AFR for most power

kavo · April 10th, 2014, 07:04 PM

Whats the best AFR for power on these motors? I had a 250 and when dynoed it produced most power at high 13 (13.5+) to low 14:1 ratios.

I have an auto tune set up and wondering what the best ratio for power is

DaBlue1 · April 10th, 2014, 08:15 PM

You may want to read this thread. https://www.ninjette.org/forums/show...8&postcount=17
https://www.ninjette.org/forums/show...9&postcount=28

Ryephile · April 10th, 2014, 08:17 PM

As a rule of thumb, peak torque is typically from 0.87 to 0.90 lambda. When talking in 100% gasoline speak where Stoich is 14.7:1, peak torque is usually 12.8 to 13.2:1. This of course depends on the combustion chamber shape, flame propagation speed, BSFC, VE, and a whole bunch of other factors.

Start with a 0.88 lambda target, and feel free to twiddle it a bit on the dyno to see where the sweet spot is at each programmable RPM cell in your Dynojet interface. Since you're tuning a naturally aspirated engine, it's unlikely you'll need to run any richer than 0.82 lambda or 12.0:1 AFR unless you're getting knock.

Good luck!

kavo · April 10th, 2014, 08:22 PM

Quote:

Originally Posted by DaBlue1

You may want to read this thread. https://www.ninjette.org/forums/show...8&postcount=17
https://www.ninjette.org/forums/show...9&postcount=28

Yes I was looking more for real world experience such as the second post

DaBlue1 · April 10th, 2014, 08:37 PM

Quote:

Originally Posted by kavo

Yes I was looking more for real world experience such as the second post

I just linked you to a couple of good single post. Here's the whole thing. Maybe it might be enough real world data for you.

https://www.ninjette.org/forums/show...618#post266618

Ryephile · April 10th, 2014, 08:40 PM

Remember to install your wideband sensor upstream of the catalytic converter if you're still running one or you won't get accurate O2 readings.

ninja250r81 · April 14th, 2014, 04:06 AM

o2 is only half of the tuning(not really other factors involved), you need to look at changing ignition timing aswell.

If the stock ECU can change the pre-programmed timing settings, if not have to look into ignition control.

Changing "o2" cleans up the hills and valley's and corrects the AFR, and a power increase or loss could occur.

April 10th, 2014, 07:04 PM	#1
kavo ninjette.org member Name: Mitch Location: Brisbane, AU Join Date: Feb 2012 Motorcycle(s): '10 Ninja 250 Racer Posts: 95	AFR for most power Whats the best AFR for power on these motors? I had a 250 and when dynoed it produced most power at high 13 (13.5+) to low 14:1 ratios. I have an auto tune set up and wondering what the best ratio for power is __________________________________________________ #77

April 10th, 2014, 08:17 PM	#3
Ryephile ninjette.org member Name: Ryan Location: Metro Detroit Join Date: Dec 2012 Motorcycle(s): '13 Ninja 300 :: Pearl White Posts: 37	As a rule of thumb, peak torque is typically from 0.87 to 0.90 lambda. When talking in 100% gasoline speak where Stoich is 14.7:1, peak torque is usually 12.8 to 13.2:1. This of course depends on the combustion chamber shape, flame propagation speed, BSFC, VE, and a whole bunch of other factors. Start with a 0.88 lambda target, and feel free to twiddle it a bit on the dyno to see where the sweet spot is at each programmable RPM cell in your Dynojet interface. Since you're tuning a naturally aspirated engine, it's unlikely you'll need to run any richer than 0.82 lambda or 12.0:1 AFR unless you're getting knock. Good luck! __________________________________________________

April 10th, 2014, 08:40 PM	#6
Ryephile ninjette.org member Name: Ryan Location: Metro Detroit Join Date: Dec 2012 Motorcycle(s): '13 Ninja 300 :: Pearl White Posts: 37	Remember to install your wideband sensor upstream of the catalytic converter if you're still running one or you won't get accurate O2 readings. __________________________________________________

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April 10th, 2014, 08:15 PM	#2
DaBlue1 Long Time Rider Name: Blue Location: Charlotte, NC Join Date: Sep 2010 Motorcycle(s): 2009 Kawasaki Ninja 250R Posts: A lot.	You may want to read this thread. https://www.ninjette.org/forums/show...8&postcount=17 https://www.ninjette.org/forums/show...9&postcount=28

April 14th, 2014, 04:06 AM	#7
ninja250r81 ninjette.org guru Name: scott Location: australia Join Date: Jan 2012 Motorcycle(s): 2012 ninja 250r se Posts: 435	o2 is only half of the tuning(not really other factors involved), you need to look at changing ignition timing aswell. If the stock ECU can change the pre-programmed timing settings, if not have to look into ignition control. Changing "o2" cleans up the hills and valley's and corrects the AFR, and a power increase or loss could occur.