speedtigger

iTrader: (16)

I think what the engine builder demonstrated to me was that there is a relationship between the engine displacement and head flow and head volume to consider as well. Not just displacement, but displacement relative to head size.

ZONES89RS

iTrader: (25)

It is the operating RPM that determines everything along with the cubes. From there it makes the required head flow, compression, cam, ect. That is the way I has come to look at it.

topbrent

iTrader: (1)

Broad strokes definitions, tighter LSA will generally yield a few important things.


- More Torque and More Horsepower throughout the useable RPM range. (Some call this peaky, others call this winning the race by being faster)
- Higher cranking compression. (earlier intake valve close)
- increased EGR effect, or intake draw velocity.
- Snappier feel.
- Rougher Idle
- Intolerance to exhaust backpressure
- Poor emissions
- Higher fuel consumption

ZONES89RS

iTrader: (25)

That pretty much sums it up. Although I get decent fuel economy and have seen some still pass emissions.

speedtigger

iTrader: (16)

I agree with everything except for:
- More Torque and More Horsepower throughout the useable RPM range.
- Snappier feel.

I think it is pretty well accepted that narrower LSA cams generally have a narrower power band. The power tends to be more concentrated in a narrower RPM range but more average power in that range. Wider LSA cams tend to have a wider flatter power band.

In fact, back in the day when Crower Cams had a truly huge catalog of racing cams, they generally recommended wider LSA cams for stick shift drag cars than automatics because they were in touch with the fact that high stall converters allowed drag cars to function in a very narrow RPM range where stick shifts required a wider flatter powerband to maintain a good average HP.

As for the snappier feel, I have never noticed this correlation.

The funny thing with all of our combined experience is that we can get in the ball park with what we think will work, but nothing beats seeing combination with our specific engines in similar vehicles. That information is golden and that is why I love the 10 second combo list that Topbrent compiled. That is money right there.

ZONES89RS

iTrader: (25)

I think the snappier feel is kind of true, the power is usually in faster, so it seems snappier to me. Seems to explode to life upon throttle stab.

Doug G

Wide LSA's give better drive-ability,emissions,smoother idle,and ect. the Mfg's think most want.
Power with a wide LSA seems to come in later in the RPM range

stevecritt

iTrader: (3)

^ Lots of good info up there. Thanks.

well I talked with the guy at EPS and he seemed pretty straight forward. We are going to talk over some combos and go from there. Did not get a chance to go over any specifics really.