At what point does a 52 not flow enough air? And hopw do you figure it out?

 

I ve read from "injuneer" that a 52mm is max out at about 500hp(flywheel).

 

When we had my 381 on the engine dyno, the 58mm TB was able to supply all the air the engine needed to make 500 flywheel HP at about 77% open. Opening the blades further did not increase air flow, or HP. If you work backwards from the 58mm throttle being open 77%, it would appear a 52mm TB at 100% would have supplied about the same amount of air.

 

what about a Hi RPM smaller CID engine? would it be a restriction at higher RPMs on the smaller engine? with a higher piston speed it would consume more volume at some point.....

I was looking more towards a formula to find out.......I have some for carb. stuff but it seems to be way off.....

 

The volume of air moved is a pretty much function of the HP being made. It isn't going to matter much whether its a large displacement making power at 6,000rpm or a small displacement making power at 8,000rpm. The volume of air required to burn the fuel that releases about 1/3 of its energy to make HP is pretty much "fixed". The plenum is there to decouple the throttle body from the intake runners.

 

o.k that makes sense

 

I guess see if you are pulling vacuum at WOT.

 

well I know that but this hasen't been put together yet......

 

It's better to error on the side of too big with throttle body's, so if you haven't bought one yet I would just get a 58mm and never have to worry about it again. Look at the LSX community, they are running 90mm throttlebodies that make our 58's look like stock to compared to those. + the throttle response is alot better with a 58mm if that matters to you.

 

I have one....got a used 52 cheap.....I know the 58 just tips in quicker like fred stated.........I'm sure it will be fine, I have made almost 400 with a stock one for the past 10 years

 

Dual 58mm Throttle body should be approximately equal to a single 82mm throttle body. Having a 90mm throttle body should give you about 20% extra air flow. If that helps

 

If you have a 52 I'de keep it unless you are worried about squeezing every last hp out of it, the only reason I sold my 52 for my 58 was that I ran out of boltons except an e-wp and I'm not going to run one of those, I didn't gain anything in the 1/4 with it though, then again i was only trapping 114 at the time so it probably wasn't a restriction back then.

 

but would a 58mm make u loose power if u are no way near 500hp at the flywheel?... like could it be too big?

 

No, only just a waste of money if you bought it as a mod and expected a power increase when you really didnt need it.

 

say u were putting out 300rwhp and u have long term plans of 500rwhp would it help if u got a 58mm at 300rwhp?