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Guest · Posted: Fri Jul 06, 2001 12:07 pm Post subject:

From: larso
Email: l_porsche@hotmail.com
Date: 06 Jul 2001
Time: 12:07:15

i don't think the CSI is the way to go, use the current set up its already got, the frequency valve.

THe OXS brain in your car takes voltage from the O2 sensor and adjusts the fuel for ya, so get a pressure sensor that reacts and puts out voltage accordingly....(i'll see where to get one)

Put it in place of the pressure sensor switch, as boost increases more fuel is added, you just gotta fine tune the switch with resistors and some treats like that to get the final voltage output to add and decrease fuel accordingly. Maybe under really high boost cut off the fuel too. WUR i don't see how u could use that unless you had voltage sent to the heating elements.

Guest · Posted: Fri Jul 06, 2001 8:01 pm Post subject:

From: Jon Furst
Email: jfurst81@hotmail.com
Date: 06 Jul 2001
Time: 20:01:54

<THe OXS brain in your car takes voltage from the O2 sensor and adjusts the fuel for ya, so get a pressure sensor that reacts and puts out voltage accordingly....(i'll see where to get one) >

The OXS system adjusts the fuel inlet pressure to control the amount of fuel that gets to the injectors. This regulates, to a relatively small degree, the amount of fuel that enters the engine. This isn't a good way to regulate fuel flow in a high boost situation.

On the 931, the control pressure is lowered by the WUR under boost to allow more fuel to flow to the injectors. The lowest that the control pressure can get is reached at 0.8 bar boost. Boost levels above this are not accompanied by additional control pressure lowering.

The Andial box lowers the control pressure by use of a frequency valve attached to the WUR fuel line. This is the only way to add significantly more fuel to the engine while maintaining part throttle and idle mixtures.

Jon Furst
'81 931

Guest · Posted: Fri Jul 06, 2001 10:36 pm Post subject:

From: larso
Email: l_porsche@hotmail.com
Date: 06 Jul 2001
Time: 22:36:09

those stupid germans put throttle switches on the car, one for idle works, but the one for the full throttle won't work then? whats the poitn of having teh fuel enrichemtn at WOT, other than that tiny bit of time you don't have full boost at WOT it looks pointless....

Guest · Posted: Fri Jul 06, 2001 10:54 pm Post subject:

From: larso
Email: l_porsche@hotmail.com
Date: 06 Jul 2001
Time: 22:54:33

>>On the 931, the control pressure is lowered by the WUR under boost to allow more fuel to flow to the injectors. The lowest that the control pressure can get is reached at 0.8 bar boost. Boost levels above this are not accompanied by additional control pressure lowering<<

WHere is the sesor for boost on the 931? is this only on the later 931s?

Guest · Posted: Sat Jul 07, 2001 4:03 am Post subject:

From: Jon Furst
Email: jfurst81@hotmail.com
Date: 07 Jul 2001
Time: 04:03:19

<those stupid germans put throttle switches on the car, one for idle works, but the one for the full throttle won't work then? whats the poitn of having teh fuel enrichemtn at WOT, other than that tiny bit of time you don't have full boost at WOT it looks pointless....>

I think the full throttle switch just turns off the OXS system to prevent the mixture from being leaned under full throttle.

Jon Furst
'81 931

Guest · Posted: Sat Jul 07, 2001 4:05 am Post subject:

From: Jon Furst
Email: jfurst81@hotmail.com
Date: 07 Jul 2001
Time: 04:05:13

<WHere is the sesor for boost on the 931? is this only on the later 931s?>

All 931's have a vacuum/boost line that attaches to the WUR. That's where it gets the boost signal from.

Jon Furst
'81 931

Guest · Posted: Sat Jul 07, 2001 11:10 am Post subject:

From: larso
Email: l_porsche@hotmail.com
Date: 07 Jul 2001
Time: 11:10:02

Ok so does this mean the 931 WUR is different than the NA one in that there is a vacuum hose nipple or does the NA also have it fro some other thing?
Like when replacing the WUR (since they always go bad on these cars) is there a different one for the 931?

Guest · Posted: Sat Jul 07, 2001 11:17 am Post subject:

From: larso
Email: l_porsche@hotmail.com
Date: 07 Jul 2001
Time: 11:17:42

i had thought it actually richened it a little....rather than keeping it neutral i don't have my haynes to look but i had thought it actually turned it off yes, but ALSO richened it by increasing duty cycle of frequency valve more than just unplugging the freq valve....because when you turn the frequency valve off, it sets itself in the middle 50 percetn duty. im just wondering if it really does ANYTHING by richening this part of the system...
Like if it didn't do anything then this car would have real troubles with emmisions no? Because when your driving on the road usually you have lots of boost, so the OXS system is doing shit as your driving, but in reality it won't do anything because you have boost holding it up right! I mean most of the time your boost gauge is up there enough under normal driving that the OXS wont't work for emmisions at all right?

Guest · Posted: Sat Jul 07, 2001 8:01 pm Post subject:

From: Jon Furst
Email: jfurst81@hotmail.com
Date: 07 Jul 2001
Time: 20:01:08

Yes, the 931 WUR is different than the N/A one. The n/a WUR doesn't have the nipple on it. The '80 turbo has it's own WUR, and the '81 and '82 share one.

Jon Furst
'81 931

Guest · Posted: Sat Jul 07, 2001 8:19 pm Post subject:

From: Jon Furst
Email: jfurst81@hotmail.com
Date: 07 Jul 2001
Time: 20:19:01

<i had thought it actually richened it a little....rather than keeping it neutral i don't have my haynes to look but i had thought it actually turned it off yes, but ALSO richened it by increasing duty cycle of frequency valve more than just unplugging the freq valve....because when you turn the frequency valve off, it sets itself in the middle 50 percetn duty.>

Hmm. I thought that the frequency valve was an on-off thing, and unplugging it would be the same as leaving it open. I believe the duty cycle for the frequency valve refers to it's closed-open ratio. Maybe someone who knows can chime in here

<Because when your driving on the road usually you have lots of boost, so the OXS system is doing shit as your driving, but in reality it won't do anything because you have boost holding it up right! I mean most of the time your boost gauge is up there enough under normal driving that the OXS wont't work for emmisions at all right?>

Well, the full load enrichment mode only happens at full throttle and/or over 3500 rpm. So if you're cruising at 3000 rpm at part throttle, you'll still be using the OXS system. I don't believe that boost level is a factor. The higher boost just adds more fuel, but it is still monitored by the OXS system.

Any CIS experts, please correct us! :)

Jon Furst
'81 931