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Discussion Starter #1
Hopefully a quick question: exactly how rich on an 848 is "too rich", i.e. so rich you might do some damage?

Check the attached dyno - running AFR between 12 and 13 after 7k, but below that it's pretty erratic between 10 and 12. Obviously that's rich, but is it so rich that it could be doing any damage (apart from the lower mileage hitting me in the back pocket)?

I've been running this ECU map for about 3500 miles, just FYI.
 

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Generally speaking, bring a bit on the rich side isn't going to do any damage as long as there is a good fuel burn. Most tuners will aim for slightly rich to help with cylinder cooling anyway. Lean condition is far worse because the cylinder heats up more with more risk for pre detonation.

Honestly, that graph is nowhere near acceptable. The AFR should be pretty much flat all the way across. The little peaks at 5k rpm down to almost 10 and big peak up to almost 14 at peak, these are not good and could also be felt when riding the bike.

As a reference, this is what a proper dyno should look like in the AFR department. Look at the blue line, notice there are no spikes, its pretty much flat all the way across.

 

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The air/fuel ratio that maximizes power has been shown to be about 12:1 or 12.5:1 and is about 20% richer than stoichiometric (14.7:1). 14.7:1 usually yields exhaust CO levels of less than 1%. 12:1 give about 6% CO. 0.5% is a target for emission control, not for engine power.

Since engine power is air-limited (not fuel-limited), for maximum power, you want to use up all of the air that gets ingested by the engine. So you richen up the mixture until the best tradeoff between over-rich power 'loss' and air utilization gives you maximum power. So up to a certain point a richer mixture burns slower, but produces more power. There’s a fuel/air ratio for optimum flame speed. Too lean, it slows; too rich it slows.

I refer you to:
Heywood, John B., Internal Combustion Engine Fundamentals, McGraw-Hill, 1988, p. 395

According to Heywood:

Both flame development and burning angles show a minimum for slightly rich mixtures ([phi is approximately] 1.2) and increase significantly as the mixture becomes substantially leaner than stoichiometric. ... Faster burning engines (which have higher turbulence) are less sensitive to changes in mixture composition, pressure, and temperature than are slower burning engines (which have lower turbulence).

In other words, richer (up to a point) burns faster (smaller burn angle), not slower. The minimum burn time appears to be right around the max power air/fuel ratio (phi about 1.2).

See pages 402 to 403, particularly Figure 9-25 at the bottom of page 403. Keep in mind that the figure is for a laminar flame, and which is not exact for the turbulent flame typical in an engine, but it is a clue and a start and not a bad guess for guessing the effect of changing parameters.

That said, we find that generally peak power output comes at 4% CO.
 

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Good information. Shazzam.
 

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Discussion Starter #6
You know your Rich when your daily beater is a 911 Carrera...

Sorry, I couldn't resist :yo::yo::yo:
hahah. not bad!

but back to the original question - can anyone see a huge issue (i.e. imminent damage/danger) by running this map? i totally intend on chucking a PCV on it asap, but got this power run done first just to see where i was at.

given i'm between 11.5 & 13 most of the time, I can't see a huge issue (apart from a bit of carbon build-up and maybe some sooty plugs) - anyone beg to differ?
 

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The PCV won't do much, its far easier to simply map the stock ECU.

Run the bike the way it is until you can get the work done.
 

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Discussion Starter #8
The PCV won't do much, its far easier to simply map the stock ECU.

Run the bike the way it is until you can get the work done.
ok. should only be a couple weeks until the PCV arrives. sadly, no tuners around here can tune direct to the ECU. Piggyback is my only option unfortunately...

however, given i've removed the closed loop with this flash, what's the reasoning behind you saying "PCV wont do much"? I've seen flat AFR's using PC's - why do you expect it not to work here?
 

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I've watched many cars being tuned and several bikes including two recently using a PC5 and i can say that my tuner would laugh at your AFR Tuned. a PC5 can tune the AFR down to 100 rpm increments which is over kill for anything but a race bike. The PC5 autotune map we pulled off a harley vrod last week was flatter then the one you posted.

Halcyononon - Don't freak out when you look at the installation instructions for the 848 evo on Power commanders website. you do not need the O2 expansion nor is it supposed to come in our kit. I talked to power commander guys about it a few months ago.
 

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Discussion Starter #10
I've watched many cars being tuned and several bikes including two recently using a PC5 and i can say that my tuner would laugh at your AFR Tuned. a PC5 can tune the AFR down to 100 rpm increments which is over kill for anything but a race bike. The PC5 autotune map we pulled off a harley vrod last week was flatter then the one you posted.

Halcyononon - Don't freak out when you look at the installation instructions for the 848 evo on Power commanders website. you do not need the O2 expansion nor is it supposed to come in our kit. I talked to power commander guys about it a few months ago.
haha, thanks dude. yeah, my current AFR is totally bogus. i'm not too concerned with the PCV install, more concerned with whether or not I could have any fuel wash after running this sort of AFR curve?

I've looked high and low all over the internet, but it appears no one can really say for sure as the AFR is dependent on so many other things.
 
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