L10 or S50?

[Brian Diehl]

If you could choose between a 330hp S50 or 330hp L10, what would you choose and why?  Both engines are at or near their maximum power capability (standard) and both engines are good at producing gobs of torque.  Thoughts? Ideas?

[rv_safetyman]

Brian, both engines are know as good reliable engines. 

Most L10s were mechanical engines.  That would make the installation easier if your bus does not have an electronic engine.  The L10 became the M11 (electronic) and then the ISM.  It will fit in many buses without raising the bed and is short enough to not need any kind of extension.  The electronic version (M11 and ISM) is quite popular with Eagle folks as it fits the engine compartment easily and has ratings up to 500 HP and torque up to perhaps 1500 ft lbs.

The Series 50 engine is newer technology and has most parts common to the Series 60.  It is a long life engine.  It has the bad rap as being a vibrating animal.  I took some time to look at Jack Campbell's Series 50 in his Eagle at Bussin 2007 and it did not seem to shake any worse than my Series 60 at idle (worst condition).  He did not do anything exotic with the engine mounts. 

Some general comments. 

1)  Any engine conversion is a HUGE project. 

2)  Almost all four stroke engines have their best operating characteristics (power and mileage) at about 1400 – 1500 rpm.  A bus geared for a two stoke will be geared too low to take advantage of the four stroke characteristics.  The gearing should be changed to reduce RPM by 20 – 30%.

3)  There is a bid division on engine converters concerning the use of mechanical vs electronic engines.  I strongly recommend electronic engines for a host of reasons (too many to list here).  The MAJOR reason is fuel mileage.  There is a great deal of divergence of opinion on the subject, but the prevailing thought seems to be about 10% better for the electronic.  Not enough to justify an big engine conversion project from 2 stoke to 4 stroke, but big enough to justify the electronic engine if you are going to go to a 4 stroke for some other reason.

Just a few thoughts.

[RJ]

Brian -

Based on my experience with both engines (Gillig Phantom transit applications), the L10 would be preferable.

Being four cycle engines, they both vibrate more than the two-strokes at idle.

The S-50 will rattle the fillings out of your wisdom teeth.

Inline six cylinder (L10) vs inline four cylinder (S50), the six is much smoother.

The M-11 is even better than the L-10, more HP & torque.

All of our S-50s, L-10s and M-11s were electronic engines hooked to Voith automatics.

FWIW & HTH. . .

[Brian Diehl]

Thanks Russ,
The real big benefit to me is I think I can make the S50 work with my current HT754.  My 754 was just recently rebuilt and I *really* want to keep it.  I just found out the S50 is 43" long (same length as the ISL BTW).  So, I think I can squeeze it in with my tranny if I can take one more inch out of my drive shaft length.  I still trying to find out if the motor I have an option on can be turned up to 330(or 350) hp with out major cost.  I also am still trying to get additional confirmation from DD that I can use it with out an Electronic tranny...

I know not having an over drive is not ideal, but given my money situation and no running engine right now I'm considering doing the engine swap now and a few years down the road going to a overdrive automatic tranny as funds and time allow.  My benefit is I have a 3:33 rear end which helps get my rpms down compared to the standard 3:83? MCI rear end.

[TomC]

Brian- I think the real question you should be asking yourself is how many more miles are you going to be driving your bus?  If over 200,000 miles, then by all means consider an engine swap.  If not, the best, cheapest, least time consuming and headache producing will be to up the horsepower of what you have.  If it is a 8V-71, I can tell you that turboing will really wake up the engine.  Even switching from a 8V-71 to the 8V-92TA will be a relatively easy switch since they are both the same engine outside, sans the front vibration damper on the front of the 8V-92 engine.  From experience, the 8V-92 can be made to be a real rocket (530hp and 1800lb/ft torque).  8V-92TA was also available with DDEC.  The difference between fuel mileage of a mechanical 4 stroke and an electronic 2 stroke is the same.  The fuel difference between the electronic 2 stroke and the electronic 4 stroke is about 1 mpg.  Is that worth the time, effort, aggravation, headache of an engine switch, I personally think not.  Good Luck, TomC

[Brian Diehl]

Tom,
I appreciate your words of wisdom.  Believe me, I've strongly contemplated keeping my engine ... but, it is going to cost me more to do an "okay" job of fixing the engine as it currently stands then it will to buy a used S50.  Yes, I understand there is still a LOT of work to be done after getting the engine.  Also, in the case of this particular option I'm pursuing I'll have access to the wiring harness, muffler, CAC, alternator, computer, tps, etc for a reasonable amount of money of the donor.  I can't predict if I'll drive the bus for another 200,000 miles, but I am as confident as I can be that I will put at least 100,000 more miles on it.  I've already put 30000+ miles on it in the past 4 years.

So, given I really dislike this 6v92 and just don't want to spend money on it, I'm going to continue to pursue the S50 option once I'm 100% convinced I can use it with my HT754.  All bets are off if I can't reuse my current tranny due to length restrictions.

And yes, there are still a bunch of details about the potential donor I need to figure out, but it is not research that I'm afraid of doing.

Again, thanks Tom for continueing to make sure I and others understand all our options and costs associated with them.
-Brian

[RJ]

Brian -

I still think you ought to more seriously consider the six-cylinder Cummins over the four-cylinder Detroit, especially if the overall length is the same.  Much, much smoother engine, the six.

The fact you've got the 3.33:1 rear axle is a real plus, in this situation.

Bridgestone makes a drive tire in the 11R24.5 size that turns 470 revs/mile, the lowest revs/mile of any tire I've seen that will fit our coaches.  This size would, in effect, also lower your final drive ratio, to work better with the lower-revving four-stroke.

A one-inch difference in driveline length isn't much, but the angles induced into the U-joints might exceed design limitations with it shortened.  Might want to talk to a driveline specialist. . .

Might also want to seriously consider a turbo MUI 8V71T, set for 350 or 370 hp.  Less of an installation headache, no need to shorten driveshaft, virtually bulletproof w/ the 754, a great powertrain combo.  Had several MC-9s with this set-up at the charter company I worked for back in the mid-80's.  Pulled better than the 6V92s, almost equal to the 8V92s.  Ran forever with routine maintenance.

As with all MCIs, just watch the temp gauge and downshift manually when pulling grades, to keep the engine in the 1800 - 1900 range on a partial throttle.  Doing that will help tremendously to avoid overheating problems.

At least you're doing your homework!!

FWIW & HTH. . .

[TomC]

Brian- the Series 50 used to be offered in the Freightliner FL106, which was a very short hood.  Some other engines that were the same length were the Cummins ISL/ISC, Caterpillar C9.  But NOT the Cummins L10/M11/ISM.  That needed a 6" longer hood.  Along with the Cat C10, C11,C12,C13 and the Mercedes-Benz 4000 engine.  I believe that the Series 50 was just about the same length as the 6V-92TA, just about the same weight (maybe 200lb heavier).  Grayhound converted some of the MCI9 and MCI12's from 6V-92TA to Series 50's.  They removed one of the radiators and converted it to the air to air intercooler.  The Series 50 doesn't require much cooling since it is so effiecient.  You should get 10mpg with it.  I personally think it is the PERFECT (even with the bit of vibration at idle) motorhome engine.  With the 3.33 and 11R-24.5, your rpm with the HT754 (you could use the HT740-the Series 50 doesn't need the extra gear because of such good low end torque-it might work better because the 740 is more rugged than the 754) 60mph @ 1591; 70mph @ 1857; 80 @ 2122 (top speed)-so it'll work!  The 6 speed world transmission whether it be the HD4060, B500, 4000HS, 4000MH, would also be great since the first 4 gears are identical to the HT740 with two additional overdrives.  The non pto version is shorter than the HT740!  Good Luck, TomC

[Brian Diehl]

Russ and Tom ...

I'd love to put an ISL in this bus... but I can't find one.  I've looked in MN, SD, OH, and FL and can't locate a single used ISL.  So, yes I'd love one and it is about the same length and 600lbs lighter than the S50.  Any ideas on where I could get a good used one for under 6k?

On the tires ...  Is 12r22.5 a smaller tire than the 11r24.5?  Is the 11r24.5 the same as what truckers use?  I think my 12r22.5 is 485 revs/mile if I remember correctly ....

I can't fit the L10/M11 without replacing the transmission with a shorter one ...  I'm still open to that, but haven't found a used 4000 HS yet.

[Tom Y]

Brian, I measured my L10 at 44 inches long. But I do not have a big front pulley, and this is to the bell housing not crank end. I looked at a S60 measured that compared to the M11 and I had the length of the S50 compared to the S60. The L10 is longer than the S50 and the same as the M11. I had a M11 to put in and found a couple L10s with 0 miles new spares. Could not pass on them set up for busses. Sold the one thru Ebay for 4250.00. When you look at the S60 copared to the M11 it is BIG. The S50 350 hp is rare, 330 hp odd, 300hp more common. My electronic L10 was 280 hp change the exhaust side of turbo and need progam change to get 330. I was told I could go 350 put should change exhaust valves. To me not worth the bother. I would put a tone wheel in the Allison if you go this way, I had to pull my engine and trans to do it. I am not doing it for the milage. I was going to a 6v92 but the 748 would not fit. So I sold both, bought a M11 then found the L10S. I do have a electronic Allison a running take out but no computer. Cheap.  I put a 740 with my L10. Still not running yet, did not work on since March but back to now. The pedals are different from Detroit to Cummins.  Tom Y       

[m-werx]

Hi Tom have you still got the m11? Darren

[Tom Y]

Darren, No it got Ebayed.  Tom Y

[NJT5047]

Coaches similar to 96A3s came with 8V92TAs offered as an optional powerplant...That's at least a 10"-12" longer engine?  Is your transmission longer than an HT740R...The retarder adds considerably to the length of the HT 740R trans...my point is that you should be able to run at least several inches shorter driveshaft without issues. 
One thing's for certain, the engine cannot be easily moved toward the rear of the bus without moving the squirrel cage blowers...the bumper brace inhibits same. 
I'd give some serious consideration to repairing your 6V92, or buying a rebuilt....repowering is soooo much work.   I'd (almost) be tempted to buy  another bus with a 4 stroke after looking carefully at what others have done...and the amount of work involved in doing it.   Saw Jim's Eagle/S60, Jacks new S50, and Sonny's Cat.  Those guys are good!   I'm sure you are too!  I'd like to see what you do...
Someone could (maybe) make some bucks by designing a cradle and intercooler package for MC8-9-96 and 102A series MCIs for a specific 4 stroke engine conversion.  Maybe a 50S...it does fit the engine compartment.    Bernhard does this for a 60S I believe...
You're ahead over most of us with your 3.31 axle. 
Good Luck, JR

[Brian Diehl]

Coaches similar to 96A3s came with 8V92TAs offered as an optional powerplant...That's at least a 10"-12" longer engine?  Is your transmission longer than an HT740R...The retarder adds considerably to the length of the HT 740R trans...my point is that you should be able to run at least several inches shorter driveshaft without issues. 
Good Luck, JR

Hi JR,
Yes, the HT754 I have is 40" long!  That includes the output shaft/drive shaft flange.  With the 6v92 in there I'm very short on space.  This fact is why I mention I could consider a longer engine like the M11 if I go to a different transmission.  The problem for me is I invested almost $5k 3 years ago to have the transmission overhauled and really want to stay with this transmission since it is a known good entitiy that will last without issues for as long as I own the bus.
-Brian

[belfert]

Isn't a series 50 taller than a 6V92?  How are you going to accomodate the extra height?  Jim (RV Safety) had to put his Series 60 up through the floor under the bed I believe.  I think this is a big reason why folks repower with the Cummins motors instead.

My bus has a factory Series 60 and the floor in the back few feet is raised a bit to clear the engine.  Older buses have a flat floor further back than I do.

Brian Elfert