[horsepowerfreek1]

When talking about camshaft events, overlap for example when you changed the LSA and compared cams wouldn't you take in account the area in the valve overlap triangle.

 

[Lobes]

When talking about camshaft events, overlap for example when you changed the LSA and compared cams wouldn't you take in account the area in the valve overlap triangle.

A very limited look, but yes. It is a good observation that you identified overlap as an event onto itself. An event that can be manipulated in ways other than just changing LSA.

 

[Chris Uratchko]

Certainly we can examine the area under the curves that make up overlap.... but overlap to me is a bit troublesome as it is not an easy thing to calculate... IMHO. It's a learned event characteristic based on the entire engine design specific to that exact engine. Certainly we can get somewhat close.... we do all the time. It can just be difficult to predict precisely.

 

[Graphic Man]

Certainly we can examine the area under the curves that make up overlap.... but overlap to me is a bit troublesome as it is not an easy thing to calculate... IMHO. It's a learned event characteristic based on the entire engine design specific to that exact engine. Certainly we can get somewhat close.... we do all the time. It can just be difficult to predict precisely.

I am guessing the dyno and track time would quickly tell you where it needs to be ?

 

[Stan Weiss]

In reference to overlap does anyone do this? Break it down it 4 areas. The exhaust from intake open until TDC and from TDC to exhaust close and then from intake open to TDC and from TDC to exhaust close. In both cases the total would be the sum of the 2 two parts.

Stan

 

[Lobes]

In reference to overlap does anyone do this? Break it down it 4 areas. The exhaust from intake open until TDC and from TDC to exhaust close and then from intake open to TDC and from TDC to exhaust close. In both cases the total would be the sum of the 2 two parts.

Stan

Stan,

By labeling the 4 "areas" your are denoting points and what you said holds true. I think most people view it that way. The area under the curves connecting those points, however, can tell a different story.

 

[65BEAVER]

Since we're on overlap subject. In a 4valve engine like a modular with a whipple, in my testing ive found the engine makes more average power with more overlap. When ive shortened the overlap i thought i would possibly gain a bit of boost thus increase power. But i was wrong. They are limited to a certain pulley so i was trying to increase the boost. 1lb is typically 30-35 average better. For you cam guys why did i not gain a bit of boost with less overlap? I was making huge changes on the dyno. This was a few years ago but i think i went down in the low 20's for overlap and i think in the mid 30's the other way..

 

[carlie]

The IVO/EVC profiles that help "trap" the best.

 

[john marcella]

Since we're on overlap subject. In a 4valve engine like a modular with a whipple, in my testing ive found the engine makes more average power with more overlap. When ive shortened the overlap i thought i would possibly gain a bit of boost thus increase power. But i was wrong. They are limited to a certain pulley so i was trying to increase the boost. 1lb is typically 30-35 average better. For you cam guys why did i not gain a bit of boost with less overlap? I was making huge changes on the dyno. This was a few years ago but i think i went down in the low 20's for overlap and i think in the mid 30's the other way..

Because you didn't have the time/area to get as complete of change over of the chamber volume . / ex gas vs new air fuel charge. JMO

 

[Chris Uratchko]

Because you didn't have the time/area to get as complete of change over of the chamber volume . / ex gas vs new air fuel charge. JMO

But if he cracked the EVO sooner, he may have been able to EVC it sooner due to a more complete evacuation, thus reducing overlap.

Most folks aren't willing to EVO when they 'can'...