87 and low octane gas

[alf]

Originally Posted by jonboy99

OP, you gave your name on a public forum. Are you sure you wanted to reveal that detail yet?

Seriously, you allude to the lsd being helpful in avoiding getting stuck on this trip. How is that kind of terrain compatible with going easy on the car to try and avoid knock?

I am not hiding here necessarily. My true identity will surface sooner or later. I do carry alf nick since a college though. Also I have friends on this forum who know me by my full name. 86 community is small and there is just a few Andy's driving BRZ in south west.


And yes, LSD helped me a few times to go thru the road when I was hanging on 3 wheel. Would not make it in front wheel driven car. BTW, if you need to rev up to spin the wheels in a bad terrain it is often too late. A momentum and moderate throttle is your friend. Also I do not anticipate to drive in the roads like all the time. If I get stuck, there is always a truck or SUV passing at least one a day to pull me out of the trouble.

[alf]

I kind of freaked out on this road actually

[alf]

and yes, I agree: this is a proper vehicle for the very road - guys from Colorado.

[FRSBRZGT86FAN]

Originally Posted by alf

A little correction. While the area I will be traveling thru is super sparse, the longest segment of road with no gas stations is 666km long. I troll you not.

By 1000-2000k miles I meant no 91 or better gas. Ppl still live there.

Originally Posted by alf

If Fiat Panda made it (again it is not a troll), I should be able too. And I do have an advantage being 2 wheel driven (as opposed to 1 wheel for the most of cars). Odds that I will get suck are lower than getting TB in first 50k (s)miles.Which I replace as a preventive maintenance before the trip.

Originally Posted by alf

I will surely reveal my plans in more detail, once I commit to the trip. This is just an early research.


And doing it in 86 is a point here.

Out of curiosity how many miles does your twin currently have? I feel like 1000-2000 miles with high knock will do some wear even with a heavily neutered safe tune edited in romraider by steve

[solidONE]

Originally Posted by alf

@steve99 offered to build a 87 map for me. I will run tests here at home to see what driving style works and what does not.

even better

[steve99]

Originally Posted by alf

@steve99 offered to build a 87 map for me. I will run tests here at home to see what driving style works and what does not.


If there is a certain window of RPM/throttle where it works, I will stick to it. Also, I will carry octane boosters.



yes, I must.

It limited what you can do with tune to accomodate such poor fuel as 87 on a 12.5:1 motor. Will need to look at knock under different conditions ond evaluate. The best option woild be to run 91 as a minuim.



I also suspect 87 will not only be lower octane but also lower quality in other terms like additives and deposits as well


I do have concerns with running poor fuels through complex modern fuel systems like this with direct injection



Its certianly not someting id recomend people do

[Tor]

Originally Posted by alf

and yes, I agree: this is a proper vehicle for the very road - guys from Colorado.

What the altitude of the area where there is only 87? As far as I understand, typically areas where only 87 is offered are very high altitude.

With high altitude, the air is thinner and lowers the effective compression of the engine. As such, high octane fuel is not necessarily required as there is a lower combustion pressure. (For forced induction engines of course a different story).

I.e. the engine might run the same on 87 at that altitude as it would on 91 on lower altitude. So if the altitude is very high, don't take out too much ignition timing.

[alf]

Originally Posted by Tor

What the altitude of the area where there is only 87? As far as I understand, typically areas where only 87 is offered are very high altitude.

With high altitude, the air is thinner and lowers the effective compression of the engine. As such, high octane fuel is not necessarily required as there is a lower combustion pressure. (For forced induction engines of course a different story).

I.e. the engine might run the same on 87 at that altitude as it would on 91 on lower altitude. So if the altitude is very high, don't take out too much ignition timing.

This is a very interesting aspect. The altitude in the region I am concerned about is between 900m and 1400m, so it is not exactly see level. I will definitely run some tests with 87 at higher elevation, just to better understand what is happening. Thanks for the info.

[alf]

Originally Posted by steve99

It limited what you can do with tune to accomodate such poor fuel as 87 on a 12.5:1 motor. Will need to look at knock under different conditions ond evaluate. The best option woild be to run 91 as a minuim.



I also suspect 87 will not only be lower octane but also lower quality in other terms like additives and deposits as well


I do have concerns with running poor fuels through complex modern fuel systems like this with direct injection



Its certianly not someting id recomend people do

Steve,
I am totally aware of the risks. In fact I am quite familiar of one of results of knocking often mentioned here https://forums.nasioc.com/forums/sho....php?t=2401576



However the reward is bigger for me here and than a potential risk, which I will do everything to mitigate. Hoping that octane boosters will be effective, which I will test.



As far as 91 vs 93, all we have in south west is 91. Not sure why.


One thing which I am confused is how to see knocking in data logs. I could not find a direct counter. I only see:


Knock Correction (FBKC)
IAM
KC Learned
FLCK

and apparently I have to derive actual events from this like here: https://datazap.me/u/yamadawg770/log...12&mark=89-137

[steve99]

Originally Posted by alf

Steve,
I am totally aware of the risks. In fact I am quite familiar of one of results of knocking often mentioned here https://forums.nasioc.com/forums/sho....php?t=2401576



However the reward is bigger for me here and than a potential risk, which I will do everything to mitigate. Hoping that octane boosters will be effective, which I will test.



As far as 91 vs 93, all we have in south west is 91. Not sure why.


One thing which I am confused is how to see knocking in data logs. I could not find a direct counter. I only see:


Knock Correction (FBKC)
IAM
KC Learned
FLCK

and apparently I have to derive actual events from this like here: https://datazap.me/u/yamadawg770/log...12&mark=89-137

No not that difficuly just change the logged parameters on oft to log iam flkc and flkc or knock correction


Thats all you need leave out the vvt intake and exhaust

[Tor]

Originally Posted by alf

This is a very interesting aspect. The altitude in the region I am concerned about is between 900m and 1400m, so it is not exactly see level. I will definitely run some tests with 87 at higher elevation, just to better understand what is happening. Thanks for the info.

Not sure if 900 meters is enough to have a significant effect. I was thinking more if your plans were to drive in the Rocky Mountains or something like that (2000+ meter). On the other hand, the pressure drop is exponential with the largest drop off at lower altitudes. So it might be worth looking a bit into it.

Regarding logs. Actual knock events are not logged at all. The only thing the ECU is logging is response to what the ECU percieves as being precursor to knock. I.e. the engine never actually knocks, as the ECU preemptively removes timing.

What is being logged, is how much timing the ECU preemptively takes out. The system is so effective, that renowned authorities in tuning says it's not necessary to use knock-ears when tuning Subaru engines and you can fully rely on the ECU logic to take out timing. Most ECU tuning is done per E-tune as well where the tuner never sees the car, let alone would be able to get their ears in the machinery.

As such, it's a matter of not maxing out the capabilities of the system from a safety aspect and minimizing it's intervention for performance optimization. Typically the ECU will remove more timing than necessary and a better result can be achieved by removing a smaller amount from the timing tables.

Anyway, when you look at the logs and see FLKC, it doesn't mean the engine is knocking. Rather that the ECU is taking messures to avoid knocking. Also it stands for Fine Learning Knock Correction. So if you see the same value, e.g. -2 deg at 4000 rpm and load 1.0 all the time, it just mean the ECU once decided to remove the timing and didn't deem that it could reinstate it for the following occurances.

Short version, there is nothing wrong with seeing FLKC here and there if it's of random nature and not excessive values. If you were to take out timing to the point where there is never FLKC, you would need to detune the engine immensely and it would defeat the point of having a system that ensures we can run the optimum timing most of the time.

[Tor]

...wanted to add, that obviously, the ECU can't protect the engine against pre-ignition.

Detonation/knock is the spark being fired too early. I.e. the ECU can intervene and change the ignition timing.

Pre-ignition is uncontrolled burn prior to the spark being fired. I.e. some other source sets off the combustion. E.g. hot spots in the combustion chamber (as an example carbon buildups or the spark plug itself being so hot that it's glowing).

Not sure what kind of pressures are required to make 87 octane auto ignite, but probably even our high compression ratio would be far less. Mazda's new Skyactiv-X engine (compression ignited like a Diesel) has a compression ratio of 16:1 and runs on 87 octane. You would probably need to add boost into the equation for that to be a problem with the FA20.

I would, however, suggest to run the engine fairly rich at wide open throttle (11 AFR) for the cooling effect of the excessive fuel.

[alf]

Originally Posted by Tor

...wanted to add, that obviously, the ECU can't protect the engine against pre-ignition.

Detonation/knock is the spark being fired too early. I.e. the ECU can intervene and change the ignition timing.

Pre-ignition is uncontrolled burn prior to the spark being fired. I.e. some other source sets off the combustion. E.g. hot spots in the combustion chamber (as an example carbon buildups or the spark plug itself being so hot that it's glowing).

Not sure what kind of pressures are required to make 87 octane auto ignite, but probably even our high compression ratio would be far less. Mazda's new Skyactiv-X engine (compression ignited like a Diesel) has a compression ratio of 16:1 and runs on 87 octane. You would probably need to add boost into the equation for that to be a problem with the FA20.

I would, however, suggest to run the engine fairly rich at wide open throttle (11 AFR) for the cooling effect of the excessive fuel.

Thanks for the very elaborative explanation. I will run tests on 87 and will posts results here.

[alf]

Also, I decided to reveal a bit more about the mysterious trip.


The idea is to take BRZ around the world. The route is, LA, hopefully Japan, South Korea, China, Mongolia, Russia, Poland, Germany and Alps, France/Spain/UK and again ship it to USA and drive back home.