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Old 10-21-2015, 02:49 AM   #16
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Thank you.. I've been having a hell of a time trying to work out what kind of powerband I'm going to get. Mostly want to avoid it feeling like a diesel and falling on its face by 4k.
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Old 10-21-2015, 03:25 AM   #17
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you can nicely improve the exhaust port with the correct port shape, this is where i would focus before worrying about a bigger valve

those cam details are useless, it only matters what the valve motion is. only the cam grinder needs to worry about the profile of the cam lobe

http://www.r3vlimited.com/board/showthread.php?t=368069

i wouldnt go down the less duration path it doesnt make sense, a split cam with more exhaust duration is often used but you dont really want a narrow LSA
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Old 10-21-2015, 04:33 AM   #18
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So I was intrigued by the eta cam thing. Digger, are you saying it won't really do anything? That makes me sad. Because if it would, that would be neat. Also, I have one sitting on the shelf. I get the feeling meta doesn't have/want a cam grinder. Budget style. Anyway, what would the difference in power band likely be between the two?
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Old 10-21-2015, 06:52 AM   #19
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Here was a dyno sheet from a dyno day that I went to just days after swapping out an auto trans and swapping out #19 injectors for some #28 because I was maxing out the 19s(using a RRFPR) so this was only a require fuel change and not retuned so it was getting into untuned territory and the AFRs were climbing quick. There is a dip where I had pretty much stopped tuning because I didn't think it would be making power above 5500 where the SETA redlines at.

It was running about 8 psi here I believe and I was really surprised to see it pulling past 6k and looks like it could have pulled a bit more than the 6300 tuned in that area.

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Old 10-21-2015, 02:02 PM   #20
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So I was intrigued by the eta cam thing. Digger, are you saying it won't really do anything? That makes me sad. Because if it would, that would be neat. Also, I have one sitting on the shelf. I get the feeling meta doesn't have/want a cam grinder. Budget style. Anyway, what would the difference in power band likely be between the two?
Why would you think it would?

You can get an off the shelf regrind pretty cheap these days.
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Old 10-21-2015, 03:20 PM   #21
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Well, because someone on the internet said it would. Then I asked to find out more details about why it would or wouldn't help in some way. So what might happen? You are allowed to say "I don't know", but if you do know, please fill us in. Thaaaaaanks.
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Old 10-21-2015, 04:20 PM   #22
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The duration is way too small look at what it does to a seta....Usually people add duration on the exhaust side compared to inlet. When people say less duration and overlap they mean compared to a performance NA cam rather than with respect to the stock cam. you wouldnt use anything less than a stock b25 cam it will just cost power. as a cheap start point just use a stock b25 cam and see how you like it
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Old 10-21-2015, 07:00 PM   #23
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Alrighty. Thanks for your expertise.
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Old 10-23-2015, 11:02 PM   #24
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First, nothing against anybody else's insight whatsoever, and I am grateful for all of the help I get...
...but digger, whodwho, ether-d, you guys are probably some of my most respected fellow r3v-mates that I have been inspired by and learned much of what I [think] I know from reading your tales, so I just had to give a big thank you for the work you all have done before I ever picked up the baton. less than a year ago, I knew nearly nothing in detail about these (or any cars) That said, I intend to milk you like cows until I might join your ranks; but enough ass kissing...

digger, I actually saw your post about cam profiles on another forum, maybe thats where you lost them lol? The only significant difference in overlap seemed to be with the shrick 288.

My interest in the seta cam was for increased lift, not the lack of duration, I just thought it would be a bonus that it has less overlap, and that the intake closes a little sooner to build more compression from the otherwise wheezy roots type blower.

Plus the article i linked - http://victorylibrary.com/supercharg...er-engine5.htm stated
"Extended timing is no longer needed to produce peak power, and will interfere with boosted operation." so it seemed to be a good choice to use whichever stock cam yielded the most favorable conditions. The seta does come across a little weak on the exhaust side but the intake looked enticing.

whodwho those dyno results are interesting... i would like to see what more experimentation would yield in terms of information on the subject.

Also I am still considering the 8.5:1 compression...
http://www.wallaceracing.com/boost-c...ratio-calc.php says with a static compression of 8.5:1, 12 psi puts the effective CR at either 15.44 or 11.46:1 at sea level depending on which formula is used (i'm only a few hundred feet above sea level and the latter result seems more consistent with what i've observed in other builds). I figure 12 psi is probably a reasonable soft upper limit to what I can expect to get from an m90 and it's easier to add more boost than to lower the CR if things dont quite add up.

Lastly, ether-d, I thought you would be proud to know I just scored a gutted 325ix with a solid motor and drivetrain for $75 from a nearby r3v member when I joined the regional e30 club he is a cofounder of. (Not sure who his on here..)
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Old 10-24-2015, 11:25 AM   #25
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Wow, a $75 iX is the shiznit. I'm equal parts proud and jealous.

One of the only ways we'll know for sure about the cams is to dyno before and after. Another would be to look up cam profile differences for production cars that had the same engines in forced and n/a applications. Meta, you seem to be good at that type of research. You now have your homework for tonight. Not to say digger isn't the final word because he really does know his shit. I'm just wondering if it could make a difference, like you said, because the motor isn't sucking it's own air.
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Old 10-24-2015, 12:28 PM   #26
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Jordan, is that you?
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Old 10-24-2015, 04:44 PM   #27
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yessir! whats up man?
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Old 10-24-2015, 04:46 PM   #28
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thanks for the assignment mr. D. I've been digging and will continue to do so but usually I post things hoping digger will descend upon us and spread his wisdom lol
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Old 10-24-2015, 04:47 PM   #29
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no pun intended
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Old 10-24-2015, 05:50 PM   #30
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yessir! whats up man?
I have been jealous of/inspired by ether-d's build, and infatuated with the idea of a diy supercharger setup. When your thread popped up, I subscribed. I just now realized who you are, and that you're local! If you ever want a hand working on your build, I would love to help out.
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