M35A2 LDT - Advanced Timing Question

[mitchsc0tt0]

Hey All,
My truck was originally a non turbo LDT truck and I added a turbo on a few years back (never retarded timing). Now I was reading that not retarding the timing could hypothetically get more horsepower but I am wondering if that is really true on our trucks. Currently monitoring my boost and EGT on steep hills and in 4th / 5th around town I never really see more then 7 pounds boost and 1040 degrees on the egt. (that was also with 1 ton in the bed)
I am wondering if I should retard the timing to the with turbo spec to get more boost power or simply crank the fuel screw up more? Interested to hear the thoughts on what you all think.

Truck Specs:
FDC Bypassed - fuel screw never turned down (.25" currently showing)
Injectors checked recently 3100 PSI pop off no leakage
395 XL tires
D turbo

 

[ToddJK]

Does it seem like the truck is lagging bad? If not, I'd leave it be.

 

[mitchsc0tt0]

On flat ground it seems great mainly up a hill it seems kind of slow. I know its not meant to be fast, but it seems the low RPM under 1700 really doesn't spool the turbo or even for that matter hit high egt and has a harder time getting up to that 2000rpm area. especially if its under 1500 it does not want to come up to speed.

Does it seem like the truck is lagging bad? If not, I'd leave it be.

 

[ToddJK]

On flat ground it seems great mainly up a hill it seems kind of slow. I know its not meant to be fast, but it seems the low RPM under 1700 really doesn't spool the turbo or even for that matter hit high egt and has a harder time getting up to that 2000rpm area. especially if its under 1500 it does not want to come up to speed.

Might be worth adjusting the fuel screw. You running straight diesel or a fuel blend?

 

[mitchsc0tt0]

Currently fuel blend but usually I do diesel every other tank and it seems to stay around the same results.

Might be worth adjusting the fuel screw. You running straight diesel or a fuel blend?

 

[Floridianson]

PM sent with phone # way to much to type.

 

[SCSG-G4]

I usually downshift when it drops down to 1700 under load. 1800 is generally considered as the max torque point.

 

[gimpyrobb]

Get a pyrometer and if you aren't hitting 1200* turn up the fuel.


If you are hitting 1200* take your foot out of it!

 

[mitchsc0tt0]

Thought everyone would find this interesting. So I went ahead and adjusted the ip timing to the correct LDT timing and noticed without touching the "go fast screw" better response overall (at least torque up a hill) and more boost now topping out around 9psi and no rise in EGT still hitting a max of around 1070 around town. So it would seem adjusting the timing after adding a turbo does provide some benefit maybe? Hard to say without actually having a dyno or anything but it at least feels like it.

 

[rustystud]

Thought everyone would find this interesting. So I went ahead and adjusted the ip timing to the correct LDT timing and noticed without touching the "go fast screw" better response overall (at least torque up a hill) and more boost now topping out around 9psi and no rise in EGT still hitting a max of around 1070 around town. So it would seem adjusting the timing after adding a turbo does provide some benefit maybe? Hard to say without actually having a dyno or anything but it at least feels like it.

Did you drive the truck after installing the turbo and then after driving adjust the timing ?
What I'm trying to find out is this feeling of extra power due to the turbo or the timing.

 

[mitchsc0tt0]

Yeah its had the turbo installed for quite some time I think roughly a year or two. Had some free time and an extra set of hands so I figured I would try adjusting the timing to what its set to factory.

Did you drive the truck after installing the turbo and then after driving adjust the timing ?
What I'm trying to find out is this feeling of extra power due to the turbo or the timing.

 

[rustystud]

Yeah its had the turbo installed for quite some time I think roughly a year or two. Had some free time and an extra set of hands so I figured I would try adjusting the timing to what its set to factory.

So you had the turbo on for some time, then you adjusted the timing to the TM's specifications, correct ?
So you used the factory settings on timing. You didn't go "rogue" and try and see what advance you could set it too for the extra power.

 

[mitchsc0tt0]

That's correct it's now set to ldt/lds timing mark. When I added the turbo a year or two back I never changed it and left it on the ld timing mark. Technically I was rogue before this post as I think leaving it on the LD timing would be adding more advance BUT I dont think I saw more power (maybe more top end but I definitely think I lost some bottom end). I do see more boost pressure now though.

So you had the turbo on for some time, then you adjusted the timing to the TM's specifications, correct ?
So you used the factory settings on timing. You didn't go "rogue" and try and see what advance you could set it too for the extra power.