I was on a performance site and noticed they sold "ported" 52mm throttle body's for our cars instead of the stock 48mm ones. What would I expect to get performance wise if I bought this and put it on my engine?! Are they worth the $200.....also do I have to port the intake to match anything? Thanks---

 

On a stock/near stock car you wont gain much, if anything. After you get into cam territory, it may be worth a few ponies

They bolt on with no port matching or anything.

 

They also make a 58mm with does require porting of the intake. But unless your making big power you wont see much a gain.

 

According to my calculations, with a normally aspirated 350 cubic inch engine, assuming 100% volumetric efficiency (which you probably won't see), you would have to rev higher than 6400 rpm before a larger throttle body made any difference.
Now, for a 383, it would make a difference at a lower rpm.

Tom Piper

 

Acording to my Scanner on my almost stock LT1. There is vacum generated at begining at about 3k RPMs on a WOT run. and it gets worse as the RPMs climb. Not much though but its there. So somewhere between the Throttle. rubber bellows and MAF its not sucking enough air to keep up with the pistons. I had removed the duting past the MAF for the test only. I know the OEM ducting is restrictive so I tested without it.

I will run another test once I fix my car and this time without the MAF and the Bellows conected. If I see any Vacum build up at high RPMs I will know its the Throttle fer sure.


Math is great but real life is bottom line. It would be interesting if the MAF is the cause of the restriction. even if its a minor vacum... still a restriction for those who are all out and bent on max Horsepower. In my case I just have too much time on my hands and like to mess with my car.


Marvin

 

I have a speed-density '92 LT1 Corvette, and according to my Tech-1A snapshot of a WOT run to 6K rpm, the MAP sensor is telling me there is no vacuum in my intake manifold, it is at atmospheric pressure. I have a stock 350 bottom end with AFR heads, Crane cam, and roller rockers. But, my intake system in front of the throttle body is different than an F-body.
Since the only items in front of the MAP sensor to limit air flow are the air filter and throttle body, that tells me that neither one of them is a restriction for my case. And, this backs up my previous calculations I posted above.

Tom Piper

 

nice work. let us know what you find.

 

With my cc306 cam, crane gold race 1.6 roller rockers, crane double springs, trick flow pushrods, k & n cone filter, cc's air foil, .030 overbore, mildly ported heads, csr electric waterpump, tb bypass, cloyds hex adjust roller timing, edelbrock shorty's, y pipe w/ 1 high flow cat, 3" flowmaster catback, mad z28 tune, and descreened MAF do you guys think it would be worth it to upgrade to the 52mm throttle body?! If its a few ponies the $200 doesnt sound TOO bad. Thanks---

EDIT: The site says: 52mm = 730cfm = 465hp potential

but I just saw they have a 54 mm ported TB = 825cfm = 525hp potential

* the price difference is only $30 from 52 to 54 btw *

Would I see anything better with the 54 or for MY setup would the 52mm be the better setup? I am probably pushing close to 400 ponies at the flywheel-

 

You may not see much of an overall performance gain, but the throttle respnse would be worth it to me, even on a stock car.

 

The site says 10-15hp , but I doubt that, lol----

 

Remember, the pressure drop on whatever the weakest component is will get PROGRESSIVELY worse at higher RPMs. There is no brick wall. You can't say "a 48mm TB will make a max of 450hp, but not 451." That is just plain wrong. When asking how much HP (and by extension, how much airflow) a given bore (or set of bores) will allow, the NEXT question you HAVE to ask is "at what pressure drop?" This is EXACTLY like fuel injector sizing.

30 lb/hr

What does that mean? It means 30 lb/hr fuel flow but at an implied fuel pressure. And that flow rating will be DIFFERENT at a different fuel pressure (higher or lower).

Same with a TB. If a 48mm TB can flow, say, 1000cfm @ 1.5in-Hg pressure drop, then it should be able to flow 1400cfm @ 3.0in-Hg pressure drop. It's all about what pressure drop YOU deem acceptable. In other words, how much of a vacuum above atmospheric is acceptable? That is the question I'd like to have answered.

 

Tom I didnt even see your post, thanks for your answer, then proving it below . Kev, thanks too---so the answer is no from you too about getting the new one?! lol

 

Yes IMO it would be worth it. However, I would really stay away from a 54mm ported TB. The 52mm bore gets somewhat porous, i would only assume a 54 would look like swiss chease. 54mm billet pieces are available from ASM.

 

Actually the stock LT1 throttle body can't even be bored to 54mm. The throttle body will come apart before you reach that diameter. I've bored alot of LT1 ane TPI thorttle bodies and all the larger I go is 52mm. I have measured the remaining wall thickness on a 52mm that has been ported and there isn't enough casting to support a 54mm bore.

I just though I would post this because the guy's 54mm ported thorttle bodies are not 54mm.

 

Thanks 97'. He said the 54 is the biggest they can go, but I guess he is lying. I will go for a 52mm since I have heard through the grapevine that the manifold is 52mm stock anyway so that should match up PERFECT. My buddy tonight told me that he thinks that the 52mm will take some torque away but rule in the topend , what do you guys think?! Thanks again---