Bigger Bore TB

[Arctc Wolf]

I have been thinking about this a lot lately. Many people believe that a larger bore throttle body/maf unit will help you make more power. This is true, but only under certain circumstances. Our motor can only draw in as much air as it's displacement, heads, cam, intake, and exhaust will allow. If you look at people who do head porting, the idea is to keep the air velocity up while increasing the amount of air into the cylinders. If you port out the heads to the max, w/o doing any other supporting mods, you'll actually lose power, mostly at low and mid-range rpms because the motor isn't drawing in the air fast enough. This is the same idea w/ a larger bore throttle body. The larger bore will slow the air velocity down at lower rpm's, but at higher rpms, the increased size will help make more power. Having other supporting intake mods such as a lid/cai/removed maf screen, as well as cam/heads and exhaust setup will help offset this low-rpm power loss and allow even more power to be made at higher rpm's. In my opinion, a larger bore throttle body won't help you if u have very few or no bolt-on mods. perhaps if you had all the bolt-on's done and maybe a better flowing heads or a better camshaft, it'll make a good difference in power. I may be wrong, but I doubt it. If I am, prove it please, and help out everybody else w/ solid info about this type of mod.

[Dominic]

Being that the shape of the intake port and length of the intake plenum governs the air velocity since its the last area the air flows through, the larger throttle body is still beneficial.

By increasing the size of the throttle body, the initial airflow is at a slower velocity and must speed up more to go through the system and into the chamber. This nets a higher change in air velocity for the same speed which results in a higher "air force" for the same mass of air. This higher air force packs a wee bit more in each chamber and nets a higher dynamic compression - in the end it just means more horsepower.

But yes, more boltons would make a larger TB more beneficial. Our TB is substantial in size, but bigger can never hurt since its just a throttle body and not a carb.

[Arctc Wolf]

it can hurt ur low-end. i've seen a few dynographs of before and after people put on bigger bore tb's, and they gain power up high, but lose a little down low. it seems like it uses the same principal of the exhaust, bigger gets u more power up high and smaller gets u more power down low.

[Dominic]

That would make sense... also partial throttle efficiency would be lower and less accurate.