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What octane gas do you use? (The Mother thread)

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Old 02-13-12, 08:04 PM   #166
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Thunderhill is where I learned this. Just blindly repeating what I've learned from people that wrench and tune for a living and build winning race cars. Granted, these were FI cars.

http://www.i-club.com/forums/bay-are...5/#post2649597

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Old 02-13-12, 09:12 PM   #167
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My car runs the exact same on 87 or 91, not even a bit of difference. Mileage doesn't change. So i figure why throw an extra 30 cents a gallon at it for no benefit?

high octane is just a bunch of hype on most N/A cars newer than the 70's, lol.
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Old 02-14-12, 04:02 AM   #168
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What do you guys think of this article?

http://www.edmunds.com/fuel-economy/...d-premium.html

After reading this and many others that say the same thing I believe the only difference between regular and premium is performance HP/torque. Especially, that both premium and regular have the same level of detergents.

In general there should not be any knocking running regular if the knock sensor is doing its job and the computer just pulls the timing back slightly.

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Old 02-14-12, 07:18 AM   #169
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Knock sensors will "protect" the engine by making ECU pull timing. I personally want as much timing as my car can stand given the conditions, efficiency = power. Our v8s are way overbuilt with 6 mains, forged pistons and strong rods, so chances are you won't easily put a hole in the piston or spin a bearing like you will, say, in a turbo-charged Subaru. Is premium required? Yes. Will the car still run on 87? Yes, it'll probably run and last for a while, especially at higher elevation. Would I run 87 personally? Absolutely not. High octane is not hype, engines are built with specific octane in mind.

Are there logging tools available for the early LS?

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Old 02-14-12, 07:54 AM   #170
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I have always (18 years) run 87 in all eleven of my LS400's, without any problems.. but I dont race or drive over 120.
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Old 02-14-12, 08:31 AM   #171
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You don't have to race or drive fast, all it takes is driving up a hill on a hot day. I will stop now as hammering at a mountain will not accomplish much. I just don't like seeing wrong thing suggested backed up by "I do this and it's fine", it may work for you but others may not be as lucky.

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Old 02-14-12, 09:24 AM   #172
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Quote:
Originally Posted by BrettJacks View Post
My car runs the exact same on 87 or 91, not even a bit of difference. Mileage doesn't change. So i figure why throw an extra 30 cents a gallon at it for no benefit?

high octane is just a bunch of hype on most N/A cars newer than the 70's, lol.
I disagree entirely about "A bunch of hype".

I would tend to believe that the reason your performance doesn't change with different octanes, is because the elevation where you are at is ideal for combustion.
Whereas, where we are closer to sea level, it makes a huge difference.

I am a certified motorcycle/marine technician. I can tell you that predetonation due to heat/low octane will tear apart the top end of an engine in short order.
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Old 02-14-12, 09:47 AM   #173
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Default 1998 ls400

93 octane all day!!
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Old 02-14-12, 09:50 AM   #174
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If some of you don't really know what will happen, as piston goes up squeezing the mixture it may ignite from heat before the spark plug fires. So, you have combustion as the piston is still on its way up. That energy will go somewhere and absolutely will cause damage to pistons and rod bearings.

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Old 02-14-12, 09:59 AM   #175
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There is always advanced timing. That means that combustion begins with the piston on the way up. What happens with lower octane is that pockets of mixture detonoate due to the increase in pressure instead of igniting as the flame front reaches them. If timing is reduced then pressure is reduced. This is why if you have a knock sensor it can save an engine from bad gas or allow you to run low octane fuel at the cost of performance. It is much more nuanced than this, but I think you knew there was more to it anyway.

BTW: Does the LS have a knock sensor? I THINK not.
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Old 02-14-12, 11:14 AM   #176
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[QUOTE=BTW: Does the LS have a knock sensor? I THINK not.[/QUOTE]

then think again, they do.
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Old 02-14-12, 12:46 PM   #177
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Something interesting from another thread... It was mentioned Toyota uses some of the same engines in both brands (Toyota & Lexus) but recommends premium for Lexus and regular for Toyota. There are other articles comparing the use of premium vs regular and the engines most effected are turbocharged. Did any of the engines suffer from predetonation? No. There was just a loss of power. With advanced technology and computer controlled timing knocking should be a thing of the past. The article I linked above is pretty insightful.

It seems pretty definitive that higher octane fuels will lead to optimum performance in the LS400 but running a lower octane fuel will not damage the engine.
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Old 02-14-12, 01:36 PM   #178
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It will cause damage, it's just that our v8 is so over-built, it'll be harder to destroy it than engines with cheaper components. The 1UZ-FE is built with 10:1 static compression ratio, which is high. When engines are designed, specific octane rating is taken into consideration and without physically lowering the compression ratio (adding volume to the combustion chamber by putting a dish in pistons, increasing volume of the heads by porting or adding a thicker gaskets) you have to stick to the octane the engine was mechanically designed for. Unless you are operating at elevation over 4,000 feet above sea level where air is less dense and physics change. Retarding timing is a safety feature, but is just a band-aid.

Okay, I'll stop preaching. Run what you feel is safe, it's your car after all. Just listing facts for information sake.

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Old 02-14-12, 01:42 PM   #179
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Quote:
Originally Posted by billydpowe View Post
then think again, they do.
Cool. Thanks.
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Old 02-14-12, 01:55 PM   #180
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Quote:
Originally Posted by McPierson View Post
There is always advanced timing. That means that combustion begins with the piston on the way up. What happens with lower octane is that pockets of mixture detonoate due to the increase in pressure instead of igniting as the flame front reaches them. If timing is reduced then pressure is reduced. This is why if you have a knock sensor it can save an engine from bad gas or allow you to run low octane fuel at the cost of performance. It is much more nuanced than this, but I think you knew there was more to it anyway.

BTW: Does the LS have a knock sensor? I THINK not.
they have 2 knock sensors.
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Old 02-14-12, 01:55 PM
 
 
 
 
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