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Drogos 11-11-2012 08:45 PM

Tuned for winter gas?
I think we already have winter gas here and as always I am scratching my had over differences in fuel and how it influences my tune. I found pretty interesting article on summer vs. winter fuel. It kind of flipped my notions on winter gas upside down. Higher 02 content, lower vapor pressure and higher octane add-ons at least on the paper should help our tunes. I was tunning my car sometime in spring and don't remember what fuel I was on. Have to talk to my tuner if he has date of the tune in his logs but my question is does it influence the tune and in what way? Should midwest people tune in the winter or summer for safer tune? Link to the article here:

Drogos 11-12-2012 02:06 PM

...non of the Tuners here has any opinion on that?

fishbone 11-14-2012 09:25 AM

The answer is it depends. The car adds timing the colder it gets. Pull logs and monitor how she does in the winter and decide. There is no reason a competent tuner can't nail a tune that works for both hot and cold.

iNVAR 11-14-2012 10:43 AM

Not every map does that. My Stage 2 map from Infamous that I got about 3 years ago has the "Timing Compensation B (IAT)" table zeroed out completely.

fishbone 11-14-2012 12:10 PM

So does mine. I meant "by default"
The table is there and can help cope with exactly what op is asking
In mine, timing is pulled when hot but none added for cold

iNVAR 11-14-2012 12:18 PM


Originally Posted by fishbone (Post 4158758)
So does mine. I meant "by default"
The table is there and can help cope with exactly what op is asking
In mine, timing is pulled when hot but none added for cold

That seems like a fairly safe approach.

Drogos 11-15-2012 12:01 AM

what the hell are you guys talking about ? I am not asking about temperature variations. I am talking about different chemical composition of fuel! Map doesn't know that so it can't compensate for anything.It can react by pulling timing when knock is detected. Not exactly the best approach is it? It like tuning for 93, putting 91 in and hoping for the best. Again my question is: based on the assumption that winter gas is more knock resistant, should cars be tuned on summer fuel only?

Drogos 11-15-2012 07:27 AM

thanks much, that's what I was hoping to hear :)

fishbone 11-15-2012 09:46 AM

No offense op but we were trying to help and gave you the correct answer. Looks like you got frustrated because you had the wrong understanding of summer/winter gas.
If you want to be 10000% positive you should log because none of us can guarantee you anything.

Drogos 11-15-2012 11:05 AM

Dude seriously!?!?!? I know you were trying to help but you were off topic since I didn't ask about lower temperatures you were reffering to. Where the hell in my post do you see me asking about lower temperatures? The only relevance is the fact that yeh, in winter it's won!!
I think I have pretty good understanding of winter vs. summer fuel. Do you? There is enough data out there suggesting that winter gas is more knock resistant just like E85 is, obviously not to such extend. I think it's a good enough reason to raise discussion on how healthy are summer tunes that are used in the winter. We could discuss further but then you will start on other irrelevant issues so what's the point. Also, I never asked about guarantees, you missed it again have you? I asked about opinion, I asked people that understand that subject better then anyone else >>TUNERS. Everything was good and this thread would be done after Infamous voiced his opinion if not for you irrelevant whining.

iNVAR 11-15-2012 11:34 AM

I would think that if winter gas were really more knock resistant, it would be reflected in its AKI #.

fishbone 11-15-2012 11:39 AM

Temperature plays a more important role here. That is where you are wrong and that is why you thought myself and iNVAR were off-topic.

Octane rating is octane rating. If it didn't meet 91 or 93 it would not be labeled as such. Barring that article and all things being equal, under most circumstances there is no need for summer and winter maps. We cannot give you the ultimate answer. It depends on the tune and how your car runs!

However, just looking at gas you are not getting the complete picture.
You may run into other problems making the car not run right, such as overboost, TOO MUCH timing added in the winter.
Like iNVAR and I mentioned, it depends on what the tune is.
If that table that we are talking about is zeroed out, you're good.
But, just so you understand, there IS a table which ADDS timing the colder it gets and SUBSTRACTS timing the hotter it gets.
So if the car is tuned at the very edge of running safe and during the winter now the car adds timing, it CAN throw the car off to unsafe levels and it WILL knock.
So! What does your timing compensation table B (IAT) show?
You should know this since you tuned your car.
Instead of getting angry, you should offer some more background because so far you've come across as missing some crucial overall information and getting hung up on an article you read online.

And, again, just because we have now established and resolved the issue of winter vs summer gas, you should still datalog the car to make sure all is well.

None of the conversation was off-topic, there is no whining here, you are a newbie looking to learn so if you hope for future help, it may be best that you set aside that attitude and aggression. A little humbleness never killed anyone. An attitude will marginalize you here real quick.

fishbone 11-15-2012 11:40 AM


Originally Posted by iNVAR (Post 4160150)
I would think that if winter gas were really more knock resistant, it would be reflected in its AKI #.

Precisely. It would be rated as, as an example 93 during the winter and 91 during the summer. AKI is AKI, all things being equal.
OP has too much of a simplistic and narrow view of the issue.

LE: OP, if your concern is how the car will run during the summer then yes, it is more likely it will run bad if you tuned it in the winter.
It's a moot point asking now since we are in November. I say yes, definitely watch it next summer and see.
How has the car run during this year?
Two tunes are usually necessary if you want balls to the wall power during both summer and winter. You may run max on the threshold of knock during winter, likely you will have to back out during the summer. My original point, which you missed, was that under normal circumstances the car can cope with this.
You've run the car during one season already and are now asking about summer in November. You should have datalogged throughout.

Drogos 11-15-2012 01:58 PM

You see, again this whole conversation is off topic hence my frustration. First of all I haven't tuned my car, it was tuned for me as stated in my OP when I refer to "my tuner". I am aware of issues that might arise from extreme temperatures, addressed this with my tuner, he mentioned exactly what you are talking about and basically told me that this is a non-issue. The car was tuned very conservatively, is being logged all the time and runs great. Can we finally put the temperature issue behind us please.

Going back to my OP I have asked very simple, very specific question about FUEL. You were the one who went off on assumptions ...did you even read my OP? Stop putting words in my mouth, read OP and trust me I will be very humble. After all this we are back to square one.

I agree that octane rating should be a good enough warrant not to even have this discussion but CALI gas has rating of 91 and supposedly is much worse to tune and has worse power gains compared to other 91 ???At least that's what I gathered from all the tuning threads. The fact is, chemical composition, vapor pressure, O2 content is different for winter gas. I think we all experience little bit lower milage on winter gas. It might be due to higher O2 concentration per volume of air in cold weather in which case tune would add fuel to compensate. Theory #2 - maybe winter gas is in fact more oxyganated hence ecu needs to run little bit richer mixture? I don't know, that's why I am here and that's what this whole thread is all about. Maybe octane rating falls within some tolerance and is a non issue on 99% of the cars but could be an issue on tightly tuned turbocharged cars. Maybe that's why Subaru map is so pathetic to compensate for all that. So who again has simplistic and narrow view of the issue. You think Octane rating is all there is and I am showing some article suggesting otherwise and I am the one who has simplistic and narrow view of the problem? It's hard to stay humble when someone fails so dramatically to comprehend basic logic and tells you that you are the one that is narrow minded, don't you think?
Last but not least I am sorry for raising this question in November. I shouldn't be so narrow minded. I should make a note to ask this question in he spring so it's more relevant. You are right, talking about differences in summer/winter fuel and how it affects tune should be restricted to spring time only.

fishbone 11-15-2012 03:38 PM

In your op you said "I was tunning my car". To us that means you yourself were tuning it.
There are a lot of us here that do self-tuning and also have help from tuners and that's exactly how your statement was construed.

You wanted the straight answer and we gave it to you.
I merely attempted to explain a bit of the why behind it.
Octane or gas is not the only factor and that's why I called you narrow minded.
I addressed the reason why the car SHOULD be just fine in the summer as well.
You dismissed that on the basis that I was off-topic and wasn't talking about the chemical make-up of gas.
You wanted an answer relating to gas but the answer as to why the car should be fine in the summer doesn't solely rest into what's up with the gas.
It also depends on environmental factors.
California suffers from quality control which means you don't always get what you pay for. The reason the Cobb ACN map is there is to give extra security.
The reason the compensating table is there is due to the simple fact that yes, the car runs safer in the winter and is prone to knock in the summer because of the difference in gas, sure, but more importantly, much higher intake temps and combustion temps, air density etc. Despite what you think this is a clever and safe approach. It's there in the stock tune and is there in most if not all off-the-shelf tunes. So I am not entirely sure why you would say the Subaru map is "so pathetic to compensate".
Zeroing out that table, in effect making it so that the car does NOT pull any timing in response to the likelyhood that it will knock during summer is each tuner's choice.
Take my example. We tuned the car also in spring just like you, also not sure on what gas blend. I am not confident all the pumps switched to the summer blend.
Summer came. Car ran fine. Gave back some timing. Winter came. Knocked. The car added back too much timing. Retuned and we found a nice balance between the two.
Here is another short answer.
If your tuner can't give you a map that runs safe both winter and summer, get another tuner.

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