8V-71 goverened speed

chessie4905 · July 20, 2018, 04:59:49 AM

How high is your max engine governed speed and what rpm's. do you run at? Not the factory spec.

luvrbus · July 20, 2018, 05:44:06 AM

I set the 8v71@ 2450 rpm and tell the people to run between 18 and 1900 rpm,you run one against the governor all the time it just creates oil leaks,the 2450 rpm comes in handy some time between gears is the reason I do it YMMV.I never go above 2200 rpm on the 92 series

TomC · July 20, 2018, 11:01:37 AM

2,450 is a good no load RPM to set the 8V-71. Although truckers from the 70's used to regularly turn them up to 2,800, but of course shortens the life. 1,800-1,900 cruise is good-with cruising at 2,100 is alright too, just more fuel burned. If you have N65 injectors, torque was rated at 1,600rpm. If you have N60 or N55 injectors, torque was rated at 1,200rpm.
Interesting to note, with my V730, on light partial throttle, it can shift early bringing the RPM down to 1,100rpm on shift. Full throttle shifts are set at 1,950, so I can manually hold it in gear with the gear shift if necessary. The transmission will up shift from 1st to 2nd at 2,400 even if in 1st. Good Luck, TomC

Fred Mc · July 20, 2018, 02:07:41 PM

When I got my bus I lived in a logging community when a lot of the trucks had 871s They all told me to slam my finger in the door and drive the?sh$t out of it so I find it interesting that it can cause more oil leaks. Good to know.

chessie4905 · July 20, 2018, 02:35:26 PM

You run a detroit against the governor all day, you'll have leaks you never had before

luvrbus · July 20, 2018, 02:52:38 PM

If you read the oil consumption charts for a 2 stroke it goes up also with higher rpm,like a 8v71 will consume a little over a 1 quart at 1700 rpm and it jumps to 3 quarts at 2200 rpm in 10 hours of run time,this why some can travel 4 or 5 thousand miles and never add a gal of oil,then others will add a gal every 1200 miles

eagle19952 · July 20, 2018, 03:01:13 PM

Quote from: luvrbus on July 20, 2018, 02:52:38 PM
If you read the oil consumption charts for a 2 stroke it goes up also with higher rpm,like a 8v71 will consume a little over a 1 quart at 1700 rpm and it jumps to 3 quarts at 2200 rpm in 10 hours of run time,this why some can travel 4 or 5 thousand miles and never add a gal of oil,then others will add a gal every 1200 miles

oil is cheap.Time is irreplaceable

Geoff · July 20, 2018, 05:10:47 PM

Question is what I have my engine, 6V92TA, rpms set at. Try 2900, cruise 1900-2100, idle 625. Reason for such high no load rpm's is because I have
military Jakes that required it for the Jakes to work at all.

lostagain · July 20, 2018, 05:13:19 PM

I was trained to driver buses by Brewster Transport when I hired on with them in 1973. Of course all we had was 2 stroke 71 series Detroits. We were taught to drive them on the governor all the time, all day. So we had our foot on the floor the whole time. You had to be on the governor to facilitate down shifting. Every morning we checked the oil and added as necessary from the tank on the right of the engine compartment. That was kept full by the mechanics at the shop. If going on a extended trip out of town, we took extra jugs of 40W. I guess they leaked, they all leaked, it was normal. The 71 series needs to be driven with your foot on the floor. The oil consumption and leaking is just part of it, get used to it.

Now the 92 series is not driven as hard, and it doesn't use as much oil, or leak at all if looked after.

Nowadays the newer engines (Volvo in the Prevost and Cummins in the MCI) only rev at 1200 at 70 mph. And you don't even have to know at what rpm they shift because the Allison does it all seamlessly. All you do is stab the pedal and steer...

JC

luvrbus · July 20, 2018, 06:35:04 PM

Quote from: Geoff on July 20, 2018, 05:10:47 PM
Question is what I have my engine, 6V92TA, rpms set at. Try 2900, cruise 1900-2100, idle 625. Reason for such high no load rpm's is because I have
military Jakes that required it for the Jakes to work at all.

I don't why it take 2900 rpm to make the Jakes work that is interesting,I have 2 -8v92 military engines with Jakes and they are set at 2100 ? is your oil pressure low they will not work below 15 psi

luvrbus · July 20, 2018, 06:57:23 PM

Most bus engines were set @2100 rpm from the factory as a no load,that gives you 1850 to 1900 rpm under a load.
The fuel squeezer engines were set @ 1950 rpm from DD and had tamper proof governors so the drivers could not raise the rpm lol I have a couple of those laying around that people tried to remove the plugs with a torch and screwed the cover up

chessie4905 · July 20, 2018, 07:48:01 PM

Mines at 2450 no load. About 74 mph wound out. 4:27 rear with 315-80x 22.5. changing rear to 4:11 and tires to 12:00 x 22.5 should get me to about 80 or slightly more.

Fred Mc · July 20, 2018, 10:06:35 PM

My 63 GMPD4106 is stock with no tach so I don't even know what rpm's its turning.Is there a corresponding rpm to mph chart somewhere so I can determine engine rpm's.

Thx

Fred

chessie4905 · July 21, 2018, 04:41:19 AM

Assuming you have an accurate speedo or a GPS to indicate mph, how fast will your coach go. And what is your rear tire size?

Bill Gerrie · July 21, 2018, 04:45:52 AM

My 6V92TA DDEC IV is set at 2110 and no way to change. With the Bill Teal over drive it will still do over 80 mph and cruises at 65 mph at 1500 rpm. I have a 4.56 to 1 rear end and 12R22.5 tires. Good mileage and less wear on the engine. No oil leaks either.