thomasw31

I was looking at adding some more hp to my car by upgrading the throttle body. Possibly to a Skunk2 70mm Throttle Body to my F20.

And I was wondering if I would need to do any other modifications, such as boring out the intake manifold, or changing Cold Air Intake coupling.
My intake manifold and throttle body is currently stock, and Im running an Injen CAI.

I prefer just to install it without any extra parts/labour.

RacerXI

Larger throttle bodies tend to provide more throttle response and feel rather than HP (approx 5). Best application would be a bored throttle body with the opening of the intake manifold matched to it to provide the best flow.

thomasw31

Thank you for the response.

What if I used a spacer between the throttle body and the manifold? A spacer that diverts the big throttle body to the stock manifold size.
I'm not sure how much its cost to bore out the stock manifold, but a spacer seems a bit pricey.
Are spacers worth installing instead of boring out the manifold?

s2cho

just bore it out yourself with a dremel to match the new tb

thomasw31

I do have an air tool with some bits that I used to bore struts with when doing alignments in the past.

I would only be able to bore the opening (inlet in believe) to hopefully match the throttle body, I would just have to be cautious on having any metal shavings blowing into it. Would just boring the inlet be sufficient instead of boring the whole throttle body? I imagine I would only bore 1/2" to an inch in if I was to do it myself.

zeroptzero

That is a a lot of boring to do with a dremel, if I recall the stock manifold on an f20 is around m, it would take a lot of grinding to get it opened up evenly to 70 mm. You can count on getting some metal shavings in the manifold, so it is best to do it off the vehicle so you can give it a thorough cleaning when done. I went with a J's Racing TB and I did a mild bit of grinding to get it up to 64.5mm. You might be able to find an adapter from one of the suppliers but then the TB is no better than stock as the minimum diameter restriction is still the same as stock. I don't think you are going to get more than a 5hp gain with a throttle body, so I preferred to keep it mild. I did like the upgrade as I got the TB on the used market for a decent price. I don't believe any of the manufacturer claims when it comes to throttle body upgrades, even J's Racing, I think 3-5 hp is about all you can expect as a direct bolt-on mod.