Hi there,

I have a Series 3 1985 RX7. totally original. I am going probably add a sports exhaust and extractors mainly to save on fuel consumption.

My friend told me that I should find out if i need to add bigger carby jets. He thinks that adding a sports exhaust will cause my carby to "run lean".

This doesnt make sense to me. Can someone explain??

Rob

 

It's a good idea to go 1 size up on primaries and 2 sizes up on secondaries (I believe that's 95 and 170 respectively, but I could likely be wrong...)

I don't think it's a critical issue, but it's a good idea. Many people don't. Just don't advance your timing too much with a stock carb and full exhaust; your mixtures won't be ideal, and a bunch of us have had problems with that. Keep timing stock or around 2 degrees advanced and I think you should be fine.

 

I wouldn't touch the jetting unless you have an a/f meter or put the car on a dyno. For all you know the mixtures could be spot on and by upping the jets you'll just kill power and fuel economy.

 

Just to elaborate, the way I got the 1/2 sizes up is that I looked into this a while back when I had my Nikki w/ RB exhaust. The guys on mazspeed.com all seemed to recommend this jetting upsize, and I also called Mazdatrix. The guy I talked to at Mazdatrix said that for my setup, that was the jetting he recommended. I actually bought the jets from Mazdatrix, but never installed them since I got my Dellorto before I bothered with opening up my Nikki, plus my Nikki seemed to be performing quite well with the stock jetting.

From talking to others who have actually done this, I recall that people were saying the jets were a noticeable power increase. Whether or not this is true I don't know, but the general consensus seemed to be backing up this mod at the time I looked into it.