Hi Folks I have converted from point style ignition to electronic ignition on my 4 port 1975 13b

The 85 rx7 manual states the Leading should be set to 5 deg ATDC and Trailing to 20 deg ATDC. According to the manual the vacuum and mechanical advance will give me 18 deg Advance on leading and 25 degrees on trailing.

this sums up to

13 degree BTDC on Leading at 3000 RPM
5 degree BTDC on trailing at 3000 RPM

Is this correct ? why does the racing beat and all other sources online tell you to set the Leading to 12-15 degree BTDC ? Is this due to not connecting vacuum ? and what about the trailing ?

I am currently trying to get my stock 13b with original carb and exhaust to be street driveable and i would like to have the vacuum advance if it helps me in the transition from low to midrange rpm..

thanks in advance!

 

Can you post a picture of your REPU? Just curious to see it. I sold my old 1975 REPU and it ended up near the UK.

I should also mention the 1975 REPU factory manual is here. It also has a section for the dizzy/timing. https://www.foxed.ca/rx7manual/manua...76%20Small.pdf

 

https://oishiiimports.com/products/1975-mazda-repu

got mine from california

 

People have their own ways of setting the ignition timing. On my 74 13b EP I set at idle, vacuum disconnected, Leading = 0deg, Trailing =10deg ATDC

 

Do you have the point style ignition?

 

electronic, 85 Rx-7

 

0 deg L and 10 deg ATDC is what racing beat and recommends. Do you have the vacuum pods connected as well ? ( after setting the timing ) ?

due to fuel quality i think i need a bit more timing i guess. Im getting some funny sounds when adjusting timing closer to 0, maybe it has to do with the fuel quailty , i dont know

is the mark on the trailing vacuum bell in the center ?

 

Rotate the engine in its normal rotation (top of the pulley goes towards the driver side) until the first mark is lined up with the timing mark. You should see the second mark a little bit further back on the pulley.

Take the distributor cap, rotor, and metal shield off of the distributor and line up the leading pickup with the tooth on the reluctor. The leading pickup is the one attached to the vacuum can that isn't adjustable.

Now leading timing is set.

Rotate the engine further until the second mark lines up with the timing mark. The trailing pickup should be lined up with a reluctor tooth, now.

Personally, I like to use slightly more leading advance than base timing, and as much trailing advance as I can get from the distributor. This usually works out to 10 degrees of split.

While you are in there, make sure that the vacuum advance and the mechanical advance can move freely. The bearings for the breaker plates can get sticky and make the vacuum advance not work, or not return cleanly.

 

This is just a starting point and yes, I use the vac advance after adjustment. The later electronic dizzy has a slightly different advance curve then the points type. So, you may have to experiment till its right on your particular setup.

 

thanks for the input. I have set the timings earlier, based on the yellow TDC mark , Im running about 5 BTDC on L. both vacuum bells and the vacuum advances are working on L and T.

the trailing mark is red and at 15 deg ATDC, i will paint a new pink mark at 10 deg ATDC , loosen the screws on the trailing vacum bell, and push the bell inn to advance the trailing.

hopefully reducing the split will help the engine run smoother!!!

thanks again!

 

do you use manifold or ported vacuum for the distributor?

 

Ported is what the stock nikki provided. It has no vacuum at idle and only had vacuum when the primaries opened. You can use manifold, it will just make for a rougher idle but is still worth having it engaged. Really helps the initial tip in on an aftermarket carburetor. I did this with my Dellorto when I had it on my SA.