Hi guys,
By chance i came across a business that sells home heating fuel and different octane level gasoline. I'm under the belief that race fuel is of no benefit to our car but i thought I'd ask all of you, because someone will give me a definitive answer whether or not 105 octane gas will make more power in the V8 motor. My guess is no, it can not increase the HP because of the engine software parameters being set for standard gas. Your thoughts please. Thanks

 

Anything more than 93 is a waste of money, and based on the distillation range may actually decrease power. If the engine were running 14:1 compression, of course you would benefit from 105 octane, but the AJ133 engine is only running a 9.5:1 compression ratio.

 

That is truly a gear head reply and i thank you Sir. I wish i had such knowledge with cars.

 

Octane us raised by additives to the gasoline which inhibits ignition so you do not get pre-ignition prior to the spark (ie, pinging).

In order to delay ignition some of the energy producing gasoline is replaced by these inhibitors.

Hence, the higher the octane, the lower the energy content of the gasoline.

To maximize energy you should run the lowest octane gas your car will run without pinging.

This assumes your car is not programmed to compensate for lower octane gasoline. My understanding is the 2.0 turbo charged engine in the Pontiac Solstice GXP/Saturn Sky Redline will run any octane gasoline but is programmed to alter the timing to lower the compression ratio if regular gasoline is used, to prevent pinging.

 

It may (probably) retards timing, but it doesn't do squat to compression.

 

Octane rating of gasoline has nothing to do with 'pre-ignition' or 'pinging', it's 'detonation' or 'knock'. The two terms are not interchangeable, nor are the different phenomena in any way similar.

Pre-ignition is premature but otherwise normal 'burning' of the fuel, detonation is 'uncontrolled explosion'. Detonation occurs after normal ignition of the fuel, not before.

The various components and additives in gasoline act to raise or lower the tendency to detonate. The actual variation in energy content (BTUs) from the lowest to highest octane fuel is insignificant.

Jaguar designed and certified the engines in N.Am. spec cars to produce full rated power on 91AKI fuel. Euro cars are spec'd to produce full rated power on 95RON fuel.

Using fuel lower than recommended may (or may not) result in lower power output and increased consumption. Such effects would be the result of the lower octane fuel not having the capability of withstanding the tendency to detonate. The engine knock sensor(s) would detect the event and retard the ignition timing until such time as the detonation is under control. Retarded ignition timing causes the engine to reduce it's combustion efficiency, hence reduced power and increased fuel consumption.

As to whether using higher octane fuel than recommended would increase power or not is possible, but unlikely. Several things would need to occur but primarily:

Is the engine subject to detonation on it's current rated fuel? If no, then there's no detonation to eliminate and no benefits to be had. If yes, will the engine software allow the ignition timing to be advanced?

If no, then using higher octane fuel is of no benefit. If yes, does the current ignition advance curve programming represent the optimum for power output and efficiency?

If yes, then more ignition advance would be counterproductive. If no, then more ignition advance would produce more power and reduce consumption.

Research on the 4.2L V8s used in the predecessors to the F-type indicated that using anything higher than 91AKI/95RON was of no benefit. As to whether the same results would apply to an F-type, I have no idea.

The last time I looked at pump prices for 105 AKI fuel, they were around $8-10 USD per gallon. Anybody willing to experiment?

 

Correct.

 

Not quite true. It depends entirely on what blend components are used to raise the octane. Gasoline containing ethanol, for example, can reduce the thermal content by as much as 3%, and if the distillation range of all the blend components is out of balance as a result of top loading with the high octane components, the combustion will perform unequally over the entirety of the rpm range, sacrificing power.

 

True enough, but that's bringing in another variable other than just octane rating. Using your example, it can be said that 87AKI E10 gas has 3% less energy content than 91AKI pure gas or conversly that 91AKI E10 has 3% less energy than 87AKI pure gas.

I chose to compare apples to apples by presuming that two fuels were otherwise identical other than octane rating.

 

Using 105 "may" "possibly" burn valves if the conditions exist to do it....btdt...looong ago...

 

Old myth that never made any sense.

 

Fair enough!

 

+1.

 

From here -

https://www.bellperformance.com/blog...Octane-Ratings

 

Ouch. I'd choose a more credible source of info than a snake oil marketing site.

 

 

The reverse of this was a recent Jalopnik article: deadspin-quote-carrot-aligned-w-bgr-2<\/title><path d="M10,3.5l3-3,3,3Z" style="fill:%23fff;stroke:%23fff"/><path d="M0,3.5H10l3-3,3,3H26" style="fill:none;stroke:%231b3a4d"/><\/svg>')}.f_branding_on.blog-group-deadspin .editor-inner.post-content .pu.

As an owner of one those who will likely be shortly upgrading to an F-Type, if low octane fuel is used an LNF will alter its timing a bit to compensate, but at less power to the rear wheels. The kicker was that the default programming would "learn down" if you used any mods or extra high octane fuel without first wiping the stock tune.

 

I dyno'ed with 91 octane and 100 octane, zero difference. Equal performance. The only difference is that the 100 octane was more than 2x more expensive.

 

Thanks for that info!

 

Maybe I was dreaming when a few decades ago when I had a small 4 cylinder Toyota (leaded gas type). I had the engine rebuilt a bit and I then tried using 105 av leaded gas to naively boost the power a bit more and used a bit more than i should have in the tank. Started to run rough, took it back to the shop and the mech. found a couple of burnt valves which were determined from using too much av gas. I stopped doing that since I didn't want to go thru that again.