Corvette Forum : DigitalCorvettes.com Corvette Forums banner

Status
Not open for further replies.
1 - 1 of 1 Posts

·
Super Moderator
Joined
·
8,480 Posts
Discussion Starter #1
throttle body size

have you ever noticed that in all the years everyones been swapping to 52mm and 58mm and mono blade 1300 cfm throttle bodies , they have said things like
I did not gain a great deal of hp
I lost some throttle responce
It sounds differant but I don,t seem to go faster
I only gained a tenth of a second plus a couple thousands in the 1/4 mile

Ive yet to find anyone that lost hp,once the engine was properly set up and adjusted with the larger throttle bodies
a throttle body is not like the venturies on a carb that control the fuel/air mix, the computer and sensors and injectors do that on an EFI system, the throttle body is only a air volume control valve, your engine can only use (X) amount of air at any given point, as long as the throttle body is allowing that much OR MORE to pass UNRESTRICTED, its going to work reasonably well. the individual ports combined on even a 454 size sbc spinning 6500rpm (WAY OVER ADVISEABLE PISTON SPEED) only can use about 850-950cfm (do the math) that can be fed from dual 56mm throttle bores, since a 58mm is the closest size thats what most guys with large engines use,a 383 like mine with a custom stealth ram only needs about 775-825cfm. a 52mm is just a little to small and a 58mm is overly large BUT, TOO LARGE, WON,T HURT PERFORMANCE NEARLY AS BAD AS TOO SMALL or RESTRICTIVE MIGHT! ONLY TOO RESTRICTIVE/SMALL hurts!
yes you might lose a small amount of throttle responce, but an overly large throttle body won,t hurt high rpm hp if mounted on an engine with an intake with the correct port runner size/length, compression and cam timing. don,t forget that a great deal of how effective an intake system is is controlled by the rpm range where the exhaust system on that same engine scavages the cylinders efficiently. if you don,t have full lenght tuned headers and a free flow exhaust , adding a larger throttle body is likely a waste of effort. if you cant get rid of whats in the cylinder now you can,t refill it effectively anyway. keep in mind an engine is A SYSTEM, ALL PARTS MUST BE DESIGNED TO WORK EFFECTIVELY AT THE SAME RPM,AND DISPLACEMENT.
HP is MORE THE RESULT OF HOW EFFICIENTLY you can pack fuel/air ,into a cylinder, burn it efficiently, and get rid of it , useing its energy to reload the next charge than almost any other factors, useing a larger throttle body can help!
I just swapped from my 58mm back to the stock 48mm as a quick test on my 383 corvette, guess what! the stock throttle body made the vette noticably SLOWER!!
yes it took about three quick 1/4 mile runs and the 58mm throttle body is right back where it belongs on my custom STEALTH RAM!!

FYI
48mm flows about 660cfm
52mm flows about 780cfm
58mm flows about 1000cfm
mono blade flows about 1200cfm

the stock 350 displacement engine at 7000rpm (YOULL NEVER GET THAT HIGH) would need about 720cfm
 
1 - 1 of 1 Posts
Status
Not open for further replies.
Top