Highest Octane For Stock ECU??

semtex · 09-03-2009, 09:36 AM

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).

semtex · 09-03-2009, 09:43 AM

Here's the original discussion thread:
XXX Racing Fuel gains 14whp on stock 370Z

YamahaR6 · 09-03-2009, 02:42 PM

Does anyone here realized that you get less miliage on Octane 94 than 91?

And I honestly can't tell the different between the two except for my pocket.

physics · 11-02-2019, 10:02 PM

I do notice a small difference in engine performance between the 91 octane that I normally put in my 2019 370Z with 12,000 miles and a 93 octane mixture from Sunoco SS 100 race gas and 91 octane pump gas. When I run the 93 octane blended mixture I notice that the engine idles a little more smoothly and more quietly and pulls a little more strongly from a start. With the 91 octane I sometimes get a little pinging and hesitation from a start if I don't feather the clutch correctly, none of that with the 93 octane. The most objective difference that I notice is in my longer term gas mileage indicator, where I get about a 2 mpg increase in mileage with the higher octane. The Sunoco race gas is hard to get here in Northern California and it is expensive, so I normally don't use it. My car's engine and exhaust system are still stock

Rusty · 11-02-2019, 11:05 PM

I get Sunoco 93 right out of the pump here in Pa.

semtex · 09-03-2009, 04:49 PM

USNA94, do you by chance know what 98 RON means in relation to, say, 93 octane here in the US? I'm curious because of the post below:

Quote:

Originally Posted by 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 · 09-03-2009, 05:10 PM

Quote:

Originally Posted by semtex

USNA94, do you by chance know what 98 RON means in relation to, say, 93 octane here in the US? I'm curious because of the post below:

98RON equates to about 92 octane here in the states.

USNA94 · 09-03-2009, 05:24 PM

Quote:

Originally Posted by semtex

USNA94, do you by chance know what 98 RON means in relation to, say, 93 octane here in the US? I'm curious because of the post below:

Here in the states we post the average of the RON and the MON. Other countries sometimes only post the higher number.
The below explanation is copied from: How Much Octane Do I Need?

What is octane? How can it help my engine? two laboratory octane numbers determine the overall octane quality of a gasoline. Both numbers are determined in single-cylinder, variable-compression-ratio engines. The first is the research octane number (RON), where operating conditions are mild. This is the number that gas stations in the 1960s put on their advertising signs out in front, numbers that ranged from a little over 100 to as high as 104. If an engine is detonating (pinging) at part throttle, it usually needs more RON.

The second laboratory octane number is also determined in a single-cylinder, variable-compression-ratio engine and is called motor octane number (MON). The MON test is conducted under more severe operating conditions (higher rpm and higher inlet temperature) than the RON test, and as a result, the number is lower. If an engine is detonating at wide-open throttle, a higher MON will usually satisfy it.

The number shown on the black and yellow sticker on the service station gas pump is the average of the RON and MON, or antiknock index (AKI). If the sticker shows an AKI of 92, RON is typically between 96 and 97, and MON is typically between 87 and 88. The RON and MON can vary slightly but still must average a minimum of 92 to have a pump posting of 92. Higher octane unleaded fuels will have a greater difference between RON and MON. For instance, 76 Unleaded Racing Gasoline has a RON of 106 to 107 and a MON of 94 to 95, which gives an AKI of 100 to 102.

wstar · 09-03-2009, 05:33 PM

I agree that with an older engine/ECU, given a fixed set of engine parameters from the factory, running a higher-than-necessary octane rating is total waste in every respect. However, we know that even on a traditional engine, higher octane fuels allow tuning headroom. When tuning the A:F ratios and the spark timing, you can account for higher octane fuel and get more power that way. The flipside is by tuning for say 110 octane race fuel, you've now made a car that will knock on regular pump gas.

The big question mark with our cars is: given a stock ECU, is the stock ECU smart enough to tune itself upwards for a higher octane fuel automatically? We already know that the stock ECU knows how to de-tune itself when presented with lower-octane fuel by using sensors to detect the onset of knocking and making the appropriate adjustments.

There seems to be some evidence that, when given a much higher octane fuel, our ECU will slow retune itself for higher power using those same sensors as a guide. I find it a bit hard to believe myself, but someone did do a dyno with some 110 race fuel and showed some statistically significant gains a while back.

Edited to add: Even without "oxygenated" fuel, just plain higher octane does allow a higher horsepower tune. By making the fuel more knock resistant, the timing can be advanced further without knocking, which results in more power.

USNA94 · 09-03-2009, 06:17 PM

Quote:

Originally Posted by wstar

The big question mark with our cars is: given a stock ECU, is the stock ECU smart enough to tune itself upwards for a higher octane fuel automatically? We already know that the stock ECU knows how to de-tune itself when presented with lower-octane fuel by using sensors to detect the onset of knocking and making the appropriate adjustments.

It's my understanding that it "tunes" itself using the knock sensor. There is no octane sensor. When it detects the onset of knock using the knock sensor the ECU throttles back thereby reducing performance. If there is no knock when running 91 octane and definitely no knock when running 101 octane, the ECU would never know the difference and run the same. It doesn't open up the throttle any more or provide more power. It just knows there is no knock happening. And the energy content of the gasoline does not go up with octane. 91 octane fuel has ~32MJ/liter of energy, 101 octane fuel has ~32MJ/liter of energy, 121 octane fuel has ~32MJ/liter of energy so the power of the engine is the same. The higher octane will allow you to run a modified engine with a higher compression ratio to get more power though.

wstar · 09-03-2009, 10:26 PM

Quote:

Originally Posted by USNA94

It's my understanding that it "tunes" itself using the knock sensor. There is no octane sensor.

We agree on this, although I think the new knock sensors are supposedly picking it up much earlier, when it's a tiny hint of a knock. You don't actually have to get to where you're risking damage to have the sensor "see" it and adjust.

Quote:

When it detects the onset of knock using the knock sensor the ECU throttles back thereby reducing performance. If there is no knock when running 91 octane and definitely no knock when running 101 octane, the ECU would never know the difference and run the same. It doesn't open up the throttle any more or provide more power. It just knows there is no knock happening. And the energy content of the gasoline does not go up with octane. 91 octane fuel has ~32MJ/liter of energy, 101 octane fuel has ~32MJ/liter of energy, 121 octane fuel has ~32MJ/liter of energy so the power of the engine is the same. The higher octane will allow you to run a modified engine with a higher compression ratio to get more power though.

Here's where we potentially differ (not that I'm solidly in the other camp either, I'm just playing out their side of the argument as best I can, and it's reasonably sound, but has question marks):

The way that the ECU responds to knock is not to "throttle back" literally with the throttle, but to retard the timing, which eliminates the knock at the cost of performance and efficiency. You mentioned this yourself in an earlier post, but I just wanted to be clear on that issue:

Quote:

However, burning fuel with a lower octane rating than required by the engine often reduces power output and efficiency one way or another. If the engine begins to detonate (knock), that reduces power and efficiency for the reasons stated above. Many modern car engines feature a knock sensor which detects knock, and then sends a signal to the engine control unit to retard the ignition timing. Retarding the ignition timing reduces the tendency to detonate, but also reduces power output and fuel efficiency.

Similarly, if you put 110 race gas in a car that was designed and tuned for 93, there's lots of "knock headroom", so to speak. With the higher octane fuel in the tank, a tuner can go into the ECU parameters and advance the ignition timing more aggressively than stock to create more power than was possible on 93 octane due to the higher resistance to knocking the 110 fuel has (the inverse of what we described above, where retarding it reduces power and helps avoid a knock). There's still only X MJ/liter of energy in the higher-octane gas, but by being more knock-resistant, it allows a more aggressive spark timing advance, which results in increased horsepower.

I *think* we both agree on the above - that by tuning the ignition timing manually with an ECU programmer up as far as you can without knocking, on any modern-ish car where that is possible, you can get more horsepower out of 110 gas than 93 gas, even though they both have the same MJ/liter of potential energy within them.

The question mark is whether the ECU is smart enough to do this by itself. Some have claimed that when it detects absolutely no hint of knocking, it slowly advances the timing more aggressively until it finds the first hint of it, and thus self-adjusts upwards (more aggressive spark timing, more power) for higher-octane fuel in much the same manner that we know it self-adjusts downwards for crappy fuel.

Nobody has put out any hard evidence that this is true, but people have mentioned it, and the 110 race gas dyno results seem to indicate that *something* is going on, and this explanation kinda fits the bill.

Shunya · 09-04-2009, 04:49 AM

this topic is getting hot~!

semtex · 09-04-2009, 08:56 AM

Thanks for the info, Ryan.

Blown32, don't get your panties in a wad. Listen, I think this is important. A forum member -- a sponsor no less -- has produced a video showing that XXX oxygenated race fuel produces a 14whp gain in a stock Z. Now, if it turns out that the dyno results were somehow falsified, I think that needs to be exposed. Indeed, if it turns out that the claim of a 14whp gain is BS, as you put it, we'll all owe you a debt of gratitude. On the other hand, if it turns out that the results are valid, then it's important to know that too. We're all after the same thing here -- we all want the truth. For the good of the community, we all want to vet out misinformation, do we not? So ease up, this isn't about you, and I wasn't trying to suggest that you shouldn't express opinions if they contradict those of a sponsor. Rather, I emphasize that IP is a sponsor because if a sponsor is putting out misleading or false info, it's all the more important for it to be vetted out.

As for the original post being about octane ratings, that's certainly true. But I am not the one who opened the door on this race fuel tangent. The OP is actually the first person who alluded to race fuel when he posted a link to gas stations that sell race gas in SoCal (post #5), and then Bullitt mentions it in post #22.

Again, I'm just trying to get to the bottom of this for the sake of getting at the truth. I presume that's what you're interested in as well, so we're really on the same side.

semtex · 09-04-2009, 09:07 AM

Back on the topic of octane ratings, have you guys noticed the slight difference between US-spec Zs and Australian-spec? According to Rudi (post #18), "In the manual for the Australian version, it states: Use UNLEADED PREMIUM gasoline with an octane rating of 98 (RON)." That works out to 93.1 AKI octane, according to this: US Octane VS Other countries Octane Ratings

In the US manual, it says to use 91 octane, and even says 96 RON in brackets. It's only a 2 point difference, but I wonder if we should infer anything from it. Like maybe the engine is in fact optimized for 93 octane? *shrug*

wstar · 09-04-2009, 09:11 AM

Hmm so this XXX fuel thing is interesting. So the basic idea here, if I'm understanding correctly, is that it's a higher octane fuel which also has added oxygen - and this means the extra oxygen in the fuel is effectively leaning out the mix for more power, and the extra octane is preventing the knock that would otherwise occur if you leaned out the mix that much on pump gas?

09-03-2009, 09:36 AM	#1 (permalink)
semtex A True Z Fanatic Join Date: Jan 2009 Location: Behind enemy lines Age: 53 Posts: 5,995 Drives: People to drink Rep Power: 32	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). __________________ "There are no small accidents on this circuit." -- Ayrton Senna 316.8whp & 248 ft/lbs (Dyno Dynamics) \| 319whp & 256 ft/lbs (DynoJet) (04/23/10) Stillen G3 CAI, CBE, Pulley / F.I. LTH / GTSpec Ladder Brace / Setrab Oil Cooler / UpRev-tuned by Forged Perf.

09-03-2009, 09:43 AM	#2 (permalink)
semtex A True Z Fanatic Join Date: Jan 2009 Location: Behind enemy lines Age: 53 Posts: 5,995 Drives: People to drink Rep Power: 32	Here's the original discussion thread: XXX Racing Fuel gains 14whp on stock 370Z __________________ "There are no small accidents on this circuit." -- Ayrton Senna 316.8whp & 248 ft/lbs (Dyno Dynamics) \| 319whp & 256 ft/lbs (DynoJet) (04/23/10) Stillen G3 CAI, CBE, Pulley / F.I. LTH / GTSpec Ladder Brace / Setrab Oil Cooler / UpRev-tuned by Forged Perf.

11-02-2019, 10:02 PM	#4 (permalink)
physics Base Member Join Date: Jun 2011 Location: Berkeley, CA Posts: 40 Drives: 19 Nissan 370Z SC 6M Rep Power: 13	Performance Difference Between 91 and 93 Octane Fuel I do notice a small difference in engine performance between the 91 octane that I normally put in my 2019 370Z with 12,000 miles and a 93 octane mixture from Sunoco SS 100 race gas and 91 octane pump gas. When I run the 93 octane blended mixture I notice that the engine idles a little more smoothly and more quietly and pulls a little more strongly from a start. With the 91 octane I sometimes get a little pinging and hesitation from a start if I don't feather the clutch correctly, none of that with the 93 octane. The most objective difference that I notice is in my longer term gas mileage indicator, where I get about a 2 mpg increase in mileage with the higher octane. The Sunoco race gas is hard to get here in Northern California and it is expensive, so I normally don't use it. My car's engine and exhaust system are still stock __________________ Hotchkis sways, StopTech braided steel brake lines, OptiCoat Pro+ ceramic coating

11-02-2019, 11:05 PM	#5 (permalink)
Rusty Ronin Samurai - Assassin Join Date: Dec 2011 Location: Fayettenam,Pennsyltucky Age: 68 Posts: 34,914 Drives: 2011 Nismo GM 6M Rep Power: 2684436	I get Sunoco 93 right out of the pump here in Pa. physics likes this. __________________ 浪人 - 殺し屋 "The Difficult Anytime, The Impossible By Appointment Only" http://www.the370z.com/members-370z-...o-journal.html

09-03-2009, 05:33 PM	#9 (permalink)
wstar A True Z Fanatic Join Date: Mar 2009 Location: Houston, TX Posts: 4,024 Drives: too slow Rep Power: 3594	I agree that with an older engine/ECU, given a fixed set of engine parameters from the factory, running a higher-than-necessary octane rating is total waste in every respect. However, we know that even on a traditional engine, higher octane fuels allow tuning headroom. When tuning the A:F ratios and the spark timing, you can account for higher octane fuel and get more power that way. The flipside is by tuning for say 110 octane race fuel, you've now made a car that will knock on regular pump gas. The big question mark with our cars is: given a stock ECU, is the stock ECU smart enough to tune itself upwards for a higher octane fuel automatically? We already know that the stock ECU knows how to de-tune itself when presented with lower-octane fuel by using sensors to detect the onset of knocking and making the appropriate adjustments. There seems to be some evidence that, when given a much higher octane fuel, our ECU will slow retune itself for higher power using those same sensors as a guide. I find it a bit hard to believe myself, but someone did do a dyno with some 110 race fuel and showed some statistically significant gains a while back. Edited to add: Even without "oxygenated" fuel, just plain higher octane does allow a higher horsepower tune. By making the fuel more knock resistant, the timing can be advanced further without knocking, which results in more power. __________________ 7AT Track Car! Journal thread / Car setup details Last edited by wstar; 09-03-2009 at 05:35 PM.

09-03-2009, 02:42 PM	#3 (permalink)
YamahaR6 Track Member Join Date: Feb 2009 Location: California Posts: 527 Drives: A Car Rep Power: 17	Does anyone here realized that you get less miliage on Octane 94 than 91? And I honestly can't tell the different between the two except for my pocket.

09-04-2009, 04:49 AM	#12 (permalink)
Shunya A True Z Fanatic Join Date: May 2009 Location: Vancouver Posts: 3,069 Drives: You Crazy! Rep Power: 22	this topic is getting hot~!

09-04-2009, 08:56 AM	#13 (permalink)
semtex A True Z Fanatic Join Date: Jan 2009 Location: Behind enemy lines Age: 53 Posts: 5,995 Drives: People to drink Rep Power: 32	Thanks for the info, Ryan. Blown32, don't get your panties in a wad. Listen, I think this is important. A forum member -- a sponsor no less -- has produced a video showing that XXX oxygenated race fuel produces a 14whp gain in a stock Z. Now, if it turns out that the dyno results were somehow falsified, I think that needs to be exposed. Indeed, if it turns out that the claim of a 14whp gain is BS, as you put it, we'll all owe you a debt of gratitude. On the other hand, if it turns out that the results are valid, then it's important to know that too. We're all after the same thing here -- we all want the truth. For the good of the community, we all want to vet out misinformation, do we not? So ease up, this isn't about you, and I wasn't trying to suggest that you shouldn't express opinions if they contradict those of a sponsor. Rather, I emphasize that IP is a sponsor because if a sponsor is putting out misleading or false info, it's all the more important for it to be vetted out. As for the original post being about octane ratings, that's certainly true. But I am not the one who opened the door on this race fuel tangent. The OP is actually the first person who alluded to race fuel when he posted a link to gas stations that sell race gas in SoCal (post #5), and then Bullitt mentions it in post #22. Again, I'm just trying to get to the bottom of this for the sake of getting at the truth. I presume that's what you're interested in as well, so we're really on the same side. __________________ "There are no small accidents on this circuit." -- Ayrton Senna 316.8whp & 248 ft/lbs (Dyno Dynamics) \| 319whp & 256 ft/lbs (DynoJet) (04/23/10) Stillen G3 CAI, CBE, Pulley / F.I. LTH / GTSpec Ladder Brace / Setrab Oil Cooler / UpRev-tuned by Forged Perf.

09-04-2009, 09:07 AM	#14 (permalink)
semtex A True Z Fanatic Join Date: Jan 2009 Location: Behind enemy lines Age: 53 Posts: 5,995 Drives: People to drink Rep Power: 32	Back on the topic of octane ratings, have you guys noticed the slight difference between US-spec Zs and Australian-spec? According to Rudi (post #18), "In the manual for the Australian version, it states: Use UNLEADED PREMIUM gasoline with an octane rating of 98 (RON)." That works out to 93.1 AKI octane, according to this: US Octane VS Other countries Octane Ratings In the US manual, it says to use 91 octane, and even says 96 RON in brackets. It's only a 2 point difference, but I wonder if we should infer anything from it. Like maybe the engine is in fact optimized for 93 octane? shrug __________________ "There are no small accidents on this circuit." -- Ayrton Senna 316.8whp & 248 ft/lbs (Dyno Dynamics) \| 319whp & 256 ft/lbs (DynoJet) (04/23/10) Stillen G3 CAI, CBE, Pulley / F.I. LTH / GTSpec Ladder Brace / Setrab Oil Cooler / UpRev-tuned by Forged Perf.

09-04-2009, 09:11 AM	#15 (permalink)
wstar A True Z Fanatic Join Date: Mar 2009 Location: Houston, TX Posts: 4,024 Drives: too slow Rep Power: 3594	Hmm so this XXX fuel thing is interesting. So the basic idea here, if I'm understanding correctly, is that it's a higher octane fuel which also has added oxygen - and this means the extra oxygen in the fuel is effectively leaning out the mix for more power, and the extra octane is preventing the knock that would otherwise occur if you leaned out the mix that much on pump gas? __________________ 7AT Track Car! Journal thread / Car setup details

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