ScaryFast

My LS6 air to fuel ratio is showing 10:1 until about 4200 RPM, then it leans out to about 13:1 at the top of the RPM band (~6500). It could be even less than 10:1 at low RPM, but the graph is using 10 as the bottom point. This was with a sniffer in the tailpipe, not a wideband O2 in the collector.

I haven't had a chance to get it back on the dyno and retuned to fix this, how much damage am I going to do if I track it this weekend?

Please tell me it's fine.

Cobra4B

That sounds a bit fat in the mid-range. I run a AEM wideband in mine and only really check it at WOT on the straights to make sure I'm not going too lean. My car stays 12.2 - 12.3 when hot. I never really pay attention to lower RPM WOT but I do know it's richer.

geerookie

Just wasting gas. Nothing to worry about but leaning it out in the midrange will help off corner accelleration.

SouthernSon

I blew up my LS6 at VIR after a tune that 'transitioned' with a slight hesitation (read - barely perceptable detonation) around 4K rpm. The engine only last a couple of hours after the tune. Melted number 7 and destroyed everything in the engine except camshaft. Not only do you need a good AFR but the transitions need to be smooth. Find someone to tune it that knows what they are doing.

Han Solo

If you have cats you need to take all readings in front of them. Too rich can wash out the cylinder walls and dilute the oil. As said above it needs to be in the proper range and transition within that range.

I hear of people running their AFR at 11 to 1 saying they are using fuel to cool the combustion chamber all the time. I disagree with this method. It may cool the combustion chamber and prevent pre ignition with higher timing but it also dilutes the lubrication for the cylinders. For my money I would stay at 12 to 1 or 13 to 1 and run the timing as low as needed to prevent pre ignition.

ScaryFast

I know where I want it to be, it's a matter of getting it there. The slight complication is that it's a MAP only tune.

Here's the graph



I can get a tuner to mess with it tomorrow but not on a dyno. I am concerned that this is more risky than leaving it as it is for the weekend. I don't want to lean it out.

drivinhard

worst case if you leave it, you should be above 4800 most of the time anyway? and it's not horribly fat from 4800 on up

ScaryFast

I will short shift to save gas.

Nope, I will be keeping it in low RPM. See above

And thaks for assuaging my fears.

spectator2

I would be worried. Might even set the car on fire just to get rid of it!!

skyavonee

I would be worried mainly because you don't even know just how rich it's really running. It almost certainly goes below 10:1, but how far? The graph doesn't show it, so you don't know. Just my 2 cents...

Scooter70

I agree. Do you have a bung in the header? If not, can you put one there? I have a wideband that you can borrow if you have a place to install it.