Jeppy

im currently attending big bend community colledge in the avation mechanic department and i can get good deals on 100LL Avgas if all my catilitic converters have been removed to prevent clogging will there be any advantages/disadvantages to running this??? i know it will mess with oxygen sensors because of led deposits but those are cheep and does anyone know what the led will do to my rotors/apex seals???? help seal or will it just gunk evrything up??? the octane level is really high also im not running high compression its just a stocker so it really shouldnt do anything advantage wize... and can rotery motors have detination like a piston motor??? and i also would like to know what a stock 12A compression test should read....and wich plugs to i insert the tester the bottom 2????

flight_of_pain

if you are not running forced induction stick to the lowest octane you can get. there will be no appreciable benefit from avgas and iirc its not going to do your aged fuel lines any good either. rotaries can detonate but it is less common on N/a motors.

as long as your compression is within 5% or so of each other you are good (unless they are all 0 lol) typical numbers i believe are in the 90-120 range depending on how hard of a life the car had. run the tester in the bottom 2 plug holes, and hold the release valve if you using a standard type compression tester.

isaac

Rx-7Doctor

iTrader: (13)

Here is a link to a thread in the archives about compression testing

https://www.rx7club.com/1st-gen-archive-71/engine-compression-test-using-piston-engine-tester-597883/

Jeppy

THANK YOU!! do you know what the lead will do to the apex seals?? will it help seal things up because it does that somewhat in planes....well i think

vipernicus42

iTrader: (4)

Here's a thread in the archives (which appears in the FAQ) about what gas to use in Rx7s (has a nice post about what octane really does).

https://www.rx7club.com/1st-gen-archive-71/fuel-intake-what-kind-gas-do-you-use-yours-485219/

Jon

Jeppy

so really i would want to run the least octain i could for power as long as i didnt hear any detonation or pre ignition.... but i dont know where i can find anything sept regular.. i would like to try it..but F it i guess ill just use normal gas..with some 2 stroke mix and call it good... although the led is mixed in with the avgas to help lubricate and cool plane motors i think the apex seals would prolly like it. i wish i had a dyno near by i would try avgass and see what affects it had to HP

Ovid213

Octane burns cooler and more slowly than gasoline, so running higher octane than you need to prevent predetonation will generally LOSE you some power. I also severely doubt that lead is a good idea for our engines, because I could see it causing buildup on the seals. On older piston engines with very loose part tolerances, lead helped the rings to do their job- piston rings and apex seals, though similar, aren't exactly analogous.

Jeppy

makes sence 4 sure im convinced not to do it haha

trochoid

iTrader: (6)

Whoa guys, let's back up for a minute. Octane is a rating system. It does not burn unless you write the word on a piece of paper and light it, then it burns, lol.

Lead did 2 things in fuel, it was a cheap way to boost the octane rating and it had lubricating properties, mainly for the valve guide seals. Problem with lead was it also became a tailpipe emission and lead is toxic, particularly to infants and young children.

When Mazda was racing rotaries back in the day, they imported their own blend of low octane fuel to the track. The lower the octane, the faster, more explosive the burn, good for NA rotaries, bad for turboed ones.

DriveFast7

iTrader: (1)

Back when leaded fuel was available, people did run them in rotaries. The previous owner of my 81 knocked the fuel pipe restrictor out so they can put the bigger leaded fuel nozzle in there. A friend also ran leaded on his 79 13b bridgeport that would be classed in SOLO FP these days.

As for AVgas, I wouldn't be suprised if the rubber fuel lines and gas tank liner didn't like it. I wouldn't run it.

Jeppy

where can i get my own blend of low octain?????

kbeefy

theres no longer lead in 100LL

Box_Man

Yeah there is, just not as much. LL stands for "Low lead".

trochoid

iTrader: (6)

That's the million dollar question. I have yet to find a source for lower octane fuel. I suspect there may be some sort of additive to lower or dilute the octane rating, but I've never taken a course in chemistry.

FIBREMAZ

I'd generally agree that regular unleaded is best for standardish carbied n/a's but I run 98RON ULP with EFi. Higher octane fuels are generally of slightly better quality (in Austrlia at least) and also run cleaner than low RON fuels. The main benefit I see from using higher octane fuel is that you can crank a bit more aggressive timing with less risk of det happening.

BUMBLEBEE7

iTrader: (1)

100LL won't harm your engine. I use to be a Aircraft fueler and now aircraft mechanic. Turbo Recip aircraft uses 100LL. My12a SP had a taste of 100ll. The best thing to do is mix the 100LL with 94 or 96 octane. Trochoid/Kbeef you guys are sharp 100% correct. When I started Aircraft Maintenance I asssssume 100LL meant low lead. To use use 100LL you need SPARK to be able to burn it. If its burn properly than you end with lead. Piston aircraft uses similar plugs as rotary. Piston aircraft uses 100LL to minimize detonation. They are various type of fuels out there 80/85LL and 100/110LL all in different colors. The 100LL is the one widely use today its blue in color. For the guys not too familiar, 100LL is very volatile the vapor alone will set you on fire. Jeepy if you look in General and Powerplant book they talk a little bit about fuel and altitude/elevation.

Jeppy

Actually 100LL has more lead in it then any other AVgas the Avation world doesnt make much sence the way they do things..

mikewoodkozar

fibremaz, that is true, but i will be darned if gas prices are jacked here, so if i can get away with 87 im all for it

no_name

you will foul your plugs in like 4 hours. Don't do it.