocharge the 2.0L other than the 2.5L that we all love? More Displacement more power. I have seen a guy's Turbo 2.5RS that was the exact same as the setup on a stock WRX (same turbo size too) and it had more HP. Just a curious question.
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Old 07-29-2001, 03:46 PM   #2
supermarkus
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Do a search on this topic, it's been covered many times over and explained better than I can do. In my opinion it boils down to the 2.0 being able to take more boost pressure because of its closed cylinder deck design. The 2.0 will stand up better to higher boost. You almost never see a person with a 2.5 holding more than 10psi boost without having some sort of built up cylinder deck. It also may be a case of not fixing what ain't broke, the 2.0 has been turbo for a looooong time.
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Old 07-30-2001, 09:57 AM   #3
impr3zaturb0
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I thought that newer EJ20 are also open deck.
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Old 07-30-2001, 10:27 AM   #4
efoo
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Yup. They are. The STi v. III in 1996/97 was the last closed-deck 2.0L engine. And even then, not all of them are closed-deck - I've helped tear one down and to our surprise it was an open deck block.

This topic has been beat to death many times already, so doing a search will yield some very good discussions backed up with good hard facts (i.e., pictures of blocks, dyno charts, etc.). Please read those threads before making assumptions and making unfounded statements; it only just serves to add to the confusion.

-Edwin
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Old 07-30-2001, 10:49 AM   #5
supermarkus
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How about this? Here's something you probably never see on these boards.

I stand corrected.

I never see anybody admit to being wrong about these kinds of things since everybody seems to be an expert here. I learn something new every day. I never read that they switched to open decks. Hmmm... more searches!!! I love this board. So informative. For the record, I thought I had read enough of the threads pertaining to this. Looks like I missed a bunch as usual. But that's to be expected with the gigs of info to be had out there. Thanks for setting me straight.

<bows in humility>

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Old 07-30-2001, 11:04 AM   #6
efoo
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Eh, no one's perfect. But you're completely correct about 99% of people not being willing to admit they are wrong, especially on this board, unfortunately. For that my hat's off to you, and I hope that I'm also corrected when I'm wrong; I would much rather suffer a bruised ego than blow up my car due to wrong assumptions about what is inside.

The newer EJ20s (what you have in your WRX) is a semi-closed deck; if you can find a sale brochure from your dealership that happens to show a cutaway of the engine, you'll see what I mean.

In any case, the weak link in these cars isn't the engine. It's the transmission. A turbocharged 2.5L engine generates far more torque at lower rpms than a 2.0L turbo engine, and that tends to break gears even sooner. At 10psi of boost, turbo 2.5L engines can put out 260-280 wheel hp and almost 300 ft/lbs of torque easily depending on tuning - why spend money on the engine block to get higher boost levels if you're going to shred your transmission anyway? Basically, the open/closed deck issue is a non-issue, at least until the transmission has been upgraded to take the power.

-Edwin
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Old 07-30-2001, 03:13 PM   #7
SYMSWRX
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Smile !!

I think the reason why subaru put the turbo in the EJ20 but not EJ25 is because in japan the car reg and insru are go by the engine size , the people buy the car with 2000cc or lower will save them a lot of taxand lis fee !!!! that's why a lot of car from japan are 2000 cc or lower !!! just like our impreza and 240sx !!!
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Old 07-30-2001, 03:23 PM   #8
DeliciouSpeed
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WRC has a engine size limit, it's 2liter. And the cars used to have to be based on production cars so thats why the two liter in the rally car and the street car. Now that manufactures have more freedom with what cars they field, exp. AWD Ford Focus(no production AWD focus anywhere).

Ken
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Old 07-30-2001, 11:53 PM   #9
LVSUBARU
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You are absuloutly correct, sir!!!!!!!
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Old 07-30-2001, 11:57 PM   #10
Penphoe
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Default Also abou torque....

Don't forget about the multiplying that happens to the engine's torque numbers when it goes through the transmission. With the "low" gears being so low, they multiply the torque of the engine quite a bit!

LaterZ!
Darren!!
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Old 07-31-2001, 12:38 PM   #11
S_rangeBrew
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Default Re: Also abou torque....

Quote:
Originally posted by Penphoe
Don't forget about the multiplying that happens to the engine's torque numbers when it goes through the transmission. With the "low" gears being so low, they multiply the torque of the engine quite a bit!

LaterZ!
Darren!!
Yeah, when DSM'ers tried making the bore bigger in the 4G63, they just ended up breaking the tranny with the massive torque. They only took it from 2L to 2.2L.

I think everyone on this board should go over to dsm.org and read everything there before "reinventing the wheel" here.

-SB
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