HP Predictions

[turdwilly]

My thinking was that 111° LSA would broaden the torque curve but it would lower the peak number a bit. But maybe I wasn't giving enough consideration to the methanol.

What is it about the 111* LSA that would broaden the torque curve, but at the cost of peak HP ?

Randy

I didn't say anything about HP. I just thought it would make the torque curve broader & "flatter" if you will, not as peaky, so the peak torque number wouldn't be as high as it would with the same lobes ground on a 106-108 LSA. But I don't have any experience with methanol, so I don't know how that will affect the torque numbers.

[randy331]

The question wasn't really what the 111* LSA would do to the power curve as much as, why it would do it ?

What valve events being moved a few deg. will cause what you say will happen to power curve?

Randy

[turdwilly]

The question wasn't really what the 111* LSA would do to the power curve as much as, why it would do it ?

What valve events being moved a few deg. will cause what you say will happen to power curve?

Randy

There's an age-old adage that widening the LSA a cam with otherwise identical lobes broadens the torque curve at the expense of the peak number. Why? I don't know - I'm not that smart. But my experience has seemed to bear it out.

Now I can tell you why I think it would happen....

If you have two cams with identical lobes but different LSA, the cam with a larger LSA will have less overlap than the cam with a smaller LSA, so the engine will be more efficient very early in the useable rpm range (slightly more torque at the bottom of the range), but you will also open the exhaust sooner & close the intake later, so it will be less efficient at the peak torque rpm of the cam with the narrower LSA (slightly less torque at peak tq rpm) as it will have less time to push on the piston with the earlier EO, & it will trap less total mixture charge at that rpm with the later IC. The larger LSA cam also will be slightly more efficient in the top of the useable rpm range because the higher rpm will lessen the hurtful effect of the earlier EO, but the later IC will allow a more efficient cylinder fill in the upper rpm range than will the narrower LSA cam's earlier IC.

All of the above will lead to a slightly "flatter" or less "peaky" torque curve with the larger LSA cam.

The cam with the smaller LSA will have more overlap & will therefore be less efficient very early in the useable rpm range (slightly less torque at the bottom of the range), but will also open the exhaust later & close the intake earlier than the larger LSA cam, so it will be more efficient at peak torque rpm than the larger LSA cam (slightly more torque at peak tq rpm) because it will push on the piston longer with the later EO, & it will trap more total mixture charge at that rpm with the earlier IC. The smaller LSA cam will be slightly less efficient beyond peak torque rpm in the top of the useable rpm range because the earlier IC will allow a less efficient cylinder fill at higher rpm.

All of the above will lead to a slightly more "peaky" torque curve with the smaller LSA cam.

I realize all of this is affected by the tuning of the intake runner length & volume, plenum volume, header & collector tuning, etc. due to charge velocities, wave tuning & all of that other stuff that's over my head. That's why I'm not a professional engine builder.

I also realize that your question was purely rhetorical - that's the way my mind sees it so that's my best guess - am I even close?

[wyrmrider]

close enough for government use
Intake lobe center would change also
what it really gets down to are the valve events especially seat timing- the cam grind can also affect,
compression
etc