LDS VS LDT and the real differences

[Capt.Marion]

Whoah, Flyingvan, can you change your text color in your post to something light-colored? The grey doesn't show up hardly at all on the default green background. In the meantime I can highlight the text to read it, but for other folks...










Dark text color fixed!

G.

 

[Flyingvan911]

Sorry. I'll have to find out how to do that.

 

[Flyingvan911]

Got it. Sorry about that.

 

[Heath_h49008]

Modern lube will do wonders all by itself, but not driving them overloaded and with your foot to the floor while you get shot at should have a nice side effect as well. (Never forget how much of a target those kids were, or how many never made it home.)

We have a number of these threads again on LDT/LDS hotrodding. I'm going to chalk it up to cabin fever.

 

[Nasty610]

I know I'm resurrecting an oldish thread but I've been doing a lot of reading about tuning a diesel engine. It's been mentioned several times in this thread that the engines are have no differences aside from the IP fuel delivery rate and pump timing. These two things alone will account for the additional power the LDS has over the LDT.

By altering the fuel delivery rate you can completely alter the power curve of the engine. By setting the pumps defuel point higher this allows the engine to rev to a higher redline. With the increased redline there is additional power potential this is not only due to the increase in RPM but the fact the pump is giving full fuel to a higher RPM. Increasing the defuel point is a very common mod to all diesel engines most noteably the Cummins B series and is accomplished by swapping govenor springs. While the small RPM increase will not provide for an additional 40 hp it will account for a portion of that power.

The other major difference noted was IP timing being retarded on the LDS engine. This is actually fairly significant because by retarding the pump time you are lowering cylinder pressure prior to combustion. With the lowered cylinder pressure you will have less heat build up. Because there is less heat build up in the cylinder there is actually more cool air to help keep the motor cool with the additional fuel the pump is injecting.

I know a lot of you advance your pump timing and feel you have gained power. What you've really gained is response but at the expense of additional pressure/heat in the cylinder. If you don't believe try retarding your pump timing and then increase your fuel. Your engine won't feel as peppy but you'll be able to run a lot more fuel which will result in more power. Because you'll have more power the drop in response won't be as noticable. I would be willing to bet with a little experimenting you could safely turn a stock LDT or LDS up to 250 hp.

 

[TehTDK]

Sorry for the slight OT:

But let me get this straight.... so the 465-2 Engine is NOT used in the M35's at all?, and is only available in the 5-tons. And you will only get it with the M35 if you buy it second hand from a 5-ton and then implant it into the M35. Is that correct?.

 

[Nasty610]

It has been posted a couple time that the LDS465-2 was used in a Ford manufactured 8x8 not just a regular 5 ton. The parts should be interchangeable though so you could build a -2 out of a -1 or LDT.

 

[Ford Mechanic]

By altering the fuel delivery rate you can completely alter the power curve of the engine. By setting the pumps defuel point higher this allows the engine to rev to a higher redline. With the increased redline there is additional power potential this is not only due to the increase in RPM but the fact the pump is giving full fuel to a higher RPM. Increasing the defuel point is a very common mod to all diesel engines most noteably the Cummins B series and is accomplished by swapping govenor springs. While the small RPM increase will not provide for an additional 40 hp it will account for a portion of that power.

.

These arn't a Cummins. The notion that I have found after much reading on this site is that the Multi's can't handle running at their governed limit for long, much less a higher one. The big difference between the Multi's and other diesil's are that a conventional diesil has a compression ratio of 16:1 to 18:1 the Multi has a 22:1. Needless to say the govener is one thing I won't be touching on mine, with the gas pedal or a screw driver.

 

[m-35tom]

actually the govenor IS something you should be adjusting. DOWN!! under the cover on the rear of the IP is the high idle screw, i set mine to run at 2550 rpm full throttle in neutral. i expect to have this engine for another 30 years.

 

[Ford Mechanic]

actually the govenor IS something you should be adjusting. DOWN!! under the cover on the rear of the IP is the high idle screw, i set mine to run at 2550 rpm full throttle in neutral. i expect to have this engine for another 30 years.

+1 ! I don't plan on hitting anything over 2300 in mine, but I'll use my foot to "govern" it rather than spin it that fast to reset it.

 

[Nasty610]

I think I worded my statement incorrectly and I am sorry for the confusion. I'm not suggesting we increase the max RPM just the point at which the IP starts to defuel. If the IP keeps fueling closer to the governed RPM there is more power potential. This isn't a mod for just Cummins either it works well on Detroit 2 & 4 strokes, Cats, Yanmars and every other compression ignition engine in the world. All IP work the same the Multi's isn't special. Has anyone tried retarding the timing to see if there is a decrease in EGT's? Preferably I'd like to hear from someone with a LDT that has turned their pump up as far as they can without changing timing, then retard timing to LDS specs and record the difference.

 

[m16ty]

It has been posted a couple time that the LDS465-2 was used in a Ford manufactured 8x8 not just a regular 5 ton. The parts should be interchangeable though so you could build a -2 out of a -1 or LDT.

They are found in some M35a2s coming right from the government. Now I don't think any deuces came from the factory with a LDS-465 but some have been repowered with them by the military. I've seen a few come through GL.

 

[Nasty610]

Are you sure? I was under the impression the LDS-465-1 was found in the some Deuces not the LDS-465-2. The -2 motor is supposed to be extremely rare with a much higher HP/RPM rating.

 

[m16ty]

I think I worded my statement incorrectly and I am sorry for the confusion. I'm not suggesting we increase the max RPM just the point at which the IP starts to defuel. If the IP keeps fueling closer to the governed RPM there is more power potential. This isn't a mod for just Cummins either it works well on Detroit 2 & 4 strokes, Cats, Yanmars and every other compression ignition engine in the world. All IP work the same the Multi's isn't special. Has anyone tried retarding the timing to see if there is a decrease in EGT's? Preferably I'd like to hear from someone with a LDT that has turned their pump up as far as they can without changing timing, then retard timing to LDS specs and record the difference.

I'm not real sure that what you're saying will work. You cannot turn up the point that the IP defuels without increasing max rpm. The pump defueling is what determines max rpm. The only factor that controls max rpm is the IP fuel rate which is controlled by the governor. In other words, the governor has no control over the rpm independent of the IP fuel rate.

 

[m16ty]

Are you sure? I was under the impression the LDS-465-1 was found in the some Deuces not the LDS-465-2. The -2 motor is supposed to be extremely rare with a much higher HP/RPM rating.

You may be right about the -2. I still wouldn't be surprised if a deuce came from the military with a LDS-456-2 but as you said, it would probably be rare.

 

[Nasty610]

You would have to have a shop rebuild your IP to set the fuel rate the way I'm talking about. It's done a lot on OTR trucks. The major issue you'd have is finding a shop that would be able work on this pump.

Don't give me credit for know which engine is in which truck. I pulled that information from this forum. There are several guys that live, eat and breath OD. I'm not one of them quite yet.

 

[akt12]

"The LDS starter is on the left. My LD is on the right, very close to the exhaust pipe. Perhaps the move was to get it away from the heat. "


Can I get recommendations on building a starter heat shield? I just bolted on a turbo to my N/A.

 

[Heath_h49008]

The best difference I have found... and it is significant.

TM 9-2910-226-34 lists the output specs for the injection pump during test-stand certification.

At 2800 rpm the LDS-465-2 (A code pump) flows between 47-50cc at 2800rpm and the governor cuts fuel to below 5cc at 3150rpm.

The LDS-465-1 and LDS-465-1A (B and F code pumps) flow between 42-45cc at 2600 RPM and below 5cc at 2940RPM.

The LD-465-1, LDT-465-1, LD-465-1C and LDS-427-2 (Code C, D and G pumps) are rated to flow between 34-38 at 2600RPM and less than 5cc at 2940RPM.

This is done with various governor springs, and Hydraulic Heads. One big head, one high rpm gov. LDS-465-2 has the high gov and the big head. LDS-465-1 &1A have big head low rpm gov, and LD/LDT-427/465-"any" have the small head and the low rpm gov.

Basically, the pump assembly/governor has your RPM limits, and the HH has the fuel volume limiting factors. (power limits at normal pressure) If you want that 50cc for 500 strokes that the LDS-465-2 used to get it's high rating, you need that HH, or to crank your smoke screw and increase the pressure/wear on your little head. If you want more RPMs, you can either play with the Governor springs in yours, or get the LDS lower pump that already has them.

The pistons, injectors, turbos and all the other factors we have gone through here are marginal changes used to keep the engine alive with the "extra" fuel.

So, if you all want LDS power, the next HH group buy might want to call China and see if that slave labor camp builds them in the same pattern as PN HD90101A (LDS) instead of HD90100A (LDT) I doubt any of you really want the governor springs to hit 3000rpm...

 

[m-35tom]

i fail to see how there is ANY increase in pressure or wear by turning up the fuel. all you are doing is raising the position of the fuel dump bar. you are not increasing the pressure just the duration and only by extremely marginal amount. a LDT can easily be turned up more than it can handle. 0.024 cc per stroke increase? well within the capabilities of a ldt pump.

also the oil cooling in the head of a LDS piston is probably not marginal or they would not have done it. the LDT does not have it, just washed with oil.

 

[Heath_h49008]

If the increase in the load on the smaller head was so inconsequential, why go through the expense of the larger one? I suppose changing the smoke cam angle to the LDS 100deg from the factory LDT 75deg would be the other side of that coin.

I'm certain you are correct, and the increase is marginal in all respects. As for the oil passage in the pistons, I believe the internal memo that was linked way back said it offered a 100deg F decrease. While with 1950s lubes that were operating at the limits that might have been worth the effort, but modern oil would seem to minimize that advantage.

My point was, the difference is all in the pumps and the hydraulic heads if the question is "Where does the extra power come from." Also, if all things are equal, buying the HD90101A as opposed to the HD90100A would seem to make sense if increased output was the goal.

EDIT: In case my point was missed by my roudabout way of saying it... just crank the fuel and get a pyro.