Anyone have trouble getting a good tach signal for rpm switch ?
 

Anyone have trouble getting a good tach signal for this type of rpm switch ?
I need this to adjust the WUR but the tach fluctuates to much
Thanks
Erick
http://www.summitracing.com/int/parts/sum-830450-1/overview/

I am using the same rpm switch and it works great. The resolution is to 50rpm I believe so it will bounce around a bit, 950 - 1000rpm.
I had no problem getting it to work with the rpm signal from the CDI box. Make sure you have a good ground for the switch and retry.
Good luck.

not to threadjack, but might someone explain how to use this switch w/ an adjustable WUR?

I've heard of it and think it's something I'd like to try...

thanks

You need a vacuum switch ,a rpm switch .this is how it works
You program the rpm switch to open the solinoid at a certain rpm. At that rpm it will let the vacuum reach WUR so it can richer the mixture
From stock the WUR ritchens way to early
Hope this helps
vacuum solenoid porsche 930 - Google Search

Your '87 came with two changeover valve switches mounted on the top left of the factory blow off/recirculation/diverter valve. You can use one of those with the summit racing rpm switch. Or buy a new one from pelican parts.

You hook up the WUR boost signal vacuum hose to one of the two hose nipples on the valve that are closed regularly but open and let air through when 12 volts is applied to the changeover valve. The other nipple that is only open to the other one when 12 volts clicks the internal solenoid goes to the bottom hose fitting on the WUR where the original hose went.

Wire ignition switched 12 volts to the changeover valve and the other terminal on it to the rpm switch. Follow the directions that come with the rpm switch for the wire colors and what they do and how to program the rpm into it. It's easy.

Then the RPM switch will open and ground the wire from the changeover valve at the rpm you programed into it and the valve will open so boost pressure will go to the WUR/CPR and lower control pressure making a richer AFR at the rpm you programed into the rpm switch.

I forgot to mention before the rpm switch is triggered by the skinny black with purple stripe wire that can be found on the back of the tachometer and in the 6 pin plug going to the ignition box on the rear relay panel.
hope that helps.

wow, I actually understood that (mostly!)... thanks as always Jim!

I'm putting it on my winter's slumber "to-do" list (ruh roh... just look @ what happened last time hahahahaha d'oh)

I used a bullet connector on this rpm signal wire to the Summit switch because you want to be able to remove the tach signal to the switch while its powered up in order to set the rpm when you want it to open. So you need to be able to cut the connection with some removable connector and then reconnect it.

Fred

I havn't needed to disconnect the tach trigger wire from it when I've programmed these rpm switches. I have two of them.
I just follow the directions that come with them and they work.

http://forums.pelicanparts.com/uploa...1406145242.jpg