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Discussion Starter · #1 ·
hey guys i know this might be stupid to ask but has any of you raced with the hood kinda open? kinda like cowl iduction? hahah well i was thinking would it work the same way? maybe if i restrict the hood from opening all the way? what do you guys think on that? ok sorry i was just bored today and was just thinking some stupid things.. haha well ima go play my new game grand theft auto 3 for my ps2 dopest game made other than devil may cry..... hmmm ok sorry for going on about games bye guys!!
 

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Seriously!

Duct your intake air from the area around the windshield wipers. When you stick a manometer there, down in the area below the removable cowl grating, you would be suprised at how much ambient PRESSURE exists at only 70MPH!
Imagine the benefits as the speeds approach 100mph! More is to be had from that big air dam of a windshield making pressure than from some pipe and cone filter hung out in front of the radiator!
I mean, not like four Land Speed Records mean anything, but, sometimes the most obvious solutions just get ignored.
Then again, with as much as I've drunk this evening, maybe you all will just toss my advice aside once again!
 

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Re: Seriously!

Ok, how is yours piped? If you haven't taken advantage of this large pressure and your own advise, how would you propose to do it in an effective and aesthetically pleasing manner.
 

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Re: Seriously!

i used to run road rallies in my 79 280zx, well once we got REALLY REALLY lost so we were doing well over 100mph for long stretches on these back country roads to make up time. soon the temp gauge was pegged. i knew about cowl induction and thought...what the ****...so i said a prayer to the safety latch gods and popped the hood. well within minutes the temp had gone back to normal. i estimate it cooled the engine temp 50-70degrees. its kind of neat. from a stop the hood stays down then as the speed increases the hood slowly rises until it hits the safety catch. this is not something i would really recommend but for a last ditch cooling effort IT WILL WORK.
 

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Overtemp VS Intake PSI Boost

Ya, been doing that for the last 22 years with summer Florida heat, what Tony led me to believe is that he was or proposes to pipeline pressurized air into the air filter(s) from the grill area behind the hood leaving the hood shut.

An immediate quick image in my mind was to invert and reverse the stock air cleaner and attach it via flex tubing to a duct fitting attached to hole in the fire wall leading to the plenum under the grill. Clearly there is air pressure there or the vents wouldn't be so strong. For that matter, those of you that do not have an AC compressor right under your filter (like mine) could use the existing heated air duct opening on the stock filter for "winter" use to the aforementioned added cowl duct modification. It would be a simple matter to switch the lever to see what if any performance gains were to be had.

Regarding quickie over temp problem fixes, in addition to popping the hood, you can always turn the heater on full blast to add a little radiative surface area and a couple quarts of cool water into the engine.

If the air doesn't come out hot, immediatly shut down because somehow you have lost a lot of water and do not have enough to cool the engine! (if there isn't enough to circulate the heater core there isn't enough to circulate the engine properly either)

So, Tony what kind of pressure did you measure and what have you done to take advantage of it?
 

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Re: Overtemp VS Intake PSI Boost

I know that norm says he has run his car with the hood half latched...says it does make a difference in 1/4 mile time...but not more than a tenth...maybe it was aonly a few hundreths, can't remember...but if you want that little extra, go for it...his car has carbs...doubt it would help on fuel injected cars...other than keeping them cooler
 

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aesthetically pleasing?

Who cares how it looks, I wan't it to work.
Several methods have been discussed in the past, and I've tried most of them.
On carbie motors, modifing a stock air cleaner assembly and attaching a duct is very professional looking.
On EFI motors, tubing can be tricky. That's all I will say.
Without an intercooler, ducting your air from this spot on a turbo car can decrease your turbo outlet temperature 100+ degrees at speed! That's not chicken scratch, and doesn't come from "cooler inlet air" but from a decrease of the turbocharger's effective pressure ratio across the compressor section. I could go and show the benefits of just 4" water colum, but I don't feel like converting to kelvin today. Suffice to say, on an early car the pressure up there can exceed 10" watercolumn at speed! That is a big pressure boost! Far better than any "ram air" system I've tested. I suppose that's why GM engineers used it...
 

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Re: Overtemp VS Intake PSI Boost

I believe Norm's reasoning was that it allowed cooler air to be inducted, not that it was a ram-air type effect.

I have been looking at designing what I hope to be an optimal set-up for my round-tops for sometime. I have been considering blocking the wiper area and using ram-air from there for a while. It is good to see someone else has actually done some testing to confirm that the improvement would be tangible. I intend on building a customer set-up based around K&N filtration. I discarded the front opening/rad grille placed setup almost immediately. Apart from cooler air, does this really buy that much? The key to the ram-air is the high pressure (higher than at the front of the car) at the base of the windshield.
 

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Re: aesthetically pleasing?

Tony,

Aesthetics are one of many considerations important to many of us. I, for one, have a nice looking car and believe performance can be obtained without looking like a frankenstein invention. Many believe in balls to the wall performance at any cost and they can have it. I admire people who are true artists in their engineering, apparently you aren't one of them, I suppose that is why you offer no drawings or pictures and feel a need to condemn those of us that include some measure of taste along with our performance. You mentioned that people ignore your advise, perhaps that is why!
 

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Nice personal attack!

n/c
 

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P.S.

Incidentally, you OBVIOUSLY missed a tongue-in-cheek comment at the opening of my followup post where I answered your questions.
 

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Ram Air-vs-Cowl Induction.

Ducting from the base of the windshield is NOT ram-air. There are distinct design differences in the way the air is pressurized, hence different names.

Ram Air utilizes a forward-facing scoop or duct that relies on air coming in at relatively high speeds, to hit a diffuser and turn to pressure. These systems are very complex to properly design. This stems from the fact that the velocities required are very high, due to the relatively small opening available, and size of the diffuser that can be fit under the hood.

With the cowl induction, though, your velocity at highway speed is enough to get the benefits of a good ram-air at 100 to 120mph!
This is due to your CAR being used as the intake, and the windshield being used as the diffuser. What happens is the same as inside the intake duct in a ram-air system, the dbig difference is that it occurs externally to the intake system, and utilizes wasted energy---any car can utilize this--unless it's fery aerodynamically slippery. A Honda Insight probably doesn't have a lot of damming effect at the base of the windshield, nor a Lambo Diablo or Countach.
Many things can be done to up the air available for the cowl induction. Strakes on the fenders helps raise the pressure, and the more upright the windshield, the more pressure you get. Small, but tall strakes at the A-Pillars keep the spill-off from occurring and are just as good as fender strakes, but hurt top speed (at speeds over 150, they can actually flatten or fold over if not properly reinforced with beading!) Fender strakes help with directional stability at higher speeds, as well as placing them on the roof.

Again, I digress. Most of the performance improvement from cracking your hood is because it lets hot underhood air OUT and lets cooler air circulate underneath. Cooling the ambient temperature of the engine operating environment is good, specifically, that the 340 air intake for the stock box will probably have 15-40 degree lower intake air temperatures from simply cracking the hood and letting the hot air OUT! I've seen high-capacity 12V pancake fans under the battery and mastervac to pump out hot underhood air in stop-and-go. Louvering the hood near the rear, even louvering the battery and washer covers helps a bit--while the car is in forward motion.!
 

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Re: Ram Air-vs-Cowl Induction.

Agreed - I know the difference, I was just clumsy with the names.
So what is it called when you use naca ducts on the hood to stream/speed the air in and pressurise it up? Could you call this ram air? It isn't really the same thing as you are drawing the air in aerodynamically rather than presenting a gaping opening at the front of the vehicle. There is a year of z's (79?) that looks like it is using naca ducts.
 

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Got up on wrong side

Tony,

Snappy answers are ususally not my style, a number of people are quick to make disparaging remarks in this forum to people who are merely trying to be helpful or or need some advise. I find that behaviour pointless and distracting. I thought your "Tongue in cheek" remark, as you explained it, was yet another and reacted badly.


Johnb510 warns against metering problems when pressurizing SUs in a newer thread on cold air induction, what are your thoughts/experiences on pressurizing stock Su's?

Regards,

RDB
 

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Author correction

It was John coffey, not johnb510, excerpt follows:

...If you're running SUs make sure you're not pressurizing or ramming the air into them. That screws up the piston metering...
 

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NACA Ducting is Ram Air.

It imparts velocity to the air, where it is introduced almost immediately to a diffuser to increase the pressure.
The NACA duct on the ZX is an interesting aminal: take a look at the routing of the air after it comes into the engine bay.
You have touched on my secret weapon against the tech inspectors if they won't let me duct cowl air to my turbo! As it was a production duct, they can't stop me from using it as I want to, rather than how the factory intended it to be used (turbo turbine housing heat removal under boost!)

The NACA Duct uses the shape to create low pressure to draw in the air to a scoop section and ingest it, rather than a scoop up into the airstream. Curiously, the opening at the end of the NACA Duct, were it presented as a scoop, up into the airstream in the identical place on the vehicle, would NOT draw in as much air as the NACA Duct does! It really is a neat piece of engineering: you get more air than a similarly sized scoop, with no drag!

Thankfully we operate with smaller displacement engines that could theoretically use NACA Ducts as intakes.
Facing rearwards, they act as exhaust vents very efficiently, but I can not use them that way in my class.
 
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