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Discussion Starter #1 (Edited)
As promised: We ran down the 87 in our first tank of fuel and filled with 91. There was a little mixing, so it was not 100% 91, but it was a lot better than before. Roughly, you are looking at 9 HP and 11 lb-ft torque above 4000 rpm.

But there is another way to measure what the computer is seeing and that is Knock Control. Knock control starts at 100 % when the ECU is programmed of the car is first started. KControl was around 100% for 87 octane. It decreased to 60-70 % for the 91 octane we used and added ignition timing as a result. Knock control is continually being adjusted as you drive.

You can view the knock control varying through a dyno or on-road performance run with a laptop. The XY chart is an excellent way of seeing this.

Or you can view the results through our free app Hondata Mobile.
 

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Wow...great to see these cars reacting to the better gas this way...I guess I'll be running the 93 that we get here in NY
 

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That is pretty interesting. Seems like a big adjustment for knock control. Wonder what the difference is with 89 and 93.
 

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@Hondata , can you post some data using 93 octane, as that is mostly available here in FL for me
 

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Discussion Starter #5
No 93 easily available, sorry. 93 will be a little bit better than 91. The lowest we have seen Knock Control on the Civic is 54%, so with the change from 87 to 91, we have got most of the benefit.

Rule of thumb with a turbo car. Run the highest octane you can.
 

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As promised: We ran down the 87 in our first tank of fuel and filled with 91. There was a little mixing, so it was not 100% 91, but it was a lot better than before. Roughly, you are looking at 9 HP and 11 lb-ft torque above 4000 rpm.



But there is another way to measure what the computer is seeing and that is Knock Control. Knock control starts at 100 % when the ECU is programmed of the car is first started. KControl was around 100% for 87 octane. It decreased to 60-70 % for the 91 octane we used and added ignition timing as a result. Knock control is continually being adjusted as you drive.



You can view the knock control varying through a dyno or on-road performance run with a laptop. The XY chart is an excellent way of seeing this.



Or you can view the results through our free app Hondata Mobile.


Trying to learn more about knock. What is an unsafe % of knock that you would want to pay attention to?


Sent from my iPhone using Tapatalk
 

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As promised: We ran down the 87 in our first tank of fuel and filled with 91. There was a little mixing, so it was not 100% 91, but it was a lot better than before. Roughly, you are looking at 9 HP and 11 lb-ft torque above 4000 rpm.



But there is another way to measure what the computer is seeing and that is Knock Control. Knock control starts at 100 % when the ECU is programmed of the car is first started. KControl was around 100% for 87 octane. It decreased to 60-70 % for the 91 octane we used and added ignition timing as a result. Knock control is continually being adjusted as you drive.



You can view the knock control varying through a dyno or on-road performance run with a laptop. The XY chart is an excellent way of seeing this.



Or you can view the results through our free app Hondata Mobile.


Trying to learn more about knock. What is an unsafe % of knock that you would want to pay attention to?


Sent from my iPhone using Tapatalk
Knock itself is just plain bad...you don't want ANY knock whatsoever...detonation (knock is what it's called because it sounds like a knocking sound inside the engine) will destroy your engine...modern ECU's are able to adjust on the fly to prevent it, that's what the knock control is doing...

What Hondata is posting about here is the ECU's knock control, or what percentage the ecu is actively trying to prevent detonation...as you increase the octane of fuel, the ecu realizes it can decrease it's knock control and increase ignition timing...therefore making more power...

For instance...to do this on my Mustang from 1994...you would have to increase ignition timing manually...by basically removing the distributor...turning a couple degrees...putting it back in...testing to see that you don't hear any detonation and adjusting fuel pressure, etc manually to account for the increase in ignition timing...it's really quite an annoying process at times...

As someone that learned wrenching on cars that way back when I was in my teens...the idea that modern ECU's can do things like this automatically is still mind blowing sometimes
 

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I was unaware that you could monitor the degree that the ECU controlled knock compared to its maximum setting. If there is a linear relationship between a change in octane and a change in knock control, and increasing octane from 87 to 91 resulted in a 33% decrease in knock control, would it be safe to predict that going from 87-octane to 93-octane could result in a 48% decrease in knock control? (Knock control would be about 52% on 93 octane.)

If that is true and there is also a linear relationship between a change in knock control and a change in power, and a 33% decrease in knock control resulted in a 4% increase in horsepower, would it be safe to predict that a 48% decrease in knock control would result in a 5-6% increase in power? (93-octane might produce and additional 14 hp over 87 octane.)

On the continued subject of optimal shift points, I noticed that on 91-octane, HP did not fall off as rapidly near redline. That might imply you could hold rpm a little higher on high-octane and enter the next gear at a slightly higher rpm. Perhaps that would keep the engine in a slightly sweeter part of its power curve.
 

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I was unaware that you could monitor the degree that the ECU controlled knock compared to its maximum setting. If there is a linear relationship between a change in octane and a change in knock control, and increasing octane from 87 to 91 resulted in a 33% decrease in knock control, would it be safe to predict that going from 87-octane to 93-octane could result in a 48% decrease in knock control? (Knock control would be about 52% on 93 octane.)

If that is true and there is also a linear relationship between a change in knock control and a change in power, and a 33% decrease in knock control resulted in a 4% increase in horsepower, would it be safe to predict that a 48% decrease in knock control would result in a 5-6% increase in power? (93-octane might produce and additional 14 hp over 87 octane.)

On the continued subject of optimal shift points, I noticed that on 91-octane, HP did not fall off as rapidly near redline. That might imply you could hold rpm a little higher on high-octane and enter the next gear at a slightly higher rpm. Perhaps that would keep the engine in a slightly sweeter part of its power curve.

its amazing what these factory ECU's can do these days isn't it?

as for the shift points..Looking at the chart, and I still think the evidence suggests anything above 6k is slowing you down...I could be wrong on this...but its my guess from just looking at the charts...

Edit: You can also see, that not only is tq falling off rapidly after 6k, but you're actually starting to bleed horsepower as well...im really thinking the car rags were overrevving the MT cars by ~1000rpm in their testing...shifting between 5850-6000 really could be the sweet spot
 

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Discussion Starter #11
Trying to learn more about knock. What is an unsafe % of knock that you would want to pay attention to?


Sent from my iPhone using Tapatalk
If the Knock Control climbs above 100% that indicates a low octane fuel. The knock control algorithms are very good. As Knock Control climbs, the ECU retards ignition then reduces boost. Knock Control can also climb if the engine driven hard and is very hot.
 

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Discussion Starter #14 (Edited)
This is our stock 2017 Civic Si. Stock as in stock clutch, intake, cat and exhaust.

Bottom red line 200 hp and 235 lb-ft torque as delivered from the Honda dealership.
Top orange line E85 and tuning for 265 HP and 283 torque.

There is more in it, but we would need to upgrade the clutch.


 

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This is our stock 2017 Civic Si. Stock as in stock clutch, intake, cat and exhaust.

Bottom red line 200 hp and 235 lb-ft torque as delivered from the Honda dealership.
Top orange line E85 and tuning for 265 HP and 283 torque.
(My 10,000th post, and it's not in the 7th Gen subforum. :D)

This is quite impressive amount of improvement from stock, are you planning on doing a similar tune with the Accord 2.0T engine?

If only Honda decided to keep the Coupe model......
 

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If the Knock Control climbs above 100% that indicates a low octane fuel. The knock control algorithms are very good. As Knock Control climbs, the ECU retards ignition then reduces boost. Knock Control can also climb if the engine driven hard and is very hot.
Low octane fuel relative to what? Does it imply the ECU is at it's limit for how much it can retard timing? Does the ECU's ignition software have a limited range?

Based on other forum discussions, I thought the ECU's underlying ignition map was based on very high octane, perhaps 95 or 96. On 95-octane, the ECU uses its most "advanced" ignition map. If any octane less than that is used, which implies always, the ECU retards the ignition (compared to the 95-octane map), as much as required to prevent knock. Is that correct? To me that seemed consistent with the knock control running at 100% on 87-octane and only 65% or so on 91-octane. I'd appreciate any further explanation, or correction, on this subject.

And lastly, I did not know the ECU could also reduce boost to control knock. That makes perfect sense and may even explain why the boost was 17 psi during your 87-octane test when all the formal literature states the Accord's max 2.0T boost is around 20 psi. Now for the bigger question, if we run 93-octane, should we expect more boost too? By any chance, did your 91-octane test also monitor boost? Was it greater than 17 psi?
 

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Discussion Starter #17
Our assessment is that Honda tunes their vehicles with a spec high octane fuel - something like 100 octane. Here are the technical notes for the earlier NA Hondas: https://www.hondata.com/help/flashpro/index.html?knock_control_tables.htm

The ECU is not at it's limit for retarding timing in any of our tests. The ECU will retard a lot more if needed. There is a limit to how much ignition it will automatically add. You can manually add more ignition timing - but if you add too much the engine will knock and the timing will be retarded.

The lowest we have seen knock control on the Civic engines is 54% with customers running 93 octane.

Dont get too hung up on boost levels. The Civic and Accord's fundamental engine strategy is torque control. The computer will vary boost, throttle position and ignition to achieve a specified level of torque. For example in the Civic we see the ECU run less boost and more ignition timing when using higher octane to achieve the same torque.

The boost levels on the 87 Octane were similar to 91.

Both the Civic Si and Accord show less boost than advertised, but dyno with either the same or more torque and power.
 

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Hondata is the BEST! I used to have Hondata reflesh on my old TSX and loved it!! Now Honda has Turbo so the difference would be more then before!
 

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As promised: We ran down the 87 in our first tank of fuel and filled with 91. There was a little mixing, so it was not 100% 91, but it was a lot better than before. Roughly, you are looking at 9 HP and 11 lb-ft torque above 4000 rpm.

But there is another way to measure what the computer is seeing and that is Knock Control. Knock control starts at 100 % when the ECU is programmed of the car is first started. KControl was around 100% for 87 octane. It decreased to 60-70 % for the 91 octane we used and added ignition timing as a result. Knock control is continually being adjusted as you drive.

You can view the knock control varying through a dyno or on-road performance run with a laptop. The XY chart is an excellent way of seeing this.

Or you can view the results through our free app Hondata Mobile.
These results are very interesting. It seems if I have this right, running with a higher octane fuel versus 87 is better for the engine in terms of power and reliability. The knock data seems to show less knock with higher octanes, indirectly due less knock control. Why would Honda recommend regular, other than marketing and cheaper price, when they know the chance for knock is greater with regular gas?
 

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These results are very interesting. It seems if I have this right, running with a higher octane fuel versus 87 is better for the engine in terms of power and reliability. The knock data seems to show less knock with higher octanes, indirectly due less knock control. Why would Honda recommend regular, other than marketing and cheaper price, when they know the chance for knock is greater with regular gas?
Well you have to remember who 98% of the buyers of this car are. They are people who want an economical car that runs on whatever cheapo gas they can put in it. Reliability isn't in question when running 87 octane, it's designed to run just fine on that gas.

Obviously running a higher octane fuel will be better for performance...but just take a look at your fellow Accord drivers out on the highway and tell me that they really care about that. Most of the '18 Accords I see in my area are being used for Uber/Lyft...
 
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