Hey guys,

ive been thinking about wacking on a bigger throttle body for more powarzzzzz but have a question...

The TB be off an XF (67mm or 74mm bore):

If i replace the current TB with the XF TB, will it require a retune or piggyback or something of the like to prevent it from leaning out and melting my pistons..

or

will it by fine and ill smoke skylines from the word go :) ...

thanx all :D

I'd be thinking it wont work.. Mainly 'cause everyone else isn't doing it, they'd rather go for a smoothed TB. Would need an adapter plate for the plenum because of the bigger unit size also.

I agree with nick yo. The t/b is purely a restrictor to allow however many L/s of air the engine needs. As it's pretty large from the factory i don't believe your engine will be needing to draw any more in and the inlet manifold will still restrict the flow at the next step.

Sure you could see more kW if its more efficient but i see it being rather expensive to modify and yes a tune would be needed as especially down low it'd allowing alot more air in as oppose to the 65mm units leaning it out.

I could see you throwing a mild cam in for a similar price.

imo fuel economy would go to ****? i was looking into work on the TB and manifold maybe getting it smoothed but cost vs. benefit wouldnt be seen until very very top end

i think i read somwhere that the standard TB will flow somthing like 300kw? might be less, but you would not see any benifit from fitting a larger TB only throttle respone would be improved because your not moving the foot as far to get the same amount of air into the motor... sort of a placebo effect.:doubt:

although a different engine, a 65mm throttle on a redtop SR only becomes a power robbing restriction once rwkw's start approaching 300

a larger throttle will only increase top end power if the stock unit is a restriction, but what will happen is low end throttle response will be increase, but wouldnt do it without a tune.

the XF TB onto skylines and silvias is one of the more common TB upgrades