Performance and fuel mileage need advice

[Bigfury]

Finishing up installing a 1990 6bt coupled to Allison 545 tranny in '77 26' Champion RV. It's a 160 hp water to air intercooler with about 170,000 miles. Will also be putting a 3.07 rear diff in. Will like to try to get 200 horses and 20 mpg, traveling 55 to 60 down the highway. As far as I can tell the engine never been tempered with. Will be installing gauges, pyrometer, boost. Is exhaust pressure needed to efficiency out of a turbo? Thanks in advance for any advice.

[Philip]

The less back pressure the better.

Questions?
What is the rolling weight on that MH?
Original gearing in the rear axle?
Why a nonOD 545?

[oldestof11]

The 3.07's should help the NonOD. He will have more forward gears though.

200hp is just minor pump adjustments away.

20mpg, IMHO, is not going to happen with that giant brick of an RV.

[Bigfury]

The RV gross weight is 12,000. Cummins along with the allison was removed together from a Blue Bird passenger bus. Was not aware of a OD 545. Orginal drive train was a 440 with a 727 and 4.56 rear. Also adding 19.5 rims. Would like to think moving this brick down the highway at 55 to 60 that 2o mpg might not be so far off.

[Philip]

Use a trans with OD and the 4:56's would work fine. It would save you time and money trying to find a 3:07 axle. The MH's had a wider axle than the dually's had. So your tires would tucked in farther. You will not put a set of 3:07 gears into your current housing.

With a GVW of 12K. That's not pushing the engine hard. The bus it came out of weighted more. 545's were never made with OD's.


MIDon a member on this site dropped a 6BT with a 518 from a 92 into a Travico. He was getting 16 MPG out of it.

https://www.youtube.com/watch?v=Vo11DG1nuGk

[Bigfury]

Already got a 3.07 ready to install. Really wish the Allison had a lock-up convertor (as they say wish in one hand and ___ in the other). Do have a S300G, I believe, that can be installed or a HE351VE. Do not believe the exhaust brake will do any good for slowing down. Would like to think with a few up grades and some good VE pump tuning 20 mpg may not be that much of a dream. Only needing to move this thing about 55 to 60 down the road, if that is where it's SWEET SPOT can be tuned in at????

[jethro]

BF-
Somewhere I was using an on-line calculator which you input all your ratios and your wheel diameter and desired engine rpm-
Fixed so you can vary any one of those so you can run your engine at its most efficient rpm range while hitting you target road speed.
If you need that page I think I have it favorited somewhere. Seems like I heard someone say that the "sweet spot" for the 6bt
is around 1800 RPM.
I am also shooting for good MPG. Not quite on the road yet. (overhauling my rear end)
I have 93 6bt,ford intercooler with stock 6bt turbo- 6 speed Ford ZF-6 manual (2 range with 4x4) in a 2004 leaf spring F-350 -
currently have 35 inch wide mud tires. May go to 18 inch wheels and a narrower tire.
Hope to get 20 + mpg My pump has been turned up about 20% (supposedly) Seems to have plenty of power driving around
the yard. I can really feel the turbo pepping things up when it gets above about 1000 rpm. It has the 18 cm H1C so I was
expecting a delayed response. It has enough power I may consider turning it down just a hare - but I wont decide till later when I can
test MPG on the road.

I just saw a device on youtube which you add that allows you to adjust your fueling electrically via 2 potentiometers in the cab while you
are going down the road. Says it works on first gen too !
www.powerdrivendiesel.com called the in cab fueling adjuster-
maybe someone here can tell us if it has been tried and how good it worked-

tim

[matthewh]

Www.grimmjeeper.com is a site that has the gear calculator that Jethro talks about. It has 2 columns, so you can compare different options side by side. Also has a nice list of transmissions and tcase's already there so you don't have to input your numbers.

[PToombs]

I just saw a device on youtube which you add that allows you to adjust your fueling electrically via 2 potentiometers in the cab while you
are going down the road. Says it works on first gen too !
http://www.powerdrivendiesel.com called the in cab fueling adjuster-
maybe someone here can tell us if it has been tried and how good it worked-

tim

After seeing the video on that "AFC Live" thing, all it is is a needle valve and a relief/ limiter valve in a box. Your boost line runs in, the needle valve controls how fast the boost pressure goes out to the AFC and the other screw limits how much pressure it gets which controls AFC travel. It did say they have a spring for the AFC which matches the boost rate supplied by the box. No voodoo there, just a nice gimmick to control how fast the AFC works.
I did read where it only made a 30 hp difference on a 1st gen, I think that's under rated, but who knows what the mods were on it.
$250 is a lot of money for a box with a couple valves in it.

[Bigfury]

It looks like I have all winter to do some tuning. There is a air to water intercooler atop the intake. Will a air to air help? The M&H Dynamic Timing spacers are waiting on production. At the same time plan on purchasing a M3 fuel pin. Not sure what to plan on after these up grades. There will be gauges added to the dash. Thanks for all the information so far.