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Author Topic: turbo  (Read 2357 times)
mikke60
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« on: March 16, 2012, 07:33:48 PM »

looking for input on cost , difficulty, and reality of installing  turbo charger on  my 8 71? mike
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TomC
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« Reply #1 on: March 16, 2012, 09:52:27 PM »

Depends how crazy you want to get.  You could do it the cheap way and just use N65 injectors and add a "smoke" turbo that puts out about 5psi-that will maintain horsepower at altitude and add a bit more power.
Or you could do what I did.  I had a custom air to air intercooler made that mounts in front of the radiator.  Then had Don Fairchild do all the installation of the Series 60 12.7 turbo with waste gate and 7G75 injectors (now have 375hp and 1150lb/ft torque), changed the blower to a bypass blower, and installed a fuel modulator to cut down on smoke at acceleration.  I ultimately had to change the muffler to a turbo muffler, increase the air cleaner from a 6" to 7", increased the radiator to the largest core-although not enough-still have to use misters, added a air to oil trans cooler with thermostatically controlled electric fan, installed two vents in the rear engine door.  Compared to the naturally aspirated engine, the turbocharger REALLY wakes up a 8V-71.  While I'm getting about the same mileage, my performance is drastically different. I spent about $13,000.00 total.  Now it's enjoyable to drive.  Good Luck, TomC
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Tom & Donna Christman. '77 AMGeneral 10240B; 8V-71TATAIC V730.
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« Reply #2 on: March 17, 2012, 12:52:19 AM »

HP is a wonderful thing, however if your looking for a long term turbo version, there are some parts that most likely need changed provided you have a late model blosk, parts like cross bolt pistons, turbo ex valves to name a few little items.
Having played the game with the 12V71 non turbo and then change over to the turbo version was not cheap, yes sure did run on the wild side.
Would not just bolt a turbo on a 8V-71 without much readeing and digging for info, nearly forgot the pistons need changed too, no end nor cost for the toys.  But lots of fun.
dave
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bevans6
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« Reply #3 on: March 17, 2012, 04:27:06 AM »

I went a slightly different route, my project is detailed in the Project section of the board.  I installed a NOS Military rebuilt 8V-71T in my MC-5C.  I finished late last year, just starting now with the early spring weather to do the final steps before a test drive.  So far it's acting like a very happy engine.  Mine is set up for 400 hp gross, around 350 hp net I expect, with N80 injectors which are a little larger than typical automotive engine injectors.   It's also set for 2300 rpm.  Quite looking forward to driving it!

Brian
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1980 MCI MC-5C, 8V-71T from a M-110 self propelled howitzer
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TomC
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« Reply #4 on: March 17, 2012, 08:26:58 AM »

One more note-before starting the project, Don Fairchild pulled one of the pistons to see if they had the correct rings, and I lucked out that transit buses uses the "tight" rings for less oil consumption, and that are turboable.  Even though the compression is at 18.7 to one rather then the 17 to one for turbo pistons, the 12.7 Series 60 turbo keeps the boost to around 15psi.  The nice thing about the higher compression is it starts easier in cold weather.  Once warmed up, going up hills and in altitude, no visible exhaust is seen-I have an up exhaust that I can see from the driver's seat.  Good Luck, TomC
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Tom & Donna Christman. '77 AMGeneral 10240B; 8V-71TATAIC V730.
Geoff
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« Reply #5 on: March 17, 2012, 08:30:40 AM »

In my opinion, changing over to a MUI 6V92TA is the best choice.  350HP, 1080 ft lbs of torque is standard output for highway use, and puts no stress on the engine like retrofitting a turbo to a non-turbo engine.  Plus you can get 8mpg as the 6V92TA is more fuel efficient.  The biggest problem is locating one that doesn't need a lot of work and having a Detroit mechanic than can make sure you put in a good engine.

--Geoff
'82 RTS AZ
6V92TA 350HP 4:10 gears

P.S.  I also think the 6V92TA is the cheaper alternative, unless you just slap a turbo and big injectors in you 8V71 with no other changes.
« Last Edit: March 17, 2012, 08:38:58 AM by Geoff » Logged

Geoff
'82 RTS AZ
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« Reply #6 on: March 17, 2012, 08:35:42 AM »

As a comparable, I put a turbo on my 4-71 a few years ago. All I did at first was install a bigger, 7" exhaust to match the turbo outlet. And a 7" in and out muffler that was quite free flowing: I could see right though it. I kept the oil bath air filter just to prove the nay-sayers wrong. The younger mechanics were telling me it would suck the oil out of it through the turbo. The old 2 stroke mechs were telling me it would work. And it did quite well. I drove it the first summer like that, around 10 to 15000 miles.

The following winter, I did a complete overhaul and rebuilt it to turbo specs. Had the head redone with the turbo rated valves and replaced the N65s with 75 injectors (I forget the exact description of them), put in new cross-head pistons, liners, front and rear seals, crank and rod bearings, and I forget what else. Set it to advanced timing. Replaced the oil bath with a big dry filter off a highway truck.

Like TomC says, it really wakes it up. I go up hill one gear higher now with the 5 speed Spicer. It makes about 15 psi of boost at optimum conditions. I went from being underpowered with a line of cars behind me, to keeping up to traffic like most transport trucks.

Well worth the time and effort, and probably easier and cheaper than re powering with a different engine.

JC
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JC
Invermere, BC
1977 MC5C, 6V92/HT740
Geoff
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« Reply #7 on: March 17, 2012, 08:50:12 AM »

To make an 8V71N into a factory 8v71T:

Std timing
lower ratio blower drive
different blower seals
Stellite turbo valves
lower compression pistons
remove breather from end plate to block
bigger injectors
breather valve covers

Then you'll need a bigger radiator and air cleaner.

You can skip any of the above but it won't be built to last, plus you don't get an aftercooler unless you have a newer block.

Detroit made 8V71TA's up and past the late 70's, but the popular choice was the 6V92TA with it power and much better fuel milage.
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Geoff
'82 RTS AZ
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« Reply #8 on: March 17, 2012, 09:24:07 AM »

Sucking the oil out of a oil bath filter with a turbo wasn't the problem unless it overfilled it was not enough flow and dirt particles with the turbo trying to pull the air the oil bath wasn't design for 

good luck
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« Reply #9 on: March 17, 2012, 09:31:49 AM »

Part of the difficulty I found, is when researching how to do it, each mechanic you talk to gives different advise. There are valid arguments in favour of high compression versus low compression pistons, standard timing vs adv., injector sizes and specs, what kind of turbo, etc, etc. You have to decide how the engine is going to be used: where in the rpm range do you want the torque, depending on your drive train ratio, whether you want economy, or lots of power if you don't care about fuel mileage, etc.

You have to gather up all that advise and info, and sift through it and decide what setup will be best for you.

The actual work doing the overhaul is not difficult: just do what the DD service manual says.

Good luck,

JC

 
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JC
Invermere, BC
1977 MC5C, 6V92/HT740
TomC
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« Reply #10 on: March 17, 2012, 11:34:51 AM »

The one main reason I stayed with the 8V-71 instead of changing to a 6V-92TA was the 71 series has dry cylinder liners wheras the 92 has wet cylinder liners that can leak when let to sitting for weeks or months on end-especially in cold weather. Not saying that they will, but can leak.  And because of the 71's build-it is much stronger then the 92 series.  My 8V is using all the same equipment that was on it from a non turbo engine.  I did change the blower to a by pass, but didn't change the ratio.  Granted, my fuel mileage would be better if I had changed the valve timing and changed the cylinder liners to turbo (the intake ports are shorter to allow a longer power stroke).  I get 5-6 mpg-mainly because of the big bump in the front from the old sign and only a V730 with 4.56 ratio.  I cruise at 58mph which is 1800rpm.  65mph is 2100rpm which I can do all day if needed.  If I were keeping the bus, I would install a Cummins ISL with Allison 3000 series transmission in T drive-my bus was one of the weird ones that was available in both V drive and T drive configuration.  Santa Monica Bus Lines had some MCI Classics-which are a cousin to my AMGeneral-that I was eyeing to replace with a Detroit Series 50 and Allison 6spd.  But-now spending my money on my truck conversion.  Good Luck, TomC
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Tom & Donna Christman. '77 AMGeneral 10240B; 8V-71TATAIC V730.
Geoff
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« Reply #11 on: March 17, 2012, 05:41:27 PM »

Tom-- The important part of any engine modifiations is that it works for YOU.  We don't drive our buses commerically and look at a business total fleet mpg for the year to maximize profits.  We drive our buses for pleasure and a couple of miles per gallon lost on the road or at a diner, or taking a break at the rest stop at fast idle really doesn't make much difference.  I don't even look at my fuel milage anymore.  Its all part of the trip and I get the greatest pleasure just being able to use my bus!!  Everytime I take it out I feel like King of the Highway.  I love to drive a bus instead of a car or a crappy sticks and staples.

--Geoff
'82 RTS AZ
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Geoff
'82 RTS AZ
TomC
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« Reply #12 on: March 18, 2012, 09:18:26 AM »

Geoff-I fully agree with you-that's the main reason I didn't change out my 8V-71.  I like the sound of the 8V-71-always have.  My fuel mileage is 5-6 depending on if I'm hauling my car behind. Just had new 7G75 injectors installed by Don Fairchild (had to go through 12 injectors to find 8 that worked-including blowing the tip off one-but that's another story [not Don's fault-bad rebuilders]).

I'm going to "The Rally" this next week in Phoenix.  Wondering if you're going-will be at the Phoenix International Raceway since they're expecting around 4,000 RV's.  Good Luck, TomC
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Tom & Donna Christman. '77 AMGeneral 10240B; 8V-71TATAIC V730.
Geoff
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« Reply #13 on: March 19, 2012, 08:08:37 AM »

I'm not planning on a trip to Phoenix, a big crowd is not my thing.

Here is a good deal on a 6V92TA with an Allison 740:

http://www.ebay.com/itm/DETROIT-6V92TA-335-HORSEPOWER-W-ALLISON-HT740D-TRANSMISSION-/130660294767?_trksid=p4340.m185&_trkparms=algo%3DSIC.NPJS%26its%3DI%26itu%3DUA%26otn%3D5%26pmod%3D180839731308%26ps%3D63%26clkid%3D7113055558518218047


--Geoff
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Geoff
'82 RTS AZ
wg4t50
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« Reply #14 on: March 19, 2012, 03:49:42 PM »

Nice in the MCI 5 Series  Grin
Dave
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MCI7 20+ Yrs
Foretravel w/ISM500
WG4T CW for over 50 wpm for ever.
Central Virginia
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