MAP manipulations

[rauscher at icst.com]

John, you have a valid question, so don't take this the wrong way:
this is really, really easy to do. I can't believe that they get 300 to 500
bucks for this unit. Maybe a 100 after the case & connectors. (maybe
this is not in US dollars?).

The gain and offset changes can be done with a single op-amp. A zener to
limit the output, another op-amp to buffer this, and a capacitor on the first
op-amp as a filter. The 5v out from a 7805 3-terminal regulator.

Maybe I'm speaking too hastily, but I don't think so.

As to the 'why', yes if all you did to your engine was up the FP, or put in
larger injectors, you could tune it in better. But, you might go crazy if you
didn't remember to reset the ECM to zero out the BLM between changes.

What this unit will do, is shift the VE & spark tables along the MAP axis.
Oh, probably change when the PE kicks in relative to the MAP also. Maybe
this is where most gains are from, as the INT and BLM will 'undo' a lot of
what you 'did' with this unit.

If you changed the cam,  this will change the  entire (or most of) the VE
table. I don't believe that the below device will do 'enough' to bring the
tuning back in. As the VE table peaks and valleys areas will
have changed.

Then again, if the ECM this unit is used on, doesn't 'learn',  then it might
do more then the above mentioned.

As for as my thoughts on the need to change the MAP output, yes, I
have been thinking of one: On a radically cam'd engine, smoothing of
the MAP output, at idle only, may be beneficial.

BobR.



Falb, John wrote:
>Are there any current designs or thoughts on modifying the output of a 5v
>MAP sensor.
>
>1. Moving the output up or down by a fixed amount over the entire operating
>range.
>
>2. Change the gain of the output up or down.
>
>3. Not letting the output exceed 5v.
>
>An example of one is here but it costs 300 and 500 respectively.
>http://www.splitsec.com/products/arc1/arc1ds.htm
><http://www.splitsec.com/products/arc1/arc1ds.htm> 
>http://www.splitsec.com/products/arc2/arc2ds.htm
><http://www.splitsec.com/products/arc2/arc2ds.htm> á 
>If you have any ideas please share.
>
>John Falb

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