Intake porting options

[strokher racing]

Ok guys lets discuss the who, where, and why of the 3.2 intake. I am in a position, and I know several others are where it comes to wondering if the 3.2 intake in stock form is a restriction. Who has ported these intakes to get the most flow etc out of them. I know extrude hone is an option as well. Several well known shops speak about how unbalanced the runners are. I spoke with the headquarters not the extrude hone branch that screwed me and they pulled up some before and after flow numbers that looked promising if they are true. Has anyone heard of a shop that does extensive work on these etc? Lets see if we can find some extra flow to compliment everything else.

Eric

[1fastredsc]

From the little i've read here and there on this board over the year and a half here, carreras don't have to worry much when it comes to intake ports. It's only the late model SC's that have crappy intake port size (32mm).

[Randy Webb]

"porting the intake"

The intake ports flow very well. The intake manifold as I understand it is not well balanced. The soln today is to use the abrasive mud (ExtrudeHone) to equalize the tubes. Previously, I think people cut the tubes in half and did it by hand with a die grinder. There are numerous threads on all this, so use the search button and then post any specific questions. Also look at Rennlist. Steve Wiener has posted in one place or the other.

[jluetjen]

Eric;
After doing a lot of research on the subject of port design, I think that it might be helpful if you broaden your question a little. Here are some question that might help you in your considerations. I found these useful when looking at the carb'd and MFI'd engines, but I haven't spent that much time on the later common plenum engines.

1) cc to cc, is the stock Carrera engine less efficient then the stock SC's or the latter engines? More specifically, is the shape and the magnitude of the BMEP curve different for the two engines? In the case of varioram engines, you might want to look at the curve for the different intake configurations. If the curves are pretty similar, it might suggest that the intake design is not a big contributor to performance within the envelope of the the stock engine configurations.

2) There is more to intake design then just restriction.
a) There is tuning
b) There is full flow capability

Tuning: There are a number of factors here including length, shape, volume of the plenum chamber(s), cam design and exhaust design. You'll need to work through them all (starting with the cam and exhaust design (based on your desired rev range) to figure out which might be sub-optimal for what you are trying to do. These things will have a huge impact on the shape and magnitude of your engine's torque curve (and by extension the peak HP). Start reading up on organ pipe theory and keep your eyes open for the book "The Scientific Design of Intake and Exhaust Systems" by professor Phillip Smith. It's out of print but available on eBay or from Amazon. A. Graham Bell discusses it also in "4 Stroke Performance Tuning". He has a number of other books out such as a similar book on 2 Stroke tuning and another on Fuel Injection systems which I haven't read, but I suspect also expand on the subject.

Full Flow Capability This factor is a key in your engine's peak HP numbers, and to a lesser extent the shape of the torque curve. The key factors seem to be diameter, shape and finish of the intake. Other factors such as upstream components (throttle plates, metering systems) and downstream components (muffler design) also play a part.

911 motors are great for this sort of question since all of the different variations sharing the same factory's DIN spec dyno measurements allow a coorelation analysis to be done that can often lead to some interesting paths of investigation.

All of that being said, in general I doubt that the "blunt tool" of extrude honing is the best way to optimise all of these factors.

[Wavey]

From Steve Weiner:

"There are some relatively simple things you can do that to enhance performance on your Carrera. Here are a few:

1) Install a GOOD performance chip; they are not all the same.

2) Regrind your cams to the 964 profile. Your cams can be reprofiled by a few companies; We use Webcam. If you retain the Motronic system, stick with 964 cams.

3) Extrude-hone your intake manifolds. Leave your heads alone as they have plenty of airflow up to 340 HP. (930 heads are nowhere near as good as your Carrera ones)"

[strokher racing]

I will clear the question up a bit I have a 3.3 turbo with the 3.2 intake. What I am wondering is if anyone knows of a shop who has experience with extensive port work on the 3.2 manifold on an all out deal.

Eric

[DG624]

What about the throttle body and MAF system? They are part of the intake and should also be part of improving flow. Also will allowing more air through the filter box help? I have read stories where the intake side of the Motronic engine has more potential for improvement than the exhaust side.