Drive ability for cam duration?
02-21-2003, 09:38 AM
#1
Drive ability for cam duration? ok im still trying to figure out cams
Now as the duration (intake and exhaust) are larger that decreases driveabilty for the street right?
Now is it total duration (both the intake and exhaust) or just one?
for example is a 226/220 more street freindly then a 224/224 since the total duration is greater or does just one like the inatke have to be high for it to loose streetablity?
thinking of switching my cam sometime and want it a little freindlier (but not much)
Now as the duration (intake and exhaust) are larger that decreases driveabilty for the street right?
Now is it total duration (both the intake and exhaust) or just one?
for example is a 226/220 more street freindly then a 224/224 since the total duration is greater or does just one like the inatke have to be high for it to loose streetablity?
thinking of switching my cam sometime and want it a little freindlier (but not much)
02-21-2003, 11:49 AM
#2
TECH Senior Member
Re: Drive ability for cam duration? Having a rough idle is basically asking how much overlap do you have, so you should be looking at the total duration.
Assuming proper tuning and all else being equal, the 226/220 should idle better than the 224/224. This is one good thing about reverse splits. It keeps the idle smoother for a given intake duration. <img border="0" title="" alt="[Cool]" src="gr_images/icons/cool.gif" />
<small>[ February 21, 2003, 11:50 AM: Message edited by: Colonel ]</small>
Assuming proper tuning and all else being equal, the 226/220 should idle better than the 224/224. This is one good thing about reverse splits. It keeps the idle smoother for a given intake duration. <img border="0" title="" alt="[Cool]" src="gr_images/icons/cool.gif" />
<small>[ February 21, 2003, 11:50 AM: Message edited by: Colonel ]</small>
02-21-2003, 11:53 AM
#3
Re: Drive ability for cam duration? It is the combination of intake and exhaust duration as well as LSA the affect driveabilty. The reason is because it is actually valve overlap that determines this. So if you are comparing two cams with the same LSA, you can get an idea of how the overlap compares by adding the intake and exhaust duration together and then comparing this number. E.G. 226+220=446, 224+224=448; so the 226 cam would have less overlap than the 224 assuming they both have the sam LSA. But this is a pretty small difference; this would be like comparing a 223 with a 224; not a big difference here . . . you might not even notice it. I'd try a 220 on 116 LSA to smooth things out.
02-21-2003, 01:03 PM
#4
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Re: Drive ability for cam duration? I am running a Comp 220/220 .564 on a 115 lobe Center Angle and it idles like stock with a very slight hint of a lope at 800 RPM. Overlap increases and idle quality decreases as the duration goes up and the lobe center goes down.
Increased overlap will help engine volumetric efficiency when properly tuned exhaust headers are used although there is a tradeoff in idle quality.
Generally speaking, to be emmissions legal on an LS1, stay with 220-222 duration on a 114 or larger lobe center. For example, a TR224 on a 112 would probably not pass but a TR220 on a 114 should. Increasing the idle speed will also help.
Excessive overlap causes the engine to misfire at idle, passing raw fuel out the exhaust, increasing HC emmissions.
Paul J.
Increased overlap will help engine volumetric efficiency when properly tuned exhaust headers are used although there is a tradeoff in idle quality.
Generally speaking, to be emmissions legal on an LS1, stay with 220-222 duration on a 114 or larger lobe center. For example, a TR224 on a 112 would probably not pass but a TR220 on a 114 should. Increasing the idle speed will also help.
Excessive overlap causes the engine to misfire at idle, passing raw fuel out the exhaust, increasing HC emmissions.
Paul J.