cam comparison
07-29-2008, 11:47 PM
#27
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i posted the sheet comparing the power band of them all.
i posted the afr and timing to get those numbers.
how is anything bogus?
how i got to the timing levels? when the afr was at said posted point?
c'mon now, you know i don't give that info out.
::smack::
i posted the afr and timing to get those numbers.
how is anything bogus?
how i got to the timing levels? when the afr was at said posted point?
c'mon now, you know i don't give that info out.
::smack::
07-30-2008, 12:18 AM
#28
depends..tightening up the lsa between the intake and exhaust cams will cause more overlap which will move ur powerband up in the rpm range which by bryans power band would be a huge gain in traps
u dont have to adjust the cam gears in the same rotation thats the benefit of having adjustable cam gears
u dont have to adjust the cam gears in the same rotation thats the benefit of having adjustable cam gears
Thats not advancing the cams. and that won't necessarily up the power band.....lsa is just a byproduct of valve events, never judge cams by there lsa.
07-30-2008, 05:48 AM
#32
Nice curves! 
Finally a real comparison of cams, thank you for this.
GM-R => 11.6 afr. 20 degree's of timing
272's => 12.0 afr 24 degree's.
Stock => 12.4 25 degree's of timing.
Looks like a pretty safe tune on those GM-R's. And nice to see that they have a really broad powerband.
Are you still running an unmodified head? A decent (exhaust) port job will probably raise that top end even more. Add a somewhat decent flowing inlet manifold and I would be very satisfied...
Finally a real comparison of cams, thank you for this.
GM-R => 11.6 afr. 20 degree's of timing
272's => 12.0 afr 24 degree's.
Stock => 12.4 25 degree's of timing.
Looks like a pretty safe tune on those GM-R's. And nice to see that they have a really broad powerband.
Are you still running an unmodified head? A decent (exhaust) port job will probably raise that top end even more. Add a somewhat decent flowing inlet manifold and I would be very satisfied...
Last edited by Speedytec; 07-30-2008 at 06:04 AM.
07-30-2008, 08:35 AM
#35
Senior Member
as the airflow across the head bumps, the timeing drops, just like it should.
advancing the stock cams, and even the GMR cars (tho it would take more advance) would cause a torque spike earlier, thus bumping power, however they would "fall off" sooner as well.
even with RPM being your friend on the dyno, helping you build power, the drop in air flow from doing this up top would be impossible to recover from.
also, as the overlap jumps, the "sooner" per say that you start to waste usable, "make me some power", air flow rite out the back with out getting any effect from it.
however on a turbo car........the result becomes a touch more friendly.
advancing the stock cams, and even the GMR cars (tho it would take more advance) would cause a torque spike earlier, thus bumping power, however they would "fall off" sooner as well.
even with RPM being your friend on the dyno, helping you build power, the drop in air flow from doing this up top would be impossible to recover from.
also, as the overlap jumps, the "sooner" per say that you start to waste usable, "make me some power", air flow rite out the back with out getting any effect from it.
however on a turbo car........the result becomes a touch more friendly.
07-30-2008, 10:45 AM
#40
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as a retort to raven about the torque issue, and witt, for the drunk text last night about this.
if you look at the timing numbers i posted vs stock cams vs 272's you'll see why it's lower. could i crank the low end timing and get the torque back up above the stock cam numbers? yes. why didn't i? who says i didn't.
this is the closest numbers i could find without blowing any of them out of the water. i spent a good hour going through 150 dyno runs to get these three numbers for this comparison.
now, this is why the numbers are so close. more or less to show the effective power band of them all, not the peak power numbers from any of them. the stock cam dyno number IS ***** out, foot to floor engine screaming at 3 am on the rollers. it had nothing more.
thanks kids. i'll be here all week. try the veal
if you look at the timing numbers i posted vs stock cams vs 272's you'll see why it's lower. could i crank the low end timing and get the torque back up above the stock cam numbers? yes. why didn't i? who says i didn't.
this is the closest numbers i could find without blowing any of them out of the water. i spent a good hour going through 150 dyno runs to get these three numbers for this comparison.
now, this is why the numbers are so close. more or less to show the effective power band of them all, not the peak power numbers from any of them. the stock cam dyno number IS ***** out, foot to floor engine screaming at 3 am on the rollers. it had nothing more.
thanks kids. i'll be here all week. try the veal
07-30-2008, 11:09 AM
#42
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technically speaking thats advancing one and retarding the other...maybe its different in the honda world but i dont see how it would vary IMO
07-30-2008, 11:30 AM
#44
anyone have a cam book i can read or a website i can go to to learn some more, i understand duration lift seperation... or was that ***** not cams.. anyways i dont get how haveing a certain valve open at a certain time does what to hp and tq and how overlapping them changes how things work....
07-30-2008, 11:36 AM
#45
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Once someone figures everything out... can they please nicelely place it in an pm and send it to me so i know what to get for my engine next? k thanks..
07-30-2008, 11:36 AM
#46
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07-30-2008, 11:57 AM
#49
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take it from the guy who built the car and ran the car at the track, the build book is one thing; the cams came out and in the actual event it ran stock cams....thats it my friend you can argue all you want my information is based on what happened . I was there.
07-30-2008, 12:00 PM
#50
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which backs up my beliefs that adjustable cam gears is a better buy than cam shafts themselves