adam

Anyone know what correct dwell values should be during driving?
I'm trying to tune my carb (81 electronic) and the Dwell is high (50's)
during idle. But during cruise, say 40 mph, it's in the 35 range.

Anyone know? Ken73 - any of your ECM work applicable here?


:confused:

Gordonm

A dwell meter is used for points. In electronic ignitions the dwell is set and cannot be changed. On points you either open them up for increased dwell or close them for less dwell

UKPaul

Adam,
Set the meter on 6cyl dwell & aim for between 25 & 35 at idle. If it is stuck on 10 degrees or 50 degrees then you have a max lean or rich condition. The idle adjustment screws are normally set 2-4 turns out and then the IAB adjusted to bring the dwell into spec.
These figures are from memory (ie don't rely on them), I'll need to check my manual, but I don't recall seeing the dwell values for anything other then idle. I'll check over the weekend, but I,m sure that around 50 at idle is wrong.
:cheers:

Dalannex

25-35 is correct at idle. With a dwell meter hooked onto the mixture control test lead you are testing the mixture control "on time" or time that the selenoid has power, and is pulling the primaries down. Therefore, if you are getting 50 at idle you have a lean condition. At 25-35 degrees of dwell the mixture control selenoid is on, or pulling the primaries down about 50% of the time. At 50 degrees of dwell the primaries are down about 80% of the time. You can figure this because the max dwell reading is 60 degrees, which is closed all the way on the primaries, and 54 degree dwell reading, for example, would be 90% of 60 degrees. So, the lower dwell reading at cruise would mean less on time of the mixture control selenoid, and a richer condition, which should be right. Your idle reading sounds lean though.

Justin

BTW, UKPaul, did you get my email? My internet crashed just as I sent it, so I dont' know if it went.

adam

Dalannex;

Thanks for the good info on the dwell scale...

I know I have a rich condition because:
a. My tail pipes (actually entire exhaust sytem) has black soot in it, at edges.
b. My O2 sensor reads about 0.62 volts (where I'm told 0.47 volts is desired.)

I've already adjusted the power piston to be at the proper height (given the
carb adjusting tools for an electronic carb.)

What I'll try is to screw in the idle jets and see what that does to the measurements.
Until now, I didn't know which has the greater effect, the power piston setting or
the idle jet settings. From the discussion of the dwell scale, it now seems that even
with the power piston mostly closed, the idle screws are making a rich condition.

Thanks.

UKPaul

Hi Justin,
No, didn't get the email, but no matter. Hadn't seen you around for a while & thought you might have gone OTT at a Xmas :party: :D
:cheers:

Dalannex

The mixture control selenoid pulls the primary metering jets down into their seats, which has a greater effect on rich or lean conditions than the mixture screws that are located at the bottom of the carb. I would screw the mixture screws in all the way, then back them out 3 1/2 turns and leave them. I would then take the top off and set the lean stop with a lean stop gauging tool, then put the top back on and set the rich stop and the initial adjustment of the idle air bleed valve with the gauging tools. Then go with your idle adjustment using your dwell meter, adjusting only the idle air bleed valve to see what your dwell reading does then. You should be able to get it to 30 degrees. If you still are getting a rich or lean condition at idle you will have to adjust the mixture control selenoid lean stop to compensate for it. If you are running 50 degrees of dwell at idle and are running rich your mixture control selenoid lean stop is set too high, because the dwell reading tells us that it's pulling the primaries down to try to lean it out, but it's not leaning out, that being the rich condition. Do you have a set of gauging tools for the E4ME? And are you familiar with the procedure for checking the variable voltage and resistance of the TPS? I think the gauging tools are the big ones right now.

Justin

adam

>I would screw the mixture screws in all the way, then back them out 3 1/2 turns and leave them.

Haven't played with these...

>I would then take the top off and set the lean stop with a lean stop gauging tool, then put the top back on and set the rich stop and the initial adjustment of the idle air bleed valve with the gauging tools.

Already did this...

>Then go with your idle adjustment using your dwell meter, adjusting only the idle air bleed valve to see what your dwell reading does then. You should be able to get it to 30 degrees. If
>you still are getting a rich or lean condition at idle you will have to adjust the mixture control selenoid lean stop to compensate for it.

Tried this, but no change with idle air bleed changes - that's why I'm thinking it's the idle
screws that are not correct. I will change those and check again.

>Do you have a set of gauging tools for the E4ME?
Yes, but no adjusting tool for the lean stop - seems silly that you get the gauging tools
for $11, but the adjustment tool is $13...

>And are you familiar with the procedure for checking the variable voltage and resistance of the TPS?

I read about that, but haven't checked that yet.

THanks.