Hi Everyone, It's "The Quick Cuban" from Excellence article April 2010.
I am normally on Renntech forum and have been missing in action from this forum, so my apologies... my name is Bill Diaz.
Just to clear up some of your questions. First off, thanks!, I am glad some of you enjoyed the Excellence article. I think it turned out very nice and I am very proud of it, but, do to space and some editor choices some things happened a little bit out of order in the article and some things were completely left out. I have to give Excellence magazine major thanks. Zachary Mayne the photographer and journalist was very professional and a really great guy. Amazing photographer too, you can see more of his photos of my car here:
http://www.qikqbnboxster.9f.com/photo.html
Pete Stout the editor was always very nice and encouraging. They run a great magazine and I have been a subscriber to 10 years now.
So, as you guys know, conversions are a labor of love and.... budget...
When the 3.4 liter was installed originally I added B&B sport headers to work with larger 3.4 liter exhaust ports, but decided to keep the stock cats. The stock cats were modified and larger piping was welded on to work with the headers and exhaust. I went this route at the time for a couple reasons..
1. Emissions
2. cost $$100 bucks to modify vs $1200 for Dansk hi flow cats.
3. sound
4. proper back pressure for low end torque.
Based on lots of research and also referring to the RuF 3400 exhaust system,
I decided to go with a 2004 Boxster S exhaust because the 5-6 hp increase in the upper rpm of some aftermarket exhausts were not worth some of the annoying sound resonance and loss of power and torque down low for city driving to me. It's all personal taste ofcourse, but I preferred to have a bit more torque down low for daily driving. Plus, I also got a steal on the Boxster S exhaust for $300 and aesthetically I wanted to add the 550 S split tip oval exhaust. It really is a great compromise of quiet cruising with a great scream once rpms hit 5000 rpm. Zachary Mayne was really impressed with the sound and almost everyone who drives it loves the way it sounds.
As far as the MAF is concerned. At the initial installation the original Boxster Air Box
was used although it was desnorkeled and had a K&N airfilter. The original Air Box uses a 3 inch Maf Housing. Because air travels faster through 3 inches vs 3.5 for the 996 maf housing the 996 ecu was being confused by the voltage signal and applying too much fuel. In hind sight I should have tracked the proper size 3.5 maf housing to begin with. I admit I had to Live and learn on that one.
As many of you already know, there are 2 ways to solve this Rich Air Fuel problem:
1. Use a "resistor" with 3 inch housing maf voltage line to "calibrate" the signal
2. Use a 3.5 inch Maf housing similar to the 996 original size.
I have tried both ways actually. i started with the Apexi Maf Air flow controller, which essentially is a variable electronic resistor that you can program from the seat of your car. I cut the stock Air Box out, but kept the original 3 inch maf housing and added a cone filter to the end of it. Using the Apexi maf signal controller we dialed in Air fuel ratios to be 12.5-13 AFR at wide open throttle. This tuning showed 270 hp and 234 lbs of torque at the wheels on a dynojet dyno.
just for comparisons here are dyno jet readings of 3.4 and 3.6 996's:
2001 911 3.4 liter Factory crank Horsepower 300 on the dyno = 252
Factory torque at crank is 258 on the dyno = 215
vehicle weight 3000 lbs.
2002 911 3.6 liter Factory crank Horsepower 320 on the dyno = 265
Factory torque at crank is 273 on the dyno = 228
vehicle weight 3100 lbs.
Bill's 1998 modified Boxster:
98 Boxster 3.4 liter approximate crank Horsepower 324 on the dyno= 270
torque at the crank 280 on the dyno = 234
vehicle weight 2700 lbs.
According to my Accellerometer tests my Boxster hits:
60 mph in 4.4 seconds
100 mph in 10.6 seconds
130 mph in 17.3 seconds
1/4 mile 12.8 @ 110 mph
These numbers are almost identical to the new Boxster Spyder.
Now, almost a year ago I switched out the Maf Housing for a 3.5 inch Cayman/Boxster S housing. So now I no longer really need the Apex voltage control unit. With the Cayman S Maf housing in place AFR's are between 12.5-13 without any voltage calibration. Excellence Magazine knew this, but they decided that the "voltage correction" made a more interesting story. So that is why they kept it in there.
The IPD intake is a definite plus for smoothing out mid to upper range power.
Most of the difference happens between 4-6000 rpm. 10-15 hp difference between 4500-5200 rpm. That is where its biggest gains are made.
As I said, hind sight is 20/20 and the proper size Maf is the way to go from the beginning. Can't say i did not have fun and learn a lot along the way though. if you have any other questions, fire away. As you can tell, I love talking Porsche
