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Old 02-05-2001, 04:40 PM   #1
HamFist
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Post Complicated cylinder head + aluminum rod questions

Ok. I'm still on track for project N/A. I have a few questions for people that have ported the heads. Anyone who has done a mild port cleanup...to a hogging of the ports...I'd love to hear from! Making them too big is bad for street, but a higher lift cam makes better use of those ported heads. More duration helps with the flow, but too much is still bad. I think I read in SCC a few years ago, that a four valve head will actually LOSE flow with too high a lift. The valves would shroud each other beyond a certain point. I've heard of ports on Subie's, Porche's, and VW's big enough to fit a soda can into. That's huge! I'll more than likely be doing hand porting, so trey's heads are out of the question. Peak power for this buildup is planned for about 8k rpm.(N/A at 8000rpm = bad ass!!!) New valvesprings, billet cams, titanium valves, and retainers round out the cylinder head parts.
Also, for the bottom end, knife edging + balancing the crank is planned, but I'm not sure about aluminum rods. Are they bad for street duty? I have no experience with them. All I know is that they lighten the rotating assembly and let it rev higher.

Let 'em fly ya'll!

Gary
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Old 02-05-2001, 06:57 PM   #2
XT6Wagon
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Get good forged steel rods. Aluminum ones have serious problems even in race duty, and I hope I don't have to explain why Ti rods are flat stupid unless you have buckets of money and need 1(one) more stinking HP.
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Old 02-06-2001, 12:37 PM   #3
HamFist
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!bump! anyone else? I knew titanium rods weren't worth it . I could put that money to more use. I kinda doubted I'd get much of a response on this. Not many people really have a BUILT impreza other than just a turbo.
IF it were a WRX with the factory turbo and low compression pistons, I probably would worry about any of this .

Gary
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Old 02-06-2001, 02:32 PM   #4
svxtrem
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You know, I really hate to rain on anyone's parade, but this N/A route is not economically feasible, nor is it as easy as you might think to make horsepower just by RPM. You really need to do the math. The stock N/A 2.5 (at least for '99) makes 166 lb/ft at 4000. That translates into 171 CFM and 98% VE. If you take a 2.5 liter engine, running at 8000 rpm, at 100% VE (volumetric efficiency) on gasoline with 10:1 compression you will see 348CFM, or about 258 horsepower. If you up the compression to 11.5:1 (and can still run on pump gas), you might see 274 HP. However, there is no way you are going to do this with stock manifolds, cats, and any type of streetable cams. This is NASCAR territory. This does not mean that you cannot do it, but it just isn't worth it.
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Old 02-06-2001, 02:42 PM   #5
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Actually NASCAR volumetric efficiency is more in the realm of 120% if I recall correctly.

Care to calculate the VE for a 1.8L making 170HP?
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Old 02-06-2001, 02:44 PM   #6
svxtrem
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ColinL- what's the compression ratio and the RPM?

[This message has been edited by svxtrem (edited February 06, 2001).]
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Old 02-06-2001, 03:01 PM   #7
HamFist
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Do you realize I'm the type who likes to do stuff because other people told me i couldn't do it ? 250-275ish is about what I expect. Downdraft injection will be a whole different ball game.
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Old 02-06-2001, 03:15 PM   #8
ColinL
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svxtrem, 10:1 and 7600.
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Old 02-06-2001, 03:26 PM   #9
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ColinL
1.8 liter (1800 cc) 7600, 10:1 compression, 170HP = 95% VE. Pretty respectable.
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Old 02-06-2001, 05:49 PM   #10
S.Damery
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Burninrubber,
More power to you for your N/A buildup I think it's a neat challenge. Keep us updated!
-Shawn

[This message has been edited by S.Damery (edited February 06, 2001).]
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Old 02-06-2001, 06:55 PM   #11
P.K. Motorsports
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svxtrem - this is most definitely not NASCAR territory. I have seen firsthand a 3SGE motor (originally 63 hp/liter) modified to make 73 ft-lb/liter at 8000. A B18B makes 72 ft-lb per liter stock and a B16B makes 73. I've also seen several very streetable (in fact very driveable) modified B18Cs which made 75-77 ft-lb/liter at 8000. BMW makes M cars which come from the factory putting 75 ft-lb/liter at power peak and the M3 can be modified more at 8000. The S2000, qualifying as a ULEV, makes 80 ft-lb/liter at power peak but I've seen B18Cs which retain a lot of streetability built to make 80. Spoon Sports had a B20 churning out 83 ft-lb per liter back in '98 which was still streetable.

My point with this long expository is that with the level of work Burninrubber is planning there is no reason to believe that he won't succeed in elevating his EJ25 to a level which has already been reached and exceeded, not in NASCAR but in street-driven, even emissions-passing small-displacement engines at the same planned RPM range. If he gets 75 ft-lb per liter at 8000 that's a cool 281 hp.
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Old 02-07-2001, 01:09 AM   #12
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My stuff's out of the question, eh? Too bad, I just had some new stuff made that would be right up your alley. Valvesprings, Ti Retainers, even bigger cams....

Oh, and my heads are hand ported, not CNC'd, so you get better flow out of them.

Cheers,
Trey
CobbTuning.com
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Old 02-07-2001, 01:28 AM   #13
HamFist
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Hehehe...don't take it personally, Trey . I was referring to your cylinder heads. I can do mine for less than the 2k. Have you tried a radius job on the vaves yet? Pistons have been quoted to me at 750...cams at 500-600 a set (billet). If you can get me a price on titanium valves (undercut?), springs, and retainers, that would be VERY cool . Dual wound valvesprings were the only ones I was aware of. Is triple wound overkill? I don't want to increase the mechanical stress created by the parts very much. Wearing down cam lobes, replacing valve springs after every run...none of that seems appealing. 400 hp N/A sounds nice...but not at 12000rpm on a street car!!!

Cheers!(clink)
Gary
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Old 02-07-2001, 06:56 AM   #14
svxtrem
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I didn't say he couldn't do it, just that it wasn't economically feasible. However, if that's what turns you on, go for it. In answer to the NASCAR question, those engines are 358 ci with 12.5 compression putting out ~750 hp at 8000 rpm on special 110 octane fuel. ColinL is right, this is about 120% VE. (I had 8 psi of boost that I forgot to reset to 0 in the program before the edit!) In answer to the streetable question, any engine that allows some sort of variable valve timing (ala VTEC) can be more streetable than a fixed cam system.

[This message has been edited by svxtrem (edited February 07, 2001).]
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Old 02-07-2001, 08:51 AM   #15
HamFist
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A solid 250hp is all I expect before the downdraft injection. If it makes 280...COOL! But, the engine has to be built first. The stack injection should put it into the 12's after tuning. There are a few all motor 12 second imports. I've only heard of them being Mazda rotaries, nissans, and hondas, though. Why NOT a subaru? It's got the biggest displacement, aside from the nissan 2.7 I4. I think it's going to be fun. Expensive? Yes. But, 12's are 12's! All motor is just more impreZZive .

Gary
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