Turbo boost hits 15 psi plus

[jimk]

You could experiment. Then you'll know your options.

Adding fuel adds boost because combustion gasses have more volume than air. That spins the turbine faster. As boost goes up the air getting compressed gets hotter, expanding even more, and while there may be more air the charge density is less. You will get to a point where compressor efficiency drops off. That will heat the air even more. Hot boost is bad. You might not be able to get there with a C.

There will be a point [somewhere] where adding more fuel will just make more smoke.

I don't plan to get too greedy. The LDS is supposed to have a bigger turbo, waste gate and stronger pistons. Perhaps a bigger radiator(?). All that and still no intercooler. I'll be very happy if I can get half way there (~150HP)

I reduced fuel 1/2 turn. Will testdrive and adjust as needed in a few hours.Towing stolly to Cobleskill. JimK

 

[jimk]

Well 200 miles of towing 14T gave a good enviro to set the fuel. That 15+ I had got a half turn less (3 flats) before this drive. Within a mile I could tell it was still too high, running at 14psi and 900*F to, and at times, to just under 1000*F (pyro post-T). Real strong though. Might have gone higher [EGT] if I didn't lift. I stopped 15 miles out and reduced fuel an additional 5 flats. Got it right were I wanted. 12psi at 2500rpm. ~13psi at 2600( but I usually don't go there, so this is ok). Temp dropped about 100*F to 800-850 on same terrain(flat). There was a noticeable drop in power but it is still much stonger than as a LD.

Engine seemed to be real happy at 2200-2300rpm/49MPH running 10-11psi at steady 800*F. The new power curve is a bit higher [rpm] probably because there is more boost there.

EGT climbs and boost drop as rpm drops. And quite consistently. For example: 2000rpm is 8-9psi at 850*F, 1800rpm is 7-8psi ~900, 1600rpm is 6-7psi and ~950*F. Going below 1500 seemed to heading for too hot (1000, for me) but a downshift is usually prudent before that time. Note:ambient air temp was 50-60*F during this. I should add the deuce has a 45mph rating at max payload/max towed, and I was over this.

I run it a bit without stolly/trailer when back. I was unable to get these same max boost and temps readings, probably because it reaches max rpm so fast and there is a need to lift. I guess that more fuel (boost) would be ok for a less demanding enviro. Slightly higher EGT may be ok too, in my opinion, for -brief- periods as for a recreational usage vehicle (I try to avoid above 975). Also, the required fuel adj seemed very easy to predict, with minimal driving and only one previous adjustment.The old LD was overfueled. Someone probably tried to turn it up because power was so low. JimK


p.s. Stolly had to sit out the parade as the throttle slave had a fit minutes before the start. I can't blame it as it needed attention and I had no extra time. The Deuce was my primary concern and it preformed it's task almost flawlessly. The only problem with truck/trailer was a few miles before getting home the NAPA muffler seems to have broke something inside. Now there is a nasty rattle at 1200rpm. The high point ot this weekend was ~ 3 hour early morning drive(deuce) on some dirt roads/trails/mountains/State Forest 10/15 miles SW of Cobleskill. Power steering, quiet, lots of power, no cars, now where to go, no map, full tank of fuel...

 

[jimk]

Update-I disabled the FDC and got 15+psi at ~2000rpm. IP required 2-1/6 turns (13 flats) to get back to 12psi at 2500rpm. Power output was very dramatic before turning it down. Power and boost came in earlier, and faster (lower RPMs). I may adjust the droop screw to try and fatten up the low end. JimK

 

[cranetruck]

Thanks for the confirmation Jim.

 

[m-35tom]

fuel rate

of course if you disable the fdc your fuel rate will go up and you will have more boost and higher egt. the fdc is after all an automatic fuel rate control. if you feel you have to disable the fdc you should 'start over' in checking and setting the fuel rate. the manual says to have 9psi boost at 2300 rpm, they don't care about egt since it will be safe at this boost level. it also says 5psi at 1500 rpm for the droop adjustment. as to how to measure this boost, the book says to have 2 people, put the truck in low range, 1st gear and use the brakes to hold the rpm at 1500 or 2300 when at full throttle. the second person watches the boost gauge while the first drives. now for a truck that is not afraid of hills you can install a egt gauge and observe the industry standard max safe temps. i have found that 12 psi gives 1250 egt, your results may vary slightly because of fuel, and inaccuracy of gauges.

 

[Billy Bobbed]

Love this thread a lot of info.My next gauge is going to be a turbo boost gauge.I need to know what my turbo puts out.

 

[andystamey]

Just wanting to clear something up, is everyone talking pre-turbo or post-turbo EGT. You could easily have a 300 degree decrease from pre-T to post-T measurements

 

[tm america]

Mine did the same thing i think something stuck in the injection pump but i haven't pinpointed it yet ... I installed a new boost gage and egt .. to keep an eye on it... and one thing i realized was i'm getting some oil in the line going to the boost gage.So i am guessing the turbo is giving off some oil .. That's probably where the extra fuel is coming from as far as i see right now. ....Also my friend has some extra fuel filters for a lds 465-2 if you need them ..he said you could have them just pay the shipping ..