i can’t be the only one who runs regular in a GT right?

[K4fxd]

So much for public safety and improving the quality of life for your citizens.

With the amount of traffic these days I have mixed thoughts on high speed chases for non felony's.

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[Dave2013M3]

That pretty much nailed it.

 

[Bikeman315]

So much for public safety and improving the quality of life for your citizens.

With the amount of traffic these days I have mixed thoughts on high speed chases for non felony's.

700 miles from Myrtle Beach to Commack, LI. The number of morons on the road was beyond belief. We lost count of the number of cars that passed us at 100+ MPH. Passed one crash on 95 in Virginia were there was a car in pieces.

 

[sk47]

Hello; Is this the correct take on timing? The two strokes of a four stroke engine in question are the compression and power strokes. With no advanced timing the air fuel mix is ignited by the spark plug at the exact top of the compression stroke.
Since the explosion of the air fuel mix is not instant and takes some time it was found that the timing of the ignition spark could be set to happen just before the piston reaches the top of its compression stroke. Am I correct in thinking this is the basic definition of advanced timing? That using the 360 degrees of a circle most engines are set to have the spark advanced before TDC (top dead center) by some number of degrees of a full circle. Some where around 20 + degrees before the piston reaches TDC is common.
My take has been that igniting the air/fuel mix just before the piston reaches the top of it's movement upward during compression allows the full energy of the explosion to happen just as the piston starts back down during the power stroke. In other words it takes a while for the explosion (burn) of the air/fuel mix to happen. So, if you start the burn a little early it will not be very strong right away and if it is timed just right you will get more power out of each explosion (burn) during the power stroke.

Another part is the compression of the air fuel mix. The more you can compress the air fuel mix, then the more power you can get out of the air/fuel burn when it happens. Gasoline can only be compressed so much in the ideal air /fuel mix before it will self-ignite from the compression itself.
Side note- if you have an air compressor try this. Touch the tank of the compressor before you turn it on. It will be cool. when it builds up to 125 psi or whatever it gets up to hold your hand close to the tank. (might be too hot to touch comfortably) The heat comes from the compressed air. The air goes from an ambient temperature, say 70 degrees F, at just under 15 psi and a volume of many cubic feet (say a room space) down to 25 gallons at 125 psi. Not only is the air itself compressed but the heat energy in that room sized volume of air is compressed as well. So, the temperature goes up.
To get the most power from the air/fuel mix it is good to have a higher compression ratio. If an average car has a compression ratio of 8 or 9 to one, a higher performance engine can have a ratio of 12 to 13 to one. Untreated gasoline will self-ignite at some higher compression ratio. So, additives which resist this self-ignition can be added to stop it.
My take is if you are running 87 octane in the higher compression engines such as a Mustang that fuel will on the edge of self-ignition (diesel) to begin with, so the ignition timing is retarded by several degrees to prevent a too early start of the burn.
I use to set the base timing by moving a distributor myself. The distributor had two ways to slightly adjust the timing itself. One was a set of spring-loaded weights which mechanically moved the distributor as the rotation speed increased. The other was a vacuum motor plumbed to the intake manifold which reacted to manifold pressure. Not much range of change. Now we have computers getting messages from a host of sensors which can do big changes of timing and air/fuel mixture in fractions of a second.

There is a discussion to be had about valve timing in all of this, but not today. What do I have correct? What do I have wrong?

 

[K4fxd]

You want max cylinder pressure somewhere around 15 degrees after top dead center. To allow for this to happen we must light the mix before TDC. Most modern engines like about 30 degrees for max power. With slower burning fuel we need to light it even earlier causing resistance to the piston moving up. At some point you will lose more power than you gain by advancing timing. So introduce fast burning high octane fuels.

 

[IPOGT]

700 miles from Myrtle Beach to Commack, LI. The number of morons on the road was beyond belief. We lost count of the number of cars that passed us at 100+ MPH. Passed one crash on 95 in Virginia were there was a car in pieces.

It’s all about what you allow to happen.

 

[sk47]

Which gas stations have the best quality fuel? (msn.com)

 

[ICU812]

Yes it will. 94 seems to be the limit for advance.


Yes it does. Service manual says up to 15% but I have tested to 50% with no wrench light.

Nope it does not. Lots of race fuel companies engineer it to burn faster. This takes advantage of being able to have higher cylinder pressure using less timing advance.

It burns slower, the higher cyl pressure is what causes it to burn fast. this IS why using higher octane than needed hurts performance as much as it helps.
Go run 116 in your mustang if you need proof.

 

[K4fxd]

It burns slower, the higher cyl pressure is what causes it to burn fast. this IS why using higher octane than needed hurts performance as much as it helps.
Go run 116 in your mustang if you need proof.

It does not burn slower. Google is wrong. Call a fuel provider and ask the tech dept. They will have low and high octane fuels that burn fast and some that burn slow. Octane is not the reason for fast and slow burn.

From sunoco

" Naturally aspirated race motors with large combustion chambers spinning at high RPMs really like high-octane, fast burning fuels. They need the octane to prevent uncontrolled combustion, and they need a fast-burning fuel so that the flame front can span the large bore of the combustion chamber quickly. If you’re not sure which fuel burns faster than others, one indicator is specific gravity. “Lighter” fuels – fuels with a lower specific gravity – tend to burn faster because fast burning hydrocarbons are themselves light. Look for a specific gravity close to 0.70 and you’ll likely find a fast burning fuel. "

https://www.sunocoracefuels.com/tech-article/beyond-octane

 

[ICU812]

It does not burn slower. Google is wrong. Call a fuel provider and ask the tech dept. They will have low and high octane fuels that burn fast and some that burn slow. Octane is not the reason for fast and slow burn.

From sunoco

" Naturally aspirated race motors with large combustion chambers spinning at high RPMs really like high-octane, fast burning fuels. They need the octane to prevent uncontrolled combustion, and they need a fast-burning fuel so that the flame front can span the large bore of the combustion chamber quickly. If you’re not sure which fuel burns faster than others, one indicator is specific gravity. “Lighter” fuels – fuels with a lower specific gravity – tend to burn faster because fast burning hydrocarbons are themselves light. Look for a specific gravity close to 0.70 and you’ll likely find a fast burning fuel. "

https://www.sunocoracefuels.com/tech-article/beyond-octane

The only reason you get a controlled burn is because it burns slower, the flame progression of the flame front is slower, the higher cyl pressure force it to move.
It has been this way since the 50's when hot roders started upping compression to make more power.
If it burned faster it cause uncontrolled flame progression and flame front, this never ends well. most times running over parts.

 

[K4fxd]

Believe what you want.

So you are going to argue with Sunoco? Do you manufacture gas?

 

[K4fxd]

Don't feel pregnant, I believed the offset pin makes more power till I tested it on a dyno.

 

[velocityblue5.0]

Don't feel pregnant, I believed the offset pin makes more power till I tested it on a dyno.

What lol

 

[rhexis]

late fall until i put it away for the winter i only put in sunoco 93 and occasionally 16oz of boostane. in the spring and summer it uses e85 that tests for me as high as 82 which is not bad for wawa e85. i would never consider using 87 it just seems wrong to me.

 

[BULLITT480]

Wrong on so many levels. lean mixture burns pistons.
you can be running 112 race gas and burn a piston just as easily as you can on 87 swill if your air /fuel mixture is too lean.
Higher octane means slower burn rate, Allowing you to produce higher cylinder pressure before lighting it off.
I think you are confusing breaking/shatering a piston to burning a hole in one from a lean a/f mixture.
Octane has zero to do with burning a hole in a piston.

yes i am aware that a lean af ration will burn/melt a piston. That is the trick of too many tuners trying to get the last 1/2 hp out of an engine on the dyno. But preignition will also burn a piston and lead to a catastrophic failure. In addition preignition due to lesser octane will develop carbon deposits on the piston effectively raising the compression ration , albeit slowly, which will lead to increased preignition detonation. With the oil on the piston you are now more likely to incur LSPI.

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