to make Weber 48 ida more economical

Rune

Supporter
I know that people do not install Webers because they want lots of mmiles pr gallon, my Webers run very good from idle to max load, but when I drive normal on the road I feel that they use to much fuel. I have not done good measurement on this yet.
I made the third progression hole, and wonder if this can do this? the idle are 120/0.70 and main is 180 /air corr.180 venturi is 37mm. I need someone to give me a idea how to continue for a better Weber . I think they perfom very good on top rpm on dyno (347 stroker) 425 hp on 6500rpm. It is in the low area I think I need someone to point out the way .
Rune
 

Mike Pass

Supporter
Fit an air/fuel meter so you can check on the a/f ratio under all conditions as you drive as you will get a continuous readout. AEM, Holley etc make them. Easy to fit - weld an adaptor for the sensor into a collector (tilted slightly down) connect to the gauge, connect + and - to the gauge. Got mine from Ebay.
Cheers
Mike
 

Mike Pass

Supporter
They should be the same if the carbs are set the same. However if you weld an adaptor into both collectors you cab swap the sensor over and put a bung in the other one. This will confirm that both collectors are reading the same so no need for two gauges. The weld in adaptors and bungs I got from Ebay.
Cheers
Mike
 

Rune

Supporter
What is fuel comsumtion on normal driving ? The books do not tell that, but I think that you folks out there that have miles on your car, have some numbers on this.
 
RUNE

WHAT IS YOUR GOAL ??? ARE YOU TRYING TO GAIN 2 MPG ?? NUMBERS WILL BE ALL OVER THE CHART DEPENDING ON HOW YOU DRIVE, FINAL DRIVE RATIO..CUBIC INCH, CAM LOBE SEPERATION... IT IS NOT AGOOD IDEA TO RUN ANY CARB LEAN TO ACHIVE BETTER GAS MILAGE. MY CAR GOT 20 MPG ON THE HIGHWAY WITH A 4 BARREL. I AM NOW RUNNING 48IDA'S. HAVE NOT CHECKED THE MILAGE..
WEBERS CAN BE A PROBLEM IF YOU RUN THEM LEAN.. POOR IDLE...POPING.
BOTTOM LINE, IF YOU HAVE TO HAVE WEBERS, SET THEM UP SO THE RUN GOOD AND FORGET ABOUT MILAGE...REMEMBER... IT'S A RACE CAR.
I TUNED MY WEBERS UNDER THE GUIDANCE OF MY FRIEND JIM INGLESE

JUST MY 2 CENTS...
 
Basicaly, as said before, its impossible to answer your question without knowing your air fuel ratio under all conditions, 1/3 rpm range, 2/3 rpm range & 3/3 rpm range, thats idle jet, main jet and air correction jet rpm ranges.

You need to fit the lambda sensor the furthest away from the collector as you can.

And most importand, you need to synchronise the carbs before you go any further. But with multiple carbs you allways have to check on sync & set the carbs once a year, like you do on motorcycles.

I usualy start driving midrange, 2/3 rpm range and try to archive about 14:1 afr. Thats the main jet doing its thing. If it starts popping you need one step richer.

Top range, about 13 -13.5 afr, thats the air correction jet. To richen that out you need to go smaller on that jet as it controls air.

Last step is idle jet, but affects low range to, 1/3 rpm range.
If it starts popping in several cruising conditions, you need to go bigger, and the resuld might be you ending up with 12.5 -13 afr, depending on weather conditions and engine bay temperatures.

All you do is avaraging, cause if the weather changes, hot cold moisture, it all have effect in a lesser way. I usualy do carb jetting in the morning or on a about 15 degree Celsius outside temp, so whenever I drive it, its always near good.

Don't try to get fuel economics, you will only harm your engine.
 
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