planing on building a second motor

[93forestpearl]

I was making more power with my 22T heads and Delta cams than more boost and a larger turbo on 25D heads.

thats because your compression ratio took a huge hit

That doesn't explain the major discrepancy in air/fuel ratio. Nor do you comment on the obvious difference in those two camshafts. Also, the other engines I referenced had custom pistons and were in the 8.2-8.5:1 compression ratio ballpark. Lack of compression does not adequately explain a 300whp wall between all of these variations.

I was comparing an engine with 22T heads and 23 psi from a GT2871R to a engine with 25D heads and 28 psi from a GT3782. If you look at the compressor maps, the GT3782 was pushing over 10 lb/min more than the GT2871R, meaning it should have been making around 100 more hp. It wasn't.


This is not an unknown problem. All of the engine builders I've discussed this with agree. Forced-induction engines need appropriate cam(s) to make proper use of the pressurized intake charge. I'm surprised this is even a debate.

[fasterthanyou]

most of the cam specs i found were aftermarket, but i grabbed this from nasioc
Factory specs for 1997-1998 '4' cams (so not for HLA):

USDM EJ25D

Intake opens 6° BDTC
Intake closes 50° ABDC
Exhaust opens 54°/30° BBDC
Exhaust closes 10°/10° ATDC
Overlap 16°

JDM EJ20G

Intake opens 8° BDTC
Intake closes 52° ABDC
Exhaust opens 52° BBDC
Exhaust closes 8° ATDC
Overlap 16°

JDM EJ20K STI

Intake opens 10° BDTC
Intake closes 56° ABDC
Exhaust opens 56° BBDC
Exhaust closes 12° ATDC
Overlap 22°



i am just saying that i dont think it is neccessary to change cams. i do see the "obvious difference" in the cams. but you cant tell overlap from that pic! it only shows duration and lift.i dont know why you would hit a "wall" at 300 HP. that makes absolutely no sense, but i am sure it would not be from cams alone. if you had 8.5 to 1 on the stock motor it would be around 7 to 1 with 2.5d heads. you would need some serious custom pistons to run 8.5 to 1 with 25d heads.

engine management?

i dont see why everyone thinks that "overlap" is such a big deal. its hardly the issue on deciding between stock cams. besides turbo cams have more duration anyway. N/A cams are set up so they are open the same time but you really need aftermarket cams if you want big power. i am sticking with 25d cams because i dont want to pay a couple hundred for 20g cams or 1000 for aggressive cams. 25d cams work the best for my application. a stock 25d longblock(stock comp ratio of 10/1) with a turbo.

i agree you have to have the right combination of parts for each application, but there are so many factors that come into play

[Delta Cam]

most of the cam specs i found were aftermarket, but i grabbed this from nasioc
Factory specs for 1997-1998 '4' cams (so not for HLA):

USDM EJ25D

Intake opens 6° BDTC
Intake closes 50° ABDC
Exhaust opens 54°/30° BBDC
Exhaust closes 10°/10° ATDC
Overlap 16°

JDM EJ20G

Intake opens 8° BDTC
Intake closes 52° ABDC
Exhaust opens 52° BBDC
Exhaust closes 8° ATDC
Overlap 16°

JDM EJ20K STI

Intake opens 10° BDTC
Intake closes 56° ABDC
Exhaust opens 56° BBDC
Exhaust closes 12° ATDC
Overlap 22°



i am just saying that i dont think it is neccessary to change cams. i do see the "obvious difference" in the cams. but you cant tell overlap from that pic! it only shows duration and lift.i dont know why you would hit a "wall" at 300 HP. that makes absolutely no sense, but i am sure it would not be from cams alone. if you had 8.5 to 1 on the stock motor it would be around 7 to 1 with 2.5d heads. you would need some serious custom pistons to run 8.5 to 1 with 25d heads.

engine management?

i dont see why everyone thinks that "overlap" is such a big deal. its hardly the issue on deciding between stock cams. besides turbo cams have more duration anyway. N/A cams are set up so they are open the same time but you really need aftermarket cams if you want big power. i am sticking with 25d cams because i dont want to pay a couple hundred for 20g cams or 1000 for aggressive cams. 25d cams work the best for my application. a stock 25d longblock(stock comp ratio of 10/1) with a turbo.

i agree you have to have the right combination of parts for each application, but there are so many factors that come into play

While some of your information is relevant, some is also mis-leading. It is obvious that your friend has not shared all of his knowledge with you.

When boosting and running turbo engines over-lap is everything. You run the correct overlap and you'll make huge power. You run too much over-lap and all your power goes out the exhaust... POOF!

The specs you "snagged" don't tell the whole story. Lift and duration do matter. Over-lap does matter. When you have too much overlap you will make less power. Not enough over-lap and you will build excessive cylinder pressure which can lead to blown head gaskets and other catastrophic failures.

And, 25D head suck until you port and polish, That is why everyone uses other heads in their place.

The best thing to do is run an adjustable cam gear. Unfortunately, no one makes them for Subaru's. That would make just about any cam feasible in a performance engine build!!

[93forestpearl]

Thanks Delta.



fasterthanyou,

Engine management for the three cars other than mine was the Hydra 2.6. That system provides enough control, especially when Phil from Element Tuning tunes two of them and was scratching his head.


My system runs a Link Plus G2, but it really doesn't matter. Fuel is fuel, timing is timing. Just a matter of interface.

[fasterthanyou]

ok, i am not saying that lift, duration, and overlap dont matter. they do.

they do make adjustable timing gears for subaru's by the way.

and the stock 25d heads flow way good! they dont suck at all stock.
http://users.erols.com/srweiss/tablehdc.htm#Subaru

and i am saying, when choosing STOCK cams, i dont think it is neccessary to change. if you want power spend 800 or more for agressive turbo cams. but if you are looking for 400 HP you would do that anyway.

[Delta Cam]

OK, I know of adjustable tensioners but I have never seen adjustable gears. Can you share this source?

[fasterthanyou]

google it.


http://realstreetperformance.com/store/ ... -2249.html

[Delta Cam]

google it.


http://realstreetperformance.com/store/ ... -2249.html

Thanks, I had not seen that before.

[Falken-18c]

http://www.ebay.ca/itm/Subaru-EJ22T-Bil ... 3cbd19725e
so would this be the way to go and what heads would be best and how much power would you make with a vf39 are bigger with a good tune

[BoostedSubie]

Thats a lot of money when you could just buy the pistons for 500 and a sti crank that is 300. I think a billet crank is a little much unless you plan on making more than 600hp. The factory Subaru cranks are strong (forged).

[Falken-18c]

Thats a lot of money when you could just buy the pistons for 500 and a sti crank that is 300. I think a billet crank is a little much unless you plan on making more than 600hp. The factory Subaru cranks are strong (forged).

yea your ways better lol cheaper any ways
so how much would this be to do every thing 3-5grand

[BoostedSubie]

I wasn't saying it was better, it would be awesome to have all that. I guess you just have the pocket book to afford it, I don't, with a family to support. Have fun with that, can't wait to see how it turns out. I'd rather see someone spend the money on building the 22t rather than the played out 257.

[Falken-18c]

lol dont have the money right now for it as i just got back to work but yea ill probly get that later. Maybe. im just lucky that i dont have a family to suport. Almost lol the women i was with wanted a family but i ran lol no kids for me at the age of 21. i need to grow up and mature alot be for i have kids would have been horible for her lol would of had 2 kids if i went along with it the baby then me. just so no one misleads she never had a kid i never ran out on a family i ran as soon as she said she wanted kids lol