I just read online that the recommended octane level for a NA RX7 is 87 and that anything higher is not recommended because it will result in HP loss, excessive carbon build-up and poorer mileage. Is this true?

http://www.aaroncake.net/rx-7/newowner.htm

 

Yes

 

yep...exactly true. Use the lowest octane you can get without getting any knocking

 

but for t2's you want to still use 93 or what ever your premium gases octane levels are...wish there was some sonocos down here

 

NO, not unless there are major modifications or additional boost.

For a stock motor (turbo or non turbo) you will only loose power using more than 87 octane.

 

uh sorry but i have large streetported 13bt running @ 10psi...should have included that..just going by what banzai-racing told me to do

 

yeah, and what was the guy asking?

So you thought you would just post, because you could... Despite that the information you posted was specific only to your set up?

Yeah, that helps people.

 

No, it's not exactly true. What is true is that the stock NA and TurboII FC RX-7 were designed for a minimum of 87 octane with a maximum of 10% ethanol. If the engine is in good, stock condition, then it will not need the higher octane fuel. Therefore, there is no reason to pay more money for higher octane if the car does not need it. Horsepower, carbon build-up, and gas mileage are not necessarily related to the octane rating. The octane rating is simply an anti-knock rating, nothing else.

No, for a t2 you want mineral water for fuel. Mine has a yuppie steam engine installed... wish there was some Perrier stations down here.

 

the previous owner of my t2 was older and he said he always ran premium in it for 15 years.. would it hurt anything for me to run lower octane? because as its stated in this thread its pointless for my to run high octane on my stock setup.

 

Higher octanes burn slower, and CLEANER..or else there would be no point to them..But your not supposed to put high octane in a rotary, think about it, stock timing with 91-94 octane? I mean rotaries have 3 power cycles per revolution, piston motors have 1 per 2 revolutions of the crankshaft. Think about it, a rotary should have to burn the fuel 3 times faster than a piston motor so it only make sense to put in a lower octane quicker burning fuel.

 

I actually tried putting 91 Octane in my car the other day. I did notice it felt sluggish at times. I thought I did something bad, but I realized after my next fill up with 89 that it was in fact the fuel.

 

Hmmm, I have been putting the "insert 1 slot higher th an 89 here" in my TII....maybe I should back it down. lol

 

Makes sense. Thanks for the input people.

 

Not true.


Actually, the rotary tends to have a colder combustion area, so it already slows the flame front down.

 

The number of "power cycles" is not the deciding variable when it comes to octane choice.

 

The higher the compression, the higher octane is needed. Jet engines have lots of compression; therefore, they use Jet A fuel (120-140). The Rotary doesn't have that high of a compression. Keep using 87. It is also much cheaper!

 

Over here in the Netherlands you can't get any lower the 95 octan at the gas-stations. Since I believe the engines are the same, wouldn't everybody over here have problems?

Riz.

 

so to those who premix thier fuel, do you still rock 87 ? when i first got my car earlier last month i was putting 91,, then decided to go 89....

Interesting thread here I did not know that rotarys require lower octane.

so think id be ok on 87?
ported turbo,
aftermarket top mount and fuel pump
boosting around 11-15psi at full throttle

Ever since i put a turbo motor in my 240sx and had my 190e 16 valve, ive gotten used to premium fuel.

 

No, because you use a different rating system for octane. its the same.

 

Octane = resistance to burning. Claims about the other wonderful things it supposedly does = fail. You need octane to prevent detonation (fuel igniting before the spark plugs fire), for example in a modified turbo. The NA RX-7 is factory tuned for extreme detonation protection even at 87 octane or a bit lower. So the lower the octane the better, as long as it's plenty high enough to stop detonation. Same applies to piston engines or any controlled ignition engine (i.e., not diesel). In other countries octane is rated differently, so it seems higher when it isn't.

 

It's unfortunate for the people living in states where they are now adding ethanol in the gas. I thought I read that E10 raises the octane level two points. I also heard that it could do seal damage to our engines, any truth to this?

 

If the engine is in bad shape or modified for higher boost levels, then higher octane would help stop any knocking that may exist with lower octane fuel. Please read here:
http://www.ftc.gov/bcp/edu/pubs/cons...tos/aut12.shtm

That is an urban legend, but don't feel bad, if I had $1 for everybody who thought this I would be able to retire, lol. I think it is a carry-over from the days when oil companies were allowed to lie about their products. Anyway, the point of higher octane is to reduce the chances of knocking, and that is it.

A 2-rotor engine has 2 power cycles per output shaft revolution, but this has absolutely nothing to do with octane whatsoever.

OK, you get one brownie point for being correct about jet engines generally having a higher compression ratio, and you get another brownie point just for relating the discussion to aviation. ....

However
1. You can't really compare an internal-combustion rotary engine with an external-combustion turbine engine with respect to octane ratings.
2. Jet A does not have an octane rating, but it would probably be around 15-25 octane if it did. Jet A is basically high-grade kerosene, similar to diesel fuel.
3. There is no 120-140 AVGAS that I am aware of. I think you mean 100/130 or 115/145, neither of which were designed for jet engines.

First of all, there is nothing wrong with using higher octane fuel in your engine other than the higher price. Secondly, as stated in earlier posts, the US has a different fuel rating system. See here for a general conversion:
http://www.btinternet.com/~madmole/R...RONMONPON.html

The FC RX-7 was designed for a maximum of 10% ethanol. E10 is 10% ethanol, so it will work just fine. The octane rating of E10 is as specified on the pump. For example, if the E10 gas pump has a "91" octane sticker, then it is 91 octane, simple as that.

 

lol sorry didnt read above post. *deleted*

 

i heard that people put 2 stoke oil in gas to help out is this true?

 

only thing it helps out with is premixing :P