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Has anyone tried or does anyone know if you can run the Sunoco GTplus 104 unleaded racing fuel in a NA Elise without causing damage? Also, would it significantly increase your horsepower?
 

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Don't waste your money. I dynoed the same car with 110 octane and 87 octane, surprisingly the 87 octane has higher horsepower.
 

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Has anyone tried or does anyone know if you can run the Sunoco GTplus 104 unleaded racing fuel in a NA Elise without causing damage? Also, would it significantly increase your horsepower?
You could actually lose HP, search google on does higher octane = higher hp.
You can run higher octane but you will be wasting a lot of money unless your engine is set up to use the fuel correctly. The stock Elise is supposed to use and tuned to use 91 per the Lotus owners manual. There would be no reason to use higher unless possibly you are getting some pinging, in which case you should probably use the cash you are going to spend on the fuel to go to a dealer to get your engine fixed!
 

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Your car will yield the biggest gains with the lowest octane gas you can run without pinging. (In case of the Lotus, I suggest not using anything but the recommended 91 oct, maybe 93 on a hot day on the track.)
 

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I ran the 104 blended roughly 1:3 with the 91. No ill effects that I could tell. No better, but no ill effects.

xtn
 

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On a stockish N/A engine, you won't see any benefit over 93 on the street or track.

On a FI engine, 100+ is generally mandatory in track environments to prevent detonation. On the street, 93 is fine.
 

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Don't waste your money. I dynoed the same car with 110 octane and 87 octane, surprisingly the 87 octane has higher horsepower.
Not surprising since race fuel is formulated to burn slower and cooler than ordinary pump gas.
As others have said, performance gains can only be realized if engine and ECU are modified to make best use of the fuel's characteristics.
 

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Don't waste your money. I dynoed the same car with 110 octane and 87 octane, surprisingly the 87 octane has higher horsepower.
True. Higher octane fuel has a lower energy content. Higher octane fuel doesn't produce more power, it prevents detonation (or at least helps defer it). It will also decrease fuel economy (again, due to the lower energy content).

Edit: I guess I need to learn to type faster. :D
 

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If you're in a track environment, always good to have more octane in the tank to prevent detonation as previously said. Even 50/50 mix of 100 and pump gas is good for you! On normal street driving, you won't notice difference with race gas..
 

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It most certainly does not. The octane rating of a fuel pertains to its relative stability and resistance to detonation.
Sunoco 94 at the Barber Motorsports Park was 10c/gallon less than the street price for cheap gas around Birmingham at the time of LOG this year. Car ran strong on 94, cool (highest observed temp was 203), and got passably good mileage (~13 MPG) for 107.7 miles of purely on-track driving. This is with a Katana and Charliex tune.
 

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It most certainly does not. The octane rating of a fuel pertains to its relative stability and resistance to detonation.
Your last sentence is true. But it also does have a lower energy content. Not directly due to its octane rating but a result of getting the octane rating. Most, if not all, additives that provide the higher octane have a lower energy content, thus lowering the overall energy content.
 

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Well i am glad to hear this recommendation of higher octane for the track. At my first event a few weeks ago I was below half tank and worried about fuel starve. Only gas station around was on the track so I filled up 2 gallons of 100 (my tank was half full with 93) I wasn't concerned with any power changes, just was worried I was hurting the engine, glad to hear i was in fact protecting it.
 

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...about twenty years ago, i occasionally ran my '81 mercury capri straight-six on 93 octane and noticed considerably better fuel economy versus 87 octane unleaded...
 

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But it also does have a lower energy content. Not directly due to its octane rating but a result of getting the octane rating.
No. It doesn't. Gasoline contains around 135 MJ/Gal of energy. Doesn't matter if it's 87 octane, or 93 octane, or 478 octane. If it meets the chemical definition of "gasoline", burning a gallon of it produces the same amount of energy. Doesn't matter if you're reaching a given octane by use of aromatic hydrocarbons, or tetraethyl lead, or magic bean dust.

If you run a normal-compression naturally aspirated engine with reasonable timing advance on 87 octane, and then on 100 octane, it's going to make the same amount of power, all things being equal.

Likewise, if you run a forced induction engine with a lot of timing on 100 octane, it'll make the same amount of power as it does on 87 octane. Unfortunately, it will also blow up due to the much greater propensity for the lower octane fuel to pre-ignite.

When you start mixing alcohol into gasoline, among other crap, in significant quantities, yes, the energy content of the fuel goes down. However, this is not a function of octane of the gasoline. It's a function of dumping something other than gasoline into the formula. Anything you buy as a pre-mixed gasoline or gasohol product, regardless of the octane rating, is going to produce the same amount of energy.

Hence, buying 93 octane or 100 octane from a commercial pump is not going to give you a fuel with "less energy" than 87 from the same pump. Period. Full stop.

In fact, if 10% ethanol is in common use in pump gas where you live, buying 100+ octane at a race track will generally result in more power as it's straight gasoline without any alcohol in it.
 

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Simba I think he was suggesting that you aren't getting 100% gasoline. You're getting (just guessing here) 98% gasoline and 2% octane boosting additives. I think he's further suggesting that the 2% of additives don't have the 135MJ/gal so your total tank full averages a bit less.

You sound like you know your stuff, so I'm not arguing. Just didn't seem like his point was made clearly, and it is possible to read your post as not addressing that point. Please clarify if you will because I would like to know.

xtn
 

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Simba I think he was suggesting that you aren't getting 100% gasoline. You're getting (just guessing here) 98% gasoline and 2% octane boosting additives. I think he's further suggesting that the 2% of additives don't have the 135MJ/gal so your total tank full averages a bit less.
That's true, however the suggestion I took issue with is that pump gas is subject to "more stuff" being put into it in order to raise the octane, as you might when mixing your own race gas using significant volumes of toluene or xylene.

This is not how pump gas blending works.

All commonly available gasoline that is sold today in a retail environment (e.g. not a race track) is subject to extremely strict additive and hydrocarbon regulations. All gasoline, regardless of its final octane rating, is produced at an octane rating of around 70 when it is distilled from oil. Various processes are taken to raise that octane to around 90, such as isomerization and other catalyst-based reactions used to manipulate the carbon structures in the fuel-- in effect "re-arranging" the structure of the molecules to be something slightly different (and in this context, more stable).

It is at that point that the various blending agents and emissions packages (and ethanol distilling) take place. The amount of these additives is generally quite insignificant, less than 1% by volume, and they do not (excluding ethanol) dramatically affect the energy content of a given fuel at a given octane. While there are blending agents and aromatic hydrocarbons added to 91-93 octane fuel, these things are also added to lower grades, albeit in different formulations.

Put simply, the original suggestion was that you should not buy higher octane pump fuel (unless you need it to prevent detonation) because it contains less energy than lower octane pump fuels. This is not the case and is misleading. While you may be able to document a tiny difference in the heating energy content in a lab environment, running 87 vs. 93 octane in an engine without any specific high octane requirement will not result in more or less power. It won't register less power on a dynamometer, nor will you "feel" any difference.

What you will feel is a higher octane fuel allowing an engine to run more timing. This is why many people experience their car "feeling" faster on higher octane fuel. It's because the ECU isn't pulling timing as a result of knock on lower octane fuel, and hence is producing more power. And, it is entirely possible to run into slight cases of detonation on 87/89 octane grades even on a normal naturally aspirated engine with a compression ratio north of 9:1, which these days is just about all of them.

Now, specific to Lotus and other manufacturers who specify high octane fuel for their engines, they do this for a reason. Specific to the Elise/Exige, even in stock, naturally aspirated form, these are extremely high compression engines compared to most. The 2ZZ runs 11.5:1. That requires 91 octane at the minimum to prevent detonation under certain circumstances, like heat soak on a hot day in traffic. Once you add forced induction to an already high static compression, the fuel requirements go up even more for safe operation.

Here's a fun exercise: Hook up a good OBD reader to your car, one that can display ignition timing. Or, use a small data logger like a CarChip. Then, go drive around on a tank of 93 octane and note the timing advance. After which, run a few tanks of 89 octane (n/a only) and compare the timing advance. It will be less, in virtually all cases, as the ECU is detecting slight amounts of knock and pulling timing to prevent it. That means you're getting less power.
 
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