Any updates on the MAF progress?

 

Just passed a major milestone on the MAF project!

On Friday I finished all of the pre-alpha MAF firmware and corresponding updates to the FocusOBD software but ran out time for a systems test. This morning I woke up early to setup the AFM and MAF on the airflow bench. They are in series (Pictured Below), so the airflow though the AFM is the same as the airflow though the MAF. I am pleased to report the simulated AFM voltage derived from the MAF signal was within +/- 0.05 volts through the entire measurable range! That is absolutely fantastic especially considering this is the first full integration of the MAF controller. With some minor adjustments to the calibration tables, I am sure I can get that down to practically zero error. There is still some small quirks and issues I need to iron out, but so far everything is working better than expected. I should be able to bolt this MAF/AFM setup into my 944 next week for some road testing while running off the AFM signal and logging MAF controller data. If the data looks good, I will remove the AFM and run the engine entirely off the MAF!



Pictured is a custom F9T MAF housing than measures airflow in the reverse direction for development. It is in series with the AFM to verify the processed MAF signal matches the AFM signal under all driveling conditions.

 

Awesome!!!!!

 

Joe, thanks for the update! Per your latest Instagram post and reply to a question, you stated your MAF system utilizes a "controller" instead of being a "kit" and can thus support additional MAF sensors. Does that mean my Ftech9 DME OBD+ could directly support the Bosch MAF sensor included in the SciVision kit I currently have installed? Thanks.

 

Yes, that is exactly right, you can potentially keep your existing MAF setup. However, a new calibration table for the MAF and IAT will need to be generated. The MAF table is relatively easy to calibrate on my flow bench. The IAT sensor is more difficult because it must be cooled to -40F to maybe 200F to fully capture its NTC (Negative Temperature Coefficient) response.

- Joe

 

Another huge milestone for the MAF Project!

I became a little impatient and decided to jump ahead of my development plan and do a full road test using the calibration tables from my bench setup. I knew it would not be perfect, but close enough for a proof of concept. The test drive was amazing, everything you would expect from a MAF sensor was realized! The throttle felt light and responsive. Also, the performance improvement was undeniable. Remarkably this was using a stock 944 NA chip. I can’t wait to try out some performance tunes, especially the RT NA-Tune. There is still a lot of work to be done, but at this point we are very close to Alpha testing. Below is a picture of the F9T MAF sensor installed in my 1985.5 944 NA just after the test drive.




-Joe

 

Fantastic 😂

 

Great job ??

 

Great job!!

 

Joe, here's the info on my Bosch "hot-film air-mass meter," as Bosch calls it. I think this should be all the info you need to make the correct tables to support this sensor. This sensor is installed in a "stealth" configuration in place of the stock AFM. The system uses a little converter harness with some unknown configuration of electrical components encased in shrink-wrap. The sensor receives power from the 14-pole connector next to the firewall, and the converter harness plugs into the stock AFM connector; no special chips are required. It works OK... but I've always wondered how accurate the conversion process is as these SciVision MAF kits did not remain on the market long. I'll have to check the sensor P/N for the correct flow table. This kit was installed when my son owned the 951 and it was never driven hard in this configuration as he was always chasing boost/no boost problems... and I still am, ha, ha.

Thanks for the update on the MAF installation in your NA 944. Sounds like some great progress! Looking forward to what the new year will bring.

All the best.

 

Exciting times!
Question.. If i purchase the Sport OBD+ box now, will I have to send the box back once the MAF work is done, or will that be an internet software upgrade only? Just trying to minimize car downtime.
thx.

 

This will just be a software/firmware upgrade, the OBD+ Sport DME has had the electronics to support MAF for some time now.

-Joe

 

Thanks, Joe. will be ordering. I have a Lindsey Racing upgraded chip. should I leave it installed or removed??

 

I would recommend you remove the LR chip, in the unlikely event it was damaged I would not be able to replace it.

- Joe

 

The datasheet for your Bosch MAF sensor has the information to generate a reasonable calibration table. However, it assumes perfectly laminar airflow which is never the case in practice. Everything in the intake path creates airflow disruptions including the ductwork, air filter and throttle body. This is especially true at idle when airflow velocity is at its lowest point. For this reason, corrections from the ideal signal response will likely be necessary. The DME can use the NBO2 sensor to trim the fuel and attempt achieve stoichiometric AFR, however this has limits. This fuel "trim" only has a narrow window it can adapt. It is also a slow process and cannot respond to fast transient lean/rich conditions. Gasoline engines normally require fuel trimming, especially as they age, so you want the uncorrected AFR to be as close to ideal as possible for the closed-loop AFR adjustment to do its job over the long term.

-Joe