Let's say your timing is set zero at idle. At 4000rpms what would the leading timing be? 1st gen dizzy.. vac is not used just mech.
chuck

 

I think its 10 degrees mech. advance normally for both leading and trailing. Maybe someone can verify for an 83 13B as I know this is the case for an 80 12A.

 

according to may haynes manual, all 12a's have a max of 10 degrees mechanical advance(L&T), the book doesn't specify a difference in mechanical advance for the 13b's

 

If it's only 10degs, why does everyone lock these things when going turbo. I sure hope it's more then 10degs.
When I measure the movement of the rotor button, I get 11mm of movement. times this by two and get 22 total degrees of timing. Dizzy turns .5 for every time the shaft turns? correct?
chuck

 

people lock dizzys because you don't want a lot of advance w/ boost, idealy you actually want to retard timing based on boost pressure, other wise you run more chance of knocking/ predetonation

 

Remember in a manual, the degrees of advance is listed as DISTRIBUTOR degrees. This is because normally when you check/adjust the advance, you have the distributor in a distributor machine.

10 degrees at the distributor is 20 degrees at the engine.

And yes, there's 20 degrees of advance (at the engine) in a stock distributor. It's normally all-in at 4000rpm, if the unit is working as Mazda intended.

 

20deg + or - a few sounds right to me, I wanted to make sure I was right.
I'm useing a 1st gen dizzy on the 13b turbo pushing 1.5bar. I set my idle/base timing at -2deg at the crank pulley. I also marked the pulley in 5deg increments. one mm per degs of advance. At 4000 rpms my total timing is 19-20btdc. Looks like I'm going to advance the timing a few more degrees. EGTs are 675c at 1.5bar and 7500rpms.

Thanks
chuck

 

Note that it's not exactly 1mm/degree, and which pulley are you using?

I don't know about the FC stuff but the GSL-SE engine had the leading mark at 5 degrees (forget before or after) while the 12A stuff was at zero.

 

Its a FC turbo motor. so leading mark sould be -5. Is what I did was measure the distance from leading mark to trailing make. It's suppose to 15 deg differance. I used this measurement to add a few more advance marks on the pulley. I then set my idle timing at -2atdc. And if my timing light is correct, my timing at 4000rpms is 19-20def BTDC. Pushing allot of water to help cool combustion temps. At 20deg btdc at 1.5 bar my EGT is to low, I think anyways. 675c. I'm going to try running 22deg btdc at 1.7bar. ans see what teh EGT temps are.
thanks
chuck