IDI's in Medium Duty Apps

[ameristar1]

I know most of the time when an IDI is used in 26000# or under gvwr, they are geared really low. For something in this weight class that needs to cruise comfortably at 65-75mph, would going to a taller gear, to make it more highway friendly, put more strain on the engine. Like if you gear what amounts to a barn to run at 1800 rpms at 70 mph, would that be too much?

 

[jperecko]

I think that the driver would quickly start to hate life if you are really going up to around 26k pounds. You would have to downshift at the all the hills and not really be able to keep speed up. It might work for just going down a flat road but I cannot imagine it being fun otherwise.

I have driven a 26k 26ft box truck powered by a powerstroke and even only at ~16k pounds I could not keep speed on the grades.

There are 2 issues... the obvious one is the weight you are dragging up the hill but there is also the fact that you are pushing that barn through the wind at 55-70 MPH.

 

[85ford]

Yes aerodynamics becomes more and more obvious the bigger the thing you are towing is. So it's just not the weight it's the wind resistance of the object.

 

[ameristar1]

Thanks for the input. I'm just throwing ideas around for an expediter style truck and testbed for IDI stuff. Something like that would work the engine really well.

I know most of the time the PSDs in the medium duties are set at 175 hp, and hopefully I'll have a little bit more than that.

That, and 10-13 speeds to play with.

 

[sassyrel]

Thanks for the input. I'm just throwing ideas around for an expediter style truck and testbed for IDI stuff. Something like that would work the engine really well.

I know most of the time the PSDs in the medium duties are set at 175 hp, and hopefully I'll have a little bit more than that.

That, and 10-13 speeds to play with.

me thinks a 15 spd would be even better--to keep the r's in the sweet spot---

 

[ameristar1]

me thinks a 15 spd would be even better--to keep the r's in the sweet spot---

You must have known about my old W900. Deep reduction 15 speed with 3.90s on 24s. No speed, but great in the mountains.

 

[Goofyexponent]

I got yas ALL beat in the lack of power department! 1996 International 4900 tandem dump truck...60 627 pounds when loaded. Powered by a mechanical DT466 with a 190 horsepower tune backed up by an 8 speed direct road ranger and 4.63's in the rears. That thing could smell a hill coming!

 

[ameristar1]

I got yas ALL beat in the lack of power department! 1996 International 4900 tandem dump truck...60 627 pounds when loaded. Powered by a mechanical DT466 with a 190 horsepower tune backed up by an 8 speed direct road ranger and 4.63's in the rears. That thing could smell a hill coming!

I knew that was you Goofy! Man, is that right? Grossing almost 61k? 190hp?
Who the hell specced out that truck?

 

[Agnem]

The last IDI of that class that I ran was a U-haul IH S1600 with a Clarke 5 speed in it. Yes, all the gears were low, but of course 5th gear was 1:1. The rear axle is where the really low gear lives. It could run the highway at 55MPH just fine, but didn't like going much faster. I don't think it would matter how many gears you have, since your not going to be able to turn the R's to keep your speed up in a rig like that. The best you could hope for is a 2 speed rear probably.

 

[ghunt]

At my work we have a '97 F-800 flatbed (rated for 26K GVW), the truck itself weighs I think 13-14K? Can't remember. It's powered by a 12V cummins, which according to the nameplate is a 160 hp/400 ft-lb model (which is weird, because it has an HX35W and it's intercooled). It's backed by a four-speed allison.

The first three gears seem to be pretty low, empty the truck will actually get up and go pretty well, although third gear is all you ever get to on hills because it bogs down on hills pretty bad. On the highway, in 4th gear it does 70 mph @ 2500 RPM's, so I'm guessing 4th is 1:1 and it has low gears in the axle. The truck will haul 12K but I wouldn't want to drive it hauling that much. It can barely get out of its own way just hauling 5000 lb which it does on a regular basis. I'd like to put a 200 hp fuel plate in it, but... *shrugs*

Anyway, I'd imagine an IDI would be even less happy in that truck since at the same HP level it would probably have less than 400 ft-lbs. I rode in an old IDI-powered International 26' Uhaul several years ago, with a 5 speed, and it was the slowest vehicle I've ever ridden in. It was down to I think 2nd gear and 25 mph on most of the hills we went over.

 

[RLDSL]

Put 5.13 in the tail end and either a 5 and a brownie in or a 10 speed or 13 and you would pull that kind of weight just fine, just don't plan on going much over 55, but in all reality, you don't need to be going any faster than that with a load like that anyway

 

[ameristar1]

It sounds almost painful in this day and age. Oh, well. When I was on the road, I liked to drive at night, and at 11:00PM it was "start your engines". The bull haulers and the ****** trucks are on the run. I would be in the slow lane doing 58-63mph just to stretch the tanks out, and these guys fly past at 80 or better. Have this happen enough times and you start to assess the options.

I think I'll leave my testing to the dyno and a pickup truck. Having an IDI in a big truck sounds like vehicular suicide.

 

[Goofyexponent]

I knew that was you Goofy! Man, is that right? Grossing almost 61k? 190hp?
Who the hell specced out that truck?

Oh ya! She SUCKED on the hills, turned 2600RPM at 62 miles per hour. It was weird. Half of the front radiator was intercooler, and half was radiator....but the pig never overheated. I have hauled 28000 kgs gross with it...it wasn't fun but it did it....somehow.

It had a cummins P-pump style IP in it, and it was apparently SUPER wasy to turn up...I never got the chance to try it though, the guy disappeared with my last pay

 

[Alex S]

you have to remember the medium duty trucks that got the IDI was in the 80s and before that they had the big V8 gas engines (392) and some of the MV series. So when the gas crunch happed, economy was no1 and then now just recently in the 90s it was back to making power and they had the technology to throw at the engines as well

 

[1320Cummins]

I have such a beast. She runs OK. I have had the truck scaled at 34,000 and about 42,000 gross combined with a small tanden trailer and tractor.
The truck has a six somethin rear in it so top speed is 65mph @ like 3400rpm.
I want to put taller gears in it but I am afraid to kill my low end especially when backing into soft yards.
We used to have a 92 IDI class 8 full size school bus and she would top out @62mph. Even with pump turned up she would loose 3-5mph just crossing over passes. I will never own another IDI in a mid range or heavy truck/bus unless it is a steal of a deal.