a little bird told me that the fb runs best on 87 octane? any truth to this?

what's the best grade to run in an fb, and why? i'm used to putting in 92, so i'm probably going to need to be convinced... and no...money isn't an issue w/ my baby.

 

Yes it is true. It is one of the few things that is cheap on this car.

Vic

 

Most of what I've read is 87 octane is best for the N/A rotories, but use 92 if you have the T2 conversion.

 

Your N/A rotary would run on kerosene if your carbueretor was jetted correctly.

The engineers at John Deere put together a funky military engine years ago that would eat any fuel fuel you had and produce 300 hp regardless. The SCORE ( Stratified Charge Omnivorous Rotary Engine ) project if you want to track it down and see what rotary can do.

 

http://mrmazda.members.atlantic.net/...t.html#ROCTANE

 

The great part about the rotary is that it can run very easily on pratically anything that burns. Gasoline, ladies perfume, even cow **** can be ingested and make good power in a rotary.

 

Man, what'd I tell you, Cheap stuff... Donnie's Discount Gas.

Heres the skinny:

Higher octane gas takes more compression to detonate, therefore is used in HIGH compression engines and forced induction. But because of this, it also burns slower.

Lower octane will detonate in high compression, therefore ignites easier. It also burns faster.

Plus high octane fuels usually incorperate detergents, additives, and other crap. These things aren't tested for the rotary, because, hey. show me one damn thing that says, "Approved For Use In Rotary Engines!"... If you really want to add something, put in MMO and maybe carb cleaner.

I may have that switched about High octane burns slower and low octane burns faster. It might be the other way around.

 

SO how would race gas work in a rotary?? 108 octane. Would it be instant death, or actually pretty cool?

particularly on an -SE

 

Yes, the lower octane burns faster, and keeps the flame away from the apex seals and other sensitive stuff. Detonation is not an issue because of the high turbulence in the combustion zone. Theoretically the earlier combustion is also more favourable as it gives higher torque due to the position of the rotor.

 

What about octane boosters for those days at the track??

 

Well, just putting my 2 cents in....

In my 85 street port 12A, with stock comp rotors 9.6:1, I ran my best pass with 100 octane gas in it...not to say that lower octane doesnt do better, I just had that expirience..

Vuk

 

Was the best pass done after you switched to the higher octane on the same day as a pass w/87 octane gas? There's no way to know for sure that the octane change alone was responsible for the best pass, otherwise. A change in 10 percentage points in humidity can change an ET easily...

 

Hey, someone answer my question....


How would race gas work for an -SE? I happen to come across a bunch this past weekend, and wondering exactly how bad the idea of putting it in my car is...

TNX

 

It's not going to kill your engine or leave corrosive residue but it won't help either unless the ECU on your car has been retarding timing on your engine due to a knock sensor picking up a slight pinging from the gas you're running now. I'm not schooled on the sensor layout or complexity of the -SE ECU but that's how it works on boingers. With the race stuff, the ECU advances the timing to its map limits or the next knock threshold.

 

You only need to run as much octane as it takes to keep from pinging. Anything more is a waste.

So it depends on your timing, compression and boost(or lack there-of)

Octane Booster is crap btw, you might as well just shove the money dirrectly into the tank, because it will help just as much as octane booster.

 

Yuh Buckaroo's got it right....
Lower octane burns faster. That's why it's actually bad to run high octane fuel in a boinger designed for 87 octane. It actually damages the engine as it burns to fast. Same for race fuel. High octane is useless in an engine built for lower octane.

For Sevens, use 87, and it will do fine. My only pet peeve is that I refuse to use fuel that has alcohol in it. For years here in Ohio the only fuel not with alcohol in it was Marathon and Shell...A few months ago I noted that Marathon now has alcohol in it. That leaves only Shell, and that's what I burn, and only that. Alcohol will eat into any rubber connections between your fuel tank and engine. Where does that rubber/fuel go? Into your fuel filter, where the large chunks can be collected. The rest? Straight to your injectors or carb, and into your engine....Pretty neat, eh?

Denny, from the 'ol corncrib...

 

Can I upgrade my existing rubber hoses to alleviate that? I dunno who runs alcohol or not around here.

All the rubber on that car needs to go anyhow. Bushings, weather stripping, hoses, etc... All of it. Nasty and crumbly.

 

For regular street cars i believe that the problem with a too-high octane fuel is that the delayed burn increases exhaust temps, and leads to earlier cat failure.

 

Hiya, Slimdave...

Looks like you're a newbie...Welcome aboard. Neat to have another Ohio Seven guy in the 'ol forum. Where do yuh live in Ohio?

Denny, from the 'ol corncrib...

 

Pele,

Knowing that attendents always tell the truth, ask...He, he, he...
Seriously, contact the company, they have to tell you the truth, just act like you're all into cutting back on emissions. The other solution is to burn Shell. Here in Ohio the fuel companies are required by law to post a sign on the pumps advising of the alcohol content.

Denny, from the 'ol corncrib...

 

Hi Denny,

I just discovered this site (I'd wondered where all the RX7 people were), and I've been hanging out at mx6.com before this. I'm in Dayton, and I'm guessing that you're (wife is in air force, about to get out.)

 

Im from youngstown...wonderful Ohio!!!!!

 

To summarize and get it straight, an octane number is nothing more than a value which represents a fuel's ability to resist pre-ignition which is not the same as detonation. In a high compression boinger, the extra horseys=more heat. Any spot in that combustion chamber like a casting flash or sharp edge will not dissipate the heat rapidly enough becoming a glow plug just like your model plane's engine. Low octane fuel in this circumstance will ignite at that source AND at the spark plug when it fires. The two flame fronts will expand and they will collide at their leading edges. The two fronts colliding is the pinging you hear called detonation and the force is roughly equivalent to a sledgehammer on top of the piston. This shock cracks rings and breaks ring lands in boingers never mind the obligatory hole in the top of the piston that will result if ignored long enough. What detonation does or how it propagates in "high turbulence" of a rotary "window" combustion chamber is best left to the fluid dynamics guys out there.I think busted apex seals would probably be one result. POINT--> The high octane gas does not create more heat. That is a function of compression, timing and the port's ability to fill the chambers. More velocity=more fill=more fuel to burn=more heat=more horseys up to a point. High octane gas allows you to have only one ignition source light the fuel when you run the above equation in a high compression chamber to try to maximze your combustion efficiency. 'Nuff said---

 

Very nicely said, Mr. mar3. You obviously know your tech stuff. Thanx for the input, Buckaroo....

A slap on the back, and a tip of the 'ol Stetson to Newbies from Ohio, 95turbot66, and slimdave....I'm in Fargo, Ohio, which is just off I-71 at the Delaware exit...

Denny, from the abandoned corncrib...

 

Oh no, I didn't mean to imply that the higher temperature is derived from the calorific value of the fuel, just that the slower burn reduces the amount of thermal energy extracted from the combustion gases - on account of the piston having advanced further through the power stroke or a rotary equivalent - hence the higher temperature of the exhaust.

I could see the turbulence disrupting the wave front, but I'm not sure about the sort of gas velocities we're talking about here so I guess it's hard to judge how much the shock is dissipated.