I am sure this was discussed many years ago. TPIs made an air foil for our throttle bodys. Debate is whether it made any real gains. TPIs has a great reputation and I am not digging on them.
But, It was said that the top of the air foil was blocking a majority of the air that goes into the top of the throttle bodys cavity which then allows fresh air to go to valve covers, on LT1s at least. This could cause blow by due to lack of air getting in there, decreasing the effect of the PCV system..
Anyone ever have this issue?
Now there are many air foils out there.

 

I just bought an airfoil off Amazon. Before doing so, I researched the topic of whether the airfoil does anything. Based on two separate tests conducted on airfoils, and I believe TPIS' own marketing, the airfoil increases airflow about 40 CFM. Increase is probably a bit misleading. I think it's more of "restores" the potential that was already there. Since the 48mm openings are not changed, thus not really increasing capacity, it lends credibility to the claims that the airfoil "smooths out the incoming airflow" allowing the two openings to maximize their potential.

When it comes to horsepower, the only testing I've read about is from Motor Trend.
Dyno Testing 7 Popular LT1 Engine Modifications

During testing, MT stated that . I have no idea what kind of math they are doing. From their own number, average power and torque are up by 5 and 6 respectively and peak power and torque are up by 3 and 9 respectively. A 20% increase on their test engine would amount to well over 60 HP and TQ. Someone please enlighten me...maybe I missed something.

As for the blockage at the top...based on my own airfoil I just got, not much of an opening. However, the bottom opening leads to not only the IAC, but there is also a vertical grove behind the foil that may direct air upwards. I wish you had posted this before so that I could analyze the design. I can, however, suck (yikes) through the tube and gauge flow resistance (damn, this sounds all sorts of wrong).
My TB is still out of the car...awaiting refurbished balancer before I reinstall it.

I did see a video on youtube..a guy claimed his Holley band airfoil blocks all air flow, top and bottom causing issues. Looking face-on, it does not have the same opening as other airfoils; but I don't know if it has an opening underneath.

To be honest, this is the first time I hear of such issues.

Ric

 

I have never heard that the airfoil interferes with the airflow to degrade the PCV system.

I have a TPIs air foil and have used it on a couple of cars. In practice, I could feel no changes in power. The only thing I noticed was that at low speed when pushing the gas pedal I had a slight bog. I later replaced the computer chip and the computer was able to handle it without a bog.

The biggest concern is that the attachment screw can come loose and then get sucked into the engine causing lots of damage. If you are using an air foil make sure that you use a thread locker!

Good luck.

 

Take a look at the C4 TB's that have them built in. I forget the brand but there are a few you can buy new and are shaped just like the screw in air foil.

 

Further information on the airfoil.


Personally, I think this test while valid does not fully explore all the possibilities.
- It's done on a TPI engine, which runs out of breath at 45-4800 RPM
- It's done on an engine that produced about 170HP to the wheels. Adding the 20% for drive train loss, this is a 205 HP engine? The 89 was rated at 230. Is this engine slightly hurt or just old?
- So they test with the stock intake ducting for base-lining and then remove it to test the airfoil and K&N filter. What did they do with the MAF? Did they run it in limp mode or open loop?

As smart allecky as they are on the video, they discredit themselves by adding variables and creating further speculation.

Do notice in the comments section...Jim Hall himself has a discussion with the two subjects regarding the test.

In my opinion, this piece of hardware is more suited to the LT1, and even more the LT4 where air velocity is higher.

 

I remember an individual from Australia, Case? was part of his name. He made comment and people shrugged it off, till another person brought it up..
I can see if there is no way for fresh air up to the top of the throttle body, then , yeah, I can see an issue.
I guess the question is, how much air is needed to allow the tube from throttle body to valve? That would be an engineering question.
My car has low tension rings, so, anything to assist in breathing pressure out of the crankcase is beneficial. My PCV goes through a coalescing filter, same type used on Air compressors.. It does collect oil.

 

The built in ones have big holes up front for the air to go to IAC and upper place.. I have an AS&M, Holley, TPIS and even BBK did it.

 

Here is a thread a coouple guys talked of it.
Air Foil This post is different. I promise - CorvetteForum - Chevrolet Corvette Forum Discussion

 

The best would be to measure crankcase pressure in your custom build. There are some videos on making a custom sensor that are fairly simple.

 

Ah I found some old photos that might help. Also I remember making a thread about it but that is many years back.

 

If you purchase the air foil that comes with a window decal it will provide 15 extra HP, but you have to place the decal in a specific location on the rear window to actually work.

 

In your last picture, I cant see it, but is there a hole drilled for the IAC at the bottom. It is usually an 1/8 inch. Allos air from IAC to go into hole in LT1/4 manifolds.


See it in this pic at bottom
Was yours on an L98?

 

My pix are a L98 52 mm TB. I also looked up my old thread and it may be further confusing lol so that picture above I ground out the solid block between the two butterflies. Here is the thread:

https://www.corvetteforum.com/forums...r-pcv-air.html

 

Ws6.com airfoil dyno results showed peak +1hp and +5tq. Under the curve was a tiny bit better, like +4hp and +6tq.

 

Minimal HP/TQ. Temperature changes can make that much..

 

I checked my airfoil when I got home. I can blow or suck air through the tube easily. It comes in through the bottom orifice, but also through the small gap at the top. See my picture above.

For me, this is enough to keep it in place.

 

I think the LT1s needed more air than the IAC original channel had, thats why it came with a hole drilled into it. This allowed the IAC to work better. It was a higher hp engine and required more air to idle.