Continental Multifuel LDT465 1D Running Hot

[Bantha RV]

Hi guys and gals,

I have a 1971 M109A3 with a stock (as far as I know) LDT465 1D. The FDC has been bypassed by the military. It runs good, no excessive smoke, starts easily, water temp stays between 190 and 200 under load, etc... I recently put in a boost gauge and EGT/Pyrometer (in the rear flange right above the turbo) in preparation for adjusting the fuel settings. Initial readings under load at 2000rpm are 9# of boost (expected), and 1150* on the EGT (COMPLETELY UNEXPECTED AND WORRISOME). I'm concerned that the EGT is so high without having made any adjustments. Most advice I've seen says to ensure your EGT never exceeds 1100, and that I should be able to get 15#-18# of boost and still be below 1100 on the EGT. Any thoughts on why it's running so hot with no tweaks at all? Does the smoke cam effect EGT? should I add or remove a click or two on it and see what happens?

Thank you in advance for any help you can offer.

Craig

 

[Floridianson]

Just a thought have you checked the air filter? In most cases we can see higher temps if the rpm are low and we can not get that hot charge out quick enough. Yea 1150 is a little hot for 2000 rpm but wondering if it would have come down if you went to 2500. If increasing rpm does not bring them down then yea to much fuel.
As for the smoke cam. The main fuel control / double nuts has a wedge plate and the smoke cam and or droop has it's own wedge plate but they fit together. After the FDC was bypassed the FDC wedge plate no longer moves. So when you adjust the main fuel / twin nuts for EGT's then you adjust / change the smoke cam you are changing the main at the same time. Yea 1200* is getting pretty hot so we down shift/ increase rpm or as said to much fuel adjustment we just do not want to stay at 1200*. As for adjusting the main fuel / twin nuts being very careful not to break the wedge plate stud when you loosen the jam nut. You can leave the jam nut loose and adjust the inner nut to increase or decrease fuel while test driving. You can use marker or paint to paint one of the flats on the main fuel nut so you can see your adjustments easy. After you find the right amount of fuel to keep EGT's where you want them then you can tighten down the jam nut. As said do not let the stud turn as it will snap easy. Use very thin wrench on inner nut so as not to over lap outer jam nut and hold the inner nut so it does not move or both nuts move at the same time. That will break wedge stud. Also does you truck have a muffler as that can increase EGT's?
Had to add this to thread what do you mean under load? Do you have tonnage in the bed or just weight of truck going up grade / hills? Yea to much weight and two much fuel and we do get in trouble and even more so with low rpm.

 

[cattlerepairman]

The FDC could have been bypassed, without the concurrent reduction in fuel delivery being made. The screw would have to be turned in a few flats.
If it hasn't, that's ok, if you run a pyrometer. It gives you the extra oomph when you want it and you control your right foot and check the pyro, especially during high load low rpm situations.
If the pyrometer is pre-turbo, you can run it up to 1200 for short periods of time. I wouldn't recommend more.

The military set up the trucks so that even a deaf and blind operator holding the throttle pedal to the floor under all driving conditions would not be able to exceed safe EGT.

That the truck would be a dog as a consequence was not a concern.

I prefer to have a bit of power on tap when needed.

Also, which turbo do you have? Screaming Whistler C turbo or much more quiet D?

The C turbo won't make 15psi willingly. The D can.




Sent from my SM-G950W using Tapatalk

 

[Bantha RV]

Just a thought have you checked the air filter? In most cases we can see higher temps if the rpm are low and we can not get that hot charge out quick enough. Yea 1150 is a little hot for 2000 rpm but wondering if it would have come down if you went to 2500. If increasing rpm does not bring them down then yea to much fuel.
As for the smoke cam. The main fuel control / double nuts has a wedge plate and the smoke cam and or droop has it's own wedge plate but they fit together. After the FDC was bypassed the FDC wedge plate no longer moves. So when you adjust the main fuel / twin nuts for EGT's then you adjust / change the smoke cam you are changing the main at the same time. Yea 1200* is getting pretty hot so we down shift/ increase rpm or as said to much fuel adjustment we just do not want to stay at 1200*. As for adjusting the main fuel / twin nuts being very careful not to break the wedge plate stud when you loosen the jam nut. You can leave the jam nut loose and adjust the inner nut to increase or decrease fuel while test driving. You can use marker or paint to paint one of the flats on the main fuel nut so you can see your adjustments easy. After you find the right amount of fuel to keep EGT's where you want them then you can tighten down the jam nut. As said do not let the stud turn as it will snap easy. Use very thin wrench on inner nut so as not to over lap outer jam nut and hold the inner nut so it does not move or both nuts move at the same time. That will break wedge stud. Also does you truck have a muffler as that can increase EGT's?
Had to add this to thread what do you mean under load? Do you have tonnage in the bed or just weight of truck going up grade / hills? Yea to much weight and two much fuel and we do get in trouble and even more so with low rpm.

Thanks for the tips. Pyro is pre turbo. Underload means pulling a 7% grade. Higher RPMs definitely helped reduce the EGT.

 

[Bantha RV]

The FDC could have been bypassed, without the concurrent reduction in fuel delivery being made. The screw would have to be turned in a few flats.
If it hasn't, that's ok, if you run a pyrometer. It gives you the extra oomph when you want it and you control your right foot and check the pyro, especially during high load low rpm situations.
If the pyrometer is pre-turbo, you can run it up to 1200 for short periods of time. I wouldn't recommend more.

The military set up the trucks so that even a deaf and blind operator holding the throttle pedal to the floor under all driving conditions would not be able to exceed safe EGT.

That the truck would be a dog as a consequence was not a concern.

I prefer to have a bit of power on tap when needed.

Also, which turbo do you have? Screaming Whistler C turbo or much more quiet D?

The C turbo won't make 15psi willingly. The D can.




Sent from my SM-G950W using Tapatalk

It has the D turbo. Runs great on the level. Makes 4-6 psi at 2500rpms and nice and cool (750*-800*). I live in Wyoming and I plan to use truck all over the Rocky Mountain west. Just hoping to claw my way up the hills a little better. Home is a t 6500' so the air is thin, and I've got to go up in any direction I travel to get out of the valley. The turbo makes a huge difference at altitude like this, but I think the altitude density may be affecting the measured boost and the EGT because of the fuel air ratio.

 

[cattlerepairman]

Yes, your level readings look very much ok. The turbo pressure you listed sure is not excessive (my D-turbo delivers beyond the gauge limit of 15 psi without hesitation, if I don't watch it).
That you are at altitude is of course important. You would indeed see higher EGT readings. As far as I can see, there is nothing to worry about in your setup, as long as you keep an eye on the pyrometer and keep it under 1200 for extended periods of time. I would add that you also will not want to keep the rpm at redline/governor for long. I know, others disagree, stating that their truck can take it just fine, but the military had certainly some experience with Deuces blowing their guts all over the road when climbing mountain passes at screaming rpm.

If you want total peace of mind, turn the fuel delivery back to what the military states in the TM. Boost will max out at around 7 psi and you will wish you had never ever driven it on any hill with the fuel turned up because now it will be....sssssllllooooowwwww.

Of course, what you really want is my setup with the LDS engine....210 hp and rated for 2800 rpm

 

[Bantha RV]

One other thing. What systems are we trying to protect by monitoring the EGT? The turbo itself seems obvious, but I've heard people talk about melting the heads or the pistons, which seems a little out there. I've seen people mention that they use 1100* as a limit because the melting point of aluminum is 1222*....what specific components are they concerned about melting?

Excerpt from "JATONKA sponsored study of adjusting fuel rates using Dual EGT gauges And the differences between pre- and post- turbo readings"

"So the big question is, what constitutes excessive EGT? If everything is working properly, 1250º to 1300º F is a safe turbine inlet temperature, even for sustained running, mile after mile. Above 1300º F things can start to get edgy. Remember, excessive EGT damage is cumulative. Over 1400º F., you're usually gambling against a stacked deck and it's only a matter of time until you lose. The higher the EGT, the shorter that time will be."

I want my truck and motor to last. I don't need it to go any faster than it already does (I have 395/85 R20s on it 46" diameter, so 55mph indicated is 63mph actual....and I'm cool with that....and it seems to be too because it will do that on level road at 4-6psi boost and 750*-800* EGT all day long) I would like its drivability and hill pulling to be a little better if possible, but not at the expense of reliability. Where is the balancing point?

Just trying to be a good truck dad. Want it to be its best....but not abuse it.

 

[Bantha RV]

Yes, your level readings look very much ok. The turbo pressure you listed sure is not excessive (my D-turbo delivers beyond the gauge limit of 15 psi without hesitation, if I don't watch it).
That you are at altitude is of course important. You would indeed see higher EGT readings. As far as I can see, there is nothing to worry about in your setup, as long as you keep an eye on the pyrometer and keep it under 1200 for extended periods of time. I would add that you also will not want to keep the rpm at redline/governor for long. I know, others disagree, stating that their truck can take it just fine, but the military had certainly some experience with Deuces blowing their guts all over the road when climbing mountain passes at screaming rpm.

If you want total peace of mind, turn the fuel delivery back to what the military states in the TM. Boost will max out at around 7 psi and you will wish you had never ever driven it on any hill with the fuel turned up because now it will be....sssssllllooooowwwww.

Of course, what you really want is my setup with the LDS engine....210 hp and rated for 2800 rpm

I want that Waterloo power steering you've got for sure! I feel like my 46" tires are my overdrive.

 

[cattlerepairman]

I have no experience running 395/85 R20 . It appears to me that their overall diameter is not that much more, compared to 11.00R20 and therefore the increase in top speed ("overdrive by tire") is comparable. The 395s are, however, much more mass to rotate and the width may also cause higher rolling resistance; both of this sucks more engine power. The 11.00R20 tire weighs about 140 lbs, the 395 weighs 220 lbs or close to it.

While the tire size is helpful on flat ground for better top speed and lower rpm at other speeds, I would suspect that, for better uphill performance, less rotating mass would be preferable, as would be a smaller tire diameter.

JATONKA's research does suggest that the "balancing point" you are looking for sits around 1200 degrees; while I do not want to stay there, he says it is ok to sustain it. 1300 and up becomes hairy.

The Deuce with its LDT is what it is...it was marginally powered when new and belongs to the class of vehicle that will never be fast going up a steep grade. Downshift, go slow and watch the flowers and the bees. Eventually, you will arrive at the summit.

If you really need to get somewhere quick, take a different vehicle