poor mpg with weber

4x4moose · December 23, 2006

ok i'm getting around 16-20 mpg with a weber on my hach. i have been told by many people that i shouldn't be getting less then 25mpg. i uped the jet size from 60 to 80, do i need to go bigger? the plugs are showing me that i'm running rich. my timing is advanced all the way and there is no pinging going on running 87octane. that choke opens and close correctly. any body have any ideas. new plugs/wires/cap/rotor. dose the stock fuel pumt put out to much psi for a weber?

Snowman · December 23, 2006

Wouldn't the larger jet size be giving more fuel, causing rich running and poor fuel economy?

GeneralDisorder · December 23, 2006

What jets did you change? Default jetting for an EA71/EA81/EA82 is as follows:

140/140 mains

170/160 air bleeds

F50/F50 emulsion tubes

50 idle jet(s)

My crystal ball tells me you have a Weber with two idle jets and you changed from 60's to 80's? That will effect ONLY the idle mixtures. You need to change the main jets and air bleeds to correct your mileage problems.

Also are you lifted? My wagon with a perfectly tuned weber runs about 20 to 24 MPG give or take. Same Weber it had when it was 2WD and getting 32 MPG. Lifted rigs just don't do well on the mileage end due to the gearing, and the rolling resistance of big tires.

GD

4x4moose · December 23, 2006

no i'm not lifted, i wish i would take the time to put my lift on. were would this other jet be located? i changed the on on the front of the carb. i believe i change the air jet, there for more air.

GeneralDisorder · December 23, 2006

Idle jets are on the front and back of the carb, and are the only ones accesible from outside the carb. To change the main's and air bleeds you must remove the top of the carb, and unscrew them. The mains are in the bottom of the float bowl, and the air bleeds are on top between the the bowl, and the air horns. The smaller of the two barrels (the one with the throttle linkage attached to it) is the primary, and should have the 170 air bleed. Secondard should eb 160, and the both mains should be 140.

And put the 60 idle jets back. Those are fine. 80 is much too large.

With the correct stock jetting I get 28 to 30 on my sedan, and about the same on my Brat when it was carbed.

GD

4x4moose · December 23, 2006

so go smaller on the mains? or larger on the airbleeds? or a combo?

GeneralDisorder · December 23, 2006

Order the CORRECT jets. It's not a matter of smaller or larger. Just go with the default jetting and you will be fine. Don't try to mix and match stuff - you'll just end up worse off unless you really know what you are doing, or have a wideband O2 setup to tune it with. Take the top off, see what you have and go from there. Order what you need to make it right. I have never had a problem with the above mentioned jetting on any EA series engine.

GD

daeron · December 23, 2006

GD knows his stuff, and has done his best to put the information you likely need to rpair your carb in the briefest terms possible.. just basically set your carb up the way he says, and you should be running great.

Not trying to kibbitz, just adding support for his advice.

chef_tim · December 23, 2006

How about a picture to help you out.........

http://www.racetep.com/weber/32_36DGAVEV.pdf

That is as good a pic as they get. HTH, Tim

HATCHY · December 23, 2006

I have a good idea Why. I have a brand new redline, I got poor gas milage too.. Because I never let the secondary close:lol: That had alot to do with my mpg.hahah

bratsrus1 · December 23, 2006

Hey 4x4 This is Jerry, you need to take your car to AA carb shop in Yakima he knows weber carbs like the back of his hand. I have a weber on my hatchbrat and i tryed everything i could think of. I took it to him and he said i can fix it well it runs like a brand new car and the gas mileage went way up way up. The guy name is Gary Latin and the # is 1-509-453-2272, call him ha can fix it. Thanks Jerry

4x4moose · December 24, 2006

thanks gd, i take a look after she cools off and dries out a little. would napa have the jets i need?

4x4moose · December 24, 2006

so what dose the emulsion tubes do? i have not the slightist idea what the hell they do.

Loyale 2.7 Turbo · December 24, 2006

... I got poor gas milage too.. Because I never let the secondary close:lol: That had alot to do with my mpg.hahah

Maybe That´s the Answer... Try to Use less the Secondary...

NorthWet · December 25, 2006

so what dose the emulsion tubes do? i have not the slightist idea what the hell they do.

Emulsion tubes are "Black Magic". They are where the fuel from the main jet and the air from the air bleed mix into a fuel/air emulsion prior to being delivered to the discharge nozzle in the venturi. Minor variations in cross-section and side-hole size/shape/location make big differences in how the air and fuel are mixed. Generally, you DO NOT want to mess with emulsion tubes, as they will drive you crazy and/or poor and leave your engine running crappy at odd places in it power band.

Do as GD says and you will be far closer far faster (and far cheaper!!!) than messing around from some indeterminant set of jet values.

Frank B · December 25, 2006

thanks gd, i take a look after she cools off and dries out a little. would napa have the jets i need?

If the counter person knows how to use the catalogs, you may, MAY find them in the old carb books. If not, they may be able to look up jets for some of the cars that had the holley 5200 series carbs on them(weber clone). Do a search on here, and the web for "holley 5200" and you'll get your list.

I used to manage two NAPA stores, and I remember the old carb parts catalogs had jets in them, but It's been a few years so they may not offer them anymore.

4x4moose · December 25, 2006

i check my jets they all seem to be what gd calls for, but the primary air bleed i think is a 110 but it could be a 170, i just need to check the emulsion tubes, not sure how do to do that. im thinking that they are going to be f50 since ever thing else is stock. so were do i go from here? just change the idle mix jet to a 50? i can try to find the 60 that was in there. but i rember it ran worse with the 60 in it but, i have spent a lot more time with the card since i changed to the 80. you all have been great help so far. the only thing is that i can think of is the float drop is to low, the lower the float the more fuel and higher would be less right?

NorthWet · December 25, 2006

... the only thing is that i can think of is the float drop is to low, the lower the float the more fuel and higher would be less right?

Depends on what you mean/orientation. (Not trying to be funny. )

If you are talking about with the carb top off an inverted, then yes, the closer the float is to the carb top the richer it will run (along with other effects). Or, the higher the float/fuel level is, the richer it will run.

chef_tim · December 25, 2006

Again with the pictures:rolleyes:

And this is how I do it (I use a digital slide scale now)......

Hope this help, Tim

4x4moose · December 26, 2006

understood. i know the float is to high(with top inverted) cause its running rich, so how much should i drop it? like 2 to 5mm or so. gd, what do you have yours set at?

redscab · December 26, 2006

the float is used to work the needle valve letting fuel into the bowl from the fuel inlet. it has nothing to do with it running rich or not. it can be adjusted as Chef Tim has shown, for off roading, so that the level in the bowl is more controlled for bad angles when off-roading.

in normal operation the fuel is sucked from the bowl through the main jets by vacuum created in your intake.

the idle circuit (screw diagonal into corner of carb just above disty) control the fuel for the idle circuit. when it's turned all the way in, it closes off the fuel at idle and the car dies.

if you have it out too far you're wasting gas, and probable compensating for the running in another manner.

there are resources on the web for weber tuning. best best is to put it back to "stock" settings, and then make sure you timing and idle speed are back to stock. then try adjustments from there.

at least you are on the west coast, when your gas is a bit cleaner and probably oxygenated (sp)... When I've been in WA, I've gotten the kind of mileage you'd expect, but in the heartland of the country, you're lucky to get 21-22 max. most of the time between 15-17 realistically, because I have a heavy foot, and like to drive that way. Even a nicely tuned/running hitachi, I get 24 max.

GeneralDisorder · December 26, 2006

Fuel level in the bowl does affect the mixture. The level dictates how much fuel pressure flows through the jets. Think of it as a siphon effect. The higher the level in the bowl, the more fuel will flow when it's sucked out into the venturi. You can adjust the float for off-road, there's a seperate measurement for that, but it does not mean you won't have to change jets or air bleeds to compensate, or possibly just live with crappy mileage.

The measurements for the float can be found on the web - I can't remember where I last got them, but you hold the carb top vertical and measure it with the float dangling.

GD