91 or 93 Octane Stage II Tune - Not Sure Which to Choose

**cjw** · 12-18-2015 08:08 AM

Figured I'd ask since I'm fairly new.

Unitronic Stage 2 runs a single octane tune (93) and says it will work fine on 91. I was talking with EPL and they prefer the 93 tune as well, even if running on 91 on occasion. I have pretty decent access to 94 in my city, but I don't want to be a slave to it and definitely not during winter and also could be tough to find on any road trips. Don't want to feel like I'm handcuffed when I'm running a tank of 91, especially on a hotter day in summer.

Does anyone have an input on this?

**Thurston** · 12-18-2015 08:10 AM

I actually have had this same question going back and forth in my mind as well.. good question.

**justr0** · 12-18-2015 08:17 AM

I got the APR Stage II 93 tune for a similar reason since I have easy access to 93 in my state, but when I take road trips, the tune can handle 91 without a problem. Now if only APR would release EMCS for the B8.5, this wouldn't be a problem worth a thought ...*sigh*

Sent from my Nexus 6P using Tapatalk

**doug97gxe** · 12-18-2015 08:18 AM

if you're always filling up with 91 then be safe and get a 91 tune

**bhvrdr** · 12-18-2015 08:37 AM

Try and get people to post logs of their timing. If the companies 91 octane tune has some headroom in it (ie, is aggressive/has knock correction going on) than you wouldnt need their 93 octane program to benefit from using 94. At the same time, if their 93 octane program had just as much headroom (was just as aggressive) than running it on 91 octane could cause excessive timing retard and bleed boost and you'd be seeing less power using their 93 octane program than you would using a more properly timed 91 octane program.

And then there is the other side. If their 91 octane program is pretty conservative (perhaps takes into account crappy winter blend 91) then you wouldnt be getting any performance benefit filling with 94 octane on that program and you'd be losing out on the power. If their 93 octane program was equally conservative than you'd get the performance benefit from it using the 94 octane and would likely suffer no additional loss using the 91 octane fuel with it either.

The only way to know which is the case is to ask someone with your same ECU (b8 versus 2013 versus 2014/2015) to log the timing and knock correction.

Mike

**cjw** · 12-18-2015 08:47 AM

I'm cool with that, but I don't think we'd build up a database on logs that quickly. Also, as indicated, Unitronic only offers 1 tune and EPL was leading me to the 93 tune, even when I mentioned I'd probably run 91 40-50% of the time. I'm assuming (trusting/hoping) that the people making the tunes are confident and correct in their recommendations.

**SteveYem** · 12-18-2015 09:15 AM

Originally Posted by cjw

I'm cool with that, but I don't think we'd build up a database on logs that quickly. Also, as indicated, Unitronic only offers 1 tune and EPL was leading me to the 93 tune, even when I mentioned I'd probably run 91 40-50% of the time. I'm assuming (trusting/hoping) that the people making the tunes are confident and correct in their recommendations.

I asked the same question of EPL and the response was (paraphrasing) that the tune is optimized for the specified fuel type, but is safe in 'street conditions' running on any type of fuel that can be found in a typical gas station. As an extreme case, even if you were to use 89 octane you could still safely merge and pass on the highway.

My takeaway is that it is ideal to use the specified fuel type, but you can safely use lower octane ratings as long as you are not hammering on the engine.

**RynoS4** · 12-18-2015 09:40 AM

Go with the 93oct tune man, ive driven all over AB and BC and have yet to be stuck putting 91oct because I could not locate 94oct. Western Canada has stepped up their 94 oct game lol.

**=Law=** · 12-18-2015 12:15 PM

I'm Uni Stage 2. I have on occasion had to fill up with 91, and haven't noticed any adverse effects. Go for 93 and don't leave power on the table.

**moose_head** · 12-18-2015 12:32 PM

GIAC also apparently uses a single tune that self-adapts to 93 or 91, they don't even give out a 91 tune anymore. In Canada though they are much much (much) more expensive because of the USD to CAD exchange rate.

**waxxonMTL** · 12-18-2015 12:38 PM

just a thought.. maybe im opening a can of worms, but here in QUEBEC, we only have petro canada 94. Rumors is that it's a 91 gas filled with extra blend to make it like a94 octane. So lots of people are saying they prefer a true 91 octane like th eV-power from shell than run a 91 + additive.

Plus theres the thing about ; the 94 stay in the tank longer than a tank of 91 at the gas station.

When I had the skyline, my tuner always told me to just run 91 shell that it was producing just as good result as the 94. Me too, I was thinking if i should go 91 or 94. then the other question is.. will you really notice the 20whp / 15torque ( i think this it what is about right vs the 91 tune right ?) compared to the average 7 cent/ liter more you will pay over a 91 ?

**blbroo** · 12-18-2015 12:44 PM

I have the GIAC 93 and 100+ octane files on my car (B8 A4 to qualify). I've been running water meth on the race file and lost my spray signal the other day. Car still felt pretty strong just on 93 and had no misfires or detonation. Their program is really good at adapting, so if it can handle that big of a difference, I would think running 91 on a 93 file won't damage your car. Each tune just moves the timing range farther up from stock, with the stock tunes being really conservative to cover really poor gas and air quality conditions. For example, I would expect problems if I ran 87 octane on a 105 degree day at high altitude.

Some A4 owners were seeing issues with another tuners file at high altitude / warm temps this summer.

Also as a caveat, it was 42 the other morning when I was running the race file on 93 and I have a much better intercooler on than stock.

Hope this rambling helps.

**MrFunk** · 12-18-2015 12:45 PM

Running of 91 fuel on a 93 tune is fine. I don't think it won't perform as good as a 91 tune with 91 fuel though (and vice versa)... if you have access to 93 more often go with the 93 tune.

**Tony@EPL** · 12-18-2015 12:48 PM

Originally Posted by MrFunk

Running of 91 fuel on a 93 tune is fine. I don't think it won't perform as good as a 91 tune with 91 fuel though (and vice versa)... if you have access to 93 more often go with the 93 tune.

I like this answer, pretty much exactly how I would respond.. the only thing I will add is this, CA 91 can NOT be run on a 93 file.