sweet spot on 12.7 60 series?

robertglines1 · September 10, 2012, 08:24:53 PM

I've run 2 strokes in past buses and run them pretty tight. Sounds like the 12.7 60 series runs a lot lower rpms. I know you run what it takes to run the speed you want. The 8V92 really liked 1950 to 2000. Just sort of sat there and enjoyed life with no problems. Bob

lostagain · September 11, 2012, 06:58:25 AM

When I drove the hockey team's D3 with 12.7 L Series 60 and 7 speed Eaton-Fuller, I really enjoyed lots of torque starting at around 1200 rpm and all the way to about 1800 rpm. You can feel it falling off beyond that. So, after shifting 2 strokes on the governor for so many years, I had to get used to shifting mid range. But all that power is so nice. It was a pre EGR too, (1995).

JC

garhawk · September 11, 2012, 07:29:25 AM

Hi Lostagain,

I have a 12.7 Series 60 and it seems to me that the sweet spot is somewhere in the 1350 to 1450 range. It is hard to tell using the 740 transmission becuase the engine must turn close to 1700 for reasonable freeway speeds.

Turning in the higher rpm range, the big 6 cylinder 4 stroke still rewards (?) us with 7.3 mpg fuel.

We have misters on the radiator for those 100 degree days in the mountains. We average about 107.3 mpg water!

Sorry! The devil made me say it.

lostagain · September 11, 2012, 07:47:15 AM

garhawk,

I don't understand your comment about the 740 trans having to rev 1700 for reasonable speed.

I have the HT 740 in my 5 with 6V92TA and it will stay in 4th, or any gear down to 1200 rpm, maybe even lower, unless I down shift it manually.

JC

belfert · September 11, 2012, 08:14:00 AM

I've heard that around 1,500 RPM is the best MPG on a Series 60. At 65 MPH with a B500 transmission I am just a hair over 1,500 RPM. My B500 has 6th gear disabled from the factory.

TomC · September 11, 2012, 12:26:05 PM

Any of the Series 60's, whether it be the 11.1, 12.7 or 14.0 all had the same rpm ranges. Shifting at 1600-1800rpm is prime, and although it will run up to 2,100rpm, it serves no purpose-maximum horsepower is produced at 1800rpm. So revving higher just uses more fuel. Down shifting-maximum torque is produced at 1200rpm. Letting it go to 1100rpm before shifting is acceptable.
Cruising for maximum fuel mileage should be between 1400 and 1600rpm. With the electronics on the engine, you can't hurt a Series 60 by lugging it to low or trying to over rev it.
As to running the Jake, 2,300rpm is maximum rpm. Jake brake produces more braking horsepower the faster the engine turns. Good Luck, TomC

robertglines1 · September 11, 2012, 12:50:34 PM

I actually wrote it down. Sounds more understandable to me with torque explained. I will probably push over the best mileage /rpm range on interstates. That is to be determined as all I have now is computer figures and estimates. Had rpm at 70 figured once but lost that paper with top overdrive # on 16710Cas. Checking Eaton site to see if I can find it again. Thanks Bob

belfert · September 11, 2012, 01:07:39 PM

Quote from: TomC on September 11, 2012, 12:26:05 PM
As to running the Jake, 2,300rpm is maximum rpm. Jake brake produces more braking horsepower the faster the engine turns. Good Luck, TomC

My experience with the Jakes on my Series 60 is that they may produce more braking power as RPMs increase, but the B500 tranny doesn't like the high RPMs. The transmission will start to upshift at high RPMs making the Jakes less effective. I like to manually downshift just as I crest a long grade so the Jakes have more holding power. Too soon and my speed drops too low and too late and the RPMs will get high enough that the transmission upshifts by itself.

TomC · September 11, 2012, 01:12:12 PM

FRO-16510C overdrive is .74. Good Luck, TomC

rv_safetyman · September 11, 2012, 04:06:17 PM

Here is DD info that may help to sort out how to run your Series 60

Jim

dickegler · September 11, 2012, 04:36:38 PM

Hi Bob, I don't know about the sweet spot, but here's a link to a real handy chart to plot out rpm vs speed in different gear.

http://www.f-body.org/gears/

Dick

robertglines1 · September 11, 2012, 04:44:58 PM

Dick: Didn't think I'd be this slow? I had myself rebuilt in the mean time! Ready to go in now. Thanks for the link! The clearance on the tag axle makes all the difference. Bob

John316 · September 11, 2012, 07:10:01 PM

Sweet spot. Hmmm. 75-80 running with plenty of extra power.

Love the power. Don't think I have driven it wide open too many times. Maybe a few on back roads passing. Takes a bit to gain speed, but we can really move.

Don't have a tach, so no clue on RPMS.

John

garhawk · September 12, 2012, 08:51:25 AM

Hi Lostagain,

Didn't mean to confuse you. What I was attempting to say was that to cruise at my freeway speed of 65 mph the engine must turn around 1700 rpm, with the 740 transmission in final gear.

Yes, the Series 60 will back up to 1400 rpm without down shifting and pull like a tractor but, the bus will not be traveling at 65 mph.

luvrbus · September 12, 2012, 02:55:48 PM

Did you 60 series guys know that a 60 series will put more torque to the rear wheels with a Allison T10,740,B500 or the 4000 series than with manual or auto shift transmission almost a 100lbs more according to Rockwell FWIW kills the old theory about giving up power with a automatic I guess

good luck