deciding on target air fuel ratios
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racerxadam
- Posts: 7
- Joined: Mon Aug 19, 2002 2:56 pm
- Location: philly
- Contact:
deciding on target air fuel ratios
So hondata has the cool feature of being able to set a desired a/f ratio and then hook a wideband up and datalog the values according to different points on the map and then telling you how far off you are from your target. So my question is how do you decide on the target a/f values. There are area on the map that probably won't ever get used, such as, any value of pressure higher than 0 at 1000 rpm. Is it neccesary to have a target for these values? Should the transition just be smooth from 14.7-12.94 at 750mb and then smooth transition down to ~12 for pressure above a few psi? Has anyone else wondered this?
Re: deciding on target air fuel ratios
You can't just arbitrarily decide on an A/F... you can choose a starting target A/F and tune the vehicle to that, but the only way to find out what the best A/F is, is to put the car on a dyno and start trying different A/F ratios.
Usually, you want to tune the car to one A/F (ie. 13.2 for NA). Once the A/F is as flat as you can make it, see how much power it put down. Then add fuel across the board (say 2%) and make a power run. If it makes power, then keep adding fuel. Same goes in the other direction.. wherever it makes the most power, is wher eyou want the A/F to be.
And yes, you want the transition from part throttle (750mb) to WOT to be smooth.. a good way to see this is in the 2D map mode. Make sure that the lines are fairly parallel and not intersecting each other.
Usually, you want to tune the car to one A/F (ie. 13.2 for NA). Once the A/F is as flat as you can make it, see how much power it put down. Then add fuel across the board (say 2%) and make a power run. If it makes power, then keep adding fuel. Same goes in the other direction.. wherever it makes the most power, is wher eyou want the A/F to be.
And yes, you want the transition from part throttle (750mb) to WOT to be smooth.. a good way to see this is in the 2D map mode. Make sure that the lines are fairly parallel and not intersecting each other.
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turbocivicex
- Posts: 19
- Joined: Sun Aug 18, 2002 4:00 pm
- Location: Ellicott City, MD
Target A/F ratio
There's no problem putting a step in the A/F ratio. The main points are:
- use 14.7:1 at low and mid load if the ECU is set to run closed loop, otherwise the long term mixture adjustment will get out of hand.
- at WOT anywhere from 12.0 to 13.8 will give best power, you have to dyno to find out.
- under boost 12.0 - 12.5 is good, as most cars will run leaner under real driving conditions than on the dyno, so a little rich is good. Max power under boost is usually in the high 12s.
- don't worry too much about the A/F immediately after VTEC changeover, as it will usually spike leaner about 1 point
- use 14.7:1 at low and mid load if the ECU is set to run closed loop, otherwise the long term mixture adjustment will get out of hand.
- at WOT anywhere from 12.0 to 13.8 will give best power, you have to dyno to find out.
- under boost 12.0 - 12.5 is good, as most cars will run leaner under real driving conditions than on the dyno, so a little rich is good. Max power under boost is usually in the high 12s.
- don't worry too much about the A/F immediately after VTEC changeover, as it will usually spike leaner about 1 point
Hondata