Throttle body

[My99VTACCLAIM]

Im looking at installing a 70mm throttle body. Will i use more fuel and just gain power or make it run more efficiently and use less like extractors?

[greenfoam]

It'll make your throttle more touchy, highly unlikely to do much of anything else. I put a 70mm on my 5 litre after a very long time of believing it didnt need one, just to see. I got

Zero point Zero gain on the track

[moose man]

I agree completely with greenfoam.

You might even be lucky and confuse the engine management system and lose power/efficiency. The computer fuel mapping is programmed to inject x amount of fuel at y throttle opening, and expects z amount of air to flow through the inlet at that time (there's a lot more than this involved, but keep it simple).
If you change the throttle size, you change the air flow rate, and the fuel system is no longer calibrated.

Any effects (good or bad) will be felt most at low throttle opening - it will probably run lean on acceleration, but these effects will lessen the more throttle is opened, to no difference to full throttle.

You inlet tract has very few restrictions in it. Leave it the way it is. If you don't believe me, connect a manometer (vacuum guage) and go for a full throttle drive and check manifold vacuum. You will find it has very minimal vacuum, meaning no restrictions.

[Tsunamix]

It Depends on the engine.

With the ecotec Auto's, the larger throttle body helps to remove the doughy bottom end response. It doesn NOT affect maximum performance really, as 68mm allows enough air in anyway.

When you have added a few other mods, insulators, extractors, high ratio rockers at least, you may see small gains from the oversize TB as your engine will need a little more airflow at the top end.

Once you go a custom tune with a raised red line plus above mods, you will see noticeable benefit.

The major reason for going OS TB is low down throttle response.

[WogBoyz]

It Depends on the engine.

With the ecotec Auto's, the larger throttle body helps to remove the doughy bottom end response. It doesn NOT affect maximum performance really, as 68mm allows enough air in anyway.

When you have added a few other mods, insulators, extractors, high ratio rockers at least, you may see small gains from the oversize TB as your engine will need a little more airflow at the top end.

Once you go a custom tune with a raised red line plus above mods, you will see noticeable benefit.

The major reason for going OS TB is low down throttle response.

agree i have all them mods as said above plus a few little extra's and i did notice it quite alot

[My99VTACCLAIM]

My VT already has Pacemaker extractors and a highflow cat and a lukey catback as well as a K&N Panel filter which im looking to upgrade to a SS Inductions Cold Air Intake soon, which is why I was thinking of the throttle body.

[Tsunamix]

With the mods you have, you won't see much if any benefit in terms of peak power / torque. You don't have any mods that make the enginee consume more air, your mods just allow it to consume it's standard capacities more effeciently.

Add cam or high ratio rockers, or forced induction or a custom tune and you will see noticeable benefits. I'd leave it low on the list of priorities right now. I would suggest high ratio rockers, insulators and a foamtune first.