cam gear settings
Nov 25, 2008, 08:35 AM
#49
Hey, you can have it as long as Robert approves. I REALLY like the stock appearing units. I think something simple like a 625 whp stock appearing would do me just fine. I love that bottom end torque. Thanks, Ted B for all you do for these threads. It sure helps to keep things straight and I use your knowledge all the time. You're an asset to the community.
Nov 25, 2008, 08:54 AM
#50
One more post for showing the answer to the C6 question.
In this diagram (nothing to do with anything other than show a sample set of cams and the timing events. The 2 curves represent each cam's events. The one on the left is the exhaust, the curve on the right is the intake. This is the standard method of showing timing events. The entire cyle shown would represent 2 full 360 crank degree cycles. Directly in the middle (the small triangular area in the middle between each curve0 represents the overlap. With the curve on the left being exhaust, the left most part of the curve is the beginning of the exhaust cam opening event. The top of the curve is at maximum lift and directly in the middle of the EXHAUST cam's duration. The curve now goes back down and the cam begins to close the exhaust valve. BEFORE the exhaust cam gets closed, notice the intersection of the INTAKE cams OPENING event. This creates the triangular shape in the middle, which is the OVERLAP. Now, if the exhaust cam is ADVANCED, imagine moving the left curve to the LEFT by 2 CAM degrees (4 Crank degrees). Remember, half of this diagram is 360 CRANK degrees, the entire diagram is 720 degrees. Also, if the Intake is RETARDED by 1 CAM degree (2 CRANK degrees) it would be moved to the RIGHT. By moving each of the curves, EXHAUST to the LEFT, INTAKE to the RIGHT, you would be further separating the LOBE CENTERLINES by 3 CAM degrees, but 6 CRANK degrees. This would make the triangle smaller, LESS OVERLAP. Don't want to be demeaning or over stating what is probably already know by many, just trying to help those who may be reading, but still not clear. Hope this helps.
In this diagram (nothing to do with anything other than show a sample set of cams and the timing events. The 2 curves represent each cam's events. The one on the left is the exhaust, the curve on the right is the intake. This is the standard method of showing timing events. The entire cyle shown would represent 2 full 360 crank degree cycles. Directly in the middle (the small triangular area in the middle between each curve0 represents the overlap. With the curve on the left being exhaust, the left most part of the curve is the beginning of the exhaust cam opening event. The top of the curve is at maximum lift and directly in the middle of the EXHAUST cam's duration. The curve now goes back down and the cam begins to close the exhaust valve. BEFORE the exhaust cam gets closed, notice the intersection of the INTAKE cams OPENING event. This creates the triangular shape in the middle, which is the OVERLAP. Now, if the exhaust cam is ADVANCED, imagine moving the left curve to the LEFT by 2 CAM degrees (4 Crank degrees). Remember, half of this diagram is 360 CRANK degrees, the entire diagram is 720 degrees. Also, if the Intake is RETARDED by 1 CAM degree (2 CRANK degrees) it would be moved to the RIGHT. By moving each of the curves, EXHAUST to the LEFT, INTAKE to the RIGHT, you would be further separating the LOBE CENTERLINES by 3 CAM degrees, but 6 CRANK degrees. This would make the triangle smaller, LESS OVERLAP. Don't want to be demeaning or over stating what is probably already know by many, just trying to help those who may be reading, but still not clear. Hope this helps.
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chvlleguy (Dec 16, 2023)
Dec 9, 2008, 03:23 PM
#53
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Ted B,
In 1/4 mile... do we need more mid-range power or more top end?
Also I know Jun 272 wasn't tested on AMS Cam test but which one is better Jun 272 vs Kelford 272 on PT67?(will give me faster 1/4 mile times)
In 1/4 mile... do we need more mid-range power or more top end?
Also I know Jun 272 wasn't tested on AMS Cam test but which one is better Jun 272 vs Kelford 272 on PT67?(will give me faster 1/4 mile times)
Dec 9, 2008, 07:13 PM
#54
Think of what rpm is used in a 1/4 mile - like 5000+ rpm - redline.
Another thing, cam/cam setting results depend alot on the turbo used. A stock turbo with fixed cams having advanced intake valves and delayed exhaust might make use of the scavaging at lower rpm and provide an AWD tire spinning punch, but probably won't perform on the track. Mid to high rpm will allow too much exhaust reversion at overlap killing power and increases chance of preignition.
Another thing, cam/cam setting results depend alot on the turbo used. A stock turbo with fixed cams having advanced intake valves and delayed exhaust might make use of the scavaging at lower rpm and provide an AWD tire spinning punch, but probably won't perform on the track. Mid to high rpm will allow too much exhaust reversion at overlap killing power and increases chance of preignition.
Dec 12, 2008, 03:29 PM
#55
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Dec 12, 2008, 06:19 PM
#56
Think of what rpm is used in a 1/4 mile - like 5000+ rpm - redline.
Another thing, cam/cam setting results depend alot on the turbo used. A stock turbo with fixed cams having advanced intake valves and delayed exhaust might make use of the scavaging at lower rpm and provide an AWD tire spinning punch, but probably won't perform on the track. Mid to high rpm will allow too much exhaust reversion at overlap killing power and increases chance of preignition.
Another thing, cam/cam setting results depend alot on the turbo used. A stock turbo with fixed cams having advanced intake valves and delayed exhaust might make use of the scavaging at lower rpm and provide an AWD tire spinning punch, but probably won't perform on the track. Mid to high rpm will allow too much exhaust reversion at overlap killing power and increases chance of preignition.
Last edited by mt057; Dec 12, 2008 at 06:21 PM. Reason: i suck at spelling
Dec 12, 2008, 08:20 PM
#57
Anyhow, for stock turbos and high boost you probably want to avoid advancing the IV or retarding EV, just my opinion. Without a dyno the best way to judge target VE gains would probably be by speed density, the AFR will lean where power goes up.
Dec 12, 2008, 10:18 PM
#58
First of all, one has to identify what it is that he is realistically trying to achieve. When someone refers to "1/4 mile", does that mean a street-driven car aiming for good 1/4 mile performance or a 42R equipped dedicated track car? It makes a difference.
Secondly, as for which is better between a JUN 272 and a Kelford 272, I'd say that depends on the setup, as they are actually quite different cams.
