GT3 82.5mm Throttle Body!

[Shehadehd]

Originally Posted by Yellow986S

Hey guys,



Would a GT3 82.5mm Throttle Body fit on a 2000 Boxster S?

I know that I will need a larger plenum to compliment the larger TB, is there anything else?



Will this larger 82.5mm throttle body create better performance numbers compared to the 997 76mm TB?



The IPD plenums are too expensive for just a plenum so I would rather go with a OEM larger TB and plenum for cheaper.

I'm working on a similar conversion. I opted for the 75mm throttle body because the MAF tube has a 75mm inner diameter. If you decide to go with a bigger throttle body, be aware that the MAF housing will restrict the airflow anyways.

Also, if you get a 83.5mm throttle body you will need to pair it with a similarly sized plenum. Reducing it to fit into your intake manifold will most likely require some reducers.

Lastly, running the 83.5 throttle body/ plenum with the 75mm maf housing will cause air velocity to decrease because 3 inches of air will need to fill 83.5mm of space. This can cut low end torque and reduce air pressure at the cylinder heads.

I think to really benefit from the 83.5mm throttle body over the 75mm, you will want a larger MAF housing. Keep in mind, this will most likely require a fuel/maf remap. running with almost 1" more air might push your injectors to their rich limits, in which case you might run lean with the added airflow you get at high rpm and speed.

With all that being said, if you find a way to do it, go for it. I would love to be proven wrong because then I can follow with the larger setup

Someone else might also want to check my info as this was just a kick of the tires explanation.