[Gmecm] Simulating the "power valve" in the ECU for PE

[Butler James-CJB006]

Some time ago I begin experimenting with the power enrichment function on my 1995 S10 to simulate the action of the ?power valve?.

 

I?m wondering if any others have tried the approach I?m about to describe.  It?s not something I?ve seen anyone write about, e.g., on Monodax.

 

Most (all?) carburetors enable PE when the manifold vacuum drops below a threshold (at least that how it works on my Edelbrock and the Holley ?power valve? appears to serve a similar function).  However, every GM ECU that I?ve seen (which is only about a dozen) enables PE based upon, at least, a table of TPS and RPM, and not MAP.  I assume other vendors? ECUs are similar.  I?m sure most of you know all of this.

 

I can see the rationale for not using MAP as a PE threshold in modern systems, and I?ll comment on that later.

 

In my case, I always liked the carburetor?s way of handling PE, i.e., when the engine approaches maximum load (e.g., 6? of vacuum or whatever one cares to define as ?maximum?), enter PE.

 

What I?ve done, in my S10 and some other vehicles since, is adjust the PE ?TPS threshold vs. RPM table? to enable PE at some target MAP, e.g., 26? or 28? of manifold pressure.  Of course, I had to have some idea of which TPS values to use for each RPM band in the table, so I simply logged a bunch of data from the ECU and sorted it to get an estimate of the throttle position/TPS values that would yield, approximately, a particular MAP for each RPM range in the table.

 

Upon applying these new TPS values to update the table, the drivability ?fun factor? was notably improved, which is why I?ve applied these changes to a number of my vehicles.  Configuring them for around 27? of MAP is usually to my liking.  I always validate the changes by logging across the RPM band and confirming that PE is entered at the target pressure.

 

In the real world a change like can cause at least one problem, i.e., when towing, or driving in hilly country, PE can be entered much more easily, and for long periods of time, with the typical consequences.  Apart from that downside, I find it?s a nice tweak.

 

Jim

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