View Single Post
fredmeister fredmeister is offline
Smart quod bastardus
fredmeister's Avatar
Join Date: Oct 2002
Location: Baltimore, MD, USA
Posts: 2,232
Originally Posted by 911st View Post

I am not an expert but I am a bit concerned about what your guy did with the dual pot on your single pot dist.

A vac-retard pot is going to pull to retard. A dual pot pushes to retard.

If you put a push pot in place of a pull pot, hooked up to the boost retard connection you will get 'boost advance'.

You can work with Boost Retard, Vac-Advance, and or Vac-Retard. Not boost advance. You could get Vac advance by hooking to the other side of the pot. If you do that you would want to time it with the tube hooked up at 4000rpm. Also you need a connection at the TB that dose not show Vac at idle and it basically blocked (ported Vacuum).

You can check this with a hand pump at idle. Advance increases idle speed.

Can I get a ya or a na on this from someone else.
You are correct that the only way to tell what is happening with his exact unit the way it is hooked up to the throttle body is to temporarily disconnect the vacuum hose and install a hand vacuum pump and watch what happens to the idle timing as vacuum is applied. Document the maximum timing change at 10-12psi vacuum since this will be about the max your engine will pull.
Then apply a pressure of 14.5 psi to the same line and see what happens. This will simulate boost of 1bar.
This is the only way to know for sure what the pot contributes to timing change.
Then run the idle speed up to 4000rpm with the lines disconnected to see what portion the mach advance contributes..
Keep us posted on what you find out.
Irregardles of his results......what is consensus on a safe max timing advance at 1 bar boost? I am reading 18-20 degrees from the various posts on the forum past and present.
Am I right?
1979 930 Turbo....3.4L, 7.5to1 comp, SC cams, B&B intercooler, Snow Perf water/meth injection, Rarlyl8 headers, Garret GTX turbo, 36mm ported intakes, Innovate Auxbox/LM-1, custom Manually Adjustable wastegate housing (0.8-1.1bar),--running 0.7bar max
---"When you're racing it's life! Anything else either before or after, is just waiting"

Last edited by fredmeister; 04-01-2010 at 07:59 AM..
Old 04-01-2010, 07:55 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #59 (permalink)