LDS VS LDT and the real differences

[deathrowdave]

An internal - combustion engine is nothing more that a large air pump (compressor) to move more air you must increase intake air by turbo / blower or cam timing . Could the cam timing gears be diferent from one to another. The LDS could have advanced cam timing over the LDT.

 

[gringeltaube]

............. Could the cam timing gears be diferent from one to another. The LDS could have advanced cam timing over the LDT.

No way.
From the books: part numbers for crank, cam and timing gears....

2815-177-9209 GEAR, CAMSHAFT TIMER: 10889822
3020-311-5332 GEAR, HELICAL: CRANKSHAFT 10889820
2815-808-6989 CRANKSHAFT, ENGINE: 11610173
2815-808-6978 CAMSHAFT,ENGINE: 11610283


ALL model engines including the LDS427 share these same parts and obviously cam timing is exactly the same for ALL!

G.

 

[mudguppy]

alright, so tell me if this is what we are saying:





the only difference between the LDS and LDT motors are -

• injectors
• injection pump settings
• pistons (only for ring count purposes)

otherwise, essentially everything else that may make a difference is the same -

• turbo (swappable and proved to not account for the difference)
• bore
• stroke
• cam
• timing
• compression ratio
• head flow (assumed?)

=================================================

so is the above an accurate summary of what the thread is stating?

 

[doghead]

nope

 

[mudguppy]

thanks - that helps.

 

[doghead]

If you hadn't noticed, I don't care to debate the differences. I only brought this back up because the OP dropped it. He was gonna answer the question of what is different(not me).

nope was actually an "long" answer, I had to post 3 or more letters!

 

[mudguppy]

well, i am interested in what the differences are.

my question was not directed to you. and if you never intended to answer the 'what is different' question, why did you feel like you needed to answer it anyway?

 

[doghead]

To keep the thead correct.

That's what moderators do to keep the site useful.

 

[mudguppy]

don't worry - we all know you are a mod.

thanks for keeping the thread correct and adding value.

 

[Kohburn]

reading back it seems to have been established that the differences that haven't been tested (others were tested to make no difference) are:

-lower compression (= higher volume of air from turbo accepted without increasing exhaust temps)
-different rocker arms (a higher ratio would = more valve clearance = more air)

 

[mudguppy]

reading back it seems to have been established that the differences that haven't been tested (others were tested to make no difference) are:

-lower compression (= higher volume of air from turbo accepted without increasing exhaust temps)
-different rocker arms (a higher ratio would = more valve clearance = more air)

good point on the CR - i was trying to recall (without going back through all 90 posts) whether the rotating assembly was the same.

if the crank and rods are the same part #'s and the piston pin heights are the same between the two motors, then CR should be the same unless there are differences in the head chambers.

however, i don't see a CR change being responsible for adding 50-70+ horsepower over the LDT.


my opinion based on what i've learned: diesels make power based on fuel. and you can alter fuel delivery to make more power without changing any other aspect, including air. fuel delivery pressure, fuel delivery velocity, injector orifice count and size, spray pattern, combustion bowl design, and other things can be altered and have affect on power without increasing EGT or putting combustion pressures above safe levels.

that's my theory without know much about anything.

 

[gringeltaube]

reading back it seems to have been established that the differences that haven't been tested (others were tested to make no difference) are:

-lower compression (= higher volume of air from turbo accepted without increasing exhaust temps)
-different rocker arms (a higher ratio would = more valve clearance = more air)

You seem to have nailed it.......!

Again from the books: ALL model engines use the same part#10899107 rocker arm for the exhaust valves. Code C,D, E and G engines (LDTs, LDs and LDS 427 resp.) also have these for the intake valves, BUT.....
Code A, B and F engines (the 5ton Multifuel's) show a different part #11641735 for their intake rocker arms.
It sure would make sense if they were of a higher ratio, in fact!!
Anyone having some laying around? I want 6 now......

G.

 

[fcdrifter13]

another thing to look at is the dynamic compression ratio. Even if both motors are the same and cam timing or lobes are slightly different this can change the actual compression quite a bit. I had an old IDI f250 and one of the best things to do was to put in a slightly different cam the difference was night and day. Another thing is the injection pump, I tried looking through the FSM but I couldn't find any thing that stated what the output pressure of the pump or what its timing is because pump timing can be different inside the pump even if the timing gear is installed in the same position. To me it makes sense that the 2 hole injectors were replaced with one hole, this is a better spray pattern onto the top of the cylinder which would cause a better burn. It would be very very interesting to see what a set of newer designed injectors would do to lower EGTs and bump power. Something with a higher pop pressure at the same amount of fuel is going to make more power.

Did anyone ever take there injectors to a diesel shop to see what the rated pop is or if they can be shimmed up to increase of polished out. Is there a technical document for the injection pump itself all i have is a spec sheet that is hard to read and a limited repair manual that is basically replacing the pump.

EDIT: while I like this site found the pump diagrams I was looking for. Time to read.

 

[SCSG-G4]

The compression ratio as specified is the same (22:1). But the pistons themselves do have a difference -kinda. The oiler that squirts up inside the piston while running is larger so more oil gets delivered to cool and lubricate the piston. That lowers the piston temp, which allows more fuel for the same EGT. Combine that with the other changes found in the TM (9-2815-210-34P) (check the usable on column) and they are really different engines. Who wants to go through the manual and not all the parts that are different?

 

[mudguppy]

... That lowers the piston temp, which allows more fuel for the same EGT. ...

piston coolers will not affect EGTs. they may, however, allow a higher sustained combustion temperature (that we observe from EGT readings).

meaning: the LDS is running more fuel. more fuel = more power.

higher rocker arm ratio allows for more intake air to enter the combustion chamber. this would account for the higher CFM ratings of the LDS even though the cam and turbo is the same as the LDT.

more air + more fuel = more power @ _'x'_EGT

 

[fcdrifter13]

The compression ratio as specified is the same (22:1). But the pistons themselves do have a difference -kinda. The oiler that squirts up inside the piston while running is larger so more oil gets delivered to cool and lubricate the piston. That lowers the piston temp, which allows more fuel for the same EGT. Combine that with the other changes found in the TM (9-2815-210-34P) (check the usable on column) and they are really different engines. Who wants to go through the manual and not all the parts that are different?

Yes the static compression is the same but the dynamic could be vastly different

Dynamic CR

Sorry I am posting from my phone or I would copy and paste the excerpts

 

[JasonS]

The LDS piston squirter drops upper ring temperature by 100F; doesn't seem too significant.

 

[Floridianson]

Found the spring weights and the LDT is the only one that shows no weights?

 

[gringeltaube]

Found the spring weights and the LDT is the only one that shows no weights?

You mean no X = no springs..., yes, saw that too, it's just a mistake in that chart there.
See TM9-2910-226-34, page B-23 and B-24. It shows application for three different springs along all models. LDT would be part#SP9043, same as LD.

G.

 

[m-35tom]

some errors in previous posts.
2 hole injectors replaced the 1 hole. they don't spray onto the top of piston, rather into a chamber in it. oil cooling on ldt just sprays onto the piston. lds sprays into passages in the head of the piston. all considered, i have turned ldt engines up to at least as much power as lds.

tom