MAF and AFM question
 

In looking at the diagrams in the Haynes, it looks like the 89 went to a more volumetrically efficient (aka not the crappy dreaded trap door that I now have on both my Porsche AND RX7) maf style air flow metering system. Has anyone ever successfully used the later maf unit rather than the 86-88 cruddy trap door unit? I know we find huge gains in the Porsches by dropping the AFM and going either maf or map for air metering, but I hadn't seen anything about the possibility of retrofitting the newer style meter to the older cars...is this completely unrealistic, or could it be done? I'm not really looking to spend SDS or comparable money for a standalone system as this is a cheap ass budget built racecar, the Porsche sees most of the budget, but this sounded like something worth looking into.

TIA

It's been done and it makes practically no difference.

The S5 AFM is not a MAF (mass airflow, aka hot-wire) sensor, it's a sliding cone AFM. Both the S4 and S5 AFM's work on exactly the same principle. The flap or cone is pushed back further as airflow increases.

The S5 AFM actually has a slightly smaller inlet than the S4 one, and they both have the same outlet.

The only way to improve the AFM is to replace it with a bigger version of the same type and use a fuel computer (e.g. S-AFC) to tune its output to suit the ECU, or ditch both the AFM and ECU and get an aftermarket ECU that uses speed-density (MAP) for load sensing.

Has anyone experimented with the LINK system? This is a piggyback MAP that has been used with success on the cruddy Porsche design that is nearly identical physically to the Mazda system?

The Link ECU's are just another aftermarket ECU like all the rest. It's aimed towards the bottom of the market. I've never seen one on an FC over here (it's a NZ system), but there's bound to be some.

Check out www.bgsoflex.com/megsquirt.html and members.shaw.ca/megasquirt/MS%20FAQ.htm. The MegaSquirt is a MAP based fuel controller (laptop programmable) that you can get all the parts to for around $150. It will allow you to remove the MAF and use the stock ECU or a distributor to control timing. There are a couple of guys here on the forums that are running it already. I'm still in the process of building/installing mine, school is getting in the way. :-P

whats up with these megasquirts anyway, are they decent, hard to build. For that price i figured more people would use them

Why are you blaming the airflow meter for being a restriction?
Why are you getting cheap when you own a Porsche?
There are numerous optons in terms of aftermarket stand-alone EMS ECU's.
Is there a reason why you can't afford one?


-Ted