It's tests like this that makes me wonder why we bother with testing at all. It took an entire sleepless weekend of running all over the Southern California with the guys of Advanced Motorsport Solutions (AMS), HPA, SoCal R32 and VF Engineering to test four R32s and we still came out with results I can't completely explain. At least this will give the Internet forum junkies material for months of discussion and argument. Whatever the case, our radar an timers don't lie.
When SoCal R32's Eugene Lee told us he had rounded up 108 of VW's top gun R32s for one event, we jumped on the opportunity to test what we thought were some reasonable examples of modified R32s: one supercharged, one turbocharged and one modified naturally aspirated (NA), all owned by R32 enthusiasts. The operative word is reasonable, so we left out the cars running stage 29 twin-charged kits with anti-lag. We ran the cars on the dyno, drag strip and at the track to see which power-adding setup we liked best and what really made for a faster car. Each R32 was tested back to back along with a stock car for reference. Interestingly, the results reinforce the strengths and weaknesses of the different methods of forced induction and NA tuning.
Dyno QueensThe first bit in any automotive mud slinging competition is how much power you make. Not that peak power really tells you how fast a car is, but it's an easy figure to throw out there for simple comparisons. It's the powerband and delivery that really matters. Sadly, you don't see too many forum discussions trading PDFs of dyno charts, but hey, dyno time can be costly.
Even on the dyno, you'd think getting a horsepower number is a pretty straightforward process. This really isn't the case, as every dyno has a different calibration and method of measurement. How much airflow the fans supply and how much cooling time the cars are allowed also make a huge difference, not to mention most cars run different brands of gas (even if it is all pump gas). Making a fair, apples-to-apples test has long been a dilemma. The only way to have dyno results that make sense is to record as much information and control as many variables as possible. Luckily, with only four cars this is a little bit easier.
We jumped on the last minute opportunity to use AMS's MAHA LPS 3000 awd eddy current dyno. This is one of two units in the U.S. (the other owned by Brabus Newport Beach) and has the most user-friendly whistles and bells I've seen. The LPS 3000 even has a OBD-II plug to allow the user to log four channels from the vehicle's ECU, along with additional channels for wide-band A/F and boost, which helped us tremendously in determining if each car was running properly (i.e., spark, knock, fault modes). My favorite feature was the cooling fans that change with vehicle speed and supplied the appropriate airflow to the car being tested.
To level the playing field even more, we emptied the fuel tanks and filled them with our local 91 AKI excuse for gas before strapping each down. Each car had three passes to nail a peak horsepower number. It usually turned out to be the second run with the best numbers, as lubricants became less viscous and engines weren't yet heat soaked. The MAHA dyno also has a nifty feature that measures drivetrain drag right after each run as the car coasts down. Based on this drag, which takes into account all pertinent factors for each run, it generates a pretty accurate crank horsepower value. Using a DIN 70020 correction factor (a European equivalent to our SAE correction factor,) the stock car put down a calculated 238 bhp, two off the advertised 240 bhp. Accurate enough for me. If this nonsense of bragging about crank horsepower is your cup of tea, the MAHA calculated a peak 260, 321 and 289 bhp for the tuned NA, supercharged and turbocharged cars, respectively. The supercharger had a steady climbing boost curve that peaked at 6.54 psi @ 6480 rpm, and the turbo car consistently made more than 11.8 psi above 3000 rpm. The HPA kit could handle this much boost by using a head gasket that dropped the compression ratio to 8.5:1.
The MAHA also recorded ignition timing, A/F, intake air temperatures (IAT) and ambient air temperatures. Ambient temperatures for all runs were roughly 65 degrees Fahrenheit, and IAT as measured by the ECU hovered near 70. The VF supercharged car was the exception, as its IAT steadily rose to 86 degrees at the end of its run, not that 86 degrees is high for IAT. Since the stock R32 uses an IAT sensor that is integrated into the MAF, these measured values only indicate the temperature of the intake charge and not the temperature in the manifold after compression and intercooling.
Score one for the supercharger, its linear boost and linear powerband.