basic rotary tech question

okay i've been thinking about the rotary for a long time now, and i can't figure out how two things work exactly.

first, the spark plugs obviously have to be sunk back in a little nook so they can clear the apex seals when the rotor spins. well, if this is the case, doesn't that little nook allow some of the air/fuel mixture from one combustion chamber to flow backwards into the combustion chamber that is on its intake stroke? does anyone understand what i'm trying to say?

second, how do you change the compression ratio on a rotary. you can enlarge the divet in the rotor so you don't compress the air/fuel as much on the compression stroke, but then on the intake stroke you will be sucking in more air/fuel because of the larger divet, so your compression will be the same. can anyone clarify this?

sorry for the long, confusing post. it's hard to explain. i wouldn't be surprised if no one knows what the hell i am asking, but thanks anyway.

yea I'm not sure exactly what your saying, but these sites might help:
http://www.geocities.com/MotorCity/Garage/7365/docs/how.html
http://travel.howstuffworks.com/rotary-engine.htm
hope that answers your questions

yeah i've been to both those sites

i totally get what you are trying to say. ive been wondering the same thing myself, at least the first question anyway. just in case people still dont get what you are trying to say, i give you exhibit A:
http://files.automotiveforums.com/gallery/uploads/94979/seal_problems.jpg

as you can see, when the apex seal gets right in between the hole made for the spark plug, there is a space that would allow combusting gas to flow into the intake chamber. would this not prematurely combust the gasses in the intake chamer? how is this overcome?

although i am not positive on this, i dont think that compression can be adjusted, it is what it is. i think. can anyone confirm this?

first off is your second question. and you are correct. the deeper the the divet on the rotor face the lower the compression.. and on a certain level a lower compression rotor would suck in more air... but not enough to make a big difference. If you were to look at a 8.5: 1 compression rotor compared to a much higher 9.7:1 compression rotor you wouldn't really tell the difference unless you knew what exactly you where looking at/for.

I can take some pics if you guys really want to see the 2 side x side.

The answer to the other issue is reletively easy as well. both spark plugs do not fire at the same time.. the lower (leading) spark plug will fire first, then the upper (trailing) plug... the holes are different sizes.. the lower hole is about the same size as the end diameter of the sparkplug while the upper looks more like a pinhole...
the lower (leading) plug fires about at TDC, and the upper a few degrees later. the upper plug will burn off any residual air/fuel and eliminate chances of "kick-back" or "spit-back"

rotaries are great. you can pretend the gods of car making made this delicate car, and you can just drive it instead of wondering about it ;)

j/k

Or be one of those gods and make it even better!

shes had too many offers on these forums already haha

I like her avatar... bucky's great

Yeah Get Fuzzy is the best

first
The answer to the other issue is reletively easy as well. both spark plugs do not fire at the same time.. the lower (leading) spark plug will fire first, then the upper (trailing) plug... the holes are different sizes.. the lower hole is about the same size as the end diameter of the sparkplug while the upper looks more like a pinhole...
the lower (leading) plug fires about at TDC, and the upper a few degrees later. the upper plug will burn off any residual air/fuel and eliminate chances of "kick-back" or "spit-back"

Let me elaborate,

The leading fires at 5 degrees ATDC, then the trailing, at 20 Degrees ATDC. Then there is another spark event. The extra spark of the leading plug late in the exhaust stroke is called a "waste spark". Using a waste spark simplifies the ignition system as only one coil and ignition signal are required for both leading plugs.

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Get in line, buddy. :D

I love how one post is goodtech info, the next is some stupid comment, then tech info, then some more stupid crap... keeps everything inforing and interesting

boy am I glad 240sx's are the new "fad drift cars for homo ricers" and not RX-7's :P

Let me elaborate,

The leading fires at 5 degrees ATDC, then the trailing, at 20 Degrees ATDC. Then there is another spark event. The extra spark of the leading plug late in the exhaust stroke is called a "waste spark". Using a waste spark simplifies the ignition system as only one coil and ignition signal are required for both leading plugs.


so there are two leading plugs, making a total of three in the combustion chamber?

[QUOTE='92 S13]http://files.automotiveforums.com/gallery/uploads/94979/seal_problems.jpg
QUOTE]



how did you pause the howstuffworks.com animation and copy it here?

2 of both, 2 leading and 2 trailing, each rotor has one of each

im assuming he just hit printscreen at the right time. you cant pause a flash animation. hitting printscreen is just like copying text, except it copies everything on the screen, you can then paste it into paint or photoshop, whatever.

I was under the impression that there was one coil for both leadings, and a spereate coil for each trailing, therby having 3 coils.

I don't know about the coils... haven't found much info on them yet, I need a service manual or something lol

There are 4 coils total, split into 2 sets. 1 Set for trailing and 1 for leading. (2 each because 2 rotors). There are 2 plugs per chamber. The leading plug fires twice during combustion.

i totally get what you are trying to say. ive been wondering the same thing myself, at least the first question anyway. just in case people still dont get what you are trying to say, i give you exhibit A:
http://files.automotiveforums.com/gallery/uploads/94979/seal_problems.jpg

as you can see, when the apex seal gets right in between the hole made for the spark plug, there is a space that would allow combusting gas to flow into the intake chamber. would this not prematurely combust the gasses in the intake chamer? how is this overcome?

although i am not positive on this, i dont think that compression can be adjusted, it is what it is. i think. can anyone confirm this?
You can change the compression ratio in your motor but only by using different rotors. The rotors from 1st gen, 2nd gen, 3rd gen, turbo, and non-turbo cars are all different in compression ratios. Some shops will tell you to use one rotor for high revving naturally aspirated cars and another rotor for boosted high HP applications.

what are the physical differences between the rotors?

what are the physical differences between the rotors?

probably nothing that you could see yourself

One coil for leading...3 coils