digger

I got a big pile of Rotary Rocket mags from the early 80s when I bought my 84 se and am enjoying reading them.

There is an article in the March '85 issue describing RB's research with the 6port EFI 13b. They found a 5% HP increase at 7k RPM by advancing the timing 7.5 degrees from stock on both leading and trailing sides.

I am wondering about the long term effects of this "tweak". Has anybody been running advanced timing for a while and what was the negs or pos on the engine life?

NOTE: They specified in the article this was recomended ONLY for the 6port EFI 13b.

Felix Wankel

The only drawback I could see is maybe an increased risk of detonation?

RXcetera

Resulting in a dead motor. I like to keep my timing conservative... why risk damaging your engine for a few (if any) HP?

speckamp

7.5 degrees of advance over the stock settings shouldn't put your motor in any danger. The paul yaw specs call for I believe 10degrees of advance, but I've heard people break spark plugs because of that, but 5-7 degrees shouldn't be too much of a problem. (the yawpower article is here: http://personal.riverusers.com/~yawpower/pultime.html) If you do what his article suggests, I'd only caution you not to run the full amount of advance he says unless you're not faint of heart I plan on running 24/14degrees when I get around to poking at mine (2deg less than he suggests).

The n/a rotaries will safely run with MUCH LESS than the 87 octane, and we can't get much less than that (that's from felix miata's faq, which escapes me linkwise)

Have fun
--matt

RXcetera

That's the thing... if I had access to very low octane gas (-87) I'd experiment with very advanced timing, but all I've seen is damage resulting from stuff like what Yaw suggest. I'd use his settings on a fresh(er) racing engine... not a daily driver.

FJ

I have the same magazine and also bought my -SE in '84. From all I've read you will not have any problems advancing it 7.5 degrees. I wouldn't go as far as Yaw mentions, but I've read about better power, throttle response, etc with a little more advance. For no particular reason, I've always left mine stock. I'll have to try advancing it this summer to see.

-John.

speckamp

Why would you want to put lower octane gas in? That's SURE to blow your engine. Not to sound like a smarty pants, but octane rating is the fuel's resistance to pre-ignite in condtions that advancing the timing, increasing the compression ratio or adding boost cause. That's why the 3rd gens want 93+ octane and the 1st gens will run on a really strong whiskey

Anywho, 7.5 degree advance (maintaining the 10degree leading/trailing split) should be fine. If you're really worried, advance it only 5 degrees, or advance it all 7 and run higher octane gas.

best of luck,
--matt

---
rotorin like a bandit.

moremazda

iTrader: (4)

I have my 12a setup with Yaw's timing specs, run 87 octane and have zero problems. I have about 30,000 miles on the setup and about 175k on the motor and the thing runs just as strong as a new built 12a.

I know everyone is talking about the 6-port, but just this to put rest the reliability issues. I also get about 22 MPG with this ignition timing.

Ryan

FJ

Increased octane reduces advanced timing and boost induced detonation (for those so equipped), not reduced octane. What damage have you seen from advanced timing?

-John.

digger

This is all very interesting. I am well aware of what pre-ignition sounds like in a piston engine (that marbles in the cylinder sound, but as a recent rotor convert have no experience on what to listen for as a signal things are too advanced in the mazda engine (Prior to the sound of internals eating each other up).

Descriptions anyone?

RXcetera

Yeah... I realized I wrote that post up all wrong when I reread it this morning . It should, of course, be the other way around. The more the advance, the higher the Octane. Interestingly, in the old IMSA days, I read Jim Downing used to bring his own super low octane gas to the track because he prefered to set the car up with conservative timing. There remains two schools of thought on this subject. Some racers swear by the low octane, conservative timing idea, other insist advanced timing and more octane is better.

RXcetera

Check the above post for the correction on Octane levels relative to Timing. Things I've noticed from excessively advanced motors (mostly Yaw's settings): broken apex seals, broken trailing plugs, poor powerband and poor high rpm response. I've tried both, as am sure many here have, and in my opinion it felt great at first but as soon as I went back to stock, that felt just as good. I'm keeping it conservative .

peejay

The only time I was able to get my N/A to detonate was when I had the trailing set up to fire at 196degBTDC instead of 16degBTDC. Swapped the trailing plugs so they fired on the CORRECT rotor and all was well. If I didn't have the direct fire I would have noticed right away that I had the distributor in 90 degrees off.

"Gee, this thing is hard to crank!!" (Rrr.. Rrr.. Rrr.... >crack< Rrr >crack< Rrr BRAP brap brap brap brap... ) Hey I thought it was just 'cos it had really good compression

Rotaries have such low compression and high combusion turbulence that you don't need high octane. Advancing timing makes more power only up to a point, and then it starts hurting power because it fires TOO early. You only need as much octane as the engine needs to not detonate at ideal advance.

speckamp

as far as I've heard, detonation sounds the same as in a piston engine. There was a video where a 3rd gen detonated BAD on a dyno, and it sounded JUST like marbles in a glass bowl type thing.

--matt

---
pheer my 1.3

RXcetera

It sounds like "PING, PIP, PIP, PING, PING" lol.

peejay

in my case it was a loud chirping like a belt slipping only about 20 times louder, and every chirp made the whole car buck and it would puke black smoke from the exhaust. It did this under medium-heavy throttle at high load in a high gear - could floor it in 1st gear and it would rev right up! 2nd gear, rev up CHiRP CHIRP CHIRP CHIRP bucking and making no power. 3rd gear, couldn't go over 65 without CHIRP CHIRP and bucking. Must've detonated 50-100 times before I disconnected the trailing ignition so it'd run cleanly

RXcetera

Hey, you're right. I've also heard the chirping sound and my first thought was "is that the belts slipping?". It happened when I dropped the distributor off by the smallest margin. The car started up just fine, but I couldnt even hit the top of first gear... very bad.

The PINGing would happen on really hot days when I was trying to get the Dellorto dialed in. I would floor it in 3rd I'd get a distinct "PING" followed by a couple more "PING"s. Again... very bad.