I'm installing a Wideband O2 and wanting to lean the AFR in some areas. So, when is lean too lean that it may cause valves to burn? Does anyone have any ideas? 15:1 , 16:1 , 17:1?? (Under normal driving conditions.) .

 

I am by NO means anything other than a novice on the subject, but from the myriad of threads I have read on the subject, it seems as if anything much above 15:1 is a REAL bad thing. Again, if memory serves, it seems like most generally try to get somewhere between 12.5:1 - 13.5:1 for safety's sake.

 

I can see by your mods you are not a "normal driver". Go get help with somebody familiar with your new lamba and ecu and tune it on o dyno or you will have a pile of shrapnel. You could lean out to 14:1 at cruising, but under power 12:1 or lower is better. There is not a lot of room for adjustment with these high rpm's and boost. You've already spent a lot of money on your ride; this is not now the time to cheap out. Hope you get into the 12's!

 

According to my supercharger book, try to keep the A/F ratio 13:1 or slightly richer than that for all around good power and safety. However considering our car's compression try to get the ratio close to 12:1 on top end.
I think under partial throttle(is this when you meant normal driving?), you shouldn't still lean more than 14:1

 

Randy is on track here.

First, I assume you'll be measuring A/F before the catalytic converter. Measuring after creates some error (not huge, but if you're trying to tune precisely....).

At WOT on a NA car, you want to shoot for ratios in the 13.5:1 range. Some cars like a little less, some a little more fuel. As a reference, the Mugen ECU creates ratios in the 13.5:1 range.

On an FI car, 13:1 is the absolute maximum that I tune for on a street car unless a customer tells me he wants to go leaner. I shoot for an even richer mixture if I can't control ignition timing. We tuned Team Hybrid's turbo car to a 12:1 ratio across most of the rpm range as he's running a little more boost (7.5 psi). Going to 12.5-13:1 will net you a touch more hp, but we're only talking a couple %.

I never want to see anything above 14:1 at WOT on a production car engine. With FI, even 14:1 is kind of scary to me.

UL

 

Thanks, for a the great feedback.

For Heavy load/VTEC conditions, I've started AFR around 12.5:1 - 13.5:1 more
Dyno time will determine the correct AFR under Load.

For highway driving light load, I'm just trying to get a feel for the good AFR(gas mileage).
Currently, highway gas mileage is around 21 miles per gallon. The FI is not even producing a boost yet.

I'll set the AFR to 14:1 and check the gas mileage. But, I don't won't to burn my valves. If I do burn the valves. It will be the excuse I need to do some really fun stuff.

 

[QUOTE]Originally posted by 1Randyc
[B]According to my supercharger book, try to keep the A/F ratio 13:1 or slightly richer than that for all around good power and safety.