If you search the vortex forum you'll find lots of posts from people who have successfully performed this mod, a complete rundown can be found in the 8v FAQ Edit: Origianlly found in this thread. Also if you feel like a long read, check out the serious MAF discussion thread, this was the long thread I was talking about earlier, I was getting mixed up with MAF & AFM again
This was the same thread I looked at when I attempted this "cheap" mod. In hindsight I should have noticed that Digiracer was the only person who claimed that this mod works. Back then Megasquirt was not as popular . It is obvious that the larger AFM would allow more airflow but take it from me its a nightmare to set-up and is rubbish! The flap should hit wide open from peak torque to max revs. But on the bmw AFM this is overcome by the heaver spring fitted. When you loose this spring you then have the problem that the flap does not close enough for idle AFR. Its all coming back to me. I tried modifing resistances on the low side then on the higher side and still no joy. Car also had cold starting issues from first start on a 10degC day and had a drinking problem. In the end I I had to conceed that VAG engineers knew what they were doing with the STD AFM and reinstalled. Car ran great. Reading about this is one thing, but do it and you may see what I mean. Not reccomended. AFM to MAF conversion is interesting for a couple more lbft and has already been suggested by poster mark25 who talked about the Split Second system. But I agree with prof on this. Too much messing about when a tried and tested solution is already there.
Hmm maybe you need to find an old one with a worn spring What about swapping the internals over, I have 2 spare AFMs... hmm. The main reason I'm not keen to try this is I bought a brand new AFM last year, so I want to get my use out of it
that what i was thinking about I know i had seen a picture before. the weak link seems to the afm. might have a look at the mega squirt system as it seem a sensible answer without spending hours messing around with something that may never work.
yeah thats the best solution, just think of all the cool things you can do with it hooked up to a laptop
finally the 2 stage throttle body should give a smother drive, as the change in airflow at small throttle openings is smaller, compared to an ABF one i suggested ABF as they run no AFM and a throttle pot based airflow calc system-much like emerald or DTA so a big enough throttle body, with megasquirt looks like a plan.
TPS based load sensing is an alfa-N system and this system is not normally used on road cars. Systems like Emerald and DTA have incorperated optional MAP sensing for fuel addition or spark retard as a percentage due to use and popularity of many forced induction motors as seen by members of this site and others. ABF motors use a speed density system or a MAP sensor to read load this is located inside the ECU module and give signal by a small vaccum hose. The 3 pin TPS is used for fuel enrichment, triggered by the rate of change of throttle voltage/opening (like carb diaphram or plunger). If you were to disconnect a the MAP sensor hose on an ABF motor while it is idling, the engine would go excessively rich as you would have just told the ECU you are full throttle or 100kpa and it would increase the injector opening time to the target AFR. On a Vag-Com this would also trigger a fault. SPi systems are mass airflow controlled or MAF controlled. Observe a unit carfully and you would see a small hole where the MAF sensor wires are located to measure airflow.
hey thanks for the info never actually ran my ABF, sold it before that, just remember the throttle TPS
Yes, ABF is MAP, with TPS optimisation. Electronics are needed to smooth the action of the one big TB flap. Effectively reproducing the effect of the old double TB on the k-jet and digi. Electronics and software are now cheap, the extra machining of the double tb is not cost effective. I think you might have got your wires crossed there.... SPi (Single Point Injection) is TPS.
Not too sure about the "wires crossed" part. However I not afraid to say that I am wrong here in commenting that the SPi system is a MAF system. VW SPi systems have a TPS for rate of opening, like the ABF, and a TVP (Throttle Valve Postioner) for valve postion.
Generally the basic ECUs run of a 2d map, eg rpm x TPS, (or MAP). This is open loop control and not optimal, as you need a safety margin in the map for all circumstances. You can then add a combustion sensor, eg Lamda, to optimise control to get closer to optimal combustion by fine tuning to take into acount variations that the 2d map doesn't even know exists. The lambda probe feeds back the result of combustion to form a closed loop. This is known as closed loop control and in the case of the narraow band Lamda, is optimal (for the catalytic convertor operation)... not power.
would i be better then to go for the open loop system and add a wideband o2 sensor to aid the management, or wil it just confuse things, including me.
ok, i take your point. The equipment needed is fairly straight forward my concern is mapping the thing once its installed, is the software user friendly or is it specialised?
