Detroit 6V92

[Moder2]

Does anyone have a 6v92? What do you think of it?

Im considering a MH with this powerplant, and have some experience with them in Buses, where they were very reliable. Would like the owners opinions though.

Thanks,

John

[Jim Scoggins]

Here is a post that someone else made a while ago. 6V and 8V are essentially the same except number of cylinders. Had an 8V92TA in a 86 Bluebird--liked it a lot--trouble free.

The 92-series Detroits are two-cycle engines.

All current production diesels are 4-cycle.

Detroit stopped production on the 2-strokers due to EPA requirements - and for no other reason. They simply would not meed EPA emissions requirements on or off-road, no matter what they tried - and try mightily they did, with their DDEC and then DDEC-II (electronic control) systems.

Ultimately, they were forced into 4-stroke production.

It is true that modern electronic engines get better fuel efficiency. However, there is a LOT to be said for a basic engine design that goes back to WWII!

I have 6V92s on my boat (two of 'em.) Detroit's basic design was simplicity itself, and ingenious. The supercharger on these engines is necessary; they will not run without them. There is no intake valve system at all. The valves are all for exhaust; as the piston moves down on a power stroke, the exhaust valves open and at the same time the piston uncovers a port, much like a 2-stroke outboard motor, that leads to an airbox that is pressurized by the blower. The clean air forces out the exhaust. When the piston moves back upward the valves close and the ports are covered; compression occurs, and fuel is injected at the appropriate time. Injection is performed by a cam-driven unit injector. The design is extremely simple - ingenious, really. The emissions problem comes from being unable to perfectly scavenge the exhaust. However, these engines tend to run very low EGTs compared to 4-stroke turbodiesels due to the overabundance of air that flows through them on a given power cycle.

The nice thing about Detroits is that there is no high-pressure injection pump or electronics. They will run, once started, so long as they have fuel and compression. You can also replace the entire fuel system (the injectors) for about $100 a hole and the low pressure fuel lift pump for a couple hundred bucks - these are unit injector engines. With under $200 worth of special tools you can keep a Detroit running in tip-top shape for a loooong time, and properly maintained they are great motors. They have a reputation (somewhat earned) as oil leakers, which is due to the fact that Detroit made the blocks so they could be "doubled" - thus, you have 6V92s, 8V92s, 12V92s (two 6V92s end-to-end) and 16V92s (two 8V92s end to end!) This, however, means there are oil ports and such on the ends of the blocks that have plugs in them and thus they tend to leak oil....

The other thing to be aware of is that Detroits are quite inexpensive to get parts for. A cylinder kit, for example, is about $600 - that's the liner, piston, con-rod, rings, etc - the whole shot. One new hole, coming up. So for about $5k in parts you can do a complete kit replacement, and it can be done "in-frame" - without pulling the motor.

Detroits have no glow plugs and "off the shelf" no starting assist. They are ENTIRELY dependant on engine compression to start. They also require (not recommend, REQUIRE) straight weight 40 grade Cx-II oil. Multigrade oils are strictly forbidden due to the high shear strength required by the injector followers - you WILL destroy cams if you run a 15W40 in them, for example, and you'll also get incessant low oil pressure warnings and probably a spun main to go with it. Unlike "modern" diesels its not uncommon (nor a problem) to have oil pressure readings as low as 10psi at idle when fully warmed up! Normal oil pressure at power (1800 rpmish) is in the 45-50psi range though, just like modern engines. What this means is that in cold weather you need STOUT batteries or you will not be able to roll them over at a high enough RPM to get 'em to light. Block heaters are strongly recommended for the winter months. Ether is very dangerous to use on these engines; I know people who have and do, but my recommendation is "never" on a Detroit.

The nemesis on the 92 Series Detroits is overheating. This is a wet liner design with elastomer (O-ring) seals at the top and bottom of the cylinder liner. If you overheat these engines, even just a bit, the liner seals will be compromised. The result will be oil to cooling system leaks, and if not caught very quickly, damage to the mains or even worse, a spun main and damaged crank. Cooling system maintenance is THE big deal on these motors. Keep them running cool and all is well. Let them get hot and you will be rebuilding them.

Also, later versions of these engines in "turbo" trim used aftercoolers, which are under the blower. That needs to be kept clean; getting to it requires removing the blower, which requires disturbing the governor and fuel rack. Its not a tough job, but it is a pain in the butt. Thus, its important to avoid exhaust leaks and use a good air cleaner so that becomes an infrequent problem rather than a frequent one.

Finally, there is the matter of airbox drains. The airbox on a Detroit is where the blower "accumulates" the charge for scavenging and the new combustion cycle. The blower seals, as the blower ages, and turbo seals will eventually leak small amounts of oil, and the compression and then cooling of the air charge causes water to condense. The airbox drains allow this accumulated crud out of the airbox instead of having it sucked into the cylinders where it will cause abnormal wear. On turbo motors there are check valves located at each drain; these must work properly. If they stick open or closed its bad news; many people neglect these service items. They should be pulled and cleaned at every oil change, and if you have motors where Detroit routed them back to the oil pan (they did on some motors, as the EPA had a kitten about the original design which just allowed the slop to go onto the road) you will do your engine a huge favor by removing that and routing them to a "crap can" that you then empty once in a while (at oil change intervals is a good choice.)

I'm very much "up" on the 92-series engines, since I own two and maintain them myself. Set up for reasonable power levels (500HP from an 8V92TA is reasonable) and proper maintenance they provide extraordinarily good service. The 8V89TA CAN be "hot-rodded" to as far as 750HP quite cheaply just by changing injectors and a few other things - don't be tempted, as the service life in that configuration can be as short as 1500 hours or less between overhauls!

The DDEC and DDEC-II versions of these engines replace the mechanical fuel rack with electronic control of the injectors and a bunch of sensors in an attempt to get cleaner and more fuel-efficient operation from them. Its mostly successful, but now you're into the computer-controlled realm and simple mechanical maintenance procedures go out the window.

If I was going to own a Detroit-powered coach, I'd want one with mechanical injection - if I'm gonna buy an electronic engine, I want one of the new design ones, as if I'm gonna get the warts I want the benefits too. With a handful of parts and a few tools on board I can fix these things by the side of the road if necessary so long as I haven't spun a main or something equally catastrophic - something you simply won't be doing with "today's technology".

[Moder2]

Thanks for all the detailed info Jim. Much appeciated.

I was all excited about thsi coach, but I think the deal is going to fall through, I am jsut not willing to pay what he wants... There is just too many miles on it to warrent that. Oh well, atleast I come away with a better understanding of the DD 6V92!



Thanks again,

J

[Lug_Nut]

Great explanation Jim. The 8V89 however I've never heard of. The only ones I remember were the 71, 92 and 149 series also coresponding the cubic inch displacement per cylinder.

[Jim Scoggins]

Lug_Nut
I didn't see where I referred to an 8v89. If I did so it was a typo. I had an 8V92.

[Jim Scoggins]

Lug_Nut.
I found it. It was a typo in the article itself. Good eye.

[Cruzer]

Originally posted by Lug_Nut:
Great explanation Jim. The 8V89 however I've never heard of. The only ones I remember were the 71, 92 and 149 series also coresponding the cubic inch displacement per cylinder.

There's also the 53 series. I worked on a number of them back in the early 70s. Less power than the 71s but similar in design. The 92s weren't out at that time and the dominant engine was the Cummins was the NH or NT series - all pre-electronics of course.

[Catdave]

An excellent post, Jim.
Very informative and interesting.

Makes me long for the days when all it took to motivate was fuel and air...

[Gary RVRoamer]

Here's a bit of Detroit Diesel trivia...

The Detroit Diesel 2-cycle diesels were all named according to a formula that goes like this:

The first digit is the number of cyliners in the engine

The second is a letter and designates the type of engine block, usually "V" for a V-block or "T" for an inline block with T-shaped heads.

The third, fourth and (on larger engines) fifth digit is the displacement of each cylinder in cubic inches.

Thus, a 6V92 is a six cylinder, V-block engine with 92 cubic inches per cylinder. An 8V92 is the same except it has 8 cyliners. An 8V149 has a whopping 149 cubic inches per cylinder.

In later years, one or more letters were tacked on the end of the basic designation to indicate special features such as a "T" for Turbocharging, "TI" for Turbocharging + Intercooling, etc.

Most of the Detroit 2 cycles blocks were designed such that they could be literally bolted together to make larger engines. Thus a 16V149 is a 16 cylinder (a pair of V8's) with 149 cubic inches per cylinder. Rumor has it there is a 16V149 mounted at the North Pole and that is what makes the earth rotate...

[edgray]

Rumor has it there is a 16V149 mounted at the North Pole and that is what makes the earth rotate...

and, rumor has it, there is NO gear reduction. It's direct drive.

[Nlmlands]

Originally Posted by Jim Scoggins

Here is a post that someone else made a while ago. 6V and 8V are essentially the same except number of cylinders. Had an 8V92TA in a 8 TV6 Bluebird--liked it a lot--trouble free.

The 92-series Detroits are two-cycle engines.

All current production diesels are 4-cycle.

Detroit stopped production on the 2-strokers due to EPA requirements - and for no other reason. They simply would not meed EPA emissions requirements on or off-road, no matter what they tried - and try mightily they did, with their DDEC and then DDEC-II (electronic control) systems.

Ultimately, they were forced into 4-stroke production.

It is true that modern electronic engines get better fuel efficiency. However, there is a LOT to be said for a basic engine design that goes back to WWII!

I have 6V92s on my boat (two of 'em.) Detroit's basic design was simplicity itself, and ingenious. The supercharger on these engines is necessary; they will not run without them. There is no intake valve system at all. The valves are all for exhaust; as the piston moves down on a power stroke, the exhaust valves open and at the same time the piston uncovers a port, much like a 2-stroke outboard motor, that leads to an airbox that is pressurized by the blower. The clean air forces out the exhaust. When the piston moves back upward the valves close and the ports are covered; compression occurs, and fuel is injected at the appropriate time. Injection is performed by a cam-driven unit injector. The design is extremely simple - ingenious, really. The emissions problem comes from being unable to perfectly scavenge the exhaust. However, these engines tend to run very low EGTs compared to 4-stroke turbodiesels due to the overabundance of air that flows through them on a given power cycle.

The nice thing about Detroits is that there is no high-pressure injection pump or electronics. They will run, once started, so long as they have fuel and compression. You can also replace the entire fuel system (the injectors) for about $100 a hole and the low pressure fuel lift pump for a couple hundred bucks - these are unit injector engines. With under $200 worth of special tools you can keep a Detroit running in tip-top shape for a loooong time, and properly maintained they are great motors. They have a reputation (somewhat earned) as oil leakers, which is due to the fact that Detroit made the blocks so they could be "doubled" - thus, you have 6V92s, 8V92s, 12V92s (two 6V92s end-to-end) and 16V92s (two 8V92s end to end!) This, however, means there are oil ports and such on the ends of the blocks that have plugs in them and thus they tend to leak oil....

The other thing to be aware of is that Detroits are quite inexpensive to get parts for. A cylinder kit, for example, is about $600 - that's the liner, piston, con-rod, rings, etc - the whole shot. One new hole, coming up. So for about $5k in parts you can do a complete kit replacement, and it can be done "in-frame" - without pulling the motor.

Detroits have no glow plugs and "off the shelf" no starting assist. They are ENTIRELY dependant on engine compression to start. They also require (not recommend, REQUIRE) straight weight 40 grade Cx-II oil. Multigrade oils are strictly forbidden due to the high shear strength required by the injector followers - you WILL destroy cams if you run a 15W40 in them, for example, and you'll also get incessant low oil pressure warnings and probably a spun main to go with it. Unlike "modern" diesels its not uncommon (nor a problem) to have oil pressure readings as low as 10psi at idle when fully warmed up! Normal oil pressure at power (1800 rpmish) is in the 45-50psi range though, just like modern engines. What this means is that in cold weather you need STOUT batteries or you will not be able to roll them over at a high enough RPM to get 'em to light. Block heaters are strongly recommended for the winter months. Ether is very dangerous to use on these engines; I know people who have and do, but my recommendation is "never" on a Detroit.

The nemesis on the 92 Series Detroits is overheating. This is a wet liner design with elastomer (O-ring) seals at the top and bottom of the cylinder liner. If you overheat these engines, even just a bit, the liner seals will be compromised. The result will be oil to cooling system leaks, and if not caught very quickly, damage to the mains or even worse, a spun main and damaged crank. Cooling system maintenance is THE big deal on these motors. Keep them running cool and all is well. Let them get hot and you will be rebuilding them.

Also, later versions of these engines in "turbo" trim used aftercoolers, which are under the blower. That needs to be kept clean; getting to it requires removing the blower, which requires disturbing the governor and fuel rack. Its not a tough job, but it is a pain in the butt. Thus, its important to avoid exhaust leaks and use a good air cleaner so that becomes an infrequent problem rather than a frequent one.

Finally, there is the matter of airbox drains. The airbox on a Detroit is where the blower "accumulates" the charge for scavenging and the new combustion cycle. The blower seals, as the blower ages, and turbo seals will eventually leak small amounts of oil, and the compression and then cooling of the air charge causes water to condense. The airbox drains allow this accumulated crud out of the airbox instead of having it sucked into the cylinders where it will cause abnormal wear. On turbo motors there are check valves located at each drain; these must work properly. If they stick open or closed its bad news; many people neglect these service items. They should be pulled and cleaned at every oil change, and if you have motors where Detroit routed them back to the oil pan (they did on some motors, as the EPA had a kitten about the original design which just allowed the slop to go onto the road) you will do your engine a huge favor by removing that and routing them to a "crap can" that you then empty once in a while (at oil change intervals is a good choice.)

I'm very much "up" on the 92-series engines, since I own two and maintain them myself. Set up for reasonable power levels (500HP from an 8V92TA is reasonable) and proper maintenance they provide extraordinarily good service. The 8V89TA CAN be "hot-rodded" to as far as 750HP quite cheaply just by changing injectors and a few other things - don't be tempted, as the service life in that configuration can be as short as 1500 hours or less between overhauls!

The DDEC and DDEC-II versions of these engines replace the mechanical fuel rack with electronic control of the injectors and a bunch of sensors in an attempt to get cleaner and more fuel-efficient operation from them. Its mostly successful, but now you're into the computer-controlled realm and simple mechanical maintenance procedures go out the window.

If I was going to own a Detroit-powered coach, I'd want one with mechanical injection - if I'm gonna buy an electronic engine, I want one of the new design ones, as if I'm gonna get the warts I want the benefits too. With a handful of parts and a few tools on board I can fix these things by the side of the road if necessary so long as I haven't spun a main or something equally catastrophic - something you simply won't be doing with "today's technology".

I have a 6v92. Died but running great just before. I have changed all fuel filters but not getting fuel. 1971 silver eagle bus. Started with starter fluid but died and I dont like to use that. Any sugestions.

[Nlmlands]

suggestions. Am new at this forum, so pardon me. I added to that message by mistake. I do need help with getting this 6v92 started.

[mackwrench]

..... I'll assume it's not out of fuel, but it sounds like your having a fuel supply issue.

Is the secondary fuel filter located at engine compartment? Find the "inlet" on the filter head, remove the line, usually a 3/4" wrench, the rig up a piece of hose from a 5 gallon can of clean fuel to the filter inlet. Remove and refill the secondary filter....

Try and start it, you may have to hold it 1/2 or full throttle for a bit to bleed air from fuel system if it runs.

IF this works, then you know program is between secondary filter and tank. I'd guess a fuel line that's crapped out on the inside causing restriction.

You can also take a air hose and blow air into fuel tank, using a rag/old towel around hose/fuel cap opening, it should push fuel back to the secondary filter line you'll have off.


.....if that doesn't work then by chance the fuel supply gear pump maybe failed or sized and broke shaft, but that's another issue.

Good luck!

btw, I loved those old DD! I understand emissions are "it" but I loved to work on them

[BigLar368]

Our city buses back in the mid 90's all had V6-53 series Detroit engines in them. They were the most gutless diesel engines I ever drove or worked on. As I recall we only had one piece of equipment with a V6-92 series engine . It was in a twin turbo model in a Bomag street mixer. Like a big roto tiller except it tilled up asphalt streets. It was a beast. When that thing would come up to RPM it would make the hair stand up on my arms. We never had a problem with it.