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Old 12-04-2006, 12:10 AM   #1
mxv
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Default turbo/all motor camshaft differences

what do you look for in a camshaft for a turbocharged car as opposed to an all motor car?

in theory i would think longer duration and not as much lift would be preferable.
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Old 12-04-2006, 01:03 AM   #2
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Actually, it is the opposite. You look for a less duration than an all motor cam due to the motor not needing as much overlap. With too much overlap, you just end up blowing the mixture straight out the cylinder. With an all motor, you look for more overlap and duration to allow the incoming air to help push the exhaust out. This is very simplified, there is a lot of science behind the theories and the dyno results, but this is what I have read and seen on the dyno from sbc's. But for forced induction, you also benefit from higher lift getting the air in at more quantities. The cam that I have in my lt1 currently is a custom grind that is 230/236 degrees at .05 for intake/exhaust. If I would have went the turbo route with this motor, I would have picked something that is little under 225 degrees, maybe even under 220. For forced induction though, headwork goes a long ways and will yield some very impressive results even from the stock cams without affecting drivability really at all. These little motors actually come with pretty good FI cams from what I can tell, about the only thing that I would really want to do to them, is increase lift a little.
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Old 12-04-2006, 05:43 PM   #3
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Awsome reply, thanks so much. very helpful
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Old 12-04-2006, 06:44 PM   #4
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No problem, if you find a cam, I can help you decide on if it is good, I used to blueprint sbc engines, so I have a pretty good idea about cam selection.
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Old 12-04-2006, 07:40 PM   #5
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what about the 1.8 cams from http://www.integralcams.com/miata.htm
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Old 12-04-2006, 10:43 PM   #6
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The thing that I do not like about that page is that they just give the duration at .004, and not at .05. If you could get that, then you could get a good idea of the initial ramp up of the cams, and find out how aggressive the whole ramp would look. But for a 1.8L, you could get away with a little more duration than with a 1.6L. I would go with the stage 1's, maybe even the stage 2's if you want to rev a little higher. The bad thing abot those cams also is that they are a single pattern cam set, meaning that they have the same specs for both the intake and the exhaust, not sure what the flow numbers for these heads are like, but if the exhaust is lagging in the flow, you wnat to add a bigger cam on the exhaust. So, I would actually try to mix match and get a stage 1 intake, and a stage 2 exhaust. Just a guess because the engineers at mazda put more duration on the exhaust for a reason.
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Old 12-04-2006, 10:47 PM   #7
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u think there is anything to be found on adjusting the stock 1.6 cams for a t25 megasquirt setup running around 200 whp?
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Old 12-04-2006, 11:00 PM   #8
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There is always power to be found from adjusting the cam timing, but beware, you are just moving the powerband up or down, not really making more power. Advance it to get more higher end power, and retard it for more lower end power. This could get very tedious, but the stock timing is set to give the best of both worlds so to say. I would like to try retarding the cam timing and advancing the ignition timing for more low end punch, and hopefully more spool for the turbo.
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Old 12-06-2006, 03:20 PM   #9
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well ill be running a very small turbo that will probly start loosing power at around 6 grand, i would be looking to get a little more breath out of it? should i be looking into a larger turbine housing and advancing my intake and exhaust cams? id like to keep the band flat and not have it dip down at the higher rpms. its stock block and head so i wouldnt take it past 7 but id like it to get to 7 and maybe start to loose breath a little before like 6500. my .48/.49 t25 on the civic pulled awsome from a dig but it would really die off at about 6250 or so, only reason why i am concerned. i like my spool but i like my power too, damn compromises
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Old 12-06-2006, 03:34 PM   #10
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Quote:
Originally Posted by boostinsteve View Post
There is always power to be found from adjusting the cam timing, but beware, you are just moving the powerband up or down, not really making more power. Advance it to get more higher end power, and retard it for more lower end power. This could get very tedious, but the stock timing is set to give the best of both worlds so to say. I would like to try retarding the cam timing and advancing the ignition timing for more low end punch, and hopefully more spool for the turbo.
Wait, that is only true on a single cam motor. Dual cam allows you to change overlap and general opening/closing positions.

You are thinking single cam'd v8s aren't you?
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Old 12-06-2006, 04:59 PM   #11
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****!
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Old 12-06-2006, 07:20 PM   #12
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how about the fact that people are now beginning to find horsepowe gains in a relatively inexpensive exhintake cam swap???? that makes the exhaust and intake cams the same!?!?!
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