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AFR why I'd rather be lean than rich...

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Old 10-12-2006 | 09:19 AM
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Default AFR why I'd rather be lean than rich...

i've always noticed this and thought it was weird...

but as an old school carb guy i always would rather have my stuff too lean than too rich when going WOT..

i have found that too rich breaks the big **** like blocks, rods, and cranks...

and being too lean i have found usually just scorches pistons or burns up a piston...


i dont know about you guys but i'd rather replace a piston or 2 than a whole setup...

thats just my knowledge from what i have done before.... so i dont see why it should be any different... a motor is a motor... it takes fuel, air and timing...
Old 10-12-2006 | 11:50 AM
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Ahhhh... What?
Old 10-12-2006 | 02:21 PM
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no one have opinions on this... i figured it would be highly and quickly disputed.... hmmm
Old 10-12-2006 | 02:33 PM
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Originally Posted by ty_ty13
i've always noticed this and thought it was weird...

but as an old school carb guy i always would rather have my stuff too lean than too rich when going WOT..

i have found that too rich breaks the big **** like blocks, rods, and cranks...

and being too lean i have found usually just scorches pistons or burns up a piston...


i dont know about you guys but i'd rather replace a piston or 2 than a whole setup...

thats just my knowledge from what i have done before.... so i dont see why it should be any different... a motor is a motor... it takes fuel, air and timing...
Running rich usually doesnt break stuff unless its very rich for a long time. But all it takes is one time running a little too lean and you can trash your motor.
Old 10-12-2006 | 02:40 PM
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Originally Posted by Smartass6885
Running rich usually doesnt break stuff unless its very rich for a long time. But all it takes is one time running a little too lean and you can trash your motor.

if you dont light the fuel thats in the cylinder that becomes a problem... you cant compress a liquid.... thats when it starts bending rods, and cranks...

so if you ever blow out your spark and you got all that fuel in there its a problem....

where atleast if your lean you just burn some pitsons.... or compress alot less fuel which still might have some room to fit @ the TDC

Last edited by ty_ty13; 10-12-2006 at 03:01 PM.
Old 10-12-2006 | 04:18 PM
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Old 10-12-2006 | 04:20 PM
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Define rich and lean (in terms of A/F ratio).
Old 10-12-2006 | 04:29 PM
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Old 10-12-2006 | 05:18 PM
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anything below 12.1 is rich in my terms in a blown motor...
Old 10-12-2006 | 05:33 PM
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Originally Posted by ty_ty13
if you dont light the fuel thats in the cylinder that becomes a problem... you cant compress a liquid.... thats when it starts bending rods, and cranks...

so if you ever blow out your spark and you got all that fuel in there its a problem....

where atleast if your lean you just burn some pitsons.... or compress alot less fuel which still might have some room to fit @ the TDC
I do not believe that you will be compressing any liquid anyway if you are running rich, most of the fuel will still burn and whatever else is left will be spit out the exhaust anyway. Fuel is added after the compression stroke and then burned, then spit out, so how would any liquid be compressed? maybe a few fuel particles would be left but thats about it.
Old 10-12-2006 | 06:23 PM
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The exhaust valve opens towards the bottom of the power stroke. Not lighting off that cylinder's charge will not result in damage from hydraulicing the engine.

Per my quick calculations a 1000 hp 346 would need about 1.93 cc's of fuel per cylinder a cycle @ 6800 rpm. Hardly enough to worry about if it didn't fire.

Last edited by andereck; 10-12-2006 at 07:00 PM.
Old 10-12-2006 | 06:37 PM
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Originally Posted by andereck
The exhaust valve opens towards the bottom of the power stroke. Not lighting off that cylinder's charge will not result in damage from hydraulicing the engine.
Right, but unburnt fuel can just be forced out the exhaust port even if it is unburnt. If you are running that damn rich anyway you have some real issues. I was assuming that the thread starter wasnt meaning that rich to where you are washing down.
Old 10-12-2006 | 07:13 PM
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Originally Posted by ty_ty13
i've always noticed this and thought it was weird...

but as an old school carb guy i always would rather have my stuff too lean than too rich when going WOT..

....i dont know about you guys but i'd rather replace a piston or 2 than a whole setup...
Dude, that's just f'n crazy.

Too rich, temp is cold and engine is low on power.

Way too lean, engine is cold and low on power.

Transitioning from ok AFR on the way to too lean, temp is at max (at or near stoic) and the engine decides to combust aluminum to make up for your crazyness.

Nitrous tuneup= plugs and pistons. Hope you can do it in under an hour.
Old 10-12-2006 | 07:36 PM
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Originally Posted by brad8266
Fuel is added after the compression stroke and then burned, then spit out, so how would any liquid be compressed?
Are u serious? You are WAAAY off dude! This is one of the most basic things to know about a 4-stroke internal combustion engine.

It's intake, compression, power, exhaust. The piston moves down pulling in a fresh intake charge of air AND fuel, then it moves up COMPRESSING the mixture, the spark-plug fires igniting the mixture, the piston goes down which produces the power, then it goes back up and pushes the exhaust gases out
Old 10-12-2006 | 07:38 PM
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Originally Posted by BriancWS6
Are u serious? You are WAAAY off dude! This is one of the most basic things to know about a 4-stroke internal combustion engine.

It's intake, compression, power, exhaust. The piston moves down pulling in a fresh intake charge of air AND fuel, then it moves up COMPRESSING the mixture, the spark-plug fires igniting the mixture, the piston goes down which produces the power, then it goes back up and pushes the exhaust gases out
Ok then that blows this whole threads idea away. Everyone is saying you cant compress fuel and if it does thats how you break parts. And now you are saying compressing fuel is the basics of the 4 cycle engine. So who is right here??
I do take back what I said about the fuel not being compressed. It does compress the air/fuel mixture. Thats my bad. i stand corrected.

The too rich or too leana rgurment is still on though.

Last edited by brad8266; 10-12-2006 at 07:48 PM.
Old 10-12-2006 | 07:45 PM
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He's right, you're not this time. Fuel is injected with the intake of air. That mixture is then compressed. The liquid fuel droplets are suspended in the intake air that is compressed. As I mentioned above a 1000 hp v-8 would have 2 cc's or less fuel suspended in the charge. A 9 to 1 LS1 would have 74 cc's or so clearance volume so there would be no risk of mechanical damage from hydraulics.
Old 10-12-2006 | 07:49 PM
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Originally Posted by andereck
He's right, you're not this time. Fuel is injected with the intake of air. That mixture is then compressed. The liquid fuel droplets are suspended in the intake air that is compressed. As I mentoined above a 1000 hp v-8 would have 2 cc's or less fuel suspended in the charge. A 9 to 1 LS1 would have 74 cc's or so clearance volume so there would be no risk of mechanical damage from hydraulics.
yeah yeah that was kinda dumb for me to say.
I agree with you that there is not going to be mechanical damage from being too rich. All you will do is run like ****. Some extra fuek isnt gonna caused hydrolock or anything.
Old 10-12-2006 | 07:53 PM
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But at least you're not crazy.
Old 10-12-2006 | 10:53 PM
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you guys can say what you want but i have a pile of cranks and rods from being rich.... and a shelf of pistons from being lean.... you just take your pick
Old 10-12-2006 | 10:56 PM
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Well, I don't want either but thanks for the offer. I do have some Holley jets I'll loan you and I know a couple good machinists if you're interested. You should recycle the aluminum, its good for the environment.


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