New guy carb question- how to select the right jets? Options

[Chily89]

I'm helping my friend get his car working correctly. We are having some carb issues. What is the process for getting the correct idle jets? I have read instructions on the redline website but I'm still having issues. The 914 is a 4cyl 2270 with dual weber 44 Idf's.

I read something about removing the main stacks then driving around. Can somebody please explain this method further.

[ThePaintedMan]

Yes. Which is why I suggested to start there first. It may not solve it, but you need to eliminate unknowns before you can tune it correctly.

Try that and see if it makes a difference on your readings. If it's a quality wideband, what you should see should be accurate.

Stu - think of it this way, widebands operate using the same Bosch-design O2 sensors that all modern EFI systems use to dynamically adjust mixture (of course there are other upstream sensors and calculations going on too). Yes, they are most accurate at temps above 1000 degrees, I think, but that shouldn't matter after a few minutes of running as the heater circuit for the sensor itself should be maintaining that. The old narrowband gauges were only accurate at a constant load, like WOT.

[stugray]

Stu - think of it this way, widebands operate using the same Bosch-design O2 sensors that all modern EFI systems use to dynamically adjust mixture (of course there are other upstream sensors and calculations going on too). Yes, they are most accurate at temps above 1000 degrees, I think, but that shouldn't matter after a few minutes of running as the heater circuit for the sensor itself should be maintaining that. The old narrowband gauges were only accurate at a constant load, like WOT.

Thanks. I understand all of that.

I will try to post a log, but what I observe is that just looking at a meter that is bouncing around from 11.0 to 18.0 at idle tells you nothing.

The data logs show that the meter varys wildly at low RPM and no load, so much so that you cannot even tell what the average value is unless you are looking at a log or a graph.

The only time that I can get an instantaneous meter reading that is even close to what the log says is under a steady load.

Maybe it is the sensitivity of where in the exhaust the sensor is located.
Mine is right after the 4-1 collector.
Also exhaust leaks can screw up the measurements,and can make it vary with flow.

I know that if the probe is mounted too close to the exhaust exit, you will get atmosphere sucked back into the exhaust and skew the readings. This effect is amplified at low RPM.