Craigorypeck
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| posted on 24/6/11 at 06:08 PM |
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NA cams and charging
What problems will result in using na spec cams with a supercharger? Only prob would be over lap??? And if not going above say 1 Bar would it work ok?
Ta
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mark chandler
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| posted on 24/6/11 at 06:28 PM |
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NA cams are generally better for forced induction so no need to worry.
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Craigorypeck
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| posted on 24/6/11 at 06:33 PM |
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Ok, whys that?
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mark chandler
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| posted on 24/6/11 at 07:29 PM |
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Hot cams are about getting more air and fuel in the engine, so longer duration, higher lift and more revs.
Put a turbo or supercharger on and you no-longer need the cam as the forced induction takes care of getting more fuel and air in.
Have a google for corky bells book, it will explain more.
Regards Mark
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flak monkey
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| posted on 24/6/11 at 07:31 PM |
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The main thing you need is low overlap. Standard cams work very well, as do mild road cams.
High lift and short duration is what you are looking for.
Sera
http://www.motosera.com
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MikeRJ
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| posted on 24/6/11 at 08:52 PM |
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quote:
Originally posted by mark chandler
NA cams are generally better for forced induction so no need to worry.
"Normaly aspirated" covers everything from bog standard mildly tuned engined with maybe 220 or 230 degree duration to a full race engine
with 320+ degree duration cams. The latter are most definitely not suitable for forced induction, but cams from a softly tuned engine would likely
work pretty well.
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Craigorypeck
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| posted on 24/6/11 at 10:04 PM |
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My cams are high lift with 288 duration, too hot for charging? would the mixture be blown out? suppose dialing a few degrees out via the pulleys would
help....
I'll check out that reading suggestion too, thanks
[Edited on 24/6/11 by Craigorypeck]
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Bare
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| posted on 25/6/11 at 02:49 AM |
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read sumething a bit more erm 'current'.
Most makers use Turbo specific cams. Wonder why?? Probably because those engineers haven't read "bell" and have no Company
pressure on them to produce massive HP gains for minumum costs.
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flak monkey
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| posted on 25/6/11 at 07:46 AM |
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quote:
Originally posted by Bare
read sumething a bit more erm 'current'.
Most makers use Turbo specific cams. Wonder why?? Probably because those engineers haven't read "bell" and have no Company
pressure on them to produce massive HP gains for minumum costs.
Very helpful as always.... Yes in an ideal world you would use a forced induction specific cam profile, but they dont exist for most engines... Bell
never suggests that you should use anything else either but does go into the theory which works in the real world too. I dare suggest he also has
considerable experience in the application of superchargers as well and building engines to suit. Do you? His book is an excellent read and the theory
doesn't date. What manufacturers do and what people do in their shed are normally 2 very different things.
FWIW I started with standard cams in the Duratec, 210deg duration, very mild and virtually no overlap.. Made 260bhp @10psi. Just changing the cams to
210bhp spec Raceline ones (a mild road cam (~270deg duration) and proven to work well in supercharged applications) took the power up to 291bhp @
7psi.
So the boost dropped a little due to increased overlap and increased airflow as you would expect.
If you cant get a specific forced induction grind then the only way to find out is experiment a little, or see what other people have done on the same
engine. I would suggest that 288deg duration will be on the high side to get the best results and you might be better fitting a milder cam.
David
Sera
http://www.motosera.com
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Craigorypeck
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| posted on 25/6/11 at 07:21 PM |
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Thanks flak.., anyone happen to have any pdf downloads on the subject?
All the stuff I've found need a rapid share account to access.
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