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As the Title says, car likes 93, i can only get 91 here. Gonna go on a limb and say that the manual is going to say "dont add octane boosters". Is there that big of a difference between the two? (other than 2 octane :p ) My search-fu is weak and putting in "gas, 91 octane, 93 octane etc" didnt help. The car is basically stock. drop-in k/n filter and a borla exhaust for the sound. Should i look for a 91 octane tune when i do tune it?

Z
 

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91 is fine. The car will adjust itself. There shouldn't be a noticeable difference in performance.

Sent from my XT1650 using Tapatalk
 

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When you tune it just let the tuner know that its for 91 octane. I'm in California so I have the same problem, but there are two gas stations by my house with E85 so once I tune my car I'm gonna have a 91 octane tune and an E30 tune.
 

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As the Title says, car likes 93, i can only get 91 here. Gonna go on a limb and say that the manual is going to say "dont add octane boosters". Is there that big of a difference between the two? (other than 2 octane :p ) My search-fu is weak and putting in "gas, 91 octane, 93 octane etc" didnt help. The car is basically stock. drop-in k/n filter and a borla exhaust for the sound. Should i look for a 91 octane tune when i do tune it?

Z
If you tune it, then yes, look for a 91 octane tune. You are fine on 91 octane though. That is all I've been running. After one Strat tune revision my engine is running very healthy. Dyno'ed today at 246 hp/276 lb-ft at the wheels.
 

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91 octane is terrible, 93 is slightly better.

You will not reach MBT on pump fuels, period. Without the ability to substantially increase boost, the majority of your gains with this platform comes from adding ignition advance.


Direct comparison between 91 octane and racing unleaded fuel.


Racing gas concentrate added to 93


MS103 vs Racing Gas Concentrate

Butt Dyno's are not the answer, real dyno's are but track testing is cheaper.

The Tuning School test are important because the car has a supercharger, all they can tune is the air fuel ratio and ignition timing, which applies DIRECTLY to the Focus ST with the stock turbo, since there isn't much more to be had out of it.

Now you understand why people run E30/E40 tunes like I do. I will have a race gas tune here soon because I want to see the difference 1) and 2) it takes five gallons of gas+ethanol to make E40 while I can run 2-3 gallons of race gas for a little less weight.

It works out to about $30 more; $43 for five gallons of Trick 101 octane unleaded from the pump + E85 = $13.26

Race gas typically only requires a 10-20% change in air fuel ratio vs 30% for E85.
 

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If you are stock it doesn't really matter. You'll reach the torque targets on either so there isn't really a gain in power.

For tuning I would go for a 91 tune, especially if that is the max you have around there. If you are close to areas with 93 or e85 a switchable map would be nice for those times when you could take advantage of it.
 

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If you are stock it doesn't really matter. You'll reach the torque targets on either so there isn't really a gain in power.

For tuning I would go for a 91 tune, especially if that is the max you have around there. If you are close to areas with 93 or e85 a switchable map would be nice for those times when you could take advantage of it.
But he isn't stock... No way at his attitude on 91 octane would he make 246 hp stock. I made 220 hp on 91 octane completely stock near sea level (California). As I said the gains in this car will come from adding timing advance.

When you have a larger turbo like you did formerly then there's more to gain from increasing the boost as well.

There is much more to be gained from switching fuels or running water-methanol injection.
 

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But he isn't stock... No way at his attitude on 91 octane would he make 246 hp stock. I made 220 hp on 91 octane completely stock near sea level (California). As I said the gains in this car will come from adding timing advance.

When you have a larger turbo like you did formerly then there's more to gain from increasing the boost as well.

There is much more to be gained from switching fuels or running water-methanol injection.
OP isn't the one who dyno'd at 242hp and I agree with you there is no way you would get those numbers on 91 (Especially stock where the tune would of shut down way before then).

I also agree with you that there are quite decent power gains with alternative fuels or even 93. If it's available then go for the best you can get.

My point was if 91 is all that is readily available to him he should at least have a slot available for it. If his tuner doesn't provide multiple fuel slots then go for 91 (or a different tuner). If you tune solely for fuels not readily available to you (Race, e85 in areas without it, 93, etc) the daily drivability of the car becomes pretty limited. Either you need to stock up on fuel ahead of time or plan your routes carefully. Been there, done that when the e85 shops closed up around my house. It gets to be a huge pain.
 

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I've unfortunately run my WMI assuming it would work and it didn't = Pulled a ton of timing

When the nozzle is not big enough = Pulled a ton of timing

I've been caught once not able to get E85. I didn't run that day.

Too bad there's no real alternative to E85 despite only running 30-40%. I'm having a hard time getting hold of VP C-85 as I want to try mixing that with 91 to see if it's there's a gain to be had.

Actually there might be an alternative but at a price.

MS109e (which you'll find under watercraft) is the best unleaded fuel PERIOD. There's a video on You Tube done testing VP MS109 vs MS109e. Additional gains of 16 hp and 10 ft of torque were realized.


If you look at the difference in The Tuning School's video comparing MS109 against C-85, you can see how MS109E might compare favorably to pump E85. It will only need about a 15-20% enrichment adjustment vs automatic 30% with E85.


Meaning you could make almost as much power without going to an extra injector setup. You can find MS109E for around $77 for a 5 gallon pail. Yes it's expensive but how long would it take you to pay for any of the commercial extra injector setups?

Food for thought.
 

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"The car is basically stock."
Like I said, 92 is fine with 91 or 93 tune. If you are "Stage 1" you're basically still stock."

Better/safest bet would be to just use 91 octane fuel and use 91ots tune. Just monitor your OAR [Octane Adjusting Ratio].
 
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