Best mods for my Motorhome?

[finn188]

I bought a 1992 35' motorhome with an IC Cummins and 4 speed Allison trans. It is a pusher (engine in rear). It only has 20K miles and runs great but just low on power. My goal is:
-to be able to tow my 93 Grand Cherokee on a stout 2 axle trailer (Im not sure on total weight)
-keeping the EGTs as low as possible.
-Low budget

I have been on the site for several hours and have found some good info but nothing specific to a 1st gen motorhome/ tow rig.
So after reading a bit here is my plan:

1- Pyrometer/Boost/Fuel pressure gauges
2-366 spring
3- tweak the pump

if thats not enough:

4-DDP injectors...300s?

if still not enough:

5-12 or 14 mm housing?
6- water injection

This is my first diesel. Is there any way to increase the boost at the turbo waste gate? Thanks and any input on my plan of attack is much appreciated.

[peobryant]

If it is a '92 Cummins it will have an H1C turbo, which has no wastegate.

If you want to keep the EGT's low, I wouldn't suggest tweaking the pump. A set of injectors will give it a nice boost in power (DDP and New Era have very good reputations) and still be manageable in the EGT department.

You may also want to add a tranny temp gauge to your list. Don't want to cook that Ally.

[finn188]

If it is a '92 Cummins it will have an H1C turbo, which has no wastegate.

If you want to keep the EGT's low, I wouldn't suggest tweaking the pump. A set of injectors will give it a nice boost in power (DDP and New Era have very good reputations) and still be manageable in the EGT department.

You may also want to add a tranny temp gauge to your list. Don't want to cook that Ally.

New plan:
1- guages
2- 366 spring
3- DDP or New Era injectors


Any idea on the numbers I could expect with these mods? Would fuel mileage suffer much? anything else I should do?

[sdstriper]

Was this a swapped in engine or is it factory? Can you get to the engine identification tag on the gearcase? If so, check the rated HP, same with the turbo, there is a tag on the turbo, ID the turbo and engine then report back.

Just because it is a 92' doesn't automatically mean it is built exactly the same as the Dodge CTD's. Unless it was a swapped in engine from a Dodge p/u...

[peobryant]

Was this a swapped in engine or is it factory? Can you get to the engine identification tag on the gearcase? If so, check the rated HP, same with the turbo, there is a tag on the turbo, ID the turbo and engine then report back.

Just because it is a 92' doesn't automatically mean it is built exactly the same as the Dodge CTD's. Unless it was a swapped in engine from a Dodge p/u...

That's exactly what I was thinking. We can't give much advice, if we aren't sure what the engine is.

[burnt_servo]

i'm wondering how much higher the stall speed of the allison converter is going to be after the engine mods ???

and it it's much higher than the engine being stock , maybe a low / lower stall converter being added to the list , much like when a guy hops up a auto dodge cummins .

[finn188]

It is a factory setup, no mods. With the model year being 1992 and having an inter cooler I was guessing it would have the same engine as the 1992.5 pickup. I will get the ID numbers today to confirm engine/ turbo. BTW I believe the owners manual claims 160? hp and 300 ft/lbs

[Richie O]

I would not give it much power. Being that heavy you are going to be on the throttle all the time. If you can get the power you want and keep EGT's managable it still is hard on the whole drivetrain. I would keep it reliable and slow. I would not go above 225 horses. Its much better to be slow and go forever then to go fast then be broke down beside the road.

[MrHorsepower]

I have a '92 Gulfstream and it is rated at 190hp, intercooled. I will go look at the numbers it has on it tonight.

[finn188]

Im not sure where to get the numbers. I looked through the manual and all I found was:

Cummins 6B5.9 190hp, intercooled. the Allison is an AT 542.

[finn188]

I have a '92 Gulfstream and it is rated at 190hp, intercooled. I will go look at the numbers it has on it tonight.

thanks

[PToombs]

The numbers are in the edge of the timing cover. Climb in thru the wheel well and you can see 'em.
Friend of mine has a MH with a factory cummins. He says it runs HOT! He did a turbo upgrade, and is in the process of putting in an I/C.
Before you get all excited and turning things up, run with guages so you can see where it's at. You might need a bigger I/C or something before injectors.

[sdstriper]

You for sure want gauges, EGT and transmission for sure. That's a four speed without OD, correct? Get the gauges and turn up the pump some. Whats the intake like on that thing? How big of an exhaust is on it and how much clearance is there to go with a larger exhaust?

[finn188]

The numbers are in the edge of the timing cover. Climb in thru the wheel well and you can see 'em.
Friend of mine has a MH with a factory cummins. He says it runs HOT! He did a turbo upgrade, and is in the process of putting in an I/C.
Before you get all excited and turning things up, run with guages so you can see where it's at. You might need a bigger I/C or something before injectors.

Do you have a link to a good write up on gauge installation for the pyro, boost, and trans? Yes the trans is the non OD 4 speed. If I do find out if its running hot is water injection an option? I have a large water source anyways and could have it set up to run when pulling hills or whenever temps climb too high.... I think you are right about getting a baseline on what my current temps are.

[finn188]

You for sure want gauges, EGT and transmission for sure. That's a four speed without OD, correct? Get the gauges and turn up the pump some. Whats the intake like on that thing? How big of an exhaust is on it and how much clearance is there to go with a larger exhaust?

Current exhaust looks like 3.5" with a huge muffler. Intake aprox. 5"? Yes there is lots of room for bigger exhaust.