Detailed explanation of Purge Control Solenoid operation?

s300 and SManager software questions & answers
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Hawkeye24
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Detailed explanation of Purge Control Solenoid operation?

Post by Hawkeye24 » Fri Jul 26, 2019 1:23 pm

I've got my s300 running my 2000 SiR with the stock OBD2 B16A2 and have been trying to understand better about the Purge Control solenoid operation and when it should be open with my car. There is only a brief description, even from Honda's technician service manual when I've looked into it at work.

Does anyone have a more detailed description in terms of map sensor values, speeds, etc it should be operating at? Usually our service manuals will have an advanced diagnostic page that better describes the operation but those are mostly for newer models.
I know there is an option to invert the purge for obd2 cars with the s300 but it seems that when I've inverted the purge, it doesn't run as well as when not selected.

I've also experienced a longer crank right after fueling when the inverted selection was used on the calibration. I've swapped a known good purge solenoid just to see if that would change things but no difference. I'm just trying to eliminate some variables. Running it with the normal selection doesn't present any issues but I'm just wondering if the purge is open when it shouldn't it would affect my AFRs for sure.

Any insight would be appreciated.

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Spunkster
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Re: Detailed explanation of Purge Control Solenoid operation?

Post by Spunkster » Fri Jul 26, 2019 3:10 pm

I do not have any more specifics on how it operates, but if you find it works ok with it not inverted then just leave it that way.

Hawkeye24
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Re: Detailed explanation of Purge Control Solenoid operation?

Post by Hawkeye24 » Fri Jul 26, 2019 4:06 pm

Got it. Would just be better to know if the purge is still operating when it shouldn't as this would affect AFR readings.

Is there a list to reference on specific models other than "some OBD2 (mostly 1998 and onwards)" that the inverted selection is required?

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Spunkster
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Re: Detailed explanation of Purge Control Solenoid operation?

Post by Spunkster » Fri Jul 26, 2019 4:17 pm

There is nothing specific as only some cars exhibit the poor running and starting conditions that require it to be inverted.

MotorMo
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Re: Detailed explanation of Purge Control Solenoid operation?

Post by MotorMo » Tue Jul 30, 2019 10:15 am

An interesting side note on the purge valve - the obd2 Honda ecu’s use a ‘pulse width modulated’ control on the purge valve- aka duty cycles. Verses the obd1 ecu’s that use an on and off valve that is then modulated by ‘ported’ vacuum on the back side of the throttle body. I have found the best approach is to retrofit the obd2 engine to obd1 throttle body l, purge valve, etc. otherwise when at part throttle the obd1 ecu will command the purge valve on, but there will be no way the amount of fuel sucked off th canister since its a direct hose from the purge to manifold vacuum, not the ported vacuum that it was designed to be used with. Rich surges and failing purge valves (from being stuck wide open for extended periods of time) may otherwise occur.
Something i have always wondered is how important (if at all) is that system to reliability and longevity of things if the canister gets fuel soaked and cant expel?? It can be a pain in the ass to swap back and forth from obd1 and obd2.....

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Spunkster
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Re: Detailed explanation of Purge Control Solenoid operation?

Post by Spunkster » Tue Jul 30, 2019 10:18 am

We have not seen any issues arising from using the OBD1 ECU on OBD2 components.

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