Hello everybody,

I have an 81 Corvette with a E4ME carb. I'm looking into the M/C solenoid and I see other cars used this setup for more then 1 year.
If I'm correct my ECM lets the M/C solenoid cycles 10 times in 1 second. (10 Hz)
I'm wondering if later ECM's uses more cycles in 1 second (like 20Hz or even 40Hz) ?

As I see the more cycles the better the carb will get to the "perfect" 14.7:1 A/F ratio in all conditions or am I incorrect?
Thanks,

Greetings Peter

 

it is more like a duty cycle solenoid.the percentage of on time varies depending on what fuel requirements ecm sees fit.less"on"time reps a richen command from ecmand vice versa for "off" time.

 

Yes you're right. 80% on time at 10 cycles a seconde is the same as at 60 cycles a second.

But for example with an injection engine. The injector opens ones every 2 crank rotations (and if I'm correct the old TBI systems can open 2x every crank rotation). At 3000rpm this injector will open 25 times a second, or can changes the fuel supply (richer/leaner) 25x a second.
When looking at your M/C solenoids at 10 times a second the system will not react to rpm changes and load changes as quick as the injection system. So that's why I ask if there are systems running at a higher the 10Hz cycle.

Greetings Peter

 

not that im aware of however operation of solenoid only really effects fuel supply during relatively steady state engine operation...cruise etc.initial reaction to rpm and and load changes are based purely by mechanical setep of carb.

 

Thanks, but I'm still hoping that somebody knows the answer.

Greetings Peter

 

My understanding is that for our ccc-qjets, the MC solenoid cycles 10 times a second, which is the duty cycle and stays constant. The 'ON' time is the amount of time, expressed as a percent, that the solenoid plunger is in the down position during each cycle. Hence about 80% dwell is the highest you'll read because the solenoid must come 'UP' before the end of the cycle.

The ECM constantly varies the dwell based on changing throttle and VAC sensor readings. It re-writes these blocks based on O2 readings. For near instantaneous changes in motor conditions it will command dwell based on the 'last known good' value for that TPS/VAC sensor reading. The 'initial reaction' to rpm and load changes is, by no means, purely mechanical. In fact the vacuum line to the VAC sensor is small, hard plastic tubing, purportedly to increase the efficiency of the vacuum signal to the sensor-a rubber line would flex and a line with more internal volume would delay signal delivery.

The ccc-qjet was used as late as '87 in the F-bodies and I think (?) '88 in the Montes.

 

Naf got it. 10 times per second is the cycle rate (which is fixed) and the "dwell" is what percentage of that tenth of a second the solenoid is activated for (which is variable under command of the ECM). I don't know what the limits are exactly, but there are limits. You'll never get close to zero or 100% except under certain conditions like WOT where it goes full-rich.

On/activated is down/lean at the solenoid plunger. Off is up/rich at the plunger.

 

Thanks everybody,

I got mine from: http://www.carburetor.ca/carbs/parts...bs/mcs1001.htm
It's up and running great, still some little tweaking to do but nothing big.

Greetings Peter