Highest octane we can run without a tune

[hozer]

Built an RB26 that made 800whp. That qualify me to talk on octanes?

My only question is why you'd put 93 octane in your Bronco?

4 reasons to ever hit a button over 87 a the pump.

• You're getting paid to compete in said vehicle
• You bought a sports car with 400+ ponies or for some reason heavily modified a giant box to go fast
• You want to flex on the poors in anonymous internet forums
• It makes you feel better

Wasting your cash otherwise

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[TroutTrooper]

Citation needed. I was running with with an engine monitor and the engine management had no problem adjusting to E30 and made quite a bit more power.

It wasn't lean, it wasn't even close to lean. That said, I am not advising anyone to do anything regarding E85, that's up to anyone who wants to try it. When I was stuck behind enemy lines in California, the 91 Octane pump gas was absolutely horrible, I used to either go to Willow Springs to gas up or add a few gallons Toulene to bump the octane (both better options than E85, if you want to avoid the pitfalls of Ethanol). One legitimate danger of E85 is the need for more frequent oil changes, that is a fact. You don't want to run E85 and not be on top of maintenance, period.

I did notice that my local gas station is selling unleaded 100 octane sunoco 5 gallon buckets. So maybe I will run her down on fuel, load up the Ford performance tune, and put 5 or 10 gallons of real race gas in the Bronco (which has a higher octane than E85).

Now, who here has made more than 300 HP/liter at the wheel on a turbo engine they tuned?

So uh.... I'm gonna be honest. Might've had enough barley pops to not notice which forum I was on and that platform definitely doesn't have the OAR system an ecoboost has...

I still don't know if telling someone asking fuel questions equivalent to "what oil should I run?" to start experimenting with ethanol is great advice. Nothing wrong with not knowing, but I'd say more knowledge is necessary before someone hops in that boat.

 

[mpeugeot]

Rotary engines don't count LOL just kidding I couldn't resist

Actually, this was a 2 liter Honda motor (640 at the wheel). Won it's class at the NOPI nationals in 2002. Only 20 years ago... LOL

 

[mpeugeot]

Better yet who has made 300 ft/lbs of torque per liter on a turbo engine they tuned.

Wait, Gas or Diesel???

If you are talking 300 Ft/lbs per liter on gas, well, I can safely say: nope, not even close. That would be savage.

If we are talking diesel, maybe, I would have to find and look at some of my old dyno sheets. I still don't think that I managed that, maybe more on the order of 200-250 ft/lbs per liter.

Now, blown top fuel would get you there. I have friends who have done that, but that gets more expensive than I can afford.

 

[JohnnyBronco]

You will receive absolutely no benefit on a stock tune running over 93 pump gas. As a matter of fact, there's an argument to be made that you'd possibly make less power on a higher octane fuel because it is less energy dense, hence its higher resistance to pre-detonation/knock. Do NOT listen to anyone advising you to run higher ethanol content fuels without supporting mods and a tune. Yes, it might technically make a bit more power, but not safely. It takes more ethanol based fuel to maintain a stoichiometric air:fuel ratio than it does with gasoline. "Lean is mean."

Not to mention the Bronco is not factory authorized for any alcohol content above 10%. If your engine goes south on flex fuel (E85) and Ford finds even a drop of it in your tank forget about warranty.

But the real difference we may be ignoring is that aviation gas may contain lead which is good for the engine but bad for people near the airport.

 

[KABQ]

Let's try to actually answer your question. The ECU will advance timing (good for power to a point) until it detects pre-ignition, at which point it will retard timing until it thinks it's safe (bad for power). That's why these engines can safely run 87 octane but DO make more power on 93. If you run higher octane fuel, the ECU *may* be able to advance timing slightly, but since it's designed for 93 I doubt it would be significant.

Once you start making mods, as you've done, and especially start adding boost like it sounds like you are going to do soon, higher octane will help. But ONLY if you tune for it. So the short answer is you can run 105 safely, but you won't see much benefit unless the ECU "knows" it can safely advance timing and utilize more boost. The long answer is you're going have to spend a lot of time on the dyno with someone who knows what they're doing behind a laptop to take advantage of race gas.

 

[Laminar]

As a matter of fact, there's an argument to be made that you'd possibly make less power on a higher octane fuel because it is less energy dense, hence its higher resistance to pre-detonation/knock.

[citation needed]

I've never seen a reputable source claim 91/93 octane E0 has lower energy density than 87 octane E0.

octane rating is the resistance to burn with the higher the rating the harder to burn. You want to run the lowest octane you can without pre ignition to get the most use/ performance generally.

Octane is the resistance to ignition - it's less likely to spontaneously ignite. Once ignition is initiated, the characteristics are basically the same.

Not to mention the Bronco is not factory authorized for any alcohol content above 10%.

15%

Do not use:

• Diesel fuel.
• Fuels containing kerosene or paraffin.
• Fuel containing more than 15% ethanol or E85 fuel.
• Fuels containing methanol.
• Fuels containing metallic-based additives, including manganese-based compounds.
• Fuels containing the octane booster additive, methylcyclopentadienyl manganese tricarbonyl (MMT).
• Leaded fuel, using leaded fuel is prohibited by law.

 

[Laminar]

but since it's designed for 93 I doubt it would be significant.

What do you mean that it's "designed for 93"?

 

[TroutTrooper]

[citation needed]

I've never seen a reputable source claim 91/93 octane E0 has lower energy density than 87 octane E0.

Left out a word! I was talking about ethanol blends. Used to run into stations basically selling E0 87 blended up to E10 as 93, but I don't know if that's much of an issue anymore.

 

[KABQ]

What do you mean that it's "designed for 93"?

The factory tune is designed to run US pump gas, which typically tops out at 93 octane. It can also safely run on lower octane levels (down to 87 per Ford) by retarding timing to prevent pre-ignition.

 

[Laminar]

The factory tune is designed to run US pump gas, which typically tops out at 93 octane.

But what do you think that means, technically? In no possible situation can the ECU take advantage of any higher knock resistance? In no other elevation or ambient temperature or engine load can the ECU use any higher octane than 93?

 

[KABQ]

But what do you think that means, technically? In no possible situation can the ECU take advantage of any higher knock resistance? In no other elevation or ambient temperature or engine load can the ECU use any higher octane than 93?

You're right, there very well may be situations where the ECU can take advantage of higher octane, particularly in situations with very high IATs like you mention (high and hot with a heat soaked intercooler).

 

[Silence]

Built an RB26 that made 800whp. That qualify me to talk on octanes?

My only question is why you'd put 93 octane in your Bronco?

4 reasons to ever hit a button over 87 a the pump.

• You're getting paid to compete in said vehicle
• You bought a sports car with 400+ ponies or for some reason heavily modified a giant box to go fast
• You want to flex on the poors in anonymous internet forums
• It makes you feel better

Wasting your cash otherwise

Really flexing hard with that extra $5/tank for premium..

 

[hozer]

Really flexing hard with that extra $5/tank for premium..

The avocado toast of car enthusiasts

 

[Silence]

The avocado toast of car enthusiasts

*side of avocado. Add the toast for an extra $10

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