Right now my car has a cold air intake and mazdatrix true duals, and while driving it i can sortof feel my 6PI system coming on, but when vdi comes on it definately feels like that car gets slower and then gets much faster when VDI kicks in.

I was wondering if anyone has gone and tried to use variable rpm switches or anything else to fine tune when these systems come on and if so what was the resulting gains?

 

Setting up my 'vert I used RPM switches for switching vac valves for the VDI and aux ports.

VDI worked best at 5200 and aux ports at 3600 for me.

The cool thing about RPM switches, is that they switch regardless of load, so you can check operation in neutral (unlike the S5 ECU).

 

I'm guessing you did pulls with both off, only 6PI on, and with 6PI and VDI on and then set them to engage where the lines crossed? Or did you use a different method?

Also which rpm switches did you use, and how much did they cost? (and i would imagine that you just disconnect the ecu from the selnoids on the rack and connect the rpm switches to them, and rig them up to always have air pressure)

 

Originally I set them to the factory specs, then played up and down to see what worked best for me on the dyno. Most people I have talked too have been setting VDI at 5800, but that made a pretty big hole in my upper mid range.

I used some Summit switches to figure out what RPM (as they are adjustable in 100 RPM increments) but then built my own non adjustable ones.

On the wire up, I set them (the RPM switches) both up next to the ECU in the passengers kick panel. I cut the EGR wire from the ECU (since I no longer have a EGR valve) and used that same soleniod for the VDI. I replaced the S4 ACV with a S5 one that has the air output for the VDI and AUX ports.

The aux ports solenoid (a spare one from a motor I bought that came with a whole vac rack) was set up next to the boost/pressure sensor on the pass strut tower and wiring routed into the ECU area.

 

thats a neat way to do it

 

Do you think that there is a bit to be gained over stock (i know it wont increase peak but a smoother band is always better), or would my money be better spent elsewhere?

 

I personally think, unless you have done some mods that require you to rethink the activation that you generally are better sticking with the stock settings.

But if you have the dyno time and access, the money invested is pretty cheap (around $100, if you do it with the summit switches and used pre owned vac valves, but not including the dyno time) just to tinker you might get some slighty better settings.

 

If you have an S5 all you need is two rpm switches. Cut the wires running to the 6PI and VDI solenoids and wire the rpm switches up to them.

For each system, doing two dyno runs (one open, one closed) will give you two curves that cross each other. Where they cross is the activation point.