Which way to turn 3.2 air flow disk?

[Discseven]

Want to lean the fuel out by adjusting the spring-disk in the air flow sensor. Am not sure what direction to turn it.

[proporsche]

this might help

[76FJ55]

Originally Posted by Discseven

Want to lean the fuel out by adjusting the spring-disk in the air flow sensor. Am not sure what direction to turn it.

What is the issue you are having?

What mods have you done to the engine?

Unless the answer to the above is something extreme, I'd have a hard time believing the spring needs to be changed.

There is also a bypass screw (Idle Mixture Screw) that will adjust mixture on the AFM. it has the most effect at low flow rates, but will have a slight effect throughout the full range.

[Discseven]

Originally Posted by proporsche

this might help

Thank you Pro. It confirms previous input I got but was unsure of.

Originally Posted by 76FJ55

What is the issue you are having?

What mods have you done to the engine?

Unless the answer to the above is something extreme, I'd have a hard time believing the spring needs to be changed.

There is also a bypass screw (Idle Mixture Screw) that will adjust mixture on the AFM. it has the most effect at low flow rates, but will have a slight effect throughout the full range.

Issue is 11 mpg city after rebuild. Prior to rebuild I was getting 18. The 11 mpg result was had with driving the pedal in the same manner as when getting 18 so the test is "apples to apples." Engine starts on first crank, idles at 800 evenly, and pulls well. So everything is in order except for the fuel consumption.

Mods to 3.2 rebuild are 964 cams timed to 1.45 exactly on both sides, SSI exhausts, 2 in 1 out Dansk muffler.

There are new fly wheel sensors. New #3 cylinder temp sensor. New Bosch Ox sensor however I did solder-splice a few inches of wire into the stock length as the SSI exhaust bung is further back than the stock position (and I wanted to keep the cable/wires running through the stock tin hole. I was advised to check the area around the Ox sensor (thanks Pete) to ensure there was ample ambient air getting to it. There is.

ECU was "rebuilt" as part of engine rebuild but afterwards I discovered the ECU was swapped on me. If I can't find a solution that excludes the ECU, I'll be returning to that. There is a rotary fuel setting in a 3.2 ECU that is adjustable. I found this switch in the swapped unit set to the factory's 0 position. I turned it to #3 position. Specs for this rotary fuel switch are on Wong's website https://www.911chips.com/fuelsys.html Unfortunately I do not know what my prior ECU rotary fuel switch was set to.

Regarding the air flow adjustment, I was advised to first clean the air filter... Done. Found it only very slightly dirty and so consider this factor inconsequential. Then, rotate the disk inside the air flow 4 notches to increase the tension on the air flap. Direction of rotation for increasing tension is clock wise. Then drive the car. If it runs good, tighten the tension another 4 notches. When the car starts to run poorly, return to the prior setting. Then test the mpg. I tested the 4 notch adjustment and the car ran fine. Have gone another 4 notches now but have yet to drive the car. Get to that tomorrow.

When I first discovered the milage having dropped, I looked at the exhaust pipe and found the insides covered with black soot. I've cleaned the exhaust now and will be looking at it after adding some miles to the car.

[76FJ55]

What are you running for fuel pressure regulator and dampers? Are you still running stock fuel injectors or have they been swapped out?

Do you have access to a wide band O2 setup? It may be worth borrowing or purchasing one if you are going to be trying to adjust mixture.

[Discseven]

Originally Posted by 76FJ55

What are you running for fuel pressure regulator and dampers? Are you still running stock fuel injectors or have they been swapped out?

Do you have access to a wide band O2 setup? It may be worth borrowing or purchasing one if you are going to be trying to adjust mixture.

Reg & damp are stock. Injectors are mine from before the rebuild, Lucas brand. I don't have a wide band but friend has an Ox meter that sticks into tail pipe. If adjusting the air flow disk---or whatever adjustment is made---gets the mpgs back in order, I can surely borrow his to fine tune.

[brianlay]

There are new fly wheel sensors. New #3 cylinder temp sensor. New Bosch Ox sensor however I did solder-splice a few inches of wire into the stock length as the SSI exhaust bung is further back than the stock position (and I wanted to keep the cable/wires running through the stock tin hole. I was advised to check the area around the Ox sensor (thanks Pete) to ensure there was ample ambient air getting to it. There is.

Using solder on the Oxygen sensor wires is not advised since the sensor "breathes" outside air through the wires.
Normally the sensor will correct the average air/fuel ratio to keep it close to ideal.

[Discseven]

Originally Posted by brianlay

Using solder on the Oxygen sensor wires is not advised since the sensor "breathes" outside air through the wires.
Normally the sensor will correct the average air/fuel ratio to keep it close to ideal.

Here's how the Ox sensor and wiring is set up. Can see a slight buldge in the black sheathing a few inches from where it starts... that is location of the splices. Discovering the mpg in the gutter, I was initially concerned about adding the 6" or so of wires and solder to this sensor as this might have affected resistance in the wires. Don't know if the signal from the OX sensor is resistance based and so that being pure speculation on my part. I have it on good authority that this wire addition & soldering business is not a problem.

[brianlay]

It's not the additional wire that's a problem, it's the solder.
This is why the Bosch universal sensors come with a crimp connector.
Search the web and you'll find many discussions like this...nobody recommends solder.
https://rennlist.com/forums/924-931-944-951-968-forum/645703-o2-splice-crimp-only-or-solder-too.html

[Discseven]

Here's what I found when test driving 8 notch adjustment. (Am continuing to tighten tension of air flow spring-disk / air flap.)

Starts on first crank. Very slight roughness in idle compared to 4 notch adjustment. After op temp reached (210 df) drove engine to redline several times... consistently pulls all the way without a hint of stumble. One issue: stalled at red light when not warm. Wanted to stall at idle after warm up but touch on the pedal keeps engine running.

Plan...

Am going to adjust the idle rpm up slightly (900-1000) and run the 8 notch adjustment to see what comes of this. Post results when I have them. Until this puzzle is truly solved, doors open for ideas.
.

[mysocal911]

Originally Posted by Discseven

Thank you Pro. It confirms previous input I got but was unsure of.

Issue is 11 mpg city after rebuild. Prior to rebuild I was getting 18. The 11 mpg result was had with driving the pedal in the same manner as when getting 18 so the test is "apples to apples." Engine starts on first crank, idles at 800 evenly, and pulls well. So everything is in order except for the fuel consumption.

Mods to 3.2 rebuild are 964 cams timed to 1.45 exactly on both sides, SSI exhausts, 2 in 1 out Dansk muffler.

There are new fly wheel sensors. New #3 cylinder temp sensor. New Bosch Ox sensor however I did solder-splice a few inches of wire into the stock length as the SSI exhaust bung is further back than the stock position (and I wanted to keep the cable/wires running through the stock tin hole. I was advised to check the area around the Ox sensor (thanks Pete) to ensure there was ample ambient air getting to it. There is.

ECU was "rebuilt" as part of engine rebuild but afterwards I discovered the ECU was swapped on me.

That's NOT good! Now you have potentially another problem. Who's the "rebuilder".

Originally Posted by Discseven

If I can't find a solution that excludes the ECU, I'll be returning to that. There is a rotary fuel setting in a 3.2 ECU that is adjustable. I found this switch in the swapped unit set to the factory's 0 position. I turned it to #3 position. Specs for this rotary fuel switch are on Wong's website https://www.911chips.com/fuelsys.html Unfortunately I do not know what my prior ECU rotary fuel switch was set to.

Regarding the air flow adjustment, I was advised to first clean the air filter... Done. Found it only very slightly dirty and so consider this factor inconsequential. Then, rotate the disk inside the air flow 4 notches to increase the tension on the air flap. Direction of rotation for increasing tension is clock wise. Then drive the car. If it runs good, tighten the tension another 4 notches. When the car starts to run poorly, return to the prior setting. Then test the mpg. I tested the 4 notch adjustment and the car ran fine. Have gone another 4 notches now but have yet to drive the car. Get to that tomorrow.

When I first discovered the milage having dropped, I looked at the exhaust pipe and found the insides covered with black soot. I've cleaned the exhaust now and will be looking at it after adding some miles to the car.

Has very little effect on the engine's running. It's propose is for tweaking the emissions for some countries.

[Discseven]

Originally Posted by brianlay

It's not the additional wire that's a problem, it's the solder.
This is why the Bosch universal sensors come with a crimp connector.
Search the web and you'll find many discussions like this...nobody recommends solder.
https://rennlist.com/forums/924-931-944-951-968-forum/645703-o2-splice-crimp-only-or-solder-too.html

This is interesting info Brian. Thank you! Looked at Rennlist and info on Clark's Garage page. Clark's info is 944 related but I suspect an Ox sensor is the same in functionality across the board.

This is text posted on Rennlist. I do not recall what the Bosh wires looked like when I worked with them but know I soldered in copper wiring of the same gauge.




Info from Clark's Garage...





Given this, and assuming the info is correct, handwriting's on the wall. Blurry at this stage but there. Will have to dive into more experimenting to find clarity.

Plan update...

Am going to run the 8 notch setting and adjust the idle... to see what mpg comes of this is given (since the set up is nearly in place.) After that, will return the air flow notch setting back to the original position. Will leave ECU adjustment to #3 fuel position as is. Cut the soldered Ox splice (that I put in) out and crimp the Bosch wires back together. That set up will have to pass between the engine bay seal and engine tin to make the connections (given SSI's placement of their bung.) If this direction solves the puzzle, will consider locating a proper hole in the tin for the shorter Ox cable. I don't recall the Bosch wires being of a config that allows air to travel along the wires to the sensor but then I've f'd up a few things here so am eating crow as it is. Next, will check engine performance and mpg with the splice out and crimps in. Later readjust idle if needed. Of course will post what is found. Brian, accolades pend. Ultimately I stick a portable OX meter in the exhaust to fine tune the AF ratio.
.

[spuggy]

Originally Posted by Discseven

New Bosch Ox sensor however I did solder-splice a few inches of wire into the stock length ... I was advised to check the area around the Ox sensor (thanks Pete) to ensure there was ample ambient air getting to it. There is.

The body of the O2 sensor is completely air tight and sealed (to prevent contamination, because they tend to be located where it's kind of nasty). Getting ambient air to the sensor body doesn't matter at all. Because sealed.

The O2 sensor requires a supply of ambient air in order to perform the chemical conversion.

The O2 sensor is designed to obtain this ambient air through the strands of the cable

Not only is this called out in all the Tech Docs since Bosch invented the thing, the universal installation kit provides screw-type connectors (Posi-Locks) to splice to the OE harness. And some (but not all) instructions specifically warn against soldering the cable or using heat-shrink.

eg, from Oxygen Sensors Trade Brochure (the bolded emphasis is Bosch's):

Oxygen sensors need a reference air sample to compare against the exhaust gas to be able to produce a signal. This sample is drawn into the oxygen sensor from the outside, but there are different methods to get this air into the sensor. Bosch Oxygen Sensors are the only sensors that draw air from the connector and through the wires to ensure the reference air sample is clean and to keep contaminates out. We believe this makes our oxygen sensors more robust, so that you only have to do the job once.

[Discseven]

Originally Posted by mysocal911

That's NOT good! Now you have potentially another problem. Who's the "rebuilder".

Has very little effect on the engine's running. It's propose is for tweaking the emissions for some countries.

Dave... ECU was handled by Vertex. A Miami shop. Why the ECU went to them is a long story not worth getting into. Suffice it to say I'm not pleased with this ECU situation and will discuss it with parties when the time is right. On the rotary switch inside the ECU for fuel adjustment, agreed. Specs for the #3 position are a "correction" of - 3.9%. Peanuts but still something.
.

[Discseven]

Originally Posted by spuggy

The body of the O2 sensor is completely air tight and sealed (to prevent contamination, because they tend to be located where it's kind of nasty). Getting ambient air to the sensor body doesn't matter at all. Because sealed.

The O2 sensor requires a supply of ambient air in order to perform the chemical conversion.

The O2 sensor is designed to obtain this ambient air through the strands of the cable

Not only is this called out in all the Tech Docs since Bosch invented the thing, the universal installation kit provides screw-type connectors (Posi-Locks) to splice to the OE harness. And some (but not all) instructions specifically warn against soldering the cable or using heat-shrink.

eg, from Oxygen Sensors Trade Brochure (the bolded emphasis is Bosch's):

Spuggy... thank you. Am truly getting Ox schooled as this thread progresses. ALL GOOD! Here's Bosch info...



Bosch language about drawing air "through the wires" suggests the wires being air conductive. Or is this marketing? Were my plate not loaded already, this would be something to research.
.

[brianlay]

I believe if you get a working O2 sensor if will solve your overly rich mixture problem.

FWIW, I did punch another hole in the tin to allow the stock 02 sensor to work with my SSIs.

[pmax]

The ECU has been swapped. Who knows what fuel map is in there.

Have you opened it up and have a look see at the chip, they being labelled typically by the modder ?

[mysocal911]

Originally Posted by pmax

The ECU has been swapped. Who knows what fuel map is in there.

Have you opened it up and have a look see at the chip, they being labelled typically by the modder ?

Excellent point! Found this Pelican Parts post related to 911 3.2 "chip tuning";

http://forums.pelicanparts.com/porsche-911-technical-forum/683503-performance-tuning-myth.html

[Discseven]

Originally Posted by brianlay

I believe if you get a working O2 sensor if will solve your overly rich mixture problem.

FWIW, I did punch another hole in the tin to allow the stock 02 sensor to work with my SSIs.

Am sensing that too. Have adjusted idle and will test run engine as it stands tomorrow, if for no other purpose than to see what comes of the standing config. Result notes on that tomorrow.

Did you gromet the hole? How / with what?

Originally Posted by pmax

The ECU has been swapped. Who knows what fuel map is in there.

Have you opened it up and have a look see at the chip, they being labelled typically by the modder ?

Good point P. I have opened the ECU and to my eyeballs, it's clean and everything looks in order. Am not an ECU expert so my view is entirely superficial. I did not look at any chip in particular. Nor did I see any notes or stickers on anything. I'll open it up again for this. Could you post a pic of or direct me to what / where I should be looking?

After test running the current config, and if the Ox correction is not a solution (as info suggests it will be)... and if no other possibilities arise and there's still an issue, ECU mapping would be next on the menu. I'd then be discussing the ECU "swap" with the responsible party. There's an ECU specialist in Lauderdale https://www.ecudoctors.com/pages/149-testing-service . I might pay them to test the unit.
.

[spuggy]

Originally Posted by mysocal911

Excellent point! Found this Pelican Parts post related to 911 3.2 "chip tuning";

Oh, still pretending you're not Loren?