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Old 06-10-2008, 11:10 PM   #21
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Re: building a fuel miser bus.

An interesting point I learned from Tim at United Truck Body is that new buses are all coming with 5 or 6 speed Allison overdrives with lockup on the converters. These transmissions are leaps and bounds ahead of the AT545's and even MT643's when looking at mileage capability. So what do they do? They put lower gears in the axles so they spin the same RPM's with the overdrives as the old direct transmissions. This is to aid in getting the buses moving easier and faster, but doesn't do much for mileage. But new buses ARE getting better mileage. I think a lot of that has to do with the huge advances in electronics to control the engines. I still firmly believe the most advanced diesels are a solid 10 years behind modern gas engines in terms of computer controls, but that also means there is a lot of hope for the future.
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Old 06-11-2008, 01:02 PM   #22
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Re: building a fuel miser bus.

the newest generation of ACERT tier 3 & 4 engines are right on top of the electronicly controlled / managed engines, they are required to meet strict air quality and emission laws by California Air Research Board(CARB) as well as federal EPA standards. The electrionc diesels are capable of sensing a loss of 2 mph while in cruise controll mode and automatically changing the calibration to increase HP by as much as 50% to maintain the preset highway speed, as soon as the power is no longer needed it returns to the lowerpower rating to conserve fuel comsumption and lower emissions. I think that that is comparable to or better than the management systems available for use on gas engines. Well actually very comparable when you consider the mechanical differences between gas and HD diesel engines.

the electronic management systems are in place/production today, It's just not old enough to be affordable for us in todays market, in 10 years or so when these buses are affordable we will all be buying the technology because it will be all that is available.

In the meantime remember that the torque converter on an automatic causes at least 10% power loss or inefficiency so a manual trans or lock up converter are desireable as well as a gear ratio that lets your engine develop good torque at a low rpm while runnung down the road at a reasonable speed.
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Old 06-11-2008, 01:59 PM   #23
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Re: building a fuel miser bus.

But OBDII cars are capable of sensing a misfire by a minute change in crankshaft speed at 6000 RPM. This means they can see that one cylinder out of 8 might not be firing to its full potential and causing the crankshaft to "slow down" 100 times per second, thus setting the malfunction indicator light. That's pretty darn impressive if you ask me!

It will be interesting when these newer, more expensive buses start hitting the skoolie market. I'm pretty comfortable working on my old mechanical Bosch-injected engine because it is so simple. I don't know what's going to happen with a new, more expensive one. I am going to end up buying a Genisys update with medium duty truck infor on it BESIDES the cars? Oofda! That could double the price of a bus!
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Old 06-11-2008, 04:30 PM   #24
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Re: building a fuel miser bus.

the tier 3 engines are firing the injectors multiple times during the power portion of the stroke to maximize power and minimize polution, it's the same technology that works as fast as the electronic guru's can make it happen, lets remember that electrons move at .95 times the speed of light.
in 95 or 96 i ran durability tests on a navistar 7.3 burning CNG, it used Volvo coil on plug ignition in the injector holes, Detroit Diesel DDEC electronic controls from the 8v92 series diesels and was firing the plugs multiple times and capable of changing ignition timing 25 degrees between cylinders in the firing order depending on feedback from knock sensors, and exhaust temps. The calibration engineer was working with me one afternoon and I asked how much power was available and he doubled the torque with a few strokes on a keyboard just to show me that the calibrations we running were conservative.
Just a quick history note,ford bought their basic electronics management system fron NASA, GM's system came from Ross Peroit's EDS.Cat and Navistar developed the HEUI injection/management system jointly,Bosch is the godfather of electronic fuel injection dating back to the 60's and they still hold licenseing rights to electronic injectors worldwide.
Neil Armstrong went to the moon and back with less computer power than a 1985 chevy has onboard.
Electronics has and will continue to change the way we think and do things, is it better? I'm not always sure, but it is the way of the future.
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Old 06-12-2008, 12:44 AM   #25
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Re: building a fuel miser bus.

From my limited experience with electronically crontrolled diesels, one needs a communication adapter with the software hooked-up to a laptop to change an injector (to set up proper fuel rate). At work, Cat charges several thousnd dollars for this stuff. Hopefully, when these buses hit our market we will have cludged all this together (of course, I'm at the end of my electronic-software rope already).
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Old 06-12-2008, 01:27 PM   #26
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Re: building a fuel miser bus.

Quote:
Originally Posted by bus-bro
From my limited experience with electronically crontrolled diesels, one needs a communication adapter with the software hooked-up to a laptop to change an injector (to set up proper fuel rate). At work, Cat charges several thousnd dollars for this stuff. Hopefully, when these buses hit our market we will have cludged all this together (of course, I'm at the end of my electronic-software rope already).
By the time that we can afford these busses they will have been thourghly debugged and aftermarket chips, programs and adapters will be available just like hotrod electronics are available for gas engines and light diesels in pick ups. The creative minds that develope this technology are serious motorheads, their employers know that part of keeping these people happy at work includes acccess to facilities and equipment far beyond what is affordable to a private individual and allow their facilities to be used after hours for government projects.
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