Standard VICS/VTCS behaviour
 

Trying to add this to my expansion board. Everyone says that the VICS opening point is aroung 5200rpm, does that mean that the VICS solenoid is activated above 5200rpm and deactivated below that or vice-versa?

Any official docs on the VTCS? The factory manual is a little vague and my EUDM car doesn't have VTCS:

VTCS solenoid:
ECT above 60°C {140°F} while idling: B+
ECT below 60°C {140°F} and Below, engine speed at 3.500 rpm: 0-1.0V

I'm going from memory here as to the "resting" state of the shutters, which I believe are open when no vacuum is present (ie: manifold sitting on a shelf, disassembled):

The solenoid is activated (pulled to ground) below 5200 RPM in order to apply vacuum to the actuator and close the shutter. Above 5200 RPM, the solenoid is de-energized to close off the vacuum supply and allow the shutter to open.


I have neither a VTCS engine nor an '01+ service manual, however I can offer some general insight based on your description.

Like most of the other solenoids on the car, the VTCS solenoid has +12 applied to one side, and is then pulled to ground by the ECU.

Thus, a reading of B+ as observed anywhere on the B/W wire up to and including ECU pin 2N the would indicate that the valve is not energized, while a reading of 0-1v would indicate that the valve is energized. The readings may seem backwards because you're measuring voltage at the low side of a ground-switched coil.

So, if I'm properly interpreting the behavior of the VTCS shutters (closed at warm idle, open during warmup or off idle) then energizing the valve causes the shutters to open.

Joe you have it backwards... open at warm idle, closed during warmup or off idle...

the VTCS is spring loaded "open" or the condition when warm/above 3500 RPM. Ie if you disconnect the vacuum source, they remain open.

The problem is that on a boosted car, it's problematic to have the butterflies closed because it chokes the car off. I had reasonable luck setting the minimum RPM to about 1700 rpm and 60C. Once the car is warm, they remain open and it's a non issue. But when it's cold, it sucks.

Ok, that makes more sense. Vacuum is required to close them, so a low test condition when closed.

I never realized that they were closed at any off-idle condition. Kind of a dick move on Mazda's part.

Reverent are you trying to get info on VICS which is what the 99/2000 cars have or VTCS which is what the 2001+ cars have?

From all the reading I have done, they are 2 different systems, with different objectives. From what I have read, VICS is used to add a little top end power, while VTCS is used for emissions controls during idle and low rpms. Here is so more info on it.

Ok, so for the VICS, I will keep the solenoid activated to get vaccum to the actuator that holds the throttles closed until 5200rpm, and then deactivate the solenoid to open the throttles.

For the VTCS, do I do the following:

1) When the engine is not warmed up yet, and below 1700rpm, keep the throttles closed by grounding 2N
2) When the engine is not warmed up yet, and above 1700rpm, open the throttles by un-grounding 2N
3) When the engine is warmed up, keep the throttles open at all RPMs

Does that make sense?

If possible, I would recommend allowing the user access to the VICS switchpoint. While not absolutely imperative, it would give the user the ability to pick up a handful of torques in the middle as the ideal switchpoint can vary by 200-500 rpm depending on the exact setup.

I'm not sure that there is any value in operating the VTCS system. The VTCS butterflies are often removed to free up a little power.

For those running COPS and EBC (WLED, ALED and PA0 all taken up), it won't be possible until I get a new firmware out that will allow people to tweak settings through a PC, but that won't happen for at least a few monts at best. For those not running COPS and EBC, they will be forced to get the VICS controlled through my board, which will not be easy to set somehow. I do have a jumper free, but that may allow a single different switchpoint, say 5500rpm instead of 5200rpm.

Ben, you have a PM.

Dimitris

I just replied to it--looks like a good idea.

You also have PT6 and PT7 (if not running sequential fuel).

Thanks for replying on a Sunday! All of the units will be running sequential injection, so PT6 and PT7 are taken.

It's not a problem man, I tend to be on this forum daily.

I didn't realize that all of your builds are sequential. Are the external drivers built in your expansion board?

Someone asked the same question on one of the first few posts, yeah, fueling is sequential on every unit except for guitarjon's who has a 90. No, there are not on my expansion board, they are on the proto area.

closed at any off-idle condition when the car is cold. It's a cold start emissions thing. The butterflies force the airflow to a small channel on one side of the intake runners to help improve in-cylinder tumble and I guess it requires less fuel since it's mixing the charge more.

I have a theory (without confirmation but based on anecdotal descriptions from other 01-04 owners) that mazda's ECU recall was to make it as you said--closed VTCS butterflies even when the car is warm up to 3500 RPM.

My theory is based on people taking their cars in for the recall or turbocharging the later models and complaining about the weird power surge at 3500 that can't be explained... until they pull and plug the vacuum line to the VTCS.

Looks good to me. And as Ben said, it can probably be left open at all times, but that RPM is low enough that you'll still gain some benefits at cold startup without the weird power surge (except maybe on a GT2554). I recall it did make cold idle a little more stable and you dont need to richen it up quite so much.

It's impressive how much work/thought you put into these.

The 4G63 code does support sequential fuel, but it will require running 2 wires in most USDM 90-93 (sole exception being 93 equipped with CA emissions).

Thanks for the kind words Ben. A few other features that I can think of the top of my head, not mentioned so far:

1) When you start the car, if you have the A/C system engaged, the A/C will not kick in immediately, it will wait 6 seconds and then engage. On most of my maps, I have the crank-to-run delay set to 4 or 5 seconds, so 6 seconds will give the engine a bit of time to stabilize the idle before it gets hit by the A/C. If the idle dips too much for any reason, the A/C gets cut off and won't start again for another 6 seconds to avoid oscillations.
2) Same goes for the cooling fans. If you give it a warm (hot!) start and the fans need to kick in, they won't for the first 5 seconds. They also don't work unless the engine is running (at least 500rpm).