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Old 06-07-2010, 02:13 AM   #1 (permalink)
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Arrow Adjustable cam gears?

So i have been doing some research about adjustable cam gears at a few different MPG websites and it seems to me that if i were to get an adjustable cam gear for 95 SL1 SOHC i would be able to advance the cam timing a few degrees and shift the powerband down the rpm range hopefully to something like peak torque at 1400-700rpm. I know that it would reduce the top end of the car (the SOHC only revs to 5500rpm anyway but i stay below 2500rpm - 2600rpm max) The peak torque on the Saturn SOHC engine comes on right around 2450rpm. I know that is low but since i shift between 1600-2000rpm i figured it would drastically help to be able to have peak torque available at those rpm for acceleration and cruising (60mph at about 2100rpm) i know that diamondlarry had a small cam advance (2-4 degrees) when he had his head shaved and it supposedly helped out alot. The adjustable cam gear for the Saturn also is only about $75 so i think that is a reasonable enough price to have torque available at such a low rpm. Anyways let me know what you guys think.

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Old 06-07-2010, 07:13 AM   #2 (permalink)
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I semi-recently bought an adjustable cam timing pulley for my Paseo. I haven't had a chance to try it out yet though. IMO it should work though.
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Old 06-07-2010, 08:55 AM   #3 (permalink)
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As I understand it, non-optimum cam timing is used for pollution control. You really want a milder cam with less total dwell and overlap.
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Old 06-07-2010, 04:18 PM   #4 (permalink)
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Quote:
Originally Posted by Bicycle Bob View Post
As I understand it, non-optimum cam timing is used for pollution control. You really want a milder cam with less total dwell and overlap.
definately non-optimal.
advancing timing on injection can be tricky.. the dealy is more than emissions, it is to allow ecu to be the slow dummy it is...by up to 14 degrees. The carb cams, even emission versions... are advanced towards 3 degrees, because it is realtime. Errors impossible, gear driven distributor included.

I would love to know if this works, as I have two cams that are injected, and want the lift for my carb engine. I need to advance by 10 degrees to be normal.

also advance should cool down top end, injection plays with temperatures so something may go rich and ruin hypermiling...
sohc should be a rock and dymamical.
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Old 06-07-2010, 11:27 PM   #5 (permalink)
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at least two variables

..."had a small cam advance (2-4 degrees) when he had his head shaved "....

when he had his
"head shaved"
he also INcreased his compression ratio as well as the small valve timing change
so
just a slight valve timing change
alone
may not / will not provide the same results / improvement
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Old 06-08-2010, 12:11 AM   #6 (permalink)
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Actually by shaving the head he most likely (from illustrations I found for saturns) retarded his cam timing (works that way on most engines I've seen). If he had the cam sprocket modified maybe it was to compensate for this? Some engines respond better to these changes than others too.

I drilled my cam sprocket for my metro +10, but it's a little different than most engines, next step for me is an XFI cam. Ideally these modifications would be complemented by smaller intake and exhaust tracts to maximize torque in the operating range we use instead of the 6,500 RPMs most modern engines can rev to nowadays...

I often wonder what kind of FE you could get with a gas engine designed for a peak RPM of 3,000-3,500?
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Old 06-08-2010, 07:07 AM   #7 (permalink)
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The Prius engine maxes out at 4k I think. I know of no other gas engine that is that low.

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