Porsche Enthusiasts Club Forum

I have an S2 cab without a cat or an O2 sensor
Am I correct that 944's without an O2 sensor determine the amount of fuel delivered by the injectors only by the engines RPM, given that at full throttle the AFM table is ignores and the WOT table is used, also I believe that the AFM is wide open around 4K RPM.
If this is correct, then I'm a little bit amazed as our cars could be way off in fuelling, with no O2 sensor there is no way to "trim" the fuel tables to take into consideration things like gummed injectors, fuel pressure etc,
I'm basically looking to justify the outlay of a VEMS/Augtronic system, one that with the addition of a Wideband O2 sensor will tune itself with 30 year old components
Steve

Wouldn't it make more sense to replace FPR (about £50)and get the injectors serviced (£15 each) than fork out for a new ecu.

Yes I agree, but If I am right then I'm amazed that there is no way of our engines to monitor what's going on and the fuelling purely relies on the asumption that everything is working ok and is of original design,
What if you've replaced the exhaust and air filter to allow the engine to breathe better, will the engine run leaner?
What happens if the prm sensor fails,
How much, if any increase in power and fuel effiency will there be in fitting a modern engine managment which will monitor and fine tune fuelling/ignition etc

9m claim significant power increases by using a Motec engine management system on 993 alone instead of the Motronic. If the VEMS or Augtronic can get rid of the barn door at least that's a step forward. The Scanvision MAF kit does not cater for air intake temperature and tends to run lean when cold and rich when hot, theoretically not needed with a MAF but the ecu doesn't know that. I never realised that the AFM was fully open after 4000 rpm which is probably why the Scanvision seems to work well on the track. Power output of an S2 seems very conservative especially compared to my old MGA pushrod which produced 135 bhp from 1600cc on a single 45DCOE or the Twin Cam MGA on twin 40's same bhp but terrible low end torque. The pushrod was always quicker on the track.
I'm using a Promax chip and the S2 feels very smooth especially after replacing the FPR which was causing occasional misfiring, but it's still no rocket ship. Then it has done a very reliable 100,000 miles whereas the MGA engines needed a full rebuild every season if they didin't blow up before that.