KGM:

Thanks for the advice on the tubing. RAMAIRBOX.COM also offers neoprene in 5-inch. I'll take that one to heart.

Anyway, I did the math (haven't flexed the fluid mechanics muscle in some time). Some very interesting/provocative results. The bottom line is that some of you, especially the REALLY fast guys (especially Ruslow) might want to consider building a system. Let me explain.

Here were my assumptions for the calculations:

No flow losses through the ram-air duct system (not a great assumption - but a tough calculation)

No flow losses through the flat stock air filter element (not the greatest assumption, but the losses are VERY LIKELY small).

A 5-inch round ram-air duct.

Per Eaton website, 700 CFM flow at redline/WOT (5400 RPM engine speed).

By direct calculation, 350 CFM flow at 2700 RPM.

Stock air inlet to the airbox blanked over, system sealed (true ram-air setup).

Standard temperature and pressure atmospheric conditions (geek stuff).

A properly sized/designed scoop in clean air, normal to flow direction.

Here are the results. I hope this works out. The results are in PSI above or below atmospheric in the top chamber of the airbox (MAF inlet).

SPEED @5400 RPM @2700 RPM

20 MPH -0.54 PSI -0.03 PSI
40 MPH -0.12 PSI 0.042 PSI
60 MPH 0.00 PSI 0.347 PSI
80 MPH 0.17 PSI 0.946 PSI
100 MPH 0.63 PSI 1.84 PSI
120 MPH 1.39 PSI 3.03 PSI
140 MPH 2.44 PSI 4.51 PSI
160 MPH 3.79 PSI 6.28 PSI

This is the ultimate, best potential ram air effect. These pressures will be reduced by flow losses in the ducting and across the airbox, leakage, and any obstruction of the scoop.

Nonetheless, there's a lot of potential gains to be had with a properly designed/fabricated/installed system. Of course, you also might rip the lid off your airbox at speed as well, although the thing looks pretty tough.

My best guess, accounting for all losses, is that you could definitely get a positive pressure (relative to atmospheric) at the MAF at speeds above 80 mph or so, possibly at lower speeds depending on your shift points (RPM at speed affects the pressure due to the engine drawing air faster/slower through the ducting).

And how about getting 4 PSI or so of pre-boost at 160 mph (Ruslow - take note). That's a TON of horsepower right when you need it the most.

Realize also the tremendous forces trying to rip your scoop loose at those speeds - 4 pound-force or so per square inch of projected area. Bolt the thing down tight, and build it strong.

Wonder why the F-Body guys spank you at high speeds? Aerodynamics and ram-air explain it. The faster they go, the more power they make. It's for real.

 

KGM:

The RAMAIRBOX.COM stuff looks pretty good. Their numbers check out also - they quote (without any supporting detail) that 2 inches of mercury pressure is available up front in the grille. This equates to about 1 psi which is approximately the stagnation pressure of air losing 60 MPH of velocity. Probably based their calculations on complete stagnation of air at 60 MPH (like against a flat, hard part). This won't be available at the MAF, of course, since the air in the duct is moving at some velocity - the air won't lose all of the 60 mph. But you get the idea.

All of the commercially available vacuum gauges go right down to 30 inches of mercury (a total vacuum), so any will cover the range of "suck" in the airbox. Lots of experiments to do.

You would do well to enlarge your system to 5-inch ducting. You get 56 percent more flow area, whcih drops the theoretical speed need to get the ram air effect at redline from 91 mph to 58 mph. A 4-inch tube just isn't big enough to feed the Lightning engine, if you're trying to get ram-air pressurization. On the other hand, running a 4-incher in addition to the stock inlet just about triples your inlet area, so let's keep everything in perspective.

Just curious - where did you mount your scoop, where did you route your duct, and why? Also (most important), how much louder did the intake howl get, and did you see an effect on your indicated maximum boost pressure?

 

All:

What do you think about this...

In stock trim at redline, the pressure at the MAF inlet, by my wild guess (we need some measurements), is probably somewhere around 12.7 PSIA (4 inches of vacuum). Most folks are getting around 10 PSI of indicated boost (24.7 PSIA) with a stock airbox setup. This works out to a 1.94 compression ratio. Recall that our blower is a positive displacement pump/compressor.

With the much-discussed 5-inch ram air setup, we have the ability to easily get 2 PSI or more overpressure at the MAF inlet at redline (at speeds above 120 mph, less for lower RPM). This is 16.7 PSIA. With the same compression ratio (1.94), we're looking at 17.7 pounds of boost (32.4 PSIA) after the Eaton. Zowie! Even at the break-even point (no vacuum or overpressure at the MAF inlet), you're looking at 14 PSI of boost.

This assumes that the restriction in the intake tract previous to the blower is from the airbox. There might be gains to be had from opening up the MAF and throttle body (as some have done). Just looking at it, I think my assumptions are, for the most part, correct. The boost gains everyone has seen from going to an aftermarket filter support this.

Any thoughts?

 

all-

I have been looking to something similar to KGM's idea also.

How much more work for a 6" duct? I know the diameter is over kill, but I noticed that Delta Tools (the distributor of the Blastgate connector that KGM used) also sells a 6" Blastgate....

KGM... Do you have a website for Delta or Blastgate, (whatever) on the documentation that came with your blastgate?

 

Actually i did a search... DUH!!!

Check this out.... a 6" Blastgate!

They also have 5" "hose"....?!

http://www.deltawoodworking.com/cata....asp?cat_id=26

 

Guys,

I found this post very interesting. I have said all along that pre-pressurizing the air charge to the S/C should have some benefit.

As you can see from my sig., I have JL's "ram-air". He and I have e-mailed back and forth on this one. He said he tested a setup like the one you and I are talking about and realized nothing. In fact, he said just the cold-air wash was better.

So, I bought his setup and did experience significant gains over the stock setup. But, I'm a hands-on person and I'm still contemplating doing what Siver-Y2K-SVT is making just to be proved wrong. Well, hopefully I'm wrong after forking over $$ for JL's kit.

JL, you can step in anytime and shed some light on your testing and if I have mistakenly misquoted you.

------------------
Jim
Black '00
#1,757 built 3/30/00
Clear corners
J.L. Single program
J.L. Stage II ram-air

[This message has been edited by gforce (edited 01-04-2001).]

 

This post proves just a little knowledge can be dangerously funny. You really got me with all your calc's ect.. Was going to quote a couple lines but its just to damn FUNNY..to quote just one. Hope you don't take yourself to seriously. Great snake oil though,, Thanks for making me smile..LOL

[This message has been edited by MNLightning (edited 01-04-2001).]

[This message has been edited by MNLightning (edited 01-04-2001).]

 

Gotta love this post.
Why not just take the drivers side headlight out and fabricate a scoop in place of the light. Seal up the fender opening, and attach the scoop to the front of the aircleaner.
When you go to the track pop out the headlight and put the replacement light/ram air scoop in.
To me this seams like the most direct and shortest path to the air cleaner.

 

Silver...Your are a hell of alot better at math than I am. I went back to look at the pictures I posted awhile back (Ram Air Pics) if you do a search, and a 6" blastgate looks like a pretty tight fit. Also I hav'nt seen a 6" scoop anywhere yet. Maybe your guy can fab you a nice one. I cut out some of the plastic fender liner to run the hose up to the box. I'll go out and take some more pics for you. A 6" hose is going to be a good trick to get up there, But I always say "more is better"...good luck!

 

Damn good thing no one cared about MNL's opinion in 1996 when they started talking about putting a SC in a TRUCK.

What WERE they THIMKING!!!

 

hope this works, like I said I have a new 4x11 scoop coming.

 

MNLightning:

Glad you found this so amusing.

All:

What's so funny?

 

KGM:

Do you have any clearance issues between the tire and the duct? I did some measurements last night and it looks a little tight at full steering lock.

Also, how does your system sound? Lots of howl?