69mm, but dont do it. it is not worth the hassles and it really doesnt improve anything but throttle response a bit. that is...unless you have a manual, most of the problems associated with these oversized t/b's come in the form of messing up the auto's shifts.
i've never yet seen any good comments from a 69mm TB on the ecotec. it's almost like you gotta do a chip for it to sell with the TB to make it a worthwile adventure. just wondering but the only way i can see it working isif you go to a twin TB setup but have the second TB on a 30% delay so that normal driving doesn't open up the 2nd TB so shift points should be normal etc and then if you mash the go pedal then you get lots of air.
I think 69mm is the biggest for the eco's. Had one on mine , and it worked fine after i fixed my lead issue. But as mentioned in a previous post, mine was a manual so it could not bugger up my shift points.
i have a 70mm throttle and i bored out the elbow in the intake manifold, makes the car way more responsive, feels quicker, shift points are fine on mine, i moved my TPS clockwise so it sensors the extra air earlier. but its still not 100% but still better than the stock one. ill get it tuned one day
The reason for this is that I'm getting the 4.2 stroker and super charging it as well hopeing the get 400rwhp so every little bit will help.
if you gonna get a tune it shouldn't matter if you fit the gibber TB as the tune should fix all those little problems
