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.
Who's really the fastest?Since SoCal R32 and HPA had rented out the Streets of Willow for the track portion of their shindig, we tagged along to do some quarter-mile testing and hot laps on the same day. Being the control Nazi that I am, we again arranged for everyone to be on the same pump gas as on the dyno day. For added assurance, we also slapped the same Dunlop SP Sport Maxx max grip summer tires on each and brought along our own drivers for the quarter mile and the track. We knew who made the most power, and know that NA cars suffered more at altitude than the types of forced induction cars we were testing. So what does our radar gun tell us? The NA car, at a roughly 40-whp disadvantage and at best a 200-pound weight advantage (no back seat or forced induction hardware) pulled off the fastest e.t., almost a tenth faster than the best runs by the forced induction cars.
Yeah, that's what I said. And since our driver, John Kiewicz, quarter-mile jockey of our sister publication Motor Trend, has unquestionable driving abilities, and each car used the same gas, the same tires and the same infallible radar gun, we were left with the verdict that heat and weight make a big difference. Considering it was only 73 degrees outside at 20% humidity, I'd hate to see what a real summer track session would do to these cars. By the time Kiewicz shifted into third on the quarter mile pull in each force-fed car, the effects of heat and knock could already be felt. We even let the non-intercooled turbo car have a lengthy cool down time for the benefit of the doubt so that it could post its best e.t. of 14 seconds even-almost three tenths faster than its hot runs-to make sure the thin air had not gotten to all of us.
Apply all the correction factors you want, but like the cop said, radar doesn't lie. I will point out for reference's sake that the stock R32 we tested that day under-performed compared to Motor Trend's stock NHRA elevation-corrected e.t. by 0.4 seconds. Next time I'll make sure to datalog each car's OBD-II output to better report what each car is doing down the quarter mile. Yeah right, I'd be working for a race team and not a magazine if that were the case.
Point for the NA car without back seats and its lightning-fast short shifter and flywheel.
Settling The Matter Like Real MenWith no solid answers, we took the battle to the Streets of Willow in its full 1.7-mile configuration with a coned-off chicane on the straight after turn eight. With James Hickerson of Eibach Springs as our hot shoe, we ripped off some timed hot laps to see which form of power delivery best fit the track. We gave each car five timed laps total, including warm-up and cool-down, but it was pretty clear that by lap three the brakes were cooked and the compressors were blowing hot air.
Probably the biggest difference between the cars was suspension setup, which wasn't our main concern in testing. Wheel travel was the key to fast times, and keeping all four contact patches well planted. Unfortunately, the slower R32s all rode too low and could not take advantage of the grip offered by the SP Sport Maxx tires. The quick-boosting turbo car stood out here, with its on/off throttle steering and aptly tuned suspension. Even the supercharged car, fitted with the Neuspeed/Haldex performance upgrade, couldn't make up for the instant torque advantage enjoyed by the turbo car in the tight corners of the Streets.
Point for the turbo car with its instant torque and broad powerband.
Poring Over The DataWith nothing conclusive, we probably have the best results we could hoped for. Each car came away showing off its own unique strengths and weaknesses, and no one really walked away a loser. I spent the better part of a week scanning the data, burying myself in old thermodynamics and turbomachinery text books, consulting MAHA along with various turbo gurus, and scouring the Internet for NHRA correction factors and meteorological data to offer the best explanation I can. I still have none. So, I'll leave you with the numbers to sort out among yourselves.
|CAR ||E.T. ||TRAP ||ELEVATION CORRECTED SEA-LEVEL E.T. ||ELEVATION CORRECTED SEA-LEVEL TRAP ||0-60 ||LAP |
|Motor Trend Tested (Fontana, CA; 1232 ft) ||14.2 ||97.6 ||14.02 ||98.86 ||5.9 ||n/a |
stock(Rosamond, CA; 2326 ft)
|14.81 ||92.25 ||14.41 ||94.86 ||6.65 ||1'39"64 |
|VF ||14.06 ||96.21 ||13.68 ||98.93 ||5.72 ||1 '37"40 |
|HPA ||14.00 ||100.98 ||13.62 ||103.34 ||5.81 ||1 '36"01 |