92Camaro305TBI

What is a KNOCK sensor?--- What is its purpose

What do you mean by "RETARD" the timeing or otherwise?

Detination(sp?)----what is that... beside explosions!

What does "your system being "lean"" mean?

Anymore I'll post later ... Thanks for the help.. I'm learning not stupid...!!!

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92 Camaro 305 TBI Automatic
2.5 high flow cat
2.5 pipes
3.5in tip
shift kit
Tinted windows(legal)
Spark plug wires and plugs...
14X3 O.E. K&N Filter

Future mods.
Headers
any other advise on getting to 300+ HP would be appreciated. Thanks
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System = Sony explode 5000 CD/MD receiver
Rockford 6x9 Fanatics
Rockford 4x6 Fanatics
Rockford 2 12" Hx2's
Rockford 1 farad cap
Rockford 800x2 Amp
Custom box
4gauge wire kit

ATOMonkey

The knock sensor measures vibrations in the engine block. Knock is a word used to describe detonation, which is an explosion instead of controlled burn in the combustion chamber. Detonation is caused by lean conditions or over advanced timing or hot spots (also called preignition). To answer your other question lean is when your air to fuel ratio is larger than what is desired. Rich is when your ratio is smaller than desired. Timing is measured in degrees before the piston reaches the top of the compression stroke(TDC Top Dead Center). Retarded timing is anything after TDC advanced timing is anything before TDC. Most engines run 30 degrees total advance and 8 degrees base advance. I hope this helps. There is a lot to learn about engines. Good Luck

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'87 Bird 350 .060 over 700R4 + Lots more

Xenodrgn

I'll do the easy one, I can't go technical enough into the other ones to answer them so you'll get it. When your engine is running 'lean', that means that there is not enough fuel for the amount of air in the combustion chamber. Running rich is the exact opposite, too much fuel for the amount of air. Both can be very detrimental to performance. Lean-ness will cause just a short explosion, not really creating alotta power, richness and it won't burn. Too rich and you'll actually extinguish the spark. The ideal situation is to have an air/fuel ratio that will burn the entire length of the power downstroke, and then be completely burt when it's expelled in the exhaust stroke (in an EPA heaven).

So to answer your question simply:
Lean = not enough fuel
Rich = too much fuel

[EDIT] typo's...
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1985 Camaro SC - 2.8L, auto.

http://www.xenodrgn.f2s.com/Frontright.jpg

[This message has been edited by Xenodrgn (edited July 11, 2001).]

Enkil

In order of the questions...

A knock sensor, ermm... senses knock. Knock is another word for detonation, which we'll get to in a later question. It's purpose is to tell the computer the engine is knocking/pinging/detonating/whatever you want to call it.

Retarding the timing is to put it in the direction of being after top dead center. Advancing it is the opposite -- to put it more towards the direction of being before top dead center.

If you don't want an explanation on retarding and advancing and what it does, skip this paragraph. The pistons are moving up and down, and the crankshaft is going around in a circle. When the piston is at the VERY top of it's travel, the crankshaft is at 0 degrees. This is known as Top Dead Center (TDC). If your timing was set to 0* TDC, then when the crankshaft hit 0*, the sparkplug would fire at that instant. Now, let's say you wanted to retard your timing. This is to set it AFTER top dead center, or while the piston is on it's way back down. If the sparkplug fires after top dead center, then the resulting combustion will not be able to "push" the piston down as hard as it could. Imagine running after a wagon, and kicking it while it's already moving. All the force of your kick can't go into pushing the wagon that much faster. On the other hand, say you advanced your timing, or put it BEFORE top dead center. In this case, the sparkplug fires while the piston is on it's way up. If time just right, most of the combustion will happen right as the piston is reaching top dead center, and so therefor the most of the explosion can be used to push the piston back down.

What are the benefits/disadvantages of retarding/advancing? Let's start with retarding. The benefits of retarding your timing is that it's easier to start the car. Not a lot of pressure is built up inside the cylinders to make it harder for the starter to turn the engine. On the down side, you're wasting power and gas if it's too retarded. The benefits of advancing the timing are that if you get it just right, you can maximize fuel economy and power, as the most of the potential energy of the fuel will be used. The disadvantages? Well, the more advanced you go, the harder it is to start. Say you're the starter, and you're turning an engine. While you're turning it, somebody on the other side is trying to push down while you're trying to push up. Makes your job that much more difficult. If you advance your timing TOO much, you'll wind up with engine knock, which we'll get to in a minute.

Detonation/engine knock/pinging is the unwanted explosion of the air/fuel mixture at the wrong time. There are several things that can cause this. Advancing the timing too much can cause it. While the piston is on it's way up, the sparkplug fires way too early and most of the force of the explosion goes into pushing the pistons back down. "Hot spots" in the engine (parts of the block that heat up more than others for whatever reason) can cause it too. If the hot spot is hot enough to ingite fuel, then.. boom. If the compression of the engine is too high, this too can cause the engine to knock. The compression ratio is found by dividing the volume of the cylinder when the piston is at the very bottom by the volume of the cylinder while the piston is at the very top. I may have those backwards, but you get the idea. Anyways, the higher the compression ratio, the more the air/fuel mixture is compressed. And the more you compress a gas, the hotter it gets. If it gets hot enough, it'll explode.

Whatever the cause, engine knock is VERY detrimental to power and the life of the engine. As such, they put knock sensors in our car. If it detects knock, the computer will retard the timing a LARGE amount in an effort to get it to go away. Slowly, the engine will return back to whatever you set the timing at.

Finally, having your engine run lean means that not enough gas is going into the air/fuel mix to get the most power out of it. If there's not enough gas, it's being starved, basically. On the other hand, you can be running too rich as well, which is to say that too much gas is getting into the mix. With too much gas and not enough oxygen, the unburnt fuel will foul the plugs and flood the engine.

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89 iroc-z 305 tbi
k&n filtercharger, open element air filter. nuffin' else

92Camaro305TBI

Man you guys are awsome.. Thanks for the help... Ok.. I think I got everything explained....

when i changed my exhaust( From 2 1/4 w/ muffler to 2 1/2 without muffler)... will this cause my air/fuel to go lean or rich and how would I know/tell?..


For some reason I dont see the logic how this could happen becuase the air/Fuel happends before it goes into the exhaust... unless the exhaust puts preasure on the place there the gases excapes???

Am I just out of my mind and thinking to hard.. ???

Enkil

It shouldn't make that much of a difference... If you wanna know whether or not you're running rich or lean, pull a sparkplug. White is lean, black is rich, and brown is juuuuuuust right. hehe

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89 iroc-z 305 tbi
k&n filtercharger, open element air filter. nuffin' else

One Eyed Jack

Is burning lean better than burning rich, in terms of engine damage / carbon deposits?

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1992 Pontiac Firebird
- 305ci V8 TBI / Automatic Trans / Loaded
- MODS: Edelbrock 14x3 Open Element Air Cleaner, Dual outlet exhaust
1985 Chevy Z28
- 350ci V8 TPI / Automatic Trans / Paid $200 for it
- In the process of restoration!

AJ_92RS

NO!!!! Running rich is "safer" albeit better. When the A/F ratio is lean, it causes backfires, HOT exhaust manifolds, HOT pistons, HOT valves. It's just not good at all. Neither are good, but better rich than lean. Rich means backfires through the exhaust, and less MPG, but it's still safer than lean.

ColinOpseth

Rich is generally why most MemCal's have stock settings for limp home mode, they retard timing and richen the mixture..

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Webmaster: www.IROC-Z.org

Red Devil

Just to clarify the detonation thing... Detonation happens only after the spark plug fires, otherwise (as ATO pointed out) it is called pre-ignition.

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"Question with boldness even the existence of a God; because, if there be one, he must more approve of the homage of reason, than that of blind-folded fear."

-Thomas Jefferson