Hello,
Hope everyone had a nice Thanksgiving! I have a friend that is thinking about buying a bus for a conversion project and he ask
me about the 8V-71 engine. I said I would would post some questions.
1. Would this be a first choice engine?
2. Is there enough power for this heavy bus MC-8?
3. Is it low on up keep?
Any help would be great, as I will pass it on to him!
Thanks,
Steve 5B.....
If I may, I would like to add to this... and pose another question.
I would like to know the answer to the question posed above as well as the 6v92 T or NA... against the 8v71.. Which is the better motor? From my searching on this forum, I believe they are close to the same HP, but I would guess the 6v92 is better in the mountains because of the turbo. Does either lend itself to modifications better? I would also guess that the 6v would be more fuel efficient as well?
The 6V92TA makes more horsepower on less fuel and weighs less, no need to modify or "hot rod" it, will also fit all transmissions that the 8V71 will>>>Dan
The 6V92 is also more sensitive to overheating issues.>>>Dan
All 92 series engines have wet liners all 71 series engines have dry liners. All of them can and have been turboed. Depending on what is available and how much work/money you want to invest anything can be a good starting point. 8v71n's are rated from 270 to 335, thats at sea level and altitude seems to really get to them. 6v92 are usually rated at 350 and can get up to 400, those ponies are good up to 10,000ft altitude. A turboed 8v71 will be very similar. The two engines are almost identical in displacement so performance wise they are very close. The 8v weighs a little more and is physically bigger. The biggest difference is the wet vs dry liner debate. Dry is a little harder to rebuild but has the advantage of never leaking coolant in the oil. Those are most of the facts you need to work with.
If you want more horsepower out of a 8V-71, it can be rebuilt into a turbocharged and air to air intercooled putting out 400hp and 1200lb/ft of torque with 80 injectors. 90 injectors can be used, but should also be used with a multi speed transmission for closer gear spacing-getting 450hp and 1350lb/ft of torque. I turbo'd and air to air intercooled my bus with a 8V-71 and with 75 injectors, has 375hp and 1150lb/ft torque-a very big improvement in performance.
If you're going to change the engine, I highly recommend you changing to a 4 stroke engine-like the Cummins ISM that weighs the same as the 6V-92 (2,100lbs) and can be rebuilt up to 500hp and 1550lb/ft torque for RV use. Then you'd have hill climbing and fuel mileage all in one. The Cummins ISM with 10spd Ultra shift transmission (no clutch pedal) would afford you the best possible fuel mileage. 10mpg wouldn't be out of the spectrum. God Luck, TomC
Quote from: Utahclaimjumper on November 30, 2008, 04:22:42 PM
The 6V92TA makes more horsepower on less fuel and weighs less, no need to modify or "hot rod" it, will also fit all transmissions that the 8V71 will>>>Dan
This is the common belief. Personally, I am taking the 6V92 out of my Eagle and replacing it with a 8V71 Turbo because the 6V92 is underpowered. The 8V71, if built right, can go far beyond 400hp. The one that is going in my bus is already built and we will be 'de-tuning' it back down to around 450 just because that will make it more streetable. The 6V92 does weigh less though. The 8V71 Turbo is my engine of choice. When I first got into buses I talked to a lot of guys who have been doing this a long time and they all sang the praises of the 8V71.
Yes but you have don close The rest of us do not
uncle ned
4104 1 "hot" 6v92&730
huggy bear
here is a link that I ran across while searching thru the archives... I found this on google...
http://www.busconversions.com/bbs/index.php?topic=9931.0
from this forum no less !!
The best bus conversion engine is the one that is already in the bus and trouble free.
There is not nearly as much savings as already having a good power plant in the shell.
You do NOT have to re-power, the stock engine is quite capable of pushing you across the continent without spending any more money to reach the summit 30 seconds earlier.
That said, the early 6V92 were not as fast as you might like off the line, and many stock installs were at the 277 HP rating, not 350 HP. And when you get into the DDEC motors, you need a computer that is rated, not just the hardware.
For your comparison in east coast bump climbing:
I have an 8V71, stock 280HP, and it runs me around just fine.
I have driven a loaded MCI EL3 Renaissance with 400 HP Series 60 and Allison B500 up Fancy Gap in Virginia on I77 at 50 mph, same speed in both 4th and 5th gear.
My MC8 with 8V71 and Allison 740 will climb it at 44 mph in 3rd gear.
So, spend your cash as you see fit, that's what do-it-yourself is all about!
happy coaching!
buswarrior
turbo;10 to 12 mpg is going to be the exception for a 450 or 500 hp Cummins if they have the gear ratio Cummins recommends 4.33 to 4.88 it is going to be a 5 mpg engine.That is the standard engine for a VanHool bus and having friends that use the ISM in their 40 and 45 ft Monocos, Foretravels and Van Hools they average about 5 mpg.Some of these guys get away with using the 3.73 and 3.36 gears for good fuel milage with 10 speeds.
I have friend in NM that has a new Dynaquest truck conversion that has a smaller 330 hp ISC Cummins with the Allison 3200TRV transmission with 4.88 rear gears he was told to expect 13 mpg his average is 8.4 when he ask the question about the low fuel milage he was told "that is what we got on our test tank at 60 mph" I have a 60 series in my bus and average about 5.5 at 70 mph so do your own research on mileage not what you read on these boards FWIW my DDEC 8v92 got better mileage than the new 60 series it got 6.5 mph
have a great day
well, since I have not even got a bus yet.. just trying to do some research first. Since I am familiar with turbo motors.. That is what I will probably stay with, Buswarrior, you are right.. Unles the coach I buy has no motor, or needs a rebuild, I will not be repowering anytime soon. Just trying to do some research before committing on one bus.
I've got a 6-92 and the biggest determining factor in my fuel mileage is how much my foot weighs on any particular day, I've never been one to try to beat a porsche off the line or crest a hill with a full head of steam, I'm just kinda relaxed and I get where I'm going when I arrive, to me thats the important thing lol. As long as you are still looking for the perfect bus, pick one with the perfect engine/tranny combo, much cheaper to get the right set up to begin with than to repower later.
Quote from: makemineatwostroke on December 01, 2008, 07:33:04 AM
I have a 60 series in my bus and average about 5.5 at 70 mph so do your own research on mileage not what you read on these boards FWIW my DDEC 8v92 got better mileage than the new 60 series it got 6.5 mph
have a great day
That is very interesting!
If good fuel mileage is important, get the fuel curves for the engine & look at the gearing of the bus. This will guide you as to where you will find the optimum operating speed.
All engines will have a rpm range where they make the most HP per Lb of fuel. Operating in this range will yield the best fuel mileage. This is where more gear choices can come in handy. ;)
Ignoring this explains why there are such varied reports of fuel mileage . . . . .
My 4501s have the Greyhound spec'd drivetrain (8V71 @ ~270hp, 4 spd, & 3.7:1 ratio) still in 'em & I get ~10 mpg on the East coast. I ran about 65 mph & I wasn't interested in being the first one up the hill.
Be wary of buses that someone has changed out the power unit to something other than factory supplied, especially if they radically increased the HP. Many potential problems can arise from a non-engineered system. Cooling issues come to mind.
All that said, the 8V71 is a reliable engine that will soldier on long after it is due for a rest . . . . A 'smoke' turbo can be added (to a healthy engine) without replacing all the internal parts -IF- the boost is kept low enough. . . . ;D
It would be enteresting to see a "turbo Motor", seeing as a "motor" is an electrical device, most turbos I ve seen are on "engines" as in internal cumbustion.>>>Dan
Quote from: Utahclaimjumper on December 01, 2008, 10:40:36 AM
It would be enteresting to see a "turbo Motor", seeing as a "motor" is an electrical device, most turbos I ve seen are on "engines" as in internal cumbustion.>>>Dan
HAHAHA...very funny!! Yes, you are indeed correct... motors are electric, engines are internal combustion... ;D ;D
There is a problem with your engine if you don't get more MPG with the series 60 than you did with the 8v92. Any 4 cycle engine that is set up like it should be will get better milage that a 2 cycle when running at the same power and speed.
Jack
Maybe not if the gear ratio puts the engine operating at the 'wrong' rpm.
An S60 tied to an HT740 and the old 3.7 gearing won't give you much different fuel mileage, cuz she's still having to spin up at 2000 rpm, where she gets LOUSY fuel mileage.
Some fleets made that engine/gearing choice early on.... oops.
happy coaching!
buswarrior
Jack; I am set on 550 hp I have been up to 625 hp any honest trucking outfit will tell you they are getting around 5 from the 60S it was different several years back before the EGR engines (mine is non EGR).Kyle you are right on about the gearing mine are too high (3.73) for the 8 speed Cat CX 35 transmission it needs to be in the 4.56 range.Jack I have read to many print outs from 60 series and know they get around 5 to 6 average for the 14L what do you average on your 50S with a 740 and the Eagle gearing I would venture to say 7 to 7.5 the Greyhounds with that setup got about 6 to 7 mpg according to readout and a 500 hp 8v92 DDEC will do the same at 1400 to 1800 rpms all day and all year long have a great day
makemineatwostroke> What are the mileage numbers that you have seen for 500HP 12.7ltr S60? And BTW, sorry for asking what is your first name? I owe you a Thanks on a previous thread!
I am getting 6.8 to 7.2 mpg, depending on how hard I push it.
Quote from: blue_goose on December 01, 2008, 01:49:42 PM
There is a problem with your engine if you don't get more MPG with the series 60 than you did with the 8v92. Any 4 cycle engine that is set up like it should be will get better milage that a 2 cycle when running at the same power and speed.
Jack
Another common belief that is not true. People in this thread have already shown that their own experience disproves this belief. And like Uncle Ned says, I have Don nearby and all of my experience comes from what I have seen from engines he has built or tuned. I have not seen anyone on this board with a 4 stroke getting the mileage he gets out of his 8V92, and this while towing his 1 ton dually. 4 strokes are great for bragging rights, but a good 2 stroke done right can be just as dependable and even more economical... Not to mention a heckuva lot less expensive!
Songman
Any one that knows anything about flow through a engine should look a dons pistons and liners compared to detroits.
Just wish i had meet him sooner before i replaced the ones in my 6v92
uncle ned
Answer to fuel MPG for my Eagle.
I have driven my Eagle 186,000 miles in the past 23 years. When I bought the bus I rebuilt the 8v71 to a 318. In 106,000with the 8v71 and a 3.76 rear I got about 6.5 MPG. 68,000 miles with the 8V92 and a 3.36 rear about 5 MPG. Now with the series 50 for the 12,000 miles that I have put on the coach I am getting a true 7.7 MPG. Allison 740 for all 3 engines and the coach weight is about 39,000 lbs.
Jack
I have a Series 60 engine and a B500 tranny in my bus. Gear ratio is 4.10. My Series 60 is factory installed.
I got an honest 7.72 MPG on a 4,000 mile trip crossing the Rockies this fall. The MPG included some 40 hours of generator time too. The bus was filled at the same pump at the beginning and end of the trip. The fuel tank design is such that it is easy to fill the same every time.
The bus was loaded pretty heavy with the bays jammed full and nine people inside with a small 500 pound trailer attached. Weight is 37,500 lbs without passengers or cargo.
If your Dina is like the ones that I have driven it is only set up for 5 speed. With the 4.10 rear you could reprogram the B500 to a six speed and get even better than you are now. I put a series 50 in my son's bus and it has the world 6 speed with a 4.10 rear and dose great.
Guys, compair apples to apples hp has to have fuel I get 7-to 7.5 on my 8v92 set at 435 hp up it to 475hp drops downs 5.5 to 6 mpg with 3.36 gears my bus weighs in at 41,000 lbs I could do better when I have time and go see Don and get the air and fuel ratio right.
Not a thing wrong with the 2 stroke I had a new C15 Cat to install in my bus but passed because of the expense and after research found out the mileage was going to be less.I don't know what the hp on Jack's series 50 is most are 320 hp you see a few at 350 hp and Belferts Dina all I have seen are 11.1L and around 365 hp. remember a Clydesdale eats more than a Shetland. I know a guy that has a series 50 in his 01 Eagle and he struggles here in the West in the mountains good luck
Don gets close to 9 out of his 8V92 pulling his dually. So I will say again that I have not seen anyone with a 4 stroke on this board getting close to what Don gets out of his 8V92. He does have a 6-speed so obviously that helps some but the fact is that his engine is set up right. We've got his engine out of the bus right now doing more things to it so his mileage will probably go up even more!
I am not trying to sell anyone on one engine over another. Just responding to the myths about 2 strokes vs. 4 strokes. Detroit 71 and 92s can be clean engines. They can be strong engines. And they can be efficient engines. And in almost every case where that is what your bus came with, it is the least expensive engine. (ie - If your bus came with a S60 obviously putting in a 2 stroke would not be the least expensive answer.)
If you think the answer to Don's mileage is the transmission, I submit that in that case it would still be cheaper to just upgrade your trans that it would be to totally redo your bus to install the 4 stroke. Not saying that the trans is what gives him the mileage, just that some might think that is the difference.
Like I said originally, I am pulling my 6V92 in favor of an 8V71T. The 6V just doesn't have the power or torque that I want in my Eagle. Going to the 8V will allow me to not have to run wide open all the time and it will be better for my engine plus give me better economy. If I can find a 6-speed I can afford I will put that in at the same time. If not I'll keep the 748.
I think some have mentioned above, the best engine for your bus is the one that is working! Fuel economy, cost of upgrades, bragging rights... those are all extras that can come down the road. With the economy on shaky ground, I would feel much better just rebuilding my current engine, no matter what it is, than I would trying to lay out the huge expenditures of changing to something different. From what I have seen, any small gains that someone might think they see by changing from a 2 stroke to a 4 stroke will never recoup the money put into the swap.
With my original engine (8V-71N set at 318hp) with the V730 and 4.56 rear end, I got 4.5-5.5 mpg (summertime driving with the gen running). Now with the 8V-71TATAAC (Turbocharged Air To Air Aftercooled), this last August went on a 1200 mile loop in California from L.A. to Mammoth, Carson City and Virginia City Nv, Lake Tahoe, Sacramento, San Francisco and home and averaged 6.2 mpg with the gen running alot of the time since in 12 days only was in an RV park only 2 nights. While the fuel mileage is not a big jump, what is the big jump up is the performance. Especially on this trip with some passes near the 9,000ft mark, and didn't have any smoking or slow downs in the hills.
Rebuilding your 8V-71 into a turbocharged engine and changing the transmission to a World 5 or 6 spd (can be programmed a 4 spd [gears of which are almost identical to the HT740] a 5 spd [.74 overdrive] or a 6spd [.64 overdirve]), you'll get close to the 4 stroke economy and exactly to the 4 stroke in power.
When I had my Kenworth with the 8V-92TA in it, I regularly out pulled Cummins and Caterpillar 400's-much to the amazement of their owners.
Personally-my only real concern with the 2 strokers, is finding qualified mechanics on the road that still know how to work on them. If I could take Don Fairchild with me, I wouldn't have the worries. This is one of the big reasons I am converting my truck into a motorhome. The Caterpillar 3406B mechanical engine is still being made by Caterpillar under the model name of 3406C, and most any mechanic knows how to work on them.
The biggest factor to fuel mileage is how you drive your bus within the gearing it has. If you go down the road at 2300rpm at the 76mph with a 3.73 ratio and direct top gear transmission, you're not going to get the fuel mileage that you would at a leisurely 55 mph. In fact the difference could be over 2 mpg between 55 and 75 mph. Sean with his giant Neoplan only cruises at 55mph, 50mph on secondary roads. Besides, aren't we out here to see the sites? I cruise at 58mph which is right at 1850 rpm, that is an easy speed to keep all day long. Good Luck, TomC
Kyle,
What is a "Smoke Turbo"? I'd love a little more snoose out of my 8V71 72N without going crazy on the modifications.
Fred
My definition of a 'smoke' turbo is one that adds a small boost (~5psi) to the intake air pressure to overcome the altitude sickness that a normally aspirated motor suffers at higher elevations.
It's purpose isn't to add much power, but to mnimize the effects of thin air at altitude - hence reduced smoke in the mountains.
Oh. Having run mine through a few mountain passes I can recognize the benefit. The 871 gets pretty gutless up there. Although in 1st gear at 2100 it handles anything we've thrown at it! ;)
Fred
Zeroclearnce; the 12.7 when set at 500 hp will get about the same mileage or less than the 14L 515 hp, depending on your serial number it may cost big bucks to get the 500 hp. I like the 470 hp on the 12.7 for fuel and torque.Is your engine a DDEC 111 or 1V and thanks again for help with the TV I have since gone to 76 inch screen what a difference. have a great evening and the name is Cole
Hello again!
I have shared the info from the post that I ask pertaining to the ENGINE QUESTION! to my friend who ask me to.
I'm at a loss of words for all of the replies. I personally would like to thank each and everyone of you for your post.
Being new to this also, I have learned alot myself and I appreciate taking your time to answer the questions.
Thanks a million!
Steve 5B.......
work = torque = mass x stroke - it's all in the math -FWIW
Re: "smoke turbo, 5 psi".
I installed a turbo on my 4-71 a couple years ago. It gives me about 12 psi. The only mod so far is new oil seals in the blower to sustain the bigger boost pressure. Very noticable power and torque increase. Well worth doing. I now go up hills one gear higher than before. (5 speed Spicer).
The 2 stroke DD is a tough, robust engine, and you don't need to go to "turbo specs" unless you're doing a rebuild anyway. As a matter of fact, several Detroit mechanics have told me they don't use the lower compression turbo pistons because it makes the engine hard to start at altitude.
Turbo-ing a DD 2 stroke is a lot easier and cheaper than an engine swap, with great results.
JC
I also used the high compression pistons. Don pulled one piston to make sure it had the tight piston rings, and since it called for transit bus rings, they were the tight rings-as compared to the looser rings for highway trucks. I'm getting about 15psi with the addition of the bypass blower (valve and passage that opens at 5psi boost to route some of the air around the blower to equalize the pressure on both sides of the blower so to make the blower basically freewheel when under power). Haven't had any problems with the engine-have put on about 10,000 miles since the changeover. Highly recommend turbocharging the 8V-71's-it REALLY wakes them up. Good Luck, TomC
Yeah what HE said! All of the above, and so on!
OK Dale, not trying to take anything away from Don's beautiful coach, and especially his talents. But my memory of his coach is sorta fuzzy since I was on the go most of what time he was here. And he left in a hurry after his dually got run over twice by the same guy on Sunday morning. But what is the weight of his coach? And honestly I really can't remember if it is a 2 or 3 axle coach. Now while I realize and admit his choice of toad is quite a bit heavier and has more rolling resistance than the typical toad. The size, weight & # of axles (rolling resistance) will effect fuel mileage too!
Now that said the first SETRA we owned # 702 aka "HOTROD BUS" w 8V92TA DDEC / HT748 @ 500+/-HP. Never ever, ever, ever, ever got more than than 6mpg with A/C off and cruising leisurely along behind dad @ 60-62 mph heading down to KATRIA RELIEF EFFORTS (very flat ground or pretty much)! Or anytime dad drove it it got between 5-6.5mpg. When I let 'er roll with it on the open road I usually got between 4.5 & 5.5 mpg! As well as quite a bit of oil consumption, about a gallon +/- per 1000 miles(depending on how hard I really pushed it!)!
Now the guy we sold it too drove it home from our place to his in North Central (Fiddletown), CA. AT 55 MPH! After he got home he called us and was tickled he got 7.5 mpg and only used 1 gallon of oil!
FWIW ;D BK ;D
BK; like clifford said apples to apples run a b500 behind the DDEC V892 500 hp and mileage will be about the same as the 60 series 500 hp with the same gearing
have a great day
Quote from: blue_goose on December 02, 2008, 05:44:42 AM
If your Dina is like the ones that I have driven it is only set up for 5 speed. With the 4.10 rear you could reprogram the B500 to a six speed and get even better than you are now. I put a series 50 in my son's bus and it has the world 6 speed with a 4.10 rear and dose great.
Allison basically refuses to change the parameters on my B500 to turn on the 6th gear. They will do it only for I think $600+ and a letter from an engineer at the OEM authorizing the change. The letter is the killer plus $600 will buy a fair amount of fuel.
MCI has two of the original Dina engineers on staff and I talked to them about unlocking the 6th gear. They said the 6th gear is locked out because they claim the engine RPM will drop too low causing the computer to downshift to 5th anyhow. I'm not sure I believe them, but don't know what the minimum RPM is either.
Is there a third party that could unlock 6th gear?
Belfert; you might find a independent Allison like Industrial to unlock 6th gear but if you don't have the 4.56 or lower most will not. I know Stewart and Stevenson won't and 6th being locked out is not only Dina, Prevost did for years have a great day
I am guessing that if I had a 4.56 or lwer gear and 6th gear on the tranny enabled my MPG would probably be about the same as with only 5th and 4.10 gears.
What gearing do newer bueses with all 6 gears enabled have?
Belfert; All I saw are 4.56 down to 4.88 with the B500 a few years back some tried 4.33 with no luck
have a great day
You have all the power that you need to get into 6th gear with your series 60. Call TKT Sales and talk to Ted about the 6th gear. He has the motorhome program and will reprogram it for a lot less than Detroit. The one that I did for my son with a series 50 we used a 4.10 rear and a six speed . He is getting over 8 MPG and it stays in the 6th gear.
Jack
Forgot to give you the phone number for TKT
1-800-997-4TKT
Jack
The thing about getting into 6th gear, is because it is a double overdrive, Allison doesn't allow the engine any lower than 1400rpm. When it reaches 1400rpm in 6th it will down shift into 5th. Once in 5th, it can lug down as low as 1100rpm under partial throttle. With 4.1 gearing, you'd have to be at 75mph before it would even shift into 6th, then it would down shift at 66mph. Actually, if you are a fast driver, it should be able to handle it-as long as you have the 4.1 ratio with 12R-22.5 rubber (485rpm). Good Luck, TomC
For fuel economy, we've been driving right around 1500 RPM which is 64 to 65 MPH per my GPS.
From TomC's reply it would sounds like 6th gear wouldn't really help. The cost of the reprogramming would likely take a while to recover if ever.
My ISM @ 1450 ft/lbs torque will allow me to pull 1170 rpm @ 60 mph with no problem. Sure, on a steep grade I need to down shift out of overdrive, but it has no problem carrying that speed in overdrive on level ground unless I have a large head wind. What is it about the B500 that makes doing this on Brian E's bus impractical?
BD-that works since you have an Autoshift. Allison won't allow 6th gear to go below 1400rpm since it is a double overdrive. Good Luck, TomC
Quote from: TomC on December 04, 2008, 01:31:01 PM
BD-that works since you have an Autoshift. Allison won't allow 6th gear to go below 1400rpm since it is a double overdrive. Good Luck, TomC
Technically, what is it about the double overdrive that makes Allison want to keep rpms above 1400?
BD- It's just what I have found out driving the World transmission, it will not lug down below 1400rpm in 6th-but every other gear will. Just the way they have them programmed. Good Luck, TomC
BD; when the B 500 or the 4070 are in the overdrive the output shaft speed has to be greater than turbine shaft speed and if that is not accomplished it will down shift., with 4.56 gear 1400 rpm would be about right have a great day