Just a thought...
Would a truck run guicker in the 1/4 with stock upper/lower pullies and a 6000+ rpm shift point, or an aftermarket pully and a lower shift point.

Theoretically, at say, 6000 rpms, wouldn't the blower be making the same boost as one w/ an aftermarket pulley at a lower RPM? RPM is usually the name of the game in drag racing.

Correct me if I'm wrong, but w/ a forged bottom end, isn't the safe engine operating range limited only by the RPM's of the Eaton, not the engine? It seems like this engine could survive 6000+ rpms....am I way off?

 

My gut reaction is that the area under the torque curve between the shift points and redline would be lower.

Tuners???

 

Kind of an interesting topic. There are many calculators you can use to determine optimum shift points, power ranges, etc... One day I used one of the better ones, to try to determine best shift rpm. I entered all my dyno power data, my gear ratios, and everything else it asked for. The calculator figred out the rpm that the truck would lose the least amount of torque on the shift. Pretty neat actually. The end result? 6000rpm Have I ever shifted my truck that high? Nope My testing has shown that anything over about 56-5700 did not gain any performance in ET. Also, according to Ford, the Triton motors can kick out a valve follower over 5400 and there is actually a TSB for idle miss from kicked followers. Now before you all call your chip makers and get your shift points lowered, let me just say that it does not make sense to me that our motors would kick a follower at such a low rpm. Out motors use the same exact heads and cams used on the 2v Mustang, and people are shifting those motors well over 6k with very few follower problems. As for the pulley thing, yes the truck would probably make the same boost at 6k with no pulley, but you would only have that extra boost for a few hundred rpms. With the pulley, you have more blower rpm all the time, so you increase power over then entire rpm band. Even though a larger crank pulley does create more heat at high rpms, you are still making more power.

 

I've always been told that the shift RPM will be dependant on the Hp curve. If you have a very peaky curve, you generally need to shift at a higher RPM, so that the engine will drop into the curve where there is still good power.

It seems with the flat torque and Hp curves that these truck have would be very forgiving. Personally, I think a 5400 RPM shift point would not slow the truck. When I change my lower pulley, I'm going to drop back to 5,300-5,400 to see how this works.

 

Thanks for the info Sal...

 

I don't know guys, my new programs been shifting aroudn what? 5600 to 5700 and it works awesome for me. Absolutley great shifts, and my trans is bone stock with those big heavy 20 inch chrome L wheels on there.

Thanks Sal

 

It also depends on what kinda cams Ford put in there... some cams are designed for a specific RPM range... aka the Operating Range...

Most are prolly ~1800-5200 in trucks (w/o blowers)

example, in my truck before the SCer, it would fall on its face at 5000, with boost, it did the same thing, but not as bad, now with a new cam and heads, it never stops pulling!

 

The higher the better on these trucks, but we do get to a point where we need to stop. I say 5500 to 5600 max.

I've gone over this extensively and shown why higher is better on our Lightnings, EVEN WITH A PULLEY the math still works out to the same basically.

Here read this and see my graphs I made up from various dyno plots of our avid fellow Lightning owners/board members:

https://www.f150online.com/forums/sh...threadid=34302

A quote from that thread I made:

That IS the correct way to shift a vehicle. You can use many a different ways to do it, but that above is the proper theory to go by. It's also common sense.

BfB