I was talking to an old diesel mechanic. He said you could replace the "tips" on the injectors to ge a hotter burn and more power. Anyone heard of this for an upgrade
Wayne

Don't f__k with the injectors. Change the entire unitized part.

Agree.

If you are keeping the 542 transmission, get a set of 230hp injectors and a #11 fuel plate.

IIRC, when I visited Vince (the PO), the documentation showed the engine had been bumped to 215 HP.

Rusty: The paperwork Vince gave me said cummins installed 210 hp injectors. I'm going to go back to 8R tires as at 2400 now I'm only going 55 mph. I can get to about 65 at 2700 but I don't think It is wise to run on the governor.
Gary: I have found a mechanic that will install a allison 2000 5 spd if I can get the programing part. If I do that I don't have to worry about the trans. Did you change injectors on your?
Thanks for all your comments
Wayne

If a person wanted to upgrade their '91 Breakaway to a 5-speed transmission, which of the Allison transmissions would you use? Let's assume that the engine is no more than 230HP. Would the engine RPMs drop enough to make a noticeable diff in fuel economy? Would it be more sensible to just drive at 55mph?
Jim

Do a search for transmission upgrade in this forum. Most of the information needed is there.

If buying a 1000/2000 series transmission make sure you get the wiring harness. And yes the 1000 will work.

And you can not justify this conversion based on money or mpg. But I would never go back to a 542. The best part of the conversion was the lockup convertor. My 542 used to overheat in the mountains and I would have to stop and let it cool down. Oh and I like traveling 70mph out on the freeways, but I don't let it go into 5th until about 60+ (rpms to low).

The one thing I didn't talk about in transmission upgrade was the overdrive switch on the dash. Keeps it in 4th gear.

BTW I have an extra TCM if needed. Been going to put it back on ebay but a little slow.

Thanks for the link. Sounds like upgrading to a 6-speed is rather expensive. Better to buy one that already has it installed. In the meantime, with my 5.9 that has been bumped up to 190 HP, it appears that a good cruising range is around 1800RPM. What would the speed be at that level. Tires are 8R19.5. I'm guessing around 55mph.

With the 542 and 3.73 final, 1800rpm gives you 47mph. Need 2100rpm to do 55mph.

Would you think that 2100 RPM is a safe/efficient motor speed? Fuel economy is not my concern. I like the engine to be comfortable.
Jim

I think the operating range is 1800-2400. If that is incorrect PLEASE let me know

Oh btw Gary I have turner classic movies on my cable, or was that something else I don't know about.
As far as price it looks like about 1/2 of what you paid for the coach should cover it.
Wayne

When I am running 75 MPH I am running 2150 RPM with the 225 tires. Smooth and getting about 10 MPG. I only do this in the flat lands sometimes. Now I try to stay 70 MPH or less but still get about the same MPG. I can only get better MPG if I go 60 MPH and no wind, then I get about 11.4-11.8 MPG.

Problem is I can go that slow, it just seems to be the best about 70 MPH @ 2000 RPM.

Changing to a 6 speed would be a LOT of WORK! Further, for those of you that have a 4 speed your rear diff is 3.73 and that would have to be changed to 4.1 or numerically higher to take advantage of all of the ranges of the 6 speed.

So, the engine 'likes' 2100RPM