Pontiac GTP High Velocity Throttle Body Info

It’s no secret that increasing boost and lowering intake temps will make your car faster, but until now, there really hasn’t been a way to achieve both simultanously.

Thanks to ZZPerformance’s High Velocity Throttle Body, you can now have your cake and eat it too. This total work of art was designed to work perfectly in the Series 2 3800 model. Most people don’t realize that the boost isn’t the only factor in determining supercharger outlet temps. The charge temperature needs to be calculated from the difference between the inlet and outlet Hg, meaning that a SC putting out 101Lbs of boost with a restrictive inlet, will actually have a higher outlet temperature, creating more Knock Retard than a SC putting out 11Lbs without a vacuum in the inlet.

There have been some tests by individuals claiming that an inlet vacuum on a L67 is minimal even with a lot of modification. However, we have to disagree, and we have extensive tests that can prove otherwise. What we found, was that KR will go up and boost will go down way before you even reach an inch of vacuum.

An autotap log shows an intake restrictive enough to create 1” of vacuum, caused the 99 to have an increase of 5 KR, and drop a full pound of boost.

The autotap is convenient, but how does this transfer into real world performance? We took the 99 in nearly stock trim** to the track and ran three tests: Test one was as it sat, test two was removing the headlight, and the final test was installing the ZZP TB. All in all we made 8 passes, allowing roughly 20 minutes between each run with the hood open, here are the slips:

 As you can see we gained almost 2mph resulting in an ET drop of almost 2 tenths! We expect the gains in a car with a smaller than stock pulley to be even better.

This is one of the parts used on the ’99 to run consistent 13.0’s at speeds of 105mph in 75-80°F outdoor temps.

** Stock 99 airbox with K&N, high ratio rockers, stock 3.8″ pulley, spare tire removed, 2 ½” exhaust, stock manifolds, stock mufflers, ½ tank 93 octane gas, no other track preps.

Newer Style on left (’99-’00); core on the right is older style (’97-’98)