It is my understanding that the LLY engine hits peak torque at 1600 RPM (dunno what it is for the LB7). But whenever I see dyno charts (typically on web sites for programmers or exhaust systems), I'm seeing the charts hitting max torque at 2200 - 2400 RPM. Is there something that I don't understand about dyno charts, or does the engine actually max out at the higher RPM? Does anyone have a "dyno for dummies 101" link? :confused:

Thanks,

Joseph

I am not 100% sure but I would hazard a guess that the way they do dyno tests you are not seeing the turbo spool up until later on in the RPM range. They typically do the tests in 4th gear from a rolling start so it takes a bit to get everything wound up. I would think you would need to do some kind of pull down test to see the torque at the lower RPMs. This is just a guess though, someone with more dyno expereince from me will clear it up for you.

I am not 100% sure but I would hazard a guess that the way they do dyno tests you are not seeing the turbo spool up until later on in the RPM range. They typically do the tests in 4th gear from a rolling start so it takes a bit to get everything wound up. I would think you would need to do some kind of pull down test to see the torque at the lower RPMs. This is just a guess though, someone with more dyno expereince from me will clear it up for you.

:exactly: .

I agree with Max Power. I noticed the same thing a few weeks ago when I got my truck Dyno'd, max torque was @ 2000-2100 rpm.

Pulling downward will typically yield better results, but is quite difficult to do vs an accelleration test. A manual trans is better suited to this as the Allison wants to shift all the time. The pull down test does still show TQ peak generally at an rpm higher than rated in my experience.

So, how does this translate to the real world? If I install a programmer that shows a TQ peak at 2200 RPM, does this mean I want to cruise down the freeway at 2200 RPM for best performance (ignoring wind load issues, for the sake of simplicity)? Or is this one of those "it depends" kinds of questions?

Joseph