52mm Throttle Body

[Hrtbeat1]

Ok I just upgraded from my stock 48mm to a BBK 52mm TB. Came with all new gaskets ect. Went on with out a hitch. One thing I've noticed is a large sucking sound now. Almost the same as if the Air duct was removed from the front of the TB. Is this normal? Has anyone else experienced this? Was the engine really in that much need of more air? The performance gain was subtle and the gas mileage dropped a bit, but this was to be expected.

 

[WhalePirot]

Until I design a custom cold air intake,

My 52mm BBK makes a similar sound, but I only have a tube and a cone filter at this point. Others could note that the BBK is fabricated like the stock units WITH an airfoil.

Ensure that you have no air leaks, especially 'behind' the BBK and that the intake nozzle is properly secured. That rubber deal can be a real bear to get on, ALL around the TB. The former allows unmetered air into the engine, causing the ECM to scratch its electronic head.

mike

 

[Vettefan87]

When I put Ram Air I got a very similar sound, at first I thought I might have had a leak but I went over everything and I didn't. Was the original design that crappy, that it starved the car?

 

[Ken]

Ya oughta hear my 58! :cool

 

[bossvette]

Ya oughta hear my 58! :cool

Yep like a shop vac on steroids, especially with just a K&N on the front of it

 

[maxrevs85]

Ditto Ken, I stuck my hand over the Maff "58"inlet and damn near sucked my hand in....whew thats some draw!!Reminded me of one of my old ....ah nevermind ....

 

[Ken]

Did I ever show you guys this one?

Talk about sucking some air - imagine what it must have been like when the secondaries on those quadrajets opened! :eek

 

[Hrtbeat1]

Mike (WhalePirot), Ken, and bossvette thanks much for your input. It makes me feel better knowing that others have heard the same thing. I thought I had a leak .... somewhere ..... I even tried putting on the factory duct/filter assy. and still heard it. After that I figured the car just needed that much more air.

I am running a straight shot TB to air filter. Its a little tight but I secured the air filter before installing the TB. With the speed density system I can hook up the K&N right to the TB, which has run better IMHO so far ... I don't have any dyno data to prove it but as far as throttle response and seat of the pants I think it helped. When I put the 52 on I heard the suction and "thought" I felt it. Maybe it was just the knowing that I had put it on ... but I swear I felt it.

Like I said the mileage has gone down, but I expected that. Then again cruising around +10 for 400 miles probabally didn't help. Hey I only dropped 2 MPG. I like the feel though.

Ken That dually would most likely suck the crome off any nearby bumper. :L

Thanks guys,

 

[Mad-Mic]

if your L98 is midly stock and not wild then you'll actually loose HP. the 48 mm tb is rated over 600 cfm and the 52 is in the 750 range. you'll not only loose HP but alos throttle response. no need for a 52+ tb when guys are running 48 mm TB's in the 11's with no starvation. the bottle neck is not in the TB but rather in the plenum. if you didn't port your plenum and the car doesn't need anymore air due to no major mods then it's a waste of money.

 

[Edmond]

the bottle neck is not in the TB but rather in the plenum. if you didn't port your plenum and the car doesn't need anymore air due to no major mods then it's a waste of money.

Mic,

Do you think porting the plenum alone would get me any gains?

 

[Hrtbeat1]

Ported Plenum

Thanks Mad-Mic,

I was hoping that you would chime in. I know you have you're Vette tuned very well. This is just another step in the long list of mods that I have planned. I ported out the plenum (actually a second plenum I picked up somewhere along the way). The next thing will be some large tube runners. After that a larger flowing manifold ie big mouth. Further down the road I will go with the GM hot cam and 1.6 ratio rockers. If that still isnt enough ... theres never enough is there ... then I'll go with some new heads and maybe even punch out the block, and drop in a stroker crank.

So far I've done some little things, 160 stat and switch, TB bypass, March pulleys, some chip tuning, and a more free flowing exhaust. Im sure there is more but I just can't think of them right now.

 

[Da Hawaiian Punch]

Thanks Mad-Mic,

I was hoping that you would chime in. I know you have you're Vette tuned very well. This is just another step in the long list of mods that I have planned. I ported out the plenum (actually a second plenum I picked up somewhere along the way). The next thing will be some large tube runners. After that a larger flowing manifold ie big mouth. Further down the road I will go with the GM hot cam and 1.6 ratio rockers. If that still isnt enough ... theres never enough is there ... then I'll go with some new heads and maybe even punch out the block, and drop in a stroker crank.

So far I've done some little things, 160 stat and switch, TB bypass, March pulleys, some chip tuning, and a more free flowing exhaust. Im sure there is more but I just can't think of them right now.

I took mine off because to me it felt like it lost some ummff on performence and put the 48mm back on and now seems to really work much better.
If I had known you wanted a 52mm I would have givin you mine, it was a BBK also and it does make a loud sucking noise also.

 

[maxrevs85]

Going from a bigger to a smaller TB, is like going from a single plane carb manifold to a dual plane . you lose top end but gain bottom end . It feels better because the torque is better down low. I have a 58mm and i went back to a smaller one for testing and the throttle response on the bottom was good ,but , after about 4800rpm , it was gone . The 58 was a little softer on the bottom end ,but will pull to 6500 on the top.
I have the tpis setup , manifold runners , afr heads and headers , cam, roller rockers and stroked to 383 and whoooaaa baby , it goes. Thought Id give alittle of my experience.
.

 

[Hrtbeat1]

I took mine off because to me it felt like it lost some ummff on performence and put the 48mm back on and now seems to really work much better.
If I had known you wanted a 52mm I would have givin you mine, it was a BBK also and it does make a loud sucking noise also.

Thanks Punch, I was going to get a 58 but when I ordered it they werre out so I went with the 52. Kinda glad I did it's like a happy medium. BTW the tranny feels really good silky smooth unless I really get on it then its real firm. I went with a 1800 - 2200 stall torque converter and this really helps too.

I've got plenty of low end grunt especially with the higher stall converter, but can still let her wind up a bit more. Maxrevs85 thanks for your input. My engine will most likely be very similar to yours .... someday I only get two months at a time to do stuff with mine so I gotta plan and do things in steps.

 

[Da Hawaiian Punch]

Going from a bigger to a smaller TB, is like going from a dual plane carb manifold to a single plane . you lose top end but gain bottom end . It feels better because the torque is better down low. I have a 58mm and i went back to a smaller one for testing and the throttle response on the bottom was good ,but , after about 4800rpm , it was gone . The 58 was a little softer on the bottom end ,but will pull to 6500 on the top.
I have the tpis setup , manifold runners , afr heads and headers , cam, roller rockers and stroked to 383 and whoooaaa baby , it goes. Thought Id give alittle of my experience.
.

With your set up, yes the larger TB prob was a benifit for you, the 383 can use the larger TB, and the AFR heads along with your cam, rollers and some what the headers also, but as for heartbeat and my self (350) with no major mods even close to what you have, the 52 was cool, but it did lack power on bottom end, but top end if it had gains, was very minimal at best, the 48 gave us the kick in the pant's on the low end which more then made up for the slight loss if any on the top end.

 

[maxrevs85]

Actually , I would like to try a 52 mm , they still pull over 750 cfm. I realy might like it.

 

[Ken]

Okay, one more time for everyone's benefit:

If you install a larger throttle body on an otherwise completely stock engine, don’t expect much of an increase in horsepower. If the engine can't make use of the increased airflow due to other (air) restrictions in front of or behind the throttle body, it won’t be able to produce much of an increase in horsepower. In the case of a bone-stock engine, a larger throttle body probably won’t hurt performance, but it won't help much either.

Once an optimum intake design has been chosen, it becomes important to tailor the throttle body (or carburetor) to suit the overall package. Quite often there’s a tendency to use too large a throttle body or carburetor for a given engine. Size is usually determined by engine displacement and maximum engine speed, or rpm. There is an equation for determining throttle body (or carburetor) size (CFM = (RPM x displacement) / (2 x 1728)), the end result being the maximum air requirements of the engine.

The key to choosing the proper size is velocity – the same theory used to choose an intake, although it’s more critical here, since the throttle body/carburetor supplies fuel to the engine by “measuring” the pressure of the airstream as it passes through the throttle bores. If the throttle body or carburetor is too large low-speed drivability and idle characteristics can suffer, and a false pressure signal will be generated affecting fuel delivery, resulting in a poor running engine.

The best method for determining a proper throttle body or carburetor size for your particular vehicle is to consult the various manufacturers for advice. They will ask you about your particular engine combination, the intended use of the vehicle and other pertinent questions and make a recommendation. Once again, optimum size depends upon how large the engine is and what rpm range it will see.

Typically, throttle body size is limited by application (unlike carburetors which come in a large assortment of sizes), so by doing a little basic research it’s usually not too tough to determine which is the best for your particular engine.

 

[maxrevs85]

Can I get an AMEN.......

 

[Da Hawaiian Punch]

Can I get an AMEN.......

Amen!!