Setup to reach 9.66 MPG at 65 MPH ?

[someguy]

Very misunderstood in busnut circles is the progression of the engines through the various emmissions regimes.

Any particular engine, you have to know what it was designed for, and what rpm is intended to deliver the power and fuel economy compromise for the vehicle it is going in.

Truck guys generally don't know about buses either..

Knowing that engine is really important, for instance, some of the last Cat motors, if it was run as little as 100 rpm away from the magic rpm, the fuel consumption curve was "V" shaped, and would bankrupt the fuel budget.

Generally speaking, the older it is, the faster it spins, the newer it is, the slower it may be spun.

Also, the whole Allison transmission thing will bite busnuts hard in the future. Just buying a "B500" or "4060" off someone cheap...They are not all capable of aggressive downspeeding, a whole ton (maybe 2 decades decade's worth?) of them can't spin below 14xx rpm, the lube pump in them was never intended to maintain it at cruise any slower. Lets be fair, cruising at 1500 was quite magical back in the day...

So, you have to have the right Allison to match the right engine.

Lots of research of information not readily avialable anywhere but a grizzled veteran at the manufacturer.

Happy coaching!
Buswarrior

Well said.  I especially agree with the B500 stuff.

I found the Cummins spec sheet for the ISM410 EPA2007 engine. 
It says:

"For maximum fuel economy or for vehicles intending to
cruise greater than 65 mph, gear for an engine speed of
1500 rpm at the 65-mph checkpoint (1600 rpm for the
ISM 410)."

[luvrbus]

I am @ 1250 rpm @ 65 mph I drove a friends new J with ISX 12 it was 1100 rpms @ 65 mph,ISM Cummins are popular in RV's set @ 500 hp 

[Jim Blackwood]

So then just drive it at 65 or 70 and don't worry about it huh?

Jim

[someguy]

Cat's take on RV fuel economy.

[luvrbus]

Cat's take on RV fuel economy.
[/quote

Cat used to be at all FMCA conventions for RV's all 3 were CAT,Cummins and Detroit with their sales pitches with movies lol even pop corn,the problem CAT had was all their engines were developed for equipment and they adapted those engine for highway use some times it worked great other times it didn't 

[buswarrior]

Cat's take on RV fuel economy.

Cat's 2005 printed materials...

You can't talk engines without the qualifier.

Happy coaching!
Buswarrior

[someguy]

FYI, a 2006 E4500 with the ZF AS Tronic 12 speed transmission cruises at 1330 RPM at 65 MPH, based on tires with 490 revs/mile, 0.78 OD ratio and 3.21 axle ratio.

In 11th gear (1.0 ratio), the engine runs at 1700 RPM at 65 MPH.

In 10th gear (1.27 ratio), the engine runs at 2100 RPM at 62 MPH.

10th gear at 55 MPH is 1831 RPM, which is full power for most engines.   A 40,000 pound coach takes 475 wheel HP to climb a 6% grade at 55 MPH.

FYI, the only difference between the 10 and 12 speed ZF AS Tronics is that the 12 speed has 2 extra creeper gears and 2 reverse gears instead of 1.  The gear ratios of the upper 10 gears are the same in both.

The ZF AS Tronic 12 speed has nearly identical spread as the standard Eaton 10 speed, except the 12 speed splits are 25-32% whereas the 10 speed splits are  35-40%.  On average the ZF splits are 8% tighter. 

At 1500 RPM, 8% is 120 RPM tighter.  With a standard 10 speed the 40% splits are 900/2100 RPM.   With the ZF the splits would be 32%, which is 1020/1980 RPM.  Nobody shifts at 1500RPM, I'm using that to show the ZF can stay in the rev range whereas the 10 speed can't.

If the transmission shifts at 1800 RPM, the ZF picks up at 1224 RPM, whereas the 10 speed picks up at 1080 RPM.   The C13 makes constant torque from 1200 to 1500 RPM and peak HP at 1800 RPM.  So the ZF shifts fit within that peak torque to peak HP band whereas the 10 speed makes the engine go beyond peak HP (to 2000 RPM) in order to pick up the next gear at peak torque.

I cannot wait to haul @$# up hills with a decent transmission for once.  Not that I want to race up hills fast.  I just want some gear ratios to let the engine do its job without revving its brains out.

[buswarrior]

Did you do the math percentages in the correct direction? Your rpm drop calculations are WAY too big.

The paper can say what it wants, none of these engines will "make power" up near the top of the rpm range. Spinning them up there doesn't make much push... but it sure will consume fuel.

You do kniow that HP is a marketing number, always has been. Where's your torque... stay there.

As for the ZF 10/12... what differentials were being put behind/infront of each, i ask rhetorically...? You don't suppose the lower gears were to allow a taller diff to get cruise speed down, without losing startability...?

The 12 speed will start off in 3 and even 4 from a stop, and skips gears all the time, it doesn't touch each one .

Keep going, you have a ways to go yet...

Happy coaching!
Buswarrior

[lostagain]

In practical every day terms, the ZF A S Tronic transmission was not a nice transmission. Most driver's hate it. It shifts quite roughly in stop and go traffic in town. It will rattle the dishes in your cupboards. Like BW says, it rarely starts in 1st or 2nd, and skips gears according to conditions. It doesn't always know what gear to be in. You have to baby it with manual shifts. I would just look for an Allison B500. Smooth, always in the right gear up or down.

[luvrbus]

If I wanted a 10 speed auto shift I would skip the ZF  and buy the 10 speed Allison,I haven't figured out why Allison is not letting bus manufactures have the 10 speed yet ,I know they were testing those in buses 

[someguy]

In practical every day terms, the ZF A S Tronic transmission was not a nice transmission. Most driver's hate it. It shifts quite roughly in stop and go traffic in town. It will rattle the dishes in your cupboards. Like BW says, it rarely starts in 1st or 2nd, and skips gears according to conditions. It doesn't always know what gear to be in. You have to baby it with manual shifts. I would just look for an Allison B500. Smooth, always in the right gear up or down.

Meritor rebranded the ZF AS Tronic as the Meritor Freedomline transmission.  It is a really good transmission, almost as good as the Volvo iShift.  In fact, Volvo used it behind the D13 for a while.

Meritor had to cease selling it because some of the technology infringed on US patents held by Eaton.  Meritor ended up paying Eaton $500M to settle.

There is no reason for a PROPERLY working AS Tronic transmission to shift roughly.   The AS is a manual transmission with shift rod actuators on top of it.  Not an XY box like the Ultrashift.  It does not shift under power.  Any jerkiness you felt was from the clutch releasing awkwardly.

Generally if the AS is shifting poorly it is because the clutch isn't set up properly or has been abused.   That happens if drivers use the throttle pedal to hold the vehicle like they would the torque convertor.  In a vehicle with a properly working clutch, they shift super smooth, up and down.

Why use an AS over a B500 ?

- more gears / better gear spacing
- less heat.  The AS doesn't even need a cooler
- about 400 pounds lighter
- more efficient
- lets the engine lug and use its torque
- less expensive to replace
- I could rebuild one if I had to
- works better with the exhaust brake

I hate automatic transmissions.  Especially Allisons.

BTW, you can't even get a manual transmission in a new Volvo VNL.  They are all iShift.

[someguy]

Like BW says, it rarely starts in 1st or 2nd, and skips gears according to conditions. It doesn't always know what gear to be in.

The 12 speed starts out in 3rd, where it should.  1st and 2nd are creeper gears.  The operator can manually jog to whatever start gear he wants, up to 4th, I think.  They skip shift quite well.   Sounds like the transmission you were running wasn't set up properly.  3rd in the 12 speed = 1st in the 10 speed.

There is a setup file for both the engine and the transmission controllers.  Everything is tunable, but the off the shelf settings should work fine.   Not sure what was wrong with the transmission you drove.  One of the parameters in the transmission setup file is the default start gear.

[Jim Blackwood]

Most drivers are wrong apparently. Aren't y'all glad there is someone around to point that out?

Jim

[someguy]

See Section 3 Maintenance.  Page 53.  Release Fork Greasing Procedure.

Section 5 has calibration procedures if the shift solenoids are ever opened up.  But unless the transmission is jerking because it is being shifted under power, that isn't the problem you are describing.   What you are describing is a clutch issue.

All the actuators in the AS are pneumatic.  The flow to them is controlled by solenoids.  If the solenoids are dirty they might respond in a jerky manner.

FYI, both the Ultrashift and the Ishift use electronic clutch actuators and they fail periodically and are expensive.  I think it is good that the AS uses a pneumatic clutch actuator.

[6805eagleguy]

Another advantage with the b500 is full boost throughout shifts,

I'm running 1450 rpm at 68mph with 3.73 rearend in 5th gear

Trying to keep up with sonnie greys bus lol