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Old 01-20-2019, 10:18 PM   #1
Skoolie
 
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Location: Santa Rosa, CA
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Chassis: CE300
Engine: DT466
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DT466 Torque & HP Dyno Charts

@CadillacKid - feel free to chime in here.

I am looking to enable 6th on an early 2006 model Allison 2500 (I -might- have to put new valves in) through PCM Performance but I noticed that still, even with 6th, the rear end is kinda high @ 6.17.

cruising at 65, the RPM in 5thOD and 6thOD would be 2375/2050 respectively. That only provides me a little room to pass as the limiter is set to about 2550RPM.

Main reason is milage, not speed. I'm happy cruising at 65, but would like to pass someone who is doing 62.5 (happens often).

So... I am looking for (google search didn't turn up what I'm looking for) the HP/Torque dyno charts for the 2006 DT466E 220HP engine. Along with that, since the torque is made at about 1400RPM and HP is about 2400RPM, what's the recommended RPM for cruise?

I want enough as to not lug the engine, while providing enough extra RPM to quickly accelerate and pass that slug - all while increasing MPG.

So I guess I am looking for a few things:
  • Dyno Charts
  • Recommended Cruise RPM to maximize MPG while not lugging the engine
  • Lowest gearing as to not affect starts (lots of stop and starts in windy mountain roads in Latin America for this Skoolie)
  • What's required to remove the RPM limiter on this beast?
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Old 01-20-2019, 10:34 PM   #2
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You are correct, those are pretty tall gears. I believe I have read various reports that recommend driving within 10-15% of peak torque of your engine. I'll see if I can back that up with any written evidence. But that likely won't be realistic for your bus currently. 1550-1600 rpms you'd be running much slower than you'd prefer.
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Old 01-21-2019, 06:51 AM   #3
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Quote:
Originally Posted by Pizote View Post
@CadillacKid - feel free to chime in here.

I am looking to enable 6th on an early 2006 model Allison 2500 (I -might- have to put new valves in) through PCM Performance but I noticed that still, even with 6th, the rear end is kinda high @ 6.17.

cruising at 65, the RPM in 5thOD and 6thOD would be 2375/2050 respectively. That only provides me a little room to pass as the limiter is set to about 2550RPM.

Main reason is milage, not speed. I'm happy cruising at 65, but would like to pass someone who is doing 62.5 (happens often).

So... I am looking for (google search didn't turn up what I'm looking for) the HP/Torque dyno charts for the 2006 DT466E 220HP engine. Along with that, since the torque is made at about 1400RPM and HP is about 2400RPM, what's the recommended RPM for cruise?

I want enough as to not lug the engine, while providing enough extra RPM to quickly accelerate and pass that slug - all while increasing MPG.

So I guess I am looking for a few things:
  • Dyno Charts
  • Recommended Cruise RPM to maximize MPG while not lugging the engine
  • Lowest gearing as to not affect starts (lots of stop and starts in windy mountain roads in Latin America for this Skoolie)
  • What's required to remove the RPM limiter on this beast?
1900 -2200 is good crusising rpm for a DT.

I've had highway gearing on most my buses. Its great.

WHy would you remove the rev limiter?
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Old 05-31-2019, 04:25 PM   #4
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Join Date: Aug 2018
Location: San Francisco
Posts: 112
Year: 2006
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Chassis: IC FE 9 Window
Engine: DT466E
Rated Cap: 29850
I went with 4.68. That made 4th equal my current 5th @ 6.17. I only downshifted once from Texas to San Jose and that was on Pacheco Pass (CA-152).

My only concern is "startability" in 1st.

The Calc =

(torque @ "clutch engagement" * 1st gear ratio * RE ratio * tire rev/mi) / (weight * 10.7)

Here is what I used-

Torque Guess = 420
1st = 3.51
RE = 4.68
RPM = 503
Weight = 22,000

Startability = 14.7 This is not good.

420 is a conservative guess value, 460 would get me above 16, I am just not sure what "torque @ clutch engagement" can be found.



=================================================


Reference:

o Startability is the drivetrain’s ability to get the vehicle and load moving. The lowest ratio’s gears must be numerically high enough to get the truck moving on a specified (in percent of grade) upgrade in “low” gear, and on flat terrain (first gear) without abusing the driveline or clutch. Startability is likewise expressed in a percentage number-although the percent sign is usually deleted-that refers to the amount of grade on which, if you stopped, you should be able to start moving again without causing any drivetrain damage.

According to one OEM, startability should be spec’d as a rating of at least 16 for general on-highway operations; 25 for moderate on/off highway service; and 30 for severe on/off-highway environments.
Calculating startability (referred to as “S” in the following formula) involves a formula that’s simpler to use than it looks:
S = T800 x Ra x Rt x M/(10.7 x GW)

In this case, T800 represents engine torque at clutch engagement (800 pound feet); Ra is the axle ratio (let’s use a value of 3.73 for this example); Rt is the transmission’s low-gear ratio (we’ll call it 12.45); M is the tire rpm (we’ll use 474), and GW is gross vehicle weight (we’ll assume 80,000 pounds here). The 10.7 figure is an engineering constant.
So, the math becomes: S = 800 x 3.73 x 12.45 x 474/(10.7 x 80,000) Or: 17,609,479/856,000 = 20.6
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Old 06-01-2019, 02:27 PM   #5
Skoolie
 
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Join Date: Aug 2018
Location: San Francisco
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The other option is to make sure I stay under 19-20K lbs with that the startability calculation works.

With the seats and lift she is 18.5K lbs. That lift is heavy and there is a 1000 lbs ballast weight behind the rear wheels (I'll replace with water or diesel tank).

I did the calc with the OEM rear end and my current estimate about matches the OEM setup when she is near her GVW max of of 29k lbs. Maybe I am just worrying too much.
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Old 06-01-2019, 04:45 PM   #6
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Chassis: 8 window
Engine: 454 LS7
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Quote:
Originally Posted by PeteinSF View Post
The other option is to make sure I stay under 19-20K lbs with that the startability calculation works.

With the seats and lift she is 18.5K lbs. That lift is heavy and there is a 1000 lbs ballast weight behind the rear wheels (I'll replace with water or diesel tank).

I did the calc with the OEM rear end and my current estimate about matches the OEM setup when she is near her GVW max of of 29k lbs. Maybe I am just worrying too much.
what did the bus weigh when it was full of students, and was it able to get around then? - l doubt they would make a bus that was unable to move a considerably lager load than what the bus is rated for
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