Ron U.S.M.C.

I would like to start a discussion about cowl induction. Because this is a important subject not only to me but to anyone running a cowl hood with a open element. Buy the way I certainly appreciate any info.on the subject as to make a educated decision as to whether or not my thoughts/opinions on how and or if cowl induction actually works. This is what I beleave to be true.
The hood is fed by the positive pressure created at the base of the windshield. The 'hood' system starts to become effective around 35+ MPH by providing good clean but more importantly, cooler air. Cowl induction systems work well if put together properly. Usually there is a air box that fits under and around the air filter assembly and seals to the hood when closed. That isolates the air filter from the hot engine air and allowing the carb or TBI to pull air while the cowl opening pushes cold air . Thats the idea. Even when the car is sitting still you can hear my TBI unit pulling air through the cowl and then down through the “x-stream” filter top. Sounds awesome.This is the set-up I am running=

Ron U.S.M.C.

I DO NOT KNOW WHY MY SIGNATURE IS SHOWING TO THE LEFT . I DID NOT WRITE THIS = This is what I have been told = Thats not how it works when your driving,,,the higher the speed the more veloctity will be pulled OUT of that cowl opening...... those rear opening cowl hoods are ment to suck air ( THE HOT AIR ) out ! not in !!!!!!

I would bet ya, @ 80-100 MPH u are starving your motor for air,,,u just don't realy feel it.

On a dyno, it may show positive, on a dyno in a wind tunel u would be supriced !

Think about it !!!!!!

PS.: wind tunnel tests have shown this many times !


Plus, all the belt wear is getting sucked right on to the filter and other engine debrey u don't see .

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iTrader: (14)

i disagree, there is going to be a high pressure built up in that area thats not going away at higher speeds. When you drive on the road with a cowl hood in the rain, you will notice the rain droplets that run up the hood and drip of the back of the cowl get sucked in, done it a few times, on the highway and it never reversed.

i have to grab a pic of what i ended up doing to seal off the aircleaner to the hood, maybe tonight

i would be interested to see the wind tunnel test

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iTrader: (14)

not exactly a 3rd gen, but it shows pressure areas


some other tidbits i found

1. Power Functions
2. As a car punches through the stagnant air at high speed, there are a number of areas that tend to accumulate high-pressure pockets. The front bumper, grille, headlights, windshield and wheel-well are the most common areas.
   
   Since engines make more power with cool outside air than the hot ambient air found in the engine bay, it seems logical to tap these high-pressure pockets to feed air to the engine. In addition to lowering air temperature, increasing the air pressure around an intake artificially crams more air into the engine than the static air could, which is similar to how a supercharger functions.
3. Other Functions
4. Cowl induction hoods are used for a number of other reasons as well, prime amongst which are intake clearance and cooling. Since many performance intakes (particularly those found on carbeurated vehicles) are taller than stock, there may not be enough room under the hood to fit an air cleaner.
   
   The second ancillary function of cowl hoods has to do with cooling. Though these hoods draw in cool air while at speed, when idling or cruising at low speed they go from intake to exhaust. Since performance cars tend to produce excess heat when idling, the ability to vent hot air from the engine bay may be the difference between a fun night out and a melted motor.
5. Aero Effects
6. Cowl induction hoods can help to smooth the airstream passing over a car at speed, but can be more of a detriment to high-speed handling than anything else. If the cowl inductor is not sealed to the intake, the cowl can actually pressurize the engine bay at high speeds. This can lift the front of the car slightly, causing a dangerous understeer condition at speeds over 150 mph.

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iTrader: (14)

so, by this, at low speeds, the hood acts like exhaust, at speed its an intake. If the cowl is not sealed to the intake, you can build up pressure under the hood and cause lift, at high speeds, it was mentioned at 150mph+.

articwhiteZ

iTrader: (56)

first. back in the late 60's and start of the 70's. all the Musle cars had some sorts air pick up."Gimick" and the Cowl induction, was one of them.

the carb was sealed off from the eng. and picked up fresh air from the cowl. did the eng get cool Air..yes..

today most of the Cowl Hoods are not set up like the hoods from GM back in the 70's. you get the looks without all the under hood parts the cars had to make them work like they did in the Day.

alot of guys take time to make the parts to seal off the intake from the eng to get the hoods to work like GM did to get Cool Air into the eng.

do this some time..

take and tape 10 or 15 pieces of 5 " long string in a long line at your cowl.& just inside your cowl. and get on the freeway.. watch how the airflow drives them... will bring a few things to light..

ronusmcmma

it looks like your hood is real close to what GM did back in 1970.

have you ever done the air cleaner lower pan. so when the hoods closed it get all it's air from the Cowl.

the lower Air pan runs about 2 to 3 inchs larger then the air cleaner.. and is sealed to the hood when closed.. car looks good

Ron U.S.M.C.

I have thought of fabricating a air tray for that very reason. Maybe use the existing bottom air cleaner tray and extending out and up with a rubber seal. Its touchy though because of the plastic air cleaner spacer. Don't want to break that.I would need to find a steel spacer instead.Also I have a after market coil that sets real close to the bottom of the air cleaner tray. So would probably have to relocate that. So yes this has crossed my mind. All of this is exactly why I started this thread. Thanks for responding guys.

DAREDEVIL 1

U can all test what ever u guys want , I tell u ..its not working.

The air will get pulled away from the cowl ,,not in to it !!!!!!!!!!


The tape test is a real good idea !!!!!

DAREDEVIL 1

This is an aero dynamic air flow,,,without a scoop or colw and its a mathematic cheme,,,not in a wind tunnel.

2 totaly different things !!!!!!

Pressure points and flow points is not the same.

articwhiteZ

iTrader: (56)

some time ago there was a video of Hot rods in a Wind tunle.

you wil see all the 70's cowl Hoods just pick up air.. it flows over the car and hood .staying about 2 inches off the car..(smoke)
not saying it was ramair.. just a place to pick up fresh air.. it was part of the Musle car hood scoop thing back in the day


mopar had front scoops even a 70 roadrunner had a vac op airgraber hood scoop.(by a button inside the car)
the 70 chevl had a vac op cowl hood goody as well.when you whent to WOT
just to name 2. even the Nascar guys pick up air from there
go check out some of there cars from the 70s and 80s & 90's

all they did was pick up Air.. and the eng would (suck) bring it in.. thats all i have ever seen.

that graf dont show the Hi presher point on the Nose of the car also
this is a spot that Ford installed Air scoops for some of there drag cars back in the 60's
(using the 2 of the 4 head light holes as well.)

they also had a tear drop hood scoop that had pick ups on the Back side of the scoop as well.
on some of there other drag cars..all sealed from the eng.. just used to get fresh air..
Verry cool stuff.

DAREDEVIL 1

I agree, maybe on a 70's car this worked,,,,the air flow was different on a straight nose ,,,not on a 3rd.gen !!!!!!

Anyhow. .......try it and u find out !!!!!!

articwhiteZ

iTrader: (56)

I use air off the front of my 92 Z28 into a ramair set up off the hi point
on the nose(fog light holes). to bring in fresh air.

and the cowl Hood for looks & making room under the Hood..

when i did my hood i could not get a 6" like i wanted.
(nobody) made them in 1992 like i wanted.. so i had to go with a 4"

i like the Looks. my hoods not sealed. and have gone 150MPH on the Hyway.. and have run into the 130's in the 1/4 mile. 10.34

and works verry well..I like it.

Ron U.S.M.C.

This is a photo. of one of the original Cowl set-ups.

articwhiteZ

iTrader: (56)

with the AIR cleaner saying 400 i wiould take a stab as saying thats a 1971
with looking at all the vac lines hooked to it.

DAREDEVIL 1

BUT A 3rd GEN,,,,flat old style front ,,,,,,wind tunnel ..real bad and yes it worked on those.

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iTrader: (14)

i think its pretty ignorant to say that a cowl doesnt work. They do work, its a fact. There are applications that work better, and ways to make a cowl hood more functional, but you cant say they dont work.

Look at a windtunnel test, yes the air travels over the car, but there is also a area at the base of the windsheild that build pressure. Its a similar effect with the bed of a pickup truck. Air flows over the cab, and into the bed hitting the tailgate, then it travels forward back to the cab, and back up and continues to loop in that fashion. That air turbulance stays there and the rest of the air traveling over the tuck rides over it and off the back. Thats why a truck gets better milage with the tailgate up than with the gate down.

On the car its the same deal, the air hits the windsheild and reverses to the cowl, the rest of the air travels over the turbulence and over the car.

do the tape and string test, it does work. If it wasnt so damn cold and the roads salty, i would do it and make a vid. Will have to wait till spring, or if the weather turns.

DAREDEVIL 1

OK,,,take a look and think.

Did this work on that car ????

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iTrader: (14)

sure it did. could be better, but it did work

DAREDEVIL 1

If u think i does.....or did, take a better look and explain to me this ....... same car ( real official pace car from 1969 )

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iTrader: (14)

heres a pic, no cowl hood, but same idea.
The car is breathing from pressure in the cowl area. IF all the air was simply being forced over the car, the engine would not be able to breath, the air would be pulled away from it.
nascar in the snow?, maybe its salt/sand

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iTrader: (14)

see the foam around the aircleaner, it can breath through that.

IIRC the tube to the engine compartment is to allow the car to get some warm air in cold weather so the car would run properly and the choke would function properly. could be wrong. do you think the engine could breath enough through a 2" opening in that tube?

sailtexas186548

iTrader: (2)

or is that salt and not snow.. salt flats?

DAREDEVIL 1

Complettley different !!!!!! Ofcorse this works in that case, now the engine sucks the air from the one flowing OVER the vent !!!!!

On a cowl hood it does not work !!!!!!!! because the airflow on the side is higher then behind the cowl and it will not blow in ,,,it sucks it with the air stream. ( AIR DROOP IS ALWAYS LOWER PRESSURE ).

Don't know how else to explain it right now.

But hey,,,by the way i deal with this almost on daily bases. I RACE BOATS AND DID RACE CARS !!!!!!! ALSO BUILD ENGINES !!!!!!

Thanks,,,i am done here,,,go testing !!!!!

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iTrader: (14)

thats wnat it is, but its a funny pic that kinda catches you off gaurd. My first though was, snow!?

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iTrader: (14)

different app, but same idea
hey, not trying to start a yelling match, just saying a cowl does work. Every drive a car with a cowl hood in the rain? the rain off the hood gets sucked into he engine compartment, engines dont like that, ask me how i know... Oh well, we made our points. didnt mean to start a pissing contest.

Ron U.S.M.C.

So the bottom line is this. I know that there maybe better induction systems than the one I have. I just want to know that I not doing anything to hurt my car. All along I have had faith in the Cowl hood and TBI set-up I have. The last thing I want to do is “starve” my car of “air”. The majority on this thread seems to believe that a Cowl hood with a open element with or with out a x-stream top, and sealed system or not Is a tried and true way to feed your car with air. I mean how many people running Carb. or TBI systems have pretty much the same set-up as me. Hundreds? Thousands?

DAREDEVIL 1

Did not mean to scare u ,,,since u are still open to engine bay, don't think your starving it.
U upgradet to stock but your only on the flow side ,,not on the cool air side since u now suck more HOT air.
If u close it off,,,that would be loosing airflow. My 2 c.
but what do i know ........

Ron U.S.M.C.

Thanks DAREDDEVIL 1 !!!!

89RS_82Z

iTrader: (2)

you are correct and IIRC there was a flap in the cowl (that vac line and the silver thingy controlled it) when the engine was cold it would shut the flap so it could suck warmer air from under the hood

im not sure if the raise of a cowl hood make any differance, but i know you take the cowl seal off of a stock hood to suck hot air out of the engine bay...... i go for someone taping some strings on the cowl and taking a drive and postin videos or pics

89RS_82Z

iTrader: (2)

ok i did some research the flap on the factory hood, its closed at like idle and all but when you hit the gas it opens it up

look at alot of pages and all seem to say that the cowl works but came up with this

there's a low pressure area that develops at the base of the windshield, and allows the motor to suck cool air in through there.

i still want to see someone make a video or pics driving........ or we can wait 6 months or so till i get my cowl hood and see

articwhiteZ

iTrader: (56)

im not sure what the point was...lol

can you get air into your intake from the cowl..yes..
will it work sealed or open at the back..yes.

will it also draw warm air out of the eng bay. if it's not sealed...yes
so will the bottom of the car.. it's not air tight..you know,

is there a presher spot at the bottom of the window at cowl..Yes

is it low? or is it Hi... dont matter air will be used by eng
and will be cooler then a none air scoop car
you will not Suck air away from the eng at the speeds the cars use a cowl hood..

like I posted. nascar uses the cowl for air as the front of the cars are sealed to cut down on air Flowing into the car making drag..Fact
and that eng is sealed.at the front.. open on the sides and bottom..

lets take ronusmcmma car.
will it work better to seal off the air from the eng bay..Yes
he will be getting cooler air into the eng...

as it is now when his fans are running more hot air is flowing into the eng bay from the radaitor at any speed.

if the eng is 195deg
and your air in the eng bay is lets say 140deg temp

why not block that off from your intake and used the 70deg temp from the out side.. say the cowl.. anything is better then useing 140 temp air.
from under the Hood.. even my 89 GM truck takes air off the Nose by head lights..it's cooler air.

are you trying to say that a cowl hood sucks air out of a eng?
or when it's not sealed it draws the hot air up and out of the cowl
making the eng suck Hot air..? (thats why you seal it.)
no air from the eng gets to the intake track when its sealed.

Take my car EFI air off the front..and cowl for looks.
will it also pull hot air out..maby.. will have to do the string test..

skinny z

High pressure at the base of the windshield notwithstanding, something to consider is whether there is sufficient flow capacity through the dozens of small holes that make up the grill in that particular cowl hood.
I don't have the numbers handy however looking at the picture I count maybe 100 1/4" diameter holes. That works out to about 4.9 square inches of available opening. Equivalent to a 2 1/2" diameter pipe. I don't believe you can support much horsepower with a 2 1/2" intake pipe.

DAREDEVIL 1

Its 106 holes. LOL..........

but the question here is DOES A COWL HOOD WORK ON A GEN 3 ???

And i say NO..........does it suck air out from under the hood......i say yes.
This is the little dispute here.

But hopefully somebody will test it and post here.

Like i said...its not does it work its does it work on a gen 3 !!!!????

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iTrader: (14)

you actually counted the holes? thast great. Yea, the small amount of air that those holes can provide is pretty insignificant, all you really going to get out of that is sound. If nobody in a warmer area can do the string test i ccan do it once the salt gets off the local roads. would be interesting to see whats going on, since there is obviously a difference in opinion here.

nobody happen to have access to a wind tunnel do they

i came up with 102 holes....couldnt resist, i had to count them, how pathetic is that....

sailtexas186548

iTrader: (2)

i counted 102 holes!

its in the 30's or low 40's here but i'm gonna go do a string test for you fellas. and my opinion is that there is high pressure at the cowl and the strings will be pulled INTO the engine bay. i have an efi car w/ a tpi air lid so the engine wont "suck" the strings in, it will be only the completely open cowl i have affecting the strings

skinny z

I'll be very interested to see the results of the test. Although I'm certain a high pressure exists at the windshield on a 3rd gen, I'm thinking that if the cowl ISN'T sealed from the engine bay, then the air that enters through/around/under the rad might seek the cowl opening as a means of ventilation (as has been suggested). Sort of like the heat extactor hoods that we've seen.

Ron U.S.M.C.

OK, Test #1 First photo is parked at home with 6 in. strings taped to upper edge of cowl. Second photo is 45mph.They have been puled against cowl and under hood.(I do not have a rear hood seal.) Third photo is at 75mph and you can see the results.Last photo. is on my way home at 35mph. and you can even see where one of the strings has been pulled into the cowl. Thats the best I can do for now. By the way im not cutting any larger holes in my grill. That paint is pristine.

Ron U.S.M.C.

AAAAAAAAAA

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iTrader: (14)

well thats interesting and makes sence, what do you think daredevil1? I would still like to try it since my carb is almost completely sealed to the hood, wonder if there would be a difference.

out of curiosity, did you drill those holes or did the hood come that way?

MotorMouth

The breather they use is sealed all the way aroung. That's not foam it's aluminum painted white.

Yes people that's form the salt flats.

Here is a link to info about this subject.
http://www.camaro-untoldsecrets.com/...es/rpo_zl2.htm

"Chevy engineer Doug Roe, who worked with Product Promotions chief Vince Piggins, found a dramatic performance gain by taking the cool dense air at the high pressure area near the base of the windshield. Ducting pressurized fresh cold air from this area to the carburetor creates a more dense fuel charge with increased volumetric efficiency resulting in more horsepower An approximate 1% horsepower increase is gained for every 11 degree drop in temperature providing the mixture is adjusted accordingly. That means if your engine has a gross horsepower rating of 350, a drop of 43 degrees would net you an additional horsepower increase of 4%, equal to 14 hp, for a total of 364 hp. These gains are typical, since under hood temperatures in normal conditions are relatively hot, and under racing conditional even hotter. Therefore, given the temperature differential of under hood and outside the hood along with pressurized unrestricted air flow, it is not unreasonable to expect this type of power gain at the upper levels of engine performance. "

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iTrader: (14)

sorry for the confusion, but the foam bit of my responce was talking about the camaro pace car pics, not the nascar one. I know the air box on the nascar is not foam, its probably CF

Ron U.S.M.C.

That Goodmark hood of mine came with the holes already drilled. I measured them and they ar 3/8. I was hoping Goodmark new what they were doing when making this hood.

Stephen

iTrader: (12)

Cut that area out (at least a portion of it) & make it functional, at least as a good way for heat to escape.

articwhiteZ

iTrader: (56)

well there you have it.

My procharger air cleaner. sorta sits over the left side of the eng.

was making a pan that sits on top of my super ram with snaps.
(so it can be removed. in a snap..lol) and seals the hood when closed with black 1" foam pressing on the Hood.the Pan is hookd to the air cleaner on the procharger.also sealed..

so all the air coming in.. is cool air off the cowl.

this is all out of sheet alum..and rivets. will get some photos when done.

the foam is temp.. looking at some cool looking door sweeps. that are used on larg shop Doors.
gas and oil proof as well. sorta looks like the stuf GM used.

the procharger heats it back up before it gos into the intercooler.. but it will be cooler then just taking air off the headers..

sailtexas186548

iTrader: (2)

i got the same results as the pics above, but i have a completely open cowl so the effects of the cowl are more dramatic.

the vid is uploading right now, ill post a link when its done.

MotorMouth

ronusmcmma, can you post a picture of your hood from the front and side views. I'm going to have my car repainted again and would like to see how the strips look with a hood like that.

xX89RSXx

iTrader: (1)

Like the rain.....Same thing happens in the fall when leaves are sucked into the engine bay through the cowl.

sailtexas186548

iTrader: (2)

here's the vid! the tick is a exhaust leak, collector bolts came loose!

92 Camaro

iTrader: (1)

I don't see a video.
maybe at the end of the cowl it needs to have an extension like on the 69?

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iTrader: (14)

the pics and the video show that the cowl works.