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Old 03-26-2011, 01:50 AM   #26
Wrencher86
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Thanks! I didn't know what IDC meant, I'm used to talking about injector pulse width in milliseconds. Most of the cam stuff I knew at one time or another, except for the lift difference between stock, Subaru performance and race cams.

I do know first hand about making sure all your parts work together, though. When I was in tech school I rebuilt the motor in the '77 Buick I had. Got it bored .030 over and bought a one-up from stock cam (that's what the machinist recommended, I still don't know exactly what that entailed). Put it all back together with everything else 100% stock and it ran like crap until the day I finally junked it (the brake lines rusted out and the gas tank straps rusted off). I was pretty bummed.

I don't know what the difference is between static compression and dynamic compression. I'll look that up sometime when I'm not falling asleep. (If you don't have anything better to do, feel free to explain here. )

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Old 03-26-2011, 01:53 AM   #27
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Static compression is what you get from doing the math to compare the volume at bottom dead center to the volume at top dead center. Dynamic compression is what you get when you actually run the engine and real-world effects like manifold pressure, volumetric efficiency, intake/exhaust valve timing, and other things are factored in.
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Old 03-26-2011, 11:13 AM   #28
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Tom at TWE has been promoting his newest "stage 2.5" cams to me big time. Says you need the upgraded spring kit because of the lift.

He also claims not only do they up the power, but they increase fuel economy. He fully admitted that this "sounds too good to be true", but at the same time he said it took a lot of r & d to get to that point.
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Old 03-26-2011, 02:10 PM   #29
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Something in between like a 220 or 230 duration is a very good fit for something not specifically race geared. There's a program called Engine Analyzer Pro. You can run it free for 10 days fully as a demo, and then it will lock itself (modify code) till you pay. If you take the time to accurately plug in the EJ25 numbers and start playing with things, you will find that cams in the 220 to 230 range tend to fair very good in terms of top end performance while retaining efficiency down to 3k rpm (cruising). The 240 and 250 kind of duration gets a bit high and is geared for top end only. This makes something like the Stage 3 cams a bit of a compromise but the Stage 2.5 cams an interesting solution. EAP is simply a software program though. It's useful for rough guidelines. It's nice that we have companies like TWE really trying to push what these motors can do.
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Old 03-28-2011, 11:26 AM   #30
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BRR... yes more aggressive than TWE's. i only know the lift and they won't share any other specs as they are proprietary to the engine builder. I may be doing head work later on, but that will be after the turbo goes on. Not sure about intake manifold, but may try the 2007+ impreza/legacy N/A version. it has a larger plenum than mine and looks like the runners are slightly bigger.

patrick... what other "dramatically cheaper, proven" options do you mean?

williaty... how do you know they are not making any more power than anyone else is? proof or anything to back that up?
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Old 03-28-2011, 01:31 PM   #31
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Quote:
Originally Posted by PA-Outback2000 View Post
williaty... how do you know they are not making any more power than anyone else is? proof or anything to back that up?
Look at the plots published by them or buy their customers. Compare them to plots published by other shops or other shops customers. They're all within dyno-to-dyno variation.
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Old 03-28-2011, 01:35 PM   #32
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Originally Posted by PA-Outback2000 View Post
i only know the lift and they won't share any other specs as they are proprietary to the engine builder.
Right there, that's a BIG red flag. What they said is utter bull****. They should, at MINIMUM, tell you lift and duration for both intake and exhaust. They really ought to also tell you lobe separation angle without you having to ask. If you ask, they should also be willing to talk about acceleration and jerk rates and other more detailed data.

Why? You need all of those to make an informed decision about your engine build. They're also not "protecting" anything other than their ability to snowball you by being secretive. If someone wants to copy their cams (and no one does ), all they have to do is get their hands on a set and a computer cam profiler will be able to profile those in a few minutes.
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Old 03-28-2011, 02:16 PM   #33
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So you are going to turbocharge a vehicle with a super aggressive race spec. NA cam installed? Sounds like their engine builder expert guy is giving you really really good advice there...
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Old 03-28-2011, 02:26 PM   #34
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Quote:
Originally Posted by Matt Monson View Post
So you are going to turbocharge a vehicle with a super aggressive race spec. NA cam installed? Sounds like their engine builder expert guy is giving you really really good advice there...
Just read that post about adding a turbo.

[yodavoice]End poorly this will[/yodavoice]
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Old 03-28-2011, 02:40 PM   #35
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Originally Posted by Matt Monson View Post
So you are going to turbocharge a vehicle with a super aggressive race spec. NA cam installed? Sounds like their engine builder expert guy is giving you really really good advice there...
Oh jeeze, I hadn't caught that he+xcell were stupid enough to blow their boost right out the overlap
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Old 03-28-2011, 03:47 PM   #36
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BRR... yes more aggressive than TWE's. i only know the lift and they won't share any other specs as they are proprietary to the engine builder.
Which is utter crap. There's not a chance I'd pay someone $2000 for cams that they won't even tell me the specs on. "Trust us, they're good." I've done two custom cams for my Mustang - one for the original 302, one for it's current 357. Both were done by Flowtech Induction. I have cam card files in Word for both. Ed Curtis, who is FTI, just asked that I not share the numbers, as they're his custom grinds. And really, there's more to cam design than just the lift and duration numbers. Those numbers don't tell you what the ramp rates look like, which is a key aspect of the cam design.

Quote:
Originally Posted by PA-Outback2000 View Post
I may be doing head work later on, but that will be after the turbo goes on.
So you're spending all this money on N/A cams, and then you're going to turbo it?

Quote:
Originally Posted by PA-Outback2000 View Post
Not sure about intake manifold, but may try the 2007+ impreza/legacy N/A version. it has a larger plenum than mine and looks like the runners are slightly bigger.
It's actually 2005+, just to ease your search for parts. That path is not without hurdles.

Quote:
Originally Posted by PA-Outback2000 View Post
patrick... what other "dramatically cheaper, proven" options do you mean?
As already mentioned, Delta and TWE. Although Delta has their standard grinds, they'll also do other grinds if you feel their normal offerings aren't enough for you.
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Old 03-28-2011, 04:45 PM   #37
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yes i will be turbo-ing the car. whether i take a middle step and do 6psi on the current open deck or go right to a semi-closed STI 2.5 shortblock with 17-18psi, i am not sure yet, but the cams will definitely be in the car when the turbo is on. it is all part of my project.

xcceleration doesn't considered these cams "race" cams. they designed the maximum potential into the cams, meaning the are they biggest lift u can get without internal cam area modification. they were designed to idle properly with not much "lope", but u still can hear it in the right idle rpm.
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Old 03-28-2011, 04:48 PM   #38
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The point Matt brought up is that NA cams and turbo cams have to be designed entirely differently. The exact things that make a good NA cam make a bad turbo cam.

Cams are solved science. There's no secret sauce, no mysterious techniques. All of the innovation in cams in the last 10 years has been better, faster, and cheaper ways to design and produce them.
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Old 03-28-2011, 04:54 PM   #39
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Only aggressive cams counteract what you would look for in a good turbo cam. Does your Xcell know exactly what your goals for the car are?


EDIT: Beaten to the punch above =(
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Old 03-28-2011, 05:29 PM   #40
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Quote:
Originally Posted by PA-Outback2000 View Post
xcceleration doesn't considered these cams "race" cams. they designed the maximum potential into the cams, meaning the are they biggest lift u can get without internal cam area modification. they were designed to idle properly with not much "lope", but u still can hear it in the right idle rpm.
Wat45? What the hell are you talking about? They aren't race cams but they are designed for the maximum potential and biggest lift? Is this a freaking informercial? You aren't talking to a bunch of methed out wastoids at 2 in the morning on cable. You are talking to people who do this stuff recreationally and professionally...
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Old 03-28-2011, 07:55 PM   #41
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I don't get how they can be more aggressive than TWE's race cams. 250 degrees is a lot for these motors since we aren't exactly spinning to 10k here. Unfortunately, I don't have any real world experience since I am a poor college student and do not work in the engine building industry. I've at least gone through some effort to understand what's available and what's appropriate for various setups from my own interests on building up a EJ25 motor and seeing what one can squeeze out of one of these things. Most of my experience only comes from reading up on as much as I can find on the internet and using engine modeling software to at least simulate these motors to some degree and understand what's appropriate for certain goals, so I'm not too far off when pursuing my goals. At the very least, I like to have a reasonable understanding of what's available and what should work for these motors. For myself, this means me not wasting money on things, not having unrealistic goals, and understanding around where I should be for part design or purchase. Cams are one thing I've toyed with some.

Frankly, I have no clue what you hope to achieve with your motor. I have a rough understanding of what a reasonable EJ25 can do in terms of revving and what general cam sizing is required to support that operation. TWE's race cams are on the high end of things. You're looking at a cam that supports a motor that will rev out to the limits of what the hardware can do without blowing up. The 250/240 cam they offer should support +8k rpm fine. Much of your other issue revolves around modifying the heads, and doing something with the intake manifold to actually be geared right for that rpm range.

The more you describe the Xcelleration cams, the more I see them as a mild torque cam, low duration but high lift, which is fine except these motors don't really need the lift. You are planning to turbo the car anyways, so I don't know why you're looking at any NA spec cam at all. However, my understanding is that a big turbo cam ends up more like a NA cam. I know with Engine Analyzer Pro, I found it would give me better numbers running TWE's NA race cams versus the common BC 272 turbo cams the turbo folks always use. However, it's just a software program and is still approximating a lot of things.
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Old 03-29-2011, 08:32 AM   #42
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williaty and matt monson... these cams r the SAME ONES as in xcceleration's own 1999 2.5rs, both the high compression and supercharged version of the SAME ENGINE. the only difference between them is that he started with an N/A block and then switched to STI shortblock when boost was added. he is also running 9:1 compression not 8.2/8.5:1 like STI's.

here are the 2 links...http://xcceleration.com/imp-gallery-rs.htm - N/A
http://xcceleration.com/imp-gallery-rs.sc.htm - supercharged

the dyno graph listed in the SC link was sun with 20psi of boost. the engine is now running in it's "sweet-spot" at 25psi. this supercharger is a positive displacement twin screw type.

if you take a look at their swiss race car... http://xcceleration.com/imp-gallery-...wiss.gt35r.htm and compare the dyno graphs, the overall shapes are close between the 2 versions of forced induction. the more impressive of the 2 curves is the torque curve. this is accomplished by combining their cam design with their custom head work to make the ultimate torque machine.u can say single cam vs. twim cam, but the effect is the same and the theory behind crafting the head work is the same. it is very rare to see that kind of dyno curve with that much power and more importantly torque come out of a 2.5L subaru.

BRR... what is the point of modifying any car?? more power and performance. different people have different ways of doing things and i just happened to choose theirs. their service is 2nd to none and they ALWAYS return phone calls, even after hours and on weekends. i feel they offer an overall great product and have the reliability, experience, and service to back it up.
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Old 03-29-2011, 08:58 AM   #43
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Not that I'm eager to get into this thread, but the one thing that keeps giving me pause, is the notion that it's a high performance NA cam that also is a good cam profile for boost. That just doesn't make sense, because it's not "normal". A Hi-Perf NA cam is not the same as a Hi-Perf turbo cam and not the same as a Hi-Perf FixedDisp SC cam.

So, one of 2 things is wrong here. Either you've misunderstood what the purpose of the cam is (boost targeted or NA targeted) . Or the xcceleration guys are feeding you nonsense.
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Old 03-29-2011, 10:11 AM   #44
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the cams i am getting are the SAME, specs and everything, as the ones in his SC car and other customers have used them in their own SOHC turbo applications. the cams are "hot" cams, but r designed for overall performance, no matter if it's N/A or boosted. boosting only accentuates the cams performance, giving you more power than if the cams were stock.
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Old 03-29-2011, 10:26 AM   #45
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You're missing the point.

Quote:
Originally Posted by PA-Outback2000 View Post
... i chose them because they have better/more aggressive specs than delta, TWE, and others. ... and are specifically engineered for the N/A's. these cams are the maximum lift u can fit in the heads w/o internal cam chamber modification.
Quote:
Originally Posted by PA-Outback2000 View Post
the cams i am getting are the SAME, specs and everything, as the ones in his SC car and other customers have used them in their own SOHC turbo applications. the cams are "hot" cams, but r designed for overall performance, no matter if it's N/A or boosted. boosting only accentuates the cams performance, giving you more power than if the cams were stock.
You see, these quotes are somewhat contradictory.
Quote #1 implies that they are a very aggressive N/A specific cam.
Quote #2 now implies they are an overall performance cam regardless of their use.

You can't have your cake and eat it too. A "max aggressive NA" cam is NOT an ideal cam for a Turbo, nor a Supercharger. If you are building a Turbo car, get Turbo cams!! If you are building a Supercharger car, get Supercharger cams, if you are staying NA, get NA cams. Don't waste your money on Hi-Perf NA cams, only to slap a turbo on later.

P.S. How do I know this? 2 reasons.. research and experience. I read up as much as I could on cam profile differences between OEM, NA, Turbo and SC. And even chatted with the guys at Delta about it. I had a set of Delta 2000 cams in my car when I installed my supercharger. It worked fine, but I wondered if the 2k cam was hurting performance. I swapped in a set of OEM cams, and gained 1psi (from 4.5 to 5.5 of boost).
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Old 03-29-2011, 10:26 AM   #46
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Quote:
Originally Posted by PA-Outback2000 View Post
the cams i am getting are the SAME, specs and everything, as the ones in his SC car and other customers have used them in their own SOHC turbo applications. the cams are "hot" cams, but r designed for overall performance, no matter if it's N/A or boosted. boosting only accentuates the cams performance, giving you more power than if the cams were stock.
I feel like we keep circling around the same issue again and again. Dog chasing tail anyone? A good N/A cam does not equal a good turbo cam. The end.
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Old 03-29-2011, 10:32 AM   #47
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A little reading fun to help a bit on cam differences
http://www.hotrod.com/pitstop/hrdp_1...nes/index.html
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Old 03-29-2011, 10:59 AM   #48
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Delta tells you that if you are planning on going FI on your car later not to get the 2000 grinds. I was unsure if i would so i planned safe and got the 1000 grinds which they said are find for FI apps. If you are thinking about going FI i would do that aggressive of a NA cam.
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Old 03-29-2011, 11:35 AM   #49
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ok then let me try to rephrase... they designed the biggest lift possible into the cams, while keeping an eye on the duration and other things. so, no matter what application u use, N/A, SC, or TC, u get an aggressive cam that makes great power, but also maintains drive-ability, good idle, etc.
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Old 03-29-2011, 01:23 PM   #50
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ok then let me try to rephrase... they designed the biggest lift possible into the cams, while keeping an eye on the duration and other things. so, no matter what application u use, N/A, SC, or TC, u get an aggressive cam that makes great power, but also maintains drive-ability, good idle, etc.
One word ... Impossible. Sorry bro.

Not saying an aggressive N/A cam cant be used in conjunction with a turbo but to say that it will be as efficient as a cam geared towards a turbo application is ridiculous. You are being had and at a premium price to boot.
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