On lugging a Detroit Diesel

[DrivingMissLazy]

my 04 going down the Westbound grade into Vail would max out at 76mph....no throttle or full throttle, I suppose if I gave it full throttle in that situation it would be lugging

Did you have a tachometer?
On any big downgrade my Eagle would continue to increase speed, It never maxed out. The highest rpm I ever got was 2500, but it was still increasing when I turned the Jakes on. Speed was past the peg on the speedometer, but I estimated 85mph.
Richard

[H3Jim]

My B500 allison kicks it up to a higher gear if I exceed 2200 rpm.  kind of scary before I added jakes.

And I confess, I have had it up to 90 or a little better.  I try  not to use the brakes at anything over 70 or 75, they don't really work anyway at the higher speeds.  5 lanes of open road, no traffic.  I hate to think what it did for my fuel mileage.

[gus]

You're lugging when you can no longer maintain speed at a given throttle setting, this includes at governor limit. You are overloading the engine.

DD, like almost any other engine, do not produce max torque at max rpm, all they do at max rpm is go faster. Max torque gives you the most work for your money. In my 671 that is around 1400-1600 rpm, but who wants to go that slow!

[tekebird]

True, but as the bus loses speed on the grade prior to the downshift it isn't lugging, it is doing what all other engines do while it is being loaded. or do you suggest to put the clutch in until the bus speed is down to the next gears top end then shift.  if this is the case on a grade that would require 2nd gear you should be in 2nd at the bottom because as soon as you start "bleeding" speed your luggin your engine??

I agree max Torque and max HP are not at Max RPM

[Buffalo SpaceShip]

True, but as the bus loses speed on the grade prior to the downshift it isn't lugging, it is doing what all other engines do while it is being loaded. or do you suggest to put the clutch in until the bus speed is down to the next gears top end then shift.  if this is the case on a grade that would require 2nd gear you should be in 2nd at the bottom because as soon as you start "bleeding" speed your luggin your engine??

An engine that can't pull a certain grade at partial throttle will soon lose enough RPM to be lugging, necessitating a downshift. A MUI engine under full fuel is in danger of overheating at any speed/grade. I suspect a DDEC is a different beast, and I have no experience with them. But as buswarrior so aptly states, a pyrometer is the best metric to determine throttle position and gear selection. Otherwise, 1500-1700rpm at partial throttle, with constant vigilance of the temp. gauge and black smoke from the tailpipe, is the safest bet on climbing grades. Automatic trannies are best shifted manually, because they will indeed lug an engine and shift down way too late. A tranny temp gauge is also a wise choice when climbing w/ automatics. Some autos utilize heat exchangers that only dump tranny heat into the engine cooling system, making climbs even harder.

Once I get my 4108 up to over 10,000MSL with my 8v71 and C65's, I'm blowing black and running hot no matter what I do. I attempt to get first lockup on my V730 and climb at partial throttle until the engine hits 200deg, pull over until she cools, and do it again. I suspect rad. misters and/or smaller injectors are in my future upgrade package if I choose to do a lot more high-elevation mountain climbin'. Or a smoke turbo, if I happen to hit the lotto!

FWIW,
Brian B.

[lostagain]

And how do you kook up a pyrometer gauge 40 feet away from the sensor/thermocouple? Does anyone know?

[Busted Knuckle]

Ah, well I can think of 2 ways! 40' or wire or use a regular guage,sending unit & stc. and use a camera to keep tabs on it! I've heard of several folks who've done just that, built a small box containing a set of gages with a camera in it to acurately monitor their engines performance! I think it's a way cool IDEA. I hope to do the same some day! FWIW BK

[Dallas]

And how do you kook up a pyrometer gauge 40 feet away from the sensor/thermocouple? Does anyone know?

Why not use remote data aquisition?
Nascar and the other major racing associations have been doing it for years.

Here's one from Advantage Motorsports:

EGT (Exhaust Gas Temperature) and/or
CHT (Cylinder Head Temperature)

These Racing Exhaust Gas Temperature sensors are available for those who require to know specific EGT temperatures at ANY portion of the racetrack.  Data graphs are plotted throughout the racetrack to let you see exactly what your engine is doing at any given point. Exhuaust Gas Temperature EGT sensor have exposed tips (not sealed tips) to give the fastest EGT reaction times to measure fuel mixture changes FAST.

  Note: Our temperature probes are designed specifically for high pressure racing appplications and should not be confused with "standard" EGT probes

$60 EGT or Cylinder Head Sensor with 2' Stainless Steel Lead.

http://www.advantagemotorsports.com/Sensors.htm

[belfert]

Why not use remote data aquisition?
Nascar and the other major racing associations have been doing it for years.

Nascar has an almost unlimited budget for this sort of stuff, some of it paid for by TV so they can overlay the data on the TV broadcast.

Busnuts generally don't have Nascar type budgets.  The price for the sensor is good, but I can't exactly figure out how much the rest of the system would cost.  It looks like $600 and up.

[gus]

teke,

No, the bus has been loaded all the time if it is pulling a hill. It is slowing down precisely because it is overloaded in that gear. It wouldn't lose speed if it weren't overloaded. Once you shift down to the proper lower gear you will be able to maintain a pretty much constant speed even though it will be a lot slower than you would like.

We busnuts are at a distinct disadvantage because we only have four speeds (most of us) and we have to compromise. I wait until the bus is a few mph above the next lower gear max mph and by the time I complete my shift down it is about right. At least that is always my plan!! When it no longer will maintain speed I slowly back off on the throttle until it slows down to this desired speed if it isn't already there. You can tell when more throttle does no good or if really over fueled you can see the black smoke. There is no point in holding the same amount of throttle if the bus is slowing.

If we had a nice 10-15 speed trans we could keep the engine at torque peak or at whatever rpm we wanted, there wouldn't be nearly the speed losses we suffer with only four speeds simply because we would not lose so much momentum between shifts.

[NJT 5573]

Here's the good news. You can purchase the Pyrometer of your choice from Isspro. They are the leader in the Pyrometer field for trucks. A nice one is $100 and they have several to choose from. (I prefer adjustable). The other thing you need is a lead from the engine to the dash of your bus. The 40 foot lead is part number R66-40 and sells for $74.54. The 35 foot lead is part number R66-35. Ref, Isspro.com on line catalog.

[Jerry Liebler]

Hey guys, fully loaded isn't lugging and it isn't the same as overloaded.  An engine that is slowing down with wide open throttle (max fuel in a diesel) is fully loaded and not over loaded.  Once it gets to the speed that allows a downshift it's certainly prudent to downshift.  Most automotive engineers define lugging as operation at engine speeds below the torque peak with wide open throttle. The torque peak on an 8V71 with standard timing is at about 1200 RPM, with advanced timing it's 1400 RPM.  My transmission ratios make 2100 in second the same road speed (30 mph) as 1250 in third which is a very good reason no one should put the so called 318 into a GM bus.  Also I've driven my bus over the continental divide 7 times, several times in 95 degree temperatures, without overheating or much black smoke probably because I have N60 injectors and standard timing.  I remember one  stretch of I70, in Wyoming where wide open in 4th gear it took 8 miles to slow from 70 to 60 and it was all over 6000' MSL. 
Regards
Jerry 4107 1120 

[Busted Knuckle]

I've driven my bus over the continental divide 7 times, several times in 95 degree temperatures, without overheating or much black smoke probably because I have N60 injectors and standard timing.  I remember one  stretch of I70, in Wyoming where wide open in 4th gear it took 8 miles to slow from 70 to 60 and it was all over 6000' MSL. 
Regards
Jerry 4107 1120 

Jerry I'm sure you meant I-80/Wyoming or I-70/Colarodo or Utah. I been all over this great land of ours and at no time or place has I-70 ever gone through Wyoming that I am aware of. FWIW BK

[Sojourner]

Common expression of lugging is:
"If you drive too slowly in third gear, you'll lug the engine"


True definition of "engine lugging" is over throttle (added more fuel or decrease Air/Fuel ratio) while engine in max straining order at low RPM at a given torque below the needed vehicle's torque load to gain speed. Another word need to shift down so vehicle's loaded torque is below engine's strong to max torque load. Otherwise unable to increase RPM plus thick black smoke. It very hard on engine's rod bearing (squeeze oil to a point of touching crankshaft's journal while in power down stroke) & piston's skirt to a point of stuffing.

If you only lugging momentary or 2-3 seconds....it usually ok but do not make a habit of doing it again.

Lugging is expensive...either now or later, period!

FWIW

Sojourn for Christ, Jerry

[Jerry Liebler]

Bk,
You are absolutely right the long fast climb is on I 80, westbound.  The steepest bit of interstate was on I70 eastbound approaching the Eisenhower tunnel, that was where I had to use second gear. It must be my age showing I was thinking I80 and typed I70.
Regards
Jerry 4107 1120