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Old 03-13-2019, 01:52 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, 02:16 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, 04:21 PM   #3
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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, 04:30 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, 05:15 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, 05:48 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, 08:44 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, 09:09 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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Old 04-25-2019, 10:20 PM   #9
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Colorado bus help me with rpm's.

We are about to complete our skoolie and take it on a shakedown trip. We bought it in AZ and it's geared to run 70+mph the whole way back to Denver without pushing the rpm's high.. My question is this.. when going down a steep mountain grade I try to keep it in a lower gear to slow the bus naturally... However as it's a 40 foot 23000lb bus when we are done it seems to want to speed up. What is the rpm I can ride down a mountain to use the air brakes sparingly. I have 1999 international pusher with a dt466e and Allison 3060. Thanks for any advice. I feel like maybe I was too cautious with the rpm's which is why it was speeding up on decents from AZ to co.
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Old 04-25-2019, 10:27 PM   #10
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Quote:
Originally Posted by AaronTSchultz View Post
We are about to complete our skoolie and take it on a shakedown trip. We bought it in AZ and it's geared to run 70+mph the whole way back to Denver without pushing the rpm's high.. My question is this.. when going down a steep mountain grade I try to keep it in a lower gear to slow the bus naturally... However as it's a 40 foot 23000lb bus when we are done it seems to want to speed up. What is the rpm I can ride down a mountain to use the air brakes sparingly. I have 1999 international pusher with a dt466e and Allison 3060. Thanks for any advice. I feel like maybe I was too cautious with the rpm's which is why it was speeding up on decents from AZ to co.
what model of an automatic transmission does your bus have?
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Old 04-25-2019, 10:28 PM   #11
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On a DT466E, you dont want to run it higher than 2600 RPMS. If you're cruising down a hill, just stab the brakes to get the RPMs down...
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Old 04-25-2019, 10:33 PM   #12
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That is also what I was wondering since I don't have the experience.... How much breaking will cause them to overheat. I am a cautious driver and stick to the right lane and go slow, especially down hill, but I am new to air brakes... So I am ultra paranoid they we're going to over heat although naturally I was stabbing the brakes.
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Old 04-25-2019, 10:57 PM   #13
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As long as you dont ride them, you should be fine!

On a long downhill grade, pick a speed range - let's say 35-45. Downshift to get in that range, then just stab the brakes to get back down to 35. Let it go back up to 45, then stab again to bring her back down to 35. Obviously, pick the speed and gear that is best for the grade/conditions, but you should be good to go...

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Old 04-25-2019, 11:00 PM   #14
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Also, the transmission model is very important as well... if you have an MT643, 2000, or 3000 series(lockup torque converter), that will be even easier! If you have an AT545 (non-lockup torque converter), downhill shifting will be much more precarious.
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Old 04-25-2019, 11:21 PM   #15
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I have an Allison md3060
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Old 04-26-2019, 01:09 AM   #16
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I have an Allison md3060
Excellent! That is one if the most desirable transmissions...just set a gear that gives you a comfortable speed and enjoy the ride!

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Old 04-26-2019, 08:02 AM   #17
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2600 RPM is max.. and dont try to downhill at the fastest speed.. SLOW DOWN!.. dont be in a hurry... if you climbed the hill at 35 with your foot to the floor dont go tryin to downhill hill at 55-60 on a steepo downgrade..



dont let the engine try to run above the 2600 RPM.. The transmission WILL UPSHIFT on you even though its set at a lower gear... the TCM is designed to upshift on a max RPM no matter what.. and wont downshift if it will put the engine above the programmed max RPM..



KNOW THE TERRAIN! - read about the grades you are going up and down before you get there.. trucker atlasses and websites do a good joib of describingthe freeways and grades.. so you know how long and what % of a downgrade to expect on the other side of your uphill climb..



I spent some time studying the grades of I-80 before i ran my 40 year old Gasoline AT545 equipped bus across it last year..



Screw the cars and truckers who try and push you to drive fast... hang out in the right lane and drive the speed you feel comfortable going up and downhill.


on the upside of the hill DONT get your DT466 Hot... 230 degrees Can destroy that engines liner seals.. while it doesnt happen every time.. we have seen several instances here on this forum of people running the temp gauge to a mere 230-235 and rebuilding their engines as a result... the alarm in the computer doesnt sound till you hit 230 or 235 (ive seen them programmed both ways).. at that point you are good and hot.. .. if you get close to that temp... slow down or pull over and idle the engine till it cools off.. dont turn the engine off unless you are sure there's a catastrophic failure such as coolant spraying all over.. or you feel you have lost the belt.. otherwise idling will let the fan and water pump cool the engine down..

downshift on the uphills too.. let there be a few RPM's.. ther allisons love to get into the highest gear they can as fast as they can... dropping down a gear or two and running with your foot not floor-boarded and RPMs in that 2100-2300 range uphill helps the fan do its job to keep your engine cool and doesnt lug the motor which causes very high cylinder temperatures..


others have commented about braking... Stab and go is how I brake on hills.. I start out at the top at a very slow speed.. and only allow myself to slow gain speed as i go down depending on the curves and length of the grade... I allow myself to be going faster at the bottom of the hill than I started out.. but I only slowly gain speed... ie as i go down if my speed goes up 7 MPH.. I will then stab it down 5 MPH... let it go up 7, stab it down 5.. by stab irt down.. I brake fairly firmly (though not Hard or harsh).. then I let off the pedal while spoeed builds.. this allows the drums and shoes to dissipate heat.. riding the brakes keeps things hot...





-Christopher
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Old 04-26-2019, 08:27 AM   #18
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Originally Posted by cadillackid View Post
2600 RPM is max.. and dont try to downhill at the fastest speed.. SLOW DOWN!.. dont be in a hurry... if you climbed the hill at 35 with your foot to the floor dont go tryin to downhill hill at 55-60 on a steepo downgrade..



dont let the engine try to run above the 2600 RPM.. The transmission WILL UPSHIFT on you even though its set at a lower gear... the TCM is designed to upshift on a max RPM no matter what.. and wont downshift if it will put the engine above the programmed max RPM..



KNOW THE TERRAIN! - read about the grades you are going up and down before you get there.. trucker atlasses and websites do a good joib of describingthe freeways and grades.. so you know how long and what % of a downgrade to expect on the other side of your uphill climb..



I spent some time studying the grades of I-80 before i ran my 40 year old Gasoline AT545 equipped bus across it last year..



Screw the cars and truckers who try and push you to drive fast... hang out in the right lane and drive the speed you feel comfortable going up and downhill.


on the upside of the hill DONT get your DT466 Hot... 230 degrees Can destroy that engines liner seals.. while it doesnt happen every time.. we have seen several instances here on this forum of people running the temp gauge to a mere 230-235 and rebuilding their engines as a result... the alarm in the computer doesnt sound till you hit 230 or 235 (ive seen them programmed both ways).. at that point you are good and hot.. .. if you get close to that temp... slow down or pull over and idle the engine till it cools off.. dont turn the engine off unless you are sure there's a catastrophic failure such as coolant spraying all over.. or you feel you have lost the belt.. otherwise idling will let the fan and water pump cool the engine down..

downshift on the uphills too.. let there be a few RPM's.. ther allisons love to get into the highest gear they can as fast as they can... dropping down a gear or two and running with your foot not floor-boarded and RPMs in that 2100-2300 range uphill helps the fan do its job to keep your engine cool and doesnt lug the motor which causes very high cylinder temperatures..


others have commented about braking... Stab and go is how I brake on hills.. I start out at the top at a very slow speed.. and only allow myself to slow gain speed as i go down depending on the curves and length of the grade... I allow myself to be going faster at the bottom of the hill than I started out.. but I only slowly gain speed... ie as i go down if my speed goes up 7 MPH.. I will then stab it down 5 MPH... let it go up 7, stab it down 5.. by stab irt down.. I brake fairly firmly (though not Hard or harsh).. then I let off the pedal while spoeed builds.. this allows the drums and shoes to dissipate heat.. riding the brakes keeps things hot...





-Christopher

Man, I gotta find a way to save this info for when I need it in a couple months. My brain can only hold onto so much information! I know I'll never find this post again when I'm in the thick of mountain driving. Off to the App Store I guess?
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Old 04-26-2019, 08:48 AM   #19
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Lol.... Yep, people think you can fly up a mountain like in a car. I am fairly mechanically inclined so I understand heat, rpm, etc. And why you want to o go up slow and start the decent even slower.. I am also not worried about other drivers as most of them realize a 40' bus needs to go slow. The downhill I am worried about is one that averages 6-7% for 4-5 miles.. it's a doozie. Lol. Gives me anxiety ������
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Old 04-26-2019, 08:54 AM   #20
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Just came off a trip through the smokey mountains and seen many truckers showing me their middle finger. Not sure why maybe they all pick their nose with that finger and where flipping something off it.
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