Every time I step on that darn fun pedal in 2nd gear I over rev per the tach. Are the tachs accurate? After 2 or 3 times of over revving I don't even hit the pedal till I am in 3rd which sucks.

The truck continues to pull and revs quite quickly to 3500 rpms. What are other 6 spds seeing?

Are there rev limiters for diesels?

 

the only way you can over rev the engine is by going downhill with a load and it overcome a no fueling state and keep driving the RPM up , you cant not over rev the engine by free reving it , it will go into a no fueling state. now this info is for electronic engine only.

 

John, maybe the 04's and up will defuel but my '03 will also over rev any time my foot is in it, od off or on, flat ground, uphill, downhill. Yea, it surprised me too the first time I saw 3600 r's. It will also over rev in park. I tried that one time just to see if it would.

 

The engine will not over rev with the accelerator pedal. Even a (stock) mechanical diesel will not run faster than the manufacturer intends unless you downshift at too high a speed and dump the clutch. All diesels have a governor that keeps the RPM in a range that the manufacturer has deemed safe. Don't worry about what it says on the tach, if Cummins didn't want it to rev that high they would have programmed it to defuel earlier.

 

just like Wanna said , it will not over rev. what your seeing is the tach. needle going over. not the engine...... I just had a cust. with N14 yesterday complaining about his engine overreving. once hook up to Insite, I just nail the throttle to the floor and held it there and Insite was reading 2200 rpm and his tach was reading 2500. LOL it buried the tach on the first second and settle back down to 2500. yes mechanical engine also have governors, and there are lots of kits for changing the governor limits with the mechanical and can have a mechanical malfunction also. with the electronic engine.. it is all written into the calibrations and have never seen a malfunction since they have come out.

 

i will sometimes put the pedal on the floor in all gears (2nd-6th) and i do not have that problem. When the tach hits 3k i let off push in the clutch and repeat in the next gear. I never have any problems.

 

drew it comes up so quick I don't think I can shift THAT fast (only in 2nd).

So what I am hearing is the tach is not accurate or not keeping up. hmmmm, are there aftermarket tachs for diesels? The last thing I want to do is spin a bearing.

 

You won't hurt the engine. The computer will not let you use the accelerator to over rev (go over Cummins' max RPM rating) for the engine. Run it as hard as you want and ignore the tach. Shift when it stops pulling.

Again, you cannot over rev a modern diesel with the accelerator - even in neutral - the electronics will not let you do it. Dodge's opinion of max safe RPM may differ from Cummins', but who do you trust?

 

he right there is a rev limiter

 

we do numerous test with the ISB in nuetral and high idle. high idle is foot to the floor. max rpm..... such as fuel restriction. so no you cant hurt the ISB or any diesel that I know of.

 

I read somewhere that these cummins engines are rated for 4500 rpm's under a downshifting type of overrev. not under a load but that gives you an idea of the rps this motor will endure for it's whole lifespan..... and a very long one at that!! I also remember someone telling me the break-in procedure for these motors and if it can handle that in the first few seconds of its life when everything is new and tight then I don't think I can hurt it!!!

 

my truck has seen 3800 downshifting... 3500 upshifting... no harm done

 

Underwood , your right , we never let a new inframe or engine overhaul idle more then 5 mins. before it goes on the dyno and gets a hard workout.

 

So is it ok do down shift, and let the engine rev, I always thought that was a bad thing.

 

As long as your not letting the engine rev to 3800+ rpm's when downshifting then it's fine. I've down shifted every manual I've ever driven and everyone I know with a manual downshifts and I've never heard of an engine or a tranny getting hurt by it.