Here is a question I'm confused about. Intellitronix told me maximum horsepower is reached when you are running rich.

A friend who builds 300zx twin turbos (stage 5s) says for me to run lean (without knocking of course) to achieve maximum horsepower?

Which is correct?

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'92 Formula
305 TPI
Mods: SLP 1 5/8ths,SLP catback,SLP air foil,ported plenum,Crane AFPR (50psi),MSD6AL,homemade cold air,K&Ns,3:73s,JET fan switch, Macewen white face gauges...ZZ9 cam is coming!

 

About 13:1 Air:Fuel ratio attains the maximum power. You ALWAYS want to run richer than 14.7:1 @ WOT, BUT many people go overly rich (like 12:1).

You want to have enough gas to burn every molecule of oxygen in the cylinder without regard for pollutants. This develops maximum HP. At 14.7:1 you have complete combustion of the air with the least amount of pollutants. This does not create maximum HP, but minimizes pollution and maximizes economy. This is what the ECM tries to attain while cruising in closed loop mode at part throttle.

 

Glen I dont want to sound like an as$ but Oxygen does not burn. You may have just mixed up air and gas.

James

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If the women don't find you handsome they should at least find you handy

 

Oxygen is the element in the air that allows the gas burn. Without oxygen, there is no combustion (well there are a few other "oxidizing" elements that will also work...but they are not components of air. And that is where the word "oxidizing" comes from...oxygen.

Put a lit match in a cylinder of pure nitrogen, carbon dioxide and oxygen and notice the results. Those are the 3 major gases that make up air.

[This message has been edited by Glenn91L98GTA (edited November 08, 2000).]

 

This may sound too technical but worth reading:
The air-fuel ratio is controlled at part throttle by a closed loop system using the oxygen sensor in the exhaust.
Under controlled stoichiometric conditions the air-fuel ratio is 14.7:1, which will provide complete chemical reaction between the oxygen and the fuel. Maximum power occurs with air-fuel around 12:1 to 13:1 (Rich), but maximum thermal efficiency occurs around air-fuel 16:1 to 18:1 (Lean). Modern engines, with engine management systems, now have their maximum oxygen requirement preprogammed to near 14.5:1.
Conventionally, enrichment for maximum power air-fuel ratio is used during full throttle operation to reduce knocking while providing better derivability.
If the mixture is weakened, the flame speed is reduced, consequently less heat is converted to mechanical energy, leaving heat in the cylinder walls and head, potentially inducing knock. Traditionally, the greatest tendency to knock was near 13.5:1 air-fuel ratio, but was very engine specific.


[This message has been edited by Ozzy88GTA (edited November 08, 2000).]

 

I am going to agree with glen on this one. ozzy, i agree with you for the most part, though. what do you mean but weakening the mixture.
-- the flame speed is reduced, consequently less heat is converted
to mechanical energy, leaving heat in the cylinder walls and head, potentially inducing
knock.--
if ya mean a leaner mix, i agree. a leaner mix burns alot longer, resulting in burnt, crispy parts after prolonged lean conditions. i don't quite understand how a richer (13:1) mix would be more prone to knock then say 16:1? you could very well be right, and i could very well be wrong.
-The air-fuel ratio is controlled at part throttle by a closed loop system using the oxygen
sensor in the exhaust.-
the oxygen sensor doesn't have full control over the a/f mix. your main metering syster, such as a MAF or MAP have more control over that then your 02.
not trying to be an *** or anything, just trying to clear a few things up.

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87 iroc-z 355 TPI 5 spd. 51006 SLP cam adv. 4* (106.5* centerline)
hypertech stage II chip/ 160* stat./ Airfoil, accel AFPR
3.45 rear (stock)
Flowmaster, K&N w/ hacked airbox
14.38@100mph 2.2 60'
removed MAF screens

 

One of, if not the main, reason why a lean mixture will lead to knock is because gasoline provides TWO functions: As a fuel of course, and also as a coolant! Less fuel means less vapor capable of cooling the combustion chambers, leading to hot spots, leading to pre-ignition, et cetera.

That's why a mixture a little richer than 14.7:1 is often considered a "safely rich" mixture.

 

Pure Oxygen does burn like mad. thats why the guys in Appalo 11(i think thats the one) burned to death on the launch pad the capsule was pumped full of pure oxygen and it ignited.
I remeber on the site a long time ago a guy said that for fun he ran a line off a O2 bottle to the carb on an old beater he said it ran like a bat out of hell till it burned up the motor. thats the the way Nitros oxide works its non flamable BUT it brings an extra 02 to the combustion however if fuel is not added to the mixture then its lean and lean is HOT that burns up pistons and can make your headers glow red hot.
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Ya sure it is just an RS

B4Cyaa

1991 RS B4C
Former Nebraska Highway Patrol Car 1 of 3
305 TPI
WC T-5
Four Wheel Disk Brakes
Only Options
Rear Defrost
Am-Fm Radio
Red-int White-exe
One BA Of A 350 In The Works
Mods
Dynomax Cat Back (to hold me over till I got the $$$ for the Borla)
best 1/4mile Run of 14.92@94.83
with 145,000 on her

[This message has been edited by 91B4C jacob (edited November 08, 2000).]

 

Also, if you do any welding...you know that you add oxygen to cut the metal. You literally BURN the metal by adding the oxygen.

 

...and you need to weld with clean gloves, if the oxygen meets greasy ones, it can ignite!


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-Tom P (Hot rodded 1986 Firebird 2.8l) from http://www.f-body.net/mailbag/3rd/3rd_mailbag.html message boards
---Think your car could be pic of the week? Visit http://www.f-body.net for details!

 

an internal combustion engine is a heat pump......the hottest condtion you can create without destroying the internal parts of the engine would be the most powerful........now choose your parts ....he he and your settings

 

grease ...oil burning in the presence of pure o2 makes it possible for it to convert ALL its chemical energy into heat FAST...its that simple.O2 cannot burn...its not a fuel

 

No, that's not what I said. I never said that the grease or oil would be burning! It just has to be there, sitting unlit. Visit these links, found through yahoo.com, and look for "grease".
http://www.metalwebnews.com/howto/weld/weld.html (under oxygen cylinders)
http://www.bernzomatic.com/weldht.htm#prec (under A Few Precautions)
http://portfolio.stanford.edu/104231 (search for grease under --Welding/Cutting/Brazing)


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-Tom P (Hot rodded 1986 Firebird 2.8l) from http://www.f-body.net/mailbag/3rd/3rd_mailbag.html message boards
---Think your car could be pic of the week? Visit http://www.f-body.net for details!

 

Ok then...

There are two things consumed in the combustion chambers of our cars when that little spark plug sparks, oxygen and the hydrocarbons that is the gasoline we pump into our gas tanks all too often. These two chemicals break down and recombine in our combustion chambers, releasing energy in the form of heat and expansion (the expansion being what pushes the piston back down).

In a purely theoretical sense, The Oxygen and hydrocarbons (comprised of Carbon and hydrogen elements) recombine to form H2O (That's correct, water), and CO2 (Carbon Dioxide) both of which are at a lower energy state then O2 and our fuel (those wonderful hydrocarbons).

However, the real world isn't at all theoretical. When not enough oxygen or hydrocarbons is present we end up with CO (Our lovely and lethal friend Carbon Monoxide) and a good many environmentally unfriendly combinations of Hydrogen, Oxygen, and Carbon.

So in the end, combustion consumes both the fuel and the Oxygen. I take that to mean both components were burned up in that consumption.

 

I said it earlier and I will say it again, oxygen is the oxidizing agent.

Good explanation of the combustion process jRaskell. But in the chemical reaction, you forgot about the Nitrogen component...and its creation of NOx...and I won't EVEN get into the subject that sulphur is also present and is the reason for SO2 and H2SO4.

I know people in the petroleum industry and they have told me that sulphur emissions is a big concern and governments WOULD make emission laws requiring SOx limitations ... but there currently isn't any way to reduce it (without making gas prohibatively expensive).

 

I am supporting the guys on the fact that O2 does burn. Whenever you burn something, oxygen is added to the substance, allowing it to burn.

 

I knew there were other chemicals that reacted to make some of our annoying pollutants, I just wasn't sure and didn't want to post anything that was out right wrong. I was pretty sure of nitrogen, but I forgot all about sulfur.

 

Just to throw more fuel on this fire ...

(bad joke, sorry)

The the most energy will be released, and the greatest heat will be generated at stochiometrey (sp?), and thus the greatest work.

Richer ratios are there to cool chambers and prevent detonation in engines that routinely exceed their nominal design specifications. Richer ratios do not necessarily produce more power by themselves ... .they are a crutch to keep and inadequately designed system from self destructing.

Much of this can be laid to ancient combustion chamber designs and thinking, which have changed litte in the interval between Marilyn Monroe and Marilyn Manson.

Sir Harry Riccardo, and later, Michael May did loads of research on chambers, flame travel, etc, and produced designs that could withstand static CR's in the 12:1 range with no detonation on 87 octane fuel. They also ran much closer to stoichiometry, produced more power per liter, and emitted fewer pollutants.

More recently, people like Jim Fueling (what a perfect name for his line of work, LOL) and Robert Yates have completely tossed traditional thinking out the window about both a/f ratios and static compression . It would take a couple of books to explain their work, but the bottom line is that a set of Fuelings, with intakes smaller than an SBC exhaust made over 700 hp, with a closed loop FI system, and BSFC numbers in the sub .30 range (.29, IIRC) which is beyond phenomenal.

And, Chevy lovers, recall too the wild success of the FI Jack Roush Trans Am cars. By using a stock Ford engine computer, reprogrammed to provide adjustable a/f's, they were able to lean their engines out on the long stretches, increasing both power and mileage.



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Bob
'87 Formula TPI 5-speed

 

Just to throw more fuel on this fire ...

(bad joke, sorry)

The the most energy will be released, and the greatest heat will be generated at stochiometrey (sp?), and thus the greatest work.

Richer ratios are there to cool chambers and prevent detonation in engines that routinely exceed their nominal design specifications. Richer ratios do not necessarily produce more power by themselves ... .they are a crutch to keep and inadequately designed system from self destructing.

Much of this can be laid to ancient combustion chamber designs and thinking, which have changed litte in the interval between Marilyn Monroe and Marilyn Manson.

Sir Harry Riccardo, and later, Michael May did loads of research on chambers, flame travel, etc, and produced designs that could withstand static CR's in the 12:1 range with no detonation on 87 octane fuel. They also ran much closer to stoichiometry, produced more power per liter, and emitted fewer pollutants.

More recently, people like Jim Fueling (what a perfect name for his line of work, LOL) and Robert Yates have completely tossed traditional thinking out the window about both a/f ratios and static compression . It would take a couple of books to explain their work, but the bottom line is that a set of Fuelings, with intakes smaller than an SBC exhaust made over 700 hp, with a closed loop FI system, and BSFC numbers in the sub .30 range (.29, IIRC) which is beyond phenomenal.

And, Chevy lovers, recall too the wild success of the FI Jack Roush Trans Am cars. By using a stock Ford engine computer, reprogrammed to provide adjustable a/f's, they were able to lean their engines out on the long stretches, increasing both power and mileage.



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Bob
'87 Formula TPI 5-speed

 

3 words:

LEAN IS MEAN (until you burn a piston)

 

Hey Ragtop, in theory the stoichiometric ratio of air to fuel will produce the most horsepower and efficiency, however, the real world often deviates from theory. It is often necessary to run an AF ratio by mass of 13:1 so as to atomize enough fuel to actually realize the most efficient (not from an emissions standpoint) combustion. This is why any engine I've ever seen performs best at a rich AF ratio, although some more phenomenal combustion chamber designs and excellent atomization of the fuel, along with good turbulence of the intake charge may allow some engines to do quite well at 14.7:1, and see little difference in running 13:1. The main reason our vehicles use an oxygen sensor to average an AF ratio of 14.7:1 is because at this point the three-way catalyst is most efficient at converting the harmful emissions from the combustion process. Although it will not minimize any of the major pollutants (CO, UHC, NOx) at this AF ratio, it is the best compromise.

 

Wow. that was a lot of big words.ah......


Anyway, I've come to the conclusion that "lean is in fact mean". I've been tinkering with my AFPR all week. I finally found the perfect setting. 33pounds. The car just won't stop pulling! I have to change my underwear everytime I get out.

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'92 Formula
305 TPI
Mods: SLP headers,SLP catback,SLP air foil,ported plenum,Crane AFPR (50psi),MSD6AL,homemade cold air,K&Ns,3:73s,JET fan switch, Macewen white face gauges...ZZ9 cam is coming!

 

Sounds like you got your answer back there somewhere. If anything at least you got a chemistry lesson.

 

LOL ozzy.

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'92 Formula
305 TPI 5speed
1LE package
Mods: SLP headers,SLP catback,SLP air foil,ported plenum,Crane AFPR (42psi),MSD6AL,homemade cold air,K&Ns,3:73s,JET fan switch, Macewen white face gauges...ZZ9 cam (i still have to install it )