Racing Beat PCM Flash: Would engine knock if using 87 octane?
 

Hello,

I am waiting for my PCM to be returned from Racing Beats. My car has a full tank of 87 octane gas. Originally the car run well with 87 octane and seem to get better mileage than using other grade. I wonder with the modified PCM, would the car still take 87? I plan to use 91 octane in the future but for now I am stuck with 87 octane until I empty the tank.

If you have racing beat PCM flash in your car, how do like the new flash? Any issue with the car after the new PCM is installed? How different does the car behave at higher rpm? My car has stock intake but with K&N filter, AP Pulley, Mazda speed flywheel and cork sport exhaust with stock cat. Car run well as is but I am curious about the new flash and want to give it a try.

Thanks.

Dunno... but bro... not totally being a dick but why would you run 87 octane when the manual and every bit of info on the car says use 93 octane? :scratchhe

Just put some octane booster in it for now and go easy, then change to 91 or 93 when tank is empty.

I would say take it easy. No hard acceleration until you can mix that 87 up with a half a tank of 93.

Yes, I was a dick using 87 octane in the car. The car runs better with 87 than 92 that I used to use and there were zero problem for the past 1 1/2 years that I own the car. I promise myself to always use 91 octane min from now on. I will do what your guy recommend. Thanks.

If I had my way, every car would be tuned to run on 87. The rotary has always loved low octane. Higher octane is not a better quality gas. We aren't talking about oil here. I've always run 87 and always will. I refuse to pay more for nothing. The RX-8 ecu is what holds this back and why higher octane is sometimes needed. Use the absolute lowest grade of gas you can without knock. The Racing Beat flash doesn't change anything in the cruise maps. only at full throttle at higher rpms so if you knock with 87 with the stock flash, nothing should change. I wish they'd have changed the flash to allow everyone to run on lower octane.

Thanks Rotary God. My car does not ping at all using 87 octane in the past. I can rev it to red line and it would run just fine. From what you said, I should be OK with 87 octane gas that I have, correct? Still, I would go up to 91 octane when I am done with this tank for the peace of mind.

What do you think about racing beat flash?

Here where I'm, we use 95, 98, 99 octane. You know what?? I feel better on 95... So RG is probably right , as usually... :)

Some people have issues with 87 and others don't If you don't, use it. Remember that the RX-8 ecu builds back in a couple of a percent in richness after it learns. The people that started using 87 octane don't sem to have any issues. It's the people that use higher octane and then try to go backwards that seem to have them. The ecu learns what you use and builds around it. When a company recommends a certain octane. They aren't doing it because less is necessarily bad for the engine. They say it for emissions reasons as that's probably what they used when they tested the engine. High octane is a conspiracy on street cars. We need one octane for all cars. I don't care which one. We just need to pick one of them.

Thanks Rotary God. I will get the PCM back sometime on Sat. What is your recommendation after I installed the PCM back in the car. Do I have to do the steering reset and the brake pump? Do I have to have like 100 miles of easy driving after the PCM has been reset? I just want to do it the right way. Thanks.

Just plug it back in and go. I guess you can do the whole brake pump steering wheel thing if you want to but I don't see why it would matter. If you question low octane, only get a couple of gallons and then see how it runs. Just remember that over several start and drive cycles, the ecu will build back in some tuning on it's own so an initial result may change over time.

My car likes 87 better. Correct me if I am wrong. The higher the octane, the more likely it will predetinate. A higher octane = higher flash point. I had to step down on my octane from premium gradually. Use the middle a couple of times before going down to the lowest octane. The RX8 is certified to run on E85. 87 should not pose a problem.

To me predetination is more of a concern than high octane pings. I think we can all agree that the ECU holds all the mysteries to this topic, and many others as well.

Lower octane detonates sooner. Octane rating is a resistance to ping. Tuning has everything to do with whether it will or won't ping too.

if your motor likes 87 octane better it probably lost some compression ....

I used to run on low octane 100% of the time . When I leaned out the mixture (similar to RB flash) under certain conditions I experienced bad knocking . Now I stick with premium .

I disagree with that.

we disagree on many things ...

A pump malfunction caused me to get about 7 gallons of 87 oct. a few weeks ago, It was obviously to me that the engine did not run as smooth, and I did get some knock at higher rpm. As soon as I burned through it and went back to 93 everything was back norm.

So basically you are saying that if an RX-8 doesn't detonate on 87 octane, it's got low compression? I will disagree with that any day as there is absolutely no truth to it. It "could" be in some circumstances but when we get into the world of "coulds" many things could happen without drawing any correlations. Some cars do run good on it and others don't. It doesn't mean those that do have low compression and those that don't have good compression. That's absolutely false.

http://auto.howstuffworks.com/question90.htm

Pretty good article. You were correct.

Were did you learn this? I've never seen anything about this.

I think every car has a variation of engine calibration. Some will tolerate the 87 octance better than others.

First, that's not what I said. :dunno:

IMO a proper RX-8 engine will generally not run it's "best" on 87 octane fuel. Further, I specifically used the term "possibly" because that response is based on several assumptions.

I recognize the preferred use of 87 octane gets debated here as much as insulating the frosty AC pipe :Eyecrazy: I'm not really interested in another long-winded theoretical debate that never seems to have any directly-applicable proof to bear it out. :rolleyes:

has to do with ambient temps too.
In FL this summer, before I started running FI I used the lowest octane fuels I could find. Car run better, was more responsive and I had no problems whatsoever.
Octane # is the amount of the additive that makes the fuel burn softer and slower. With higher octane you pretty much burn gas, that has less burnable gas in itself.

That changes things. I thought you were trying to draw a direct correlation between detonation and compression. If the RX-8 runs best on a higher octane on average, that's because it's tuned to do so. The engine would be equally happy with any other fuel with different tuning. If one person here can run 87 with no issues, his car doesn't necessarily have a compression issue.