Discussion
Gerry Attrick said:
I'm trying to finalise the retune on my 350i flapper version injection system after it was bodged. Does anyone know the CO readings at anything other than idle? 30 or 50 mph for example?
Thanks
Don
Tasmania seems to know al lthings to do with Flappers
ooe er misses
Mark Adams would be another good source of info.
adam quantrill said:
I tune for just under 1% CO at idle (for the MOT)
then I put it back for what it likes after.
Wow. That's weak. I thought the MOT allowed anything below 3.5%.
The problem I have is that the tension on the flap in the air meter was changed to overcome a hesitancy problem, and I need to get it back to the original condition. I have set the idle at 2.5%, and it appears to work well in the low throttle positions. I now need to adjust the flapper spring to get it right throughout the rest of the range. Once this is done I can then go back and reset the idle. I need a CO setting at some point at a higher speed to set to.
Hi Don
There is only accurate method of setting flap type airflow meter spring tension, and a part throttle CO value won't really help you.
You can only set up the CO AFTER the spring tension has been set.
Setup is best done on a Rolling Road, but can be done on the street with an assistant. The tension has to be adjusted so that the flap is almost fully open (99.5-99.7% according to atmospheric conditions) at full power.
Basically this sets the full operating range of the airflow meter. After this is achieved you can trim the full load CO, then set the idle CO. Everything else should fall into place.
Your best option is to book an hour on a rolling road with someone who knows what they are doing, and will save you hours of trial and error. If you let us know the region you are in, I may be able to refer you to someone good in your area.
It is possible to roughly calibrate the meter on the street, by using a digital multimeter to tell you when the flap is nearing fully open. This is where you need an assistant to note the highest reading whilst you nail it flat out.
However this still won't tell you the full load CO. If you need more info then please just post back here.
There is only accurate method of setting flap type airflow meter spring tension, and a part throttle CO value won't really help you.
You can only set up the CO AFTER the spring tension has been set.
Setup is best done on a Rolling Road, but can be done on the street with an assistant. The tension has to be adjusted so that the flap is almost fully open (99.5-99.7% according to atmospheric conditions) at full power.
Basically this sets the full operating range of the airflow meter. After this is achieved you can trim the full load CO, then set the idle CO. Everything else should fall into place.
Your best option is to book an hour on a rolling road with someone who knows what they are doing, and will save you hours of trial and error. If you let us know the region you are in, I may be able to refer you to someone good in your area.
It is possible to roughly calibrate the meter on the street, by using a digital multimeter to tell you when the flap is nearing fully open. This is where you need an assistant to note the highest reading whilst you nail it flat out.
However this still won't tell you the full load CO. If you need more info then please just post back here.
Hello Mark.
Thanks for the information. Sounds like I've got the wrong idea on how the system works. I assumed that the amount the flap opened sent a signal to the ECU to set the fuel output. Hence a lower tension on the flap, the further it opened for any given air flow and the more fuel was injected.
For entertainment value, I'd like to try to set it up myself. Are the details of the pins to measure from, in the bible (I'm on a business trip at present, so away from home)? If not can you tell me which ones? Once the flap spring tension has been set, how is the CO adjusted at points other than idle?
Thanks for the information. Sounds like I've got the wrong idea on how the system works. I assumed that the amount the flap opened sent a signal to the ECU to set the fuel output. Hence a lower tension on the flap, the further it opened for any given air flow and the more fuel was injected.
For entertainment value, I'd like to try to set it up myself. Are the details of the pins to measure from, in the bible (I'm on a business trip at present, so away from home)? If not can you tell me which ones? Once the flap spring tension has been set, how is the CO adjusted at points other than idle?
Details of pinouts of AFM
disconnect the multi-plug from the air flow sensor.
connect an ohm-meter between terminals 6&8 then 6&9 then 8&9 and compare the
resistances to:
6&8 = 350-370 ohms
6&9 = 550-570 ohms
8&9 = 190-210 ohms
reconnect the plug and switch on the ignition,peel back the rubber cover on
the plug. connect +ve probe to pin7,-ve to pin9, open flap and watch voltage
decrease as voltage goes through each resistor pack just measured.
connect ohm-meter between pins 6&27 for air temp. correcton, compare to:
-10deg.C 9.2 Kohms
0 deg 5.9 Kohms
20deg 2.5Kohms
40deg 1.2Kohms
also throttle pot: connect between red&green wires, ignition on : 0.27-0.31
volts.
.
disconnect the multi-plug from the air flow sensor.
connect an ohm-meter between terminals 6&8 then 6&9 then 8&9 and compare the
resistances to:
6&8 = 350-370 ohms
6&9 = 550-570 ohms
8&9 = 190-210 ohms
reconnect the plug and switch on the ignition,peel back the rubber cover on
the plug. connect +ve probe to pin7,-ve to pin9, open flap and watch voltage
decrease as voltage goes through each resistor pack just measured.
connect ohm-meter between pins 6&27 for air temp. correcton, compare to:
-10deg.C 9.2 Kohms
0 deg 5.9 Kohms
20deg 2.5Kohms
40deg 1.2Kohms
also throttle pot: connect between red&green wires, ignition on : 0.27-0.31
volts.
.
I've just been modding the larger Jag AFM for my 390; just to get it to idle correctly I had to retension. What I found was that the voltage on the original AFM pot wiper (terminal 7) was 2.7V at idle (approx. 750 rpm), so I altered the Jag AFM spring tension till I got 2V7 and hey presto, reasonable idle. The voltage reduces as the flap opens further; as there's only 2V7 to start with, you can see that the adjustment is pretty sharp... of course I haven't been able to drive the 390 with the AFM hanging off, so I know that I'll have to fine-tune it once it's mounted correctly but hey, at least it works now! 
Ian
Ian
adam quantrill said:
I tune for just under 1% CO at idle (for the MOT)
then I put it back for what it likes after.
Sometimes I have to add an extra bypass pipe to
the air meter as I run with a rising rate regulator.
- Adam
Adam,
Could you enlighten me why and how, on the extra bypass pipe you mentioned. I have a rising rate regulator as well, but have changed nothing related to air intake.
Rob
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