pappy92651

Here's the hardest part (attached). How do you get positive pressure to the air tubes, provide a path for water containment, and leave the stock system intake intact? This mod is completely reversible and will not ruin the value of your car. So Far, so good. Tomorrow the Lexan (polycarbonate sheet) stiffener goes on and I change the bell mouths.

jorj7

Steve,

The water containment might be as easy as putting a hole at the bottom
of the hose where it bends up:



But i think unless you connect the new intake hose directly to the original intake
hose, you'll lose any the additional intake pressure. You'll still have cooler air,
but the volume may decrease since it'll be defused in the chamber in front of
the original intake inlet. It seems to be a large inverse venturi....

WallyP

A friend did quite a bit of wind tunnel testing for a major auto company. The air passing thru a radiator is fully stalled, and the air speed thru the radiator is 13 mph! That makes it sound as if the entire area in front of the radiator may be at high pressure.

Sierra Shark

George (jorj7) is correct. Unless you connect directly to the original intake tubes you are losing volume and pressure. True you are recieving some cooler air. Think of a garden hose. If you pinch off the flow the water mid-stream the outlet flow decreases. Also you are taking in a large volume of air and trying to force it into/through a smaller suface area (the opening of the air tubes on top of the radiatior) without connecting the two. Unless that open area in between is under hugh vacuum you can't force the air through the original intake tube opening quick enough. If you connect the two sets of tubes you will create more mass flow. However, you are still faced with the problem of going from a large tube (large volume) into a small opening and back to a large tube (volume loss). At the very least you will need to seal off the intake (filter) box from leaking air (which they all do to some extent). Even though you report to have cooler operating temps I would be curious to know if having those tubes hanging in front of your raditor will have any long range negative effect on cooling such as hot weather driving. Also, if you connected the tubes to increase volume and pressure what effect does this have on the MAF? Aren't those tuned to a certain frequency?
Man, you are so close! Keep it going and keep posting. This stuff gives me a great big.............

pappy92651

George, I absolutely agree with you. I think that there is more to be had if you connect the hoses. The big problem is how to do this without chopping up the car. The best way to maintain pressure is to run one hose all the way to the inlet bell mouth. No question. I am getting positive results and I will post some data at the end of this dialog. I would be willing to bet that a setup with bell mouths in the high beam location would produce measurable gains.

Wally, Thanks for that data. It appears to be true. Since my latest version of the induction system is producing noticeable performance increases I see the possibility to improve slightly by playing with inlet locations and using a continuous hoses to the air box.

Sierra Shark, I also agree with you (and George). If I could find a way to connect 1:1 from the bell mouths to the air box that would be perfect. I cannot see a way to do this easily. An adapter plenum would have to be very thin to pass over the radiator. Go under the radiator? Put a bulge in the hood for clearance?

As I understand the MAF it is a hot wire type and responds to corresponding levels of mass flow by temperature deflection. It does not like turbulent air blowing directly on it. Some of the racers have abandoned the MAF because of related problems. I discussed this with Louie and he said that the stock configuration can handle increased mass flow as long as you don't change the air box radically. Some of the guys who tried running LH cars (qualified as 87 and later) with the air filter top off saw weird results. The car surges a lot during normal driving.

See my previous post regarding water temp readings. With the new induction set up my gauge reads 1/2 most of the time. In stock configuration my gauge reads near 2/3 most of the time. My operating water temperature dropped. Temperatures drop even more above 60 MPH. At idle I saw no change, stock or modified.


Results:
No power drop after sitting at idle for 5 minutes, air box near ambient, 70F.
0 to 60 MPH ET dropped from 4.6s to 4.5s
Wheel spin now in both first and second gears
Definitely more torque on the freeway and above 4500 RPM

Air Box pressure? unknown
Air Box temp = 70F at idle, 50F at 100 MPH, ambient was 68F

So I'm done with this experiment for now. I eliminated my stop light to stop light power loss (heat soak). If someone finds a way to route high pressure air without major structural changes please let me know. I would love to try it.

Thanks for the input guys! Now back to the intake manifold project.

Adam C

Steve,

As far as chopping up the car goes, what's the big deal? This would be a very simple deal to connect the air hoses to the ones you made by eliminating the bell mouths.

You are keeping the car anyway aren't you?

It would look stock if executed properly.

Nice work though!

Barry Johnson

How about just making a couple pieces out of fiberglass that look like the plastic tube ends behind the radiator to connect down to the new inlets?
Also, why the lexan cover? If you're going to connect the tubes directly together, why would you want to have an air barrier there? Wouldn't that (at high speeds) create more drag since the high pressure area in front of the radiator has no where to go to? If the lexan was gone, the air could continue to travel up and over and hit the engine and provide its minimal amount of cooling that way, and not be blocked off.
A friend has an '84 S that he has made a duct in his hood with a custom bent intake tube that has a filter sitting directly against the duct. He has gained some serious airflow with this, and at high speeds he has so much air that he runs lean and can't safely exceed 120mph. But, we know that this system works, if you can get the fuel to keep up.

pappy92651

Adam, I hear what your saying and agree, but it won't happen this time around. I am MORE than happy with the results. The car is spinning the tires in 2nd and chirps the tires when I hit third (on an AT with 285/30-18s?). I will have to give you a ride some time. It's scary. On the freeway it's a rocket.

The issue is not about whether or not to cut the fan shroud. The issue is about all the stuff that needs to be relocated if you intend to keep the hood looking stock. There is 1" of clearance between the hood and the oil cooler. If you relocate the oil cooler you still have a radiator in the way which is 1.5" from the hood. No way to get 3" of tubing through that convergence unless you fabricate a squashed plenum. Not the best way. Or...

I had another discussion with Louie Ott. The best way to route the 3" hoses would be to create a custom hood that has a raised nose or cut the hood and install a box. That would allow you to run 3" hoses all the way from the air box to the bell mouths at the nose of the car. I am convinced that this would work well. But I want to have a hood made that will look nice.

The reason for the coolant temperature reduction is that the lexan plate prevents the air from tumbling at the top of the hood near the stock bell mouths. More air is being forced through the radiator in a non turbulent manner. Louie sanity checked my design and made only one suggestion for improvement. Increase the radius at the hose ends to create true bell mouth configurations. I am also trying to seal the plate a bit better (reduce pressure leaks).

I abandoned the hood scoop at the front of the hood concept. It dropped the intake temperature but that's all I got. The engine was pulling air from a negative pressure zone. Not a very good mod, and it echoes the results that others posted after installing low profile hood scoops.

Thanks for the complement. I need to test before and after pressures to see what I have gained.

Hello Barry, The lexan plate works quite well at channeling air through the radiator (see post above). Why would you create more drag if you closed off an area that is already 90% sealed? The top of the engine gets very little air from the top seal leakage. The S4 front flaps did have a significant effect on drag but they were deleted on later models.

If your friends hoop scoop were located near the base of the windshield or high enough off the hood it should work well. The problem with rear placement for LH cars is that care must be taken to avoid creating turbulence and fooling the MAF. On pre LH cars you have other issues. Has your friend considered a programmable rising rate fuel pressure regulator?


Attached are pictures of the induction version that I'm going to continue to test. A few people mentioned a pressure drop after the plate and vacuum to the air tube bell mouths (and the air temperature drops below ambient at WOT at 100 MPH).

pappy92651

Additional, Look at the cavity under the hood (X). This is where the air flows. The lexan plate and top of the fan shroud are sealed against it (indicated by arrows). Air passes from the blue hoses to the sealed hood cavity to the fan shroud bell mouths. The fan shroud seal is a factory job that I improved by adding foam on the sides of the radiator. Porsche was trying to prevent air from leaking over the top to the engine bay.

The idea again is to separate radiator and intake air, increase pressure to the intake tubes, provide cooler air to the intake tubes, and reduce air turbulence to the radiator (stop it from rolling around under the hood which really is not desirable). Louie also found that at speed the air tumbled in front of the radiator long enough to pick up heat.

Adam C

Awesome work, Steve. Can't wait to go for a ride!

Pierre Martins

Steve you've given me a great idea for my race car, thanks.

I'll have air ducts in the hood where the mouths of the intake tubes are, but i'm still gonna install an air diverter to force air through the radiator. I'm thinking of making it out of carbon fiber.

Anyway, just wannit to say thanks for the idea.

Pierre.

Barry Johnson

Steve,
I'm quite impressed with your research and functional design, and am eager to see the final product.
My friend with the scoops has not used a programmable regulator, just an afpr as far as I know.
Wish I had a 3rd 928 to tinker with now! Maybe its time to get an S model...

Normy

That's all interesting research and construction, but I'm certain that the best you'll be able to do will be to lower temps in your intake a few degrees....

MOONEY aircraft a few years ago mounted an intake right behind the propellor of one of their popular light planes. Their sales literature, from their testing, indicated that at speeds of around 180 knots they were gaining about 1 inch of manifold pressure from this ram intake...or about one half pound per square inch. Speeds lower than 180 knots essentially gave them no supercharging effect.

I may be wrong, but that graph is not showing you pounds of pressure; I suspect it is actually demonstrating some variable known as "coefficient of pressure", which when applied in a mathematical formula could be used to determine the real aerodynamic pressure at various points along the car. Also, that graph is for the dead center of the car, not necessarily where those tubes are mounted.

Not to be rude or anything...but 1/10 of a second 0-60 doesn't show anything. I rely more on 1/4 speeds or times since it is very difficult to take 0-60 readings. I've timed my car with handheld stopwatches and with a G-tech numerous times and neither method is capable of giving me consistent readings. 1/10 of a second came from better shifting or warmed up tires.

-As to construction of these pipes...I've seen model airplane fuselages constructed from glass cloth and resin available at any hobby store. These are light- weighing perhaps an ounce, are formable in ANY shape, and though they would take an evening to make, the reward would be a factory look. You could even make a set of drain fittings. To build these, you get some foam blocks, whittle them to shape, then apply the glass cloth and resin. Voila.

B safe!

N-

Tony

How do you manage to keep the temps in the air box from increasing (2 F') at idle with all the hot air surrounding it? Thats good stuff.

Im more interested in the stall converter in your car. It made a huge difference in your performance!

pappy92651

A word to anyone who might try this mod: Do not completely seal the lexan panel! I just tried this and a strange resonance occurred. I encountered 2 distinct torque peaks, one at 3000 RPM and one 5000 RPM. 4000 to 4500 RPM is the zone where the resonance flappy transitions. What I'm trying to say is that by sealing the lexan panel I killed my broad torque curve.

If you decide to fabricate interface plenums which mate the stock bell mouths to nose mounted bell mouths be aware that you will be changing pressure zones as you transition from 3" hose to plenum and back to 3" hose. I would like to try this, but I think the 3" hose all the way from the air box to the nose is the way to go. It is a matter of what you want to modify to allow uninterrupted 3" hose routing. Louie Ott sent me a primer on work that he has done in this area.

Pierre, You are welcome. The air diverter for the radiator really works well. Temps come down noticeably on the Gauge. I need to place a thermocouple at L2 and measure the new H2O temp for my records.

Barry, Thank you. Stage 2 is pretty much done. Stage 3 will be a custom hood configuration which allows 3" hoses to pass over the stock fan shroud. A diverter will have holes to allow the 3" tubes to pass through and channel air to the radiator for improved cooling. A proper set on bell mouths will be used on the front end.

BTW, did you put that sign next to the cat? He's just napping, right?

Normy, Thank you for the comments. The figures that I'm working from do not come from the graph. It's really just Porsche advertising data which illustrates where relative pressure zones exist. The number that has more meaning is what's measured inside the air box. The entire system is leaky so I really don't know how much of a pressure increase we can expect. I think it's just about colder air at slightly higher than stock pressures. As you stated big pressure gains should not be expected.

H'm. GTECH? Stop watch? Wish I could measured torque at the wheels while driving. That's where having the dyno in the wind tunnel would be handy. You could then model total performance in moving air.

The plenum is worth a go, but the labor involved in relocating the oil cooler is an issue, but I know that it has been done. The method to fab fiber glass plenums is intriguing. I have never done glass molding but I'm sure that I could learn to do it quickly. The custom hood approach allows the use of continuous 3" tubes. If you look at the pressure change when going from a round to flat plenum there is a degree of turbulence. How much will depend on how wide the plenum gets. I'm concerned about resonance created at the pressure drop. It's just another unknown.

Hello Tony, Silver water heater blanket custom fitted around the air box, GTS intake tubes, insulated radiator top, the lexan panel (diverter), and fresh air tubes. I guess I never mentioned the water heater blanket (Home Depot). I stumbled right into it while buying the diverter parts. You can cut it and bond the seams with neoprene cement. Or you can use contact cement followed by automotive silicone on the inside seams. Take the entire air box off and spend a few hours to get a good fitment. A Velcro flap is on top to get into the air filter. You could also wrap the GTS tubes if you want to get really crazy! Looks like a NASA project.

I have a spare 2300 RPM brake stall TC from Edge Racing in the garage. The higher stall speed really effects your 0 to 60 time. There are some diminishing gains from 60 to 100 MPH because your landing in the next gear at 400 to 500 RPM above stock. I did it because I'm running GT cams, 285/30-18s and I'm very interested in my 0 to 60 ET.