The return springs are shot on my stock TB which makes it hang up and not close properly at idle and it hovers around 1k until you tap the gas or put your foot on the brake for whatever reason, so Im looking to replace it. Ive read 48mm is fine for stock or mild but then again Ive read 52mm is a nice step up if you have exhaust work which I do. What Im looking for is track proven increases/decreases from a stock 48 mm TB to a 52mm TB and what manufacturer you used. Seat of the pants improvement is nothing short of a guesstimate so Im looking for numbers so I can make a better judgement on what to spend my money on, thanks!!!

 

One guy claimed it gained him a tenth or two, but the runs were on different days with different weather condition, etc...

If you are running slower than high 12's, I would bet it won't be much of a difference...do a search for a recent thread about a BBK TB size with a lot of replies...this debate has been covered.

I can't wait for actual proof from someone, not just manufacturers claims...

 

thanks for the info! I may bite the bullet, get a 52mm TB and i have lots of runs before and know what my car is capable of so I will have definitive numbers for MY specific application and results. As soon as I can swing getting one and have slips before and after, Ill post back....