So what's up with...

[John316]

I have read in some posts, that you all have talked about driving your Detroits hard. We have always driven really gently. Easy accelerations, not working the engine harder than necessary...you get my point. My question is, do we need to drive ours harder. We have a S60. My thought is that the two strokes need to be driven harder than our S60 does. But am I mistaken? I would still have a hard time driving our bus harder, and not taking it easy, but I want that engine to last as long a possible.

If we do need to drive it harder, what are the reasons? Is it because it prevents buildup of some sort in the engine? It runs cleaner? Uses less fuel (okay, I know it doesn't )?...

Thanks for putting up with me...

God bless,

John

[JackConrad]

When people talk about driving a DD hard, I think they are talking about the 2 cycle and mean to keep the RPM up.  Most 2 cycle engines run better (longer) if the RPM is kept in the "PowerBand" whic his usually towards the higher end of the RPM range.  Jack

[VanTare]

John316 S60 like the 1200 to 1500 rpm range they have problems when you run in the 2100 rpm  range for long periods of time at least mine do 

David

[NJT 5573]

The S60 is a million mile engine if it gets maintence and thats pulling up to 105,500 lbs, so I don't think you can find a way to hurt one as long as it comes up to operating temp in a light duty situation like a bus.

[NJT5047]

I agree with the other 'NJT'...as long as the oil is changed and air cleaner serviced, you cannot damage the engine.   You can't over-rev, and it has DDEC limits that prevent damage to the engine due to low oil, hot oil or water...etc. 
As Jack says, 2 strokes are definitely sensitive to lugging.  Your S60 was born to lug. 
You gotta drive the two strokes like you stole'em.  An S60 just goes. 
One thing a heavy foot does on an S60 is consume a lot more fuel.  That won't hurt the engine.  And, the engine won't 'carbon up' or any such thing. 
Long term idling isn't really good for any diesel, but unless you like to sleep in the bus with the OTR AC running even that's unlikely to be an issue.
A maintained S60 will outlast the typical RV coach owner.
I'd love to have an S60.  But...being 'retarded' and all that...$$$$$$ ain't gonna happen. 
I have bus lust for an E model too...but that ain't gonna happen either.
JR

   

[VanTare]

John316 I don't get that kind of mileage from mine they are not a trouble free engine a great engine but not perfect.The maintenance can get expensive on the s60 a set of injectors can be over 8 grand for new set and the warranty on injectors are a 100,000 miles not a million. FWIW I have seen more run 600,000 miles than a million I never saw one run a million miles and I have 18 of the S60 and the warranty doesn't mention a million miles


David

[gyrocrasher]

1993 KW, 430 hp S60. Bought it with 825K, sold with 1.14Million. Still running strong.No internal work while I owned it. No internal warranty work, at least, before I bought it. Mitch

[John316]

Thanks guys, that makes a lot of sense. I suspected that the two strokes had to be driven like that, but I wanted to be sure.

One other question. We don't have Jakes (yet ), so when we go down a significant down grade, we usually downshift. (We also have a retarder on the transmission, but that gets the transmission hot very quickly.) So we are going down a grade, slowly, and have it in third. The engine winds up, as we gather some speed, and we use the brakes/retarder to slow down. (Sadly we don't have a tach, yet, so I go by sound.) My concern is, "Is it possible to over-rev the engine?" If we just let her drift, in third, what would happen? Seems like the engine would over-rev and cause damage, because we keep gathering some speed. Does anybody know what would happen?

BTW we have a Allison B500 transmission.

Thanks for putting up with me .

God bless,

John

[NJT5047]

Sammy could answer your question affirmatively, but my best guess is that you could overrev the engine by allowing it to take off downhill.   If you go over the max road speed in a given gear, it's overrevving.    I also guess that an S60 is far more sensitive to over-revving than a typical 2 stroke.
I've got an Allison trans retarder on a two stroke, it'll definitely overrev my engine.
However, minimal brake  easily maintains a safe speed...Use some brakes.  Downshift, and keep the speed under control.   
I-40 at Black Mountain and I-26 coming out of Ashville is the only places that I frequent where the retarder is especially useful.   Although it is 'on' all the time.  Unless on wet roads.   
You know to turn the trans retarder off when driving on wet or slick roads?     
I doubt that the retarder is programmed to 'drop' out.  That would be dangerous.  A blown engine would be more desirable than driving off the moutainside.
Once the transmission overheats, it won't shift.  And it'll set a 'Check Transmission' light.
Is your CTL light coming on?  Do you have a trans temp guage? Does it read high?   If not, it may not be as hot as you think. 
JR

[John316]

Thanks for the replies.

NJT, We will be getting a tach soon. So that should help. We use the brakes, and downshift, just like you described, thanks. Good point on turning the retarder off when the road conditions are bad (rain, snow, etc). And again you are right, our retarder doesn't "drop out." We have a temp gauge on our tranny. I think that it is pretty accurate. We have never had the CTL come on. We just don't let it get that hot. We also have TranSynd (SP) in our transmission, so we can get even hotter...

Thanks again for all of your help. It has answered my questions.

God bless,

John

[NJT5047]

John, FWIW, you can figure out your engine RPM for whatever speeds you wish to calculate.  Pick a gear and road speed and figure backwards.   All you need is tire diameter, road speed, trans ratio for whatever gear you are calculating, and diff ratio.

JR

 

[junkman42]

My mc7 has an HT70 with retarder and jakes,it will almost go backwards up a hill!  Has more stopping power than is necassary.  The retarder will raise the tranny temp on a long grade.  John

[HighTechRedneck]

John, FWIW, you can figure out your engine RPM for whatever speeds you wish to calculate.  Pick a gear and road speed and figure backwards.   All you need is tire diameter, road speed, trans ratio for whatever gear you are calculating, and diff ratio.

JR

Here is one of several online calculators for helping with that calculation:

http://www.csgnetwork.com/rpmcalc.html

[John316]

Thanks a LOT guys. That is very helpful. I will calculate backwards. GPS helps to get the exact speed...

God bless,

John

[buswarrior]

The B500/DDEC computers will not allow you to wreck the engine. It will upshift, as will every normal Allison I have ever seen or read about, when engine speed is just short of nuclear.

The retarder in a B500 will outperform a Jake. Yours may need some programming, previous owner may have had their own ideas as to what they wanted. You have the 4 position or 6 position on yours?

The D model MCI's had issues with transmission temps. To get the best cooling, you want higher engine RPM than 6th gear when descending. Rad fan, coolant flow, all superior at higher RPM. Use the transmission the same way you would without the retarder, downshift as needed to get the engine RPM high, and use the retarder joystick as necessary to control road speed.

Check to see what tranny cooler yours has, there was an update available.

happy coaching!
buswarrior