Where Should I locate a water/methanol injector when I can't find throttle Body Spacer


Asked by Apr 09, 2014 at 08:20 AM about the 1999 Pontiac Grand Prix 2 Dr GTP Supercharged Coupe

Question type: Car Customization

Ihave H2O/Methanol injection kit, I'm to place the injector after the mass air sensor which is in the front of the throttle body. All TB spacer for this vehicle say's won't fit supercharged.
Any Simple Ideas?

6 Answers

Norm Davis

Try AirRaid, I believe their TB spacer fits supercharged engines about $120.00. Shouldn't give any clearance issues. Setting the timing is going to be an issue with the boost/quench balance on a supercharged engine. Good luck!


A TB spacer is no benefit on any forced induction engine, whether it is turbo or supercharged. The injection kit will have to be mounted in the intake tube to be in front of the TB.

Norm Davis

Hold on....the TB spacer alone does nothing, agreed. But you must install a TB spacer in order to port the methanol at the right place, which is after the MAS but before the TB. Installing it as you described will put the injector before the MAS, which is not recommended. Doing so will pretty much negate any value to the methanol kit as the ECM will simply compensate for the increased density. The MAS location on the Pontiac forces you to use a spacer. All TB spacers are not equal. The supercharged GTP has a slightly different throttle body so you need the spacer that's specific for that setup.

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Best Answer

the TB spacer will be after the TB. it goes between the TB and the intake manifold. he said the methanol has to go before the TB.

Norm Davis

The methanol injector has to go after the MAS. After that it can go anywhere - after or before the throttle body. You could even tap the intake plenum if you wanted to (or were nuts) and install a series of injectors. But the common way to do this is to buy a TB spacer and tap it for the injector. Many cars have the MAS well upstream of the throttle body so there are places to tap into the air flow, between the MAS and the TB. That's not the case on the Pontiac, where the MAS is virtually bolted right into the side of the TB. You must use a spacer, or tap into the intake plenum.

1 out of 1 people think this is helpful.

Norm is right. From the guy who asked Question.

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