6v92 Lugging Prevention

Scott & Heather · June 21, 2012, 08:44:28 AM

Once again, you guys are amazing, and so right

Even if I don't always listen...

I was running our coach down some country roads for an hour or so and they were hilly and I just had to take it slow around 45-50 MPH. I initially just left it in 4th on my Auto 740 but I noticed an increasing and increasing amount of smoke out the tailpipe. Just slowly got worse. Engine was definitely low RPM and lugging. Downshifted just one gear and within 4 minutes, smoke cleared and never smoked again that day as long as I kept RPM up a little..not screaming, but no lugging either. At highway speeds, it's no issue, but these things seriously hate to be low RPM lugged! You've always said it, I just didn't get it. Now I do...crazy.

Busted Knuckle · June 21, 2012, 09:14:59 AM

Scott not only does the lugging cause smoke, but also HEAT!

Don't lug that baby! Run it hard and keep those RPM's UP! It's not yer gramma's Escort, it's built to run and RUN HARD!

These are the same engines used in commercial equipment and set to run full blast wide open throttle for days/weeks on end (being shut down only long enough to service them, then back to WOT!)

But please don't try to run granny's Escort this way, or you'll owe her a new car!

BK

Scott & Heather · June 21, 2012, 10:53:02 AM

chuckle. Bryce, someday I'll meet you, shake your hand, and thank you for the many laughs you've given me

Truth is, why doesn't an automaker make an engine that can take the beating like a Detroit? As for heat, so it actually runs hotter when lugging? Didn't know that..is that because the hamster cages are spinning slower?

Eric · June 21, 2012, 11:28:53 AM

Mazda rx8 or any winkle rotary engine....owned a few and they are happy screaming down the road !

Have fun !

Eric

Busted Knuckle · June 21, 2012, 11:35:20 AM

The heat build up has a lot to do with the extra fuel being dumped into the engine that can't be used properly because the engine can't turn the extra RPM's that it should be able too for the amount of fuel being burnt.

Also especially on a bus that has the engine and radiators in the rear (side mounted radiators) there is no forced air into the radiator like on a truck. So it depends on the fans to pull the air through the radiator to cool it. So the faster the fans turn, the better flow of air and more cooling! Plus less unburnt fuel generating extra heat in the cylinders.

So it's a combination of things. But he bottom line is these engines are designed to run for days on end at the set governor speed with out hurting them. (generators, pumps, and other field equipment do it all the time.)

BK

Busted Knuckle · June 21, 2012, 11:36:54 AM

Quote from: ekhedge on June 21, 2012, 11:28:53 AM
Mazda mx8 or any winkle rotary engine....owned a few and they are happy screaming down the road !

Have fun !
Eric

OK so you can drive grampa's Mazda MX8 like that all day long, but still don't try it with gramma's Escort.

BK

HB of CJ · June 21, 2012, 04:17:02 PM

Kinda surprised that your mighty Allison auto didn't automatically down shift and hold in a lower gear. But that can vary depending upon how the automatic is set up....some down shift real well, others, like yours, need a little helping hand....on the shift lever or button.

Yep....don't re afraid of running your mighty Detroit near or at max rpm for long periods of time....they actually LOVE it. With a 6V92 type mill, 1800 to 2000 rpm for rolling hills sounds fine. Broommm. Brooommm. HB of CJ (old coot)

Lee Bradley · June 21, 2012, 04:29:23 PM

Quote from: Busted Knuckle on June 21, 2012, 11:36:54 AM
Quote from: ekhedge on June 21, 2012, 11:28:53 AM
Mazda mx8 or any winkle rotary engine....owned a few and they are happy screaming down the road !

Have fun !
Eric

OK so you can drive grampa's Mazda MX8 like that all day long, but still don't try it with gramma's Escort.
BK

Mazda RX8 is another 2 stroke. :-)

muldoonman · June 21, 2012, 04:30:53 PM

My Old Boss years ago would replace his buses (Prevost and Executive Coach)) every other year and would run the dog out of them. I went with him to a shoot ( trap shooter) to Vegas one year in the early 90's. He got a ticket on the floor at 87 mph out of El Paso. He run um on the floor all the time. 8V92's!

Scott & Heather · June 21, 2012, 09:05:21 PM

Wow. That's cruising!
Yeah my Allison is stupid about when to shift. So I tell her what to do now. I think you guys might be talking about a Mazda RX-7 which has the Wankel engine in it. (although winkle sounded kinda funny)

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chuckd · June 22, 2012, 04:45:53 AM

Scott: I have a dumb Allison as well. I do all the shifting, it shifts too soon, and the revs drop too low.

Chuck

Tikvah · June 22, 2012, 08:08:09 AM

I'm glad to hear there are others who do their own shifting.... I thought I was crazy (no comments

)

I do all my own shifting, keep the RPMs up but never really knew if I was right. Seems it shifts hard too... but I think I remember that being normal.

It's automatic after-all

Dave

luvrbus · June 22, 2012, 08:19:00 AM

You guys need some adjusments doing all that shifting on a 740 I down shifted mine sometimes for the jakes and that was about it

good luck

wagwar · June 22, 2012, 08:50:16 AM

Quote from: luvrbus on June 22, 2012, 08:19:00 AM
You guys need some adjusments doing all that shifting on a 740 I down shifted mine sometimes for the jakes and that was about it

good luck

Mine shifts too late on a hill, causing the engine to 'lug' IMHO. So, how do I perform these adjustments to improve the performance of the 740?

boxcarOkie · June 22, 2012, 09:08:26 AM

Quote from: muldoonman on June 21, 2012, 04:30:53 PM
He got a ticket on the floor at 87 mph out of El Paso. He run um on the floor all the time. 8V92's!

Man-Man, with the deplorable condition of America's Highways (Infrastructure) 87 MPH would scare me too death!

You can have that. I am going to stay over in the slow lane and piddle around at 1900rpm and watch the circus in the smart-aleck lane roll on by.

BCO