Cam driveability
01-25-2006, 01:12 PM
#1
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Cam driveability On a fuel injected F-body car what part about the cam that changes when going to a bigger cam effects driveablility most. Is it the lsa,duration or lift that makes it stall at traffic lights and drive bad. I know that tuning can fix that but without the tuning what makes it do that? Hopes this makes sense please excuse my ignorance. Thanks 
01-25-2006, 01:18 PM
#2
Originally Posted by LS1dirtybird00
On a fuel injected F-body car what part about the cam that changes when going to a bigger cam effects driveablility most. Is it the lsa,duration or lift that makes it stall at traffic lights and drive bad. I know that tuning can fix that but without the tuning what makes it do that? Hopes this makes sense please excuse my ignorance. Thanks
01-25-2006, 01:44 PM
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Overlap. Both LSA & duration affect overlap. Typically, a degree in LSA affects overlap more than a degree in duration. If you want to learn more about it, find an engine setup simulator and play around with different durations and LSAs to see how they affect cam timing events & overlap.
01-25-2006, 02:37 PM
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So you are saying that lsa has the most of effect on driveability tuning. Another words lsa is what makes a car stall at stop lights without proper tuning. A cam with a lsa of 110 ten is going to run worse and be harder to tune then a cam with 112 lsa?
01-25-2006, 02:55 PM
#5
Originally Posted by LS1dirtybird00
Another words lsa is what makes a car stall at stop lights without proper tuning.
01-25-2006, 03:17 PM
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The overlap between intake & exhaust valve opening & closing is one of the primary causes of stumbling at idle. Some say the exhaust gas gets mixed in with the fresh intake charge and causes the rough idle.
Another reason for driveability issues is a "lopey" cam. A cam that has a late intake valve closing event (typical of large duration cams) will bleed off cylinder pressure at low rpms and create a "lope". Cylinder pressure creates torque, so that is why lopey cams typically are not know for their abundant lowend power.
So, to answer your question, if you have 2 cams of the same duration and same intake valve closing event but the LSAs are different, the cam with the lower LSA will be more rough-idled. However, understand that you could have say a 195/200 duration, 110 lsa cam that idles much better than a 235/240 duration, 114 lsa cam.
Another reason for driveability issues is a "lopey" cam. A cam that has a late intake valve closing event (typical of large duration cams) will bleed off cylinder pressure at low rpms and create a "lope". Cylinder pressure creates torque, so that is why lopey cams typically are not know for their abundant lowend power.
So, to answer your question, if you have 2 cams of the same duration and same intake valve closing event but the LSAs are different, the cam with the lower LSA will be more rough-idled. However, understand that you could have say a 195/200 duration, 110 lsa cam that idles much better than a 235/240 duration, 114 lsa cam.
01-25-2006, 04:22 PM
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The reason why I am asking all this is because I will putting Patriot stage three heads,carb intake, headers ect ect. I am putting a cam in also and I have a couple to chose from MS3 Trak Trex S1 G5x3. I will be tuning it myself and its not exactly a daily driver but I do want ok driveabilty and I want to know for myself what effects driveability and not just take someones word on what cam to buy because they have it. Thanks for the responces.
