Highest Octane For Stock ECU??

ZzzZz

What's the highest Octane our stock ECU can effectively utilize? 91? 92? 93? 94?

Here in California, the highest is 91 but I've been able to try 93 and 94 as well.

I know there will be doubters but the 93 definitely had an impact on performance. The engine ran smoother, with that harse noise near redline every magazine describes becoming less clattery and more throaty. Throttle response was improved and so was MPG. Response going part-throttle was greatly improved.

The 94 made the engine seem lazy and out of breath. The engine is quieter going through the RPMs than the 91 but throttle response was bad and it seem to rev up slower.

Just yesterday I was low on gas and decided to finish off my 93. I drove spiritedly and made note of overall sound and feel. Once it was on empty, I filled up a tank of 91. Immediately I noticed a difference in engine sound in the mid to upper RPMs and throttle response.

Since this was just my perception I was looking to try and get others' experiences and try and align my butt-dyno with a real dyno (concrete #'s).

kdo2milger

i only put 93 in here...i would stay away from 91, its not much different than 89 honestly...

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ZzzZz

People here in Cali would shoot you over here if you dare compare 91 to 89!

Unfortunately, you can't get higher than 91 at gas stations here.

khtso

We can only buy 91 here in California, unfortunately.

ZzzZz

Race Gas Stations in SoCAl

Octane Blending Chart

ishthemienguy

yea..California suks! off topic a little bit but, have anyone tried to add the octane boost into any of your vehicle? not just the 370z but any car was just curious if the stuff works.

ZzzZz

I've tried it on others cars but didn't notice much. I heard that you have to put a lot of bottles in just to boost octane by a couple points and not what is directed on the label. I guess I just don't trust that it works.

the_student

Yeah, most of us Californians usually have 91 around. In San Jose, there is actually one station with 100 octane that you can mix with 91 and get around 95/96 octane.

JoeD

Yes, my friend's 76 station in Redwood City offers 100-octane unleaded at the pump, too. However, on practically any stock car, it will hurt performance rather than help.

It's only in the case where a car is dyno-tuned to run on a specific grade where there will be an improvement. Only then in the hands of a competent tuner will you reap the benefits of "more octane."

the_student

I assume that US versions of the 370Z were optimized for 93-octane. And since here in Cali we usually have 91, would you say if we are able to mix 100 and 91 octane to achieve a 93 octane level, that the cars will perform more to their peak performance? It would be a relative increase in performance from filling the tanks with 91...in theory.

JoeD

Doubtful.

The only production-car I can think of which was optimized for anything but 91 is the Veyron. Everything else is made to run on 91-octane, as California is the biggest car-market in the country.

Mix any octane of fuel you want in a 370Z...there will be no varience on a dyno greater than what there would have been even if you didn't change the gas from pull-to-pull.

ZzzZz

I doubt they'd cripple cars for just California's sake. Yes, the cars are all sold "50 state" emissions equipped, but I'd bet money that the ECU compensates for the lower 91 octane, thus making the minimum requirement, but can handle advancing timing when the octane's higher.

Even though its not exactly a US-Spec, here's an example of what could be going on for our 370s:

Stock UK Spec EVO VII (Vishnu Performance)
EVO VII dyno run 91 vs 93 octane - NASIOC


Or for US-Spec, look no further than the 350z!
350z 91 vs. 100 octane

rudi

In the manual for the Australian version, it states: Use UNLEADED PREMIUM gasoline with an octane rating of 98 (RON)

I have alway used BP Ultimate which is 98 RON in both my 370 and S15

Mercennarius

I'd venture to say you're wrong. Many cars are actually produced in two variants for the US...the federal spec and california spec. The ECUs are modified to run on Calis piss poor gas and stricter emission requirements. Sometimes cars are sold in every state BUT California(TT Supra etc.).

Though I will agree that running higher octane then is needed will net you zero gains...in fact often times it can hurt your overall performance. Optimally you want to run the lowest octane your engine can run on without detonating as this will give you the most power and mileage. As soon as your engine detects knock it pulls back timing/adds fuel to the map to run a more conservative and safer tune to prevent future detonation.

As for the original posters question, your ECU does not read octane levels it only sees what the O2 sensors and knock sensors tell it. You can run as high of octane as you want but it would be pointless to run anymore then you need and may do more harm then good. Just run 91-94 regular pump gas...anything less and you're engine will likely run a safer tune and anything more would be a waste on a stock car. I'd be more worried about the quality of the gas, stray away from older gas stations as they tend to have more sediments deposited in the bottom of their tanks that can get in your gas. The difference in brands is negligible.

Trips

Good Post... thats the bottom line, there is need to over octane a stock car unless it's highly modified only then will you see a difference.

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