[tom.pond]

Does any one know what the desired o2 level would be in a naturaly aspirated chrystler 318 is? I am trying to fine tune my a/f ratio for max power and efficency. Currently I am at 0.6% o2 on my gas analyzer. I feel this is lean, I thought of running rich of stoich., say 0.2% for a little more power. Any suggestions would be great, thanks.

[Marmot]

Originally Posted by tom.pond

Does any one know what the desired o2 level would be in a naturaly aspirated chrystler 318 is? I am trying to fine tune my a/f ratio for max power and efficency. Currently I am at 0.6% o2 on my gas analyzer. I feel this is lean, I thought of running rich of stoich., say 0.2% for a little more power. Any suggestions would be great, thanks.

Real life isn't very close to stoichiometric but it seems like you are pretty close to the theoretically correct point for economy. If you want power, sweeten the mix a bit more. If you have an EGT probe (ideally on each cylinder) you can fine tune it a bit easier and make sure you aren't running a couple of cylinders too rich or lean. Run at the power level you wish to tune for and lean the hottest cylinder to peak then enrichen to cool it down 50 degrees or so. That should be best power.

[tom.pond]

Thanks for the reply. Unfortunately my water cooled exhaust manifold wont allow for any thermocouples, so I wont be able to check out each cylinder very acurately, I guess a hand held pyrometer would be the best I can get. I think i will at least be able to check the differential between left bank to the right bank.

[Marmot]

Originally Posted by tom.pond

Thanks for the reply. Unfortunately my water cooled exhaust manifold wont allow for any thermocouples, so I wont be able to check out each cylinder very acurately, I guess a hand held pyrometer would be the best I can get. I think i will at least be able to check the differential between left bank to the right bank.

If you have a good tach, why not just run the boat under load at full throttle on smooth water and lean the mix until you see a drop in rpm then sweeten it up again until you can obtain the highest rpm. Go little past that point then back off less than you went beyond the peak rpm .... I hope that isn't as confusing as it reads.

The only risk in going too rich is wasting gas unless you go way overboard and start smoking black and carboning up the works. Look at your plugs to fine tune it over a longer period of time, they should look nice and chocolatey without soot or deposits. To get a good reading on them you have to run at full power and then stop the engine without idling for any time at all or it will soot them up and give you the wrong idea. Sorry if I am being too basic on this but just ignore the obvious.