987 v 986 Air box

[blue2000s]

Originally Posted by Brad Roberts

I do tune the cars that I have used this setup in, but I also believe that the stock ECU (no flash or tune) can easily adapt for this and headers.

This really is only slightly different from installing a cone filter setup.

Thoughts?

I have doubts. The DME uses the MAF to measure air speed. It needs to convert that speed to volume flow so it knows how much air the engine is injesting. The conversion calculation has to include the diameter of the MAF housing.

Increase the MAF housing without telling the DME and it thinks the airflow is lower than it really is. Same speed + larger area = more flow. And not a little difference, it's a 23% increase in area! Huge! I would be really surprised if there was some way the DME can compensate to that change.

It means Porsche would have had to allow for housing changes while programming and then figure out a way to double check the sensor. I don't see a system that can make the correction. You know how slow O2 sensors are, they aren't fast enough to make a meaningful correction. They are mostly used for steady state (cruising) corrections. And there is no MAP sensor to verify flow with a pressure measurement.

I bet when you do a tune, the car is running very lean to start, yes?

[Brad Roberts]

Thinking about this

[Brad Roberts]

Funny part? I run the cable cars with the MAF disconnected pretty regularly. The base map in the ecu is pretty damn good..

Still thinking. Everything you posted makes perfect sense. I understand what we are doing (I'm not using this on anything smaller than a 3.2) but I will in the future.

[blue2000s]

Originally Posted by Brad Roberts

Funny part? I run the cable cars with the MAF disconnected pretty regularly. The base map in the ecu is pretty damn good..

Still thinking. Everything you posted makes perfect sense. I understand what we are doing (I'm not using this on anything smaller than a 3.2) but I will in the future.

The base map with the MAF disconnected probably runs fuel metering off the throttle position sensor. So it's probably fine as long as you don't mess with the cylinder filling efficiency of the engine (very free flowing exhaust and intake) and you don't change the size of the throttle body. If you do those, it'll probably go lean again. But the non-MAF map is probably conservative to begin with so it might bring the fuel level to about right.

[Brad Roberts]

Correct. TPS metering. The throttle response is not as crisp when I have them disconnected.

I have seen multiple cars adapt upwards of 20hp with no computer change, knowing that we changed the plenum (after MAF changes)

Typing out loud

[blue2000s]

Originally Posted by Brad Roberts

Correct. TPS metering. The throttle response is not as crisp when I have them disconnected.

I have seen multiple cars adapt upwards of 20hp with no computer change, knowing that we changed the plenum (after MAF changes)

Typing out loud

With safe AFR's?

[Brad Roberts]

I'll install one of these on a stock 3.2 engine with headers with a before and after A/F readings. I have a gutted stripped 3.2 race car in the shop that will be easy to install one on. I'm pulling the engine this week anyway!


B

[blue2000s]

Originally Posted by Brad Roberts

I'll install one of these on a stock 3.2 engine with headers with a before and after A/F readings. I have a gutted stripped 3.2 race car in the shop that will be easy to install one on. I'm pulling the engine this week anyway!


B

That should be interesting. Hopefully it's interesting, anyway.

[Brad Roberts]

With safe AFR's?

Porsche runs these super lean anyway, but yes, more than safe.