Vlocity

Guys and Gals,

I have been thinking about this for over a year and finally took the plunge. It is rather daunting taking a cutoff wheel to a PERFECTLY good hood. This is the next step after building my splitter with diffuser last year.

The vent is a $60 E-bay find that I had to heavily massage to make work. As in cut it apart and glass most of the rear. The problem with it was that the hood it was intended for had a substantial crown and our hood is relatively flat in that area. So this is NOT a cut and drop in deal.

I identified the low pressure area of the hood through the wind tunnel tests conducted by Porsche on the 928 and installed a vent in that area.

The total vent is over 70 square inches. The leading edge has a nice litte lip that is about an inch tall that will give some added benefit and insure low pressure behind it on the opening side.

I have also built a couple of "spats" on each side of the blower snout to act as a "barge board" to keep some of the air from washing over the top of engine.

I found a new "medium" to work with. COROPLAST. It is light flexible and if I need it to bend, I run a wire through the core. This is the same stuff that campaign signs are made of and I bought and entire 4 x 8 sheet in black for under 30 dollars.

I built some rather low tech pieces with coroplast on the inlet side of the radiator. Mainly directing the flow into the radiator and not letting the
air cascade over the top since my engine air inlets are no longer of use. So I think I will have increased the pressure on the inlet side.

The barge boards set just on top of the distributors and as you can see they are removable.

I was going to hold out and post this when it was completed, but with Mark's inquiry I might as well show you what I've got. Oh and disregard the hood misalignment, its just setting on there right now.

Please keep in mind that this is a 85% DE & Track Car.


Best regards,

Ken

svp928

Actually looks pretty damn good!

IcemanG17

wow...very nice....I need to add a vent on the lemons racer....some extra downforce would help, but mostly I want to vent the hot air!

GUMBALL

Nicely done! and well thought out!

I would be interested in seeing a with/without comparison of engine and underhood temps.

Just another thought, (seeing that it is a car used on track) I would be interested if you notice an increase in front grip with the vents open - I am wondering how much it would reduce air built up under chassis . . . . like I said, just a thought.

mark kibort

I already did the tufts test, and there was a substantial flow out of the vent at 100mph. Now, does it produce downforce? yes, but Im sure it is very slight, but it all adds up. spliter, vents, etc. with the hood vent and a splitter, I was able to correct a push condition with my race car. I wasnt able to close off the vent to see what part of the fix was due to the vent.

Ducman82

anyone ever try a Cowl style induction hood?

mark kibort

that's how half of my air gets to the engine

pcar928fan

Forget the vent, I want your garage floor and decor!!!

karl ruiter

Shouldn't the gills be on the side?

Vlocity

Thanks. I have a LOT of time in getting it to look this good. I wanted it to be functional first and not something that would cause me to cringe everytime I looked at it. It looks better in person.

I saw an engine tempature decrease last year with my splitter and diffuser that has the air directed over the oil pan. I was able to remove my two pusher fans that were in front of the radiator last year as a result of the splitter.

With the new deflectors and cowling that I have now built for intake side of the radiator and the additional vacuum that the vent will create on the backside, I hope to see another small decrease in engine temperature. I also hope to see a few degree drop in intercooler temperature since my heat exchanger is where the AC condensor used to be.

The air flow through the radiator does have some engine cooling effect, so that is one reason that I made the barge boards removable. The barge boards are there to help direct air out the vent and not let the air get tangled up in all of the mess that is the top of the motor. My exhaust manifolds and the entire exhaust are heat wrapped in order to reduce underhood temps.

That is the whole idea. First, Increase airflow through the radiator by providing a vacuum in the low pressure exit of the hood to increase cooling of the radiator and heat exchanger for the intercooler. (The lip on the vent also aids in creating low pressure in the vent area) Second, reduce some of the airflow / cushion of air from under the hood and under the chasis and lastly add some of the airflow to the area over the top of the car that will eventually arrive at my vortex generators, rear wing and gurney flap.

The cowl style hoods are mainly for engine cold air from a high pressure source. My engine air is from a 1050 CFM 4 inch filter that is in the passenger side wheel well. You will note that our cars have a seal from the cowl to the hood to keep that high pressure air from getting back under the hood and having to exit under the car. With all the work I have done to limit some of that cushion of air, I don't want the cowl area open. I do have a spare seal that I have cut down though in case I see an underhood temperature problem, putting in a partially cut down seal would add some cold air.

I am taking high pressure air from between the seal and windshield as my fresh air source for the drivers side valve covers. I am using a small filter and zero cracking pressure valve to introduce fresh air into the engine to aid crankcase ventilation.

Mike Frye

I LIKE IT!

I'm thinking of doing something similar with my spare hood, except I want to see if I can drop down the part behind the vents kind of like a Ford GT. Very nice and functional. Nice work!

Vlocity

Thanks Mike, I thought about that design as well and I think it would look great. The problem I have is that my blower snout extends so far forward and is so tall that I could never make a radius. With a NA motor I think you could pull that off.

Regards,

Ken

SeanR

That looks really sharp, well, the entire car looks fantastic so this is just an addition to it. Well done.

Vlocity

Here are a few pictures of the radiator inlet deflectors.

As I mentioned above I made these out of Coroplast. These pieces mount against the heat exchanger for the intercooler that is currently out of the car for repair, so there is no gap at the top. I have a small piece of foam that slips into the headlight pivot arm cutout on the right side of the picture to seal that off. Even if I forget and pop the lights it just presses the little piece of foam out of the hole.

The idea here is to keep the air directed toward the core and not let the pressure on the inlet side drop off. Normally after the air passes through the bumper cover opening it expands and slows, then either finds its way through the radiator or up into the region where the engine inlets are located.
You can see that with my deflectors I have greatly reduced the effective "opening" size.

I use foam adhesive seal between the heat exchanger and the radiator at the perimeter of the core to prevent leakage of the air out the sides.

You can see in the picture from the post above where the IC Heat Exchanger sets and how these mate up.

I also have a Request.

There are NUMEROUS threads in the forum that debate the THEORY. I would appreciate everyones indulgence to limit this thread as much as possible to the EXECUTION and APPLICATION of that theory.

Thanks,

Ken

Carl Fausett

Nicely done. Will you be getting before-and after engine temp numbers so we can see how it affected engine temps?