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Author Topic: 6v92ta verses 8v92ta  (Read 3478 times)
sledhead
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« on: May 10, 2013, 01:41:14 PM »

I have a chance to buy a rebuilt 8v92ta and a 754cr 5 speed or keep my 6v92ta and put the 754cr on it . I just had my 6v92 set up to 350 hp and it run's great with 9.5 mpg (cdn) is it worth the lower mpg for more hp ? What do you guy's and gal's think            thanks dave
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1990 mci 102c  6v92 ta ht740  kit,living room slide . home base huntsville ontario canada
bevans6
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1980 MCI MC-5C




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« Reply #1 on: May 10, 2013, 01:49:41 PM »

I wouldn't be surprised if they didn't get very similar fuel mileage if driven the same way, but you would have 50hp or so on tap for "emergencies"...

It's a lot of work to change, unless the 8V92 is on an MCI cradle already.

Brian
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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
sledhead
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« Reply #2 on: May 10, 2013, 01:56:14 PM »

The complete unit came out of a 1993 mci , I was told about $1500. re and re plus some misc parts.                  dave
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1990 mci 102c  6v92 ta ht740  kit,living room slide . home base huntsville ontario canada
bevans6
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« Reply #3 on: May 10, 2013, 03:38:27 PM »

If I thought the engine was good I'd do it in a heartbeat.  Ain't no prize for going slow...

If I still lived in Ontario I'd take a weekend and cruise on up for a visit.  Opportunity missed, I fear...

Brian
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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
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« Reply #4 on: May 10, 2013, 03:46:21 PM »

The 8v92 and 754Cr is a nice setup if you don't want it I know some one that does he pay you a finders fee hard to pass up a extra 125 hp lol with 1400+ lbs of torque, yours a newly rebuilt 6v92 which will serve you well for years I doubt I would do it but we all do strange things
« Last Edit: May 10, 2013, 03:50:50 PM by luvrbus » Logged

Life is short drink the good wine first
RickB
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81 MCI 9 smooth side 8V71 Allison 754




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« Reply #5 on: May 10, 2013, 03:49:07 PM »

Clifford

I hope you're thinking of me when you say you know someone looking. I'd sure love to buy that combo if you decide not to.

Keep us informed

Rick
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I will drive my Detroit hard... I will drive my Detroit hard.
luvrbus
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« Reply #6 on: May 10, 2013, 03:51:58 PM »

I was Ricky lol

good luck
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lvmci
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« Reply #7 on: May 10, 2013, 06:11:59 PM »

I'm having daydreams of a 500hp 8V92 in my 5A, passing sport cars going up Cajon Pass in the fast lane, lvmci...
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Mci 102C3 8V92, Allison 4 speed 740
Formally MCI5A 8V71 Allison MT643
Utahclaimjumper
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« Reply #8 on: May 10, 2013, 06:50:43 PM »

That's not a "daydream" that's an hallucination!!>>>Dan
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Utahclaimjumper 
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akroyaleagle
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« Reply #9 on: May 10, 2013, 06:58:43 PM »

I went from a good 8v71N to a reliabilt 525hp 8V92TA. My fuel mileage is the same.

May be in how you drive.
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Joe Laird
'78 Eagle
Huron, South Dakota
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« Reply #10 on: May 11, 2013, 02:27:56 AM »

Anyone with the 8V-92 @ a high hp running #40 oil, spin the rear main bearing YET?  Prime reason I only ran the #50 oil in my crazy 8V-92 setups, no issues, but the outfits running the #40 are legend for rear main issues.  Just wondering as I also prefer the 8V, but most know why the bus outfits went with the 6V, lack of rear main issues, more miles per rebuild, yes we all have a buddy who is married to the sister of the  mechanic who always gets 2 mil miles from the 8V-92, right ?  Grin

Dave M
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MCI7 20+ Yrs
Foretravel w/ISM500
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Central Virginia
sledhead
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« Reply #11 on: May 11, 2013, 05:20:56 AM »

Now It's clear as mud .   With what I have now at 65mph my tack is 1700 rpm and this is usually the speed I set the cruise at. With the 5 speed I know the final drive is 1 / 1 but to have the extra gear between 3rd and 4th would be all I need to make the set up almost perfect.
Now after driving the 6v92 with little power for the last 6 years. But now with the ddec change with the 350 hp or more  the drive is very relaxing. With the 8v92 I know there will be more power still. But how about the eng heat and reliability and mpg ?      again thanks dave
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1990 mci 102c  6v92 ta ht740  kit,living room slide . home base huntsville ontario canada
luvrbus
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« Reply #12 on: May 11, 2013, 05:52:15 AM »

MCI had great success with the 8v92TA set at 400 hp lots of those still on the road IMO the 8v92 is more durable than a 6v92 a 400 hp 8v92 will do as good if not better on the mileage as a 350 hp 6v92 DDEC or mechanical 

I still would keep your 6v92 with a fresh rebuild over a unknown 6v or 8v the main bearing on a 8v92 has never been a problem for me using 40W oil I guess things could happen
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akroyaleagle
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« Reply #13 on: May 11, 2013, 06:55:52 AM »

I am not a fuel engineer!
I do have a lot of miles in my coach wit the 8V71n, also the 8V92TA. I know what the fuel mileage is. I have kept a record
for 17 years.

If the rearend does 65mph at 1700, it doesn't care what is driving it. It will be the same speed at any HP at 1700rpm, even if a hampster in a cage wheel is powering it.

It takes the same HP to move the coach at the same speed. It is very nice to have extra HP when climbing. With mine, I can blow right past the trucks on climbs.

It uses more HP now when climbing but the time is much shorter. I think it balances out.

I believe if you hot rod a detroit it will not last long. Reliabilt set mine up and I drive it no different than the 8V71.

I also believe the guys that tell you to slam your finger in the door then take it out on the engine never bought the engines.

My 71 was like the rest of them, it ran better at 1800 or above. The 92 seems to really like lower RPMS. It acts like the series 60.
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Joe Laird
'78 Eagle
Huron, South Dakota
Geoff
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« Reply #14 on: May 11, 2013, 06:18:03 PM »

I have heard from a lot of people that they get 5-6 mpg with an 8V92TA.  Then 7-8 mpg with the 6V92TA.

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Geoff
'82 RTS AZ
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