Toyota Tundra Forum

I posted this a few years ago and thought it might be worth reading for you inquisitive types. (I ended up having to give my Nephew some basic physic lessons that for some reason his High School education had skipped......................or he had slept through and he stopped playing with cars weighing less than his.)

Last night while I was out making my rounds, my 20 year old nephew called to ask me some questions about his 1976 Camaro I gave him when he graduated High school. (Yeah, uncle Squid is cool.)
Anyway, it seemed that as he put it some POS Honda ricer smoked him? So I asked him how the Honda could be a POS if he had lost? He ignored me as expected. (Sometimes Uncle Squid shows his age.)
What he was looking for was some information on how to make the venerable Chevy 350 a little more potent. As we were talking I noted some misconceptions he had concerning some very basic aspects of internal combustion engines that I thought I'd share with all of you.

Octane
Plain and simple, octane is simply a measure of fuel-detonation resistance.The higher the number, the less prone the fuel is to detonation.
Detonation is the un-uniform ignition of the air/fuel mixture in the combustion chamber. Normally, the combustion flame front originates from the spark center. When detonation occurs, the charge is lit at not only the spark center, but also from hot spots caused by build up from carbon deposits within the combustion chamber. This causes an uneven flame front, resulting in a sudden rise in combustion pressures, which can damage a piston on the power stroke.

What's even worse than detonation is what's called pre-ignition, which occurs when the air/fuel mixture (Charge) unintentionally lights off without a spark. This usually means the event occurs toward the end of the compression stroke when charge temperatures and pressures are still rising. With pre-ignition, the sudden change in charge pressure from premature ignition as the piston is still moving up is equivalent to taking a hammer and beating it on top of your pistons. The sound is very similar, just like a ping.

Higher octane fuels are especially helpful to boosted or high-compression performance engines, along with older engines. With boost or a high-compression ratio, the air-fuel charge is compressed to higher pressures, which makes it more susceptible to detonation. Older engines with carbon deposits built up in the combustion chamber also benefit from high-octane fuels as the added space occupied by the deposits also effectively increases the compression ratio.

Now this is where it gets fun.
Todays engines, like the VK56DE in our Titan, the Infinity QX56 and the 5.7L in the Tundra control detonation with knock sensors that retard the spark timing at the onset of knock. Retarding spark timing or richening the air/fuel mixture to reduce knock ultimately robs power. This is why an increase in octane increases horsepower. Since the engine's knock threshold is effectively raised with higher octane fuels, spark timing is not retarded. This allows combustion and charge expansion to occur so that more force is put into the power stroke. Bottom line: Higher octane fuel only helps you make more power if your engine is at the verge of detonation (whether you know it or not).

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Good Gawd that is one ugly Tundra.

lol...I'm still lost.

Sooooooooooooooooooo...should we add some race fuel to our 87 oct tonight at the track? hummmmm.... I guess if we were close to detonation......it would increase horse power?


Still no freaking high flow filter to be had. I'm ditching the OEM filter for the 1/4. I might suck up a dog...but hey its in the name of being FAST! lol

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Mine: 07 5.7 CM 4x4 SR5 Tundra White
MINE & His: 07 5.7 DC 4x4 TRD Tundra Radiant Red

Squid, I appreciate the info, that was cool! Chicks, I hope to heck there aren't too many dogs in your line of fire tonight.....lol Can't wait to see the times though!

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5.7 Slate Gray DC
4x2 w/Tow package
20" OEM Alloy wheels
Leather Buckets
Gatorhyde liner

You rock Chicks, go get em.

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2007 Tundra RC LB SR5 5.7L 4x4, Tekonsha Prodigy Brake Controller, JCW Side Bars, AMP BedStep, 12K+miles and no problems besides the tailgate beginning to fail.

If I'm going to go racing on Friday I'd empty the tank during the week and then I'd put 5 or 6 gallons of premium on the way to the track depending on how far I have to drive and how many runs I'm planning to make because fuel is weight and then because I'm a goof I'd bring 5 gallons more in a container because I'm sure to make more runs than planned and run out of gas.

There are off the shelf octane boosters but they work better for bikes where you can mix the concoction in a 5 gallon container, drain your gas tank and then refill with the race mix.

Man! Now I want to go racing.............................

I would like to add my own two cents to Squid's excellent octane coverage. If you want to get better gasoline mileage with the 5.7 L, running premium gas WILL give you better mileage if you don't lead foot, if you coast instead of hard brake to a stop and if you accelerate mildly instead of neck snap. The 10.2:1 compression ratio used in the engine is way above the 8:1 compression ratio of most of today's vehicles that can run on regular gasoline. With this high compression ratio, the spark timing is controlled by the Engine Control Module (computer) up to the detonation point. The point is detected by the (4) detonation sensors located between each cylinder pair at the firedeck level. The Owner's Manual and the Service Manuals say to use 87 octane OR HIGHER. What that means is, if you run higher octane, the ECM will keep advancing the spark plug firing until detonation is detected.
Here in Michigan, octane is commonly 87/89/93. I believe that the use of higher octane will allow advanced timing and a resultant higher mpg. Since I haven't had my Tundra long enough to do detailed mpg analysis, I do not know if straight 93 octane or a less expensive mixture of 89/93 octane will cause the timing to advance to maximize mileage. However, at some point the ECM will not allow spark plug firing to advance any further, even at 100 octane. You might want to experiment with this, after all, it 's your dime. So, if I haven't bored you silly, max POWER and max MILEAGE are available with the SAME fuel, but your driving habits are the most important factor in increasing mpg.
On another note, I bought the TOYOTA TUNDRA 2007 Technical Features Manual on Ebay, and found more easily understood information on the actual workings of the various features (engines, trans, drivelines, options, brakes etc) than in the set of 6 Toyota Tundra Service Manuals that I have. I am not the seller of the new Features Manual, but if you would like some GOOD info, for 2007 through 2009 Tundras, I highly recommend this book. The publication is actually for the technical people at a Toyota garage before the new models come out. It is well worth the $35-$45 for the manual and I see they are still available on Ebay.
The only feature I don't like on my Tundra is the CRUISE light. I would prefer it lit ONLY when I have cruise activated, not when it is just enabled. There is my two cents. DRAYKS