Tim240z Posted November 2, 2002 Share Posted November 2, 2002 Well in the neverending endevour to get my twin Weber setup for better driveability I was able to borrow a AFR recorder from the lab at work. It's a very high Dollar industrial unit and is VERY accurate. It can display Air/Fuel ratio, %O2, Lamda and equivalence ratio. Question: What are the best setting for performance/driveability. Should I use AFR display and set up for Stoich. at idle and underload. The unit can datalog, so I can drive and get high rpm/high load #s Thanks, Tim BTW, I have already welded in the O2 sensor bung and have readings at idle of 14.56 (AFR). Quote Link to comment Share on other sites More sharing options...
Guest Rick Johnson Posted March 12, 2003 Share Posted March 12, 2003 Max power is about 13.1 to 1. Most people are afraid that this is too lean and will run hot. I suppose the fear of running an overall air fuel of 13.1 to 1 is that some cylinders will be richer and some will be leaner. I guess if you stick to an overall of 12.7 to 1 like most people suggest, your leanest cylinder will probably not be lean enough to cause problems. When I used a wide band sensor to set up my car, the G-Tek agreed that about 13 to 1 was the best power. If you are real clever you will disable the rear barrels and check the air fuel at about 3000 RPM on the front barrels (this should be about the same velocity as 4 barrels at 6000RPM). After setting the front jets to 13 to 1, connect the rear barrels and run it up to 6000 RPM and adjust the rear jets to match the front barrels. (You should pull out the secondary diaphragm spring and confirm with G-Tek that the horsepower does not change - My Avenger will only open fully with no spring at all in the diaphragm) If the cruise mixture is lean, you will have to richen the jets and build in a power valve restictor to lean out WOT - I spent weeks optimizing my setup. I ended with a 14 to 1 cruise with a 13 to 1 power mixture. Quote Link to comment Share on other sites More sharing options...
Guest Rick Johnson Posted March 12, 2003 Share Posted March 12, 2003 Max power is about 13.1 to 1. Most people are afraid that this is too lean and will run hot. I suppose the fear of running an overall air fuel of 13.1 to 1 is that some cylinders will be richer and some will be leaner. I guess if you stick to an overall of 12.7 to 1 like most people suggest, your leanest cylinder will probably not be lean enough to cause problems. When I used a wide band sensor to set up my car, the G-Tek agreed that about 13 to 1 was the best power. If you are real clever you will disable the rear barrels and check the air fuel at about 3000 RPM on the front barrels (this should be about the same velocity as 4 barrels at 6000RPM). After setting the front jets to 13 to 1, connect the rear barrels and run it up to 6000 RPM and adjust the rear jets to match the front barrels. (You should pull out the secondary diaphragm spring and confirm with G-Tek that the horsepower does not change - My Avenger will only open fully with no spring at all in the diaphragm) If the cruise mixture is lean, you will have to richen the jets and build in a power valve restictor to lean out WOT - I spent weeks optimizing my setup. I ended with a 14 to 1 cruise with a 13 to 1 power mixture. Quote Link to comment Share on other sites More sharing options...
Mudge Posted March 12, 2003 Share Posted March 12, 2003 I went for 13.0:1 WOT AFR on my Fbod, shoot for 12.5:1 - 13.0:1, make sure your doing your WOT testing in 4th gear or maybe 3rd is pretty close For your idle stuff, if you can get around 15.0:1 that would be nice (or 14.7:1 if you want stoich, but thats mainly for O2 sensors). If you go too lean with idle your off idle response will suck, and you could ping, so dont worry about starving it too much. Look for around those AFRs though for cruising. What Webers are these? Scribble down your jets and such too Quote Link to comment Share on other sites More sharing options...
Tim240z Posted March 12, 2003 Author Share Posted March 12, 2003 Mudge, These are the same as yours (twin downdraft 32/36). I posted my jet sizes in one of your posts on the same subject. Did you ever get your jetting correct? Tim Quote Link to comment Share on other sites More sharing options...
Mudge Posted March 12, 2003 Share Posted March 12, 2003 I got up to about 22 MPG, my cruising on the freeway is 3400-3800 RPM, I'm very convinced that I have a 3.90 in the car, but I wont find out till I do the R200 swap. I'm actually wondering now if the rear IS an R200, I will get a better look tomorow when I do the brakes. Looking at it last night it looks big, so I need to ID it better. Every speed trap I've been through agrees very accurately with my speedo. Even with my jettings, the car feels week in certain spots (2k-3k about), sometimes the go-pedal needs a little more motivation to get out of this wierd hesitation, so maybe the float settings are incorrect or maybe they need rebuilding, I dunno. Oddly I have 1 plastic float and 1 brass (or copper?) Quote Link to comment Share on other sites More sharing options...
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