| Author | Message | ||
| Gary Pasternak (Cessna5354)
Registered Member Username: Cessna5354 Post Number: 48 Registered: 2-2007 Posted From: 72.90.9.251 Rating: N/A |
I have a 5C with a 6V92TA with 95 injectors. It was rebuilt 6 years, 15K miles ago. I am looking to reduce the fuel usage and lengthen the life of the engine. I am keeping my speed to 65, down from the 70-72 I initially ran. If I kept a really light touch on the accelerator would I run less fuel thru the 95's thus eliminating the change out ??? Thanks in advance as I have searched this but no conclusions, At least none obvious to my limited grey matter. Hope you all have a wonderful day. Gary | ||
| Luvrbus (Luvrbus)
Registered Member Username: Luvrbus Post Number: 647 Registered: 8-2006 Posted From: 74.32.92.133 Rating: N/A |
Most coach engines are happy with 7G65 to 7G75 a 9G95 is a big injector one other thing you need to tell us what turbo you have blowing the air to 95's 7G65=244 hp 7G70=277 hp 7G75=294 hp good luck (Message edited by luvrbus on February 22, 2009) | ||
| Gary Pasternak (Cessna5354)
Registered Member Username: Cessna5354 Post Number: 49 Registered: 2-2007 Posted From: 72.90.9.251 Rating: N/A |
Hey my bad, I have 9G90 injectors with a TV 7511 1.08 Turbo, as per the Stewart & Stevenson Rebuild reciept. I am running a 5C 35' w/o tags. Probably about 25,000lbs. PO was running between St Louis & Denver with a 4X4 toad. | ||
| Jack Campbell (Blue_goose)
Registered Member Username: Blue_goose Post Number: 121 Registered: 5-2007 Posted From: 67.140.240.129  Rating: N/A |
If it runs like you want it to leave it alone. It would cost more to change the injectors than you will ever save in fuel cost. Jack | ||
| Laryn Christley (Barn_owl)
Registered Member Username: Barn_owl Post Number: 597 Registered: 10-2006 Posted From: 141.152.69.200  Rating: N/A |
Just keep an egg under your foot and you will accomplish your goal. | ||
| Gary Pasternak (Cessna5354)
Registered Member Username: Cessna5354 Post Number: 50 Registered: 2-2007 Posted From: 72.90.9.251 Rating: N/A |
Both last answers were what I was thinking, but I thought there may be a better way, but if I will not see the payback, forget it as has been indicated. No bailout for our Detroits, so it will stay as is. Thank guys. | ||
| Gary Pasternak (Cessna5354)
Registered Member Username: Cessna5354 Post Number: 51 Registered: 2-2007 Posted From: 72.90.9.251 Rating: N/A |
OK let me thinks of this in another manner, If the rack has not been run in 6-7 years, should it ? Also while in there maybe I can find out why the Jakes are not working. I have not traveled out west so no biggie, yet. My PO had said he had them fixed the jakes several times ( receipts substainciate this), but the PO said they did not work for him & still no workie. I am estimating that to purchase, replace the injectors and set-up the rack, it would cost about $1,200 - $1,600. While in there I could investigate the Jakes. Over $ 2K I would never see the payback in fuel reduction. Gary | ||
| Keith Wood (Ft6)
Registered Member Username: Ft6 Post Number: 89 Registered: 8-2008 Posted From: 75.211.234.221 Rating: N/A |
Truck companies in the 1990s experimented with smaller engines, and discovered that a 350 HP tractor burns MORE fuel than a 500 HP tractor, because the guys with big engines got out of the hole and up to cruise faster. Once in top gear, both used about the same amount of fuel, but the small engine was still going through the gears and burning more fuel while the bigger one was already in top gear. Having more engine than you use is better than not having as much as you need. | ||
| David Guglielmetti (Daveg)
Registered Member Username: Daveg Post Number: 1 Registered: 2-2009 Posted From: 71.138.27.85 Rating: N/A |
Have the rack run (kinda like a tune-up) and have the jake heads looked at while they are there...there are some small springs and o-rings that need servicing periodically. The jakes should be checked to see if they are being energized electrically before they go into the jake heads though. | ||
| Clint Hunter (Truthhunter)
Registered Member Username: Truthhunter Post Number: 45 Registered: 1-2009 Posted From: 24.129.235.190 Rating: N/A |
...a simple tack in the shoe has real fast payback on fuel savings. I would concentrate on the Jake repair and decide how much more I wish to spend from there; on 15km on a proper rebuid is not enough to warrant a tune if all is good. If the jake is in the electric control circuit, then you may not even need to open the valve cover. | ||
| R.C.Bishop (Chuckllb)
Registered Member Username: Chuckllb Post Number: 513 Registered: 7-2006 Posted From: 75.211.194.39 Rating: N/A |
Yep... I agree, Clint.  FWIW RCB | ||
| Buswarrior (Buswarrior)
Registered Member Username: Buswarrior Post Number: 1497 Registered: 12-2000 Posted From: 76.69.142.98  Rating: |
It takes a certain amount of energy to move the coach down the road. No matter which injectors, in basic terms, it'll use the same fuel at a certain steady speed. The bigger injectors/higher horsepower just let you dump more fuel into it when you push hard on the throttle, something that you may want periodically! Smaller injectors is the way to prevent a hired driver from blowing the fuel economy on acceleration. I'll take issue with the above theory on fuel economy from bigger horsepower. Faster acceleration takes a lot of energy. The big power plants, when driven conservatively, as in acceleration no faster than the smaller engine, will use the same fuel, where the big power helps is staying in high gear longer up the hill, or not shifting at all, even though it burns lots of fuel to push hard, it burns less than the loss of gear ratio with a downshift in the smaller engine. Big power is also able to pull a higher gear ratio, which burns some fuel, but saves just a bit more by running the engine slower. Calling on all of the big horsepower regularly will empty the tank. A high horsepower engine leaves the economy in the hands of the driver, a lower horsepower engine puts limits on the driver emptying the fuel tanks. Major fleets are loath to leave this kind of control over profits in their drivers' hands. Owner Operators go broke cuz they can't keep their foot out of it once they've become addicted to the power. I'd stick with the injectors you have, continue to moderate your accelerator use and see to getting the jakes working. If running the rack ends up part of getting the jakes working, fine, but I'd leave it alone otherwise. happy coaching! buswarrior | ||
| Gary Pasternak (Cessna5354)
Registered Member Username: Cessna5354 Post Number: 52 Registered: 2-2007 Posted From: 72.90.9.251 Rating: N/A |
Thanks so much for the response as this helps. One more thing I am looking to clarify, I believe now it to be true, that is if the life of a diesel is measured by the fuel run thru it, not the miles, If I can relax, go slower, keep the foot out of it, I would accomplish the same. I will start with the 24V to the jakes and proceed from there. Next time I am in US Coach with the bus they will get checked out. Unless I get more ambitious with the assistance of the board. Thanks all. | ||
| FAST FRED (Fast_fred)
Registered Member Username: Fast_fred Post Number: 702 Registered: 10-2006 Posted From: 66.82.162.16 Rating: N/A |
One problem with the basic DD design is like most industrial engines it was designed to produce a certain HP at a specific RPM. The DD are reasonable at fuel burn between 1200 and 1800rpm and at 60% and above of the engines load rating. Go over the RPM and the fuel burn sucks , in an 8V71 1950 is best you can run , and MAINTAIN NORMAL EFFICIENCY Creating about 16 hp per gallon of fuel burned in an hour. The N60 is whats in most 8V's , Da Book will give the normal injector size for your engine. IF the injectors were replaced to dump more fuel in , the HP of the engine AS set up becomes the guide to stay above the 60% mark. This is why over sized defuler injectors cost more at every speed. Your coach should weigh between 25,000 lbs and perhaps 40,000 lbs, so what works on an 80,000+ lb truck is of little use in setting up for economy. FF | ||
| marvin pack (Gomer)
Registered Member Username: Gomer Post Number: 407 Registered: 3-2007 Posted From: 71.55.228.218  Rating: N/A |
Well after co-driving otr truck/trailer in the hills of Virginia,West Va,Penn,Maryland hauling shavings and peanut hulls to farmers and the such, The tractor had an 8v-92 with 100 injectors. It was used for hill climbing and weight to get the sucker over the top. Under load which was normally 60-80,000 lbs it took it all and fuel was cheaper then also. After checking cost per mile against a smaller engine it was found that the larger injectors gave better averall operating cost. The engine had over 500,000 miles on it before it was rebuilt and then was an in-frame job. Go for the larger injectors and drive it sensibly and you won't be sorry at all. You may lose a little fuel mileage here and there but I believe you will be better satisfied with the results. Gomer | ||
| Tom Christman (Tchristman)
Registered Member Username: Tchristman Post Number: 65 Registered: 1-2006 Posted From: 66.218.33.156 Rating: N/A |
There is a down side to running larger injectors. Because of the retarded timing, you'll never get the same mileage as an engine with say 80 injectors no matter how light you are on the gas pedal. If you drove both buses (a 90 injector, and a 80 injector bus) the same, the 80 injector would get about 1 more mpg because of more advanced timing. This is why buses had smaller injectors-so the engines couldn't get hurt by either lugging or running with your foot on the floor continuously. Any Diesel engine with electronic controls are not affected this way. This is why it is no longer an advantage to buy lower horsepower engines, unless you have no self control-mainly like fleets with drivers that just don't care. Good Luck, TomC | ||
| George M. Todd (George_mc6)
Registered Member Username: George_mc6 Post Number: 739 Registered: 8-2006 Posted From: 64.55.111.6 Rating: N/A |
Gary, How about some info, and we can point you in the right direction for Jake diagnosis. Stick or Auto? DDEC or MUI? Ability to use (and possesion of) a simple voltmeter? Post back, please. G | ||
| Gary Pasternak (Cessna5354)
Registered Member Username: Cessna5354 Post Number: 54 Registered: 2-2007 Posted From: 72.90.9.251 Rating: N/A |
George, & others, Automatic 4 speed 644 (I believe) Allison MUI Own and can handle a Fluke Tom C. You are on to what I thought might be happening, however with the conversion might take 50k miles to break even. Take care guys, | ||
| Tom Christman (Tchristman)
Registered Member Username: Tchristman Post Number: 66 Registered: 1-2006 Posted From: 66.218.33.156 Rating: N/A |
With the lightness of the 5, I would seriously consider reducing the injectors to 80's. This will still give you 295hp and around 900lb/ft torque-still more then a natural 8V-71. Your break even point is 50,000 miles, then after that you're ahead-especially when the fuel prices go back up. Good Luck, TomC |
