If anyone has actually swapped a series 50 for an 8V71 I sure would like to know the comparative fuel economy. Should I keep dreaming of doing this swap?
Regards
Jerry 4107 1120
I swapped my 8V71 MCI 5a bus that got 6.4 mpg for a Series 50 RTS bus that gets 10.75 mpg at 60 mph.
6.4 mpg seems fairly low for a 35' bus. Was the series 50 a fresh engine?
What axle ratio does the RTS have? Also what transmission in both the MCI and RTS?
If you swapped the whole bus then many other variables are at work, not just the engine.>>>Dan
You'd be looking at 2.5-4mpg better. But then you have all the electronics to set up. IMHO-better to turbo your engine for more power. The fuel mileage savings will not offset the cost of setting up the electronics. And if you ever have to have the bus towed because of electronics failure (which is highly likely) you completely offset all fuel mileage savings, up and beyond the time wasted. Properly setup, the mechanical 2 strokers are extremely reliable-probably the most reliable engines ever made. Good Luck, TomC
How many times do electronics really fail? Obviously I know lots of people with cars and I very rarely hear of the electronics in cars failing.
TomC, you sell trucks. How many of those come in with electronics failure?
Electronicsfailure might be more likely on a engine swap just because of the custom wiring harness.
I would say it is not some much an electronics failure to worry about........but sensor failure.
I have seen many a new car sitting on the side of the road overheated when the sensor for the fan went inop........thus overheating.
the real question is it worth the time and money..................ANSWER: NO, NEVER.....Unless.......you need the 12 step program for having the need to Futz with stuff
The Cost and Time involved, let alone the possible problems you MAY have will never be recouped.
Similar example:
I want to buy a 3/4 ton pickup......should I get the diesel.......it's a 6000.00 option and will get a few miles per gallon better than the big gas engine.
I went thru this decision once did all the math with the engine cost vs fuel cost at the time.........to realize the fuel savings..........I would have to keep the truck 20 years.........now this did not account for the added resale when selling the diesel........IIRC over 10 years I would have only recouped 3000.00 of a 6000.00 option.........now that 3000.00 I would have lost.........would have served me much better at earning interest in a CD or something
Now this situation didn't also take into account the time and problems involved with the SWAP or problems down the road.
When CA mandadted that some of it's State Subsidized Commuter buses be repowered with the 50, it was done by a company that specializes in such things......and even they had problems with the SWAP.
I see trucks coming in on the hook almost daily. When I say electronics failure, that can be anything from complete CPU failure to a loose wire to a sensor-but enough to stop that engine. And that is with any make of truck or engine that is electronic.
When I was driving, the only time I had to be on the hook was for a mechanical failure. And in 1.3 million miles of driving that was only twice (engine related). Once for a blown water pump, and the other for a fuel pump. Otherwise, I was able to disconnect, or jump, or something to successfully get to my next destination (and sometimes run for days-like when my shut off solenoid failed) without interruption. The ONLY reason electronics were introduced is for smog control. Good Luck, TomC
I only know of three people with this swap..none will post here....people on here have told them it won't work is unreliable and too expensive....Just goes by if you can actually do this by yourself...from start to finish...VS 8v71 at least 4 mpg..but better off throttle and useable tq at all highway speeds...A highway geared donor bus still the best way...then you will have something that will run with anything built....All modern comp controled work so much better than old mui...Can still remember when if you could not fix it for your self setting beside the road you could not afford to drive a bus conversion...now its all glitz and what you can pay someone else to do..go figure..gg04
Given the resourcefullness & tenacity of the one who started this thread, I doubt that the electronics will be much of a road block.
I think a S50 would be cool! However, I have pondered this for a while & the thing I keep coming back to is the shaking issues with a large displacement 4 cylinder. They can only be dynamically balanced for a narrow RPM range. Naturally you would want this at normal cruise RPM. That leaves lots of shaking at idle.
Then comes the cost/ benefit ratio. I just can't get there either, not while my engine is a viable means of propulsion.
My RTS with Series 50 has a 4:11 rear end, and a 731R transmission. The "R" means it has a retarder, which is really great. The retarder provides about as much slowing power as the Jakes on my old MCI. I don't know what transmission the old MCI 5a has... I think a 642??? 3-speed automatic model.
I don't have other than normal vibration with my Series 50, at any speed, and including at idle. I read many posts before I bought the Series 50 bus about how the shaking at idle would shake my teeth out. This turned out not to be the case. The engine is quieter than my 8V-71, and has no more vibration than that engine did, probably less. The RTS goes up mountains MUCH faster as well, almost keeping up with traffic. The main place it's slower is from a dead stop. There it feels like it takes longer to get up to speed. I think it's the EPA computer keeping me from accelerating faster. I didn't care for it the first few weeks, but I've gotten used to it, and I love the power in the hills, so it's a more than fair trade, particularly since I almost doubled my fuel mileage.
Kevin
With a factory install on the RTS, it was obviously engineered properly. It is easy to take the results of a properly designed system for granted.
The natural frequencies of the components involved can be very complex. I doubt I'll be able to do as good a job if I was retrofitting one in my bus - maybe my concern is a result of too much school, the vehicle dynamics classes were rather intimidating.
The vibration issue is real! A in-line 4 cylinder is inherently dynamically unbalanced. The larger the displacement, the larger the vibration. That's why you don't see many in cars larger than 2.4 liters. If you deal with it correctly, no one notices anything. If you get it wrong, the results aren't good. I have been in buses that had a strong low frequency vibration that was so bad, it was making people sick.
The chance of a successful completion of any task is improved if potential problems addressed in the planning stages rather than ignored.
I'd still like to put one in my cruiser. maybe one day. . .
Was the RTS still being made when they started putting the Series 50 in buses? I thought the RTS buses with Series 50s had all been retrofitted by various companies on behalf of transit operators who needed to meet smog regs?
Kyle4501- I hope I can put the vibration issue of the Series 50 to bed finally. S50 is the only engine made where the oil pump has to be timed since it drives counter rotating balancing shafts to cancel out the vibration issues. Granted an 8.5 liter 4 cylinder is not going to be as smooth as a-say-8.3 Cummins 6 cylinder. But given the fact that the bigger the cylinder displacement is with fewer cylinders means better fuel economy (mainly less friction-and the 8V-71 has a bunch of friction). I have ridden on S50 transit buses in the back to listen to the engine, and except for a minor amount of vibration at idle (no more than any other 4 stroke Diesel), it really ran well (was in a 60ft transit that was filled). Personally, I think the S50 is the perfect bus conversion engine-It is reliable, gets up to 350hp and 1100lb/ft torque (like a well tuned 6V-92TA), gets unbelievable fuel mileage, 1 million mile life expectancy, doesn't leak oil or burn oil, is short in length, requires little cooling (on MC8 & 9 Grayhound converted over from 6V-92TA and took one of the radiators out and replaced it with the air to air intercooler-shows how efficient the S50 is). If I had the room of a 4501, I wouldn't think twice about installing the S50 since you have two radiator mounting possibilities and plenty of room. Plus-wouldn't it be nice to get 8-10 mpg with an automatic, or 10-12 mpg with a manual? Good Luck, TomC
Yes, there are lots of RTS busses out there that left the factory with Series 50 engines. They are starting to be sold off now by the transit districts. I got mine for $10K, in very good shape, with no rust, and under 400K total miles. This included the destination signs, new front tires and a wheelchair lift that worked perfectly. I spent $3,500 more to have the 4:11 gears installed, and $2,000 to have a 4 point leveling system installed. I take it in for painting tomorrow. The quote is $4K for two colors. Does that sound fair?
Quote from: TomC on June 06, 2007, 08:28:22 AM
. . . .10-12 mpg with a manual? Good Luck, TomC
Mine has the 8V71 (brown tag injectors) & 4 spd manual with 3.70:1 axle ratio. According to the previous owner, that is about what he got as long as he stayed out of the rockies. He kept a log that showed every expense. He put over 400,000 miles on it as a band tour bus.
So far,
EVERYTHING he told me concerning this bus has proven true. He didn't drive like a maniac either, rather he had learned the 'sweet spot' & that's where he cruised.
I never said a s50 wouldn't work, just pointing out the biggest difference between the 4 & 6 cyl 4 strokes. If you accept this fact & include it in the design of the refit, problems can be minimized & future enjoyment will be maximized. (The shaking MUST be considered when planning a swap or you will experience premature hose failure where they connect to the engine. Also, there must be room for the engine to move.)
I know more than I want to concerning the counter rotating balance shafts used on engines . . . The short version is they only dampen some of the vibration, & it depends on a lot of variables to how effective they are. The fact that it will last 1,000,000 miles says a lot for the durability of the design.
Some people are more sensitive to vibration than others. I know the vibration of my 8V71 is almost nonexistant & since it runs fine w/ no smoke, I can't justify changing it any time soon. However, if I find a suitable donor drivetrain with an automatic & overdrive & jakes, all bets are off. ;)
By factory install, I was referring to a quality professional install vs a hack job by some monkey with a smoke wrench.
We have a case tractor we put a cummins N-14 in out of a truck with all the electronics from the truck. It has worked great untill about two weeks ago when it died , so i took the ECM into cummins and they told me it was dead! No big deal rite, think again they said they had a rebuilt one for only $2995.00!! thats how much we paid for the whole motor used with all the electronics. So as others have said stick with the old mechanical motor much less to go wrong and cheaper to fix!!
Two cents from the person that did one.
DD said in there info that the series 50 did viberate any more than the series 60. They should know more than anyone else about that.
It only takes 3 wires to make the DD ecm work. If the ecm is bad or if you have a bad sensor it may not run. These problems are few and far between. If you need a ecm for a DD you can get a 1V on ebay for $800.00 and get it programed for another $200.00.
Lets get this out of the way next. Had my bus 21 years. Started with fair 8-71, rebuilt it to new spec. in 1993. Got about 6 miles to the gal. Changed to 8-92 in 1998. The 8-92 was a reman from DD that was set up for 350 HP. Made a bad change by raiseing the HP to 475. I could out smoke any one and only got 4.5 miles to the gallon. There were no hills after that, if you could keep it cool enough. That cool enough was a big problem.
Now I have a series 50 in the old bird. Been in sence last November and I have only put a little over 3,000 miles on it so far. Did the change over myself with help of 2 friends. Took about 250 hr of labor. The next one won't take but about half the time. Won't have to learn electronic engines again. Lots of time spent reading and looking to make sure there were no mistakes.
The engine that I put in came out of a city bus, that was monunted sideways. The transmission reversed the direction. I used all the parts that I could from the city bus. Had to buy some air and oil lines, fan drive and lots of welding.
There is no way that I would change back. The bus runs the best that it ever has. Not as much power as the 8-92, but getting twice the fuel milage. That is two times as much. Best cruse control that you could have and jake brake works better than any 2 cycle.
I like mine so well that this winter I am going to take out a 6-92 in a 102A3 and replace it with another series 50.
If I can help anyone that wants to make the change let me know.
Even though I just had my 8V-71 turboed and intercooled, and it puts out a respectable 375hp and 1125lb/ft torque, I am getting about 5.5mpg with it. My 10240B AMGeneral transit was actually a Flyer D800. These buses were made in one model or another, first by GMC called the classic, then MCI also called the classic ending in 1992. Santa Monica bus lines has some MCI Classics running with the Series 50 and B500. Seen the engine cradle, and it looks exactly the same. When Santa Monica finally retires those buses, I'm going to buy one and just switch the cradle and rear end cradle along with the gas pedal and shifter. Then will have close to a 10 mpg bus with a modern engine and transmission. It is getting harder to find mechanics that are still familiar with the 2 strokers, and also finding the Delo 100 40 weight. Good Luck, TomC