High Idle RPM

[JIM CHALOUPKA]

I could use some values of RPM for regular idle speed, and high.

These would be for series 6o model, DDEV III, and DDEC IV.

I am trying to compare the two and see if they have different values.

Just as I was receiving my bus the DDEC III went bad and was replaced (upgraded to a IV). I have no experience of values to determine if my regular rpms of 700 and high of 800 are correct. I have a feeling 800 is not correct.

The tech who did the changeout was employed by Stuart Stevenson and performed the work at Mr. Olivers shop (this may have been a side job) could not adjust the high idle any higher than 800 rpm and just shrugged it off with an oh well they don't want you to idle much anyway.

I stopped into a Freightliner service shop without the bus just to see if they thought they could adjust it up. The answer was yes. Bring it in. I said how high should it be? They said around 1500 rpm. I think that sounds too high, so now I am seeking advice here.

[Joe Cannarozzi]

950 or 1000 on the high side IMO

Your 700 idle speed seems high by 100, IMO

[lonesome george]

Jim,
Ours is a 98 chassis and it goes to about 1000.

BTW I like the spooky looking babe.

[dale farley]

Jim, Mine is 700 and 1000. Fifteen is too high.

[Jon Wehrenberg]

Ditto on the advice of the others. mine is about 650 and about 975 to 1000.

[Kevin Erion]

Jim, why the DDEC 4 instead of 3? I think a 3 gets better MPG and might have some other advantages, but I am not 100% on the other advantages.

[JIM CHALOUPKA]

Thanks all for the come back. I too would like the 1000ish. I think I'll stay away from that particular Freightliner shop though.

George she's there for you, I haven't been able to find her yet. We needed something around here to liven things up. Corona Kelly seems to be retired, and Jerry keeps his college girls to himself.

Kevin, I was told it was the latest and greatest and that the III was history.
Being green at this it seemed plausible, and I was happy I was getting a new one.
My mileage is between 7 & 8 so I don't know if it can be better than that.
I also don't know what it was before. (when Roger had it).

JIM

[rfoster]

Pre ultra low sulphur It got as much as 8.25 mpg with no toad and maintain 62.5 mph or less. Most of the time after they took the good stuff out of the fuel and at about 70 mph 7.12 mpg was the best I could get.

[lewpopp]

Roger, I think you are lying about the 62.5 mph. You never when that slow even with the big J. come on , fess up. Too many giant oysters?

[rfoster]

Pre ultra low sulphur It got as much as 8.25 mpg with no toad and maintain 62.5 mph or less. Most of the time after they took the good stuff out of the fuel and at about 70 mph 7.12 mpg was the best I could get.

[Jon Wehrenberg]

Off topic but I have to agree with the King.

Nothing has changed on my coach except the fuel, and despite the BS from the fuel industry I'm at 7.4 routinely now whereas prior to the fuel formula change I was around 8.0

Those are Pro Driver values and are not affected by my use of the Webasto or generator. Those values are based on 5000 mile averages which is the distance between oil changes and when I reset the Pro Driver so unusual situations such as highly mountainous terrain, or driving on the flat with a tailwind are all averaged out. Most of the time we are towing the Hummer H2, and this last trip to the Keys we towed a Ram 1500 so the mileages reflect a fairly heavy toad.

We also run the OTR frequently.

I can say with certainty that in order of impact on mileage from greatest to the least is terrain, speed, headwinds or tailwinds, weight of the towed vehicle, and use of the OTR. I think towing a heavy vehicle or stacker trailer in mountainous terrain with headwinds would be the worst possible combination for mileage. The best would be a slow drive, with a tailwind on level ground with no toad.

Cold weather decreases mileage, warm weather increases it.

[Joe Cannarozzi]

Surprisingly a head wind will hurt just slightly, crosswinds hurt worse.

Can't ever seem to catch a tailwind:o

[0533]

Why does cold wx make for lower fuel economy verses Hot Wx. I would have said the opposite if I were to guess. What is the cause Jon.

[Jon Wehrenberg]

Just like in our planes our buses burn more fuel when the air is colder and hence more dense. I don't know if the thinner air is offering less resistance, or if the engine is more efficient when the air or fuel is warmer, or if the engine wastes fuel when it is cold out. But my fuel averages on both the plane and bus are better when it is warmer.

I know specifically the plane uses 3 pounds per hour more in cold weather than in summer because I fly lean of peak and maintain a fuel flow relative to peak EGT. I have no control over the bus, but the Pro Driver shows lower mileage in colder temps.