Silver 8V92 OTR: Questions for the two stroke gurus

Discussion in 'Trucks [ Eighteen Wheelers ]' started by Shedlock2000, May 20, 2024.

  1. Shedlock2000

    Shedlock2000 Bobtail Member

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    Hi all,

    I have a couple of specific questions related to running a silver 8V92TA in OTR application that I can’t find consistent answers to in the many related threads on here.

    I am thinking about buying a a flat-top ‘87 W900b with 3.90 rears, an 18 speed (true double over), and a late silver 8V92TA with upsized injectors that (I am told) pushes about 525bhp for bull hauling at 105,500lbs with quad axle trailers and tractor on a regular route down the I15 out of Canada. There are at least 7 long pulls at between 5% and 9% grade (which I read are not the 8V92s best terrain) and a lot of flat.

    Here are the specific questions I am looking for answers to:
    1. I hear these things can run backwards. What exactly causes them to do so (we used to have a two stroke dumper that would run backwards if you didn't let it die completely when pulling the cable fuel cut-off. I am assuming that doesn’t apply here)?
    2. I hear these things can run away on you, too. What exactly causes them to do that?
    3. What would real-world fuel figures be like pulling a moo house? The current owner has fuel and mileage records to show he’s getting 6-6.5 on the flat out of Ontario to Illinois hauling a can at 80,000lbs and shifting at 1650 and 1950rpm. From what I read, that seems very unlikely — so what gives?
    4. What is the actual torque likely to be at 525 (I am assuming it is a 475 tweaked). I read that the TA generated 1250lbft at 1400rpm, but also read that they like to cruise at 1650rpm. Knowing they have a flat torque curve, would 1250 be the peak torque on the hills at 1900?
    5. Ignoring the Kitty and Cummins naysayers, was this engine particularly fragile (Cats are particularly finicky and expensive to rebuild, Cummins are less reliable but cheaper to rebuild — what is the deal with the DD 2 strokes)? It currently does not leak any oil (save whatever minimal blow-by is found in the air box cans), but do they suffer from anything else other than twitchy governors?
    6. I may need, in very cold temps, to idle the truck at the lot over night (else it likely wouldn’t start in the morning). I know these things don’t like idling (it has a 1100rpm fast idle switch fitted), but is idling for 6 hours at -20ºc completely out of the question?
    7. In comparison to a well-running BC2 at 440bhp, which would you expect to pull better on the hills and what would your expected fuel comparison be between the two.
    8. I understand these engines prefer to run at a consistent rpm for long periods of time. Given that a significant part of the run is 14 hours on flatish highway, is this kind of OTR stuff what this engine performs well at (compared to city work, for instance)?
    9. What is your guidance for engine overhaul intervals? I read that these engines kind of tell you plenty of time in advance that they need overhauling?
    10. Disregarding the ‘slam your hand in the door’ stories, how do these engines shift in comparison to the Cummins BC or the Cat 3406 (the latter being my preference, as I always find Cummins to quite to fall and too snatchy)?
    Thanks in advance for your thoughts. Any additional thoughts related to the discussion are welcomed. I have a lot of experience with engines and mechanical work, so I am not frightened by the potential of fiddling here and there; however, I do have zero experience with Detroits of any kind.

    Photos for attention: IMG_3908.jpeg IMG_3909.jpeg
     
    Last edited: May 20, 2024
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  3. BoxCarKidd

    BoxCarKidd Road Train Member

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    1: When someone is trying to take off. Chocks the engine down, mashes the clutch and it kicks back it can run backwards. Blows smoke out the air filter when it does that. Thank the later models should shut down with the key. If not choke it down with the clutch again. It is uncommon.
    2: When oil starts blowing out a turbo or blower seal they can run away. RPM is unstoppable until it explodes. I had even seen a Mack run away. The older ones had fixed racks. If one injector stuck they were all wide open and here we go. Later models have spring loaded injector levers. One cannot hold the rest and one will carry not carry it away.
    If one is really worn out using lots of oil they can suck up that excess oil and run away as well.
    4 through 10. I cannot really answer about that fuel consumption The last ones I was around were built in 1995. They were in 2505 Terrigators. 2 burned 60 gallons a day and the third burned 80? They were all sisters doing the same job. Seems like Detroit pretty well had them all worked out by that time in Gators and trucks but they could not pass emissions.
    Do not ever remember driving one of those in a loaded truck. The ones in Gators liked higher RPM as did the 8V71's. 71's would twist up to about 2800 rpm. A little flat loaded on a big hill. Doubt they ever go over 5 MPG. Big Rick's was the fastest Astro. Manual steering and bias steer tires. He said she could run out about 92's on a good day's. The later Provosts 92's were DDEC, electronic.
    Cannot answer all your questions but the latter 92,s that I was around were dependable. Do not let them run at low idle for hours.
     
  4. Shedlock2000

    Shedlock2000 Bobtail Member

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    Thanks, BoxCarKidd! That’s very helpful info. Regarding the idling, what did drivers do with them back in the days these were more common to keep cool/warm? It’s easy enough to fit a Webasto or similar now, but that stuff wasn’t about then!
     
  5. BoxCarKidd

    BoxCarKidd Road Train Member

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    Adjustable hand throttle set at about 950 is good in my opinion. That 1100 is probably fine just sounds a bit high. is it adjustable?
    If it is one with the air box drains connected back to the oil pan do away with that as Detroit did.
    I watched a man with an old worn out 8V at low idle with 2 one gallon oil jugs under it catching the slober from the air box drains. The tops were cut out a little bigger on one side. I thought he was just keeping it off the ground so ho did not get kicked out of the place. He picked them up. Poured that junk back in the engine oil fill tube. Hung those jugs back up on hooks on each side of the frame and left.
    It is true because I cannot make stuff like that up.
     
    Shedlock2000 Thanks this.
  6. Shedlock2000

    Shedlock2000 Bobtail Member

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    Well, I’ve heard of recycling, but that’s a bit much!

    No, the air can pans are separate and require draining every now and then. Buddy says he dumps his once a month but there’s only 1/4” in them at most — he admits to hardly ever idling.

    The fast idle is adjustable — I think it’s one of those bolt on electric affairs, but I haven’t seen the device itself. It operates from a switch in the cab near the key. I might have 1100rpm wrong now — I haven’t seen the tach while it’s idling, I’ve only heard the engine and my guess was just that. It’s regular idle is 600 — which surprised me for being that slow.

    When the throttle is blipped to somewhere about 1500 rpm, there is a gentle puff of brownish smoke which carries the faintest blue as it disappears. He says it uses two quarts of oil every month running 12,000 miles or so. It’s only been run on Delco 40 and has a Lubrifiner installed.
     
  7. BoxCarKidd

    BoxCarKidd Road Train Member

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    Never saw pans under one. Ours just slobbered on the ground like old school. I thank Delo 40 low ash is best. We had to special order and stock it ourselves.
    That is the same filter set up used by a trucking company I worked for in the 80's. They went 16,000.
    Sounds like it has been well cared for.
     
    Shedlock2000 Thanks this.
  8. BoxCarKidd

    BoxCarKidd Road Train Member

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    I am not a 2 stroke guru but I did work under some of them. They are probably all gone buy now. Lift my hat to those people that helped me.
     
    Shedlock2000 Thanks this.
  9. BoxCarKidd

    BoxCarKidd Road Train Member

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    Thanking back I did see that in a manual. They were trying to appease the EPA.
     
    Shedlock2000 Thanks this.
  10. Shedlock2000

    Shedlock2000 Bobtail Member

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    The current owner seems to be the sort that fiddles a lot. He said he’s had the rack off because he didn’t like how it ran and wanted to set it up better; he also did something to some linkage or other which he said was letting some of the injectors to fire slightly later than the others. So I get the impression the guy is on top of things.
     
  11. Shedlock2000

    Shedlock2000 Bobtail Member

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    The pans were, or the Lubrifiner was? The pans make sense to me. He says they’re connected somehow and haven’t be detached, but I haven’t yet seen them myself.
     
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