a buddy of mine was going to bore out my throttle body for me, but I was wondering if the stock throttle body out of a 98GS can be bored w/out hurting anything. We were wondering if the butterfly "flaps" on them would have to be changed if we bored it out to say 60mm. also, does the mass air flow sensor interrupt the flow of the extra air going into the engine and bsaically ruin the extra air flow?

You can't bore the stock one to 60mm. Thats why you get the Jeep TB. You can bore yours up to 57mm, but most do it to 55mm. If you bore your TB, you have to make a new throttle plate ("Butterfly") no matter how much you bore it out. If your friend didn't already know this, I wouldn't let him do it. Make him do his first.

and we dont have mas air sensors, only the GST/GSX do, we use a MAP sensor located in the intake manifold

Scott, you can purchase a bigger throttle body from HowellAutomotive.com. Don't let your friend do it. This takes very precise machining and if he screws up, it will be a big expensive headache for you. Sean

thanks for all your feedback guys, but my friend who is gonna do it use to make guns for bosnia when they were at war. He can pretty much machine anything in the world very preciscly and the brand new 50K laser cutting machine at his work will help him as well. How do you change the flaps that you need after your done boring out the TB?

I wouldn't go past 57mm. I think the reason that you can't buy an aftermarket bored TB any bigger than that is because you start to run into internal channels. I'm not exactly sure about that, so I may be wrong there.

As far as the plate is concerned, I just took a measurement and the plate diameter is ~.015 inches smaller than the bore. It may need to be more or less than that depending on the thickness of the material you're using to make the plate, but that should at least give you a good starting point.

Good luck. Keep us posted on your results.


ride__________95 Eclipse RS : 5 speed
power________Gude cams : Jeep TB : AFX UDP : ram air : test pipe : GST catback
suspention___BOMZ F/R upper strut bars : ES inserts
sound________Kenwood KDC 5000 : Audiovox 8" sub toob - no sub amp(damnit!)
shizzle_______AutoCommand remote start : dual air horns : Caspers o2 simulator(rear)
incomming___Hurricane F/R lower strut ties : Field SFC Hyper-R
Jeep TB writeup - http://www.dimensia.com:81/jimbo/JeepTBfor2gnt.html

HI everyone. I was just wondering, what does a bored throttle body do? I mean, I know its bigger so it allows more air, but what about the size of the intake manifold? That doesnt change, so I mean, what does a bored TB do? Or is the intake manifold already bigger?