[cmitchell17]

I am trying to test combinations in DynoSim so I can get answers on the most optimal cam combination on the LT1. The simulation requires the MIN/MAX cross sectional area on the intake and exhaust runners. From the Corvette team's LT2 presentation I was able to get the intake runner length (assuming it doesn't include the intake port) as well as the "taper schedule". I went out and measured the exit on my intake manifold as well. To find the MIN intake runner area, I assumed it occurs right before the valve guide area, so I took what I knew from the LT2 presentation and did the best I could trying to measure the intake port on my heads (I have TSP CNC LT1 heads) with some snap gauges and drew out a spline curve in CAD:


I think I get a somewhat decent numbers for the intake:

Although I'm not sure if GM intended the taper angle at .8 degrees, which is what you get if you do the trig on the "taper schedule" numbers from the LT2 presentation, so there is still a lot of unknowns that can significantly effect the numbers.


However, I am having a lot more difficulty with the exhaust port/runner/header/collector dimensions. I did the best I could digging up info from old threads where people measured the insides of the cat pipes, but the numbers I am using don't seem right since the simulation calculation is going unstable. I know the stock headers are a try-y, and I think they do in fact taper throughout the collector, but DynoSim just doesn't like the numbers I come up with:

So does anyone have better numbers for the exhaust runner and collector lengths and pipe diameters?

The HP and torque output I am getting now is pretty low:

The output DynoSim gives should be gross output, I can't imagine that the LT1 water pump, altenator, and ac compressor could eat up more than about 10-15 hp, but the numbers I am getting above still don't meet the stock J1934 SAE output numbers. They are also early on peak HP and torque by about 200-400 rpms, so I still probably have errors in my intake runner dimensions as well. You can see where I highlighted the calculated exhaust port pressure after the exhaust valve, the simulation bounces around and won't converge on a solution in that area and makes me think something is really screwed up on my exhaust dimensions, and/or they are just not realistic.

Also I would be happy to run anyone's build combinations once I can nail down and get the stock LT1 output and be confident in it. I can simulate your build and run your combo through the built in iterator to spit out the most optimal cam valve open/close points.