Ferocity02

iTrader: (60)

This might sound like a "newbie" type of question, but I would like to bring in some serious camshaft discussion and terminology to help explain the cam lope we all know and love. Now, many of us directly relate LSA with lope, which is not always accurate. Yes, a TR224 on a 112 LSA will lope more than one with a 114 LSA, but what happens when you change the duration, lift, and lobe of the cam, but keep the LSA the same...?

The basic question I have is, What single camshaft dimensions or specification reveals most accurately how much a cam will lope?

... or, is there some math one can do to get quantitative idea of how much a cam will lope? I'd like to bring into discussion certain things such as duration, lift, lobe seperation angle, advance/retard, intake centerline, exhaust centerline, IVO, IVC, EVO, EVC, overlap, lobe type, and even DCR.

Obviously there are other variables such as heads, exhaust, idle speed, etc... Lets do our best to keep all other things equal.

Discuss!

Beast96Z

iTrader: (21)

Mike, key term here is OVERLAP. Increasing duration, spliting duration, and tightening LSA are your KEY elements of lope. All of these relate to overlap. Your best bet at determining what a cam will "lope" like is using a overlap equation. Intake duration + Exauast duration /4 - LSA *2 = overlap. The other things you mentioned may have a small effect, but I believe it would be negligable. You'd probablly notice more by putting a large volume head on.

(Increasing duration) If you look at a cam, say a 224/224 112LSA since you already mentioned it, then compare it with a 244/244 112 LSA, some may think, well, there both single patterns and have the same LSA, so there gunna sound similar. Not true. Using the equation, you see that the 224 cam has 0* of overlap, but the 244 cam has 20*. That's a hell of a diffrence.

(Increasing split) I used to have a 230/236 112LSA in my 96 Z. My bud had the same motor, but sprayed, so I ordered him a 230/242 112LSA for his car. My car loped, but his car shook the house. By adding in the 6 extra degrees of exaust duration, we upped his overlap by 3 degrees over mine. This made a huge diffrence in lope.

(LSA) I think we all know how this effects things. Tighten the LSA, add overlap.

To me increasing duration and LSA make the biggest diffrence. Spliting duration should be done per application and is a by-product of what you are doing with the car.

SStrokerAce

iTrader: (2)

Yeah, OVERLAP is the key. The problem is you need to be able to calculate the overlap area to figure out how much lope the car will have. The volume and amount of idle vacuum are both affected by the static compression as well so that's also part of the issue.

Basically some experience helps when trying to get the right sound for a car, just like it does when you are working on getting the most power.

Bret

DUSTYWS6

Got a question on that equation.....when you go through your example, you calculate 0 overlap for a 224/224 112. I'm coming up with 224 + (224/4) - 112 x 2 = 56....is there a typo in the equation?

Thanks for the good info

2000TransAmWS6

iTrader: (12)

Dusty, i believe that it is supposed to be:
{[(224+224)/4]-112}*2



i understand that overlap is the key, but i hear Patrick G talking about where the overlap is centered (ie. towards the exhaust side, or what-have-you)... does that have any affect on the sound?

btw: good question Ferocity02

Ferocity02

iTrader: (60)

Thanks for the replies, I figured ovelap would be the best determiner of the amount of lope. I guess the best way to see how much lope a cam will have is to find the overlap of several off-the-shelf cams and see which one is the closest to your grind. Then you can interpolate how much lope your cam will have. Good stuff.

Beast96Z

iTrader: (21)

224+224=448 448/4=112 112-112=0 0*2=0