TurboIIGuy

Okay so I keep hearing about guys pulling extra horsepower out of the timing they run on a rotary. Abel has stated that there is about 20 hp stuck in the timing on a turbo motor but what about a 12A.
Is there any advance curve or tuning adjustments that any one knows of?
post your links, thoughts, or tries.

Jeff20B

iTrader: (13)

Lots of 12A people run 24L 16T.

TurboIIGuy

I can't find my haynes manual or my factory repair book right now so I'll ask..............what is stock timing set at???????????
And also does anyone change the advance curve????????????
I know that on modded street rods guys usually setup the advance curde to advace early and alot.
For example, I saw a 1996 ford mustang GT with a holley carb conversion, that's right no fuel injection.
And it was set up to achieve, I think it was, 26 degrees of advance by 3800 RPM.
That's like 12 degrees more than stock. So is there anything I can do for a N/a 12A that is similar?????????
I also know that Mallory ignitions makes a distributor replacement for rotaries.......Anyone ever try it or is currently running it??????????????

TurboIIGuy

also is 24L and 16T at full advance or before vacuum advance???????????

Jeff20B

iTrader: (13)

With vacuum advance disconnected (and the rubber hoses plugged to prevent a vacuum leak), rev the engine to about 4k and locate your custom timing marks on your pulley with a timing light hooked to the leading circuit. Then rotate your dizzy housing untill the desired mark is achieved. Then with leading set, swap the timing light to the trailing circuit and push or pull the secondary vacuum diaphram assembly untill the trailing mark is where you want it in relation tot he little pin on the front cover.

If you haven't marked your pulley yet, remove it from the engine and mark it every 5mm (a cloth metric tape measure is perfect for this) up to 30mm. You see, the circumference of the stock main drive pulley is 360mm and therefore, 1mm = 1° (you can thank Mazda for that). When looking at the front of the pulley, you'll want to mark it in a clockwise direction (that's the direction for marking advance.

I think a stock 12A pulley is yellow L 0° and red T 20°. Starting at the yellow line, mark it every 5mm up to 30mm, and then add one more mark between the yellow and red marks to give you 10° after top dead center for setting trailing, or if you're wanting to keep things simple for the future, you could measure 8° and blacken the stock trailing mark.

I don't know if my post made any sense. I'm sure somebody else will be along shortly to recommend the Paul Yaw stretchy masking tape method. It's still good information as it can be applied to any size pulley, but it's up to you to decide if you want to go through the hassle (and risk mismarking due to any number of things).

joeracer

For anyone removing the front pulley for any reason, read the following first.

http://www.mazdatrix.com/faq/pulley.htm

TurboIIGuy

I read that before and am well aware of the damage possible, LoL

TurboIIGuy

that all made sense to me. I am looking at my main pulley, it has two markings, actually more like nicks in it, this is more or less where the timing is to be set, I know they are stock markings.
My question now is which marking means what????
if I look at my car from the front of the bumper facing the firewall there is a marking at about 12 o' clock and then at about 3 o' clock. Anyone know which marking is leading and which is trailing????
What degrees are these stock markings at???????????
is it yellow L 0° and red T 20° as Jeff20B said, if so which one is which since there is no paint left on these markings??????
Thanx for all the help guys, I am always learning something new.

Blake

There is no need to scare people over simply removing the pulley. The issue Mazdatrix is warning about only occurs if you remove the pulley hub, which requires loosening the big bolt in the center...something you will NOT do accidentally, as it is torqued to hundreds of foot pounds. Removing just the stamped pulley only requires loosening four 10mm bolts, torqued to about 7-10 ft lbs.

Blake

There are no stupid questions here, so I'm glad you asked. Just thinking through it logically will help. When you look at the engine from the front, which way does it turn? Well, the intake is at the top on the left, spark plugs in the middle on the right and the exhaust is at the bottom on the left, below the intake. So, the engine must turn clockwise, from your vantage point, correct? The Leading ignition fires first, even though the plugs are below the Trailing spark plugs. So, the Leading timing mark is first (farthest clockwise). The Leading ignition mark is at 0 degrees, which is Top Dead Center (TDC). And, the Trailing mark is at 20 degrees After Top Dead Center (ATDC; counterclockwise). These are the correct factory timing AT IDLE. If you rev the engine with the timing light attached, you would actually see those marks move counterclockwise until reaching "full advance" (the marks move counterclockwise as the spark happens sooner, to more advance positions on the pulley...as yet unmarked). There are two advance mechanisms: mechanical and vacuum. Mechanical uses weights at the ends of levers, held back by spring tension. Centripital force as the engine revs advances the ignition timing. The vacuum advance advances timing under low load situations only, for improved economy. You disable the vacuum advance, at least temporarily, to set the timing at "full mechanical advance", somewhere in the neighborhood of 4K RPM. All performance ignition tuning happens at full mechanical advance, as a baseline, since nothing else affects it. Setting ignition timing at idle is kind of like your employer specifying what time you need to leave for work, rather than when you should actually be there. That's fine if it takes everyone the exact amount of time to get there, but in the real world people live different distances and drive at differrent speeds. Same with ignition systems: Some people lock out the mechanical advance (I don't recommend it) and other change the advance "curve" by swapping springs or weights. Anyway, just remember that if someone says to set the Leading timing to, say, 24 BTDC (Before Tob Dead Center), that is NOT 24 degrees advanced from idle! The real difference is much, much less because the factory 0 TDC timing at idle changes significantly by full mechanical advance.

I hope that helps. If you have trouble visualizing it, check out my web site Rotary Engine Illustrated.

cpa7man

iTrader: (2)

Very good thread guys, Blake & Jeff thank's for the great insight.

Anyhing special for a street ported 12a, Race application?

TurboIIGuy

Great info Guys, thanx a whole bunch.
I'm glad we got some clear direct recomendations in this thread as opposed to a bunch of guys saying I think this will work or I heard that will work.
Great stuff here.
Thanx again. I understand the ignition timing the way it was explained by Blake perfectly I am rather mechanically inclined as does everyone around say so but there are always going to be things I need to learn more about. Just like these unprinted tricks, this isint the kind of stuff you'll read in a Haynes repair manual or a factroy repair manual..
Thanx again.

vipernicus42

iTrader: (4)

I've got a question then:

If you unhook your vac advance (and plug the vac lines of course) to remove the vacuum advance of the timing, can you just remove the springs from the mechanical advance?

Without the springs there, as soon as your car goes to idle the timing would go FULL advance, both vacuum and mechanical. Then you could set your timing without having to rev it up to 4k for the mechanical advance. That would make it easy for someone to set timing by themselves, without having someone else hold it at 4k. Then of course, once I had that timing set, I'd replace my springs and vac hoses to get my car back to "normal" cruising curve... Does this make sense? I mean will that work, or does unplugging the vac advance leave it at 0 advance rather than full? In that case, I'd be setting 16/24 and adding vac on top of that... :S I want to keep my vac and mech advance because I need it to be at least *semi* efficient on gas.

I remember Carl mentioning that removing the springs puts you at full advance when the car is running as an alternative to tack-welding your weights.

Question 2:
So I can't find more than one mark on my pulley, and it's the trailing.. I think... and the pulley is in BAD shape... so I can remove it just by taking the 4 bolts off and I don't have to worry about screwing anything up by doing it? I want to sand it, paint it, and put new marks on it.

Jon

joeracer

I was not attempting to scare anyone needlessly. I was simply putting a link to information that could prevent a fellow 12a owner from making a costly mistake that is easily avoided. There are a lot of people that put undersized pulleys on their car. Geez.

-chuck-

TurboIIGuy

ok to whome ever reads this next question please read the previous posts by Blake and jeff20b to understand my question.
Is the timing noted also okay for running a slighty retuned carb, actually an RX2 carb and a full Racing beat exhaust(single, not the street port one)?????????????
I wouldn't think timing needs to me adjusted to accomodate these rather minor upgrades but it never hurts to ask..................Thanx.....

credible_hulk

vipernicus42,

I am not sure about your first question, but you can take the pulley off with no problems. Just be sure to not mess with the huge bolt in the center, under the pulley. That's when things will go wrong.