A/F Ratio

Loadco · #1 (**permalink**) 07-15-2005, 07:31 AM

I'm running a tunnel wedge on a 427. I recently purchased the Innovative Motorsports LM-1 A/F ratio meter. Have spent some time getting WOT A/F ratio set. All my testing was done with the O2 sensor in the pasenger side pipe. WOT A/F on the passenger side is 13.2. I switched the sensor to the drivers side and the WOT A/F is richer at 12.1. Has anyone experienced this. I am sure I have no exhaust leaks or intake leakes that would influence the results.

blykins · #2 (**permalink**) 07-15-2005, 07:39 AM

Not too uncommon....could be just the difference in jets on that side paired up with different runners on the intake.

Loadco · #3 (**permalink**) 07-15-2005, 07:45 AM

Quote:

Originally posted by blykins

Not too uncommon....could be just the difference in jets on that side paired up with different runners on the intake.

I'm not to sure I follow you. The primary jets in both carbs are the same size (#68), the secondary jets in both carbs are also ther same size (#80) and both carbs have the same size power valve and secondary spring.

blykins · #4 (**permalink**) 07-15-2005, 08:24 AM

True, but there could be inconsistencies in the intake that would warrant a different size jet on the passenger side than on the driver's side...

I used to work at an engine lab....the engine builders there would sometimes have to jet differently from one side to the other (seemed more common on Demon carbs).

It could be a difference in shape in the intake runner....cast flaws.....could be anything.

If you don't have any gasket leaks, there's only so many explanations for why it would have different A/F ratios on each side...

Loadco · #5 (**permalink**) 07-15-2005, 08:33 AM

Now it makes sense Brent. I was considering different jet sizes from right to left but was not sure if that was a good idea as up to now I have never heard of anybody doing that.

blykins · #6 (**permalink**) 07-15-2005, 08:51 AM

Yeah, you don't hear of many people doing it, because many people don't have access to lambda sensors to check their ratios....and a lot of people don't think about checking right to left....

You might wanna look at your idle air bleeds too.

Chaplin · #7 (**permalink**) 07-15-2005, 09:39 AM

Does a tunnel wege have an open plenium or split plenium design. If it has an open plenium, different jet sizes doesn't make sense to me because all the fuel/air from jets on both sides of the car are getting mixed together below the carb and sucked into the intake runner.

Excaliber · #8 (**permalink**) 07-15-2005, 09:44 AM

Hmmmm,,,,,, Shelby came out with an offset to one side intake manifold for this very reason.

Brain fart, can't recall the name now!

blykins · #9 (**permalink**) 07-15-2005, 09:46 AM

SB Victor Jr. single plane intakes have this problem. Some cylinders will run leaner/richer than the other ones....causing hotter exhaust temperatures on different cylinders. It has to do with the casting inside and the lengths/shapes of the runners.

They make a "turtle" that goes down in the plenum to even it out.

Loadco · #10 (**permalink**) 07-15-2005, 09:47 AM

When I have some time I'm going to give it a try. I will post the results.

RICK LAKE · #11 (**permalink**) 07-18-2005, 04:41 AM

Loadco You didn't say which carb you are using or intake manifold. Any way Look at the manifold and see if it is a dual plane. If yes, the right side of the carb controls the left side cylinders. You want to go 2 sizes smaller on the MAIN jets for the rich side and 2 sizes larger for the lean side. If it is a single plane, without a divider or turtle, left is of carb goes to left side head. Go no more than 2 sizes without rechecking A/F. Try for around 12.7-12.9. Better to be rich and not hurt the motor than lean. Lean makes more power but with the gas today, I would be adding additives. These additives will affect o2 sensors to a small degree. I would use your A/F meter for checking but wouldn't leave it in the pipe for long term. Check the local speed shop for jet kits. If you have a jet drill kit you can open up them yourself. Buy 1 set for spares of the orginial size. If it is a single plane manifold you may need to have it ported to match each cylinder if you want to get crazy. FE does have a couple of hotter running cylinders than the rest. Welcome to the ERA Club. Rick Lake

Loadco · #12 (**permalink**) 07-18-2005, 03:04 PM

Well, actually I did say.. It is a Tunnel Wedge which is a single plane intake. I run a 50/50 mixture of Cam2 and gas so I'm not worried about a13.3 A/F ratio. Thanks for your reply.



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