musing about fuel savings

You would have to do the airflow analysis to convince me. Even though it looks as if each injector squirts its entire load of fuel into one and only one cylinder, I doubt that this is the case. What you would wind up with, is either a super-lean mixture every seventh cylinder, and that can't be good, or unburned fuel shot out the tail pipe. You have to have a means of bleeding off compression, and blocking the intake, maybe the exhaust, when you don't want a cylinder to fire. This makes it a lot more complicated, than simply reprogramming the ECM. In other words, a multi-displacement engine has to be designed from the ground up, in order to fulfill its intended purpose.

What you could do, is get a four cylinder Jeep like I have, install a less restrictive intake and exhaust, and learn to drive wide open throttle like I do. This would get you up to 25 mpg, which will be a lot better than what you get now. I didn't say you shouldn't have a Jeep for the mileage, but I got pretty close. You need to get rid of that six cylinder thinking.

Turbo City was working on a Jeep 4 cylinder turbo kit, but they abandoned it because of lack of anticipated demand. There are available supercharger kits for the 4 cylinder. Those are two ways of getting the same effect as multiple displacement. Another trick is to get the engine race-balanced and install forged pistons, so it can handle a couple thousand more RPM without getting hot oil and shrapnel all over your windshield.

Earle

DougW proclaimed:

Except for the ones that flip a cam such that the hydraulic rockers no longer function on the disabled cylinders, e.g. the 5.7 Chrysler engine pretending to be a Hemi.

This has been used as an electronic rpm limiter on some sports cars, rather than just shutting the engine down or cutting power which could result in a rather nasty accident, the EFI would start dropping fuel to one cylinder and rotate that droppage.

Real Jeeps don't have alternators, radio amplifiers, or off road lights

(I felt compelled to throw this in)

Been experimenting with exactly that. I used to get 19 mpg/US gallon at a carefree 75 mph and over the last 640 motorway miles, I have averaged a little over 24 mpg/US gallon at an "eggshell on the throttle peddle" 60-65 mph. I was almost impressed with the TJs fuel consumption actually.

Dave Milne, Scotland '91 Grand Wagoneer, '99 TJ

.. should have mentioned that I also upped my tyre pressures to 30 psi on the motorway which does feel better.

Dave Milne, Scotland '91 Grand Wagoneer, '99 TJ

A real Jeep might have a generator you mean. Alternators didn't appear until the 60's did they?

I know of shops here in Toronto Canada that will wind anything and sell just brushes or diodes, etc....

I did the XJ's starter recently. It had me worried though, it dragged for a bit until the brushes wore into the old center slabs but now sounds normal.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's

"L.W.(ßill) Hughes III" wrote:

And yes, no Real Jeep uses a volt meter, all that tells you is the> state of your battery, not whether you're charging seventy amps and> using a hundred, like the amp meter will show that exact measurement in> discharge.

Yes, Of course back in the day vehicles did not need much power other than for the ignition and the sad headlights we had back then.

I had a couple cars without radios other than a transistor propped against the windshield. My first car radio was an Delco AM model with tubes and a built in speaker scavenged from a junkyard for a couple dollars.

The kids nowadays don't know about that stuff though..

Good analysis, Earle. Simplest way to test the theory would be to pull one plug wire and see how you like it .

As I am sure you can attest, the I6 is marginal above 10,000 ft. anyway. Heck, 5th gear is useless without a 2% or better downhil grade and/or a stiff tailwind.

Someth> You would have to do the airflow analysis to convince me. Even though it

Dave, how much of that fuel saving was attained by the impatient SOB on your bumper so close he was actually pushing you along (or the air pressure from his horn as he tried to speed you along)?

I got bored one day and ran a quick anaylsis of the drag effect of a

6x6 flat surface (fair aeordynamic representation of a Jeep). Just figuring the total pressure was interesting. Air pressure varies with the square of the velocity, at least for the speed range we are talking about, so your results come pretty close to the energy difference between pushing that 6x6 sheet of plywood at 65 vs. 75 mph.

I got similar results > Been experimenting with exactly that. I used to get 19 mpg/US gallon at a

Well ya know, if that would work in the slightest degree, one of the makers would have tried it eh.......

Figure what the engine runs like with one plug wire off and just figure on that power hit once every 7 shots. Shutting one cylinder down on a conventional engine just doesn't work and Caddy proved shutting down cylinders works for shit.

I hear the new crippled Hemi, that has no right to that name has a serious power lag while the computer thinks about what cylinder to fire when it is new and it is 'fly by wire' with no cables, imagine when it ages....

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's

DougW wrote:

Well, no impatient SOBs actually. The truckers here are a lot slower than in the US, doing 55-65 mph, so if you are polite and flash them to let them know when they have over taken you enough, they give you a friendly wave or left-right-left flash of the indicators. Your truckers are downright scary when you are in a jeep doing 80 up a hill... and can only see the letters "AC" of "Mack" in your rear view mirror :-).

Dave Milne, Scotland '91 Grand Wagoneer, '99 TJ

Yes but real off road vehicles don't have.....spark plugs.

MANY shops rewind Generators, look in Hemmings.

Having an ammeter AND a voltmeter is nice. Like having a thach and a manifold pressure gauge, or a coolant temp and coolant pressure.