Could use some coaching on a '79 CA car tuning for SMOG
05-14-17, 03:02 PM
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Could use some coaching on a '79 CA car tuning for SMOG
First time running her through SMOG, carb was touched by a shop and I had to re-do some of their work (wouldn't idle, flooding). That leads me to want to make sure I have her in good order before trying SMOG. All of her SMOG gear is intact and functioning to the best of my knowledge.
The idle is now set at 750, so I think I am OK there.
The picture shows what I think is the idle mixture control (where screw driver is touching). My questions is that the manual says screw that in until running is bad and then back off, but I've seen here that the coaching seems to be to screw it out until it runs back and then turn it back in a 1/2 turn. I know the thermal reactor needs fuel to run hot, but not sure which way to turn the idle control based on the conflicting information.
The idle is now set at 750, so I think I am OK there.
The picture shows what I think is the idle mixture control (where screw driver is touching). My questions is that the manual says screw that in until running is bad and then back off, but I've seen here that the coaching seems to be to screw it out until it runs back and then turn it back in a 1/2 turn. I know the thermal reactor needs fuel to run hot, but not sure which way to turn the idle control based on the conflicting information.
05-14-17, 03:23 PM
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ok, yes that screw is the idle mixture screw. the screw above it is the idle air screw.
i would suggest the idle air screw be left where Mazda says to put it, or leave it alone.
the idle mixture screw is pretty simple. counterclockwise turns the screw out, so it can let more fuel in, and it will be richer. turning the screw tighter, puts the screw in the passage, which will then let less fuel through, which will be leaner.
you want to turn the idle mixture screw to where the car idles the best, and then go 1/8th to 1/4 turn richer. off the top i would say to start with the idle mixture 2.5 turns out, but if the Mazda book says something different go with that.
as you say the Thermal reactor needs heat to work, and heat comes from fuel. with my SA we pretested the car, and it passed, the smog guy turned it off to setup the machine, which took about 2 minutes, and then when he ran the smog it almost failed, because it wasn't HOT.
so we want the thing richer than optimum to get the reactor working, and it also keeps the engine from misfiring. a misfire will spike the HC's, and we need to avoid that.
after the test feel free to turn the mix back to where it runs best. i actually like the reactor system, the cats need a certain mixture all the time, and the reactor doesn't, it also seems to be more durable. and third the reactor WORKS, my SA posted excellent emissions numbers
i would suggest the idle air screw be left where Mazda says to put it, or leave it alone.
the idle mixture screw is pretty simple. counterclockwise turns the screw out, so it can let more fuel in, and it will be richer. turning the screw tighter, puts the screw in the passage, which will then let less fuel through, which will be leaner.
you want to turn the idle mixture screw to where the car idles the best, and then go 1/8th to 1/4 turn richer. off the top i would say to start with the idle mixture 2.5 turns out, but if the Mazda book says something different go with that.
as you say the Thermal reactor needs heat to work, and heat comes from fuel. with my SA we pretested the car, and it passed, the smog guy turned it off to setup the machine, which took about 2 minutes, and then when he ran the smog it almost failed, because it wasn't HOT.
so we want the thing richer than optimum to get the reactor working, and it also keeps the engine from misfiring. a misfire will spike the HC's, and we need to avoid that.
after the test feel free to turn the mix back to where it runs best. i actually like the reactor system, the cats need a certain mixture all the time, and the reactor doesn't, it also seems to be more durable. and third the reactor WORKS, my SA posted excellent emissions numbers
05-14-17, 03:40 PM
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Thank you very much for the response. The idle mixture screw as been touched already so let me try the above and fingers crossed.
Thanks again, have a great rest of your weekend.
Thanks again, have a great rest of your weekend.