Throttle Body
 

I was talking to one of my coworkers about mods, and he suggested I port and polish the throttle body.

He told me he did this to his Z-06 and it dramatically increased throttle response :

http://www.s2performance.net/

http://forums.corvetteforum.com/showthread.php?t=1548531&highlight=shaner

http://custom.autos.yahoo.com/gallery/photos-car-8202;_ylt=Aq0EL53HMqAKSy6B35VPC7BK.ckF?photo_cat=a ll&start=10&sel=14

Anyone ever done this to their Boxster, or know anything about it ?

Nick

I've not seen a larger throttle plate offered for the Boxster. If you can't find a bigger plate, you can't port the body. Polishing, however, is still do-able. Probably a little flow gain but won't cost much if you do it yourself either.

Blue,

I think an enlarged throttle body is mentioned in the third link and offered here :

http://www.scargoracing.com/

( Click products - Parts for the Boxster )

Nick

I have heard of and seen this mod done before in the past, but not on a Boxster. I've actually seen where people open up their MAF body (this was done on a supercharged vehicle and everything was opened up as much as possible) in addition to intake kits and a larger throttle body. The idea being that the more air in and out of the motor the more power.

However, despite the theory of more air in and out, the more power, I have experienced where the exhaust on a 4 cylinder (Nick, the red 240SX with the turbo) when opened up to 3" all the way (new header, and full exhaust) actually dropped the power (theory that there wasn't enough back pressure?). This was done before the turbo was added to the car.

I'm hoping MNBoxster can chime in here and explain some stuff...

That's the entire throttle body, not just the plate, but it does sound like it's larger. Then you polish from there.

Without increasing the plate size.. You would be just widening the outer surface and tappering it up to the plate then polishing it... While the air will flow through much smoother, you are still bottle necking the air at the plate, so im not sure how much power you can get out of it.

Part of making good lower RPM torque is through air velocity. This helps to fill the cylinders and aids in mixing. The larger the intake path, the slower the intake speed, thus reduced low engine speed torque. This is typically most sesitive to port sizing and valve timing.

Exhaust size is tricky. You're not just trying to open the exhaust path from the engine to the air but you also need to take resonant sound pressure waves into account. These sonic waves can hurt or help cylinder evacuation depending on design. Also, valve timing is designed with a certain amount of back pressure. Changing the backpressure can lead to reductions in power and economy without internal timing changes.

Exactly, that's why I made my original comment about the larger plate.

BTW, it looks like an exchange program with the throttle body, so they're probably just reworking stock parts and adding their own throttle plate.

Also, throttle plates can be modified to be more aerodynamic when fully opened. Things like knife-edging and shaft smoothing can be done to improve flow.

^^^ my bad, thought you were the topic starter, After i read all the comments, i ran to the top to see who started it and i was 1 (page Up) from seeing NickCats comment.

A very trusted mechanic pointed out to me that the rest of the Boxster intake remains unchanged, making a throttle body mod impractical.

To add to what blue2000S wrote, sure, a larger throttle body can "improve" throttle response. You're letting in more airflow at a given throttle position versus the stock throttle body.

You can get the same effect without spending any money by pushing the throttle pedal more. ;)

I'm in conflict about this throttle body. The mechanic who told me it would not help is a considerably talented Porsche mechanic who posts on some other BB's. However, I noticed Techart uses one in their 2.5 powerkits. They seem like a trustworthy aftermarket supplier. I have to admit though their website claims 230Hp out of a 2.5 with just a SS exhaust, throttle body and ecu upgrade, I smell marketing at work...I'd love to do that mod but I'm skeptical.