Bus Conversions dot Com Bulletin Board
October 24, 2014, 11:00:16 AM *
Welcome, Guest. Please login or register.

Login with username, password and session length
News: If you had an Online Subscription: It will not be stolen by your mailman or your neighbor who also may be into buses.
   Home   Help Forum Rules Search Calendar Login Register BCM Home Page Contact BCM  
Pages: 1 [2] 3 4 5 6 7 ... 9   Go Down
  Print  
Author Topic: Repower MC9 Conversion from 8V71  (Read 14395 times)
Melbo
Hero Member
*****
Offline Offline

Posts: 1070


MC8 under construction




Ignore
« Reply #15 on: October 25, 2010, 10:30:44 AM »

Just as a heads up -- I only get about 7 mpg --- drive it fast and 6.8 --- drive it slower and 7.2

I did not figure I could pay back the repower from the fuel mileage but because I didn't have to rebuild the two stroke and change the tranny to auto

I would have spent the same money to upgrade and keep the two stroke.

YMMV

HTH

Melbo
Logged

If it won't go FORCE it ---- if it breaks it needed to be replaced anyway
Albuquerque, NM   MC8 L10 Cummins ZF
bevans6
Hero Member
*****
Offline Offline

Posts: 4762


1980 MCI MC-5C




Ignore
« Reply #16 on: October 25, 2010, 10:34:02 AM »

I spent a lot of time researching a swap to a Series 50.  I spoke to a number of people who had done this.  It needs a new differential gear or a high overdrive gearbox, or both, and the average timeframe for the physical install was around 45 days of actual work, whether bought out or done by a highly skilled owner.  The cost was estimated $15K to $30K, not including a transmission.  For me the biggest issue was going to be getting the computers talking to each other and to the bus...

I decided 3 mpg wasn't worth it.  People who had done it uniformly praised the change.  I guess I decided that if I wanted a bus with a 4 stroke, I would just buy one and be done with it.

Brian
Logged

1980 MCI MC-5C, 8V-71T from a M-110 self propelled howitzer
Spicer 8844 4 speed Zen meditation device
Vintage race cars -
1978 Lola T440 Formula Ford
1972 NTM MK-4 B/SR
rv_safetyman
Hero Member
*****
Offline Offline

Posts: 2199


Jim Shepherd


WWW

Ignore
« Reply #17 on: October 25, 2010, 11:18:44 AM »

Alan, on this and BNO, you have been given some pretty good advice.

If you are SURE that your engine is toast, I would do a rebuild since you have the ability to get it done inexpensively.  The engine is easy to remove and your boys can work on it a lot easier when it is out.  Again, make sure that your engine is, indeed, toast and is not just leaking or using oil because someone stuck the wrong oil in it.  As you probably know, you can inspect the cylinders without tearing down the engine.

Then, stuff it back and and drive it while you do your homework on a four-stroke. You can recoup a significant part of your rebuild cost when you replace the engine by selling your 8V71.  Keep good records and take lots of photos so that you can document the rebuild.

After you do your homework - take your time - you will make a good decision.  20-30K per year begins to add up in terms of fuel savings.  I estimated in my article that I saved about $4K in 50K miles of driving. 

Since you have a clutch already, then a truck transmission with overdrive makes good sense when you go to the four-stroke.  Better yet, the AutoShift is also a good way to go.  I really don't think an OD will do you much good with the 8V71, as you need to keep it wrapped up.

Jim
Logged

Jim Shepherd
Evergreen, CO
85 Eagle 10/Series 60/Eaton AutoShift 10 speed transmission
Somewhere between a tin tent and a finished product
Bus Project details: http://beltguy.com/Bus_Project/busproject.htm
Blog:  http://rvsafetyman.blogspot.com/
luvrbus
Hero Member
*****
Online Online

Posts: 12762




Ignore
« Reply #18 on: October 25, 2010, 11:40:59 AM »

Jim, it is not funny but I had to laugh your 4000 dollar fuel saving went by/by with all the problems you have had lately your in the hole buddy.
If the guy doesn't like 2 strokes best for him to get something else he will never be happy that is the reason most of the 2 stroke people don't waste their time responding.


good luck
Logged

Life is short drink the good wine first
rv_safetyman
Hero Member
*****
Offline Offline

Posts: 2199


Jim Shepherd


WWW

Ignore
« Reply #19 on: October 25, 2010, 05:27:06 PM »

Clifford, good talking to you today.  Yep, by having to get the second Series 60, my savings were overshadowed by the costs involved.  Maybe I could look at it as paying for most of my replacement engine  Grin Angry.

My gut feeling is that the 6V92 would have been a problem if I had put a ton of money in the rebuild and then tried to have it pull 46K pounds up these CO hills (service truck is 9.6K).

I talk a little about buying an engine in my article.  I made a huge mistake believing that Series 60 engines were all  "million mile" engines.  I worked with statistics much of my working life and should have understood.   My engine had over 650K miles and I had a very uneasy feeling.  At the time, it was about the only engine available within a reasonable distance.

Southern Oregon Diesel got bitten several times by installing used engines in buses.  As I understand it, they would only install engines they rebuilt after they got bitten several times.

The issue today is that everyone wants to avoid four-stroke EGR engines.  That dictates engine prior to about 2003.  It follows that these engines have a ton of miles on them.  Not a good situation.  I have suggested to a couple of folks that the consider getting a salvage engine and have it rebuilt.  Hard to justify the cost when you only put a limited number of miles on in a year. 

For my second engine I was fortunate to find an engine in a wrecked truck where I could verify that the engine had be rebuilt (220K miles previously) by a DD dealer (got receipts from both the owner and the DD shop).  Even that does not guarantee that I will not have problems. 

Because I did all the work myself, I am not out much more than it would have cost to rebuild my 6V92 that spit up (at DD rebuild cost).  Having said that, if I paid myself $5 per hour, the conversion would have cost me about a million dollars  Grin Grin Grin

Jim
Logged

Jim Shepherd
Evergreen, CO
85 Eagle 10/Series 60/Eaton AutoShift 10 speed transmission
Somewhere between a tin tent and a finished product
Bus Project details: http://beltguy.com/Bus_Project/busproject.htm
Blog:  http://rvsafetyman.blogspot.com/
TomC
Hero Member
*****
Offline Offline

Posts: 6854





Ignore
« Reply #20 on: October 25, 2010, 11:27:11 PM »

Rebuilding you're 8V-71 will be the best and cheapest way to go.  Once overhauled properly, you'll probably never have to do another over haul again-suggest you restrict your injectors to N60's for best fuel mileage and longevity.

Another way to go is to find a crashed trash truck with a Cummins ISM and Allison world transmission. Buy the whole truck (make sure it hasn't been pilfered) so to get all the wiring and parts for the electronic engine and transmission.  Then you'll have an engine that will get 8-10mpg and and enjoyable automatic transmission to drive (I drove 1.3 million miles truck with 13spd transmission-I have Allisons now).  Good Luck, TomC
Logged

Tom & Donna Christman. '77 AMGeneral 10240B; 8V-71TATAIC V730.
RoyJ
Full Member
***
Offline Offline

Posts: 178





Ignore
« Reply #21 on: October 27, 2010, 04:38:52 PM »

IMHO, a commonly underestimated engine is the little Cummins ISB, specifically the latest 6.7L. Without the emmissions crap, they'll happily make around 400 hp and 800 lb-ft of torque.

Now, they'd never stand up to commerical duty cycle at those power levels, but for an RV, it's perfect. The best part is, they're everywhere in junk yards from late Dodge HD pickups.

The only think I'd be worried about is the 68RE transmission. They're fine for the Ram's 26,000 GVW, but on a coach with 36,000 GVW, I'd spend a grand or 2 beefing it up and add a big cooler. That said, hot shot haulers routinely gross 36,000 stock.

You'd have to gear the diff to run about 2000rpm @ 60mph. Which requires roughly 5.13 on a 42" tire. By doing so you'd have a passing gear (5th) of 2600rpm@60, and hill climb (4th) of 3000rpm@60, with a whole bunch of gears for lower speed - a lot better than the stock 8V71, especially at altitude.

You'd easily get 10mpg with this setup, and have minimal cooling requirements.
Logged
arl
Newbie
*
Offline Offline

Posts: 11





Ignore
« Reply #22 on: October 27, 2010, 04:56:33 PM »

Roy,
   I don't doubt your word, and if you're right, I'd be very interested to pursue your suggestion.  But I have a few questions:

1.  Is the ISB a 2-stroke?  Why the high rpms?  3000?  That sounds high, even for me, who is used to 2300 rpm cruising speed at 64mph.  I thought THAT was high.  The poor 8v71 sounds like its hurting itself.

2.  10mpg is my dream goal.  Are you just shooting from the hip or is that really possible?

what do the rest of the board readers say about this?

thanks!
Alan
Logged
bevans6
Hero Member
*****
Offline Offline

Posts: 4762


1980 MCI MC-5C




Ignore
« Reply #23 on: October 27, 2010, 05:18:51 PM »

The ISB is the dodge ram pickup truck engine.  it's a good engine but it makes its power from rpm's not raw displacement.  I wouldn't put one in an MC-9 on a bet.  It's OK up to maybe 25,000 lbs and slow, you'll be 10K over that and you already think the 8V-71 is slow.  All that said, you can over-fuel the thing to death and get 400 or even 600 hp from it, for a little while!  Mind you, I think it's the best pickup truck engine every created, and the earlier versions were even better, for pickup truck use...
Logged

1980 MCI MC-5C, 8V-71T from a M-110 self propelled howitzer
Spicer 8844 4 speed Zen meditation device
Vintage race cars -
1978 Lola T440 Formula Ford
1972 NTM MK-4 B/SR
luvrbus
Hero Member
*****
Online Online

Posts: 12762




Ignore
« Reply #24 on: October 27, 2010, 05:23:15 PM »

ISB 5.9 L
ISL 8.3 L
ISM 11 L 

The ISB is not going to cut it in a 40 ft bus


good luck
Logged

Life is short drink the good wine first
robertglines1
steam nut
Hero Member
*****
Offline Offline

Posts: 4024





Ignore
« Reply #25 on: October 27, 2010, 05:34:17 PM »

reason I ask where you were is their is a preowned engine guy in Central City-Ky he also does rebuilds       Bob
Logged

Bob@Judy  98 XLE prevost with 3 slides --Home done---last one! SW INdiana
arl
Newbie
*
Offline Offline

Posts: 11





Ignore
« Reply #26 on: October 27, 2010, 05:43:36 PM »

OK. I hear the cautions about the ISB (5.7 L) not being big enough.

So what about the ISL?  I have a friend who has one with an Allison world transmission in a wrecked country coach RV for $7k, not including controller/remote.  I could probably get it for $5K plus the controller (which will then require programming as well) for another $2K.

Is that reasonable and doable?
Logged
robertglines1
steam nut
Hero Member
*****
Offline Offline

Posts: 4024





Ignore
« Reply #27 on: October 27, 2010, 05:56:21 PM »

8 v 71 = aprox 9 ltr   61 cubic inches per ltr  568 inch in 8v71
Logged

Bob@Judy  98 XLE prevost with 3 slides --Home done---last one! SW INdiana
belfert
Hero Member
*****
Offline Offline

Posts: 5448




Ignore
« Reply #28 on: October 27, 2010, 06:13:53 PM »

I would personally stay far away from an ISB.  They put out a lot of HP, but not a lot of torque.  Stock they put out less torque than an 8V71 I believe.  A Series 60 puts out around 1,350 lbs of torque and up.  Torque is as important as HP in a large vehicle.  Remember that 26,000lbs is the maximum load for a pickup pulling a trailer.  It is very rare for most pickups to be loaded that heavily.

Diesel pushers used to use a lot of the ISB, but now they mostly use the ISC or similiar and bigger.  Freightliner uses the ISB in their diesel puller today, but that is about it.
Logged

Brian Elfert - 1995 Dina Viaggio 1000 Series 60/B500 - 75% done but usable - Minneapolis, MN
RoyJ
Full Member
***
Offline Offline

Posts: 178





Ignore
« Reply #29 on: October 27, 2010, 06:58:26 PM »

I knew I'd open up a can of worms with the ISB. Think about this: thousands of 40' school buses, grossing 30,000+, run around everyday with ISBs tuned to mid 200hp (for commercial longetivity).

Now, put on 5000 lbs more, but add 150hp, and suddenly it's not possible? A lot of people doubt it simply because it hasn't been done, not because it isn't possible. The MCI 102 I drive at work dynos 290 rwhp with an 8V92, nobody ever doubts its ability. Now, put in a 350 rwhp ISB, and all of sudden it's big no-no?

Yes, there is one catch - you'll have to run high rpm due to lack of torque. But compared to what? An ISM? Sure. But 8V71N? which makes what, 900 lb-ft with common injectors?

Remember, toque can always be made up from gearing, but hp always remains constant (law of physics). As long as you're making the horsepower needed at the crank, gearing will ensure enough toque is available at the rear axle. This is why I stressed the importance of a 5.00+ gearing.
Logged
Pages: 1 [2] 3 4 5 6 7 ... 9   Go Up
  Print  
 
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.18 | SMF © 2013, Simple Machines Valid XHTML 1.0! Valid CSS!