Better mixture without 02 connected
 

Woluld a Motronic 3.2 have a stronger part throttle map (torque wise) if it were programed to run ( ignoring the 02 sensor) with a specific value, say 13.2-13.6, vs using the 02 sensor and have to oscillate up and down to maintain
Stoich (14.7)? I realize gas mileage and emissions would not be optimal, but if torque and horsepower were, would this be the way to go?
So in short I'm asking would it be better to have both part throttle and WOT maps programmed for optimum torque and horsepower?
TIA,
J.P.

The O2 sensor is the part of the system that really fine tunes what the mixture is. How could removing it give you better mixture control?

If you want it to run with a specific map of 13.2-13.6 call Steve Wong and have him make you a chip that runs there. It won't run better then having it run where he sets them normally and it would consume more gas. Oh, and it would idle rougher.


Wayne

I have a Steve Wong Chip programmed to ingore 02 sensor inputs. The car actually seems idle better than with the old chip and the 02 sensor connected. Prior to fitting this chip, I replaced the original sensor with a new one and didn't notice any improvement. There does seem to be a bit better midrange performance too. Didn't notice any gas mileage drop either.

Jpahemi,

Without the O2 info your control pressure would be almost the same regardless of engine/air temps, so your cold starts and warmups might be bad. I essentially have this kind of setup in my car as I have no DME or cat, and I could set up the car to either start very well or run very well but not both. Since where I live, cold starting can be an issue, I am running an older, vacuum controlled WUR instead of the previously DME controlled one. I don't know where you are, but perhaps cold starts are not a concern. You also would not have an enrichment for altitude changes or WOT, or you would ALWAYS have it, which may not be good for around town economy, or give you part throttle bucking or idle hunting.

Genrtlemen, thanks for your replies. I'm a little confused (what else is new). When the throttle switch for WOT is activated, the O2 sensor input is ignored and the chip runs the corresponding map value set by the program, in this case 13.2-13.6 (SW chip). During the part throttle position, the O2 loop is activated to achieve Stoich (14.7), that part I get. Now, as in the Euro cars, can't the part throttle map be programmed to run the same 13.2-13.6 ratio? Wouldn't this give optimum performance for that map? I'm not certain how the chip knows it's giving 13.2 in the WOT map if the O2 is inactive. Is this a preset value that the programmer knows based on experience with enigine design and various other data?
TIA,
J.P.

"So in short I'm asking would it be better to have both part throttle and WOT maps programmed for optimum torque and horsepower?"

What do you think Porsche/Bosch did? Do you assume that they didn't
understand engine thermodynamics and FAILED to optimize the 3.2 DME?

"Now, as in the Euro cars, can't the part throttle map be programmed to run the same 13.2-13.6 ratio? Wouldn't this give optimum performance for that map? I'm not certain how the chip knows it's giving 13.2 in the WOT map if the O2 is inactive. Is this a preset value that the programmer knows based on experience with enigine design and various other data?"

All B.S. & hyperbole! You've been listening to the performance chip marketing hype.

1. To precisely control the A/R ratio, a feedback element is required, i.e. O2 sensor,
either a narrow band (older cars) or a wideband (newer cars). Without an O2 sensor,
the DME CAN'T control the A/F to a desired/critical value!
2. The max. torque occurs at an A/R of 12.6 (see the data at www.systemsc.com
on the Graphs page and read the info on the Technical page).
A value of 14.7 insignificantly effects the max torque as seen on the graphs.
3. At WOT the DME ignores the O2 sensor and as such can only achieve a TARGET
A/R which probably is not the optimum one for max torque.
4. Most/All aftermarket fuel injection systems, e.g. Motec, use a feedback element
to optimize the A/R ratio over the complete torque curve.

Bottomline: The 3.2 DME works great for what it was designed for as programmed
by Porsche/Bosch. Based on the overall system design, there's little to be gained
by performance chip mods. GET REAL, when it comes to believing the HYPE about
them and the resulting DME performance effects.

Buy a few Bosch fuel injection books & READ, and ignore the B.S. presented
by many!

Don't the aftermarket chips already reprogram full throttle and part throttle maps? I chiped my VW Jetta and the biggest seats of the pants feeling came from part throttle response.

I think you are confusing Motronic with CIS (there is no control pressure with Motronic).
-Chris

Yes Loren, Bosch failed. They produced a program that yields good gas mileage, emissions and tolerance to poor fuel quality. I tend to believe if power was paramount in developing the program for the 3.2 , a different chip program would have evolved. They let me down!!!
Do you think the thousands of $'s I spent was wasted?? I've been had. Why me??? :~(
J.P.

Before you listen to Loren (who is incredibly knowledgable in many areas) tell you what he thinks about other people's aftermarket chips, we need to know if he is prejudiced by his business dealings:
http://forums.pelicanparts.com/uploa...1094494402.gif
Now, as far as the O2 is concerned, disconnecting it sends an open loop signal to the DME. I have smoother idle (cold or warm) with mine disconnected (prolly needs replacing anyway).

I'm not trying to be argumentative as I've promised to "only use my powers for good" :D but please Loren, don't cut my sentences in half to make your case (like you did the last time).

The narrow band O2 sensors used in the Motronic cars in question ('84-89 911s) does an OK job of tuning the mixture for emmissions but it is far too slow to be truly precise enough for closed loop A/F control AFIK. It's only good for keeping the ratio at 14.7:1 which is fine in non-demanding conditions. In other words the DME can't "control the A/F to a desired/critical value" other than 14.7:1.

The 12.6 number is a textbook number I assume. Every motor is different. I was talking with Steve Weiner a couple of years ago and he told me that 12.5-13.5:1 is too rich for a (3.2?) 911 motor. Something about the 911 having a "lazy" combustion chamber. This would make "max torque" and "best emmisions" (14.7:1) mixtures even closer to each other than if you use the 12.6 figure.

True.

While this may be true I see little relevance to the 20 year old Motronic systems we are working with that only support narrow band. As far as I know the narrow band O2 sensor is used in conjunction with a cat converter. Did Porsche ever use narrow band O2 sensing without a cat? Wouldn't they have done so if it was actually of some benefit?

-Chris

"Yes Loren, Bosch failed. They produced a program that yields good gas mileage, emissions and tolerance to poor fuel quality. I tend to believe if power was paramount in developing the program for the 3.2 , a different chip program would have evolved. They let me down!!!" - Naivete -

A chip marketing program's best accomplishment - Reaches one who totally "sucks
up the all hypepole".

http://forums.pelicanparts.com/uploa...1094516658.gif
Funny thing, we can't seem to get a straight answer out of the man.

Chrisbennet,

Thanks for clarifying.

"Chrisbennet,

Thanks for clarifying."

Clarifying what????????

"The 12.6 number is a textbook number I assume. Every motor is different." - Chris Bennett -

The 12.6 is a theoretical value which varies little between ALL engines!
DO SOME READING AND DON'T ALWAYS BELIEVE THE "HEAR-SAY".
Bottomline:
As I said, to control the A/F ratio, requires a feedback element, e.g. an O2 sensor
which is what basically was initially asked. It's B.S. to assume that basic fuel
maps can control the A/F ratios without an O2 sensor over all loads and driving
conditions. THAT'S WHY AN O2 SENSOR IS USED TODAY ON ALL CARS!

So in order to have optimal AFR, regardless of fuel managemnet type, you need the O2 sensor as intergral part of the system. Systems like Motec allow the user to optimize for power vs. the stock DME sytem used in the 3.2 which was designed with different parameters. Ok, I understand.
Essentially, the Euro cars can only guess AFR since the O2 is absent.
J.P.

Loren,

ChrisBennet clarified my confusion between Motronic and CIS.