Convert 4.3L Chevy V6 to carb?

I am getting 45 mpg with a stock 1999 Honda Civic, with mechanical tappets, FI, and no hybrid technology. According to the Nevada State Patrol, it can do 125 mph too. I think that you could compare that to your first Willys car with its 30 mpg and a top speed of what, 70? There are other things holding the TJs back than the FI. Inappropriate axle gearing for example. In fact, you could take your stock 4.0, put 4.11 or 4.56 gears in it, forget the headers and the carb, and blow the doors off your CJ7s and early YJs.

Earle

Ever been inside one of those things? If so, 'nuff said.

Earle

Practically every passenger car manufacturer is claiming at least forty miles a gallon now, with at least one model, thanks to electronic fuel injection. They could do better too, but they don't need to as yet.

Earle

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Basically you are totally wrong... FI help with emissions by supplying fuel in a much more precise manner than carbs, FI can run much leaner and stay closer to the ideal air/fuel mixture (ideal for power AND fuel use) throughout the range you use a vehicle in. This means you get more complete combustion, which means more bang for the same amount of fuel, which means more POWER AND better MILEAGE.

You don't get one without the other

Properly set up FI will supply fuel close to the perfect ratio whether

9000 feet above sea level in 30 degree temps or at 0 feet 100% humidity and 120 degrees. Based off input from an o2 sensor. On the fly in real time.

Carbs use a very primitive and extremely complicated failure prone set of mechanical devices to derive ONE unchangeable (until you stop and replace jets) fuel map that has to suit the vehicle under a huge set of variables.

I mean there isn't even a debate here, no matter HOW MUCH of a tuning wizard you are Mike, you will NEVER tune your carb as well as a computer can keep FI tuned... by the time you leave your driveway your air/fuel ratio will be less than ideal, a computer will have compensated and corrected the ratio 30 times before you left the same driveway.

O2, engine temperature, air density/flow, air temp, lots of sensors actually.

Computers have allowed car companies to play with not only the power but the emissions. Most FI cars never reach peak power because they were tuned to meet emission standards. That's why aftermarket chips and mods can find so called "lost horsepower".

Carbs are tricky buggers. They like stable humidity and temperature to stay perfectly tuned. Race cars that ran carbs were a fine example. Tuning based on temperature and humidity, trying to guess if the air would be cold or warm up by race time.

However, FI can run at angles that give carbs fits. Carbs can run on fuel that would kill an injector.

My cat likes trout feast.

etc.

Back then, nobody cared. The VW Bugs were getting about the same, but with a gas tank that basically sat in your lap, "stale air" heat that came right off the cylinders, no cam bearings and a carburetor that you could rebuild and tune blind folded. I think that test run was done on an oval track, too.

Earle

Bill,

Don't these things basically run at full load all the time? This means that they will have a much more limited range of operating parameters than any street use car, and over this limited range more primitive carburetor technology will be more appropriate. I don't imagine that they worry too much about economy or emissions either. ;^)

Earle

Great in theory, too bad real life proves it otherwise.

Why does a FI system need a fancy new chip to get more power and they warn about way less gas mileage?

LOL, got news for ya....

Here is my last tuning experiment with my carb 258 engine with the emissions computer gone and 'no' catalytic converter in the exhaust stream.

On the ASM 2525 test:

I got 589 NOx, 16 ppm HC and 0.11% CO

But but but, my Fuel Injected 4.0 Cherokee with a fresh tune up and a new O2 sensor got:

HC for the Cherokee was 58 ppm, CO for the Cherokee was 0.56%. NOx wasn't recorded.

So much for theory, eh....

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's Canadian Off Road Trips Photos: Non members can still view! Jan/06 (More Off Road album links at bottom of the view page)

There is a product out there, that sports a "power" program and an "economy" program, all on the same chip. I think it is for the Chevy 350. There aren't more of them, because of lack of interest. Maybe gas prices are now high enough to change this. Stock FI programs run slightly rich on purpose, to lower combustion temperature and reduce NOx. This produces more HC and CO. It is also one reason that a less restrictive intake and exhaust will give you both better economy and more power, when added to just about any stock FI vehicle, and without burning holes in the tops of your pistons.

Earle

Bill,

I am talking about partial throttle operation, such as I use when driving where I live. Now in Southern California (I have been there but I avoided rush hour) a big carburetor on top of a rat motor might be more appropriate. ;^)

Earle

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Sure, they would if the rules allowed them. FI is prohibited in Pro Stock. Now take a look at the Outlaw Pro cars that have a choice of carb or FI, and they are running FI.

Chris