detonation

[fastTa]

I'm confused myself. The internet source and you say one thing, My Ignition/MSD book & my Smokey Yunick book say another. Smokey ought to know what he's talking about, but like I said, it's a terminology problem where we are getting conflicting answers.

The best way to describe it is if you get knock & pinging (the rice & tin foil sound which usually triggers the knock sensor to pull timing) in a high compression engine, thats a potentially harmful warning sign, and if you ignore the knock, you might get bang, bang, bang, - maybe busted piston lands, holes in pistons or smashed & battered crank & rod bearings. Need to avoid the abrupt violent pressure spike when the piston is on the upstroke. Everyone agree?

So what does Smokey say exactly? But, yes I will agree that if you can audibly hear detonation that it is not a desirable thing.

Here is the thing. To optimize horsepower in an internal combustion motor you want to have your overall timing advance set to such that the resulting "normal" combsution process makes peak cylinder pressure at 14 degrees ATDC, 16 for an all out drag race motor. Obviously, you don't want excess heat and pressure interfering with that because anything applying abnormally excess pressure on the piston during the compression stroke places undue stress on the wrist pin, rod, and can severely scuff the skirt. All not good.

How's that Piels taste tonight?

['01WSsick]

Thanks for the info. i just need some time to tear into it and see whats wrong. i will check the plugs but you all know how fun plugs are on an f-body. A fuel issue was just my first thought, but i always run 93 so i thought it might not be increasing voltage to the pump as the throttle is increased. If im not mistaken thats how the returnless fuel system works. but as soon as i tear into it i will let you know, i have been busy building my s-10, never build an s-10, they are more of a pain then they are worth, but fun when finished.

[Kevin - Blown 95 TA]

So what does Smokey say exactly? But, yes I will agree that if you can audibly hear detonation that it is not a desirable thing.

Here is the thing. To optimize horsepower in an internal combustion motor you want to have your overall timing advance set to such that the resulting "normal" combsution process makes peak cylinder pressure at 14 degrees ATDC, 16 for an all out drag race motor. Obviously, you don't want excess heat and pressure interfering with that because anything applying abnormally excess pressure on the piston during the compression stroke places undue stress on the wrist pin, rod, and can severely scuff the skirt. All not good.

How's that Piels taste tonight?

Well Smokey goes on bout detonation destroying stuff, so he isn't talking about pinging, although in a high enough compression race engine, the two probably happen pretty quick.

I'm off beer to lose weight, so I am drinking Jim Beam when I need to get a little sideways.

[Injuneer]

..... A fuel issue was just my first thought, but i always run 93 so i thought it might not be increasing voltage to the pump as the throttle is increased. If im not mistaken thats how the returnless fuel system works.... d.

The LS1 uses a fuel pressure regulator. It does not alter the pump voltage to control pressure. The system is "dead ended" because the pressure regulator is mounted directly to the fuel pump module.

[Rhode Island Red]

01WSsick - You might want to try this before changing the spark plugs.

Go to your nearest GM dealer and buy some GM top end cleaner. You see LS1's tend to build up carbon rather badly if you drive the car at low RPM's (below 2500) most the time.

What happens is the carbon builds up over time and slowly creeps up the compression. Eventually the compression exceeds the amount of knock 93 octane gas naturally prevents. This has happend to me several times (I really can't rev to 55000 rpms regularly enough to blow out the carbon )


what you do is:

1) start the car and get the engine warm.
2) Take of pcv filter
3) Pour the top-end cleaner into the tube connected to the Throttle body.
4) increase rev's slight so as it not to stall
5) near the end of the bottle, dump the last remaining bit in all at once. The engine may cut out but this is ok.
6) Immediately turn off Key and let it sit for 1/2 hour and reattach pcv filter.
7) Turn on car and rev slightly to about 1100 rpms and hold it there and watch the smoke fly

It really does smoke out your neighborhood ! so make sure your in an ok area to do this

I betcha this will probably cure your problem