Pretty confusing statements there IMHO. Though I do agree, a AFM and MAF do measure air in different ways, the MAF providing much less pressure drop and constriction to the flow of air.

So let's divide the discussion up nto MAFs and AFMs.

*AFMS*
Here is the insides of a 944 Bosch AFM with a pretty extensive explanation of how it works http://frwilk.com/944dme/afm.htm

All the AFMs I've opened up have a potentiometer (slider) that varies it's angle according to airflow. Separately to that circuit is a temperture sensor. The temp sensor is directly connected via two pins to the AFM plug. The AFM does not integrate the temp sensor signal and the voltage corresponding to airflow at all.

*MAFS*
The MAFs I've seen too have a separate temperature sensor which too provides one or two pins on the MAF plug.

*ECU and temp sensor signal*
In either case, the temp sensor signal is fed back to the ECU to allow enrichment or lean out of the fuelling at cold or warm environment's respectively. Again, the AFM or MAF never integrated internally the two separate signals of temperature and airflow.

*Comments*
By all means, if you know otherwise I suggest post a schematic of the MAF so we people on this forum can evaluate the accuracy of such information presented.

sjsj

 

pics? you want pics? ok, this one has the pulse fired plasma plugs - as you can clearly see - they work wonders.... more here http://www.rense.com/general29/astn.htm

 

Nope, different picture to what I see. This one is the inside of a Porsche 944 Bosch AFM from http://frwilk.com/944dme/afm.htm. Also a pretty extensive explanation of how it works .

sjsj

 

The 928 Bosch MAF does not output a separate air temperature signal. The output of the MAF is mass air flow per unit of time. The Mass part of MAF means the mass of air. That includes the air temperature as well as the atmospheric pressure and velocity of air passing through it. The output of the MAF can be used directly to determine how much fuel should be used. Compensation for engine temperature is required, but that's all. The MAF schematic is in your 928 shop manual.

 

For some odd reason you keep ignoring my questions on both threads, so let's try this again .............AND WHAT KIND OF CAR IS THIS (BRAND, MODEL, YEAR...ECT.), PREHAPS A PIC OR TWO????????

 

 

AAAAHHHHH, finally something that leaves sjsj speechless?

 

Prefer this pretty pic myself. Always like to look inside things. This is the Porsche 944 Bosch AFM from http://frwilk.com/944dme/afm.htm. Also a pretty extensive explanation of how it works .

I find this makes me

 

Sorry, but I don't see any of your cars on that site. It's all theory and testing of individual parts. It's a collections of information copied from other sites. No signs of an actually running and preforming vehicle.

 

Imo, time to bring the Ferrari back IMHO.

 

Yup. I know exactly how the AFM works. I've had my share of swapping around AFM electronics into larger housings, tuning AFMs, converting them to MAFs, AND I have a pretty decent grasp of electronics!

As far as the rest of it, I 100% agree with what Louie stated:

"The 928 Bosch MAF does not output a separate air temperature signal. The output of the MAF is mass air flow per unit of time. The Mass part of MAF means the mass of air. That includes the air temperature as well as the atmospheric pressure and velocity of air passing through it. The output of the MAF can be used directly to determine how much fuel should be used. Compensation for engine temperature is required, but that's all. The MAF schematic is in your 928 shop manual."

 

hmm? I work in El Segundo... and live about 10 minutes away from it.

 

Point taken and correct. The MAF does measure the volume and density of the incoming air.

Another random piece of information just in case you didn't know.
[Google is your friend!]

 

Yeah, i meant tony. I like the fella, and know he knows his stuff, so that's why i threw the no offense in there for him.

 

Hi all,

I read this thread, had some good laughs, and have until now resisted from posting, but what the heck. Let's insert some science here:

1. Spark plugs igniting a 40:1 mixture
Not possible. The flame-front just would not propagate. A plug just ignites the mixture, but it has to burn by itself after ignition. At 40:1 homogenious mixture the dilution by air is large enough to quench the flame. Result is no burn.
If the spark were so powerful that it by itself can combust such a lean mixture, it would require more energy than the engine produces.
Lean burn engines that ARE running that lean or leaner, use stratified charge where part of the combustion chamber is filled with a richer, burnable mixture and the rest is made up with air or leftover exh. gas to keep dynamic CR and therefore efficiency up.
I've seen many spark-plug designs that supposedly increase combustion efficiency. None of them work. Mostly because they violate some of the most basic physical principle: A spark arcs from the point of maximum field. After it establishes a path, it continues to go through that path. Multiple or split electrodes just don't change that fact.

2. Widebands reading only to 30 AFR.
No, the sensors read fine up to free air (infinite AFR). Some controllers limit their readout to 20 or 30 AFR.

3. Water injection increasing power
Not in an unmodified engine. Water vapor actually displaces some air and therefore LOWERS overall a/f charge. Minor gains in combustion efficiency by helping in the CO -> CO2 conversion process offset that somewhat.
With increased CR, gains can be realized. Static CR of 14:1 to 15:1 is reportedly possible with WI with attendand increase in efficiency. Turbo engines benefit from decreased knock probability under boost.
Problem for production engines is that the user has to worry about 2 "fuels", and if running out of water would quickly destroy the engine. Filling with tap-water, which a lot of regular users would do at some time, can quickly clog the injectors from disolved carbonates. Too great a danger of warranty claims for manuf.

4. NB sensors can be used as tuning device
Not possible. The Nernst equation, which determines the output voltage of the sensor has a temperature term. Whan calculating the their output voltage purely from those equations (actual sensors differ from that even more), the same output voltage of for example 880mV is produced at 10.1 AFR and 900 degC sensor temp or at 14.1 AFR at 500 degC. There ain't no such thing as a free lunch. If it were possible, OEMs would waste money installing widebands if NB sensors could do the job.

The best of the cheap performance tuning tools has not been mentioned in this thread. It's a carpet knife. You use it to cut out a section of the carpet behind the gas pedal. That allows more WOT.

A fuel saving tip I found on another forum should be here also. The poster noted that his fuel gauge shows a much fuller tank when going downhill. He (correctly) concluded the engine uses less fuel when going downhill. His suggested solution, keeping with the spirit of this here thread of new approaches, was to jack up the rear suspension so the engine is "fooled" into thinking it goes downhill and therefore requires less fuel.



Regards,
Klaus