[cobalt327]

Might better to look to what NHRA/IHRA Pro Stock does, then.

I know the drag cars have rules that cover how much of an opening they can have in square inches, etc.

But I'm thinking they are compelled to hang those big-A scoops out there because of the engines deck height and intake configuration along with the body line constraints more than for any R/A effect. But that is just my opinion...

AFAIK they (NHRA/IHRA) do not dis-allow "ram air". I don't think NASCAR does, either, actually- though their rules may by default dis-allow it.

But I do not recall anything saying that non-mechanical (like turbo/super charging, etc.) positive pressure air intake to the engine is illegal, per se.

Is there a rule that specifically says "no dice" to this?

[curtis73]

Originally Posted by ap72

pressure is created at 1MPH (albeit only a slight amount), and pulling air from a high pressure area does not necessarily increase drag. And this in no way violates any laws of physics.

I'm not going to argue this any more. A few thousand tests have been done on this that prove you wrong. Any "pressure" that could possibly be created by 0-60 speeds will be tiny immesurable amounts that won't affect HP.

I defy you to use a boost gauge in that ram air intake and I promise the needle won't move. If it DOES move, that means your car is creating so much drag at that area of the car that you need all the help you can get anyway.

My argument is simply this. Let's say you have an area of high pressure at the cowl. Your two options are to either source that high pressure air from the cowl, or somehow re-engineer the aerodynamics to eliminate that high pressure area. I guarantee that the second option will generate more results than using the "ram" air from that high pressure area.

You don't seem to understand the pressure differentials that we're talking about are expressed in inches of mercury. 29.93"Hg is standard pressure. Engineers who measure pressures on different areas of the car at 100KM/H measure pressures that might peak at 30.10"Hg. That includes the grille area, the cowl, under the chin, and at the leading edges of the fenders and mirrors. That is the pressure that is created by the moving air as it moves over the vehicle surface. You can't harness any more than that.

Even the front of a cab-over semi doesn't create that much pressure. So, at best a vehicle moving at 61.7 mph can create a pressure of about 0.17"Hg of positive pressure. That translates to 0.083 psi.

Keep in mind that atmospheric pressure differences of 0.17"Hg are responsible for creating things like hurricanes, tornados, and hail and generate energy outputs in the neighborhood of 1 PW which is equivalent to 200 exajoules, or 10^15 watts. That's 1,000,000,000,000,000 watts. That's also equivalent to about the energy released if you exploded a 10-megaton nuclear explosive every 20 minutes of the hurricane's existence. So unless your car can create 1,000,000,000,000,000 watts every 20 minutes, I doubt its generating any usable pressure for intake air.

The tests have been done using MAP sensors, the math has been done a few million times by automotive engineers like myself, the proof is out there. If you want to continue believing that your car makes pressure for the intake because you put a 5" scoop behind the grille, go ahead. I'm just not going to let the OP leave this thread with such blatant misinformation.

Ram air is simply cold air that is sourced from an area of the car that people used to think provided higher pressure to the intake. Ages ago, someone put their hand out the window at 40 mph and the wind provided a lot of force against their palm and they mistook FORCE for PRESSURE. This is the same basic argument as using a leaf blower as a turbo. They generate flow, but very little pressure. Folks who aren't educated in physics very frequently mistake the two, and automotive marketers capitalized on it. Pontiac made a fortune by branding it "ram air," but in order for the ram-air cars to make more power they were equipped with better heads, a different cam, and higher compression. It wasn't the hood scoop that made it powerful, it was the engine.

Flow is NOT pressure. Force is NOT pressure. Pressure is pressure. Just because the car generates drag and has to overcome the force of wind resistance doesn't mean its making pressure. Just like a leaf blower. Just because it will blow skirts off of unsuspecting women does not mean that it makes pressure.

[Deez]

Great thread.
Since hurricane was mentioned and formally educated chaps have posted, what about those tornadoes? You know, the thing that spins like spinner wheels inside? your air cleaner before your carb. Ram air is better than that I suppose. JK. The Ford Thunderbolt used a cold air/ram air set up thru the headlamp holes IIRC strictly drag race oriented but sort of both. I thought about using a similar bumper hole setup too on a 80s olds but maybe some type of cold air pan instead, having read this I see no point other than getting fresh cool air. Somewhere mentioned IHRA/NHRA even those big engines that do use a lot of air only do so for a few seconds and maybe turn 1000 revolutions for the whole run - say (8500rpm/60sec) x ET. Even for a 7.5 ET 565ci engine that's not much air. Atmospheric pressuer is what pushes air into the cylinders, the weight of the air, not the sucking of the piston - the air fills the empty space provide by the descending piston. As for ram air with the minimal increase as described there is no 'ram' effect. o.ox is nothing to ram home about. Might find more gains through increased efficiency and maybe a tuned intake/exhaust where scavenging could help. Seems to be a lot on that too. Sorry for carrying on...

What about one of these, how do these 'work' at high altitude?

[barnym17]

Seems like a moot point, if your system or a sealed cowl system, properly sealed scoop etc. is going to gain power.Wether it be from a slight ram effect or not you will still be lowering intake air temp consideribly and that makes power.I think the figure is 1percent per 10 degree drop.So if under hood temps are say 200 degrees(seems a reasonable number) and you duct in air from outside the engine compartment at 100 degrees by the time it reaches the carb you have gained 10 percent which can be quite a bit of power.And all this means is you will get the engine much closer to putting out the power it will show on a dyno in controlled conditions.

[cobalt327]

Originally Posted by barnym17

I think the figure is 1percent per 10 degree drop.

More like 1 HP per 8-10 degrees F drop in temp, IIRC.

Cold air systems claim bigger gains but they're also changing the filter to a less restrictive design and also often have smoother and/or larger diameter tubing.

[alittle1]

Sounds like a pizzing match to me, but here goes my two cents. See this article: http://www.crankshaftcoalition.com/w...ld_air_intakes.

and then add this: water and methanol injection. Think about the last time you had a needle and you blew on the alcohol that was swabbed on your arm.

Comments!!

[curtis73]

Originally Posted by Deez

Great thread.
Since hurricane was mentioned and formally educated chaps have posted, what about those tornadoes?

OEMs go to great lengths to laminate airflow. They use honeycomb screens in the intake to reduce that spinning. For the most part, those tornados are absolute snake oil.

If anything, the spinning air would simulate a longer intake runner with less flow. That net result would be that the engine might make more off-idle torque, but at the risk of a loss of HP.

Snake oil. Waste of money.

[Torque454]

Ram air definitely. I'm sure the ram air would work for boosting power slightly if you could add extra fuel too (air is nothing without fuel) but the main thing would be the REAL cold air. A cold air intake kit is a waste of money IMO unless it actually draws air from somewhere other than under the hood. Unfortunately as mentioned already most "cold air" kits draw in underhood air or just barely stick out of the fender or core support where it still has access to nice HOT underhood air. One big fat friggin SCAM IMO.

[barnym17]

Are you sure the Holley book I have by Doug roe says percent not an absolute number.This supposedly comes from Holley engineering.

[Jake_Dragon]

Is this Ram air or Cold air?



Can you lay your hands on your throttle body and not get burned after the engine is at 195 degrees?

[curtis73]

Originally Posted by Jake_Dragon

Is this Ram air or Cold air?

Neither. Until that air gets chewed up by that blower, its probably 250 degrees, and the front of that scoop isn't in a high pressure area.

[ap72]

Originally Posted by cobalt327

More like 1 HP per 8-10 degrees F drop in temp, IIRC.

Cold air systems claim bigger gains but they're also changing the filter to a less restrictive design and also often have smoother and/or larger diameter tubing.

1 percent for 10 degrees is probably a hair low, but a good ROT.

[xxllmm4]

Interesting article from Autospeed

http://autospeed.com/A_110824/cms/article.html
http://autospeed.com/cms/A_1023/article.html
http://www.autospeed.com/cms/A_0629/article.html

some of these are multi part articles, good reading

Jordon

[curtis73]

That first article records 2 inches of water at the bumper... which equates to 0.072 psi. Then they also recorded that it reduced the vacuum at the airbox by 4 inches of water (0.144 psi).

Then they say, "you can find gains with this approach. We’ve proven it!"



I'll keep my cold air and give up that .072 psi

[ap72]

interesting articles, basically by putting a ram air intake at the bottom of the front bumper you can expect about a 1% increase in power from the pressure alone, accompany that with the lower air temps and a better designed ram air system and 5% is not unbelievable. That's only 20hp for a typical 400hp sbc though, about the same you'd get as a manifold swap in a lot of cases. It also did not discuss fuel metering, with FI its much simpler, but with a carb it can be a bit tricky, especially for a car that sees both highway and city driving.