retated on areodynamics. can I make lemonade out of lemons

[Guest pvtkary]

ok guys I have gotten on my soap box about astetics, so enough said. Ifn I want to do some top end, and spoilers are the only answer then please help me find the flaw in my thinking. If I must induce an area of low pressure under the car to keep it on the road, then y cant i use this air to feed the engine instead of just pushing it out of the way. I havent done the math yet, but, If I must use some horsepower to move the air out from the underneath of the car, y cant i use it as an air ram. If I scoop the air up, and force in into the induction system the same low pressure should be created under the car? and presto i dont catch air at 1??MPH ????????. Am I retarted on aerodynamics???, or is this pheasable.

[Guest Anonymous]

Do not forget the stiffer suspension modifications to hold the front end down and check out photos of the early racing Zees to see what type of front spoilers they were using. MSA offers a rather simple unobtrusive (if you want aestetics) looking spoiler with or without ducts based from an early racing team. The BRE "spook" #50-1521 or 22. Also there is a matching BRE deck lid spoiler. The BRE front spoliler is designed to limit air flowing under the car but also to use the air to force downward pressure to keep the frontend focused to the road.You can make all this complicated beyond my understanding but keep in mind this BRE team was winning races with stiff suspensions and simple spoilers in the early years with speeds in excess of 100mph.

[Pop N Wood]

I would think you would have to move too much air to be practical. I don't think 750 CFM of engine suck is going to create much of a vacuum under a moving car.

 

I know at one point either Indy or F1 cars were using oversized "radiator fans" in the rear of the car to improve downforce. But the teams modified the set ups based on the tracks because the fans stole enough engine power (or was it increased drag?) to reduce the straight away speed by several MPH. They only geared in the fans on road courses with lots of turns. Either way it took some serious HP to draw the something like half inch of vacuum under the car.

 

The sanctioning bodies eventually outlawed the fans for safety reaons. They didn't want to risk mechanical failure and have the car suddenly lose half a G of cornering ability in the middle of a turn.

 

I do rember the original 300 ZX (I thnk) ads claiming the car wheels (or is rims more techinically accurate) were designed to blow air outward, drawing a vacuum under the car to improve downforce.

[Dan Baldwin]

I can't decide if you're more "retarted" on aerodynamics or spelling

But cirrusly, we're talking about HUGELY different volumes of air here. The air feeding the engine would be a small fraction of the air you'd like to divert from the underside of the car.

 

As far as hp required to divert the air, you should be able to FREE UP some hp by reducing lift. Reducing lift reduces induced drag, so (big generalization here) minimizing lift should minimize drag. The BRE-style spook, painted satin black, is your best bet. But hey, why not find out if you NEED anything first? Just lowering the car should go a long way to reducing lift.

 

FYI:

aestetics => aesthetics

retarted => retarded

pheasable => feasible

[Guest pvtkary]

thank for the help guys. I kinda figured that the air required by the motor was less than the air i need to remove from under the car. that is why i want to build an air ram, inplaceof a spoiler. This would greatly increase the performance of the motor ie posative manifold pressue. If i must move the air why not do something useful with it.

[RPMS]

I remember the cars that Jim is talking about. I think they ran Indy... Anyway, the reason they didn't last wasn't because of the threat of mechanical breakdown in the middle of a turn. If I remember correctly, they had a nasty habit of Hoovering up any foreign material on the track and spitting it out the rear-facing fans at ridiculously high speeds. Can you imagine trying to draft on a car like that with pebbles and stuff rocketing towards you at a closing velocity of 400 mph??

 

I remember that the "sucker cars" could run insane amounts of lateral G. Neat idea, if it had worked out.

 

Scott "Nothing sux like Electrolux" Ferguson

[Guest Anonymous]

I think we spoke about this before and its in the archives (what isn't if you only know what key word to use? ), at any rate. If you go back in time to the Can American series (CanAm cars circa mid to late sixties) you'd find that the Chapparal of Jim Hall advanced that idea years ago. He first started with a adjustable wing he could actually move depending on throttle setting. He moved the idea forward with ground effect skirting and the back wheels were totally covered with giant fans in the back to suck the car to the track. I believe for the reasons stated, or just because it was to innovative for the time, or a un-fair advantage for the season, or perhaps it was just the end of the CanAm era, but it all came to a halt. Slick car too, mid-engined 427 chevy with hilborn injectors, made ton's of HP and weighed very little, looked very much like a GTP car without the top on it. It also was innovative in that he used an automatic tranny. Perhaps the idea just sucked.. haha, sorry couldn't resist.

 

Regards,

 

Lone

[A. G. Olphart]

Damn Lone, you must be near as old as me to remember twin white fans on the butt of a low white car (going rapidly elsewhere).

 

Weren't those things spun by lawnmower engines or such?

[Guest pvtkary]

thanks guys

you have reinforced some things that i thought i knew, or had a strong supission about. i have looked into race car design, scirts, spoioers, wings n such. im not trying to create a perfect vaccume under the car. I kinda thought that the body with stock ride height would not mutch care for top end. i was wondering what the limitations of the stock looking configuration was, and how much i needed to modify it to look at like 140-160 range. i suspected that some modifications would be necessary. if a small chin spoiler will do then the area of this spoiler should make a nice air ram. no one has touched on this idea here. has anyone experimented with air rams. perhhaps im using the wrong word here. you know like a ram jet works.

[silicone boy]

I recall watching the legendary Elliot Forbes Robinson racing in the Chimney Rock Hillclimb outside of Ashwille, NC in a custom built sucker car. Here's a guy who doesn't need any help with driving who uses a leaf blower motor to create suction that results in phenomenal stick to the road. I'll bet it takes some of the challenge out of cornering till your ears bleed.

[Datsun660z]

Pvtkary, you have got the right idea, I have a Volkswagen Scirocco with an AIRDAM that has RAMAIR built into it from the manufacture of the AIRDAM. It even came with the plumbing that goes to the air box. It made a HUGE difference in performance starting at about 40 miles per hour. I hope this affirms your thinking.

 

 

Jon Peterson

[Mikelly]

Getting a Zcar stable between 140-160MPH is VERY easy to do. I've been doing research on getting a Zcar Stable Past 200mph, and IF you are willing to follow a few suggestions, then you CAN do what you are trying to do without too much external body modifications.

 

Search the archives, as we have covered much of this many times, or contact me off line and I'll give you the benefit of what I have learned. I've had several Zcars up to the 160s, with one pass being officially clocked (By a state trooper with a Stalker unit) at 168mph. My car was ROCK Solid, but did have a large WING on the back (Porsche Style) and an MSA Airdam up front.

 

Mike Kelly

[Lone Star 1]

I know what your saying, and think that you could make a two or three inch deep by three foot wide scoop that would trap air and funnel it to the motor with some type of filter built in. It could be placed under the raditor and not be very noticable. You would pick up a little hp at speed and in afect create an air damn. Not a bad idea, and keeps the stock look.

[DavyZ]

One of those looon threads was entitled "Belly pans for aerodynamics" or something close to that. I wanted to know about it and boy, did I ever get an education after I started that thread!

 

Davy

[Dan Baldwin]

There is power to be gained from ram-air, but you have to address the fuel-delivery side as well or you'll run lean the faster you go, especially if you're carbureted. Maximum ram-air pressure is equal to 1/2 rho V^2. Using standard SL density of 1.378E-6 slugs/in^3, I get .34 psi at 40 mph, 1.37 psi at 80 mph, and 3.07 psi at 120 mph. So that'd be about +2.3%, 9.3%, and 20.9%(!) more power, respectively. IF you could get full stagnation pressure, which would likely require a scoop protruding from the nose of the car. Damn, those numbers seem too large to be ignored! Somebody correct me if I'm wrong.

[blueovalz]

Sounds high to me too. I've got a homemade ram air set up on my 240SX (completely enclosed box with slightly protruding scoop on front of bumper) that provides an estimated 3-5% gain at highway passing speeds. The only comparison I have to give is that the car accelerates almost as quickly in 5th gear as it used to in 4th gear at the same highway (70+ mph) speeds.

[Guest bluex_v1]

Please excuse me if this is a stupid question, but if your air intake is in the air dam and just a few inches above the road surface, wouldn't you suffer on hot sunny days from the heat of the asphalt warming the air right above it?

..maybe just not as significantly negative as the ram air effect is positive I guess...

[jhaag]

If you want to read more than you ever thought possible , check out the following books. When my note says 'very technical' it means that the book uses numerous formulas (beyond my skills) to illustrate its points. The titles of several refer to chassis design but cover the importance of aerodynamics on chassis design. I think the first several books are the easiest for the lay person (like me) to read. I've gotten all of them via utilizing the free interlibrary loan service at my friendly local public library.

 

-Competition Car Downforce: A Practical Guide - Simon McBeath.

 

-Competition Car Controls - Alan Staniforth.

 

-Aerodynamics for Racing and Performance Cars - Forbes Aird

 

-Competition Car Suspension – Alan Staniforth. Very technical

 

-Aerodynamics of Race Vehicles – Wolf Heinrich Hucho. Very technical

 

-New Directions in Race Car Aerodynamics – Joseph Katz. Very technical.

 

-Race Car Vehicle Dynamics – William Milliken. Very technical

 

-Inside Racing Technology – Paul Haney. Very technical

 

--Grand Prix Car Design and Technology in the 1980s – Alan Henry. Dated but it describes the movable panels, brushes, underbody ducts and fans used to create downforce.

 

I believe the Chaparral used a snowmobile engine to create the suction for its 'sucker' car.

 

There are several British magazines that cover racing technology, including aerodynamics, in some detail. Race Car Engineering is one.

 

Some time back a person on this site posted this web link (http://www.gmecca.com/byorc/designpublicationsbooks.html ) and I ordered all of them via interlibrary loan.

 

John