Intake plenum and 911 throttle body

[jb92563]

This is a great development by Ben with everyone's input suggestions.
More heads on a design can be better than one and the results will likely prove that out.

I am trying to get up to speed on this and figure out how to get the most out of this on my 01 S.
Also be great to summarize where we are with this design and testing results/impressions.

Q1) What is the primary objective of this part?

From what I have read the goal is to improve the aerodynamic flow of air into the engine, over the stock part, which should result in a greater Volume of air available for combustion, smoother airflow, quicker throttle response etc.

Q2) Has anyone calculated the current volume of air over an rpm range of the stock part as a baseline and compared it to the New design?

I think you could probably use the MAF readings on a Durametric to easily read those values.
Retaking those MAF/rpm readings with the new plenum will immediately tell whether an improvement has occurred with the new design.
This would be super easy to accomplish.

You should also be able to calculate air velocities to determine what you would need to do to make the greatest improvements. The Y shape should be better than a T if the diameters/volumes are consistent. Any change will increase or decrease airflow speed which will result in less than optimum results.

Q3) With the new improved air volume numbers one could calculate the amount of fuel required to make use of the extra air available and perhaps using the O2 sensors readings determine if the existing mappings are able to supply enough fuel to use all the available airflow. Again more calculations or observations of the sensors?

Once this is determined then you might get an idea whether an ECM remapping would be beneficial.

Q4) What are the current diameters of the plenum. What TB's will fit?
From reading Im seeing 76mm 997 TB and 83mm GT3 TB with 73mm being stock size for the 2.7L engine?

Q5) If you are fitting a bigger TB like 83mm wouldn't you want to increase diameters upstream including the airbox. Can GT3 parts for the upstream components be used or would it be custom?

What comes in must also be able to exit even faster so opening up the exhaust flow might also be part of the optimum tune.
In the case of cars with 4 cats removing the secondary cat has opened up the exhaust flow rate to help in that regard and the car can still pass emissions.

It would be nice to list the combinations tried so far and what the results were so we all don't have to go through the learning curve, and can get optimum results right away based on the amount of work we are willing to do, ie Just the Plenum vs Plenum & TB vs Plenum, TB and exhaust etc.

Perhaps you can edit Thread #1 to include all the latest info and results.

Kudo's on undertaking and documenting a cool sort-of open source development of a 986 part.

Looking forward to seeing the results posted.