[Joes]

Running rich

I have a White '95 968, The car is running very rich. The whole back of the car is getting black I have to figure out what is going on. The cat after the "Y" pipe has been cut out, that is the only "mod" that I know of on the car. The O2 sensor and the temp sensor are the most obvious things to check. My real question is there is a "coding" plug by the DME which adding a 1K ohm resistor is supposed to change the map to ROW (non catalyst ) Which I did, no difference. Does this really work?

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[banditsc]

Have you tried cleaning the <acronym title='mass air flow'>MAF</acronym>?

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[flash]

what chip is in there?

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[Joes]

Stock chip. I took the <acronym title='mass air flow'>MAF</acronym> out it looks good but I'll spray it and put it back. That thing getsHOT!!. I was hoping that the resistor in the coding plug would take the O2 sensor our of the picture but I may have to go down that route.

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[Cloud9...68]

[quote name='Joes' timestamp='1377872152' post='148382']

Stock chip. I took the <acronym title='mass air flow'>MAF</acronym> out it looks good but I'll spray it and put it back. That thing getsHOT!!. I was hoping that the resistor in the coding plug would take the O2 sensor our of the picture but I may have to go down that route.

[/quote]

I have to ask - when you say the <acronym title='mass air flow'>MAF</acronym> sensor gets very hot, you didn't actually touch it, did you? Not only are they very fragile, but the oil from your skin (or grease from a glove) can significantly impact its performance and shorten its life. Hopefully the heat you felt was from some distance from the actual sensor wire...

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[flash]

use ONLY a MAF cleaner.

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[Joes]

I didn't touch the wire, the whole body of it gets hot. I have <acronym title='mass air flow'>MAF</acronym> cleaner.

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[flash]

well, with the cat removed, the O2 is going to act up. the exhaust is flowing too fast over it, and the readings will be very wrong. basically it will make the ECU think that you are under a lot more load than you actually are.



it is also likely to cause the O2 sensor to fail more quickly. not sure why you would remove the cat. it actually helps quite a bit in maintaining low and mid range torque (about 20 lb/ft). time and again we see people remove them, mistakenly thinking they will gain power, only to lose a lot more torque than they ever gained in upper end hp. ultimately they usually put them back in.





our system is very touchy about exhaust changes. there are gobs of charts out there showing the big dips from free flow systems. i discovered just how touchy when developing the supercharger. small changes in the tubing resulted in big changes in the curve. most were not good. it took quite a bit to find a setup that didn't lose power.

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[Joes]

What about changing the map to the ROW map no one has said anything about that. Does it work???? also the manual says if there is no signal from the O2 sensor it ignors it. (in other words it changes it map) Has anyone had experence with that?

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[flash]

that depends on what you mean by "work". it is not a solution to running rich. the ROW cars also run the same cat as we do. there were very few cat delete cars, and they run a different chip. they were only sold in countries that did not have unleaded fuel. the ROW maps are for minor fuel differences and such. they have slightly different timing and fuel settings. they are not for cat delete.

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[Joes]

I understand what you are saying. The manual says (electrical diagrams model 95 sheet 5 ) that if you put the 1K ohm resistor in the coding plug it will change the map to a "non cat" map. (I assume) Adding that resistor is identified as M150. If you go to sheet 14, M150 is identified as " Without catalyzer"

and on a 944 Wilks sells the resistors to change the map in the DME. Now I have done this to race cars and street cars and I could never notice a difference even on the dyno but nevertheless according to the book it is supposed to change the map. So I guess I'll just get a new O2 sensor and see what that does.

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[flash]

adding the resistor does change it to the cat delete map. however, that also causes rich running, as it put you always in open loop. it is not the fix for your problem, and a very bad idea for a street car. running it at lower rpms, as you would on the street, you will foul things out in a hurry. i wouldn't be a bit surprised if your plugs are carbon fouled too. the tops of your pistons are also likely to be coated.



likely you burned out the O2 sensor from running with no cat. like i said, the ECU gets confused because of the increased flow. so, it adds fuel. that constant rich running coats the O2 sensor and causes it to fail prematurely.



if you are going to run without a cat, you need to remap the ECU. the stock chip can't do what you need. neither can any aftermarket chip out there. you'll need to do a custom one.

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[Joes]

well that makes sense I have a O2 sensor on the way, thanks

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[flash]

yeah - it's a real bugger. i went through a few different iterations of cat-backs so as to not have things moving too fast. and i was keeping the cat. i spent about $11k on the various attempts. i wasn't the only one either. it's amazing at how touchy this car is. it looks like it's due to the cam overlap as well as the exhaust velocity. porsche did a few things to slow things down. i think they ran into this very problem. the solutions they came up with are interesting to say the least.



but, that's exactly why everybody see losses when they open up the exhaust. it goes against all the things we know and do with other cars, but it is reality. if you want to keep the bottom and mids, don't open it up at all.

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