Highest Octane For Stock ECU??
 

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).

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

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.

We can only buy 91 here in California, unfortunately.

Race Gas Stations in SoCAl

Octane Blending Chart

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.

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.

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.

No wonder I couldn't find anything above 91 here in Los Angeles.

Highest performance will be achieved on the lowest octane fuel possible without knock. If you run 87-octane and the engine does not knock/ping, then it will run better than if you had filled 91+.

Yes, there is such a thing as too much octane, and no..."octane-boosters" you buy in a bottle from Auto Zone do absolutely nothing.

That said, I have a hard time believing one can feel a difference with 91 vs. 92/93/94-octane on a stock car.

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."

iiunno what the dealership put in the car but for my first fill up i put 94 in...there are only a few gas stations here in edmonton that sells 94. I didnt notice any difference.

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.

True.

You have to remember that, with modern cars, the ECU will dial back timing to prevent knock/ping. If you put 87, it will dial timing back and reduce performance but it will be fine. On the flip side, if you put 91, it will advance timing to give greater performance.

Now the unknown is: what octane is necessary for the ECU to advance timing to the MAX? Timing from manufactures might be designed around 91-gas as a requirement but is it really "optimized"? Is their untapped potential?

Silly analogy but it's kind of like how you can overclock CPUs to realize performance gains over stock by simply advancing the timing. The CPU is marketed and rated at 3.0GHz but it can go higher.

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.

Given proper conditions absent the externalities that would otherwise cause the ECU to pull timing (excessive heat and/or very high load), that figure can even be lower than 91-octane. However, in real-world conditions, my guess is that it's right around there where timing will not be advanced further.

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

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

:iagree:
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.

http://images50.fotki.com/v1557/phot...youlose-vi.gif

Seems a lot of people believe high octane = higher power.

It's been covered here and NUMEROUS places on the web that this is not the case, yet the myth still prevails.

Hmm...I should email mythbusters.

I've never ran anything under 94 octane in my life...
I love my cars so I'm gunna feed it with real food

I agree with some of the above statements. The only times I saw tat race gas helped was when the cars were modified. My s2000 loved 112 octane :D it would eat it up. I also had close to 10K worth of work done in the power department. You will know that you are gaining power when it takes the engine less time to hit redline! I ran 112 for about 2 months till I destroyed a racing test pipe from T1r... thats right I destroyed it! :tup: S2000's are known for hot exhausts but with the racing gas I cracked and disintegrated all of the welds in the test pipe it literally fell apart. I have it as a trophy in my shop and had T1r send me a brand new one saying it just fell apart one day.

But any way like others are saying if your car is not tuned to use high octane you will loose throttle response and power. I had an emanage ultimate that allowed me to adjust everything for my fuel and performance parts and I saw a good 17hp increase by going to 112 octane. Be safe with your fuel the stuff can get dangerous for you and your engine. I have 10 gallons of experimental race gas thats close to 120 octane and if you get it on you it evaporates instantaneously... some pretty cool sh1t!

YouTube - XXX Race Gas gains 14whp on stock 370z

Wow, look at how much leaner it ran with the race gas. I wonder if that is due to the way the gas is burned or if it is the ECU's doing.

At least part of it is due to the oxygenation of the gas. How much of the gain is due to oxygenation vs. high octane and/or ECU adjustment is impossible to say from this test alone. But I think it's enough to at least cast doubt on many of the positions that have been taken on this thread thus far (like the position that race fuel won't produce any gains on this car unless it's highly modified or tuned to use race fuel, for example).

Here's the original discussion thread:
http://www.the370z.com/nissan-370z-g...tock-370z.html

That's the whole problem right there.

Higher octane gas isn't better for your car...

I had some flanges welded to my S's test pipe so I could wrap it in the stock cat heat shields... it lasted about 6 months before I started hearing this ringing noise. Took me another 6 months before I tracked it down to the test pipe. when I took it off, two of the four brackets had ripped holes in the tube wall. Looks like the heat was just so bad it affected the stainless surrounding the welds. Pity.

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.

The gains were made because of the oxygenated fuel, not because of the octane difference. Oxygenated fuels have a lower power stoichiometric and thus you have to run a richer AFR mixture then non oxygenated fuels to compensate. While oxygenated fuels will reduce gas mileage they are able to produce more energy during the combustion process.

Whatever, forgive me if I don't take your word for it. In any case, this still disproves the claim that race gas produces gains only if cars are modified.

Its not the octane that makes the difference though. You only need high enough octane to resist preignition, anymore can't help you.

Then why with the oxygenated fuel does the car run a lot leaner?

And how do you know this definitively? How can you be 100% certain that higher octane didn't account for at least some of that 14whp gain? Understand, I'm not saying you're wrong. What I'm saying is that I don't know for sure one way or the other, because I have yet to see any proof. I just see a bunch of people making claims, but I see no tests to verify one way or another. What I'd like to see is a video similar to the one IP did, showing someone dumping in non-oxygenated 100-octane fuel in. If the dyno reads 0 gain, then I'll be convinced that higher octane doesn't do anything, because that's actual evidence/proof. Let me put it this way. I wouldn't accept someone's claims that mod xyz produces huge gains without seeing proof in the form of dyno results. I doubt many of us would, right? So likewise, I'm not going to accept anyone's claim that xyz produces zero gains without the same kind of proof. As far as I'm concerned, until there is proof one way or the other, the question hasn't been definitively answered and all positions are conjectural. Also, just to be clear, I did not post that video with the intent of offering it as proof that higher octane produces gains. We obviously can't say that because the fuel they used was oxygenated. My intent was only to refute the claim that race fuel in general will produce no gains in the 370Z unless the car is modified for it.

That's the question though, where is the sweet spot between 91-94? Why pump 94 when you can save money with 91 right?

Was never suggesting 100octane+ is beneficial for a stock 370z.

Oxygenated fuels increase the burn rate. It's like adding a (weak) supercharger, and because the ECU is reading off the Air Flow Sensor on what's coming in, and is reading the o2 levels going out, I'm sure it's trying to enrichen the A/F ratio, which would in turn add more fuel and oxy-fuel, making the problem "worse" - I'm sure after a certain point the ECU wouldn't know what do to and just use it's default (rich) map to protect the engine...it's basically as if the fuel injectors are shooting in pure o2 out of a tank into the chamber, in a sense.

You get the same result by using nitro-methane...though, don't go buying R/C gas and sticking it in your Z.

I don't think members on this site believe on an absolute level that high octane always equals higher power. It's not always the case.

But when your talking in terms of going from 87 to 93 for your 370z, your "equation" actually does apply.

Going from 87 to 91, sure with OUR cars and others that recommend 91 octane per manual...

Going from 91 to anything above it, snake oil.

well is it a bad thing using 94 octane? why should fuel lower than 94?

my mechanic told me that my engine requires me to use 94octane.
after internal work had been done.

What internal work did you have done?