Murray

It may just be anecdotal but every time I disconnect the battery and reset the computers the car seems to run like a scalded cat after it. It just feels like the throttle response is better and it feels more free reving. Would there be any truth to this or am I just imagining things?

SeanR

Yup, happens. Especially when something like a knock sensor or hall sensor is not working right. Sometimes it takes a bit for a bad reading to come on and the computer will retard the timing.

docmirror

When the power is removed from the LH, it goes back to an open mode setting. This provides more fuel than normal to the engine until it learns the stoichiometry through the O2 sensor. The fuel economy will be worse, but the performance will be enhanced until the fuel is metered down some.

Murray

Seems like it should feel that way all the time. ;-)

FredR

Maybe your O2 sensor is sending a dodgy signal to the LH? You must ensure you know for sure both knock sensors and the Hall trigger are working correctly.

When we shark tune we are able to get more out of the motor because we custom tune both the LH and then the EZ units. For LH we are able to richen up the mid range and lean off the top end to get better better performance. For the EZ we able to dial in quite a bit more advance in performance critical cells.

All 928's here are open loop variants [they were supplied in the leaded gasoline era] so we do not experience this type of thing. At least with ST2 you can disable this loop and reinstate it any time you want.

Regards

Fred

John Speake

I assume you mean that after some miles the performance drops off again ?

Murray

The drop off in performance must be gradual because I don't really notice the degredation. And to be clear, the car still performs very well and is fast. But that first drive after a reset is really cool.

John Speake

All fault codes and adaptation parameters for O2 and idle loops are reset when doing a battery disconnect.

So for example, if you had a knock sensor fault code before the disconnect, then imediately after the reset performance would be restored because you would loose the 6 deg retard that is applied. But of course it would be applied again as soon as the EZK recognised the fault again.

That doesn't appear to be the case with your car.

After the reset, the O2 loop has to re-adapt. It starts with adaptation zero, it doesn't go open loop,(only until the water temp has risen to 70 degC or so, as always happens)

The LH gradually builds a set of corrections to the LH maps using information from the O2 sensor readings. It is trying to keep the O2 loop within the middle of its range so that it will cope with other variations. This process requires you to drive the car for several miles under varying load and RPM .

It would appear that in your case it is the LH adaptation that is the reason for the performance change you have noticed. It suggests that maybe your O2 sensor may have a problem. When was it last changed ?

Murray

I don't see any record of the O2 sensor being replaced. I am planning on an x-pipe installation this winter and was going to replace the O2 sensor at that time anyway.