Originally Posted by Patrick G

One of the best ways to maximize the area under the curve is by utilizing parts that compliment each other. Too often, racers on this board design their motors without regard to all of the pieces of the puzzle, most notably, the intake manifold. The great thing about the LSX intake is that it gives a nice broad power and torque curve. The downside is that the runner length of the LS1/LS6/FAST and port cross sectional area tend to force a torque peak around 4800 rpm and a power peak around 6300 rpm.

The intake valve closing point is the biggest determiner as to where the motor makes peak power, but the intake manifold will always try to force the 6300 rpm power peak. Sure you can force a later power peak by closing the intake valve later, but experience has shown that the gains up high will not offset the losses in the mid-range. Basically the area under the curve gets worse.

For a stock displacement 346, there are diminishing returns in power once you exceed an intake valve closing point of 46 degrees ABDC at .050" when running an LSX intake manifold. General Motors knows this better than anyone. Just look at their factory race cams:

ASA Cam: 226/236 110LSA (IVC of 43 degrees ABDC)
Grand Cup Cam: 239/251 106LSA (IVC of 45.5 degrees ABDC)

These cams make excellent power under the curve. Why? Because they pump up dynamic compression and close the intake valve within the window that the LSX intake manifold likes.

There are many cams that make good peak power, but are pretty weak in the low and mid range. Almost without exception, they are large duration cams with wide LSAs.

Take this cam for example: 237/242 113LSA +0. This is a popular cam that is known for making good peak numbers, but what is left out is how weak the area under the curve is. Why? Because the intake valve closing point is 52.5 degrees. That's more than 6 degrees past what the LSX intake manifold is tuned for. The small gains up top are not worth the large losses down low. The dynamic compression is a cam-only arrangement is below 8:1. Not good!

So in a nutshell, when running an LSX manifold, we need to keep our valve events in line with the rpm range the intake manifold was designed for if we are interested in maximizing the area under the curve. GM knows this and many on this board know this. Sadly, many of our sponsors are promoting cams to the street/strip crowd that are poor candidates for maximizing the torque curve.

Originally Posted by joecar

What would the TQ/HP curves look like for a 1000HP Supra and a 1000HP LS1...?

Which one would you rather have...?

Having a large area under the torque curve makes for a very responsive street car (95% of time spent below 4000RPM).

Originally Posted by Patrick G

For a stock displacement 346, there are diminishing returns in power once you exceed an intake valve closing point of 46 degrees ABDC at .050" when running an LSX intake manifold. General Motors knows this better than anyone. Just look at their factory race cams:

ASA Cam: 226/236 110LSA (IVC of 43 degrees ABDC)
Grand Cup Cam: 239/251 106LSA (IVC of 45.5 degrees ABDC)

These cams make excellent power under the curve. Why? Because they pump up dynamic compression and close the intake valve within the window that the LSX intake manifold likes.

.

Originally Posted by Patrick G

For a dual-purpose street/strip car, a good benchmark is for the car to be putting down its cubic inch displacement in torque by 3000 rpm and make at least 1.25X its displacement in peak torque.

For a stock displacement LS1, that would mean 346 rwtq by 3000 rpm and a torque peak of 433 rwtq.

Similarly, a 408 would make 408 rwtq by 3000 rpm and 510 rwtq at its peak. Sadly, too many motors on this board (intended for dual-purpose) don't come anywhere close to these mid-range torque numbers and as a result, make poor area under the curve.

Originally Posted by gollum

Patrick, Everything you stated so far makes verygood sense. But can you explain why these GM racing cams have LOTS of exhaust duration? ASA and Grand Cup cars run open exhaust. It seems you would need less exhaust duration with open exhaust

Also, wouldn't the early opening exhaust timing hurt torque output?

Originally Posted by DAPSUPRSLO

So does the 1.25x number take into acount drive train loss? It would seem it does or is that being over looked?

Originally Posted by STOCK1090

Calculus

Originally Posted by Patrick G

The GM cars run lots of duration because this puts the overlap more toward the intake side of TDC which will allow the motors to rev well past peak hp.

When you narrow the LSA, it opens the exhaust valve later, which is one of the reasons the GM cams make excellent mid-range torque. Basically, if you run more exhaust duration, it typically means you open the exhaust valve earlier and close it later, but when you narrow the LSA, you can offset that earlier EVO by opening it slightly later, balancing everything out.

Originally Posted by gollum

So wouldn't a higher lift (LSK lobe) ASA style cam be a better choice for your current street combination than your new LSK 224/228 110 cam?

Originally Posted by joecar

What would the TQ/HP curves look like for a 1000HP Supra and a 1000HP LS1...?

Which one would you rather have...?

Having a large area under the torque curve makes for a very responsive street car (95% of time spent below 4000RPM).

Originally Posted by FieroZ34

But as we've been saying, area under the curve over the entire RPM spread has no affect on the car's performance--that's waht gears are for. Now take a 3000rpm cut from both graphs, and see which one's area is higher.