Anyone Using VPC with DSMLink?

If anyone else is curious...here's the answer I got back directly from Thomas Dorris at DSMLink....
-------

Using a VPC with DSMLink shouldn't be any different from using a VPC
with a factory ECU. The VPC is supposed to output a signal that more
or
less replaces the factory MAF. However, you do need to keep a few
things in mind.

First, the VPC may be configured to produce a lower than factory
airflow
frequency in an attempt to compensate for injector size. Running a 660
VPC chip, for example, would reduce the airflow value to the ECU by
about 32%. If you also have DSMLink configured to reduce fuel by 32%,
you'll obviously have some issues. It has been suggested in the past
to
configure DSMLink to counter the VPC airflow signal by jacking the
airflow compensations up (in this case, you'd use +47%:

1 / (1 - 0.32) = 1.47

That way, the ECU would see a factory airflow and you could use DSMLink
to control fuel and timing like it's supposed to.

The other thing to keep in mind is the potential for the VPC to attempt
to work around airflow fuel cut. If you're running a 450 VPC chip,
this
limit can be quite low (14-16psi) and the VPC will produce a signal at
that point that's not at all what the ECU wants to see. So it's
actually probably best to run something like a 660 chip so that the
fuel
cut point is much higher and less likely to be seen in practice.

--
Thomas Dorris
ECMTuning, Inc.

atc250r said:

One more thing to keep in mind is the limit of the MAP sensor that the VPC uses. I was told by a few people that the MAP sensor maxes out at about 25psi and this appears to be true. After swapping my FMIC to a short route style one last week, the first time I made a 3rd gear pull the boost peaked at 1.96 bar according to the peak-hold on my turbo timer but the SAFC (which is wired into the MAP sensor) only saw 1.72 kg/cm2. When I had the boost set at about 1.7 bar according to the turbo timer the SAFC still saw the same 1.72 kg/cm2 from the MAP sensor which converts to about 24.5psi. Basically once you cross the 25 psi point you will have to add fuel in other ways (SAFC or adjustments within the DSMLink) so tuning it could get a bit tricky at that point.

John

Click to expand...

The VPC's MAP sensor limit is a problem. What happens is it just clamps the hz signal to the ECU. From that point on, the ECU isn't seeing an accurate airflow reading. Fortunately, the DSMlink does have a nice work-around built in. It's designed for small MAFs that are being overrun and works quite well with the VPC. It has a "fake MAF" setting. This will clamp the MAF signal and extrapolate a fuel curve based on the VE table. Unfortunately, this is dependant on the accuracy of the airflow reading at the clamp point, and with the VPC it doesn't seem to be very accurate.

There is also a feature called "Use MAP" that lets you tie in a MAP sensor for boost logging. When this is activated in conjunction with the Fake MAF setting, what happens is the DSMlink will clamp the MAF signal and begin to extrapolate it's data from the VE table AND the MAP sensor (in our case a GM 3 bar). I've found that this gives very consistent AFRs and makes tuning much easier.

NOTE: this MAP sensor does NOT replace the VPC's MAP sensor. The VPC functions exactly like it always has until the set clamp point.