Twilightoptics

iTrader: (1)

So I hit the dyno with my local car club this past weekend. Made 111HP and 107TQ

Up from 88HP/98TQ last year.

As per my last post, I rebuilt the carb, added a RB header with 2.5" exhaust to the dual pipe split, and took an SA intake and cleaned the casting flash in addition to aesthetic smoothing.

I don't know what my AFR was last year, this year it was a steady high 13.8:1 after a rich spike which I assume is the secondaries coming in. So are the secondaries coming in too late causing the richness?

Also, maybe one of you guys know what jet and or drill size needed to take the secondary jets down that full AFR point to get me in the high 12's?

This is a stock Pineapple rebuild with about 28,000 miles 1982 12A w/ Stock Nikki

Thanks guys!

dj55b

iTrader: (2)

Your AFR should be close to that, if you dip into the 12's you'll most likely loose power.

Kentetsu

Nice gains! If you are interested in doing some further tuning of the carb, get with Sterling and he will guide you on jet sizes, air bleeds, etc. www.sterlingmetalworks.com/bymc





.

t_g_farrell

iTrader: (1)

Now you need to breathe better. My stock port 12a with the mods in
my sig gets 134whp on a dyno jet.

You either need a sterling or mods to the nikki to get more flow.

Twilightoptics

iTrader: (1)

Hmm I know rotaries don't like pre-ignition... and typically best power/safety for that is made around 12.8:1 N/A.... you're saying it should be on the lean side?!


I don't know what muffler I have. I would like to finish the 2.5" exhaust. That's next on the agenda.

Sterling is the man. He's helped me before!

OneRotor

iTrader: (3)

Because the 12a has such a low compression ratio, you're going to have a very hard time achieving detonation if your AFR's are under 14.0.

I'm not sure about the power aspect of a 12.0 vs. 13.0 vs. 14.0 AFR when N/A, but you shouldn't worry about detonation unless you're running a huge ignition advance or a very lean AFR.

851stgen12a

Awesome #'s Paul!! Im curious to see how mine stacks up....
Im about to ditch my Holley setup, and switch to the delltoro setup...
When we gonna go racing??!

j9fd3s

iTrader: (3)

13.8 seems a little lean, depending on the carb/exhaust/ignition/etc it might make a little more power if it was a little richer... however it might not. ive found so far, that going from like 11.5 to 12.5 is a HUGE difference but going from 12.5 to 13.5 is really subtle.

Twilightoptics

iTrader: (1)

My experiances with piston engines showed significant gains richening from lean, not as much going leaner from the rich side of 12.8ish.



9.4:1 is still a decent compression. What kind of dynamic compression is assumed on a stockport? Is any of it bled off in the rotational cycle?

Still trying to learn the rotary thing. I guess the physics of burning fuel don't apply? Ignition system is stock, about 2º advanced from stock. Been toying with throwing an aftermarket Leading coil on though in that everquest of better milage.

Either way definitely an improvement from last year. The power stays up in the upper RPMs now too. I'll see about sending Sterling a message.

dj55b

iTrader: (2)

You can't quite tune a rotary engine like a piston engine. AFR are going to be different and so are EGT temps.

Oneiros

Hmm... If you're using stock jets, you can safely increase the primary fuel jets a bit, maybe out to 110 - 120.

j9fd3s

iTrader: (3)

with the rotary mazda usually has them setup really rich, so we make power by leaning them out.

piston engines seem to be the other way, again usually

both seem to make best power in the high 12, low 13 AFR's though...


on the rotary again, since we're usually leaning it out, its a little safer to leave it a little richer. so like if there is no difference between 12.8 and 13:1, i'll just leave it at 12.8.

IMO this gives you a little extra margin in case you get a bad tank of gas, or its really hot or something, we have crap fuel in CA