Yep. The one thing I might note however is that only thing that ever gets expressed in cam degrees is cam settings, so by setting the cams at -1/+2 (3 deg at the cam gears), we actually decrease overlap by 6 deg.

 

True, but I was trying to use his reasoning of 1 degree increase when in fact it is 3 degrees (same reasoning/reference) decrease. In terms of crank, that's 6 degrees of decrease in proper terminology.

 

Exactly. Now, how about taking that HTA86 off your car and sending it to me at no charge, and. . .

 

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.

 

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.

 

thank you for all the info. burp... still digesting it sorry.

my question is does having more or less overlap increase top end power?

 

More overlap generally means more top end power and worse idle and low speed qualities.

 

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)

 

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.

 

 

Are you saying that in your opinion it is better not to adjust cam gears? Or just that it is done properly on a dyno or with a ddl so you know you are making an improvement in the desired power band? Just curious I like to hear from all sides.

 

No. Just saying the turbo has a lot to do with what changes will be benificial. Unlike N/A engines, the IVC - EVO settings are the most significant. This however depends on cam specifications which appear to be ignored judging by the outdated Cams Specs sticky, and lack of related info or interest.

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.

 

A [i]dedicated[i] 1/4 mile car

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.

 

Hi Ted, wat would be ur recommendation on the cam settings for my setup listed in my signature?

Thanx alot

 

Ted? Anyone?