Mid America Motorworks Mass-Airflow-Sensor Housing (PN 616-002)
Cost: $49.95 (on sale; normally $99.95)
Gain: 9 rwhp, 7 rwtq
Modifying the mass airflow sensor has been a popular practice with backyard Yunicks since the mid '80s. Rather than simply punching out the screens on the OEM unit, we decided to try one of Mid America's Mass-Airflow-Sensor housings, on sale at the time for only $49.95. Comprising two larger-than-stock plastic end pieces that sandwich the factory MAF, the housing is said to move 55 percent more air than the OEM setup, for a total flow rating of 1,000 cfm. Ours installed in around 10 minutes with no unpleasant surprises, and after verifying that the car's idle quality was good and that no SES lights had been triggered, we made our next set of pulls.
We were stunned when the Dynojet registered improvements of 9 rwhp and 7 rwtq-precisely what Mid America claims for the unit in its catalog. That the plastic aftermarket housing is lighter and conducts less heat than the aluminum stocker is an added bonus.
Aside from a forced-induction system or nitrous kit, this may be the first aftermarket part we've tested whose performance actually lived up to its advance billing. Even at its regular price of $99.95, this one's a steal.
Breathless Performance Products 160-degree Thermostat (PN 100-214) and Coolant Bypass Kit (PN 100-215)
Cost: $39.98 ($19.99 each)
Gain: 1 rwhp, 0.5 rwtq
Corvettes have long been known for overly warm engine-operating temperatures, and the LT1 C4 is no exception. Ours tended to run in the 200-to-210-degree range in normal driving, occasionally creeping into the 230-degree zone when traffic snarled.
While they were unlikely to make a significant difference in our dyno numbers, we reasoned that a few well-chosen cooling-system modifications should have a salutary effect on real-world performance and engine-component longevity. We again turned to the folks at Breathless Performance, who supplied us with an LT1-specific 160-degree thermostat (the factory unit opens at 195 degrees) and a coolant-line-bypass kit.
The parts went on easily in under an hour and with a minimum of perturbation. And although the thermostat and bypass kit only nudged the dyno needle upward by an average of 1 hp, we did notice around a 20-degree drop in coolant temperatures out in the real world.
It's worth noting, however, that this cooling benefit all but disappeared in heavy traffic, a fact attributable to our car's stock fan programming. Indeed, only by complementing the lower-temp thermostat with revised fan-actuation thresholds is it possible to exert complete control over engine-operating temperatures. We'll address this in the near future, when we perform a dyno-based custom PCM tune on the car, but for now, the 20-degree drop under most driving conditions is a welcome improvement.
Breathless Performance Products Adjustable Fuel-Pressure Regulator(PN 100-208)
Gain: 0 rwhp, 0 rwtq
Like modifying the factory MAF sensor, fiddling with fuel-pressure settings has been a popular method for extracting extra power ever since the Corvette graduated to electronic fuel injection in the mid-'80s. Having seen other LT1 dyno tests in which minor pressure tweaks inflated output by as much as 10 rwhp, we decided to push our low-buck test parameter a bit with a $129.95 adjustable pressure regulator from BPP.
After establishing that our Vette's fuel system was providing 47 psi of pressure in stock form, we dialed in a series of 2-psi increases, retesting at each increment until we reached a maximum pressure of 55 psi. Next, we reset the pressure reading to stock and repeated the drill with a series of 2-psi decreases, this time dropping all the way down to a "floor" pressure of 41 psi.
Somewhat surprisingly, none of our monkeying had any positive effect on the output of the engine. Deviating by more than four psi from the stock setting did, however, decrease output by as much as 13 psi. Could it be that by 1996, Chevy had refined the LT1's electronics to such a degree that altering fuel-pressure settings was no longer a viable power-tuning technique? Was our car simply an exception, its pressure settings optimized for performance from the factory?
Notwithstanding our rather disappointing initial results, we suspect that the pressure-tuning capability provided by the adjustable regulator will prove useful as we perform more significant modifications in the future. Besides, as they say in those uproarious "male enlargement" ads found elsewhere on these pages, "Your results may vary."
In the end, our efforts yielded 13 rwhp and 10.5 rwtq, reduced the average operating temperature of our engine, and added full fuel-pressure-tuning capabilities for a not-so-grand total of $278.92. Too dear for you? Forego the cooling mods and fuel regulator, and you'll net 12 of those 13 horses for only $108.95.
H.L. Mencken once said, "The chief value of money lies in the fact that one lives in a world in which it is overestimated." The same applies here. We're just not exactly sure how.
1810 N. Parsons, Ste. 106/108
Seffner, FL 33584
Breathless Performance Products
2070-F Tigertail Blvd., No. 2
Dania, FL 33004
Mid America Motorworks
P.O. Box 1368
Effingham, IL 62401