MAF housing for 3.4 conversion not quite right

[galtenbaugh]

I have a 2000 Boxster that I've installed a 996 3.4L as a replacement for my blown 2.7L. I've been driving the car for a while now and I'm almost happy with the result but I have one last problem. For an intake I used a BMC Carbon airbox with a Cayman MAF housing epoxied to it, and then a series of 3.5" silicone elbows and tubes to the throttle body. I have a stock 2001 996 3.4 low emissions map from my dealer and an FVD Boxster 3.4L conversion map.

The problem I'm having with both maps is that the engine is running fairly rich at full throttle. I recently installed a wide-band AFR meter and and at less than full throttle, it seems to be running fine with the airfuel ratio bouncing around 13:1. At full throttle it runs at around 10.5:1. My first question is whether this can be damaging to the engine if I do a track weekend running at 10.5:1. At Texas World Speedway, I'll be a full throttle most of the time. My fear is that this much gas will wash the oil off the cylinder walls. What should the AFR be at full throttle? 12.5:1?

My second question is how can I fix this? I believe this is caused by the difference between the Cayman MAF housing venturi diameter of 82mm compared to the ID of the 996 at 85mm. That's about 7% difference in area? Has anyone else noticed this? I guess there are a few ways to fix it, reduce the voltage from the MAF by 7% or get a 85mm MAF housing, or ask FVD to adjust the map to account for the 7% difference.

Anyone have any ideas?

Thanks!

George

[Guest]

The cheapest way is to use a resistor. See my previous posts about my conversion. I'm sure you need a different value of the resistor.

Good luck

Sergiu