Replace AFM by MAP

24th February 2004 Night

Part 2 - Re-test

This 2nd attempt is tested even knowing the odds are not in favor. This is simply to confirm the previous "understanding" of the "engine's aspiration" behavior, namely the vacuum part versus air flow.

Not only that, it also answers the curiosity once and for all of the chances of success.

Now this time a proper vacuum sensor is found and used. Not the wrong pressure sensor.

Two of the vacuum hoses needs to be blocked of, else the engine dies immediately upon start. If the hoses are not block, then can be simply stuck into any throttle to complete the vacuum loop and it will do. Yes I've tested it.

The ISC Valve must be left open to breath.

The result is rewarding ........................................................... 

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....................... with the sound .............................................

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..............................................................of the fearsome 4 throttles :)

No it did not work completely nor properly.

The result is as expected but a little better.

1st - it will idle perfectly - because using the converter to achieve 3.1 volt

2nd - it will rev strongly, willingly, loudly, powerfully :) no problems here

3rd - the ultimate requirement - it will not maintain proper aspiration during partial throttle hold. 

The engine will go into rough breathing, choking at times and then dies.

This is much much better than before where it could not even maintain aspiration as long as this.

The converter's setting is proofing difficult to set. The gain stage is extremely sensitive and often too much gain and too quickly.

The converter's overall off-set has been extremely useful in this case.

The setting combination was found to be: - (until it was realised that the gain was too strong, too much and too quick)

1. reduce gain to minimum i.e. no amplification of signal

2. overall off-set to 3.1 volt

3. mess with the throttle

4. read the output voltage from the converter

5. no response = gain too little

6. increase gain very little

7. repeat 4, 5, 6

8. until at sudden throttle there is sudden 

9. and the more thrttle applied the lower the voltage becomes

The partial throttle hold problem is that after engine reached desired rpm the vacuum would stabilizes and reduce back to around 22 IN Hg. This is not the same as air flow where more rpm requires more air then more flap opens and less voltage.

When vacuum changes after desired engine speed is achieved the ECU L-jetronic in this case reads a completely different scenario and delivers fuel and ignition in an un match manner and causes the engine's aspiration to be out of tune. This is unfortunate.