10 MPG 6V92 W/HT740

[NJT 5573]

This sounds about right to me. Its posted w/picture at the new silver eagle factory bus gallery sight. It is a 1980 model 10 with 9g90 injectors. This blows me away as I have some DDEC injectors (latest technology BS) and my 6V92 rarely sees 5.5 MPG. Can someone please elaborate if they have found a way to bring a DDEC engine back to the future. How can an engine that is using twice the fuel per mile be cleaner than one that uses half the fuel per mile. I'm not having any luck purchasing a flash from DD that looks to be enough of an improvement in power or fuel savings to justify $500. I think I really do have a boat anchor, can anyone show me how to polish this turd?

[tekebird]

how many miles on your engine? a well running but tired engine can be several MPG lower than a fresh engine.

what tire preasure are you running? min preasure based on wiehgt vs max preasure can be 1 mpg

are you running rib tires or treaded tires?  this probably equates to .25mpg

also keep in mind the way your bus was speced by NJT it likely is geared on the low side they were commuter buses after all

I did a lease to a political campaign over the summer and my 8v71 averaged almost 8mpg......and I drive hammer down on the highway.  this included a fair ammount of secondary road driving  I bet on a highway trip I can  get 9 out of her.

[Eagle]

I doubt the MPG very much.  Unless it has been re-powered it is a mechanical engine as the DDEC came out about 91 or 92.  I have a 85 model 10 with a 6V92TA and 9G90 injectors low mileage and I do well to get 7 MPG.  We can not take one fill up and say we get XXX # MPG as the coach may not be level when you fill or you may not get it completely full.  You need several fill ups to get an average MPG.

[TomC]

To get the most MPG out of your existing power plant as mentioned earlier- have your tires at the proper inflation for the bus weight; run highway (steer) tires all around (most buses do not have enough power to take advantage of lug tires-besides they usually produce noise at speed); check your axle bearings at to proper tightness and switch to synthetic lube; grease U joints; have your engine precision tuned by a mechanic that really knows what he is doing with Detroits (like Don Fairchild); check your gearing-ideally you want the engine turning 1800 at 55mph for a 71 series and 1600 at 55mph for a 92 series-and cruise at 55mph!  You can't possibly get over 6 mpg if you're cruising at 75mph.

The difference in mileages between engines is generally- start with a 8V-71 natural and turbo it or go to a 6V-92TA-should be good for 1-1.5 mpg increase; go to a DDEC 2 stroke or a mechanical 4 stroke-another mpg; go from a mechanical 4 stroke to a electronic 4 stroke-another mpg.  So going from a 8V-71N to a electronic 4 stroke-starting at 6 mpg, you should get about 9.5 mpg.  That's a 50% reduction in fuel use!  So over a 100,000 mile period, you'd go from using 16,670 gal to 10,520 gal-a difference of 6,150 gal, or at 2.75/gal, that would be $16,912.00.  So far NOT enough money difference for an engine change.  If you were to go over 250,000 miles, then it would be at a savings of $42,280.  But remember, if those electronics ever crap out during that time and have to pay for a tow and repair bill, there goes your savings.  Personally, if you have an 8V-71N that is just not enough power, I HIGHLY recommend you do what I did and get the engine turbocharged with an air to air intercooler.  The difference is that I pull long grades at 40 compared to 30.  Just went over the Grapevine northbound, and down shifted to 2nd on the first big pull, where I would have been in 1st before (V730).  Then once at the top of the first hill and back in 3rd NEVER down shifted again through the rest of the pass-where before would have down shifted to 2nd another 3 or 4 times.  Modifying the engine in your bus is always the cheapest to do rather than doing a different engine transplant.  Good Luck, TomC

[tekebird]

Eagle,

are you questioning my mileage?

it is documented and logged mileage over a 6000 mile lease.

I have gotten as good as 12mpg on my 4104 on a trip from PA to  Daytona Beach FL ( all down hill)
heck on a round trip coast to coast I averaged 10 towing my Full size pickup with two motorcycles in it.

tire preasue, tire design, speed acceleration, and a fresh engine all add to MPG.

[Gary '79 5C]

Tekebird,
I won't question you mpg's, But I like sure question Mine.... I run a 6V92 Turbo, with a 4 sp. Allison auto trans. All this in a 5-C. I donot know the size of the injectors, but i believe the former owner had install oversized, 65's come to mind, not sure.
I get 7 MPG maybe, cometimes just below. The engine is NOT a DDEC, and I usually run at 70 MPH up and down I 95. Can't say I idle it often, or run the genset to rob diesel, but I do operate the Webasto overnite, may be 5 galls at most ? ?

Tires are at 95 Lbs.
I have thought of getting a pro look see, from Johnson & Towers here in NJ, also need to get the Jakes operational as well. Although not much need up - dn I 95. I also run thru Pa Tnpke without problems, just back off on the speed at the mountains peak.

I would love any suggestions to improve the 7 MPG, from Tekebird or others.

Thanks,
Gary
P.S. Nick, you are much taller in person.... Very nice to meet you Saturday, Thanks for taking the time.

[tekebird]

I think part of your problem is the auto.....and doubt you will get better due to that.

My Auto is a 6 speed which should shed some light on the reason for my mileage....I forgot to mention that......and the fact that the engine only has 160k on it from new ( not rebuilt)

Over sized injectors will probably be another decline in MPG......although I couln't guess how much,

For the tiny bit of extra power it gives I bet you loose 10 times in lost economy

When new guys come arounfd and ask about 4104's on the board, everyone says oh they are slow and don't have any power.

Hardly the full truth....sure a worn out one doesn't have any power...then a worn out series 60 doesn't either.  My 04 has no problem keepoing up with traffic on any east coast grade.......with that said, yep the first step of the grapevine, Donner Pass, Cajon Pass Vail pass etc are 2nd gear pulls........but they would be in my dads 08 or my MC-8 as well.

all in all it doesn't really add up to lost time.......I have done the exact same cross country trips in my truck and my bus towing the same truck has no real mentionable extra time, maybe that is made up at fuel stops, I don't know......

Only thing I might suggest is Propane injection...that will add some power and some economy...but will cost you for the kit and propane.

[Gary '79 5C]

Tekebird,

I looked right past the obvious as well, the trans, When I was looking for a conversion I really was looking for something with a 10 spd RoadRanger or the like. But then I saw the resale of these coaches was 10K less than with an auto, I said that I would take the convience of the auto.
The engine I have was rebuilt in Denver by DD, 12K miles ago. Runs strong all day long without using oil, or at least the slightest bit. The guys at Lukes cannot believe how little usage.
I might investigate the injectors installed. I think it wsa on the rebuild invoice. If not I will check. The former owner ran between St. Louis to Denver with a Large Jeep in Tow.
I might not need the power availabil with the large injectors I will have to look at the cost of replaceement and paybacks...
I run now at 70 MPH without problems. The 6 spd tranny as you have would be Cat's Moew, but that will wait until I have more time under my belt and am in more need of a trans replacement.

Thank  for your insight and quick clarification. Never thought of the biggest contricutor to milage.

Stay warm, healthy, and such.
Gary

[tekebird]

I bet dropping speed to 60 will give you a MPG as well