frequency valve/lambda control conversion Euro308QV

Ok, here is one for the Brainiacs out there.

So, I have to get the 308QV Euro smoged ( every 2 years in Calif) so while I have the prototype supercharger parts sent back to 928Motorsports for finalizing (polish, powdercoat, remachine etc.) I'm going to the test only station.

When I did the California EPA conversion 2 years ago, the conv facility added a lambda control unit, frequency valve, O2 sensor, cats, and a charcoal cannister evap system. When I did the SC work I simply removed the fuses from the lambda electronics, removed the stock WUR and frequency valve system, and pulled the O2 sensor off. Everything went into protected and labeled storage for the future. The future is now.... and everthing is back on the car as it was, but it does not apparentley function. It seemed like a simple off and back on would work fine, but Nooo.

My wide band data logger tells me I am running (quite well and smooth, btw) an air fuel between 11.8 and 13.5 under normal warmed up driving/accel/cruise conditions. The idle air fuel warm is set to 14.5:1 +/-. Warm up sequence is normal with the cold start injector, warm up regulator and aux air working as designed. If I test for 12v power at the 2 feeds ( one constant, the other powered along with the fuel pump etc. cir) to the lambda box, all is well. If I disconnect the plug to the frequency valve, there is no change in performance.

Clearly, the lambda control system is not doing its job. But why. Can I check the O2 sensor, the frequency valve, the freq valve control connection for output or resistance values to confirm ? Thought I would put it out to the community of experts ( I do not include myself here) before I take it to the $$$$ smog mechanics to iron out.

(the only thing that was ever done that may have had an effect on the sytem is this. My dyno tech used a injector driver to fire the feq valve in order to determine how it was working against fuel dist control pressures. We found that the freq valve and jumper line was being used to lower WUR control pressure by bleeding off to the tank return fuel circuit).

The O2 sensor is a single wire, no heater.

Any ideas?

-Luigi

 

Light bulb !!

Of course !! I have had the fuel distributor enhanced, so it is probably running to the rich side with the stock WUR control pressure setting. I can put the adustable control pressure 086 WUR back on and set it up for an overly lean control pressure, and let the freq valve/lambda control it to stoich, no? I would first like to confirm the operation of the existing equipment though. The lambda control is not an archaic "johnson box" it is a more modern Mercedes Benz unit (I can get model#s later if need be).

Thanks for the input !!

 

Good point. I can easily tune this, no matter what, to run stoichiometric to 2800 rpm. It's just driving it to the smog station without vaporizing piston crowns or burning valves !!! I think Motob is on to the program though. I'll test the O2 sensore for 0-5v with my Fluke VOM, and check the freq valve. Then I'll lean it out with the freq disconnected, and reconnect to confirm control (or some version of those things).

Thanks for the input FBB !!

More input welcome !! Anyone ??

-Luigi

 

Duh.


(although, I never changed the control pressure on the stock WUR that was working along with the smog modifications prior to "the science project", it is back on as before, and system pressure has been dropped back to 84psi as well ??) I'll bet the 25% flow enhancment to the fuel distributor is the cause, and changing back to the adjustable 086 wur will nail it. There will be no boost enrichment, as there is no boost !! just a little vacuum/off idle control pressure change.

-Lou

 

Mine is all aftermarket conversion (graymarket Euro car). But I'll check it out for any usefull info anyway, thanks !

 

Ok. No worries, all better now.

Switched to the adjustable control pressure WUR, brought the control pressure up to almost match system pressure, adjusted the idle air fuel to a 14.7 +/- (warm) and voila !! the lambda system took control as designed.

Thanks for all your input and ideas, boys !!

Happy Thanksgiving !!