lean? rich? - 600RR.net
Exhaust & Fuel Delivery Tips on how to get the most out of your bike

 
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post #1 of 21 (permalink) Old 05-07-2009, 02:53 AM Thread Starter
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lean? rich?

i dont know to much about running lean and rich.. can someone break it down for me? ive heard that lean is running to much air.. and rich is running to much gass.

what are the benefits for either or. and wat is best for your bike?
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post #2 of 21 (permalink) Old 05-07-2009, 06:04 AM
 
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I'm no expert and will gladly be corrected if I am incorrect!

Lean and rich usually refer to the amount of fuel vs air ratio's. Think of a certain volume, say 1 litre, this space can only be occupied by 1 litre no more no less, so if we have 50% air and 50% fuel we can not add any more volume to the litre. If the perfect air fuel ratio was 50/50 it would not be rich or lean, but if we changed the air to say 70% and the fuel to 30% then it would be lean. Conversely if we changed the air to 30% and the fuel to 70% it would be a rich mixture.

There are other factors such as air density, humidity and elevation effect this in many ways. As elevation increases air becomes thinner, the oxygen component becomes less, therefore your mixture if unchanged becomes richer. Humidity also makes your mixture richer, because of the water molecules in the air, taking up more space, less air, more fuel.

Thankfully modern efi eliminates most of the nightmares, until we put new exhausts, air filters etc with out re-tuning the efi system to match.

Or sensors give you nightmares and cold sweats doing what they want to do, irrespective of what they are being told!!
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post #3 of 21 (permalink) Old 05-07-2009, 01:44 PM Thread Starter
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what are the pros and cons of running lean.. and visa versa for rich?
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post #4 of 21 (permalink) Old 05-07-2009, 01:50 PM
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Running rich or lean is something you try to avoid. It's a measurement away from perfect

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post #5 of 21 (permalink) Old 05-07-2009, 01:52 PM
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Quote:
Originally Posted by p3t3rc View Post
what are the pros and cons of running lean.. and visa versa for rich?
run lean = make more power and runs HOTTER
run rich = make less power and runs cooler


^thats the short version, there's lots more. But you dont wanna be in the far end of either one because both can harm your engine.

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post #6 of 21 (permalink) Old 05-07-2009, 02:45 PM Thread Starter
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ah i see. thanks for the info guys. the reason why i ask is because im about to gutt my intake as seen on this thread https://www.600rr.net/vb/showthread.php?t=101096 and i was just wondering if that would make my bike run lean.
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post #7 of 21 (permalink) Old 05-07-2009, 02:58 PM
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Quote:
Originally Posted by p3t3rc View Post
ah i see. thanks for the info guys. the reason why i ask is because im about to gutt my intake as seen on this thread https://www.600rr.net/vb/showthread.php?t=101096 and i was just wondering if that would make my bike run lean.

no need to worry... thats not enough to lean out the a/f ratio


but if you do an aftermarket air filter and full exhaust it definitely will

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post #8 of 21 (permalink) Old 05-07-2009, 03:31 PM Thread Starter
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what about just an after market filter? i was thinking if i should just put one on right now while doing this mod.
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post #9 of 21 (permalink) Old 05-07-2009, 07:45 PM
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Originally Posted by p3t3rc View Post
what about just an after market filter? i was thinking if i should just put one on right now while doing this mod.

ehh...
you should be ok

But def look into the filter before you get it...
I personally was planning on getting an aftermarket filter (street version since im not tracking until next year) and now im staying with the OEM for the better filtration... just a heads up :01_thumbu

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post #10 of 21 (permalink) Old 05-07-2009, 08:03 PM
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Ideally, according to many "experts", the perfect Air/Fuel ratio is 14.7/1 More air and less fuel than that and you are heading in to the lean area, which does make more power, but runs hotter. If you take those ratios to extreme, you risk burning a hole in the top of a piston(s). If you take it the other way, you are running rich. Take it to extremes and you lose power, run cooler, and blow out black smoke like a diesel truck........well maybe not like a diesel, but you get the point. A/F ratios are what is trying to be acheived when someone puts an aftermarket exhaust AND a Power Commander on their bike and then has it dynoed. The person running the dyno can adjust the A/F ratios at at 250 RPM increments, all the way up to redline/rev-limiter. If the tuner knows what he or she is doing, you can get a map that is very close to optimal for your bike, exhaust, elevation, etc. A/F ratios are not something to fool around with (on a Powercommander) unless you know exactly what you are doing, unless you are looking for engine trouble. Hope this clarifies it a little bit.

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post #11 of 21 (permalink) Old 05-07-2009, 08:06 PM
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Yes! Technical time.

To run an engine lean is to have an A/F ratio that is Air-biased, so anywhere from 51/49 and ascending (whereas Air is the primary). A lean mixture can yield a more OR less powerful combustion, depending on how lean you are running. Lean engines typically run hotter, burn A/F mixtures more thoroughly, leave less carbon deposits and expell less emissions. Technically, a lean engine will run MUCH smoother than a rich engine but it will also overheat MUCH faster. However, the downside is that it is almost impossible to detect cylinder head temperature changes without a manifold-mounted EGT sensor. If you don't detect changes in temperature and immediately correct the problem then you'll run into major problems, mainly consisting of burning pistons (almost instantly), rings, cylinder and even the cylinder head, if you leave a lean engine running for too long.

To run an engine rich is to have an A/F ratio that is Fuel-biased, so anywhere from 49/51 and descending (whereas Air is still the primary). Too rich of a mixture will lead to premature carbon deposits (which will directly affect ignition function), sluggish power delivery and, in worst case scenarios, cylinder wall scorching. However, with today's EFI systems, the worst that will generally happen is carbon deposits, sluggish power delivery and progressive cylinder/cylinder wall washing.

Anyways, for a typical engine (one that doesn't get rebuilt often) a good A/F curve is one that is slightly rich while at idle, slightly lean throughout the power band and then again to the slightly rich side just before peak power is made up until rotational limits of the engine's design. The variance should usually be no more than +/- 3-7% between the two A/F ratio extremes, depending on your style of driving.

Now, you can get away with running a lean engine ALL the time if you have a proper cooling system and proper electronics to ensure your engine can vary A/F ratios depending on EGT at the manifold at any given moment. But I wouldn't really suggest looking into it.



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post #12 of 21 (permalink) Old 05-08-2009, 04:53 AM Thread Starter
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thanks guys for answering all the questions i had.. i know know the pros and cons of rich and lean.. after reading what you guys had to say.. im going to wait on the after market filter until i can get a better grasp on the air/fuel ratio or until i can pony up for a PC. thanks again.
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post #13 of 21 (permalink) Old 05-11-2009, 10:53 PM
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asfd

How "bad" is it to run a full exhaust with no PC on your bike? I dont have a pc, but i have a full exhaust sitting in my garage begging me to install it, but it will probably be a few weeks before i can cough up 300 bucks for a pc3...this is on an 06 600rr, with no other performance mods btw

thanks
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post #14 of 21 (permalink) Old 05-11-2009, 11:11 PM Thread Starter
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from what i read i think it wouldnt be good for your bike. but i can be wrong.
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post #15 of 21 (permalink) Old 05-11-2009, 11:47 PM
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Quote:
Originally Posted by renix01 View Post
How "bad" is it to run a full exhaust with no PC on your bike? I dont have a pc, but i have a full exhaust sitting in my garage begging me to install it, but it will probably be a few weeks before i can cough up 300 bucks for a pc3...this is on an 06 600rr, with no other performance mods btw

thanks

i would wait the few weeks until you can have the pc. With or w/o other mods, its not like its gonna cut seconds of your time... if you even track it.

I personally waited about a month until I could get my bazzaz and install it and I will be getting my headers in on Wed. I used the time to prep the bike for the install and even got other mods done.

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post #16 of 21 (permalink) Old 05-11-2009, 11:58 PM Thread Starter
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Struck how do you like your bazzaz? and how do you go about tuning your moto?


Quote:
Originally Posted by struckbylitenin View Post
i would wait the few weeks until you can have the pc. With or w/o other mods, its not like its gonna cut seconds of your time... if you even track it.

I personally waited about a month until I could get my bazzaz and install it and I will be getting my headers in on Wed. I used the time to prep the bike for the install and even got other mods done.
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post #17 of 21 (permalink) Old 05-12-2009, 12:06 AM
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Struck how do you like your bazzaz? and how do you go about tuning your moto?
I only got to do a couple short rides so far with the bazzaz to make sure it was working properly. I DID notice that with the map it came with and only a slipon it was a lil too rich.
Since on Wed. my headers will be coming in, I've obtained a couple maps from members to get by until I have the AFM (which im also ordering on Wed.).
The AFM is the bazzaz self-tune unit which i'll be using to create my own maps and even combine with other maps...

This weekend I should have everything prepared and have enough time to really test it all.

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Last edited by struckbylitenin; 05-12-2009 at 12:08 AM.
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post #18 of 21 (permalink) Old 05-12-2009, 12:09 AM Thread Starter
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let me know how it goes.. i plan on getting an FS exhaust..
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post #19 of 21 (permalink) Old 05-13-2009, 04:37 PM
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This thread is why people should take their bikes to a knowledgeable tuner... I'm not even going to bother quoting people and correcting them as it would take all day. Lean and rich is related to the air/fuel ratio (AFR). Stoichiometric AFR for gasoline is 14.7. 14.7 grams mass of air to 1 gram mass fuel. Anything higher is "lean". Anything lower is "rich". None of this 51/49 parts crap as it isn't true. It has to do with the amount of oxygen needed to "theoretically" completely combust the amount of fuel. It is completely theoretical as complete combustion is impossible. Gasoline cars attempt to run at stoichiometric AFR solely because their is a very narrow AFR range a three-way catalyst can operate in and allow a car to pass the EPA's emissions standards. Another benefit is it allows car manufacturers to use the cheaper "switching" EGO sensors. It is not optimal for power or fuel economy...

Optimal AFR for fuel economy is predicted to be around 13.1. This means it is rich. This also means that there are unburnt hydrocarbons and carbon monoxide (CO) as there was not enough oxygen to complete the combustion process and turn CO into carbon dioxide (CO2). Another benefit of running rich is it has a cooling effect on the in-cylinder gas which helps prevent knock. Compare the compression ratio of a 600rr to a production gasoline engine. A Subaru engine has a compression ratio of 8.2:1. (This is actually a little low as it has a turbo but Honda's cars are considered high around 9.5:1.) A 600rr is greater than 12:1. Higher compression ratio increases power but also increases knock meaning more fuel is needed. Due to variances in UEGO sensors, the optimal AFR for power may vary from the reading on the UEGO. This is why you take it to get tuned.

No need to talk about direct injection/HCCI/low-temp combustion as this engine wasn't built for it... The typical AFR values go out the window for these though FYI.
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post #20 of 21 (permalink) Old 05-13-2009, 05:27 PM
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I used the 50/50 because if he's asking he's not going to going to understand 14.7 gma over gmf. That's a theoretical target, anyway, because it's based on pure fuel (nothing more than n-heptane and iso-octane) which you will never get in your tank. There are too many variables to nail down a perfect A/F ratio (like amounts of alkane, octane, detergents and any oxygenators). All of those variables alter the 'stoichiometric' ratio. Fuel with too much methyl tert-butyl ether can have an 'optimal' ratio of almost 14.0 gma over gmf, flat. A 'stoichiometric' ratio only applies to light loads (read: constant) anyways. As soon as load (however you want to interpret the word) is introduced into the equation the 'ideal' ratio goes out the window. A three-way catalyst can be run in both open- and closed-loop. From a smog POV it works better in a closed-loop because all three parts (NOx, CO and HC) are diminished at equal values. Running a three-way open-loop changes those values to be favorable to CO and HC, but not so much NOx, but strictly from a comparative volume POV.

You can also combat knock with certain cooling strategies, so you can technically run lean (within reason) all the time.



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post #21 of 21 (permalink) Old 05-13-2009, 05:46 PM
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Quote:
Originally Posted by E-NA6CE View Post
I used the 50/50 because if he's asking he's not going to going to understand 14.7 gma over gmf. That's a theoretical target, anyway, because it's based on pure fuel (nothing more than n-heptane and iso-octane) which you will never get in your tank. There are too many variables to nail down a perfect A/F ratio (like amounts of alkane, octane, detergents and any oxygenators). All of those variables alter the 'stoichiometric' ratio. Fuel with too much methyl tert-butyl ether can have an 'optimal' ratio of almost 14.0 gma over gmf, flat. A 'stoichiometric' ratio only applies to light loads (read: constant) anyways. As soon as load (however you want to interpret the word) is introduced into the equation the 'ideal' ratio goes out the window. A three-way catalyst can be run in both open- and closed-loop. From a smog POV it works better in a closed-loop because all three parts (NOx, CO and HC) are diminished at equal values. Running a three-way open-loop changes those values to be favorable to CO and HC, but not so much NOx, but strictly from a comparative volume POV.

You can also combat knock with certain cooling strategies, so you can technically run lean (within reason) all the time.
For pump gasoline, stoichiometric AFR is 14.7. Ask anyone in the auto industry and they will tell you 14.7. I don't know how someone could not understand 14.7 g air / 1 g fuel. It is pretty easy and a lot more accurate than 50/50. The only time we worry about fuel blends is for research purposes and even then we assume it is 14.7. That is the open loop target and we allow the EGO sensor to switch around the "true" stoich value. I don't think he is doing research so I don't see the point in bringing up specific fuel properties.... Telling him 14.7 also allows him to use a wideband that shows a value around 13 and know what it means. It also doesn't tell someone to plug in 1 for the AFR on the autotune or bazzaz mapping systems.

The "ideal" ratio is always present. Whether it is achieved or not depends on the fuel control strategy. At high load, car manufacturers will run rich for cooling reasons. I am not sure if that is what you were referring to? Running an engine in open-loop is stupid. No one in the car industry does it unless the EGO sensor fails. That is why bike manufacturers are converting to a closed-loop system with the increasingly strict emissions standards being introduced. Whether it is running lean or rich in open loop mode depends entirely on the open loop map. It is safer to run rich though...

Once again, these engines do not have sufficient cooling to run lean. They are designed to run rich for cooling reasons, knock prevention, and maximum power.
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