I have a car going to dyno to test some different mufflers/straight pipes. I'll test this also with a stock muffler in place.

Based on previous experience with Porsche intake manifolds.. I'm betting this is a muffler. Any kind of overlap in the valves will produce intake noise.


B

Well i havent felt a decrease in power at all on my butt dyno but I do feel like ive gotten more power, especially in first gear... this could be placibo effect but if anything, i would say i had a gain.

Butt dyno would be off on the car I'm dyno'ing :) Removed upwards of 500lbs out it.. LOL



B

How in the heck did you remove that much weight? It must be just a shell.

You could call it that :) Another Boxster Spec car being built :) which is why I'll be dyno'ing different exhaust combo's. Straight pipes for large tracks and *some* kind of restriction for short tracks like Laguna or Sears.

http://www.boxsterspec.com/uploads/m...8492_thumb.jpg



B

Dang, what do you do for a speedo and Tach?

you should caption that picture with "Still havent found where that rattle is coming from"

It will have a dash :) (stock) one. To get the Heat/Ac unit out of the car.. pull the dash. The roll cage will pass through the dash.

Heat/Ac unit:

http://www.boxsterspec.com/uploads/m...8479_thumb.jpg



B

Are you going to do anything fancey to the dash now that its out like, cover it in leather or alcantera with body color'd stitching?

Rattle.. :LOL:

I drove it Sunday night.. it is actually VERY quiet for having ZERO sound deadening in the chassis.

http://www.boxsterspec.com/uploads/m...4244_thumb.jpg


http://www.boxsterspec.com/uploads/m...4268_thumb.jpg


B

For those of you following along at home.. this is what we are talking about:

http://www.boxsterspec.com/uploads/m...5033_thumb.jpg

Something else of note that we do to these cars: we install 996/BoxsterS oil coolers. They are nearly double the capacity.

B

Oil cooler differences: Stock 2.5 on left..

http://www.boxsterspec.com/uploads/m...9102_thumb.jpg


B

Oh man, you have to admire the engineering behind the boxster to be quiet without all the sound deading.

Is that oil cooler your talking about the oil cooler below the intake manifold?

Correct on the oil cooler. You can see it below the intake in the pic above.

The X51 oil cooler is nearly double the size of the BoxsterS cooler!!!


http://www.boxsterspec.com/uploads/m...1204146571.jpg


B

Interesting, Is there enough room under the manifold to fit the X51 oil cooler or would that be over kill for a boxster?

I don't believe it will fit :( The main difference between the Boxster and 996/997 intakes: the 996/997 is TALLER (they have more room) The runners are longer before it becomes "plenum" so they have more room to stack stuff on the top of the engine.

Porsche has a lot of engineers.. I only add the larger coolers to the early cars that will be tracked or DE'd.


B

Good deal, well let us know what happens with your dyno results.

This little box is most likely for noise abatement alone. It doesn't have the volume to make much of an impact on the pressure waves of the intake flow.

Here is what Porsche says about their tuned intake:

"The Boxster inherits its twin-resonance air induction system from the 911
Carrera. The system acts as a “resonance supercharger,” allowing the engine
to draw from higher velocity airflow at certain engine speeds. A crossover pipe
connects the individual air collector/resonance chambers for each cylinder bank.
A flap in the pipe remains closed from idle to about 3,100 rpm. When it opens,
each cylinder bank can draw from airflow “excited” by the resonance created by
alternating induction between all six cylinders. In essence, “dual resonance”
creates two induction paths for each cylinder. Below 3,000 rpm, the cylinders
draw air from a “short” path. From 3,000 rpm to about 5,100 rpm – when the
resonance flap opens – the cylinders draw from a long intake path, which
boosts torque. Above 5,100 rpm, the flap again closes to allow the cylinders
to draw intake air from a shorter intake path to boost horsepower at higher
engine speeds."

They don't address that little res. box specifically but others in this forum have removed it, dynoed and lost torque and HP. I gotta believe it is a small part of their tuned intake system. The GT3RS has 3 res. chambers. Somebody thinks they are important. It's sort of like tuning a subwoofer cabinet. You adjust cabinet volume, dampening and port size to maximize certain desired frequencies (or RPM's).

Does this make any sense to anyone or am I just a lone voice deep in left field??

The intake plenums and the tubes connecting them are definitely meant to help intake charging, both by changing tract length and pressure wave control. The little box doesn't have the same function.

Are you saying that other people on this forum have removed the little box and found a power reduction?

'Am I missing something here? Is the resonance box just a muffler to reduce intake noise or is it an important part of the factory tuned intake. With a properly tuned intake, sonic waves from the intake pulse combine with airflow to force charge the cylinders as much as 125% of airflow alone. Porsche has been tuning this for a long time to give us better top end power and that nice big fat torque curve that gets us out of corners quickly.

I don't know the answer to this, just raising the question. Tuning an intake/exhaust is a lot more like tuning a musical instrument than we realize. It would be disappointing to remove the res. box and get a narrowing of the torque curve and lose 10hp in the process. Faster good, Slower bad! Any Porsche racing techs in the know on this? '


I added a TTP intake which effectively deleted the muffler, at the same time I had the car chipped, so I dont know what effect the change in the intake alone had on the cars performance. When I dynoed it after the intake and chip combination, I picked up about 20hp, then picked up another few with headers on my 2.7. I have a photo of the intake tube at my website below my signature.

Ed

:cheers: