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Old 10-12-2011, 11:35 PM   #1
arcmpower
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Default stage 2 93 octane is bad for our cars????

I had a 07 sti running AP Stage 2 OTS 93 octane map for 3 years without any problem before I sold it for the 2011 sti with the same stage 2 setup. When I visited a local subaru specialist the other day, he told me to ditch the 93 octane map and use 91 instead (we have 93 octane gas sold here). He said the timing is too aggressive on the 93 map and I can continue to buy 93 gas using the 91 map to be on the safe side.

However, when I read the footnotes about the 91 map, Cobb said not to use 91 map if the gas is 93 or it will create boost creep and destroy the engine...

Any idea???? Should I change it to 91 to be safe? I never heard about such thing, now I am concerned.
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Old 10-12-2011, 11:37 PM   #2
scooby24
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It's an option for safety, but if you datalog and you're not seeing knock, running 93 won't be a problem. I log a lot on 93, never saw WOT knock except low RPM around boost threshold. Knock learning in that area of the map was never more than -1.4.
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Old 10-12-2011, 11:57 PM   #3
arcmpower
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I never learned how to read those log, so basically how can I tell if there is an unwanted knock and in what speed or rpm or gear should I look for?
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Old 10-13-2011, 09:37 AM   #4
Cobb Tuning
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Quote:
Originally Posted by arcmpower View Post
I had a 07 sti running AP Stage 2 OTS 93 octane map for 3 years without any problem before I sold it for the 2011 sti with the same stage 2 setup. When I visited a local subaru specialist the other day, he told me to ditch the 93 octane map and use 91 instead (we have 93 octane gas sold here). He said the timing is too aggressive on the 93 map and I can continue to buy 93 gas using the 91 map to be on the safe side.

However, when I read the footnotes about the 91 map, Cobb said not to use 91 map if the gas is 93 or it will create boost creep and destroy the engine...

Any idea???? Should I change it to 91 to be safe? I never heard about such thing, now I am concerned.
I'm curious where you are reading in our map notes that using 93 octane with a 91 map will cause boost creep?

You can certainly use the 91 octane map with 93 octane gas - this would be a more conservative approach if you feel it necessary.

Bill
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Old 10-13-2011, 12:14 PM   #5
arcmpower
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Originally Posted by Cobb Tuning View Post
I'm curious where you are reading in our map notes that using 93 octane with a 91 map will cause boost creep?

You can certainly use the 91 octane map with 93 octane gas - this would be a more conservative approach if you feel it necessary.

Bill

I mis-read it, it was addressing the high-flow cat and not to use stage 1 map.

So if I really want to use 93 stage 2 map on 2011 sti, what are some symptoms or data do I have to look for? My current set up is invidia catted turboback and AEM intake. Would a LWG Stage 2 93 be as conservative?

Thank you for your advice.
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Old 10-13-2011, 12:28 PM   #6
WRXt4cy
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The octane rating of fuel would have nothing to do with boost creep. You might have seen something about using a catless DP with a map meant for a catted DP. The 08+'s seem to be more susceptible to boost creep with a catless DP than older STi's. I run a catless invida on my car and I see a little bit of boost creep in 4th, 5th & 6th if if I come into boost at lower rpms. It got better when I switched to a Grimmspeed EBCS but its still there. To avoid it I just downshift if I need to get on it.

The symptoms of boost creep is simply that your car wont hold its target boost clear through the rpm range. There will come a point when the wastegate can't flow enough exhaust and the lack of back pressure in the downpipe allows the compressor to spin up faster. When this happens you'll see your boost "creep" up over the target. With your catted downpipe you probably have enough back pressure to keep from getting boost creep.

As others said, running a 91 map with 93 octane just gives you a better safety margin.
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Old 10-13-2011, 12:39 PM   #7
Cobb Tuning
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Originally Posted by arcmpower View Post
I mis-read it, it was addressing the high-flow cat and not to use stage 1 map.

So if I really want to use 93 stage 2 map on 2011 sti, what are some symptoms or data do I have to look for? My current set up is invidia catted turboback and AEM intake. Would a LWG Stage 2 93 be as conservative?

Thank you for your advice.
You would need to data log with the AP in order to determine if there are any issues. You can post your log here and we can take a look at it. A good run would be to put the car under some load. If you can so safely, try a 3rd gear wide open throttle (WOT) run from 2000 RPM on up (before redline).

Bill
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