spigot

iTrader: (4)

I'm looking for any web pages, or any other source that can explain how timing on the 3rd gen works, how it is setup, how porting changes it, how single turbos change it, and a whole bunch of other question I've forgotten to ask.

I've already found http://www.rotaryengineillustrated.com/
but there have to be more that cover the topic.

I'm soon going to need to tune my car and I need to figure out how this stuff works, I get the fuel maps and how to tune them, but how does the timing factor into the equation? Do I set the timing then tune for the correct AF ratios or is there some special technique to get the correct timing?

Is there a good way to tune the timing without blowing the engine (the equivilant of starting rich and taking fuel out of the fuel map)?

My setup will be
street port
3mm seals
XsT04e
HKS twin power
upgraded fuel system
power FC
and a whole lot of other stuff...

Thanks,
Matt

Jedon

You seem to be interchanging port timing and ignition timing.
Port timing is like a camshaft on a boinger, and determines when the fuel/air mixture enters the combustion chamber and when the exhaust exits. After you have the engine together you can't really change that, so to tune you are concerned with the ignition timing.
Playing with the timing seems to be the trickiest part of tuning and prone to killing your engine very easily.
I have read of people using ingition retard as a safety measure in overboost situations.
Sorry if I blabbed about stuff you already knew or got it wrong, I'm interested in any more info you find also.
-Jedon

spigot

iTrader: (4)

Yea one of the main questions is how does port timing effect the ignition timing? With a street port the chamber opens earlier and closes later, does this require that you fire the leading plug later and the trailing earlier as not to explode the mixture while the intake port is open?

Matt

RETed

You folks need to be able to use the correct terminology, or you're going to end up all confused.&nbsp Understand definitions for "duration", "overlap", etc. first.&nbsp Changing port timing does not affect ignition timing; ignition timing is referenced to the position of the rotors, so it really has nothing to do with port "timing".&nbsp Changing port "timing" affect intake/exhaust duration and overlap characteristics, but it does not affect ignition timing.&nbsp Don't comfuse the word "timing" to be describing an identical idea (well, technically they do - how's about that for more confusion)...



-Ted

spigot

iTrader: (4)

Ok let me make sure I understand some things first...

When I refer to ignition timing I'm refering to the degrees from TDC that the spark plug fires so +5 is five degreese after TDC.

Each face in the combusiton cycle gets 3 sparks, leading, trailing and waste. Waste is a byproduct of linking the coil outputs for the leaking plug. ( I chould be wrong but it usually goes off just after the exhaust port is opened.)

When I describe port timing I'm refering to the degree from TDC that the port opens and closes. For instance lets say the intake port opens at -40 and closes at -15 and the exhaust opens at 15 and closes at 39. Before u start yelling I know these numbers are off!! So in this case our intake duration would be 25 degrees and our exhaust 24. If we asume that there is no radical porting then there should be no overlap (in this example that would mean that the rotor face is less than 30 deg.)

Now the thing I'm trying to figure out is when do you fire the plugs? In the above example I'd guess you fire the leading plug just as the intake port closes and the trailing just as the exhaust is about to open?

So what happens if there is an overlap?

If I increase the duration of the intake port I'm going to have to retard timing as not to blow the mixture while the intake port is open correct?

To say that the port timing has nothing to do with when you fire your plugs makes no sense to me at all, If that were the case then bridge ports / street ports / stock ports would all run the same timing

Matt

RETed

Pretty good!

When rotor face is in it's ignition cycle, it cannot be in it's intake/exhaust cycle - it is another rotor face that is in a separate cycle.&nbsp This sounds like part of your confusion.&nbsp If the rotor face was in is ignition cycle and just happened to be in an intake or exhaust cycle, you'd either have an intake backfire or exhaust "backfire", respectively.

Everything is respective to TDC.

The BP and PP differing ignition timing recommendations take advantage of the increased duration of the intake port.&nbsp That's basically it.&nbsp For the most part, the ignition timing is still pretty close to stock (within 20&#176 or so?) - remember ignition timing degrees are 3x more than rotor position degrees, so 21&#176 of ignition timing difference is actually only 7&#176 of rotor position difference.



-Ted

spigot

iTrader: (4)

Ok few more ?'s

So lets say for example that we expand the intake port (such as a street port) by 1 deg... then we would need to retard the stock timing by 3 deg?

Don't any of the porting methods require you to fire while in either the intake or exhaust cycle? Or is that the barrier of how large a port could be (assuming u didn't have to worry about water passages and such)? No such thing as a 2 stroke rotary engine?

Now if we have ported the engine(2 deg) will the ideal spark point (point at which the most power can be made) be more than 6 deg retarded from the stock timing? I guess the question is what determines the best time to fire the plugs? Is there any real way to tune for it with /without a dyno? How much HP is avialable from tuning the ignintion maps or is it just right/wrong?

Thanks for the help... I prefer to know how something will work before I start playing with it, I'm sure some of the street port maps for the PFC will work fine, I'd just like to know why they work

Matt

RETed

Change in port timing doesn't necessarily require you to change your ignition timing.

Intake port timing usually increases duration.&nbsp Increased duration just allows more intake charge to enter the combustion chamber versus non-ported/stock intake port.&nbsp This is beneficial up to a certain point.

Exhaust porting increases duration of the exhaust cycle.&nbsp Earlier opening of the exhaust port allows the exhaust gases to exit earlier, but this hurts (low-end) torque, as the exhaust gases are not allowed to "work" on the eccentric shaft (i.e. "crankshaft"); this is why for low-end power, you want a later exhaust opening - this allows the expanding exhaust gases to transfer their potential energy more to turning the "crank".&nbsp There is a balance on a rotary turbo engine of do you let the gases out earlier so that it has more "power" to the turbo, or do you keep the exhaust gases in to get more power - this is a pretty tricky question, and all your experts out there do not have an agreement on this, well at least not in my experience.

Delaying port closing goes into increasing port duration and also increases overlap; overlap is defined by the time both the intake and exhaust ports are open.&nbsp Delaying exhaust port closing also helps the exhaust gases exit the combustion chamber, but you need to watch out for overlap.&nbsp Increasing overlap also increases the chances of a natural EGR effect which dilutes the clean intake charge with some of the exhaust gases left over from the exhaust cycle.&nbsp Now, you are going to have folks who are going to argue increased overlap is good for the engine - yes, at higher RPM's, but definitely no at low RPM's.&nbsp This is exactly what BP and PP engines do - run huge amounts of overlap and huge increases of intake port duration.

There are other intricacies such as intake pulsations, exhaust pulsations, and all kinds of weird phenomena that will take volumes of books to cover correctly.&nbsp I just wanted to cover just a very basic notion of what port timing is (versus ignition timing, well not really).&nbsp I'm sure we'll get some input from the other experts on here on this subject...



-Ted

VELCRO SHOES

****** ******!!!!!!!

I'M CONFUUUUUUUUUSED!

SPOautos

Hmm, this is all very interesting. We need to archive this thread.

One thing that strikes me a unusual is the overlap part where the exh and intake mix. Seems like that would be bad, kinda like sucking in 1600F air into the intake system. I know alot of people run those large overlaps with bp and pp engines but how is mixing 1600F exhaust in with you intake safe???

An i just crazy and not understanding this or something?

STEPHEN

SPOautos

double post...sorry

spigot

iTrader: (4)

Ok lets see if this is correct... When you describe overlap you are talking about one apex? Since the intake ports are on the side housings (non peripherial) the point of the rotor can be straddling the intake port which would lead to an overlap condition?

Also if this is the case then a peripherial port has the largest overlap condition since the apex seal doesn't block off that much area when swept over the port? If so then why is the renisis using a peripheral port design, wouldn't that be harder to control emmissions?

Matt

RETed

Technically, it's one rotor "face" rather than an apex.


Yes, the PP has the highest overlap.
Actually, the Renesis runs side ports for exhaust, which is kinda the opposite of what you're stating.&nbsp Side ports decreases overlap and decreases exhaust duration, which is better for low-end power and emissions.

Yeah, emission is something I didn't even touch in my previous post.&nbsp It gets really weird sometimes, but basically, the longer the combustion charge stays in the engine, the longer it burns.&nbsp The longer is burns, the cleaner the emissions.

The easiest way to think about port timing and ignition timing is with a piston engine, sorry to say.&nbsp The crank -> camshaft -> valves system controls intake and exhaust timing; this is similar to rotary engine port timing - the timing of the intake and exhaust (valves/ports) opening and closing.&nbsp The ignition timing is controlled by the distributor (old) or ignition triggers/ECU/ignitor (new) - the firing of the ignition spark that ignites the combustion chamber.


-Ted

jspecracer7

Wow this is a good thread! Keep it going guys...

spigot

iTrader: (4)

Ok some more random ?'s

Any truth to the rumor that the rear rotor intake ports flow upto 20% more efficiently than the fornt, which leads to a tendancy to blow the rear rotor first?
( We need someone with 2 widebands and more time on their hands than they know what to do with where's Jim)

You mentioned tuning for full burn within the chanber/ while the exhaust is opening to spool the turbos, is that the system the rally cars use to keep their turbos spooled? (does it kill the enigne or is it just anoying and that is why it isn't done on the street?)

btw thanks for answering all of these ?'s I'm sure quite a few of us have learned something

Matt

RETed

Wow, that's the first time I heard that theory on blowing the rear rotor.

I dunno about the FD, but the FC stock ECU fuel-cuts the rear rotors, theory #1.&nbsp The rear rotor doesn't get cooled as well as the front rotor, theory #2.&nbsp Fuel flow through the fuel rail hits the secondary rear fuel injectors last - any drop in fuel pressure will affect this fuel injector first, theory #3.


Yes, that "mis-fire" or "flat shift" system on rally cars does two things.&nbsp First, it spits a big load of fuel on the shift.&nbsp Second, it does a massive ignition timing retard.&nbsp Couple both together, and you end up burning fuel out the exhaust, which helps keep the turbo spooled.&nbsp This is done purely as a performance stand-point.&nbsp This burns valves (in a piston engine) and burns up turbine wheels in the turbo.&nbsp These rally cars sometime change turbos in between stages!&nbsp People try to do this on the street, but I don't recommend it unless you feel like swapping your turbine wheel (and shaft) out every few months.




-Ted

rxrotary2_7

good thread.

spigot

iTrader: (4)

Ok those work for stock engines, what about those with aftermarket ecu's and upgraded fuel systems? Granted that cooling is a big issue, so that alone could be the case.

What can be done to aid cooling to the actual block? I rember someone groving the water passages to increase the surface area but I never heard if it works. Any other ways that have been successful?

Just a random ?' since this has been beaten to death in another thread, what coolant are you running?

Also what do most engines die of that you have personally seen? Some common ones that I've seen are corner seals, and a couple spun bearings. But I still have yet to actually see an overheated engine (and I live in SoCal where it's warm) granted I've only seen 5 blown engines (and it had better stay that way for a while now )

Matt

spigot

iTrader: (4)

And here is a really random ? I've been playing with for a while... Is there any good/easy way to build a 610 cc single rotor engine? I'm guessing that taking out the second rotor shouldn't be too hard ( have to chop the ecentric shaft in 2) what else? But the big one is how do you get it down to 610 from 654 ( for a 3rd gen, I don't know if it was different for the others)? The one way I keep comming up with is to shave the sides of the rotor and then re cut the groves for the side seals, and shave some off the rotor housing. But that is alot of high accuracy machining that needs to be done, it would be easier to use a rotor with the sides filled in, but I don't know of a good way to do that, or even if it would bring it down enough to hit the 610 cc mark.

Anyway just something to daydream about

Matt

RETed

Ensuring proper fuel delivery will practically eliminate fuel starvation.&nbsp My parallel fuel rail conversion with an aftermarket FPR minimizes the chances of fuel injector starvation due to the stock/series fuel rail system.

http://fc3s-pro.com/TECH/MODS/FUEL/prail.jpg

Cooling is a totally 'nother issue...


Bulletproofing the cooling system itself would help tremendously; typical upgrades like larger radiators sure can't hurt.&nbsp Water jacket grooving typically only is done on the ignition and combustion areas of the rotor housing, so it does not directly address a "hotter block".&nbsp Efficient airflow around the engine should be addressed - make sure you have your engine floorpan still intact, as this keeps airflow going around the engine rather than immediately dive under the car.


I currently run Prestone anti-freeze.&nbsp I'm trying to locate a consistent source for that "Mercedes" type coolant, as this thread popped up on the big list.
http://www.imcool.com/articles/antif...-Glysantin.htm
http://216.78.172.244/cooling_system...coolingsys.htm
http://www.mbca.org/MBCA_Antifreeze.htm


Abuse would constitute bad timing/overly lean mixtures and overheating situations.&nbsp Detonation failures cause broken apex seals, corner seals (primarily) rotor housings, and rotors (indirectly).&nbsp Overheating would almost always damage the water jacket groove.&nbsp I've seen severe detonation "dent" rotors.&nbsp Spun bearings is not something I typically see, as lubrication problems almost always kill oil control o-rings first, which causes huge puffs of smoke through the exhaust; spun bearings are usually a sign of overrevving, in my book.



-Ted

RETed

The hardest part will be the eccentric shaft and counterweights design.&nbsp The introduction of "modular" eccentric shafts make designing and building them pretty easy right now.&nbsp Counterweight balancing is still a bit shouded in mystery right now...



-Ted

spigot

iTrader: (4)

Since it's hot in Vegas what oil weight and coolant/water ratio are u running?

Who is making modular eccentric shafts?

Matt

ULTIMATERX7

So lets say you already have a street port with a single turbo and or going to tune your car on the dyno. Do you set your timing at lets say 13 degrees adv., than tune your fuel? Or turn down your timing and adjust your fuel? Which is first?When lets say it runs strong up to 6500 or 7000 and it starts missing, is that timing or fuel or both? I not tring to confuse just trying to learn.
Gary
Wolf 4.0
XS T04S

RETed

I run Shell Rotella T oil in my FC right now.&nbsp It's a 15W40 dino oil.&nbsp I usually run 50/50 water/coolant.


I think Guru Motorsports in Aussie does?


-Ted

RETed

I always tune fuel first, cause fuel will always save your *** if run on the rich side.&nbsp Ignition tuning is a matter of having some kinda knock display (I do have a J&S) or a very good ear.&nbsp I would typically tune fuel first...then ignition...then go back to fuel to tweak a little with the new ignition timing maps.&nbsp This takes a whole lot of time and work to do; I typically tune on the street up to 80% then tune on the dyno if it needs to be refined more.


That's too general a problem - it could be numerous things "wrong".
*Spark plugs are too hot a range - check plugs, if possible, after a hard run to "read" AFR mixtures; try a set of colder plugs to see if it runs better.&nbsp Wide-band should peg rich under hesitation.
*Inconsistent spark - almost like above - try CDI box if spark is blowing out under lots of boost.
*Fuel problem - this is a matter of tuning and/or making sure your fuel system has enough capacity.&nbsp Wide-band should should lean.
*Fuel injector pulsewidths too high - anything above 90% is asking for trouble.&nbsp Wide-band should show lean.

It could be something weird like too hot an intake temp (insufficient IC cooling) or too much boost.

As you can see, there's a lot of things that can cause your problems.



-Ted