chuck8313BTSDS

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

t_g_farrell

iTrader: (1)

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.

Sgt.Stinkfist

iTrader: (6)

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

chuck8313BTSDS

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

Sgt.Stinkfist

iTrader: (6)

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

peejay

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.

chuck8313BTSDS

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

peejay

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.

chuck8313BTSDS

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