Purge valve control

[F6R]

Anyone have some suggested settings for controlling a charcoal canister purge valve?

[IJ.]

Engine Temp based 0>59c = 0 60>130c = 100%

[Scott@FP]

I'd add TPS to that as well, you don't need to purge constantly at 100%, just occasionally, and at idle it can screw up La if its going in an out of purge.

[IJ.]

I'd add TPS to that as well, you don't need to purge constantly at 100%, just occasionally, and at idle it can screw up La if its going in an out of purge.

Interesting Scott, got some suggestions for the TPS range?

I only did the simple on/off so it replicates the Mechanical purge my car came with.

[Scott@FP]

Duplicating the factory ECU logic is always the best starting point if you can get the info.

With TPS you can make sure its shut off at or near WOT (turbo car), and feather it down at low load/idle so its not interfering with wide swings in La when lots of vapors are present. Many factory ECU's will have separate load/trim cells for when the purge is active because it can change La quite a bit.

Fuel temp and TPS works good as well.

The object for aftermarket ECU not 100% emissions compliant is to keep the canister from pooling liquid and keep the fuel tank from pressurizing so purge strategy isn't super critical and tied into other things like leak detection etc.

TPS 6% = DC 5%
TPS 25% = DC 10%
TPS 50% = DC 5%
TPS 60% DC 0%

then slope for temp (fuel or coolant), RPM or ?
Keeps my tank non-pressurized and canister happy, no stinky vapors overflowing etc.

I suppose you could achieve the same thing with a check valve and a very small fixed orifice on the ported vacuum port of the throttle body if you need the output back for other functions.

I'm sure the Motec guys are wondering why we bother to put these kinds of ECU's in street cars and actually use EGR, purge etc. You can pick up a pretty good increase in fuel mileage with a functional EGR w/o hurting WOT power, so why not?

[IJ.]

Thanks Scott I'll give that a try!

I'm using a GM Purge valve on the L98 Chev any ideas on pwm settings?
(just running it switched at the moment)

I'm pretty sure the MoTeC Boys wonder WTF I'm doing with 99% of the things I do

[Scott@FP]

Might be able to get solenoid freq info from a factory service manual, if not try using actuate outputs, start with a freq of say 16Hz, then actuate from 1% to 90% see if you get smooth operation, adj freq if its not operating properly. maybe feed the valve with some low pressure (>1 PSI) air from a regulator to check valve operation. If it never operates smoothly its probably not a PWM compatible solenoid but an on/off solenoid.

[IJ.]

Thanks again I'll try it this morning when I head out to the shed!

[stevesingo]

I have an E30 M3 that I want to keep stock looking (kind of). I was under the impression that the valve was simple open/close affair. Any one know any different?

If that is the case, I was thinking of open >10% TPS <60%TPS. Any issues with this?

Steve

[IJ.]

PWMing the valve turned a little ugly/noisy once the engine was running and pulling a vacuum, ended up just including a TPS Y axis and setting it to switched and I'll see how it all behaves thanks for the help Scott!