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Originally Posted by airbox1
nice job mnboxster. however, don't be discourage in using higher octane gasoline, steven choi. since boxster engines are high compression engines, they benefit from having higher octane gasoline. yes, it's true that higher octane gasoline doesn't directly "give" your car more horsepower, but it definitely indirectly effects how much horsepower your car is getting. in other words, with a higher octane gas, your chances of premature detonation decreases. therefore, with a performance enhancing chip, like the revo or giac, you can delay the timing beyond its normal parameters, thus, giving the engine more horsepower. again, please keep in mind that it only works if you have the chip and higher octane gas working in conjunction.
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Hi,
Thank you for your kind words. I think there are a couple problems with your arguements.
First, the Boxster
is a higher compression engine, but it benefits from Gas which has only so much of an Octane rating. Any more than this is not needed and you derive absolutely no benefit from it, although it usually costs you more.
Second, your car only gets it's power from releasing the Heat Potential of the Gas, that is, how much energy is released during combustion, and how efficient the engine and drivetrain is at using that energy. The most efficient IC engines on the market today only contribute about 25% of the energy released to actually turning the rear wheels. The rest is lost to mechanical inefficiencies and heat. There are no
chances of detonation as you suggest, either the detonation threshold has been reached, or it has not. Some things which can affect reaching this threshold are:
Ambient Temperature - Air (any Gas really) is heated when it is compressed. Roughly, the increase is 1°F for every 1 PSI of pressure. If you start with 70°F Ambient Air and compress it 100PSI, it's temp will increase to 170°F, but if you start with 100°F Ambient Air and compress it 100PSI, the resulting temp will be 200°F and so on. On very hot days, this can exceed the combustion threshold of the A/F mixture. Note, to simplify I used the example of 100PSI compression. In reality, most high compression Engines achieve cylinder pressures of 150PSI-190PSI, so you can see it can make a big difference.
Cooling System Efficiency The more efficient your cooling system, the less
leftover heat remains in the cylinder to heat up the incoming charge before the Piston compresses it. Similar to the example above.
Spark Plug Heat Range The Heat Rating of your Spark Plugs has NOTHING to do with how Hot a Plugs burns. It is a measure of how much heat the Plugs extract from the cylinder and pass through the head to be carried off by the coolant between cycles. The difference in one rating of the same type plugs (for example a
6 to a
7, or a
6 to a
5) is equal to about 70°C-100°C (158°F-212°F) of heat it can remove from the system. Again, the less heat retained in the cylinder, the lower the intake charge will be when compressed.
Most ECU's will compensate 1 or 2 points in Octane rating, but performance may decrease slightly (usually unnoticable unless at Top End or under extreme load) as the ECU switches to a less efficient MAP.
If you cannot find 93 Octane fuel in your area, there are a couple things you can do:
First, switch to a lower Heat Rated Plug (the Boxster is a '7' rated Plug, try switching to a '6')
Next, make sure your cooling system is in top order - no debris clogging the radiators and if in a temperate climate such as California, run a coolant mix of 60% water/40% Anti-freeze (water has greater Thermal Conductivity than Glycol), you'll still have plenty of anti-corrosion and lubrication protection, but you'll be removing more heat from the engine.
Finally, there are octane boosters. But, be careful with these OTC types. They will raise the Octane a few 0.1 points and they're usually sold in 12oz. containers for maybe $2.99 (that's equal to almost $32/gal. !!). The primary ingredient of these is Toluene (Octane Rating 117), mixed with some Dye and Light Oil.
You can buy Toluene from any Sherwin-Williams Paint store for approx. $4/gal. and make you own. Mixed 10% with 91 Octane Fuel will raise the Octane Rating to 93.4 Octane. Care must be taken when storing and handling Toluene as it is extremely flammable and somewhat toxic to breathe, but for little more than a gal. of fuel (which you'll be replacing with the Toluene) you can achieve the Octane Rating recommended. Adding amounts greater than 10% are not recommended because of excess wear and tear to the Fuel System, but 10% is just fine.
Here is the formula for making your own Octane Booster:
This is the basic formula to make your own octane booster. (128 oz = 1 gal):
100 oz of toulene for octane boost
25 oz of mineral spirits (cleaning agent)
3 oz of transmission fluid (lubricating agent)
Diesel fuel or kerosene can be substituted for mineral spirits and light turbine oil can be substituted for transmission fluid. Note, the final 2 ingrediants are also added to ordinary pump gas as well, so don't be shocked.
Hope this helps...
Happy Motoring!...Jim'99