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Old 08-23-2016, 06:25 PM   #1
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MPG frustration

So from what I've gathered online, it seems like most DT466 users are getting roughly 9-12 mpg. Mine is still only getting 7.5-8, doesn't seem like the foot or towing the toad is making a difference at all.

My trip this past weekend was 600 miles, just myself and 3 guys. Not a ton of gear at all. I kept it at 60 the way there (2350 rpm), and noticed that I was getting pretty poor mileage. So on the way home decided to slow down to 55 (2200 rpm), and still only got 7.75 mpg.

A few things I haven't checked, tire pressure and fuel filter. But could either of these things really be hurting me this much?

The drive had hills, some of which required the pedal to the metal, but not too many more hills than I would expect a normal trip would have. Idk. What do you guys think
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Old 08-23-2016, 09:03 PM   #2
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depends on quite a bit. the gear you are in, the rpms you're going, tire pressure and wear on the tire, quality of fuel and oil as well as both of those filters.
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Old 08-23-2016, 10:51 PM   #3
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Originally Posted by BurlKing View Post
depends on quite a bit. the gear you are in, the rpms you're going, tire pressure and wear on the tire, quality of fuel and oil as well as both of those filters.
And air cleaner restriction... My gauge shows 2% resistance at this time.
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Old 08-24-2016, 12:24 AM   #4
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Worn injector nozzles can really cause the fuel to get consumes too. If the injectors don't atomize, it takes way more fuel to make the power.

What's your exhaust look like when climbing a grade? What's EGT look like?

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Originally Posted by bread519 View Post
So from what I've gathered online, it seems like most DT466 users are getting roughly 9-12 mpg. Mine is still only getting 7.5-8, doesn't seem like the foot or towing the toad is making a difference at all.

My trip this past weekend was 600 miles, just myself and 3 guys. Not a ton of gear at all. I kept it at 60 the way there (2350 rpm), and noticed that I was getting pretty poor mileage. So on the way home decided to slow down to 55 (2200 rpm), and still only got 7.75 mpg.

A few things I haven't checked, tire pressure and fuel filter. But could either of these things really be hurting me this much?

The drive had hills, some of which required the pedal to the metal, but not too many more hills than I would expect a normal trip would have. Idk. What do you guys think
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Old 08-24-2016, 01:59 PM   #5
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Your post doesn't tell anyone anything about your bus. We know what engine. What about the transmission, tire size, rearend gear ratio, miles on the bus. How about helping us help you.
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Old 08-24-2016, 05:52 PM   #6
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Transmission is MT643

Rear end is 4.78 (I listed the RPM so that should be sufficient anyways)

Mileage is 115k


I'm not seeing any smoke at all really ever. Except for when I first start the bus. The air filter gauge says I have plenty of life left, but idk how accurate that is

I do have a pyrometer, but it's not working
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Old 08-24-2016, 09:47 PM   #7
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Still didn't put all the info but I'll take a stab at it. The 4.78 is the same as one of my buses. For me, that is more of a ratio for an around town bus than a freeway bus. I drove back from Texas at speeds between 45 and 50 mph. I am comfortable having the engine at 2000 rpm. I think that is the sweet spot. This is not the same as a VW 1.9 TDI. I know they make a 4.44 and a 4.10 rearend. I am posting a link for you to check the rpm for different factor. You could also go up in tire size.

Engine RPM Calculator
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Old 08-24-2016, 10:06 PM   #8
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Still didn't put all the info but I'll take a stab at it. The 4.78 is the same as one of my buses. For me, that is more of a ratio for an around town bus than a freeway bus. I drove back from Texas at speeds between 45 and 50 mph. I am comfortable having the engine at 2000 rpm. I think that is the sweet spot. This is not the same as a VW 1.9 TDI. I know they make a 4.44 and a 4.10 rearend. I am posting a link for you to check the rpm for different factor. You could also go up in tire size.

Engine RPM Calculator

Yea that seems to be the sweet spot for me as well. I'll grab my tire size tomorrow I haven't been out by the bus today. I really want to change the rear end size I think. does anyone know where to start on finding the part #s I need? I will get the model # of the rear end tomorrow. I know it's spicer
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Old 08-24-2016, 10:13 PM   #9
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the slower you go the less wind resistance which is huge for most of our busses that have nearly 90 degree front ends.. ive done well running mine at 60.. but this next trip I may try 55 just to see if theres a difference.. since I have a 545 trans my RPMS tend to run up a bit anyway just due to the stall speed on the torque converter being at the max power-band of the DT-360

of course re-gearing to say 4.44 can help your top speed however it gives you less leverage against the road so you may run out of engine much easier on hills than you did previously... downshifting to 3 helps in that situation and ofcourse your top speed in 3 is higher wit ha different gear.. but in a bus im thinking you wouldnt go any taller than a 4.44? maybe im wrong about that... a 4.11 would definitely bring your RPMs down...

depending on availability of parts and cost to regear, aother option is a tranny swap to an over-drive unit.. a 1000 or 2000 series.. not cheap.. but i also know re-gears arent cheap depending on the rear you have also...

-Christopher
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Old 08-24-2016, 10:21 PM   #10
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I'll just sell it and get a different bus if I can't get 9-10 mpg at that point

I have 11 r 22.5 tires so with 4.10 gears I would have 2011 RPM at 60 mph which would be perfect I think. I don't mind slowing down for hills if I can go faster on the interstate which is the majority of my mileage in the midwest
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