[B]Howard and Brian, what type spark plug are you using? I was studying Brian's comments about pre-ignition and found this about "Noble Metal Spark Plugs".

"your problem may be preignition. Of all the fuels commonly used, methanol has the lowest self-ignition temperature and so is the most pre- and post-ignition sensitive. Platinum or other noble metal electrode spark plugs are to be avoided because the catalytic behavior encourages self-ignition, particularly of methanol."

http://www.innovatemotorsports.com/f...ad.php?p=36062

I will remove my Platinum plugs before another tune. I guess the Iridium ones also.

Barry

 

Another example
http://en.wikipedia.org/wiki/Glow_plug
Glow plug filaments must be made of materials such as platinum and iridium that are resistant both to heat and to oxidation and reduction by the burning mixture. These particular materials also have the advantage of catalytic activity, due to the relative ease with which molecules absorbed on their surfaces can react with each other. This aids or even replaces electrical heating.
The burning of the fuel/air mixture in a glow-plug model engine, which requires methanol for the glow plug to work in the first place, and sometimes with the use of nitromethane for greater power output, occurs due to the catalytic reaction of the methanol vapor to the presence of the platinum in the filament, thus causing the ignition. This keeps the plug's filament glowing hot, and allows it to ignite the next charge.
Barry

 

Interesting view point.
The actual fact is that most of the race plugs used for both piston and rotary engines are made of both platinum and iridium. Pesonally I have found on certain applications the regular alloy plugs to be more prone to pre-ignition and detonation and vice versa for the plat/irid plugs on other applications. There are parties on both sides that will argue thie benefits of all the plug types out there. One sure thing is that they all have been proven to work. The same chemical benefits the materials offer for ignition to occur naturally could and do help in ignition especially under harsh and racing conditions where extreme combustion pressures exist where the regular plugs are prone to misfiring.
The thing is the auto ignition point of the materials used on the spark plug tip will take a back seat to what is needed to survive in the harsh enviroment a spark plug have to operate in especially in a rotary motor. With gasolene or methanol fueled motors all the pre-cautions to avoid auto ignition have to be took anyway no matter what type of plugs are used if it has to survive and live a healthy life.

 

Crispeed
I sent this pre-ignition question to NGK. They replied that they were unaware of any problems with methanol, but cautioned about using platinum with nitrous.

A side note, in NACA research paper #710 on pre-ignition. The catalytic effect of the platinum could be neutralized by using TEL (lead), the same way our newer catalytic converters can be ruined with leaded fuel.
Barry

Leaded race fuel could be providing this service behind the scene.

 

That's something every serious nitrous junkie is aware of.

 

"Of all the fuels commonly used, methanol has the lowest self-ignition temperature "

the above quote is VERY WRONG if it includes gasoline in the "all fuels commonly used."

one of the HUGE ADVANTAGES OF METHANOL is it's autoignition temperature compared to gasoline.... ALL gasoline, and that includes racegas.

autoignition temperature:

methanol 850-870 F

gasoline 475-495 F

this almost 400 degree positive margin over gasoline is VERY important to all w turbo'd rotary owners. we are on the edge as to autoignition due to a number of factors and alcohol is much more knock resistant than gasoline.

as to spark plugs... i listen to Jose LeDuc and he told me run nothing but NGK 6725 10.5s in my application.... expensive but cheap and they seem to last.

on a mid to low 400 rwhp application i would probably run something else.

howard coleman

 

[QUOTE=howard coleman;7022377
as to spark plugs... i listen to Jose LeDuc and he told me run nothing but NGK 6725 10.5s in my application.... expensive but cheap and they seem to last.
[/QUOTE]

The NGK 6725 series of plugs are platinums and I personally only run the 11.5's as I have found notting better to do the job. There is supposedly a newer version of this plug made by NGK for the rotary and it is in Iridium but it is not even listed here in the US. I've seen it in Europe and mainly Japan. Like as usual they get all the good stuff first and we have to wait.

 

Those are the NGK 7420 series of Iridium plugs for the rotary. Available in 9, 10, 10.5, and 11 heat ranges.

 

Crispeed and Howard, why wouldn't you run the trailing plugs a step colder? Don't we have a problem with poor cooling flow across the trailing pugs? It is the first plug uncovered exposing a possibility for pre-ignition (possibly glowing and at lower pressure).
Barry

 

wow, the like, first thing I EVER learned about turbo cars, was DO NOT USE PLATNIUM OR IRIDIUM PLUGS IN A TURBO CAR! for this reason.

I'm surprised it isn't common knowledge :P

I'm running 9EQ's on all 4 for now, we'll see if I have to go a step colder or not.