Gas Flow a 165 Throttle Body

Why gas flow the Throttle Body?

• To develop more power every restriction to the flow of air through the intake system should be minimised. Gas flowing and boring out the TB reduces the effects of this restriction allowing the engine to breath easier, develop more power and help the turbo to spool up earlier
• The modified TB will flow 17% more air. More air and more fuel equals more power
• Toyota obviously saw a benefit in enlarging the TB as the 205 came with a revised larger TB as standard

Surely the 165 Intercooler is a larger flow restriction?

This is correct. However as stated above reducing all the restrictions helps to develop more power.

Do you have any measurements?

Below is an illustration of the stock versus the new throttle body. The new gas flowed body's dimensions are in brackets.

Throttle body dimension comparison

Can't I get any old machinist to do this?

In a word no... For a start the butterfly valve is not circular, doh! You are going to need specialist tooling...

What does you Throttle Body look like?

Something like this...

Note the different thickness of the TB walls	Side by side comparison
Old TB	New TB
Old TB open. Note how far the bolts protrude from the butterfly support bar, this disturbs air flow, and the ridge around the TB before the butterfly valve	New TB open. Note the machining undertaken on the butterfly support bar - every little helps! The front edge has now been knife edged to increase flow further

Are there any other options?

Yeah, what about fitting an ST205 TB? This is the largest of all the GT4 TBs and measures ~60mm as standard. Whether or not this will fit either a 165 or 185 manifold remains to be seen!