8V92N core

[Geoff]

I ran across an unusual Detroit engine yesterday-- a RH 8V92N-- in other words, NO TURBO.  Hard to find, and someone might be able to use it to replace an 8V71N in a bus that doesn't have room for a turbo (MCI5?).  I believe these put out around 400HP.  The engine is just a core but is complete and good for a rebuild.

--Geoff 
Arizona
928 771-0045

[HB of CJ]

Might be a sweet retro way to make a cool hot rod 4106 Bus Conversion into a more hot rod 4106 Bus Conversion.  HB of CJ (old coot)

[TomC]

Because of the big front vibration damper, 8V-92's cannot be used for a V-drive. But, there's probably someone that took the time, effort and money to make it work. Good luck, TomC

[CrabbyMilton]

Good info Tom. It may be academic but I have some old ALLISON  brochures it it says that te maximum HP for the V730 is 275. So would such numbers preclude an 8V-92 turbo or not? I know the 6V-92 TA is often rated at 350 HP and that is over the 275HP limit.
So are the guys who are putting the 6V92TA in the 4106's with the V730 putting the life of the tranmission at risk of early demise because of the higher HP and torque? I mean the 8V-92TA is rated well over 400HP.

[luvrbus]

 You don't need a vibration damper on a low hp 8v92 they do fine without one we installed a 350 hp 8v92 N/A in a MCI 5 with a 644 Allison it's been running for 11 years without a vibration damper and a 644. Richards(driving mrs lazy) old Eagle has a 435 hp 8v92TA it never had a vibration damper Mike the present owner is still running it without one fwiw.It's not a problem to set a 8v92TA @ 350hp MCI used that setting for a few years

[CrabbyMilton]

You made me remember something now. I do remember now that MCI did(perhaps others) offered the DETROIT 8V-92TA in a 350(I think) version. But what I didn't get is that the 6V-92TA had a 350HP version at the same time. So could the reason for a lower power 8V-92TA so the operator could upgrade to higher HP at some point with the same engine in place? Or where there different ratings for buses as opposed to trucks and other applications like fire apparatus. I have the brochures but they are buried in boxes.

[bevans6]

I would expect that a 350 hp 8V-92TA would have a lot higher torque at low rpm than a 350 hp 6V-92TA, and so would drive like a much more powerful engine.  I think I will look and see if I can find any brochures...   

Brian

[luvrbus]

Both had the same amount of torque if I remember it was 1175 ft pounds fuel savings was the idea the 8v82 with the 7G75 injectors would get better mileage with less smoke than a 350 hp 6v92 with 9G90 injectors,plus the 8V92TA 350 hp was a 1800 rpm engine vs the 2100 rpm 350 hp 6V92

[HB of CJ]

I do not remember if the very old non turbo 8v92 Detroits even had a front end vibration dampener. Certainly 1200 pounds of torque would not do that Spicer, clutch or angle gear gadget or shaft any long term good.  One good solution is to keep your foot out of it in the lower gears.  In 4th or high gear, go for it.  HB of CJ (old coot)

[TomC]

I had my V730 rebuilt. I told the shop (in Riverside, Ca [can't remember the name]) that I was running a 375hp with 1125lb/ft torque 8V-71 turbo. They beefed it up, increased clutch pressure. I can notice the difference. Under less than full throttle, it shifts firmly. Under full throttle it shifts like you would think it should. With a turbo engine, you don't have to worry about fast throttle response. Hence the power comes up slowly.

Side note-the new Diesels are so responsive now (no to full power in 1/4 second) Meritor has come out with a 35 series U joint. When using a direct drive transmission with axle ratios now down to 2.21, the U joints are taking a beating, especially when fully loaded trucks first come up out of the loading dock. High efficiency low rpm engines are being offered by Cummins and Detroit. Cummins ISX 15 has a 450hp @ 1,600rpm with 1750 torque at 1100rpm.  Detroit has the DD15 at 400hp @ 1,600rpm with 1750 torque @ 975rpm! With the 2.21 gearing running 510rpm tires, at 65mph, the engines are turning 1221rpm with the Detroit. Cummins advantage with the specially made 10spd Ultrashift overdrive (only a .80 overdrive compared to .74) and running a 2.65 rear ratio, at 65mph the ISX15 is turning 1171rpm. With slower engines, comes better fuel mileage and with the common rail fuel injection, timing is infinite. Low rpm engines are smooth running, compared to just a few years ago when you didn't dare go lower than 1200 with a 4 stroke or under 1400 with a 2 stroke. Good Luck, TomC

[eagle19952]

with 1750 torque @ 975 rpm
running a 2.65 rear ratio, at 65 mph the ISX15 is turning 1171 rpm.

How many days does it take to get up to highway speeds ? 

[TomC]

One of my customers let me drive the new low rpm engines. Performance wise, they work very well. Just hard to get used to up shifting around 15-1600 and down shifting at 1000. But, acceleration, hill climbing, etc is just the same. It doesn't matter what the rear end ratio is. As long as you can get the vehicle moving, any speed in between top speed and stopped is taken care of by the transmission. Who cares what gear you're in if you're pulling a hill at, say 1300rpm. You are still get exactly the same power pulses per foot whether you had 2.65 gears, or 4.11 gears. Rear end ratio, transmission ratio doesn't get you up the hill, engine torque, and lots of it gets you up the hill. Good Luck, TomC

[bevans6]

I always found it funny, kind of questioned the wisdom, that we all try hard not to "lug" a two stroke, yet they make maximum torque at around 1400 rpm and only a titch less at 1200 rpm.  The have to be running clean and strong to make maximum torque, so why do we fuss about running them that low on the road?

Brian

[niles500]

Brian- max torque (what gets you going) is produced at full throttle, not cruising throttle, max HP is at a higher RPM in the power band, HP is what keeps you going - FWIW

[bevans6]

I know that.  For the record, I completely and fully understand the relationship between torque and power and rpm, ever since I had it drilled into me in first year physics.      My question has nothing to do with that.  My question is why are we taught that running a two stroke at 1200 or 1400 rpm at full throttle is bad?