coldfire

iTrader: (1)

Can someone explain exactly the purpose of having the Accelerated Warmup System solenoid? I understand Mazda's original purpose for having the car rev to 3k+ on startup, but for some reason the AWS solenoid isn't the sole device that causes the car to rev to 3K+. the Bypass Air Control Valve has something to do with it. i just did a series of test with these results:

AWS plugged, BACV plugged = 3k cold start
AWS unplugged, BACV plugged = 3k cold start
AWS plugged, BACV unplugged = 3k cold start
AWS unplugged, BACV unplugged = 1.8k cold start

so actually the car only needs either the AWS or BACV and it will rev to 3k+. but why? if the BACV can do it by itself why bother putting the AWS solenoid in there.

oh well, i have been annoyingly having the start the car in-gear to avoid the annoying startup. This is one more reason a Megasquirt will be going in soon enough...

HAILERS

It's a combination of the AWS solenoid and BAC working together. Remove the plug from the AWS and the rpm should have dropped down to the 2300 rpm range. It does on my cars.

But this only happens for seventeen seconds and can be overcome by putting the shift lever in any gear and should only be happening when the water temp is b/t, if I remember right, 55 degrees F and 95 degrees F. Any Water temp above that and it should not happen.

I was just guessing at the water temps above. The correct figures are in the FSM.

My5ABaby

iTrader: (7)

Wasn't this always mostly people trying to get help on their cars?

scrip7

iTrader: (6)

Also, if you still have the thermowax unit on the throttle body, there are 2 adjustment screws. One is for fast idle cam position and the other is for fast idle speed. The thermowax should be fully released when the engine reaches normal operating temp. The FSM describes the screw locations and adjustment method.

stevej88na

Check the first graph out:
http://howto.globalvicinity.com/gv_w...i=60&co=1&vi=1

That was an attempt at understanding and graphically portraying what various idle speeds might mean. Are you sure some of those 3k idles aren't 2.8k? Your findings might be of interest since I wasn't sure how much the AWS contributes.

coldfire

iTrader: (1)

thanks for the replies guys.

HAILERS, you are describing the operation correctly. however on my car i didn't seem to notice any difference no matter what combination of BACV/AWS. based off the stock tach, i got about 3k every time.
and yes, this is only for 17 seconds, after which it drops to around 2k or less (again i haven't recorded the exact reading), and then eventually idle, ~800.

but this is an error on my part only checking the stock tach, because i have both an SAFC and a wideband that datalogs so i can get an exact RPM. i will try to get this sometime soon. hopefully there's no harm in multiple starting/stopping the engine when it's cold.

Steve that's a good section on your site. quite informative. i will try to get you some exact RPM readings if i get the chance.

coldfire

iTrader: (1)

so i've been monitoring the SAFC reading on cold starts lately.
as far as i can tell, with the AWS solenoid unplugged the lowest RPM i see is 2800. it's usually 3000 but it is not always the same.
it can be as high as 3200 RPM though. this is just with the BACV plugged in.

with both the AWS and BACV plugged in, cold start is at least 3000 RPM, sometimes as high as 3400 RPM.
this is of course for just 17 seconds or so, then it drops down below 2000.

stevej88na

Interesting, so the AWS might account for roughly 200rpm, assuming the BACV is open-loop during those 17 seconds. Thanks for the info!

coldfire

iTrader: (1)

well i'm not saying that's how they are all supposed to work. mine might just be weird

also you have take into account temperature, which might affect the RPM on startup also. that could cause the variations.

it'd be good if someone else could test this out to confirm...

scrip7

iTrader: (6)

Also, if you still have your thermowax, that is the basis for your fast idle. It holds the throttle open a certain amount, based on it's adjustment screw settings. Any additional rpm comes from the AWS, air solenoid (for 17 seconds) and perhaps to a certain extent the BAC. The AWS is just an open or closed air valve, so whatever the initial throttle position is via the t-wax will be added to by the AWS. You could have a 4000 rpm idle if you wanted it, depending on your t-wax adjustments, though not at all desired. If the overall idle is too high, the first adjustment to consider is the t-wax.

The whole idea behind having such a fast idle when cold is to get the catalytic converters to "light off" as quickly as possible, to start cleaning up emissions levels at the tailpipe. We don't have emissions testing where I live, so I have no cats. I prefer a cold fast idle at around 1800-2000 rpm max, quite enough to give a stable cold idle.

sniperstevedave

Another purpose is to heat up the O2 sensor quickly. The the doped cubic zirconia that makes up the sensor will only conduct ions (and thus a charge) when it is at a sufficiently high temperature. Some cars have a type of O2 sensor that has a heating element built in.

scrip7

iTrader: (6)

Exactly right. The temperature that most o2 sensors of the zirconia type start producing a working voltage is 600 degrees. Not only do most current vehicle's o2 sensors have heater elements, but some Chrysler vehicles turn on the heaters as soon as the driver's door handle is lifted, all in the name of tighter emissions control to satisfy tree-huggers and EPA.