AFR Issue
 

This video explains a lot. I think some P cars need tuning and run rich from the factory. When I first did my 3.4 swap and dyno'd it was only putting down 246hp. The afrs were just like in this video, down in the 10's. The car ran great with no check engine lights but had plenty of safe room to tune. Many people don't listen but I suggest putting a real wide band afr gauge in your car and see what is really happening. I was able to pull just about 10-12% fuel out of my fuel curve and the car has been a blast to drive. I run my afr's between 12.5- 13:0 This is nothing new, my car has been with a fuel controller for years. I use the Apexi AFC. It splices into your maf and is simple to use. That being said you can also destroy your motor if you are not careful and know what your doing.

Moral of the story is get a wideband or durametric if you want to see what your car is doing and watch you intake air temps for all you guys with cold (hot) air intakes.




10/19/13 Porsche 996 Racecar Dyno, 287whp/253wtq, tuned AFR's ~ 13.0, X51 headers - YouTube

So how much power are you putting down now? You're running a cayman airbox and a BMW 540i MAF housing right?

Correct. The BMW mass air housing is the same as a Porsche one. I don't know what I am making at the wheels. I'm guessing about 280+. It feels real strong.

I'm in the same boat
Car feels way to slow for 3.4 I think
I'm considering this mod since your original post
Not sure if I have enough knowledge to do so, but hey I'm quick learner
Btw. How did You manage to squeeze 987 air box there?
Is your engine lowered?
Mine is not and looks like not enough space

The 987 airbox is a must. It does fit with the engine not lowered. I put mine in while the motor was in. It's a pain in the ass. Basically you have to cut off any extra plastic on the box and remove the intake manifold on that side. It was a lot of trial and error but it is the best intake for our car. If you decided to put a wide band 02 sensor and gauge in I can walk you through the setup and tuning. All the gear that I am using below.

Digital Wideband Air/Fuel Gauge

http://www.summitracing.com/parts/apx-401-a018?seid=srese1&gclid=CPvdh9KHkLwCFag7Ogod0zQA8g

Auto Meter® 20014 - Porsche Boxster 1997-2001 Single Steering Column Black Gauge Pod (For 2-1/16'' Gauges)

So you are pushing the AFRs to lean? Lean produces more power, but you run the risk of burning up the motor. Although, 13 doesn't seem that radical. Isn't stochiometric around 14/1? If so, you are below that level.

When I used to race motorcycles, the 2 stroke guys with money had an interesting way of seeing how lean they could get. They would lean out the jets until the pistons siezed, then they would go one step rich, perfect! But expensive.

I'm assuming you are not running a closed loop fuel injection system, because the O2 sensors at the exhaust will send a signal to the DME to correct for the programmed AFR. No amount of tweaking the MAF will give you a different AFR in a closed loop system, just a CEL for an over/under limit of fuel trims., or am I missing something.

Yes I am leaning out the mixture to a safe ratio. I'm on the factory ecu with a 996 program. The fuel controller on kicks in at a selected throttle point but like you said even at that there will be no adjustments until you really get on it and it goes into open loop.

Ah, so at some point the fuel management goes into open loop. That explains it. So these "$69 Miracle Chips that give you 60+ HP" ads are onto something, because all they are is a resistor that splices into the MAF and supposedly leans out the AFR at high loads?

car runs closed loop at part throttle/low load. uses narrow band 02 sensors to keep things at stoichiometric. once you go wot or are under high load (climbing a hill) the ecu goes open loop and just delivers fuel based on measured airflow. in these conditions it also richens the mix to control heating, etc.

the tuners can't touch the part throttle tune, but they can fiddle with things when the car goes open loop by leaning the mix a bit - saves gas, improves performance by running closer to stoichiometric.

oem wot afr isn't 10:1, however. insite measured it on his car in another thread and found 12:1 or something close to that. if you are getting 10:1 then something is up - car isn't metering airflow properly; ie, thinking that it is getting more air than it is. some quick math shows that the difference between a 74 mm and a 76 mm maf housing is 5%, enough to change afr from 12:1 to 11.4:1 ...

I've been chasing the rich properties for years. I have the correct sized Maf housing for a 996 flash. Who knows though? The 996 airbox has the Maf right on it and the. Directly into the throttlebody. It was calibrated for just this setup. Best explained here. I would never get the correct metering due to a complete different intake setup compared to a 996.
http://986forum.com/forums/performance-technical-chat/26073-996-maf-housing-diameter.html

yeah, you get into a whole wide world of crazy once you start trying to emulate the airflow conditions out of an oem 996 airbox. best to just keep it closed loop with a wideband 02 sensor and piggyback. how hard were the apexi maps to work with?

They are simple. Download a manual for one. I've been using these on other turbo cars since around 2000