Anybody know what size the stock V6 throttle body is? Thanks.

I want to say 57mm but others can confirm

Its smaller then that. Not sure on the exact size but you can bore it out to 57mm.

-Frank

I am pretty sure it is 52 mm and can bored out to 56mm and if you do the modification to the half shafts with the flat mounting screws it is equal to 57mm.

D. Morse has a nice rebuild of tpi with boring out to 56mm and matching this to upper plenium including return shipping for 100.00

tim

Thanks for the replies....

I tried to measure the inner diameter on the car with my digital caliper, but I can't get it fully into the opening where the butterfly is. Eyeballing it, It appears to be around 50mm, but I know that's not completely accurate.

Stock it is 52mm
Fiero Store "big bore" is 55mm
Darrell Morse bores it 57mm

You can't make the bore "larger" by "modification to the half shafts with the flat mounting screws"
You can maximize flow but the diameter of the bore is a constant. It will be XXmm regardless what you do to the shafts and screws.

To measure the bore correctly, You need to measure at the base of the throttlebody not the face.

can anyone post the CFM of each of these?
and also the CFM a 2.8, a 3.1, and a 3.4 need with a stock cam @ 5000 & 6000 rpm?

quote Originally posted by Pyrthian: can anyone post the CFM of each of these? and also the CFM a 2.8, a 3.1, and a 3.4 need with a stock cam @ 5000 & 6000 rpm?

CFM is directly proportional to HP :

140 hp = 203 CFM
160 hp = 231 cfm
180 hp = 262 cfm
200 hp = 290 cfm

basicly every 20hp = 29cfm

[This message has been edited by Kohburn (edited 10-11-2006).]

quote Originally posted by Pyrthian: can anyone post the CFM of each of these? and also the CFM a 2.8, a 3.1, and a 3.4 need with a stock cam @ 5000 & 6000 rpm?

CFM of an engine is based on engine displacement and RPM.

The total CFM of an engine is calculated by:
Engine Size (c.i.d.) X Maximum rpm/3,456=cfm@100 percent Volumetric Efficiency (VE)
So as an example a 2.8L is 173 ci.
173 X 6000 / 3456 X 1.0 (100%) would be 300.3 cfm.
This would be the max the engine could flow at 100% VE.

Some things to also note,
VE of a stock natrually aspirated pushrod engine is around 85-87% VE. You can raise the VE (even over 100%) with mods like multi-valved heads, sonic tuning, and forced induction are some examples.

The CFM vs. HP as Kohburn lists is total actual CFM of an engine. Going back to the Fiero 2.8L with the lower VE (87%) it needs 261 cfm but with the intake runners, cam, and heads the actual true flow is closer to 200 cfm of the engine even though it has a calculated cfm of 300. Hence why the 2.8L has roughly 140hp.

Throttle body CFM is just a calculation. At 52mm the TB flow is about 308 cfm. At 57mm flow is 354 cfm. (These are max values and do not take into account the throttle plate and design of the TB.) But just because a TB can theoretically flow 308 cfm does NOT mean that the engine can utilize all of it. This is why just changing to a larger throttlebody only gives minor gains. If you want to increase power/flow drastically, everything in the path needs to be opened up.

To find the actual true flow of an engine would require a flow bench and an engine dyno.

[This message has been edited by Oreif (edited 10-11-2006).]