I took my stock intake from my NA 7.3 F-250 that sat above the radiator, stretched it with heat, turned it sideways and mounted it next to the radiator (after cutting out part of the radiator mount) on the drivers side. The installation is very similar to Dave's. I then cut a piece of 4" corrugated plastic drain pipe to go over the new intake to attach to the Banks turbo and K&N filter. My question is..I have purchased a metal transition that goes from 3"x 10" (30 cu in) to a round 4" (12.5 cu in). I also purchased a 4" round metal flex pipe to replace the corrugated one. The original intake is 16 cu in transitioned into 4" round. My thought was to replace the corrugated pipe with a smooth one to cut down on excess air turbulance created by the corrugations. I also felt 30 cu in jammed into a 12.5 cu in pipe would be better than 16 cu in jammed into 12.5 cu in round pipe. Hence the reason for changing the transition. I have not started the prooject yet. It is going to require some drastic cutting next to the radiator and some welding to support same. Am I getting a little too radical with this whole project and is it worth the effort? Just trying to jam MORE air into the turbo via the K&N filter. Your thoughts please

 

I ran a deflector from behind the grill up behind a cut out behind the light that gives me a measured 3 times the air pressure in the duct than I had with the stock scoop. This on my N/A but has minimal bends, the scoop is 2.75 x 10 inches and is baffled to caputer all the ram air. The pressure measured at the inlet of the 4" section was with a manometer at 50 mph was 3" as compared to 1" with the stock set up.

 

Tom, any improvement to air supply will be benifical...I had an 86 with dual air inlets, worked great. My 84 has a/c so I can't run the same setup...I have basically the setup as Dave S., but I expanded the original opening to 4x11, installed a heating duct and piped it to the air cleaner. what I might do is add an additional air vent just below the bumper, route it thru the wheel well to a y pipe for additional air???

 

Don't you think there is a point where no matter how big the ram air intake is, the 4" pipe will only allow a certain amount in OR do you think a larger intake will pressurize the air in the 4" pipe and FORCE the turbo to accept more air. I'm thinking there has GOT to be a saturation point somewhere along the line. No doubt Dave has a chart that explains that. What's you .02 on this Dave?

 

No chart, but I do have positive pressure between the air filter and turbo instead of a vacuum.

I just did calculations on the amount of air the engine could use in theory at cruising speed and then made the scoop big enough to supply more air than that to the turbo.

My figures are based on 1002 CFM at 3300 RPM and 21 PSI of boost.
Yes that is 2.5 times what a NA 6.9 can take in at the same RPM.
At 3300 RPM in third gear I am moving 50 MPH and the scoop is getting 1222 CFM of air.
That is the closest I ever can get to using all the air the scoop is supplying to the turbo until I drop to first or second gear.
If I do that either a U joint of driveshaft is getting ready to break, so I try not to stand on it that hard in the lower gears.

I have talked to several diesel hot rodders that could not figure out how I could get that much boost out of a single ATS turbo, I had to send them pictures.

And the best part is it will go over 21 PSI and 3300 RPM if I don't mind paying the fuel bill.

 

So if I remember from one of your posts, you have a 4x10 scoop located in the same place as mine and that is supplying a 4" tube to your turbo. You are getting much more boost than I am. If I run approx 2200-2500RPM with a 3x10 or 4x10 and max boost of 10PSI will I have positive press at the filter or a vacuum (of course that would be with an approx speed of 50-70 MPH)

 

The reason I'm thinking of adding the 2nd intake is increase the air volume "pressure" at lower RMP's....I'm not an engineer, but I have tinkered with air supply to the intake for a # of years with some better results than others, in fact I had tried
-2 air vents going to a y set up
-dual air intake [on the drivers] on my 84

While both were an improvement over the stock setup, I still belived it could be better and simpler, so I went with Dave S's setup....I belive that this setup supplied the same air volume as the dual setup I had, with a lot less crouding around the air filter.

 

One correction. His is a 4x10 scoop - but it supplies a 6" pipe almost all the way to the turbo - then it reduces to 4" right before the turbo inlet. That bigger pipe is where he's getting the larger volume of air.....

 

It's imazing Dave S. was able to put in a 4x10 and even more imazing he could run a 6" pipe. I am a little leery about cutting any more frame that holds the drivers side radiator.I already took out the heavy metal radiator bracket and installed an 1/8" vertical angle iron to hold the radiator. Now that I want to increase the scoop size, I will need to cut the heavy steel channel that runs vertically up next to the battery. I'm concerned about weakening the structure. I won't cut the entire vertical piece, just most of the 2 sides of the channel. ( 2 1/4"x1" vertical support of which I will cut approx 3/4"x6" off both sides of the channel). What do you think

 

[QUOTE=Dave Sponaugle]No chart, but I do have positive pressure between the air filter and turbo instead of a vacuum.

I just did calculations on the amount of air the engine could use in theory at cruising speed and then made the scoop big enough to supply more air than that to the turbo.QUOTE]
I presume my turbo would require less volume being that it has a waste gate and only develops 10PSI max of boost. Is that correct? I suppose if I stick with 3"x10" with a 4" tube I will probably have enough volume. I am placing the scoop in the same location as yours. With my air conditioning in the way, I would have trouble installing a 6" pipe.

 

Ok, works something like this.
With 31" tires in second gear at 3300 RPM you are going 55 MPH with an E4OD and 3.55 gears.
So let's use 60 MPH for calculations.
60 MPH = 1 mile every minute

5280 feet in mile * 12" = 63360 inches every minute of travel.
63360 * 30 Sq. In. = 1900800 cubic inches of air scooped every mile.
1900800 Cu. In. / 1728 cubic inches in a cubic foot = 1100 CFM.

444 cubic inches for a 7.3 * 3300 RPM = 1465200 cubic inces of air
1465200 / 2 for a compression stroke every other revolution = 732600 Cu. In.
732600 / 1728 = 423.95 CFM with no boost

14 PSI boost would double the amount of air your engine would use, but you are only getting 10 PSI.

So 423.95 / 14 = 30.28 Cu. In. per pound of boost
30.28 * 10 = 302.8 Cu. In.
423.95 + 302.8 = 726.75 CFM of air required at 3300 RPM and 10 PSI of boost.

1100 - 726.75 = 373.25 CFM of excess air
This number is slightly lower because we rounded up from 55 MPH to 60 MPH, but I think it will be safe to say that you are going to have a positive pressure at your turbo.

I removed the drivers side radiator bracket/spacer completely.
I also trimmed the flange on the radiator flush with the back of the channel mounted beside the core.
Then I cut part of the radiator shell flange off as well.
After all that I fabricated a new bracket that drops down from the top of the radiator shell to suppport the radiator on the drivers side top.

I have another plan for more air, but I never have time for everything I want to do.

One of these days I am going to have to get another truck so I don't have to drive mine every day. If I had a couple days at a time that I could continue working on it without putting it back together every night, I could get more done.

 

Thanks Dave. That puts my mind at ease about cutting the frame. I was afraid of compromising the integrity of the frame that supports the radiator, headlight assy, etc. I did the same thing with the new brace. The calculations you supplied were great. Thanks a lot. Tom

 

I can not say the calculations are exactly right.
I know the math part is correct, but I only have real world schooling on turbo's.
No hang on the wall kind of experience at all.

I just know it works for me, and that is the calculations I used to size mine although the numbers were rather different.

The bracket I made to attach to the top of the radiator to the radiator sheel is made out of 1/4" x 1" flat steel.
It has been in there for 3 years with no problems at all.
The off road conditions I am in every day or two is best described as extreme.
Lots of body and frame flex is normal when you drive up roads built for dozers only.
If mine stays in place with where I go, hauling as much weight as I do, you should have no trouble at all.