Then your vehicle is to be driven either in western Texas, or on the German autobahn.... if they catch you in Illinois running that fast, you're cooked...
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- Thread starter pwrwagn
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Then your vehicle is to be driven either in western Texas, or on the German autobahn.... if they catch you in Illinois running that fast, you're cooked...
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paullud
Veteran Expediter
So how do you make an engine work harder, burn more fuel, increase wind resistance but still end up burning less fuel?
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WanderngFool
Active Expediter
Are you calculating your mpg "at the pump"? Dashboard readouts are notorious for being optimistic.
At the pump is the only way that matters.
At the pump is the only way that matters.
At the pump, of course. I don't even have an EVIC.
by being so much more efficient it overcomes the load change.
flattop40
Expert Expediter
And why would wider tires give better mileage
The tires were not wider they are taller. The circumference is increased therefore you travel further per revolution.
WanderngFool
Active Expediter
Thanks for posting your spreadsheet. It doesn't help me personally because I took a different approach a long time ago and I'm not about to revamp but I'm sure you gave people ideas.
And I didn't even know it was possible to upload files to the forum. Good to know.
245/265 is tire width
flattop40
Expert Expediter
Without getting into all of the math. A tire that is 265/75r16 will have 24 1/2 less revolutions per mile than 245/75r16 hence the optimism of better MPG.
Utah's good, so is Wyoming and Nebraska. Montana's good, too.
The other day, I followed a cop out of town on the Illinois Tollway. 74 in a 65. And he was getting passed. I don't know what speed enforcement is on the tollway, but it seems to be inconsistent. That being said, I have a near spotless driving record and want to keep it that way.
paullud
Veteran Expediter
That wouldn't change anything other than you were driving faster and burning more fuel.
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Actually, it changes many things...
Boost, turbo geometry (variable venturi turbo), timing, egr amount, number of injections (common rail diesel), all due to rpm and load change. I believe this engine is, for emissions purposes, horrendously detuned, especially at lower rpm's. That's why my fuel economy is so bad in the first place. This thing should be getting 30-35 mpg @ 55 mph - or better - due to low weight and size. My estimated curb weight is 3700 lbs. Also, the engine was originally designed for european diesel, which is has a legal minimum cetane rating of 46, while ours is a pathetic 40. This has a very dramatic effect on starting and economy.
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You forgot MAF and intake temperature. Every TDI engine has all of those things. That still doesn't change the physics of increased rolling resistance with increased speed, and increased wind resistance and drag with increased speed, both of which require more power to push the vehicle down the road.
The European (EN 590) minimum cetane index is 46, and a minimum cetane number of 51. That engine, just like the Sprinter engine, was designed specifically for a minimum of 50 cetane. In North America (ASTM D975) the minimum cetane number is 40, but it's rare to find diesel in the US that's below 42, and it's usually in the 42-45 range. Canada is mostly 50 cetane. California CARB diesel is a minimum cetane number of 53.
It's not that hard to find 50 cetane in America, and if you can't it's easy enough to bring low cetane up to 50 by using Power Service which gives a 4-6 cetane boost (depending on which one you use - the anti-gel white bottle boosts 4, and the gray bottle boosts 6).
A minor point, because I know what you're saying, but a turbo diesel injection engine doesn't have a throttle. The fuel fed to the engine is computer controlled, based on a plethora of sensor inputs (which becomes incredibly annoying when the engine goes into limp home mode). It does, nevertheless, require more power to push a vehicle down the road at 75 MPH than it does at 60 MPH. And it is also true that once you reach a cruising speed it doesn't take all that much power to maintain that speed. But what he's claiming is the turbo boost, EGR, intercooler, air mass, timing and fuel rail are all working in concert to actually burn less fuel at higher speeds. Basically, by increasing the turbo boost it allows for less fuel to be injected by the fuel rail, resulting in better fuel mileage at higher speeds. A TDI certainly burns less fuel at a given speed than a non-TDI, but it won't burn less fuel at 75 than it will at 60. It can't, regardless of how much boost pressure there is or timing or anything else. It could in a vacuum, where there is no wind resistance, and if you had zero rolling resistance on the tires (which increases with speed, BTW), and if you had frictionless wear parts.
It seems everyone wants to argue... Not only is it possible, it is reality.
How's it happen? It works like this:
At 80 mph, the motor runs about 2400 rpm.
At 60, it runs about 1800. There's something called "BSFC" or "Brake Specific Fuel Consumption". It's the precise amount of fuel required to produce 1 horsepower, expressed in gallons power hour, liters per hour, etc. It is the absolute amount of fuel required to produce one horsepower for one hour. I have seen BSFC maps that showed LESS fuel consumption at double the horsepower, by changing rpm and throttle.
And not only have I verified it through actual measurement (miles and gallons burned) repeatedly, so have others who own the same vehicle. But NOT ALL OF THEM HAVE THE SAME EXPERIENCE. Modified CRD's do not. There are many things in this motor that can vary efficiency, and they have to do with accuracy of assembly - including cam timing, and there's at least more than 1 computer program for the same motor for the same year and same vehicle.
It can actually take MORE fuel to produce less horsepower at 1800, if the engine's detuned badly enough, compared to 2400.
How's it happen? It works like this:
At 80 mph, the motor runs about 2400 rpm.
At 60, it runs about 1800. There's something called "BSFC" or "Brake Specific Fuel Consumption". It's the precise amount of fuel required to produce 1 horsepower, expressed in gallons power hour, liters per hour, etc. It is the absolute amount of fuel required to produce one horsepower for one hour. I have seen BSFC maps that showed LESS fuel consumption at double the horsepower, by changing rpm and throttle.
And not only have I verified it through actual measurement (miles and gallons burned) repeatedly, so have others who own the same vehicle. But NOT ALL OF THEM HAVE THE SAME EXPERIENCE. Modified CRD's do not. There are many things in this motor that can vary efficiency, and they have to do with accuracy of assembly - including cam timing, and there's at least more than 1 computer program for the same motor for the same year and same vehicle.
It can actually take MORE fuel to produce less horsepower at 1800, if the engine's detuned badly enough, compared to 2400.
At Chrysler, that department should also handle blinker fluid and brake lube.
Wow. I became a diesel injection tech back in the late 80's. I worked at that until 2000.
If you think I'm stupid, then I've never been so insulted in my life. If you think I'm lying, same thing.
Either way... Apparently this little club of insiders doesn't want any outsiders.
If you think I'm stupid, then I've never been so insulted in my life. If you think I'm lying, same thing.
Either way... Apparently this little club of insiders doesn't want any outsiders.
I don't think you're stupid, or that you're lying. I just think you need to contact Chrysler and give them your data. They make millions of dollars every time they can squeeze another MPG out of a vehicle, so they'll want to see your findings, I'm sure.
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