piscator wrote:JimC wrote:Seth, that's certainly dreadful fuel economy in your diesel vehicle. My 2 litre Forester diesel 4WD averages 6.7 litres per 100 km, which equates to 35 mpg, even better on long trips to the outback.
I think the main reason why the Audi process might be important in the long run, when an oil shortage eventually occurs, is that it will support what will be a large number of "legacy" diesel powered transport until other technologies mature.
Is Someone talking about his 5mpg F450? The one he burnt up letting his EGT go too high because he didn't know to downshift his non-intercooled truck when pulling a load up a grade?
No, that was the Hummer, which ruined the engine because there was no EGT gauge at all, so when hauling up a grade at high altitude (since the truck was tuned for sea level originally) it over-fueled even in first gear and overheated the #8 cylinder, a typical problem with the 6.5 GM diesel because of a faulty cooling jacket that didn't have a crossover pipe at the rear of the head to keep the rear cylinders properly cooled. I was one of hundreds of people who did the same thing. After that I installed EGT and tranny temp gauges instead of the idiot light that prominently announced that you've already blown your engine.
Or perhaps you were referring to my 98 Dodge diesel pickup, which had a serious design flaw which is that the transmission torque converter did not lock up in first or second gear, it only locked up in third gear or higher. Again, there was only an idiot light that came on AFTER you'd fried your transmission trying to pull heavy loads or up hill in first or 2nd gear. Dodge didn't tell anyone that the tranny was not designed to lock up in first or 2nd and many trannys later they switched to a different transmission altogether that DID lock up in low gear. After the first tranny, which was replaced under warranty, I installed EGT and trans temp gauges and it never happened again.
The F-450 has pulled anything I have ever hooked it in a very civilized and professional manner, and it has never once so much as overheated the coolant, much less the tranny fluid on a miles-long 7.5% grade pulling at 34,850 gross combined. I love the Ford's ability to tow anything. It just gets really lousy mileage.
Not representative. Truck's geared to the ground and owner doesn't understand he needed a $1700 splitter for double OD if he wants fuel mileage on the highway with 4.88 or 5.10:1 gear ratio.
Already has a tow mode and overdrive. Yes, an aftermarket overdrive would be nice, but I couldn't put one in while it was under warranty because it voids the warranty, and since it just went out of warranty two years ago (timed out, not mileage) and I didn't use it that much, I didn't bother to install one. I could, and I could install a drive line retarder too, but I've found that the Ford's own automatic Jake brake works very well on downhills and I've never needed a drive line retarder. As for an overdrive, if I drove it all the time that would be on the agenda.
That same truck would get 20mpg unladen and 10-12mpg pulling a 36' fifth wheel at GCVW with a US Gear tail unit and effective 0.8:1 double OD in the Big Hole. Ford's engineers had unrealistic design constraints they had to compromise to meet 50-state passenger vehicle emissions requirements and the demands of the bean counters to build the heavy duty trucks on the same lines, so they designed a truck that would self-destruct if you drove it on the highway. Normal US highway speeds have the engine tach'ed out close to 3000RPM with those short gears, and the engine was not designed to spend significant periods above 2500RPM, with or without intercooling. Look at the engine's torque and horsepower curves.
I must disagree somewhat. My truck runs just over 2200 RPM at 75mph and it is intercooled. I can't remember exactly, but I think it has 4.88:1 gearing. The real bitch is that it's computer-governed so it won't go more than 80 mph under any circumstances. I had to buy a diesel programmer just to turn off the computer governor. It also has some nice features including tunes for economy, towing, high power and racing, which will add more than 150HP. I use the towing program with the governor shut off because that program automatically reduces power if the EGT exceeds programmed limits, which keeps you from burning up your engine inadvertently.
The combination is enough to provide authoritative acceleration for this four-ton vehicle, and makes light work out of any typical hauling and towing. The gearing that doesn't allow much boost to build in the first couple of gears when the truck is empty, but at highway speeds, the engine is right in the meat of its powerband in fifth gear - an absolutely perfect setup for full-time towing. The Tow/Haul mode makes for perfectly-timed up- and down-shifts, and greatly reduces the need to use the service brakes while decelerating.
Source
Someone should have deleted his cat and mufflers
First, it's a federal crime to tamper with the emissions system, so I'd never do it, and even if I was tempted to do so, I couldn't do so until it was out of warranty.
while increasing the diameter of his exhaust pipes, added a splitter, and intercooled his engine. The $2500 would have doubled his fuel mileage and doubled the life of the engine in the $30,000 truck.
30K? New? No, more like 64K. Worth between 30K and 38K today.
If I decide to go mobile full time I might look into mods, but outside of the failure of a gasket that pumped all the coolant into the cylinders just outside Fort Knox that took two weeks to fix, and a faulty radiator, and a few other minor gripes, all of which were repaired under warranty, it's been the best, most trouble free truck I've ever owned...except for the mileage.
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While we're talking about trucks...
Maximum allowed grade on the Eisenhower interstate System is 7%, and must be less than Critical Length of Grade, as trucks can't force downshifts.
The approach grades are steep, being 7 percent on the west approach and 6 percent on the east approach. Source:
CDOT
My bad, I thought it was 7.5% on the west side.
Their 9/10/13/15/18-speed transmissions are not "Synchronized" like your passenger vehicle. Even if the driver tries to downshift with the clutch engaged, the shifter will just grind if the engine RPM is not within a narrow range, and he'll have to find a higher gear with no engine braking.
If a big truck doesn't select a low enough gear at the top of a big hill, he can't brake down to a reasonable speed when his load starts pushing him down the hill because his air brakes generate too much heat and his wheel rims will heat up and burn the beads off his 125psi tires, which will blow them off the rims in the next curve if it doesn't do it right then.
The solution to this is either crawling down the hill, or a Jake Brake, which opens the exhaust valves during the power stroke of the the 4-stroke evolution. This means the engine uses the truck's inertia, transmitted through the drivetrain, to compress air and make noise instead of the engine using fuel to compress air and make noise and transmit force through the drivetrain in the other direction. A Jake Brake may well have saved all of our skins at some time during our lives, as people don't go around thinking about the amount of inertia a moving 80,000lb object contains, and credit them with the same confident nimbleness they feel while driving their Mini Coopers and clapped-out Jettas.
There are two runaway truck ramps on the west side that get used fairly often. Speed limit for vehicles over 30,000 gvw is 30 mph.
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