Some aftermarket throttle bodies have no base idle adjust screw, so what do you do in that case. BBK and Holley are two that come to mind that do not have this adjustment. Any input ?

 

What is the reason for asking about this? Are you considering getting a new one? I woulnt suggest it. Your stock TB should be fine for most applications. If you decide to get an aftermarket i would suggest 64mm at the largest. Anything bigger would be overkill.

 

depends on his setup on what size is overkill or not.

 

Yes it does...forgot to mention that.

Thanks.

 

Guess my setup is not the question or whether I need it or not.

I was just wondering what happens on those T/B's that are without the base idle adjustment screw. How is it adjusted ???????

 

here's my rpm service 70mm tb. The nut and bolt under the cable pulley is used to adjust idle. You turn the screw cw to raise idle.

 

how does the screw adjust the idle other than opening the butterfly......... interesting ??????

 

ttt

 

That screw does it all when it comes to setting idle speed.

when you adjust the idle screw on an oem tb you change how much air the tb needs to bypass/add to maintain idle speed. this aftermarket tb doesn't have that idle adjusting screw. There is an air passage that will allow air to get into the plenum when the butterfly is closed, but in my case it wasn't enough air to get a 900 rpm idle. So to increase idle speed i had to turn the screw cw which opened the butterfly and gave me more air.

 

JG 70mm TB's are the same way. they have bypass holes but if they do not bypass enough air then you have a throttle plate screw adjustment(butterfly) the only thing crappy about that is the fact that it changes your TPS voltage and brings your TPS % up instead of it being 0-3% its like 3-5% which in some cases causes idle issues(some cases not all)