So I've done the research on the octane issue for the N/A FC3S.

I've come to the conclusion that i should use 87 octane fuel. Due to the fact that 93 may leave lots of carbon buildup behind.

When I first got the car 3 weeks ago, i filled the tank with 93 octane, then I read the threads, and the next fill up was 87.

BUT, with 87 my idle seems a bit more erratic and i think i'm losing a few ponies.
On top of which the smell of gas is soo much stronger on 87 (I have an exhuast leak somewhere right by the headers)... the smell could it be the pulsation damper? How can I tell? or is it the exhuast, b/c i only smell gas when the car is idling and the car is NOT in motion?.

I've read if you're losing hp with 87 octane, then I might have some carbon buildup problem, and that i should go from 93, to 89, to 87 at Shell. What's the purpose of that?
Also, wouldn't the fact that i redline my car at least 3 times a day help break/loosen that carbon buildup, therefore allowing me to use 93 octane????

Thanks, sorry for the repetetiveness of my posts

Jahan

 

No, that's bogus. You car can use any octane grade of pump gas. The 87 grade is the minimum octane recommended, not the only octane recommended.

There are several possibilities for this:
1) Your engine is out of tune.
2) Your engine has deposits.
3) The 87 octane fuel you are using is of low quality or contaminated.

If you have tried 87 octane fuel from different gas stations, then you can eliminate #3.

An exhaust leak should smell like exhaust, not fuel. I would be very concerned about a pulsation damper problem. See here:
http://www.mazdatrix.com/c-pulsation.htm

The factory service manual shows where to find the pulsation damper to see if it is leaking.

To save money. It's basically a way to determine the minimum octane requirement for your engine, and it's not just for deposits, it's for any problem. In your case, I would try buying the 87 gas at a different gas station, first.

Also, all three grades of pump gas are very similar in their power rating, so you probably wouldn't be able to tell the difference if the engine is running OK and the gas is good. Sometimes the higher octane grades have slightly more power, although the lower octane grades usually have more power, but it all depends on how the manufacturer blends their gas.

Example for Chevron:
87 Octane = 18,500 btu/lb
89 Octane = 18,300 btu/lb
92 Octane = 18,400 btu/lb

There is a 0.5% difference in power between Chevron 87 and 92 - big whoop. It is interesting to note that 89 actually has the least power in this case. Other brands of gas may be different, of course. Regardless, the incredibly small amount of power difference isn't anything to lose sleep over.

Not really. That is more of a method to help keep the deposits from forming. It may shake some deposits out here and there, but that may be a bad thing if a big chunk decides to fall off and wedge in the mechanics of the engine.

 

^ Thanks so much, youre the man. But i've used different gas stations @ 87 octane and like I said the idle seems a bit rougher and when i meant i lose power i think what i really meant is the engine doesn't feel as smooth as I go up the tach.

Thanks again evil. SO do you think i can just stick to 93? And i'll check my pulsation dampener before i explode.

 

Yes, I would stick to 93. It would be good to try and find the problem, though.

I had a POS Camaro that had a computerized carb that of course screwed up, and in its fail-mode it only worked well on high octane. I just used high octane until I unloaded it on a piston-head who was willing to replace the computer.

LOL, yes, check the pulsation damper. It's not so much of an explosion problem, but rather it tends to start a fire after you park it. Sorry, I forgot to include this excellent link in my last post:
http://fc3spro.com/TECH/FAQ/pd.html

BTW, replacing the pulsation damper with a banjo bolt is a bad idea in my opinion, as that will put the pulsation strain on the fuel injectors, which are not cheap.