LMTV Alternator Disaster, engine now catastophic

[aleigh]

My vote is for an 8.3 Cummins! Tuned to 300hp. It would have great mpg compared to a rapped out 6.6 running at its high end for hp.

But will it fit. Not a lot of room under the cab...

 

[snowtrac nome]

I would leave the cat maybe tune it up to around 300 hp. Replacing with a like engine will be a lot less work. When the 363 ford diesel took a dump on my snow cat, I went looking for another one. I had a 6 b cummins on the floor but that would have required a re engineering of the whole thing. Putting the engine in is easy, the fun comes with hooking up all the accessory's, which can get expensive real quick

 

[coachgeo]

But will it fit. Not a lot of room under the cab...

vote this too.... and make CAD drawings of all the brackets and mounts and share with us

 

[aleigh]

I admit I am getting pretty 6CTA + P7100 curious.

 

[coachgeo]

I admit I am getting pretty 6CTA + P7100 curious.

confused? Both 8.3 and 5.9 have the P7100 pump (slightly different specs for each though)

 

[aleigh]

I specified because the Bosch isn't the only pump available.

snowtrac is right that sticking with another 3116 is easiest, but, the 6CTA engines seem to be cheaper (absorbing the costs of having the charge lines, exhaust, etc all fabbed again). They also seem to be easier to work on although I suppose that's a matter for debate. The thing that I keep looking at though is the 5-6MPG of the truck. I put anywhere from 3k-6k worth of fuel through it a year. Even a 25% improvement in fuel economy is going to mean big bucks down the road.

I know physics is physics, but plenty of others have bigger, heavier things that are getting better mpg.

 

[coachgeo]

Think you will need an RPM signal for the computer on the tranny... the 3116 had a sensor that reads off on the crank?

 

[aleigh]

The Allison would need a few things, probably most notably throttle position. That's what the little box is that takes-off from the throttle on the driver side. The existing sensor is divorced though, and Allisons on cummins is a common application.

 

[snowtrac nome]

you can also get an rpm signal for the cummins to. I work on both engines and also deere on occasions, I don't see much difference in the price of parts in any of them. The aftermarket support for parts is drying up because of deals like cat has, where they no longer allow the company's they are outsourcing parts manufacturing to, allowing them to sell under said company's name to. The 6 b does have a lot of aftermarket support just because of its popularity and there are a gazillion of them out there. Unless you go with a modern efi motor I wouldn't expect a big change in fuel millage between a cat 3116 and c series cummins if any at all. When it works bosch common rail is down right impressive. and is even better if you can get away from vgt turbos and emissions,but when it brakes you think yellow motors are expensive,you aint seen nothing.

 

[coachgeo]

The Allison would need a few things, probably most notably throttle position. That's what the little box is that takes-off from the throttle on the driver side. The existing sensor is divorced though, and Allisons on cummins is a common application.

doooh.... forgot about that one. sounds like options are there. Am getting excited for you now lol

 

[aleigh]

TBH I worry more about parts availability than cost. Like when I had these problems, I needed a new water pump cover, which is just a part in the normal water pump assembly that is normally sold as a complete unit. One was sitting on the shelf at cat in Seattle, for $40. I don't really care if it's $20, $40, or $60 I just care that I can get a part when I need it because more likely than not I am stranded somewhere if it's a problem.

This probably deserves its own thread but really why are the school bus guys getting 10+mpg on these motors?

 

[mkcoen]

This probably deserves its own thread but really why are the school bus guys getting 10+mpg on these motors?

Gearing and full time four wheel drive cuts the LMTV mileage considerably.

 

[aleigh]

Some data. Checkout that fan...

 

[Aernan]

I'm currently getting over 8 Mpg out of my truck but it's unloaded. Rumor has it you can get 10 out of the truck with tuning, tires, high speed gears. From what I am reading methanol/water injection could help some maybe 2 mpg and there might be a newer more efficient turbo available. It would certainly be possible to get a VNT turbo as well.

Another critical thing to consider is there may be significant losses in the transmission, transfer case, drive shaft, differential, hub gears that an engine swap won't fix.

 

[Aernan]

so it looks like modern diesel engines get some 45% efficiency.

https://en.wikipedia.org/wiki/Engine_efficiency
[h=3]Diesel engines[edit][/h]Engines using the Diesel cycle are usually more efficient, although the Diesel cycle itself is less efficient at equal compression ratios. Since diesel engines use much higher compression ratios (the heat of compression is used to ignite the slow-burning diesel fuel), that higher ratio more to air pumping losses within the engine.
Modern turbo-diesel engines use electronically controlled common-rail fuel injection to increase efficiency. With the help of geometrically variable turbo-charging system this also increases the engines' torque at low engine speeds (1200-1800 RPM). Low speed diesel engine like the MAN S80ME-C7 have achieved an overall energy conversion efficiency of 54.4%, which is the highest conversion of fuel into power by any single-cycle internal or external combustion engine.[SUP][3][/SUP][SUP][4][/SUP][SUP][5][/SUP] Engines in large diesel trucks, buses, and newer diesel cars can achieve peak efficiencies around 45%.[SUP][6][/SUP]

 

[Awesomeness]

Even a 25% improvement in fuel economy is going to mean big bucks down the road.

I know physics is physics, but plenty of others have bigger, heavier things that are getting better mpg.

You won't get 25% improvement from any engine change (only). 5% is more likely, with 10% being a stretch goal. The engine isn't really the problem (largest contributor of waste), so changing it doesn't make a lot of difference.

The "heavier things getting better MPG" are significantly different. They are more aerodynamic, lower to the ground or have ground effect spoilers installed, aren't full time AWD, are using narrower / harder tires to reduce rolling resistance, etc. The weight is not nearly as important as it seems, except when accelerating... keeping the truck moving at a certain speed is only fighting wind resistance / drag and drivetrain friction (the weight is irrelevant).

It would be interesting to see what changes to the truck would be necessary to get 25%.

 

[Awesomeness]

so it looks like modern diesel engines get some 45% efficiency.
https://en.wikipedia.org/wiki/Engine_efficiency

This is true, but "non-modern" diesel engines aren't way worse. (What does "modern" mean, as even the 3116 is attempting to do some of the "modern" things they are describing in cruder, more mechanical ways.) Our engines are probably only 5-15% worse, so you're just gaining a little bit, and that little bit is only addressing one of several major contributors of the fuel economy.

 

[Awesomeness]

Some data. Checkout that fan...

View attachment 718037View attachment 718038

Where are those pictures from?

I wonder what the parasitic energy to drive the fan is, when it is turned "off"?

 

[Rebuilder]

The SD Brazo's came with the 6.7 Cummins and Allison trans so that option would definitely work. Is the 8.3 a completely different engine or is it dimensionally close to the 6.7?

 

[aleigh]

Where are those pictures from?
I wonder what the parasitic energy to drive the fan is, when it is turned "off"?

"A strategic investigation for fuel economy improvement of medium-duty tactical truck: preliminary simulation and experimental results".
Y. Gene Liao, Allen M. Quail Jr