What is safe RPM to turn

[DAVe3283]

So why under power is the redline 3250 but under grade braking it is 4800? Might be easier on the motor like I was saying earlier?

I believe this is why:

It is all sort of a moot point for a stock engine, as fuel and air run out well below 4800 RPM (I loose a significant amount of airflow by 3400 RPM according to my logs).

The stock turbo is too small for that much airflow, and the pulsewidth gets too big to keep smoke down. And GM didn't want much (if any) smoke from the stock duramax.

I spin my engine to 3600+ RPM once in a while, and even with 26 degrees timing and only 2200 uS pulsewidth it smokes like a freight train. The boost drops like crazy once I hit 3400 RPM, and anything above 3800 RPM just doesn't make much power, and I'm better off shifting to the next gear. So I would not be too surprised if this was the reason GM only fueled to 3250. But I could be wrong...

 

[GeneralTJI]

spin my engine to 3600+ RPM once in a while, and even with 26 degrees timing and only 2200 uS pulsewidth it smokes like a freight train. The boost drops like crazy once I hit 3400 RPM, and anything above 3800 RPM just doesn't make much power, and I'm better off shifting to the next gear. So I would not be too surprised if this was the reason GM only fueled to 3250. But I could be wrong...

I have pretty similiar results revving the piss out of 4th gear to keep out of 5th/6th. Boost drops, smoke increases, egts rise etc.

 

[IOWA LLY]

http://www.youtube.com/watch?v=UMxN3QzLsvs

This was over 4500 rpms, with completly stock heads. This charger makes plenty of power at 4500+ too.:thumb:

Surely not stock valve springs though right...?

If so that's pretty wicked that you can run that much boost and those kind of r's.

 

[bullfrogjohnson]

I've spun mine to 4500 numerous times with bone stock internals and no problems yet. But my charger will flow at that rpm. I am interested when I tear into it if there is any piston to valve contact. Josh spun his motor to 5200 rpms when his input shaft broke at the track with stock valve springs. There was kiss marks on all the pistons from the valves though:rofl:

But like everyone has said there is no reason to spin a stock charger that high. It wont do anything but build heat and overspeed the charger.

 

[Rhall]

Surely not stock valve springs though right...?

If so that's pretty wicked that you can run that much boost and those kind of r's.

Completly stock, springs and all, not by choice tho. Had a problem with my other heads.

 

[xcablb7]

i've pulled before and simply cuz i wasn't paying attention the motor was singing 4500 all the way down the track, a few times not that it made power there but wheel speed was up, and i've seen a flare to 5187, so i guess we could say it's not the end of the world don't do it on the regular but if it happens pulling out of the muck don't sweat it

 

[Vasbinder]

Yep the PPE is messed up. I tried to log with it and it said to call them. So I'm just going to take it easy and leave it in drive and tow haul and Gett'r Done. Thanks for all the info to help this Noobie out.

 

[06SIXSPEEDMANUAL]

Is that on your ZF-6 truck? Holy crap lol.

Yeah that was my Zf truck. I ended up breaking a rear axle shaft before that pass was over too

 

[Ben46a]

My stock ZF6 LLY has seen 4800 many times, hell i spin it that hard backing up when plowing snow to get the speed up, Never had an issue, over 110,000 miles on it now.

 

[duramax3388]

i would see up to about 4k out of my old truck sometimes more limter on that was set at 4500 never seen that much tho. here is alittle video of it. six speeds love rpm http://www.youtube.com/watch?v=GP_itFL_UXU