944 Chip Design.
- Thread starter barks944
- Start date
Yes Tom I went to the WRC with Tom (to many Toms). But it was all cut sort due them not wanting to drive on ice.[&:]
Will have a dig about for that info at the weekend.
It will be good to see this work, or do as I did blow your Lux up by trying to stay with faster cars then buy a turbo and you will be the faster car!!
Will have a dig about for that info at the weekend.
It will be good to see this work, or do as I did blow your Lux up by trying to stay with faster cars then buy a turbo and you will be the faster car!!
sawood12
New member
OK, the AFM does have an air temp sensor, but it is only sampled once at startup and is not used continuously. The mapping is compensated for the temp measured at startup. Therefore the ECU is not calculating mass flow.
Also the relationship between the 0v - 5v output of the AFM is not a linear one with respect to the air flowing through the device. As the airflow increases in speed the barn door opens, and as it opens it offers a reduced frontal area to the airflow, therefore the barn door opens at a differing rate to the increasing speed of the airflow.
Also at about 4krpm the barn door is fully open and so further calcs by the ECU are done on the basis of RPM and throttle position.
What you're after are features that are already available on severeral existing MAF kits. All these kits (well the decent and more pricey ones anyway) have a small computer that calculates the mass airflow and outputs a signal that can be interpreted by specialist code on the DME (i.e. not standard Bosch Motronic AFM code) so you are not tricking the ECU into thinking it is still seeing an AFM, you are converting the ECU into a device which is actually calculating the true mass airflow.
You can tell a proper MAF kit that calculates true mass airlfow if you don't need to re-chip it to suit varying boost pressures i.e. the Vitesse kit which is $1250 plus $850 for the Piggy back that offers you real time tuning capability with data-logging, closed loop AFR (either from the stock lambda sensor if you have it or from an aftermarket wideband sensor if it is a pre-cat car) and MAP based ignition mapping.
I'm not trying to put a dampener on your aspirations as it would indeed be an interesting project, but I wouldn't assume it is simple or easy in any way or necessarily cost effective. Given the time you'd need to invest and the probably cost to get it all working you'd probably have been better off with something like Megasquirt or the Vitesse kit.
One possibility (though i'm not sure if it has ever been attempted) is to use a 968 ECU and MAF sensor, as the 968 did have MAF.
I can get a MAF sensor for about 40 quid from ebay and the signal conditioning wouldnt need to be much more than pic chip a couple of DAC's and some time programming. I'm a control engineer so im happy enough designing the signal transmitter myself. Shouldn't cost much at all. I'm aware that the 944 uses throttle position at full throttle. As I say its one of the reasons you should not see any change in performance at full throttle.
Isnt that essentially a mass flow calculation...You are taking temperature and therefore density into account...Maybe you mean its not calculating true mass flow but its somthing analagous to it.
Isnt that essentially a mass flow calculation...You are taking temperature and therefore density into account...Maybe you mean its not calculating true mass flow but its somthing analagous to it.
sawood12
New member
Airlfow and massflow are not the same thing. However what you say is correct in that you could get it working by effectively tricking the ECU into thinking it still has an AFM - which clearly will work. Not sure you'll be getting the full benefit of MAF sensors though which sort of defeats the object in my mind. In fact i'm not sure exactly what benefit you'll get. If all you're trying to do is to fix idle stutter then a refurbed AFM will probably do that. My car got a nearly new AFM a couple of years ago and has since idled rock steady and there is no stutter or hesitation throughout the rev range - though AFR's are all over the place.
But anyway i'm one of these people who left my toolbox alone a long time ago and has become very lazy and will just go and buy an already established kit!
But anyway i'm one of these people who left my toolbox alone a long time ago and has become very lazy and will just go and buy an already established kit!
What I think I might get from this is better throttle response when not at full throttle. The MAF sensor should track changes in air flow much better than the barn door meter. This is known as lag in control systems and just means that the control system, in this case the DME, is working in the past. The more lag there is the further in the past the DME is working. Dont get me wrong I dont think it would make a massive difference but there may be some gains to be had. On the BMW's with motronic and in the link to the carlton that had MAF sensors fitted they noticed an improvement in throttle response.
The early rennlist discussion on the scivision maf was very similar, look here http://forums.rennlist.com/rennforums/showthread.php?t=135576
Tony
Tony
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