Why dont Jeeps get better gas milage?

i..have..a..08...jk4dr..get..18..around...town..with..upgrades..luv..it..

writesoon!

With modern 3-way catalytic converters, they only function properly when the Air / Fuel ratio runs at stoichiometric (no excess air, no excess fuel). That's why these vehicles have O2 sensors to trim the fuel injector duty cycle.

Carburettors don't do a very good job maintaining this level of F/A control. On the other hand, carbs can be set to run leaner than stoichiometric which gives better fuel consumption (so long as they aren't set to run so lean that you have driveability problems). With accelerator pumps and power valves, carbs can run richer under load or acceleration and still operate lean at cruise.

But, do you remember some of the cars from the early 1980's with their miles of vacuum lines and complicated fuel control systems? Remember what poor power they gave (5.7L Corvette motors at less than 200HP!)... fuel injection, good intake manifold and cylinder head port designs and new combustion chambers improved power a great deal. Return to carbs? No way. Look at the power and driveability improvements when Jeep went to the HO 4.0L engine.

While true that CAFE gives the auto makers a great incentive to have better fuel economy, failing exhaust emissions is an even bigger problem.

reboot

"DougW" wrote How's THAT for a basic mods list.

Missing the fuzzy dice.

Cant they smooth the aerodynamics down some so that better gas mileage would result?

I'm just proposing some small changes that could really make them more efficient

So can fuel injection. Someone who knows how to hack the chips can give you any fuel-air mix you want. It's just not something you can do by diddling a few controls under the hood.

But three way catalysts need to run a little bit rich.

Which fuel injection can also do.

Yeah, they were trying to turn a carburetor into fuel injection.

Once again, there's no tax on emissions, it's go-no go and done on a brand new car. The EPA doesn't drive cars 50,000 miles to make sure that they hold the settings and if they don't hold the settings the manufacturer's liability is to fix them, not pay a tax.

If the issue is that the fuel injection is set to make a 3-way catalyst happy the issue is with the 3-way catalyst, not the fuel injection and if it's really all that important to you I suggest that your best solution is to become a scofflaw, toss the catalyst, and have someone burn you a ROM with whatever fuel-to-air ratio you think is appropriate.

Some of the newer systems can even be remapped if you have the correct software. Other options include changing the reference voltage presented to the MAP sensor, or making subtle changes to the O2 sensor response.

Or you could just rip out most of the computer and build your own...

Even if you don't, that site has a lot of interesting reading.

Now that looks like fun.

You'll lose your fold-down windshield (if that hasn't happened already).

Then you wouldn't really love to have a CJ.

Only if the laws of physics are overturned by the supreme court.

Claims incompatible with desires. Low gearing for crawling, aerodynamics that would make a brick blush for starters.

I hear the CRV is fairly aero.

"Kate" ...

Yep, if you look at the grille you will notice that it is now slanted and the windshield is more raked back. Further unbrickifying and you don't have a Jeep anymore. Tomes

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I don't have one but the folks that have Prii (the plural of Prius) and are obsessed with mileage maximization use these a lot. If you peruse the Prius groups around the net you can get useful information on how they are used. Tomes (

Yes it is, and that is indeed the point of it all, isn't it.... Tomes