I really just plain old blew a shift today and couldn't figure out why I was pushing the go pedal and I wasn't moving (it's been a really long couple of days). Anyway, I really hit the go pedal and realized that (I think) I hit redline on the truck. Question - do these things have a rev limiter to keep idiots like me that miss a shift from frying their engine? If it doesn't have a rev limiter, do you think I harmed anything? I only had it up above 3K somewhere for a second or two before I realized what I did....

 

OUCH , but I dont think you done anything to it if it was for only a couple seconds. Dont know about the rev limiter but I think they dont but not 100% sure. I would just be a tad more careful

 

Won't run faster than 3200 rpm. It will run 3200 all day long and won't hurt anything. You can't possibly over rev you're cummins.

 

didnt a cummins tech .. or? , say they test the cummins at 3500 rpms all day long or something?

or was it 4,000? but thats probably pushin her

 

Spinning donuts in the desert, I accidentally hit around 3500rpm. On the street, it feels like it starts to defuel or at least lose power around 3000 or just over. No, these rev's are not something that I do to my truck everyday.

 

you wont hurt a thing , we always run these engine at full throttle in neutral. we call it high idle. lot of our testing is done in high idle.

 

Almost, but not quite true.

It's true you can't over-rev your motor simply with the GO pedal, however if you were to shift into 2nd while you're going 70mph and let the clutch out... well that's another story.

I once saw a gasser come flying into a parking lot where I worked and he must have mistaken 1st for 3rd, because after a brief tire chirp all I saw was smoke and heard crunching noises as if he threw a rod. That said, it would be really hard to over-rev your cummins unless you're just a dolt.

 

As far as a Rev Limiter, I'm not sure.

However, the 3 Gens do have a Speed Limiter on them. BD make the Ram Speed Eliminator to get around the speed limiter. It also by-passes the "Torque Management" in the vehicles computer. This allow you to get full torque at low RPM's.

 

anything is possible , but your not going to over rev the engine with just throttle, we get engine blown from over reving and owners saying they dont know why it blew , but we also get a snap shot and find that the truck was going way to fast for the gear it was in and the brakes were applied. most cases they were going downhill to fast. I do remember one time in the old days a 8V71 Detroit that was rearended by another truck and threw a rod thru the side.

 

3200 RPM is all that I can get my truck up to. After that, PCM starts defueling. Some people will tell you that running your truck at 3000+ RPM is dangerous. I just don't buy that.

Every piece of the PCM programming has been approved by the engineers AND lawyers at Cummins. They are always going to be conservative with thier programming. If they set the limiter to 3200 RPM, its because they tested, retested, and tested some more at running that engine at those levels (probably more than you or I will ever do) for extended durations. If they say its safe, I believe them.

I don't tow a lick, so to work my engine, from time to time I'll rev her up to 3000 or so to work the engine a bit and get her a little hot. Only do this for short distances (say 1/4 mile), and do it mainly to keep things loosened up. It really is the only way I can put a load on the engine. The Cummins doesn't miss a beat

Now, the bigger question is why did Dodge put a 5000 RPM tachometer on the truck if you can't get over 3200 ?

 

My '03 has a rev limiter on it. I got bored one day and wanted to see if it had one so I bumped it in neutral and put it on the floor. It turned to about 3400 or 3500 and wouldn't go any further. That said, I've never hit the rev limiter while driving the truck aggressively.

 

On my 04.5 HO 600 the max rpms the Attitude reported from a dyno run was 3395. I have seen it a little higher than that and the OD reading 110mph. The 315s and 3.73 gear produce effective 3.43 ratio. It did not feel like it was defueling at 110mph and about 3450rpm, but that is when my chicken limiter kicked in .

 

i've turned mine about 3800 downshifting, and up to about 3500 in low gears upshifting... the ecm is the governor of the engine... on the throttle, there is no way to over rev the engine... off the throttle or with external un-metered fuel, the engine can go over speed...

finally someone else calling governed rpm high idle...

having your engine turn 1000rpm isn't high idle, it's fast idle in my books...

 

Right, High idle is 3500 (where computer won't let you go past in neutral.

You can overrev by downshifting.

Power will fall off past 2900 (the rated speed i.e. max hp).

 

Actually, the 03/04's start to defuel at 2750 or so gradually down to some amount that isn't enough to keep the truck accellerating, effectively limiting the top RPM while you're in gear. It could be defeated with some ECM programming but nobody seems to be willing to step up (BullyDog!).

Andy