Acceleration:

In total Tim made about seven acceleration runs, but one was thrown out since the mounting calibration run was too brief and the G-Tech didn't have it's attitude zeroed out. However, the remaining half-dozen acceleration runs gave plenty of data to poke and prod! As I alluded to before, the Prelude has an extremely high-revving four cylinder engine, with a power peak of 7000rpm stock and a redline of 8000rpm! Since it is also front-drive and has an open differential that made for a lot of entertaining launches. :)

Due to the difficult launch variables the Prelude's 0-60mph times varied between 7.8 and 8.1 seconds, and the unadjusted quarter mile times varied between between about 16.1 seconds at 90mph to 15.7 second, 92mph quarter mile. Most published figures for these cars put the 0-60 time in the 7.2-7.4 second range, but Tim's launches generally between a fairly soft launch and a limiter-bouncing smoky burnout through first gear. Nice work, Tim, you've cemented your place in the burnout gallery!

Power:

The most power recorded on the screaming Prelude was 141bhp @ 7150rpm, and the torque peak was about 115lb-ft @ 5500rpm. A stock Prelude motor is rated at 200bhp @ 7000rpm, and 156lb-ft of torque @ 5250rpm. As I started to pull the data off the G-Tech and CarChip OBD2 logger, I was absolutely astounded when I got to the atmospheric figures. Normally the intake air sensor reports air temperatures about 10 degrees elevated above ambient. In the case of a turbo motor like Eric's Saab, the temperatures can be 20-60 degrees higher. In this case the CarChip actually recorded intake temperatures that ranged from 37-60 degrees hotter, from a naturally aspirated motor!

The culprit in this case actually is the supposed cold air intake system that was in place when Tim bought his Prelude. Even though the intake filter is located as far away from the engine as possible, the open filter element essentially is sucking in very hot air, artificially robbing his engine of a lot of power! To calculate this I created two spreadsheets, one for an estimated temperature, and another given the theoretical output if he can replace the intake with one that isn't prone to heat soaking. The difference between the two is essentially 15 bhp, or about 6% loss! Given his current intake, the engine was only putting out about 186bhp, where if the intake were not so hot it should be putting out about 201bhp.

As I mentioned before, Tim had done some engine work but some of the parts were defective, and shortly thereafter his motor seized. By way of comparison the new motor and assorted bits show a clear increase in power over the old, and over a wide RPM range. This gives him an advantage of one or two tenths in (uncorrected) ET!

Technique:

Tim has got his work cut out for him launching the Prelude. Since his engine's torque peak is above 5000rpm, and the redline at 8000rpm, it's imperative that he launches with a lot of RPMs or it'll bog out. However, since his car is also front-drive and does not have a limited slip, just a bit too many RPMs and the tires disappear into a cloud of smoke. Literally! The first run he launched at about 5500rpm and an impressive amount of smoke resulted. Tim has driven this car at a drag strip, and he was unpleasantly surprised by how bumpy and slick the pavement at "Test Site North" is.

So, after the first wheelspin-fest Tim settled into another half-dozen runs to try and experiment with street launches. The quarter time times varied by .3 to .4 seconds, which is very significant, and even more the trap speed also varied by 1-2 mph! This is very unusual since normally trap speed is a factor of power and not how well you've launched. Since the Prelude is so much of a revvy motor, though, a poor launch dramatically affects how much power the car will put down.

To compare the launches the RPMs are key. When looking at this RPM launch comparison, you can see four very different launches Tim used. Too many RPMs resulted in massive wheelspin, while too few made the motor bog heavily. The two fastest runs were a moderate wheelspin launch and a very low wheelspin launch. Both runs actually were identical in RPM at the end of the rollout, but the rising RPM launch meant the wheels were unloaded by weight transfer so more wheelspin resulted. Treading a fine line between these two would likely yield the best launch. You can see the two moderate launches translate into a clear acceleration advantage.

Since the Prelude's VTEC timing profiles shift over at about 5250rpm, it's very important to keep the motor running in the high profile, so each shift should try to keep the RPMs at about 5400rpm or above. When you look at his shift points you can see that redline shifts are optimal for the 1st-2nd and 2nd-3rd shift, although the 3rd-4th shift should probably be at about 7600-7800rpm.

Corrections and Other Factors:

As I described before, since Tim's intake is letting hot engine-warmed air into his intake plenum I've made two correction spreadsheets for the current weather-corrected data as well as an optimal correction to show where he'd be if the intake temperature was normal. Since the G-Tech tests are a "run as ya brung" even, the actual corrected data will be the official figures:

	Recorded Data	Corrected Data
Optimal Case	0-1/4 mile in 15.7 secs @ 91 mph	0-1/4 mile in 14.8 secs @ 96 mph
Actual Data	0-1/4 mile in 15.7 secs @ 91 mph	0-1/4 mile in 15.2 secs @ 94 mph