Well...this question goes out to all the people who have tons of mods and still use the air pump. Well, even if you don't have an air pump...feel free to post.

First of all, my cars VDI is working, however with all my mods i've done to my car, there is no longer a sudden burst of power when it opens up. (Like there use to be before porting the lower intake, and going true duel exaust) So i was thinking....why not try to get it to open a little earlier? What i did today is take an extra VDI acutator i had laying around, open it up, and tinker with the spring rate. Well i realy did'nt tinker with it...i just compressed it a bit in a vice, then took a torch and lightly heated it up. Now, with the same pressure that would normaly make the spring compress to 1 5/8", it will compress to 1 3/8", after i heat treated it. I can't tell you how much less pressure will be needed to open up the VDI, but i'd think it would be less.

Has anyone else ever done anything like this? Just curious...

CJ

 

I thought the timing(for solenoid) is controlled by the CPU at 5200rpm? You might want to rig up a little pump and operate from inside the car for the time being.

 

I have found that that with a free flowing intake and exhaust(such as you or I have), the VDI actually kicks in later than on a stock engine. Before I put nylon inserts in place of the 6 port sleeves(same idea as pineapple sleeves, but without the sleeves), the powerband wa really defined. You could fell the spike right when you got into the VDI's powerband, and that spike was at 6K, not at 5200, which is the stock switching point. Now that I smoothed out the 6 ports, there isnt the defined spike, but the engine builds torque smoothly until 6K, where all hell starts breaking loose(along with the tires ). Seriously, I think the stock actuating point is about as good as it gets. If anything, its too low, do the flat spot on a heavily modded n/a will be right AFTER the switchover, not before.


BTW, I have mine wired, due to no air pump. I am working on an electric actuation using the stock signal.

 

Hows the dyno coming. when???

 

Maybe a month, dont know for sure. Have a few thing sto do before I dyno again, like redo my whole exhaust(if youre wonderinbg, its already sold when it does come off).

 

I had also toyed with creating a manually adjustable VDI switch-over point, similar to the VTEC contorl units.

Since I am not running (or won't be, as soon as the engine rebuild is complete) an air pump in my '90 N/A, I will first try this:

Use the back pressure air pipe from my RB presilencer as an air source to run to the VDI. Apparently, about 4psi of pressure, at a fairly high rpm, is created from that tube, but that remains to be seen.



Second and more complicated method:

This direction eliminates the air controlled charactistic of the VDI. I would remove the stock actuator, and replace it with an electronic solenoid. Something similar to the ones used for remote keyless entry or trunk release. Mount it in such a fashoin that the solenoid will actuate the stock VDI "arm."

To control the solenoid, I suppose you could use a simple RPM switch, but I wanted to kill two birds with one stone. Since I'll need to control my fuel anyway (3rd gen pump, TII secondary injectors), instead of using a regular Apex S-AFC, the idea is to use a V-AFC.

The bonus feature of the V-AFC is that it has an additional lead which normally hooks up to the VTEC soleniod at the Honda's ECU. For the RX-7, I would wire that VTEC lead into my door actuator soleniod. So based on user definable RPM setting, I could actuate my solenoid whenever I wanted to!!! Hence, controlling the VDI "switchover" point by RPM!!!

It seems too easy in theory, though...

Regards,
Shawn

 

Hey guys-

Where EXACTLY is the VDI actuator located? I have a 91' NA and have been working on getting my auxillary ports working, but am unsure about my VDI. I don't know if it's working, and I figured I'd check. I could probably find it if I looked around, but it would save me some time if you guys could at least point me in the right direction.

Thanks, Derek

 

On the drivers side, its the valve in the middle of the middle piece of the manifold. Just below the TB and intake plenum.

 

Thank you very much.

-Derek