guitarjunkie28

i'd like to see dynos of an rx8 with 87,91, and 100+ octane fuels, to see what the computer does with it.

neil

That would be a cool Dyno day project. I'd be willing to take part in that some time. My car is still stock in the intake and exhaust. No time in immediate future, but definatly open later. I'm in Seattle area, we have enough * owners we should be able to get a few together when the clubs out here arrange a day again..



neil

guitarjunkie28

i'd just be concerned with how long it would take the computer to adjust for the octane. if, in fact, it does.



i somehow doubt mazda would be willing to release the criteria for any possible octane learning mode in the computer.

neil

OK, I'm just a parts guy so take this with a grain of salt.. (Or like Mark Twain said "Better to remain Silent and thought a fool, than to speak up and remove all doubt.") But anyway...



There is a knock sensor on the car and my presumption is that it takes no time to learn anything as the computer is responding to the Sensor, along with the other feedback. I am sure the more tech types can take this further, but I expect any differances that can be measured will show ASAP. Older Rotaries actually can do quite nicely on 87 if tuned to it.



Higher Octane means a slower burn as most of you know. In Airplanes with such a huge bore and surface area, it is necessary to get a relatively even burn along with the 2 spark plugs. We do have a strange large surface area thus the leading and trailing plugs.



On my old RE5 Suzuki Rotary Motorcylcle, It had only one plug but was fired twice as I recall..



oops... the old fool has spoken..

neil

guitarjunkie28

i'm not sure how much power can be built with octane alone on these motors. they already run a LOT of timing to begin with.



leaner with less timing would build more power over richer/more timing.



but it's still something i'm curious about.

iceblue

Mine pings on 93 in hot days.



The ECU only pulls timing back a maximum of 5 degrees under detonation. So it does little to no good I can let it knock for as long as I want. Ive been pissed off and held the pedel down for over 5 miles with it detonating so much it couldent rev over 5 grand and slow as ****. Just because I hate my motor.



The FE is said to use higher octane because of the higher compression and advanced timing as stated.



Alot of times in the winter and if I get good gas I can run 87. Shity gas at pumps allot as each county has there own set of aditives they feel you should run.

j9fd3s

i was leafing thru the 93 rx7 service highlights book (it explains how each system works, plenty of neat graphs etc, there is a very detailed book for the rx8 too), and the fd book mentions that the ecu compensates for the octane of the fuel. it also says the knock sensor retards a maximum of 7 degrees.



i do not see how else it would know what octane is used, and 7 degrees doesnt seem like enough of a difference to compensate for the fuel AND have a saftey margin. i do know that the fd's are tuned so that the do run on 87 just fine.

guitarjunkie28

did you buy the book or are the service highlights (for the rx8) online yet?

j9fd3s

there are kinda 2. theres the yamaguchi rx8 book



and then theres a service highlights book, its like the fsm but explains the systems in detail, lots of graphs.

its available as a book. shoot me a pm, i'll get a part number and price, mazda turns the website off on the weekends

guitarjunkie28

oh i was just hoping to DL it for free



but i'll pay if i have to. i do enough with the rx8's now to make it worth it.