What is the best mixture number to set the carb mixture at idle for my stock application, after it's hooked up to a Sun test machine? So that it's not too lean and not too rich. Can't find it in my books.
Adjust for highest possible vacuum at idle; then turn each screw LEAN just a bit--enough to knock off about 1/4 inch of vacuum each. Going that little bit lean makes very little difference in idle quality, but a major difference in emissions created.
since your going to be using a sun machine for set-up, get the co to 2.00 to 3.00% make sure to watch the hc output. set the co to get the lowest hc output. dont worry to much about the a/f reading on the scope. also check your base timing as to much base timing will cause high hc output also. when the engine is running and have the four gas probe in the tail pipe, pull the pcv valve out (vacuum hose still attached to valve)and watch the co readings if the co readings go down you need to change the oil before setting up the carb. the oil is loaded with fuel and your not getting a correct reading of the amount of fuel the engine is getting.
If you are using a Sun Engine analyzer, the best approach is to set the carb for minimum HC. If the the engine is either rich or lean, the HC or hydrocarbon readings will start to rise. As you approach the best setting, the HC readings will continue to drop, until they bottom out. The actual reading will depend on the engine, however, the best setting will be the one providing the lowest HC readings. Taking the time to set it that way will provide an impressively smooth idle, with minimum emissions, and the best economy. That method has been successful for me for years. Ray
You can really fine tune the mixture adjustments on a Sun machine, but Ive found that the car doesnt always run well with the mixture set that way. I love playing with my Sun scope but Ive always had to richen the mixture afterwards to make the car run nice. It doesnt always run good real lean Just out of curiousity, what model Sun scope?? I have a Sun 500 5 gas analyser.
Hi Jason, yes you are absolutely right. Too lean will also cause a more shakin' engine at idle. I do not know yet what model Sun it will be. I am going to a person i know that works at a universal car garage/ repair shop so i have to wait what they have. I know i do not want it too lean, i will look at the engine when it idles without too much shakin'. It's funny because when i drive it for a while very easy just just floating on the road, drive back to my garage, open up the hood and the engine does almost not shake at all, i can put a euro (our dollar coin) on the side of the airfilter element and it stays there. But sometimes it just seems to shake a bit more. Thanks:TU: P.s. nice to see you work at Snap-on. My buddy and i have visit the Snap-on truck lots of times here in The Netherlands. that would be your collegue here in The Netherlands right! My buddy knows the quy very well and the tools are the best but man they are very expensive.
So, in the end, you might as well do it yourself in your driveway with a vacuum gauge. Adjust for best vacuum, (engine fully warm, curb idle, some folks prefer to do it with the auto trans in gear and the wheels blocked) then lean it out a touch. Done. You don't need an exhaust analyzer to adjust the idle mix.
A Sun machine is invaluable to diagnose engine drivability problems. Between the gas analyser and the dual pattern occiliscope, you can pretty much pinpoint emmision and ignition problems failrly quickly. it had a bunch of custom tests like cylinder balance, snap Kv test, and cylinder shorting to name a few. Its a neat tool!
yes its a great tool to have. thats why i have my own in my garage,along with my own sun distributor machine.:TU:
I have a Counselor II 'scope and and the matching exhaust gas analyzer--the gas analyzer doesn't work because I'm too cheap to install a new oxygen sensor. Yes, they're lots of fun. Yes, they're great for diagnosing problems. Yes, you get a really groovy pattern when you connect a 'scope to a car with an MSD box. No, you don't need either piece of equipment to adjust idle mix on a car that is otherwise running OK. Especially if you have to go to someone else and have them do it, and doubly so if they're going to charge you for it. The point of adjusting the idle mix is to make the engine run good at idle and off-idle, while minimizing emissions. And a vacuum gauge is all you "need" for that as long as you aren't trying to verify the thing for emissions laws. At the point where you are dealing with emissions laws and certifying the vehicle, I'll concede that the exhaust analyzer is essential.
Schurkey- The O2 cell for your analyser is $58.00. Call 1-800-FMC-TEAM (1-800-362-8326) You need extension 1757 for customer parts. Tell them you need a 7049-0004-01 oxygen sensor. Theyll mail it right out to you :TU: .
Appreciated! I have seen 'em on eBay; and the local Snap-On guy gave me contact info for a service center. I should order one before they're discontinued. Problem is, they're only good for six months and then you need a new one--and I'd probably only use the thing once or twice in six months.
yes, once you open the package you "light the fuse" so to speak. But you should get more than 6 months out if it. A year and a half is about average. Ive seen them go up to 2 years. Use only Snap On/Sun 02 cells. Ive had low voltage issues right out of the box with the off brand ones.
