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Im reading a book on tuning Demon carbs. What should the fuel curve look like? 14.7:1 is ideal but max power is around 12:1. What should an ideal fuel curve look like? Whats the easiest way to find this out. Im thinking about getting an a/f ratio gauge and welding in a o2 sensor in one of my exhausts. Is there a better way to tune my carb? Im a total rookie when it comes to carb tuning and reading plugs.
Typically on a NA motor, 12.9-13.1:1 will yield max power. FI applications usually shoot in the mid 11's to keep everything cool. 14.7:1 is stoichiometric, and only good for part throttle cruise. Even then I'd go a little richer.
Typically on a NA motor, 12.9-13.1:1 will yield max power. FI applications usually shoot in the mid 11's to keep everything cool. 14.7:1 is stoichiometric, and only good for part throttle cruise. Even then I'd go a little richer.
So the A/F ratio should be the same from idle to wot? Do it flucuate throughout the rpm range?
So the A/F ratio should be the same from idle to wot? Does it flucuate throughout the rpm range?
The 14.7:1 A/F ratio is what you shoot for at idle and at a high vaccuum / light load cruise speed.
At WOT / max power you want to shoot for 12.5 A/F ratio.
Richer mixtures than 12:1 add cooling but subtract HP.
Perhaps Unchained's response makes some sense. It's a balancing act - like he said, 14.7 at cruise/part throttle, where you're not really loading the engine for acceleration or maintaining high speeds. As more throttle is put it (expecting the engine to accelerate or to maintain high speeds or loads), more fuel is needed to make more power.
Can someone recommend a good a/f ratio monitor that is not to expensive. Im assume i would have to weld a bung into the exhaust and run the headers dry during testing right?
www.innovatemotorsports.com is the website of the manufacturer.
You can get the LM-1 A/F meter with the O2 sensor right out of the Summit catalog.
Their about $ 350.00 And it has datalogging built in.
I also get the Aux Box unit that goes with it that lets you datalog 5 A/F and 5 other things like EGT, MAP, oil pressure, jet pump intake pressure, etc.
It's the best engine tuning tool I ever purchased.
I've got a brand new Innovate wide band with an extra cable I'll sell to you for $250 + shipping. I used it for 1 hour for a tune on the boat in the drive way. Everything is there. I can send you pics. Just PM me.
Corey
The Innovate system is a very good setup.
Normally leaner at idle say between 14:1 & 15:1
Richer at WOT between 12:1 & 13:1
Part throttle low load can be leaner...
BUT.... this is all dependent on the specific engine. Engines are like women, you've got to give them what makes them happy.