Rx7carl

Octane isint the determinante factor of power in a gallon of gas. There must be a "theoretically" correct octane for an N/A rotary at it's stock compression. And I never subscribe to anything that cant be shown to be true. Just cause eveyone runs race gas in "all motor" class doesnt mean anything. I'm sure NSU Wankel and Mazda have studied this during the R&D work.

Scalliwag

While not subscribing to the normal train of thought on many things may be understandable. I would think that people have ran their NA's on pump gas and if it ran better they would not be paying $10 a gallon to run something that makes their car run slower.

88IntegraLS

The efficiency fault of the rotary engine seems to be not burning the fuel fast enough, as the air / fuel mixture will still be burning well after the rotor passes the point of maximum leverage on the eccentric shaft during the combustion cycle. If a quicker burning octane fuel could be used while avoiding preignition and detonation, its greater energy release per unit time could theoretically be set to occur right in the stage of maximum mechanical advantage on the E.C.

I would guess that retarded timing and / or water injection with some clever tuning could make a workable N/A rotary engine on 80 ocatane. Maybe even a tad more power could be extracted if one could harness the quicker burn properties w/o blowing up the motor

Good job on those housings Scalliwag, I would buy a pair if I could afford it

HWO

Because it combusts slower, you can run more advance, and thats what gives more HP

simply putting higher octane fuel into your car doesn't achieve jack if you dont tune for it

RICE RACING

yes rotaries are wierd compared to piston engines, you gotta remember that at around 7000rpm a piston engine only realy has say around 4m/s to burn the fuel before the exhaust valve opens, where as a rotary has 6m/s to do the same job (because of the gearing of the rotor relative to the crank) You have allot more time to do the same job, hence some of the timing you can use and the fuels that will or can be burned seem so far from the norm.

But I think allot of guys forget that you realy have a 1/3 more time available to do "work" combine that with allot of other factors such as spark configuration and different burn (heat release) rates of various compositions of fuels and you got a fair few variables to play with

Some "unconventional" methods can be exploited, such as low octane combined with less advanced spark lead combined with T&L firing together (which increases burn speed) and there are many options available for increased performance while still getting efficient combustion, what is the exact best method/combination ? There are many ways to skin a cat

nimrodTT

Given everything else is equal: running lower octane gas will give no benefit. It has been said already in this thread that octane rating is not a power rating. The octane rating also tells you nothing about the speed of the fuel's flame front. Octane only tells you its resistance to pre-ignition. Here is how it goes; I'll try to keep it short:

1. You need a higher energy fuel to make more power (all other things being equal). This higher energy fuel has the potential to burn stronger in the chamber of the engine, which can create more power.
2. You need a higher-octane fuel to run more timing advance without pre-ignition (all other things being equal). This additional timing advance can allow the fuel that is in the chamber to burn earlier and/or more completely. This also has the potential to make your engine more efficient and/or powerful.

The way I see it, you put the two together and you've got a pretty good combination.

Rx7carl

Thank you, you get what I'm saying. I'm talking about not using H2O inj however, and setting the timing to what the engine needs to make its best power. Basically REALLY tuning the ign for best power.

Rx7carl

WRONG!!!!!!!! more advance = more negative work in the engine. Higher octanes dictate more spark advance because they burn slower, so they need more time to burn, so you start the spark earlier. The downside of the early spark is that the start of the burn is too early and is actually trying to STOP the engine and reverse it! Especially in a rotary because of its narrow long combustion chamber we have a long burn which dictates a quick burning fuel to extract the maximum energy (i.e. burn it all) without having to advance the spark into the realm of negative work.

Scalliwag

There is a lot of very interesting thought here. Since our motors do use such a unique combustion process gasoline is probably not even the best fuel to use. What I mean by that is that with the optimum tuning and the optimum fuel to achieve the highest amount of horsepower there is probably a more desirable fuel or blend of fuel to achieve this. I just doubt that lower grade pump gas is the trick. The link refered to earlier that talks about how racing fuel is made may explain why all the "all motor" class rotaries run racing fuel. Maybe it is not the octane but the additives?
The biggest problem would be all the testing and tuning and blowing **** up trying to come up with this. To find advisors in this field would probably be a royal bitch.
But I think most of us are pretty used to knowing that we have to rely on ourselves much of the time.

A professionally built engine dyno, a lot of extra time, and good beer would be needed to really be able to get a project like this to work. You need something generating numbers in real time. You would also need a bullet proof motor. Probably some specially made one piece apex seals from a high strength stainless to hold up to as much abuse as possible.
If a temp sensor could be tapped into the rotor housing with a small tube going to the inner wall of the rotor housing you could at least stay a little ahead of failure.
My idea is that if you ran it tuned to pump gas so you could get an idea of where the temperature can safely be. At least that gives a starting point.
Otherwise you could find out what makes the most horsepower may just melt the motor at the end of the first pass.
I have never had first hand experience with an engine dyno so I don't know if there is a temperature sensor for the exhaust or not. If there is then the only place the sensors would come in handy would be running in your car. You could use the same setup I drew up for having a constant compression reading for testing my housing resurfacing mainly during breakin.
Here is an exaggerated view of what it would look like. You would change out the fitting with a sensor.
You would use a length of stainless brake line (because it is strong enough to withstand press fitting for sealing in the water jacket) Note that where the hole breaks the inner wall it is smaller than the tube.

I know this is a lot of jabber but if any of you guys are serious on trying to find an optimal fuel this may help you save motors in the process. This experiment could cost a lot of money before fruition is gained depending upon a lot of luck. Oh, and if you can stand behind a safety barrier during testing woukd be a big plus. Just in case you use a fuel that creates a rotary pipe bomb!

Scalliwag

Even at this stage of the game they would be $300 each to do them. If it works out and I get the spray equipment that price "should" come down though.
If you haven't visited the thread lately you may want to check out who offered to help test them

ASE_Joe

yes, most engine dynos are equiped with multiple EGT probes. At least all of the ones i have used have them. I havnt dynoed a rotary, ,but have done many piston engines. I have seen exhaust temps range from the low 500*Fs (very rich alcohol engine) all the way up past 1300*F. I dont think fuel had much to do with this though. Never experimented with just that. The mixture and timing seemed to be the contributing factor.

Scalliwag

Right. I doubt that very many people setup motors on dyno's for testing homemade fuel blends. Even less have tried it with rotaries probably.
But the biggest danger in this testing is going to be detonation and high combustion temperature.
The first numbers I would want to see and monitor when the motor started would be these temperatures though. Otherwise testing may be over before it even gets started. If they are little high make it richer and see if it plays out.

So has anybody dumped toluene in there tank after reading the link?

Rx7carl

Good points Scalliwag. I think the truth is that we really don't know, hell maybe even they dont know why they run that fuel except that it makes more power. I was just throwing out q's with some educated guesses. And thats why I was wondering if NSU or Mazda data on the subject was availible. Your right that it would be a MAJOR undertaking to try to solve this correctly. And prolly not worth it realistically.

88IntegraLS

If that surface you spray and machine on is as good as it sounds, $300 each is still a bargain. They are cheaper than stock and milled to the same tolerance, but with a surface with less friction and more resistance to wear.

It all comes down to my lack of funds! Same sad FC story

Scalliwag

Just be sure to tell all your friends not to throw away their galled housings! Hopefully at the end of the testing phase you will have $600 (plus the shipping) I can do a set for you
I may start buying galled and chrome flaked housings and some of you may be able to get sets done by trading in useable cores, or at least bring the cost down that way.

So if we want fuels that burn off quickly I would venture to guess that if we used something that burned off to quickly we could control that a lubricating material to help reduce the inherant friction on the internal components. That would seem to be a good trade-off to me. You slow the combustion process with a lubricant.

I always wanted to throw some graphite in a tank to see how and if that would work. My dufus *** theory would probably only work if you did not use a fuel filter.
Of course that is a really fugged up idea, but hear this out. The fuel would burn off and the graphite residue would penetrate all cavaties down to the smallest pore.
That SHOULD reduce a lot of friction and possible restore compression and possibly oil seal.
I never had a motor I disliked enout to try that on though.
When I get in my garage I think I will mix some in some gas and put a small amount in an open container and ignite it.
So be sure to watch the news just in case this goes bad! I would like to see what the graphite residue was like after the fuel burned off. If it became sticky or just burned off it would not be a good thing. If it kept it's original properties that would be promising.

My neighbors always like me to tell them when I am going to be experimenting so they can get their kids in the house! It ain't that bad but they do get puzzled looks on their faces sometimes when they see all the weird **** in my garage

nocab72

There have been a couple threads in the past months with some people sharing their "toluene" experiences.

K

Scalliwag

good bad or both?

protlewski

Hell scalliwag If I lived next door to you i would help you with those exps. I like seeing things blow up!

Scalliwag

Damn, if I lived in Key West I would be scuba diving so much I would not have any time for my wankel projects! Do you have any buddies with a dive boat?