I have been wanting to ask this question for a long time.I have a non turbo 8-71 four speed manual in a 1978 -5B. Some times a little more horse power would be really nice. My engine has been completely rebuilt. Adv. timing with N65 injectors. Crank is still standard, two piece pistons, new cams, rebuilt heads and all new bearings everywhere. I have no oil leaks and engine uses very little oil. Starts immediately and no smoke. 310 hours since overhaul. With no mountains involved as in B.C. where our daughter lives I get at least 9mpg at 60-65 mph.(1750 rpm). When the rebuilt heads where installed I remember the letters N/T was written with a metal marker on the inside of the head. Does that mean there is a difference between turbo and non turbo head? I believe my engine to be very healthy. If my engine will handle a turbo, I would consider start looking for a turboed 8-71 in a bus that is headed for recyle with automatic tran. I would not be looking for a good engine just parts-- turbo , exhaust piping, larger rads, and all parts from gear train cover to auto trans. end. I think a MC-9 would work.
The biggest mistake i made during my conversion was that when I raised the roof 6" I should have raised the rads , cooling fans and gear box drive for fans with roof. The engine compartment in a 5B is very full now. I would likely need to raise all pieces that 6" to add a turbo. and still have room to do maintenance. This tight space is even more noticable after adding jakes as I recently did.
Anyway i am just looking for thoughts if this is possible or should I consider other options? First thing I need to know is will my engine handle a turbo without major changes to engine? If that part is possible I definately got lot more questions. Thanks
LarryB
You can read my article in the Projects section on how I put a turbo 8V-71 in my MC-5C. I'll add a few pictures to this post as well. Issues are it's almost impossible to put a turbo on top of the engine, in the "normal" place, with the MC-5 engine bay. Mine is hung off the driver's side. I made my own intake and exhaust plumbing to put it there. As far as converting your engine,advanced timing is a little aggressive for a high compression turbo engine. All the factory turbo engines have standard timing, because of the higher combustion pressures from the turbo. It's possible to put a turbo on a high compression engine but it should be a boost limited turbo with a waste gate, to limit maximum boost. It sure can be done, but it's not the work of a weekend. You need to know what pistons you have - some can take some boost, some can not. Don Fairchild did a turbo 8V-71 for Tom C with high compression pistons. I can tell you 400 hp (N80 injectors in a 8V-71T) is a little smokey but flat out runs in a 5C...
Brian
Edit: fixed Don's name, sorry about that!
That's Don Fairchild not Sheppard he will get for that Brian just buy a 6v92 a lot easier up grade with a little more power and torque
Does my heart good to see some one else playing with the Turbo & the 71 engines, did notice the lack of oil cooler/oil filter. Assume that is not an issue, just enjoying my old games with the 8V & 12V babes, never played the 6V-71 but the 6V, 8V & 12V-92 are good make you happy engines. And whole hearted agree using the 6V-92 in the -5 MCI at 450 hp would be a nice go getter.
Remember this is no such thing as too much hp to a point, 850-900 12V-71TT is over board for sure in the MC7, but was fun playing/learning. The best part was the MC7 frame took the big power & weight of the 12V-71, no issues, am told the MC8 & 9 do not have the structure for that game. I felt the MC7 was designed for the possibility of using the 12V being right after the MC6, no idea nor facts on that.
Dave M
Dave, good catch, I installed the oil cooler and oil filter from the bus engine somewhat later. You can see the oil cooler in the second photo. It was a long process to clean all the old gasket material from the cooler, and it all needed to be perfect, as you know. The turbo engine, coming from a military tank (actually a self propelled howitzer) as it did had a very large double cannister cooler for the automatic transmission in the military chassis. As I mentioned in my article in the Project's page, about the only thing that I used from the military engine was the long block and blower. Most everything else I changed, including the oil cooler!
Brian
Brian,
Your project just brings back many memories, all happy and smiling. The single biggest surprise I had was installing the 12V in the MC7, when it was all clamped down on the slides, it was very clear abut the clearance around the engine & body structure, it just cleared the bell housing, air intake so perfectly, I laughed with relief. the next issue was finding the short drive shaft configuration, with the RTO-910, the drive shaft with slip joint had to be 9.5" center of U Joint to U Joint with the slip joint in mid position. Looked crazy, the total slide was about 2.5" and the splines were also about 2" length with the outside diameter of about 7", with such a short shaft, they had to go larger diameter to get enough strength in that driveshaft, like said, the learning process was non stop, but mucho fun.
Dave M
The quick additional answer to your question is YES and NO. One can just add a Turbo with NO other engine or accessory changes. The turbo will make boost and it will clean up the exhaust ... but that is about all it will do. Mounting the wrong turbo on a normally non turbo charged engine MAY damage the engine. Wrong components at odds.
A pure Factory Turbo Detroit Diesel 2 stroke engine is a different animal. Practically everything is different, including the crank, block, rods, pistons, heads, valves, cams, blower, seals, water pump, injectors, coolers, oil pump, etc., etc.. You MAY have the WRONG pistons in your existing engine NOW if you have no turbo.
Or ... there is a third position or option that uses ideas and components from both the above. Kinda a hybrid turbo engine using some stuff that will not hurt but will kinda help with power and smoke and would be a half way measure building a true turbo engine. 2 stroke Detroits are strange old beasts with weird ways of doing things.
It would be easier and cheaper to just fine a proper turbo 2 stroke Detroit Diesel engine from the get go. But ... it might be cheaper yet just to drive what you have, even though you may have the wrong pistons in the engine. You MAY have turbo pistons. But ... the engine will run kinda OK as is. Hope this helps kinda. HB of CJ (old coot)
The 8V71 is 318 HP depending on injectors,the V series with a turbo were 350 HP engines,the heads injectors and timing are different,you might be able to put a small turbo on it but I doubt you'd gain much,you could always go up one size on your injectors.
I lucked out with my 8V-71N in that it had the tight transit bus rings rather than the loose truck rings in it. On my transit bus, we changed the N65 injectors (300hp and 800lb/ft torque) to 7G75 injectors (375hp and 1125lb/ft torque). I did not change anything in the engine. Changed the Blower to a bypass, added fuel modulator, used a Series 60 12.7 liter turbocharger with waste gate to keep boost around 15psi since I kept the high compression two piece pistons, added air to air intercooler, additional electric fan cooled trans cooler, bigger air cleaner, recored radiator to the biggest I could but still needs misters on the hottest of days, and changed the muffler to turbo muffler.
I can tell you it REALLY woke up the 8V-71. Before, when towing my car, going from L.A. to Las Vegas, there would be several smallish hills I'd have to down shift on. Now only the big hills of Cajon and Baker I need to down shift.
Also-used to pull south bound Grapevine at 32mph (just the bus) now pull it at 45mph.
I get the same fuel mileage, but now have much more power and except for initial smoke at first, doesn't smoke at altitude. Good Luck, TomC
For gods sake, you have the perfect example of a good 8V71 that most folks would kill for. Leave it alone and enjoy a rare Detroit that you don't have to screw with.>>>Dan ( There is NO SUBSTITUTE for RELIABILITY)( The trick to getting the most out of an "A" timed engine is RPMs, don't let it fall below 1700 Rs when pulling a grade.)
Thank you all for your replies. Now I can stop quessing what the answer to my turbo question.
Brian - read your article several times. In fact i have read the all replies in this post several times. Thanks for posting the pictures, that cleared up a lots of thing on how you made adding a turbo to a MC-5 without lifting the rads,fans, etc. Looks really good.
HB- you mentioned I may have the wrong pistons . I found the old bill today and will go to Waterous ( now Wajax) for an exact description of what piston I do have by the part # Will get back for more advice likely. You and a couple other mention about helping to clean up my exhaust. If by that you mean to get rid of black smoke--- my bus will not make black smoke. I have never seen black smoke in my rear view, no matter how hard you try and drive it.
Tom --what you are talking about is beyond my mechanical ability without it been written in a book that I can follow step by step, (like Detroit manual). Once you start mixing and matching parts from different engines and knowing the limits of how far each can be pushed, I would be lost.
Claimjumper you are likely right enjoy what I got, it seems to be reliable. I need a project for next winter so i had to ask the question about a turbo. It is not that under powered just a few more ponies would have been nice.
Please let me know about this exhaust issue and the fact my engine will not make black smoke. Thanks
Larry B
One thing that might be overlooked; any horsepower boost will fall clear to the bottom line in output. Most of the engine's power is spent overcoming the load that is the bus.
If the bus engine produces just 100 horsepower more than needed to climb a given grade, another 50 horsepower will give a full 50% increase in acceleration. If you once have that extra performance, you likely won't want to give it up, even if it costs you some fuel.
For what it's worth.
Tom Caffrey
If you're not smoking under full load on a hill, all that means is that you're not over-fueling the engine so you are keeping the rpm up where it wants to be, running in the right gear, and so on. Plus the engine is tight, you have all the compression you are supposed to have, your intake and exhaust are passing the amount of air they should. If you want, try N70's, they will give you some more fuel, add about 25 hp and you should smoke up hills like a trucker! ;D
Brian
Any of you guys ever saw the option of cams for these old engines I am not much up on cams for the V71 series but I bet a Coke there are 20 or more the last time I counted there was over 30 for the 92 series
There is more to it than just changing injectors sometimes a larger injector will actually drop the HP when you get the exhaust temps right that is about as good as it gets for performance and power
Then keep in mind hp ratings are at sea level in those old engines that is why they were such a good marine engine
Quote from: bevans6 on December 27, 2014, 03:58:11 AM
If you're not smoking under full load on a hill, all that means is that you're not over-fueling the engine so you are keeping the rpm up where it wants to be, running in the right gear, and so on. Plus the engine is tight, you have all the compression you are supposed to have, your intake and exhaust are passing the amount of air they should. If you want, try N70's, they will give you some more fuel, add about 25 hp and you should smoke up hills like a trucker! ;D
Brian
Speaking of truckers blownin' smoke up the hills....... There's a local marine Detroit mechanic here in CT. He's super hard to find, I had heard about him for years but could never find him. By chance, I finally found him and convinced him to do some work on my 8V71N while it was out of the cradle (he hates working on trucks and flat out said NO WAY when I asked him to work on my 4106 but agreed when I told him the engine was out). The only thing this guy works on are 2 stroke DDs. Period. When discussing which injectors to install he swore that the best performance/fuel economy for a 8V71N was had by installing N70 injectors, standard timing, and propane injection, 2400 rpm. He claims 350hp and no smoke in the hills when using propane. He said he did hundreds back in the 70s and this was best setup he'd seen. I chickened out and went N65s A-timed for fear of smoking too much. Like you, it's completely impossible for my bus to smoke under any condition, which makes me think that I should have gone with the N70s. I still plan to add the propane but it's not clear how much HP that will add with N65s.
By the way, this guy has framed pictures of engines that he's built hanging in his shop! His favorite was a quad turbo 12V71 making around 2000hp he built it for a trucker. He said the trucker wanted to go 85mph on flat roads, down hills, up hills, no matter, 85mph. It got 3.5 to 4 mpg! This trucker, as it was told to me, was able to get another delivery or haul back on his daily run, thus he justified the lower fuel economy/higher hp, saying he was still ahead of the game. I think this was in the late 60's or early 70's.
The N70 with the right setting was a true 318 hp not the 304 hp it was a fire truck setup, but there you go one has to have the right cams,blower and liner port height or they smoke like a train
We had N90 injectors in our old fire apparatus. "N" pistons, no turbo. Governed speed was about 2500. The master mechanic told us not to run over 2100 continuously. We also had to learn to keep our foot out of it until the engine spun up. Otherwise the black smoke was simply incredible.
Starting as early as around 1974 the shops began replacing the big injectors with I believe N65s. Smog laws already in California. Do not remember about any throttle delay stuff yet. I helped do it as I thought it was fun. Hardly any mufflers. Long ago and far away. HB of CJ (old coot) :)