Bold comments are me.

 

Yes indeed, those are certainly bold comments.

 

why would it be expanding if you ran the correct grade of gas. All S4 and S5 RX-7 models were designed to run on 87 octane.

Rob at pineapple and Dave Atkins both can back me on this. We talked about it last year at 7 stock and all agree about the issue. I can show you a half dozen rotors sitting in my garage, all with the widened seal groove, all from engines with known knocking or boosted issues and from S4 and up motors.

Again, the 9.7 compression rotors are fine to use 87 octane in a non boosted application. Its the 10.0:1 and above that I would not. Compression is just too great.

Of course pre-mix can also cause issues, as typically levels of pre-mix above 150:1 can lower the octane a point or two (depending on the quality and RON of the gas in the first place)>

And remember that S4-S6 knock sensors (and I am unsure about FE) all dropped knock sensor input in the stock ECU when there was WOT.

 

There're reasons that Toyota stay on the *top* of the choice for most ppl.

 

Let me guess, your thinking I may be loosing compression cause of this right? Wrong! Any heat pouring off the turbos will only bake the coolant seals on the NON compression side of the engine. I've personally assembled engines with scorched housings on the exhaust side of the engine and had great compression. Regardless, my coolant seals are fine. I properly cool my car down with light driving b4 shutdown. This basically makes my car NA and cools everything. I also run filtered/distilled water in my cooling system which is far less corrosive than tap water. Trust me I know I little something.



With my mileage your probably right but considering the fact that I do the water steam clean method, do you really think I would care about a few drops?

Nope! Not when someones been doing it much much longer than me. Also check out post number 33. This proves my point about 87 being more explosive and why my car starts better with 87 than 91.

http://www.rx7club.com/showthread.ph...ghlight=octane



I understand the effects of detonation perfectly in a rotary. I also understand how Mazda tuned the factory ecu and that my total compression ratio in my Fd is much higher than what people are getting in the Rx8 due to forced induction. The fact is with both engines having the same displacement, and my car making way more hp & torque, the internal pressures and stress levels in my Fd engine making 11psi boost (rougly 265hp with my mods) is alot higher than the NA Renesis period. There is no comparison but yet I can safely run 87 in my more over stressed engine. So why can't YOU comprehend that? 87 is safe in a stock Renesis. That's all I've been saying. Prove to me that 87 will cause detonation high enough that rotary's will blow apex seals in a COMPLETELY STOCK CAR with stock tuning. I have yet in all my years to hear of that happening.



Who's arguing? Yes it will compensate in some degree. It's harder for fuel to pre-ignite if you have to much dumped in. Ecu's can be tuned richer to compensate for a lack of octane. I told you before...this is why the fd has such a rich 10.1 A/F ratio under full load. Mazda knew not everyone would use their recommended fuel grade so they had to compensate for that lower grade by running richer. Even tuning experts know this. The Fd can even run up to 11.5 and be safe under boost at 10psi. There is plenty of margin there. Same goes for the NA Rx8. If you still don't believe me about the compensation, I'll get proof from a rotary tuning expert who has all the respect and trust if you want.

 

You claimed this expansion was due to not running the correct octane in the second gens. I responded with my own experience with my NA S5.


My experience doesn't include boosted 2nd gens. You never clarified about which models you were talking about b4 when making the expansion claims on the rotors. All that time I was clearly talking about NA S5 rotors.


.3 differance do you see your paranoya? See my above post about the internal pressures of my fd engine being far greater than the renesis. 87 is fine in stock NA Rx8.

 

Not gonna argue or even discuss this anymore. Do what you want. You don't understand, and fail to understand or read my posts and instead read what you want into them.

So I am not gonna post on this anymore. Figure it out yourself.

 

Bold.

 

It lives.

 

Figure what out? I understand plenty. I know for a fact that 87 is safe in the Rx8. That's what I'm trying to get some of you to understand.

 

There is nothing stupid about the fact that my original engine has lasted much longer than a huge percentage of other Fd owners. Any turbo charged engine that's being operated in a vacuum state is NA. As long as you are not on the throttle hard enough to spool the turbo's (which is exactly what a cool down is used 4) there's no reason for them to heat excessively. It's those people who stupidly shut down their engines after a hard run or think that idling is the best way to cool the car down. Hell that just generates even more heat cause now you don't have any air flow through your radiator or oil coolers. This is exactly why I think turbo timers are useless. Either way my coolant seals and my turbo's are fine cause I do a proper cool down that's beneficial in removing heat. Though my turbo's may still be hot cause of their close proxemity to the engine, they cool down faster cause I shut my engine down at a decent engine temp. Get it?


If you don't understand it's because your not reading the facts. That link and post number 33 proved my point about 87 having more heat engery. Did you not read it? Here's the quote for you:


Octane rating is the ratio of Octane to Heptane in gasoline, with higher octane gas having more octane (who would have guessed?) However:

Heat of Combustion for heptane: 44.752 MJ/kg
Heat of Combustion for octane: 44.427 MJ/kg

from the wiki: http://en.wikipedia.org/wiki/Heat_of_combustion

So the more Octane you have, the less energy you get when you burn it.

This chemistry lesson brought to you by the letter O.


Notice the highlighted red statement. Why do you think race fuel needs more spark to ignite fully? Same goes for E/ethanol. Lower octane gas gives you more energy but less knock protection. Higher octane gives you more knock protection but less heat energy. The extra heat energy of 87 is why my car starts better.

I don't need to provide mass results. I already explained to you how the stock tuning of the ecu allows for this.



You don't pay much attention to my post do you. Old quote form this thread:

Yes depending on your driving habits. If you run the engine as it was intended & and use the full rpm range all the time, then 91 octane is the best fuel choice. If you granny drive around all the time, it's better to run the lower octane. Rotary's knock mainly happens in the upper rpm ranges under load (6k and up). If your not driving your car to it's potential, then it's pointless to run the 91. That's all I'm saying. Think about this, why run a race fuel if your just cruising on the highway? You would actually have less power because race fuel takes more spark to burn. That's a fact.


I understand fully. Your the one that doesn't comprehend what I'm saying or pay attention to what I've already posted.

Again you just proved my point that you do not pay attention. When did I ever say anything about 87 was safe with mods on a STOCK tune? I SAID STOCK CAR WITH STOCK MODS. Geeez!


Uhhh I knew about that when the 8's were 1st held up at port (look at my registration date). So tell my something I don't already know. That extra fuel is why the 8 can safely run 87.

 

God Almighty Give It A Rest Already!

 

Hmmm, it really diminishes my point that it wouldn't retain the all-caps I tried to use.

 

I never knew we were talking about anything but stock tune? You said a few times that you knew how rich the stock tune was on your FD, so you knew your margin of error. I dunno, that implies to me that you were talking about a stock tuned FD . . . .

 

It lives...
(getting in on the fun)

 

All I was talking about was stock tuning on stock Fd's. Not stock tuning on Fd's that have mods. If that were the case then yes, it would be totally stupid to run 87 under those conditions. All Fd's are tuned excessively rich from the factory. Mine is no different than anyone elses. If you through in some modifications in then all bets are off and you quickly loss that margin. I can now see where some of the confusion was coming from. I'm not trying to be at odds with anyone here. Just trying to help and state some fact as I know it and clear up some well known paranoia with-in the rotary community. With your ownership experience, I thought you were completely aware of how rich all Fd's were tuned. So obviously were both at fault for assuming each others thoughts. That tuning is why I understand the margin of error. Same goes for the Rx8.

Peace!