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Not to be combative, but that is all pure conjecture. And my tests using the TorquePro Knock detector plugin would SEEM to prove that there is no detonation for the given conditions in my tests using 87.
Couple that with the fact that I see ZERO difference between timing advance at constant speed highway driving for 87 and 91, I'm still not convinced.
You're right about one thing though: we need a scanner that reads knock sensor output, but I don't even see a PID for that.
Not combative, you're right, it is conjecture. I think the device 6spd is using can directly measure knock retard, he might be able to help us more since I don't have access to warm weather at the moment.
But according to my experiments, if my conjecture was right, the knock sensor likely won't trigger at highway speeds for either 87 or 93, so matter as your engine load doesn't exceed 50%. If it exceeds 50%, it triggers using 87 at 50-60F IAT. If it exceeds 70%, it triggers using 93 at 50-60F IAT.
It appears to me the engine was designed to always try to be squeezing for top performance, using the knock sensor to avoid knock. In this manner, the engine is always running at the upper cusp of performance, no matter what fuel you put in it.
You'll notice that timing never goes above 40 degrees -- that's obviously rule based. Below 40 its a spread -- that's likely based on tables and operating parameters. At higher loads, past some threshold, timing begins to delay linearly (on average statistically) with the load... that type of behavior looks like knock sensor to me. And the behavior is amplified with 87, which makes me suspect its the same knock sensor process in 93.
6spd also mentioned that he detected some knock with 91 above 50% engine load, which lends credibility to this conjecture.
Rusty, I didn't detect any knock during my 91 octane run, I only saw the ECU adding Knock Retard for brief periods of time.
FlashPro Help <use this thing, go under tuning your vehicle and then knock control tables.
Rusty, I didn't detect any knock during my 91 octane run, I only saw the ECU adding Knock Retard for brief periods of time.
FlashPro Help <use this thing, go under tuning your vehicle and then knock control tables.
Just filled up with with 87 to test!
Right -- knock retard is the question. You saw knock retard above 60-70% load? If so then that is in agreement with my data as well. Though the degree may differ due to differences in IAT. Looks like mine was warmer than yours (50-60F here in motion).
Rusty, I didn't detect any knock during my 91 octane run, I only saw the ECU adding Knock Retard for brief periods of time...
Did you mean to say timing retard instead of knock retard?
Also, it's important to remember that any increase in engine load will cause timing retard, regardless of fuel being run. Just because you detect timing retard does not mean it's due to knock.
Will be interested to see your results from running 87. I'm still curious why there is such a huge disparity between your timing reading with 91 vs my timing reading with 87 and 91.
Not to be combative, but that is all pure conjecture. And my tests using the TorquePro Knock detector plugin would SEEM to prove that there is no detonation for the given conditions in my tests using 87.
Couple that with the fact that I see ZERO difference between timing advance at constant speed highway driving for 87 and 91, I'm still not convinced.
You're right about one thing though: we need a scanner that reads knock sensor output, but I don't even see a PID for that.
Are you referring only to highway cruising, or cruise and WOT? I can see not really having detonation with 87 at cruise, but WOT, I don't see how you wouldn't incur knock and retarded timing.
I think Honda's Knock control methodology is much more complex and variable than it seems.
Rustylogic - you said you never saw above 40 degrees of timing, which means you probably never hit the section of the timing map that contains them. There's very few cells that exceed that, and you'd probably only see them at no load reving.
Instead of using the Engine Load, can you graph against map value in kPa? That's how the tables are setup in Hondata - RPM vs Map.
When you look at the MBT ignition table vs the Knock ignition limit, you can see that MBT is much lower than the knock limit at lower loads, which means - run crappy gas and it won't matter. Once you get to higher engine load, the numbers go negative, especially on the high high speed table.
Are you referring only to highway cruising, or cruise and WOT? I can see not really having detonation with 87 at cruise, but WOT, I don't see how you wouldn't incur knock and retarded timing..
For the knock detect plug in tests, I'm referring to WOT to just short of red line. You start at slow rolling speed (~20 mph in 3rd gear and punch it and hold to red line or when the app tells you it's complete). I ran 3 or 4 of these on 87, (one was going uphill) and the app never detected detonation. It was ~40F at ~1650' elevation.
Originally Posted by screaminz28
...I think Honda's Knock control methodology is much more complex and variable than it seems....
Rustylogic - you said you never saw above 40 degrees of timing, which means you probably never hit the section of the timing map that contains them. There's very few cells that exceed that, and you'd probably only see them at no load reving.
Instead of using the Engine Load, can you graph against map value in kPa? That's how the tables are setup in Hondata - RPM vs Map.
When you look at the MBT ignition table vs the Knock ignition limit, you can see that MBT is much lower than the knock limit at lower loads, which means - run crappy gas and it won't matter. Once you get to higher engine load, the numbers go negative, especially on the high high speed table.
Timing plotted as function of Intake Manifold Pressure (psi)
I bet that hot summer 91 data looks very similar to the cold 87 plot. Will be looking to do that experiment this year (unless we have someone here who lives in warm climate already and can contribute that data).
That is really one of the main pieces of data that will be able to tell us whether or not its "ok" to run 87 under certain conditions without the risk of engine damage. The other part of data is actual experience: who has run 87 in their vehicle with no complications, and for how long?
Last edited by RustyLogic; Feb 2, 2015 at 09:02 PM.
Don't have to much time to go over the data but I did two 3rd gear pulls rolling into it, so going from 2000 rpm and slowly increasing pedal to 100% at about 3300 rpm on 87 Octane. At 60-ish kPa the ECU pulled about 4 to 5 degrees off the total timing. At 98 kPa it pulled 6 degrees and then started to added timing back only pulling 3 degrees off total timing and it was hovering around 19 to 20 deg. Only recorded 2 knock counts on this pull, IAT was 32 deg F.
Highway, 70 mph, MAP= 47kPa IAT= 30 deg F. IGN= 29 deg F.
That's around 8.7 psi that it starts to occur -- seems to be somewhat consistent with my previous data. I guess your IAT is 30F cooler than mine was, which may account for the smaller retard. Are you using factory specified ignition tables?
Don't have to much time to go over the data but I did two 3rd gear pulls rolling into it, so going from 2000 rpm and slowly increasing pedal to 100% at about 3300 rpm on 87 Octane. At 60-ish kPa the ECU pulled about 4 to 5 degrees off the total timing. At 98 kPa it pulled 6 degrees and then started to added timing back only pulling 3 degrees off total timing and it was hovering around 19 to 20 deg. Only recorded 2 knock counts on this pull, IAT was 32 deg F.
Highway, 70 mph, MAP= 47kPa IAT= 30 deg F. IGN= 29 deg F.
Will post more when I have more time!
How does the FlashPro tuning figure into all of this? Are we comparing apples to oranges if you are running the FlashPro?
That's around 8.7 psi that it starts to occur -- seems to be somewhat consistent with my previous data. I guess your IAT is 30F cooler than mine was, which may account for the smaller retard. Are you using factory specified ignition tables?
Rusty I've converted my files to CSV files. If you could plug them into MATLAB that would be awesome! PM me.
Originally Posted by nfnsquared
How does the FlashPro tuning figure into all of this? Are we comparing apples to oranges if you are running the FlashPro?
I removed my tune and used the J32 basemap for the tests.
...I removed my tune and used the J32 basemap for the tests.
How can two 2004 6MTs have such a significant difference in timing readings at cruise speed? Yours at 29.5 and mine at ~34. Can temperature cause that much of a difference?
I now have > 200K miles on my 2006 and I've used premium 95%-98% of those times. I used mid-grade otherwise. (My gas cap said recommended not required. I've done normal maintenance through the years w/o any issues engine wise. Now with that side, I've always been pissed with Acura TL's having to use premium grade gas or its recommended. Apparently other have agreed and part of why their sales fell through the floor as gas prices went up. (remember I said part of the reason). >90% of the cars on the road today can operate on 87 octane fuel without any issues, with many of those car offering the same amenities as the TL. I do wish the 2015 Acuras much success and hope it does well in the market, but I wont be one of those buyers because of the required fuel. This also has nothing again to do with not being able to afford one.
I now have > 200K miles on my 2006 and I've used premium 95%-98% of those times. I used mid-grade otherwise. (My gas cap said recommended not required. I've done normal maintenance through the years w/o any issues engine wise.
...... wait a minute, you have a 2006 model Acura TL and your gas cap says "91 recommended" not "91 required"? It's the same engine. If yours says "recommended" then all they did was change the gas cap label. Can you provide a photo?
Last edited by RustyLogic; Feb 4, 2015 at 09:38 PM.
Your vehicle is designed to operate
on premium unleaded gasoline with a
pump octane of 91 or higher. Use of
a lower octane gasoline can cause
occasional metallic knocking noises
in the engine and will result in
decreased engine performance. Use
of a gasoline with a pump octane less
than 87 can lead to engine damage.
We recommend quality gasolines
containing detergent additives that
help prevent fuel system and engine
deposits."
The 2006 model has the same engine as the 2005. The answer to this thread is that you can use 87 octane without engine damage, according to Acura themselves.
How can two 2004 6MTs have such a significant difference in timing readings at cruise speed? Yours at 29.5 and mine at ~34. Can temperature cause that much of a difference?
Lots of variables, I do have snow tires and they are smaller diameter than stock, that might be causing the variation.
Your vehicle is designed to operate
on premium unleaded gasoline with a
pump octane of 91 or higher. Use of
a lower octane gasoline can cause
occasional metallic knocking noises
in the engine and will result in
decreased engine performance. Use
of a gasoline with a pump octane less
than 87 can lead to engine damage.
We recommend quality gasolines
containing detergent additives that
help prevent fuel system and engine
deposits."
The 2006 model has the same engine as the 2005. The answer to this thread is that you can use 87 octane without engine damage, according to Acura themselves.
My 04 says premium fuel only on the gas door.
Here's my scatter plot, my excel csv files are huge! 200Hz sample rate was a little much . Blue is 87/E10 mix and Red is 91 Octane
Hi 6spd, are there differences between the FlashPro base map and the factory supplied ECU? I'm guessing there may be from your charts?
Experiments aside, if Acura says the 2006 model is only "91 recommended" and the engines are the same, that's the answer to all our questions: 87 octane can be used safely. I'm going to try to reach out to Acura for comment and see if I can by any chance get information from them.
WTF, that's 180 out from Rusty's results, correct?
And I also have smaller diameter snow tires: 225/45/17, so that can't be it.
I would say results are some what similar but I think the difference may have to do with the basemap that I am running, this scatter plot is only of normal driving with a mix of highway and city. I didn't experience any knock on either one of these datalogs, it was only during my two 3rd gear pulls that i experienced 2 & 3 knock counts, these are not included on the plot.
Bah I have the same tire size, General's right? Strange. Maybe ethanol content?
nfn, how long have you been putting 87 in your car for? And you haven't had any complications?
Not all that much. I've run 87 on road trips 6 times/year since 2007 and pretty much run 87 for the last year since I've been putting a ton of road miles on the car due to business.
No issue whatsoever, but you're talking to a guy that rarely gets above 4K rpm and where summer temps rarely exceed 90F.
Originally Posted by 6spd-GERCO
I would say results are some what similar but I think the difference may have to do with the basemap that I am running, this scatter plot is only of normal driving with a mix of highway and city. I didn't experience any knock on either one of these datalogs, it was only during my two 3rd gear pulls that i experienced 2 & 3 knock counts, these are not included on the plot.
Bah I have the same tire size, General's right? Strange. Maybe ethanol content?
How do you KNOW those were knock counts? Just asking...
"Fuel Recommendation:
Your vehicle is designed to operate on a premium unleaded gasoline with a pump octane of 91 or higher. If this octane grade is unavailable, regular unleaded gasoline with a pump octane of 86 or higher may be used temporarily. The use of regular unleaded gasoline can cause metallic knocking noises in the engine and will result in decreased engine performance. The long-term use of regular-grade gasoline can lead to engine damage."
The 2006 manual:
"Your vehicle is designed to operate on premium unleaded gasoline with a pump octane of 91 or higher. Use of a lower octane gasoline can cause occasional metallic knocking noises in the engine and will result in decreased engine performance. Use of a gasoline with a pump octane less than 87 can lead to engine damage."
The difference?
- 2005 manual defines "regular unleaded gasoline" as 86 octane or above. Long term use of such "regular unleaded gasoline" (86 or above) can lead to engine damage.
- 2006 manual makes no definitions, but simply refers to octane levels. Levels only below 87 may lead to engine damage. Levels below 91 but at 87 or above will only lead to decreased engine performance, and possibly knocking noises.
- Nowhere does either manual state that use of 87 will lead to increased building of carbon deposits.
I would say this is factory approval to use 87. My earlier data also leads me to believe this. If I hear anything from Acura specifically, I will let you know.
Thank you for allowing Acura Client Relations the opportunity of responding to your message. Client satisfaction is of utmost importance to us and we assure you of our interest in providing you with accurate information.
As the manufacturer of the vehicle, we encourage following the fuel recommendations listed in the Owner's Manual. Upon further review, we confirmed premium unleaded fuel with a pump octane of 91 or higher are recommended for both the 2005 and 2006 TL. Although the verbiage expressed in the Owner's Manuals may vary slightly, the recommendations are the same.
I'm asking them now to confirm that the statement "use of fuel below 87 octane may lead to engine damage" implies that use of 87 octane or above does not. Will let you know if they actually do. But at this point, I'm already convinced. 2006 manual clearly states that only fuel below 87 octane can lead to engine damage, and the company has confirmed that recommendations between vehicles are the same.
Can anyone interpret this in any other way? I believe we finally have an answer to this age-old question.
Last edited by RustyLogic; Feb 5, 2015 at 07:30 PM.
I know the sticker next to my gas cap refers to 91 or above, at any rate. Not sure why you want Acura to confess to something. Want to run 87, go ahead.
I know the sticker next to my gas cap refers to 91 or above, at any rate. Not sure why you want Acura to confess to something. Want to run 87, go ahead.
Exactly. If you feel comfortable running it, so be it. If by chance your engine shits the bed, don't expect Acura to be replacing your engine. Remember, you're also talking to someone in a call centre, not an engineer and who knows where they get their information from.
And if your engine does shit the bed from running 87 and you decide to sue Acura for what's written in their owners manual, something tells me that Acura has much deeper pockets and will be able to run you out of the court room, since lawyers have many ways to extend law suits which inevitably will leave you broke.
I seem to have stumbled into a discussion about semantics regarding technical, user-facing engineering documents. (I happen to do a bit of this for a living.)
I must preface by stating that the wording in such documents is carefully constructed and follows industry standard style guides. The one pertaining to my field is this one: https://development.standards.ieee.o...t/styleman.pdf
Note page 9, the description of the use of the word "should" and its equivalence to "is recommended that". The argument you're making, OP is that you can run 87 because running 91+ is a recommendation, not a requirement. You're correct. It's not a requirement. Now let's stop for a moment to think about why it isn't a requirement. The word requirement indicates a mandatory condition of operation. We all know that the car can run on 87, therefore it would be incorrect to state that running 91 is a requirement. Thus the most strict end-user description of operation would be to state that it is recommended to run 91 (or that you should run 91, per IEEE-SA Standards Style Manual).
The grand fallacy is that you assume the outcome of your engine performance or longevity would be the same either way (87 or 91) since running 91 isn't, to use engineering terminology, a requirement. Well I'll tell ya what. I'll go ahead and run 91 because I understand why engineering recommendations are put in place and I understand why they use the language that they do. If you can understand the difference between our spoken language and how those same words are carefully defined in engineering publications to be used in industries throughout the world, you might have a second look at the bullshit you're putting in your gas tank.
We appreciate you following up with this added correspondence. Our office has confirmed the use of premium unleaded gasoline with a pump octane of 91 or higher is recommended for all Acura vehicles. The use of lower octane fuel than 91 can cause occasional metallic knocking noise in the engine and will result in decreased engine performance. The use of gasoline with pump octane less than 87 can lead to engine damage and is not recommended.
"91 recommended" not "91 required".
I'll take measurements for 93 again in the summer, and see where the ignition timing curve moves.
There is zero change in timing between 87 and 91 for highway cruising in my car and I've done several hard pulls to red line using 87 with zero detonation. Granted, it's much cooler here. I don't have any issue running 87 in my car for highway driving. Period.
Besides "pure" 93 (several fill ups) and "pure" 87 (2 fillups), I tried a mix, which I estimated to be around 91.4 octane. Here is the result. The differences between 91.4 and 87 are less apparent than with 93. So additional octane above 91 actually improves performance over 91. Therefore, the dropoff in the timing curve is the knock sensor retardation.
A few conclusions we can make right now to this thread:
1) Third generation TL is in the "91 recommended" category, not the "91 required".
2) The knock sensor is used to retard timing under all octane levels. The octane level shifts at what load/IAT the engine begins to rely on the knock sensor. This means even when you run 93, the knock sensor will "detect knock" at minuscule levels before they are harmful, and adjust timing.
3) Only use of octane below 87 may lead to engine damage. 87 or above, and below 91, leads to decreased performance and possible ping/knock with a combination of high temperatures and high load.
Everyone is free to use whatever fuel they feel most comfortable using. But let the above information be a guide.
Last edited by RustyLogic; Feb 6, 2015 at 09:38 PM.
... Therefore, the dropoff in the timing curve is the knock sensor retardation.
How do you know the knock sensor was activated? More likely, I'd say the ECU is following the applicable timing curve based on octane (as described in the FlashPro help document under Knock Control Tables).
Because the only way the ECU is able to measure octane levels is by knock sensor activation. And clearly, putting 93 in compared to dealer "recommended" of 91 changes these timing tables.
Because the only way the ECU is able to measure octane levels is by knock sensor activation. And clearly, putting 93 in compared to dealer "recommended" of 91 changes these timing tables.
Source? Just asking..
And here's a quote from the FlashPro help file:
"Thus the ECU may run less timing than the ignition tables at certain load/rpm points, even if it does not detect noise from the knock sensor."
Yes, there are upper bound and lower bound limits for the timing. And the timings are functions of RPM and load.
But the only thing changing in my experiments is the octane rating. There is no way for the ECU to know the difference in fuel octane without input from the knock sensor.
"Fuel Recommendation:
Your vehicle is designed to operate on a premium unleaded gasoline with a pump octane of 91 or higher. If this octane grade is unavailable, regular unleaded gasoline with a pump octane of 86 or higher may be used temporarily. The use of regular unleaded gasoline can cause metallic knocking noises in the engine and will result in decreased engine performance. The long-term use of regular-grade gasoline can lead to engine damage."
The 2006 manual:
"Your vehicle is designed to operate on premium unleaded gasoline with a pump octane of 91 or higher. Use of a lower octane gasoline can cause occasional metallic knocking noises in the engine and will result in decreased engine performance. Use of a gasoline with a pump octane less than 87 can lead to engine damage."
The difference?
- 2005 manual defines "regular unleaded gasoline" as 86 octane or above. Long term use of such "regular unleaded gasoline" (86 or above) can lead to engine damage.
- 2006 manual makes no definitions, but simply refers to octane levels. Levels only below 87 may lead to engine damage. Levels below 91 but at 87 or above will only lead to decreased engine performance, and possibly knocking noises.
- Nowhere does either manual state that use of 87 will lead to increased building of carbon deposits.
I would say this is factory approval to use 87. My earlier data also leads me to believe this. If I hear anything from Acura specifically, I will let you know.
Sure it's factory approval. That means it's your car, your money, your car's engine life. Being stupid by ignoring
"CAN LEAD TO ENGINE DAMAGE" and continuing to use regular is of course your choice. After all, it's a free country. I do feel for your poor car however.
.
.
+ "Your vehicle is designed to operate on a premium unleaded gasoline with a pump octane of 91 or higher."
No, this is not open to interpretation. I'll continue to live in my ignorance
I know I said this is my last post, but I did want to thank you for posting this as I DID private message RustyLogic and sent him gas lid covers with labels from 2004-2008 Acura TL's and all of which said the same as what you posted. I never got a Private message back, nor a thank you nor a mention of "Someone private messaged me the information I requested" I would like to take the time now and say thanks for allowing me to do find the information you requested and get no reply back.
Continue to run your results and ask "Acura Corp" to give you what you want to hear. I wouldn't know anything since you know, 6 years in an acura dealership meant nothing to most here. When you do happen to get in touch with an engineer at Acura, please let us know, because the reply you got was just a generic response from the answering staff at head corp.
. Blue is 87/E10 mix and Red is 91 Octane
