8v92 differences

[preacher57]

I have an 89 MCI with a mechanical 8v92 engine. ( ht740 trans )
It runs OK but it's tired. I am looking at a good used engine for sale that is a 1st gen electronic style.
My question is, are these engines basically the same thing? Can I just bolt-on my older stuff to the new engine and have it work properly?
There are compression ratios, injector sizes, turbos and other things to consider, but I am just scratching the surface of this idea. It seems like a good deal if it will work without having to "fix" every darned thing.
I'm used to old Chevy vehicles where everything bolts up to everything else and works!
I'll keep running my old, tired beast if I have to but the thought of a fresher engine is fun...

[luvrbus]

You don't want a DDEC l that is a 2 box system, a lot of the stuff will bolt up,the internals are different like the camshafts ,the DDEC doesn't have a governor on the blower and the injectors are different, some have different oil pans that use less bolts and different style pan gasket The DDEC has no rack the rest is all about the same unless you are getting a super buy rebuild what you have

[Van]

I have an 89 MCI with a mechanical 8v92 engine. ( ht740 trans )
It runs OK but it's tired.

Just curious but can you describe tired, why not freshen up the mill you have?

[Coach_and_Crown_Guy]

For what you spend on getting the electronic DDEC engine and all it's attendant issues, you could easily just fix your mechanical 6V-92. Believe me when I say the mechanical engine is the one to have for oh so many reasons.

The change to DDEC will involve lots of new wiring and entanglements with the bus systems, the transmission, which may not match well without electronics of it's own to talk to the DDEC, just off the top of my head. Plus lots of wiring between the engine and bus systems, also all the engine air controls will have to be removed, and many other things as well, way too many to list here, it's not trivial to go from mechanical to DDEC.

You need to find an EXPERIENCED and Reputable Detroit 2 stroke mechanic/shop who can diagnose and repair your mechanical engine to the full potential and maybe even better than it was originally designed for. For instance California buses were crippled with all manner of smog, smoke limiting devices that turned them into SLEDS. I've driven them enough to know they feel gutless and slow to accelerate etc, but it's all because of the pollution modifications to the basic engine.

Come to think of it, You may have nothing wrong with your bus except that it's been loaded and crippled by various pollution reducing HELL BORNE devices. You say it's "tired" without details. That's Exactly how a smog crippled 2-stroke feels and drives, but it's designed that way, nothing wrong with the engine. You need better information before spending money on another engine, or even attempting to repair this one if nothing's wrong with it.

A truly "Tired" 2-stroke needing new cylinder kits will be smoking (blue mostly(oil)) all the time and leaking oil from the air box drains and many other places, and it will really Sound Tired. Maybe only someone with an experienced ear can tell the difference but it's usually pretty obvious it's ready for an in-frame with around 4-500k miles usually.

If you only experience sluggish performance issues and the engine sounds good, it's probably Smog crap, ---OR--- maybe even throttle linkage adjustments, FULL Throttle lever travel on the governor itself, you really need to be sure the throttle lever is going all the way to full fuel before assuming the engine is needing repair. This particular problem is not uncommon at all and should be looked at first. One of the advantages of the mechanical is you can see and diagnose problems without having to get involved with electronic code readers and various sensor glitches affecting engine performance. Reliable and repairable is the mechanical.

Deal with the one you already have, the mechanical is the very best choice to have anyway, by far.

More info on where you live and details on the bus and where you got it from would be helpful. If you are in Southern California I can Highly recommend J & R Diesel in Riverside for all things Detroit 2 stroke. They are THE go to place for anyone needing proper 2 stroke repairs. They can tell you if the engine is full of smog crap equipment and what your options might be to improve it's performance.   You're Welcome.

[preacher57]

Thanks for the input guys!
I am in NW Washington state, This bus is a new purchase for me and I got it from a town 115 miles south of me.
It has roughly 400K on the bus, I don't know about the engine.
When I say it's "tired" It runs fine but blows an excessive amount of grey smoke for the first ten or-so minutes and again when you give it the beans for the first mile or so.
I drove it back home the day I bought it and it was really sluggish. From the replies I got with that thread, it seems to be a fuel issue or an airflow or throttle adjustment.
All I have done so far was clean the air filter. I am alone so it's a trick to check throttle movement but I could set my camera there and run up to hit the pedal.
I know it needs maintenance as there are no records for the last ten years.
Oil change is waaay past due as the filter is encased in oily road dirt. It does drip a bit of oil out the tubes even after sitting there idling for 20 minutes it will leave little puddles.
It is very dirty in the engine bay and I am planning on a complete detail as soon as it warms up out here.
I had to install a new oil gauge as the old one read almost zero all the time. ( I was panicked that it had no oil pressure! ) It now reads something reasonable when warm, I don't remember exactly....
Next is to put in an inline fuel pressure gauge but I need to make sure I know the correct place to put it in. Before, in between, or after the two filters/pump.
Of course, before the pump shouldn't be pressure.
I am a decent mechanic and am learning fast about these engines, but completely new to two-stroke diesel. I have watched dozens of youtube videos and can see how they are built and how the cylinders function.
A look at valve adjustments and injectors will be in the near future, but again- It's freezing here and I don't want to pull it apart and leave it that way. Anything I do to it I need to have done and put back to running condition before the sun goes down.
I will ignore this "deal" and work with what I have. Thanks for the advice...
A good cleaning and a tune may get things back, but she was slow up the hills! From what I've seen on the videos, it should roar up the hills a lot better.
there doesn't seem to be any leaks in the exhaust  or intake anywhere.
I'm not interested in jacking it up with bigger injectors or anything. I want it stock as it was on day one.

[freds]

Give it an oil change. A lot ignorant people out there put in multi weight oil when it requires ashless 40wt. My bus smoked a lot until it got it's first correct oil change.

In my case the hint was a lot of 10W40 oil containers in the bus.

About where are you located in WA?

[preacher57]

I currently live in the gigantic metropolis of Sequim, WA

[luvrbus]

The gray smoke is oil burning ,could be as simple as blower or turbo seals which are easy to check,or it could be the oil rings and those are the only rings you cannot check from the inspection covers,the oil rings are not that good on the 2 cycle engine if you over heat the engine the expanders loose their tension and the tiny oil rings break.Pull the inspection covers if the liners have black streaks you are going to need a inframe ,with head work, a inframe kit on your engine will cost you 4 to $5000.00 for after market parts, the bottom end never gives any trouble unless it been run low of oil 

good luck    a

[DoubleEagle]

Clogged fuel filters can drop performance quite a bit. If the oil has been not changed recently, chances are the fuel filters were not either.

[luvrbus]

That is the way it works when a engine needs work people don't service it they run it till they can sell it ,fuel filters and a oil change is not going to help him with the gray smoke and oil coming from the air box drains though ,the engine may have just to much idle time and needs to run ,they will wet stack even on fast idle

[Coach_and_Crown_Guy]

All above are excellent replies and things you should be doing when you can. Straight 40wt oil. DELO 100 is best
DELO 400 in a pinch, several other brands are good too but must be low ash 40wt. Never ever use multi-grade oils.  Change all the filters, Fuel, air, oil, and even really old fuel if contaminated by algae can cause all sorts of trouble. Biocide the fuel and change if possible or at least freshen with new fuel and reduce percentage of contaminated fuel.

Don't expect a 6V-92 to storm up a grade. Not that much torque. Expect to go up most grades at around 30-35mph in second gear. that's very normal. And be sure to watch your engine temp gauge like a hawk. DO NOT overheat a Detroit or you will become well acquainted with your mechanic and incur expensive bills. Get educated on the proper care and driving of a Detroit 2-stroke. It's definitely becoming a lost art and skill-set but it's crucial if you want to enjoy many years of happy driving. The 6V-92 puts out slightly more power than the 8V-71 did but in a slightly smaller package. They also put out more heat into the coolant so overheating is usually a constant concern.

[luvrbus]

He has a 8v92 it should pull ok

[Ed Hackenbruch]

Use fast idle when not driving. Best to drive it for a half hour or so. My first summer with the bus we spent in an rv park where once a week i fired it up and drove a few hundred feet to the dump station. When we left in the fall we had a huge cloud of smoke behind us for the first couple of miles until it warmed up and burned off the fuel/oil that had built up in the cylinders. After that we never had it happen again because i always drove it around after idling for any time.

[Coach_and_Crown_Guy]

Oops. I missed that it was an 8V-92. I assumed the 6V since that was the predominate engine used in most buses at the time to replace the 8V-71. I suspect that MCI put in the 8V-92 since it was the same size as the 8V-71 and gained a LOT of extra power and performance.....seemed like a good idea at the time.

But with more experience it became pretty obvious that the MCI-102x3 twin side radiators weren't up to the task, even though they were larger than previous MCI models, of keeping the monstrous heat produced by the 8V-92 from building up and causing engine overheating issues. That's why I mostly see 6V-92 installs in most of the buses of the time in just about everybody's bus brands. The 6V-92 mated to the indestructible Allison HT740 was the King of the highway coach power offering for many many years.

Eventually MCI changed to the full width radiator design of the "D" and "DL"s which also happened to cool 8V-92's much better, but by then the best engine by far was the new Series 60 4 strokes being ordered and which eventually became the new gold standard. Pretty much blew away the 8V-92 advantages in every area. That's why they took over so completely. As much as I LOVE me my Detroit 2-strokes I have to admit that the Series 60 is truly the ultimate dream engine to drive and maintain.

[lvmci]

...But with more experience it became pretty obvious that the MCI-102x3 twin side radiators weren't up to the task, even though they were larger than previous MCI models, of keeping the monstrous heat produced by the 8V-92 from building up and causing engine overheating issues...

Hence the reason I added the 3rd radiator...