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Old 03-13-2019, 12:52 PM   #1
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DT466E Max RPM

So I've gone through this forum and schoolbusfleet and a few other diesel forums, and I can't seem to get a decent figure on the DT466E's max RPM's. I can find a lot of claims and comfort levels, but nobody seems to have an actual nameplate max RPM and I can't for the life of me find it through navistar.

The engine is a DT466E from a 1997 Vista.

From here, some very well regarded members have stated they wouldn't push it past 2600 or 2500, while others give 2700+. However I can't seem to find an actual nameplate figure on my engine block or online stating what the manufacturers max RPM is.



For a bit of additional clarification, I've got the AT545 Slip-o-matic and prefer a average speed of 45 MPH. Not trying to push the bus constantly, but just trying to see if I'd be able to travel at a decent speed on highway sections with 50-55MPH limits which would put me at 2550-2650 RPM.


Any advice? Is 2650RPM safe for several hours, or would that be not advised?

EDIT: Added threads that I've browsed. Maybe I'm missing a good one or something.

I know the power after 2400 RPM goes right down, but just trying to get a feel of what I shouldn't push the engine to.

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Old 03-13-2019, 01:16 PM   #2
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Do you know if your bus has a speed governor on it? If it does it's possible you may hit that before you hit ~2600 rpms.

As for your question about if it is safe. Yes, it's safe to run it at high RPMs for extended periods of time. It was designed to be extremely robust. Of course wear and tear is going to occur faster at those engine speeds.
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Old 03-13-2019, 03:21 PM   #3
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Quote:
Originally Posted by rensch26 View Post
Do you know if your bus has a speed governor on it? If it does it's possible you may hit that before you hit ~2600 rpm.

As for your question about if it is safe. Yes, it's safe to run it at high RPM for extended periods of time. It was designed to be extremely robust. Of course wear and tear is going to occur faster at those engine speeds.
I was just checking numbers on a school bus I saw advertised - max hp was reached at 2300 rpm, and it was governed at 2500 - peak torque was at 1400 rpm - to travel at the sweet spot between max torque and max hp with a 5.57-1 rear axle ration, I'd be traveling at somewhere between 20 and 30 mph - that bus would definitely need a higher gear ratio ( lower number ) set of gears if I wanted to travel at the highway speed limit and not prematurely wear out the motor
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Old 03-13-2019, 03:30 PM   #4
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I'll have to look but I believe the max RPM is set in the computer at 2700 unloaded and 2600 loaded.. it makes its max power at 2300. so the only reason for ever running it past 2300 is to run-out a gear so when it up-shifts it will shift into the middle of the powerband.. . by nature of being ion a lower gear you are applying more torque to the ground in the lower gear. than you will once it shifts.. so you can bury the throttle and it will run up to the TCM (electronic trans) or pressure-valve-governor (mechanical trans) and then shift.. usually around 50-100 RPM below the redline of the engine..



theres no good reason to run sustained above the max output unless again for gearing.. ie you newed to climb hills in a lower gear and want to maintain speed uphill vs upshift and lose speed.. but travelling at leass than full load high RPM will just use extra fuel though it wont really hurt the engine per se'.


yes the computer can be altered with the right software to spin it faster... but why?



the book for my mechanical DTA360 (and also mechanical DT466) states that the DTA360 can be safely spun up to 2800 loaded / 2900 unloaded (foot to the floor neutral).. and that it wont Nuke itself if you spin it up to 3200 RPM by adjusting the governor springs.. however that anything above 2800 loaded will "significantly reduce" the expected lifespan of the engine... (yes it says that in the service manual)..


-Christopher
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Old 03-13-2019, 04:15 PM   #5
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Don't exceed 2600 rpm. It won't without you changing parameters in the ecu, so just don't.
I know you don't want BIG speeds but if you're redlining to hold 55mph its time for a gearing change or an OD transmission swap. That's part of the deal getting a route bus from NC.
You want your cruising rpm somewhere between 1800-2300ish. Your mpg's will go up if you lower your cruising rpm.
It won't kill it right away but your engine won't like life at redline.
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Old 03-13-2019, 04:48 PM   #6
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Thanks all, seems I'm going to be on surface roads until I do a rear end change.

They removed the limits at the lot, it was originally governed at 45 I believe.

Looks like I'm gonna be sticking to 45 for the time being on long trips, which isn't too bad on surface roads and honestly around the speed I prefer. That'll put me around 2300RPM for the majority of the time.

I'm okay rolling along at 45-50MPH on surface roads, just checking to see if it would be suitable to go for an hour or two at 55MPH/2600RPM on mountain highways without worrying about causing major damage.

The specific reason is I'm planning on going through the Appalachian mountains from SC to KY. This gives me three options - take the surface roads which have a lower speed but higher grades, take the highway with 50-55MPH but lower grades, or go around down to Atlanta and then up and around avoiding the mountains.

Outside of trying to find the lowest grade routes, and if given the choice of a flat road or flat highway, I'm always going to be taking the road. Even if I had a the transmission and rear end to go 70-80, I would not ever push it to that. Slow and steady is what I'm aiming for, although a slightly lower rear end would be nice to bring me to maybe 60MPH top speed for scenarios like this. Even taking a regular car I prefer non-highway/interstate routes, you get to see so much more stuff!


EDIT:

Just ran some numbers through this calculator using these parameters:

Engine RPM: 2300
Rear End: 5.39
Tire Height: 38.15 (265 75R22.5)

Gears 3.45; 2.25; 1.41; 1.00

This gives me 48MPH at 2300RPM, with the slippage and comparing to real world tests at 50MPH at around 2650RPM, I should be running around 45MPH at the 2300RPM in 4th gear.
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Old 03-13-2019, 07:44 PM   #7
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I ran my DTA360 at 2600 RPM for long periods of time without issue. as long as your fan clutch is good and set fairly low you will be fine... my DT360 liked to get warm in warm weather at higher RPM till I replaced my fan clutch and turned the temp down on it... you dont want your DT466 to get hot no how.. and you have probably seen the threeads from a couple of then that have been a little warm and it ruins the cylinder liner seals.. esp on #6 which gets the hottest... generally 230 is TOO HOT for a DT, however im beginning to think that sustained temps at 210-215 are about all id want to do.. my DT360 with good fan clutch goes up to 195, fan goes on and it drops to 185-190 or so... fan goes off..


just keep that in mind running at higher RPMs for extended periods..

-Christopher
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Old 03-13-2019, 08:09 PM   #8
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Thanks Caddy. My temperature seems to hold at just under 200 most of the time unless it's cold, at which point it tops out at around 190-195. Never actually seen it hit 210 on the dash or scangauge, even pushing 2650-2700RPM (for 10-15 minutes).
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