i'll trade you my N/A for your turbo II

 

http://www.imoc.co.uk/technical/article/octane.htm#q31

Go there if you wanna know about Octane. Basically higher octain detonates at a lower pressure, sort of like its more explosive. Lower Octain gas actually has more energy than higher octane diesle even more. Basically on a NA Low Octane works better since stock ignition timing was designed for it. And there isn't a risk of detonation really. With a turbo motor I would stick with the higher octane it'll run better smoother and make more power. Some high compression piston motors like integra GSR b18s and RSX K20s will stumble and barely rev past 5 with anything lower than 93

 

instead of pressure, i would say compression. octane is a resistance to compression. likewise, i want to say that the compression affects it due to heat. so, unless i'm wrong, octane is a resistance to heat.
its like saying "tight briefs kill sperm count." tight briefs don't kill sperm, the extra heat that is likely to occur from wearing tight briefs will kill sperm. thats how i think of it anyways.
i dont know about the rpm increase (not counting boost). does higher rpm = more load on engine. too much load with too low octane i believe could cause knocking.

 

actually i believe the gsr required 92. i used 91 in west texas since thats all they had. it was during a road trip, so i never revved hard. i wouldnt worry much switching from 92 to 91, especially since gsr's don't have very high compression to begin with. 10.1:1 i believe.

 

Like I said, if you can get the boost down to stock levels, you will be fine if you don't abuse the **** out of the car.

 

i wouldnt go through the hassle of selling a car and buying a new one to save about two dollars everytime i fill up. seriously, what are the prices per gallon there? if you do buy another car, it better require 87 and get better gas mileage or else i would see it as a waste. i believe honda crx HFs got ~50 mpg. i may be a bit off, but i remember it was dang good.

 

If you can't afford it get a new car. Don't whine about having to do this and that and how its so expencive. You chose to buy an RX-7, you have to learn to live with it.

Just because the cost of entry is low, doesn't mean it is an inexpencive car to own.

 

Resistance to compression? We're not talking about H2O here

Of course it doesnt resist compression, because obviously the A/F mixture is compressed in the combustion chamber. Higher octane gas does not compress less, it can resist the ability to explode under compressed/heated conditions better than lower octane gas

I actually sound kinda smart.... if only in high school we had to do reports on the effects of low octane fuels in a rotary engine....

 

ive been rnning 87 in my car now and it is all stock except for jasma cat back and k&n filter.. am i going to f*ck up my motor too????? let me know soon. im on empty

 

there is so much bs in this thread.

87 is perfectly fine to run on a STOCK TII. If your car is functioning properly you can floor it all day and not ping once while using 87 octane. People saying that if you run 87 octane in a TII you will blow it are wrong. I have a TII with 121,000 miles on 87 octane to prove it.

Whether or not you can get away with 87 octane is not a question of whether your car is turbo or not. If your car is running stock boost then you are perfectly safe running 87 octane.

In this PARTICULAR INSTANCE I would recomend 91 octane. Why? Well since the original poster has an intake and exhaust I can only assume that he is no longer at stock boost levels. If you want to use 87 octane then put your stock exhaust and intake back on the car or port your wastegate like someone else mentioned.

I'm getting really sick of people telling me that my engine is going to blow because I run 87 octane in it. especially since the car has 121,000 on the original engine and still runs strong with good compression and no smoke.

 

a rotary engine is just another internal combustion engine.
it IS a resistance of a compression. water doesn't compress. there's a difference between not compressing and a resistance (from pre-igniting) due to compression.
"The octane rating of gasoline tells you how much the fuel can be compressed before it spontaneously ignites. When gas ignites by compression rather than because of the spark from the spark plug, it causes knocking in the engine. Knocking can damage an engine, so it is not something you want to have happening. Lower-octane gas (like "regular" 87-octane gasoline) can handle the least amount of compression before igniting."

 

Agreed

NO type of air can RESIST compression by a 10Ib rotor and a metal housing squishing it together. Its not like the 87 gas will compress more than 91 gas. Regardless, the air and fuel mixture is the same and it will compress the same. Its not going to fight back against the rotor and the housing

Now as far as how much the fuel can RESIST the heat put upon it before spontaniously igniting is a different story.... resisting compression is not an issue.

I get an A!

 

what are you talking about "no type of air"? where did that come from? i've been saying the same thing all along. octane is the measurement of resistance from compression. the quote above is from howstuffworks.com. i dont mean resist as in 'push against,' i mean resist as in how much compression it can take before it ignites.
87octane can be compressed less than 91octane before it pre-ignites.

 

LOL i think we both understand the concept well, its just an indifference on how to describe it through words.

Friends?

 

I've actually found pretty decent gas milage up to 3800RPM.

Also, drive with the throttle in such a position that you're always in closed loop mode. (dont push it in so far that your vac drops below 5-7hg)

 

Bad idea...I wouldn't drive even a stock TII hard without high octane fuel. You're assuming 87 is ok for a perfectly stock car in perfect condition. It is likely that most high mileage motors are NOT in perfect shape with perfect compression. Most high mileage motors probably have some carbon buildup which causes hot spots and makes the act of detonation easier. High octane is really just cheap insurance...

If you can't afford another $5 a tank, you shouldn't be driving OR you should get another job

 

Everything you said is basically wrong. Why do you think Mazda recommends high octane in the manual that comes with the car? Maybe your turbo isn't spooling correctly, or you don't make 7500 RPM shifts.

-Joe

 

The knock box is probably helping things out running 87 but it's just not a good idea.

 

whoops, i got my numbers screwed up - last time I filled with 91, not 87 - lol

still - minimal boosting for me

 

why do you think Mazda recomends putting 87 octane in my car? Read the S4 TII factory manual. You are wrong.

and redline is 7,000 not 7,500...

 

He's right 87 octane on a STOCK T2 is just fine--per the owners manual. BTW, older used engines will develop lower compression so less risk of detonation.

Yea for this guys modified 88 with higher boost you should get higher octane.

 

When I was making myself broke on $2.65 a gallon 92 octane gas I often has this very same thought. I know the downsides, and the savings really aren't worth it.

Let's say you need 16 gallons of $2.65 gas, that makes for $42.50 worth of gas.

Now lets say that the low grade, 87 octane was less, it's usually about $.20 less a gallon. Now that means that it is 16 gallons of $2.45 gas. That makes about $39.20.

The difference there is only around $3. When you are spending almost $40 for a tank of gas, what's another $3 to make sure your engine is safer?

And really, a lot of you have cheaper gas around you than I do, so the difference would be even less. Please do everyone on here and yourself a favor and use premium gas.

 

using high octane gas in a stock TII will decrease performance. Why don't people understand this...

 

Because people always just say stuff like this and never explain why

 

Its so TRUE!!!