Can someone explain to me what detonation is, and how it effects the performance of the truck? Thanks

 

Dear Noles,

Detonation is another name for "spark knock", a condition that occurs when you have too much spark advance for the octane level of the gasoline being used, too high a compression ratio, too much heat in the combustion chamber, etc. Usually, it's from too much spark advance. It is uncontrolled spontaneous combustion, and makes a sound kind of like marbles in a can, or a "rattle" type of sound.

There are others here who can explain it for better and more thoroughly than I, and perhaps they'll add their thoughts on this.

It's basically the fuel mixture igniting long before it's supposed to, while the piston is farther down the bore than it would be normally, and can cause engine damage if allowed to continue for prolonged periods.

That's a very basic and rough explanation, I hope it helps your understanding.

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Mike Troyer
Performance Products, Inc.
National Distributor of Superchips
(540) 862-9515
Email: mtroyer@compuserve.com

 

Mike's right on the money. I've usually heard it called "pre-detonation" (every time the sparkplug fires there is supposed to be a "detonation" ).

Under normal circumstances, the sparkplug fires before the piston reaches the top of its stroke - spark advance. This is because it takes time for the fuel mixture to burn and build up the correct pressure in the cylinder to force the piston down and produce power (this is often referred to in degrees of crankshaft angle eg., 10 degrees before top-dead center). As the rpm's increase, the spark must occur when the piston is farther down in the cylinder on it's compression stroke. At idle, the advance might only be 5-10 degrees, but at high rpm it might be 30-50 degrees. It takes the same amount of time for the fuel to burn regardless of the engine rpm.

When pre-detonation occurs, the piston is not only fighting against the air pressure it is supposed to create, but also the pre-mature burning of the fuel mixture.

Diesel engines mainly use the heat of the compression stroke to trigger the fuel mixture burn. I believe that some (all?) diesel's prevent pre-detonation by not injecting the fuel until the timing is correct, rather than compressing the fuel and air together during the full stroke.

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98 F150 XLT SC 4.6 4x4 ORP 3.55 LS, Factory: towing pkg, fogs, steps, slider, remote entry; Hella driving lights, aux backup lights, K&N filter and airbox mod, Rhino lining, Roll-n-lock cover, SuperChip, fog light mod, AC mod, spare tire mount mod

 

Could using 93 Octane in a stock engine without a superchip cause detonation?

 

PGMR, thanks for that explanation. It cleared up some of the smoke on spark advance in my skull. I learned something today. CAn I go home now? Im an electrical guy myself.



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White 1999 F150 4X4 XLT Regular Cab, 5.4L Short bed, 373 Rear, Towing & Off Road Pkg, 6 Disk CD, Keyless Entry

Mods Include : Superchip, Flowmaster exhaust, Chrome bed rails and Smittybilt nerfs, Full window tint,
K&N filter, Ventshade window deflectors. Triton boats tag on front - BASS sticker in rear glass

 

Thanks guys, for all the helpful information.

 

Dear Blockhead,

No, it cannot. However, if you have a late-model Ford, without a Superchip, and you're using 93 octane, you're wasting money, except for perhaps better detergents in premium gas. Your Ford owner's manual (for all non-performance vehicles) states to use only 87, (or some words to that effect) and there's a reason. Higher octane fuels burn slower, so using premium can sometimes cause driveability problems in Fords, believe it or not! I've seen this happen myself, when it happens the vehicle acts "soggy", and has noticeably poorer throttle response. Soggy, in other words. (That's a scientific term!)

If you use a Superchip, it completely reprograms the fuel curves specifically for the use of premium. (Just in case anyone was wondering why you can use premium with the Superchip)

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Mike Troyer
Performance Products, Inc.
National Distributor of Superchips
(540) 862-9515
Email: mtroyer@compuserve.com

 

Mike,
I was running 93 while the chip was in the mail. Got the chip installed. I could tell it was a little sluggish running high octane before the chip, that's why I was wondering about the detonation. Runs great now.

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'99 Oxford White F150, 5.4L, 3.55, Mobil 1, Superchipped

 

Mike,
I have a question for you. I have a Superchip in my '99 and it kinda hesitates on take off. It doesn't matter if I take off slow or fast, it still does it. Just wondering if you think the chip mght need to be reprogramed or if you might know what else could be causing this? Thanks