| Author |
Message |
Bob Wies (Ncbob)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, May 11, 2006 - 1:02 pm: | |
It's great that there are so many fleet operators and owners on this board so I'm asking a question even though I might be close to the right answer......
I'm not going to go overboard to get the best fuel milage while on the road. I'd like to keep up with traffic and let the heavy haulers pass me and still keep in mind the wear and tear on my recently rebuilt 8V71.
For me that's about 1900-1950 RPM's. It works out to about 65-68 MPH.
Having operated motor yachts with Detroits for years we felt the 1950-2000 was optimum cruising speed for..say a 14 hour day.
Opinions or advice?
NCbob |
Geoff (Geoff)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, May 11, 2006 - 2:46 pm: | |
1900-1950 is okay for the engine (it will run at 2100 all day), but if you can get your RPM's at 1700-1800 you'll get better fuel milage. I don't like to run 8V71's lower than that although you can if you don't lug it on grades. I have my 6V92TA geared so I go around 63 mph at 1800 rpms and get 7.5 mpg. I could get 8 mpg if I went even slower. |
Gary Carter
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, May 11, 2006 - 4:27 pm: | |
The fuel flow charts for a 92series show the most HP per pound of fuel between 16 and 1700 RPM. Have never seen charts for a 71 series. |
Kevin Hatch
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, May 11, 2006 - 5:22 pm: | |
My mech set mine at about 1950rpm and it does great! 9-10mpg going 70ish mph! That is in the flats though (good ol' west Texas!).
Kevin Hatch
PD-4905
8V71 - 4spd |
Tom Caffrey (Pvcces)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, May 12, 2006 - 12:17 am: | |
Bob, our peak mileage seems to be around 62-65 mph. We've broken 10 mpg with our 27,000 lb. coach. We only lose about 1/4 mpg if we run around 73 or so. We lose about 1/2 mpg at 55.
This means that our peak mpg is right close to 1650 rpm.
Since the work load is really lightened up running at 55, I take it that the engine does better if it's got a pretty good load on it.
The wind noise above 70 tells me that the engine is working quite a bit harder, but the mileage hardly falls off.
This tells me that the best hp/fuel ratio is with a heavier load than when we're cruising at around 65.
For what it's worth.
Tom Caffrey PD4106-2576
Suncatcher
Ketchikan, Alaska |
Marc Bourget
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, May 12, 2006 - 1:03 am: | |
the best hp/fuel ratio is at best BMEP, Brake Mean Effective Pressure. It can vary by RPM depending on throttle setting because it's more or less "load" dependent. Higher RPM on the flat, lower ( a little) on a grade when carrying a little more throttle. |
niles steckbauer (Niles500)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, May 12, 2006 - 3:22 am: | |
I have found the best operating RPM w/ 2 stokes is where the the torque curve intersects the HP curve (power band) - too bad there's not a dyno at every garage for us to be able to 'dial it in' - FWIW |
john w. roan (Chessie4905)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, May 12, 2006 - 3:07 pm: | |
If your engine is set with advanced timing, it will get better fuel mileage at probably 1750 to 1900. |
Chuck Lott (Chuckmc8)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, May 12, 2006 - 4:31 pm: | |
How can you know if engine has advance timing? |
john w. roan (Chessie4905)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, May 13, 2006 - 8:15 pm: | |
For one, if it is a turbo model, it should be standard timing. If is na, there is a procedure in the factory DDC manual to determine this with a dial indicator.Also the injector tag can tell you , but not 100% of the time. |
herman
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, May 17, 2006 - 1:19 am: | |
Niles, I can't make any sense of your suggestion: if you change the scale factor for either the HP or the torque, the RPM of the point of intersection can be moved around to just about anywhere. |
FAST FRED
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, May 17, 2006 - 5:43 am: | |
GM set the Sports Car of Coaches , 4106 ,for 60 mph , 1650 rpm.
Slow by todays standards but probably the best for engine life and low fuel consumption.
If you can live with 1650RPM you may get 300,000+ between overhauls.
FAST FRED |
niles steckbauer (Niles500)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, May 17, 2006 - 7:07 pm: | |
Herman, I can see where maybe that was confusing - There is a point at the beginning of the top of HP curve and the end of the top of the Torque curve that usually provide the optimum benefits of both HP and Torque (wind cutting and hill climbing) - If you look at the time of my post you probably understand why I was a bit non-intelligible - HTCIU |
Frank 4106
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, May 17, 2006 - 8:09 pm: | |
Niles,
HTCIU ??? |
niles steckbauer (Niles500)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, May 17, 2006 - 9:27 pm: | |
(H)ope (T)his (C)lears (I)t (U)p |
Buswarrior (Buswarrior)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, May 18, 2006 - 11:19 pm: | |
ok, yeah.
P&PE
P(issed) and P(ie) E(yed)
EH?
happy coaching!
buswarrior |