Dynomax Cat-Back Exhaust System - The Frugal Formula

The Search For Cheap TPI Power Begins With A Dynomax Cat-Back Exhaust System For Our 1989 Firebird Formula

Steve Baur Nov 14, 2002 0 Comment(s)
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As speed enthusiasts, we are constantly searching for a greater thrill from our performance vehicles. Some of us can do this with a large bank account, while others accrue credit card balances or borrow from relatives. Some take the plunge and buy a new car that has good power to begin with. Most of us have been down these roads before, and now that we're a little older, hopefully we are a little wiser and practice more restraint with our finances. This doesn't mean that performance has to suffer though. It just takes a little more consumer education to get the best bargain for your money.

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That in mind, this author has started this personal project to accomplish just that. With smart decisions and a mild amount of money, I hope to find affordable performance in this third-gen 305 TPI Firebird. I'm shooting for a total investment of $10,000 including the price of the car, which has lightened my wallet by $3,000. That doesn't leave a lot of coin, but many of my friends and Internet acquaintances say it can be done. I've christened my baby Blue Thunder because it's blue, it's going to thunder, and if I can equip it with a laser-guided gatling gun like Roy Scheider's helicopter, then I might just be able to pick off some Fords for target practice. All joking aside, as time and personal funds permit, I will report to you whenever possible with pertinent updates, but it's premature to promise regular installments as Blue Thunder's engine and driveline is too old to be considered "project car reliable." Hey, if the engine or trans eats itself, all bets are off!

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Blue Thunder is a 1989 Formula equipped with a Tuned Port Injected 305 cubic-inch engine and a five-speed transmission. It has the G92 3.45-geared rear axle and about 130,000 miles on the odometer. For as long as possible, I intend to gain the aforementioned performance while running 87-octane pump gas. Blue Thunder serves as my daily driver that racks up over 110 miles per day, so gas pricing and fuel mileage are very important factors in this equation. Around the GMHTP office, we had heard that a higher-octane fuel will improve fuel economy but have never found this to be true, so I'll stick with the cheaper petroleum for now.

The car's high mileage makes engine longevity a question. Since it is a daily driver, I want to limit the amount of abuse it receives at the track, but will run the 305 until it dies. Judging from the baseline numbers, the mini-motor is still in pretty good shape though. With nothing more than a very dirty K&N filter, the car ran a best of 14.844 at 93.13 mph. Here are the four runs it made and what we did to get those times.

Baseline Performance
Run/Notes: 60' ET Trap Speed
1. Shift at 4500 2.265 14.992 91.78
2. Same 2.275 14.904 92.24
3. Shift at 5000 2.280 14.879 92.93
4. Same 2.310 14.844 93.13

Obviously there is improvement to be made in the 60-foot times, which should result in a better ET. On the chassis dyno at Crazy Horse Racing in South Amboy, N.J., Blue Thunder turned out a respectable 191.9 horsepower and 272.8 lb.-ft. of torque to the rear wheels. Both the dyno and drag runs were made with a full tank of 87-octane fuel, and the engine temperature at about 160°. The gas gauge is shot so in order to maintain a consistent weight at the drags, I'm going with the full tank, rather than guessing by mileage.

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Some of you may have caught the third-gen T-5 Pro 5.0 shifter install in the previous issue. (Wow, what an improvement!) This was my first modification and now that the sloppy stock shifter is gone, I looked for a good aftermarket exhaust system to be the first performance modification. Third-gen owners actually have a pretty good selection when it comes to this performance part, and while the other staffers love the sound of some other popular exhausts, I opted for something a bit quieter due to the excessive time spent in the cockpit.




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