Since the inception of GMHTP's LS1 project car, we've cut a full second off its ET (13.36 to 12.36), added 6 mph (103 to 109) to the trap speed, and added 55 horses and 48-foot pounds to the wheels. Up to this point we've had great luck assaulting the '99 T/A with a bevy of bolt-ons, hooking it up with trans mods and a converter, and giving it just enough traction to drop ETs without shredding the stock, 3.23-geared rearend. Of course, there's no way of telling when this 7.5-inch weakling is going to bow out in spectacular fashion; we'll deal with the sorry-assed 10-bolt when the time comes.
Regarding external engine mods, the bolt-on flood has slowed to a trickle; there were only a few more that we wanted to test before moving on to bigger and better things.
Three of those mods, an electric water pump, a larger mass air meter, and an aftermarket throttle body, have enjoyed internet infamy for quite some time. The jury is still out on whether these "performance enhancing" LS1 mods do anything positive--so we wanted to dyno test them to find out for sure. Unfortunately a supposedly kick-ass throttle body wasn't ready in time for testing, so then there were two.
So for this go-around, we put these LS1 components to the test: a Meziere electric water pump and an SLP 85mm mass air meter. Neither are absolutely necessary at our approximate 350-rwhp level, but may prove helpful in the days ahead. Three critical areas will be measured with the help of SuperFlow components: the dyno will record changes in rear-wheel power and any changes in coolant temperature, and the flow bench will measure any changes in airflow between the OEM MAF and the 85mm unit. Let's get going.
Before starting another modfest, a spin on SLP's SuperFlow chassis dyno is made to get an accurate baseline. After headers and an exhaust system were installed (March 2004) the T/A made 347.4 horses and 347.1 foot-pounds at the wheels; today, 341.3 horses and 339.8 foot-pounds showed up, along with a few degrees of knock retard. | 
After a short cooldown period, Hank Daniecki Jr. begins the water pump swap by popping off the airlid, then removing three 10mm bolts from the throttle body. | 
Once the bolts are gone, the throttle body is removed and set aside. |
The Katech tensioner is loosened so the serpentine belt can be removed. | 
A catch can is placed under the car and the coolant is drained. With the radiator dry, Hank disconnects the upper radiator hose from the pump and begins work on the six 10mm bolts. | 
Here's a trick to make pulling the stock pump easier: on the driver's side, remove the 15mm bolt retaining the nearby tensioner pulley to allow better access to the lower water pump bolt. |
With that last bolt out, the water pump can be pulled forward. | 
Brian Reese uses a pair of vice grips to remove all of the coolant lines from the passenger side of the pump... | 
...and then it is removed from the car. |
With the factory pump off, you can see the coolant passages leading in and out of it. | 
We like to replace used gaskets regardless; since ours were shot two new GM gaskets (part No. 12559271) are used for the pump install. | 
Daniecki lines up the two gaskets and places the Meziere water pump on the front of the motor. |
Two of the factory bolts are screwed in to temporarily hold the pump while he verifies that the gaskets are seated correctly and the pump is lined up. | 
All bolts are then installed, snugged up, and torqued to 22 foot-pounds. | 
The inlet was placed onto the pump and tightened down with the included Allen bolts. (Note: the thermostat IS NOT installed under it, it goes in the upper neck.) Next, the two Meziere heater hose fittings are screwed in and tightened. |
The three coolant hoses are slipped onto the nipples and clamped down. | 
Then the pesky driver-side pulley was reinstalled, as was the Katech pulley and serpentine belt. | 
The SBC thermostat is installed under the upper water outlet housing. Now the upper radiator hose goes into place on the new Meziere pump. |
The throttle body remounts to the manifold and its three bolts are tightened down, then the induction and all of the sensors are reconnected--all that's left is the wiring. | 
We chose to wire the Meziere water pump through one of the Trans Am's relays, found nearby on the driver's side of the engine bay. As you can see here, the quick connection clip from the pump has already been snapped together. Be sure the battery is disconnected! | 
Brian unclips the driver-side power distribution block from its supports. He traces an ignition relay... |
...terminal 30, from a GM schematic as it is the switched ignition key source--when you turn the key this wire gets power. | 
The pink wire is number 30, and Reese removes the insulation in preparation for adding the Meziere pump's blue hot wire. | 
Reese solders the pump's power wire into the pink wire. |
He then connects the ground wire to the chassis ground on the driver-side shock tower and snaps the fuse box back into place. The battery was reconnected. | 
Our finished Meziere electric water pump looks sweet in the T/A's engine bay. Once the coolant was topped off, we were ready to test it. After warm-up driving it was clear that the Meziere had come to play: when the revs came down, the water temp would drop to a chilly 150 degrees in gear at idle. To keep the test consistent Hank ran the T/A on the rollers until the temp matched our baseline numbers (around 176 degrees), then made the pulls. 345.3 horses and 344.6 foot-pounds hit the rollers, and the high-rpm knock retard had disappeared. | 
The electric water pump made power as promised--next up: the MAF mod. We would be bolting on SLP's 85mm MAF (part No. 23060, $160), said to flow 895 cfm at 28 inches of water--90 cfm more than the stocker. |
Before installation, a flow comparison on SLP's new SuperFlow flow bench tested that statement. As we looked on, the T/A's factory 75mm MAF flowed 765 cfm at 25 inches of water, the SLP 85mm sucked 849 cfm. (The lower than rated atvacuum setting of 25 inches vs. 28 inches was necessary since SLP's MAF was exceeding the capacity of the flow bench before reaching 28 inches of vacuum.) That's an 84-cfm increase with screens! | 
So it flows more--the important question is, will it make any power? The SLP MAF is installed in place of the OEM unit and the Bird is readied for another dyno pull. | 
The dyno graph shows the results: from the 341.3/339.8 baseline, the T/A gained 4.0 horses and 4.8 foot-pounds with the Meziere pump, and an additional 2.8 horses and 2.7 foot-pounds with the bigger MAF. Notice how we saw a large power gain under the curve from the electric water pump--here is where the big difference between the Meziere and the stocker showed up.Chart courtesy of SLP Performance Parts |