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Author Topic: How do stock tunes deal with low octane fuel?  (Read 493 times)
blairl
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« on: May 05, 2022, 08:17:41 AM »

This is a complete shower thought and I have no clue where to post this.  When I was a kid, my parents had a V70 2.4T (ME7) and a B5 Passat 1.8T (had a cable throttle, no clue on engine management).  My parents regularly used 87aki fuel in these.  Did they just survive based on the engines being strong and the tune being conservative?  Is this what the "x during continuous knock" maps are intended for?  Searching for octane in the FR yields surprisingly little and I'm just curious.  I imagine the strategy would be along the lines of:

Pull timing first (it's the fastest variable the ECU has control over but also raises EGT)
Very rich AFR next (rich mixture burns cooler, cools combustion chamber, also lowers EGT)
Reduce load last if you can't spray the knock out with fuel and timing adjustments

I've heard people say stuff along the lines of "cars in the US are required to run on 87aki without damage".  A quick google search is inconclusive.

Just looking for some insight










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nyet
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« Reply #1 on: May 05, 2022, 12:05:12 PM »

Yes. See FR for more details, but all of the above, and more, are done to protect the motor.
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ME7.1 tuning guide (READ FIRST)
ECUx Plot
ME7Sum checksum checker/corrrector for ME7.x

Please do not ask me for tunes. I'm here to help people make their own.

Do not PM me technical questions! Please, ask all questions on the forums! Doing so will ensure the next person with the same issue gets the opportunity to learn from your experience.
blairl
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« Reply #2 on: May 05, 2022, 01:12:45 PM »

Yes. See FR for more details, but all of the above, and more, are done to protect the motor.

I literally just learned of the alfa FR like two days ago, I didn't realize it was in English. 
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eliotroyano
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« Reply #3 on: May 05, 2022, 02:19:17 PM »

conservative
I have had to deal with very bad fuels, 75-80RON with hot ambient temps all around and that is the "key word". Inclusive NA cars suffers a lot. Normal stuff will help but in my case adjust cams timing can help too.
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tadope
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« Reply #4 on: May 12, 2022, 07:16:46 PM »

also your parents probably drive like old grannies.

even if the stock tune didn't have so many protections, i'm sure driving gentle wouldn't do much even with bad gas.

a lot of people never see WOT. I have friends that think that their car will break if they rev over 4k rpm.
so they never do,  like ever.
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tadope
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« Reply #5 on: May 12, 2022, 07:18:21 PM »

i feel like our me7 ecu must be pretty darn protective, or our engines extremely durable.

I was running a bad tune that I got (no name will be mentioned) and it was constantly asking for 15afr and 24lbs boost from 5.5krpm to redline.

I smashed on it like this for a long time.
didn't hurt the engine at all.
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Blazius
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« Reply #6 on: May 13, 2022, 05:35:16 AM »

i feel like our me7 ecu must be pretty darn protective, or our engines extremely durable.

I was running a bad tune that I got (no name will be mentioned) and it was constantly asking for 15afr and 24lbs boost from 5.5krpm to redline.

I smashed on it like this for a long time.
didn't hurt the engine at all.

It's both but its not ideal.

If it was done properly you would make more power, have better economy, wouldnt blow pistons on highway runs etc, obviously.
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nyet
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« Reply #7 on: May 13, 2022, 10:08:05 AM »

"Didnt blow up yet" is not a good metric of anything.
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ME7.1 tuning guide (READ FIRST)
ECUx Plot
ME7Sum checksum checker/corrrector for ME7.x

Please do not ask me for tunes. I'm here to help people make their own.

Do not PM me technical questions! Please, ask all questions on the forums! Doing so will ensure the next person with the same issue gets the opportunity to learn from your experience.
tadope
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« Reply #8 on: May 15, 2022, 02:48:56 PM »

"Didnt blow up yet" is not a good metric of anything.

well, if it was a boosted 90's honda it would have blown up after one or two highway pulls for sure.

this bad tune was actually what prompted me to learn to diy. I realized I couldn't trust tuners.
so I ended up fixing the tune myself.
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