Dyno Test: July 2, 1999

Dyno Test
Paradise Garage

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Woodbridge Dynotech, Woodbridge, Va.

Test Session: Friday, July 2, 1999

Last time our 1998 Pontiac Firebird Formula saw a dyno, it was turning 288 hp stone stock. And while "almost 300 hp" sounds good, "over 300 hp" sounds a lot better. We'd read extensively that the stock airbox is a point of restriction, so we replaced it with a new airbox from Modern Street & Race in the hope of finding that elusive 12 horsepower.

Take a look at 130 mph in 4th gear.

But one thing we don't trust the the old SOTP Meter (Seat O' The Pants). We arranged for some time on a dynomometer at Woodbridge Dynotech. John Sealock, the proprietor, did the honors.

We haven't made any mods at all to the Paradise Garage Firebird, but the first order of business was to doublecheck the baseline to make sure the car hadn't magically picked up any power over the ensuing 18,000 miles.

Well guess what. It did. It showed 291.4 hp, almost four more horsepower. And yes, these numbers are corrected. To make sure we weren't crazy, we tested it again and showed 291.1 hp. That's about as repeatable as it gets. So we don't know where the extra power came from. The original test, at 288 hp, was with 10,000 miles on the odometer -- it was broken in.

The new MS&R airbox.

For our next trick, we removed the stock airbox and replaced it with the unit from MS&R. We had two different filters for this thing: an Amsoil unit and a K&N unit. We started with the Amsoil filter, since that's the no-cost option. The K&N is an extra $26.

Results? 289.0 hp. What the heck??

We retested. 286.9 hp. It was odd that a more efficient airbox would cause a loss in horsepower. Torque was down too -- 304 and 308 lb-ft, from 311 and 315 previously. This was not good.

All right. We yanked the over-oiled Amsoil filter and put the K&N filter in its place. Amazingly, this helped a lot. We immediately saw 292.9 hp, a four horsepower gain over the Amsoil's best pull. Not bad for a filter. K&N, we're convinced. The backup run showed 291.8 hp. Still pretty good, and torque was back in line too with 309 and 310 lb-ft.

Of course, our net gain was 1.5 hp. Hardly persuasive. Where was the extra horsepower?

MS&R warned that the LS1 computer was going to need some time to learn its new parameters. Fair enough. We left Woodbridge Dynotech with a date for two weeks later.

* * 800 miles pass * *

If the computer hadn't relearned in 800 miles, it wasn't going to. John welcomed us back and we strapped the Firebird back on the dyno. A moment later we would know the deal once and for all...

290.9 hp. The computer didn't make a difference. The backup just confirmed it: 289.2 hp.

These were not quite the results we were expecting. We aren't really significantly closer to our goal of 300 hp, at least on a dyno. The airbox has another chance: on a track test. Since the airbox is designed to move air more efficiently, it could be that on a static test the box is just not able to utilize its design. This will reveal itself on the track, where the box has no excuses.

Our first test was pretty much an exercise in frustration. There were no useful results. But we backed it up with a second test and a third test. After all that testing we were able to find about a two-tenths gain with the new airbox. That's pretty darn good!