Dyno Testing Results (1 February 1999)

The three cars had slightly different modifications and I think the results are very interesting.  First, below is the dyno sheet for my run.  Keep in mind that my only engine mods are K&N FIPK, A'PEXi Super AVC-R, Magnecore wires, and plugs regapped to .034.  Stock adjustable exhaust (in Sport mode), stock 9B turbos, stock fuel delivery, stock everything else.  The car had 68,000 miles on the odometer at the time of the test, last tune-up at 50k miles, Exxon 93 octane fuel, and the SAVC-R was set at 1.00 kg/cm^2 @ 72% BADC, which resulted in a short overboost to 1.05 kg/cm^2, then a steady 0.99-1.00 kg/cm^2 until 6000 rpm when power began to drop off (note: 1.000 kg/cm2 = .9804 bar = 0.9678 atmospheres). This run was made in fourth gear since it is closest to direct drive (.92 on the 6-speed Getrag).

The top line is the torque curve in Newton-meters (the vertical scale on the right) as measured by the dyno at the wheels during acceleration. The next line is the engine horsepower curve in kilowatts (the vertical scale on the left), which is computed from the torque curve using the familiar equation horsepower = torque x RPM / 5252. The next two lines are the wheel horsepower and drivetrain loss, also in kilowatts. Note that the drivetrain loss is computed from torque as measured by the dyno at the wheels during deceleration in gear with the clutch in, and this curve is subtracted from the computed flywheel horsepower curve to produce the horsepower curve at the wheels. The top lines were rendered left to right during acceleration and the bottom lines were rendered right to left during deceleration.

Then we have the lines of text. Can't read German? Neither can I, but Roger translated. Here's the scoop, complete with conversions into SAE units:

P-Norm is peak horsepower corrected to European DIN standards.  266 kW = 362 DIN PS = 367 SAE HP (conversion factors are 1.36 and 1.014, respectively).
P-Mot is the peak horsepower uncorrected.
P-Rad is the peak horsepower at the wheels.
P-Schlepp is the drivetrain loss at the peak horsepower RPM.
Maximale Leistung is the speed and RPM at which the peak horsepower was achieved (in fourth gear), 205 kph and 5680 rpm, respectively.
Drehmoment is the peak torque.  480 Nm = 354 lb-ft (conversion factor is .7375)
Maximales Drehmoment is the speed and RPM at which the peak torque was achieved (in fourth gear), 187 kph and 5180 rpm, respectively (note that torque was almost as high at as low as 3000 RPM)
Maximale Geschwindigkeit is the maximum speed achieved during the run, 220 kph
Maximale Drehzahl is the maximum RPM achieved during the run, 6090 rpm
Luftdruck is the ambiant atmospheric pressure, 989 mbar (about 1.02 kg/cm2)
Ansaugdruck is the intake pressure (not measured)
Abgasdruck is the exhaust pressure (not measured)
Lufttemperatur is the ambiant air temperature, 9 degrees Celsius
Oltemperatur is the maximum oil temperature during the run, 91 degrees Celsius
Abgastemperature is the exhaust temperature (not measured)

Also measured during this run was air/fuel ratio (A/F ranged from 11.4 - 13.0) and intake temperature at the intersection of the two Y-pipes (107.8 degrees Celsius maximum).

Observations:

1. A $450 boost controller and a $150 air intake system netted nearly 15% more horsepower!
2. The peak torque was produced at 5180 RPM, but this represents the tail end of a power band that started at under 3000 RPMs (ie- we saw 350 lb-ft of torque at 3000 RPM)!  The torque curve is wide and flat, which is why the car feels so strong and smooth.  Some modifications can result in higher peak power, but drivability may suffer.
3. No detonation was experienced.  In a subsequent run, the dyno was progammed to hold the car at 5700 RPM at WOT (the horsepower peak) while I changed the boost.  Any increase in boost over 1.00 kg/cm^2 resulted in less horsepower, indicating that the knock sensor was causing the ECU to retard the engine timing.
4. The injector duty cycle (IDC) maxed out by 6000 rpm, but the air-fuel ratio (A/F) was still between 11.4 and 13.0, so the mixture was not leaning out.
5. Why did power drop off after 6000 RPM?  Three ideas:
1. the stock 9B turbos are too small
2. the stock exhaust is too restrictive
3. the boost controller sensed that IDC was too high and reduced boost
6. Drivetrain loss was 30% at peak horsepower RPM!  It's amazing the car gets 23 MPG!

Mike Chapleski's 1995 Dodge Stealth R/T TT (U.S. Spec)
22K miles, FIPK, stock 9B turbos, stock 360cc injectors, Magnecore wires, .034 plug gap, DSBC @ 14 psi, Alamo DP, test pipe, Borla, Mobil 1 10W030 oil, Syncroshift in trans, ShockProof Heavy in xfer case, Centerforce DF clutch, 6-speed Getrag

Jim Matthews' 1994 Dodge Stealth R/T TT (U.S. Spec)
68K miles, FIPK, stock 9B turbos, stock 360cc injectors, Magnecore wires, .034 plug gap, SAVC-R @ 1.00 kg/cm^2, stock adjustable exhaust, Mobil 1 10W40 oil, ShockProof Light in trans, ShockProof Heavy in xfer case & diff, original stock clutch, 6-speed Getrag

Roger Gerl's 1993 Mitsubishi 3000GT VR-4 (Euro Spec)
5K miles, FIPK, stock 13G turbos, stock 440cc injectors, Magnecore wires, .034 plug gap, DSBC @ 14 psi, AFC, ATR DP/cat, Borla, original stock clutch, 5-speed Getrag

Here is the combined graph for all three cars:

Observations:

1. With precats in place, an aftermarket exhaust system (downpipe and cat-back) results in little to no horsepower increase when running boost pressure levels that the stock engine and fuel delivery system can support without detonation.  An exhaust system moves the torque curve higher in the RPM range, sacrificing torque in the lower RPMs where the car is driven most frequently and marginally extending torque into the RPMs where the stock injectors are already maxed out.
2. The bigger turbos and higher capacity fuel system on Roger's Euro-spec did not result in more peak horsepower but created a higher peak torque (around 4500 RPMs), and, had the tires on the car been rated for higher speeds, they probably would have extended the power curve into the upper RPM range.
3. Plug gap makes a difference.  On Mike's first run, his plugs were gapped to .04x.  Then he regapped his plugs to .034 and on his second run the car seemed stronger and resisted detonation.  Plug gap also affects EGTs.  On the drive down to Switzerland, Mike was seeing EGTs in the 975 degree range, but on the way back to Germany, he was seeing EGTs in the 925 degree range.

The night before Mike and I made this 250+ mile journey down Autobahn 5 from Frankfurt to Switzerland for dyno testing in Zurich I discovered that one of my front brake pads was completely worn down to the metal.  After much discussion and a call to Roger to verify that he had spare pads I could use when (if?) we made it, we decided that we would attempt the trip anyway and just avoid using the brakes!  We left early Sunday morning and I followed Mike down so that he could buffer any surprises.  Luckily, the Autobahn was very clear that morning and while I did use the parking brake a few times, I only had to touch the brake pedal one time! Our average speed on this trip was still nearly 130 mph; I got up the nerve to take this shot as we slowed upon approaching a merge area. When we arrived in Zurich, my rotor was still in good shape and Roger's Euro-spec pads fit without any problem.