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© 1998-1999 Brian F. Schreurs
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Woodbridge DynoTech, Woodbridge, Va.

Test Session: Monday, December 7, 1998

To get a better idea, I took the Paradise Garage 1998 Pontiac Firebird Formula to Woodbridge DynoTech to be strapped onto a DynoJet inertial dynamometer. This device measures horsepower delivered to the rear wheels by making the car spin two 1600 lb drums through the car's rpm band.

Everybody at DynoTech was very friendly and helpful. They seemed as interested in running the Firebird as I was. John, the proprietor and "Dyno Master," patiently answered all my questions and ran his shop professionally.

It takes a lot of straps to hold back almost 300 horsepower. No one wanted to drive through the shop wall.

I drove the Firebird into the bay with the DynoJet, parking it so the rear wheels were resting on the dyno's drums. The DynoTech crew secured my Firebird with thick three-inch nylon straps attached to steel brackets mounted in the concrete floor. On the front, the straps were wrapped around the points where the anti-sway bar attaches to the frame. On the rear, two straps were wrapped around the axle housing and two were cross-strapped to frame points. Huge metal ratchet cinches made sure that all the straps were tight.

They also clipped inductive pickups to the LS1's #1 spark plug wire -- no small feat considering the two-inch-long wires. This allowed the DynoJet software to read engine rpm.

John set up the DynoJet software for the car and weather conditions. The weather conditions are particularly important, as it allows the computer to calculate corrected horsepower, which is the only number truly useful for comparison purposes.

Then John got into the Firebird with a two-button remote for the computer and "drove" the car to fourth gear (the correct gear for a five- or six-speed manual; a four-speed automatic would have used third gear) where he punched the computer's "go" button and the Firebird's "go" pedal in rapid succession.

WWWWWHHHHHHHEEEEEEEOOOOOOOOOOWWWWWW

No matter how good you think your car sounds from the driver's seat, trust me, it sounds way better from the outside! It's a rush to listen to your own engine, right next to you, run from a leisurely 1800 rpm to a screaming 6000.

Dynos don't lie: We lay it on the line.

The numbers came in and the Firebird saw a measured 283.8 hp, which with the CF of 0.99 equals a corrected 282.4 rear wheel hp. Applying the traditional 15% drivetrain loss puts this engine at about 335 hp, far more than the advertised 305!

The next two runs fared even better -- apparently the LS1 responds well to being warm. Although the first run was conducted at normal operating temperature, the following runs were somewhat warmer, slightly over 200 degrees. They resulted in corrected 286.9 and 287.6 hp!

Torque remained strong as well, peaking at a measured 310.4 and a corrected 309.4 lb-ft.

Over the next couple of days, some doubts arose as to the repeatability of the inertial dynamometer. To prove their consistency, I teamed with Woodbridge DynoTech to re-test the Firebird without any mods. Two days later we met again.

The weather was 20 degrees cooler so it would be a bit of a challenge for the computer; if they couldn't make the appropriate corrections, the numbers would be way off. We put the Firebird back on the rollers and it screamed to redline all over again.

It ran a measured 298.9 horsepower! This demonstrates how critical it is to use corrected numbers. The weather greatly affects the output of an engine. But, when the computer made corrections for weather (using a new CF of 0.94), it lined up right at 281.6 hp, within three- tenths of one percent accuracy when compared to the first run made at the same engine temperature. That should be good enough for almost anyone.

According to the various formulas for calculating trap speed based on rwhp, the Firebird should be running a bit faster than it is. This spring I'll be perfecting my technique so we'll see whether experience can dramatically improve times!