jd93rx7

I went 150 the other day without a spoiler and backed off because of fear. I heard that they can lose control over 130. Is this true? Does a spoiler help of this or a front air dam?

JspecFD

iTrader: (2)

The front lip spoiler has been proven to reduce lift at the front as well as increase drag. In contrast, the stock 93-95 rear wing has been proven useless.

twinturboteddy

Can I ask why you are doing 150.

Cetchup

Speedo says 180...lol

Roadracing7

iTrader: (2)

God help us with drivers attempting high speed runs and the idea that a plastic lip flimsily held to a flexible bumper will hold a 2800lb car to the ground, drag yes, but downforce no!
I'd be interested to see some wind tunnel test data on rear wing verus nothing or at least a program with simulations for the car. I would think it is possible that the rear wing could shape the nasty turbulence created by the rest of the car and clean it up for a little bit of drag reduction if no actual downforce was added. JspecFD, can you point me to the proof of its uselessness, I'm actually curious of this.

A good indication of how the car acts at 150 is for you to tell us, was it out of control at 130? You should be ok for road holding assuming your car is properly aligned, balanced tires, no bad pavement changes, bumps or stong wind gusts. You're pushing it, but I've driven an FD at 160 and it was stable, however far from stock... and if you need to go that fast, get in an airplane. If you run over a dog or child, destroy an FD or anything else, you're in deep $hit! Use your head.

Richard

matwey

I thought I had the proper article....Car and Driver Feb. '92 which has the RX-7 on the cover, but it wasn't the one I was looking for. But, it did state that the drag coefficient is .32, which is excellent. Also states that the top speed is 159 mph. The car is near perfectly shaped. But, what I was looking for is an old article from C & D which states that the rear spoiler does little to nothing, except enhance appearance. I do believe these cars are pretty stable.

peejay

Arguably, the drag pushes the lip down, closer to the ground, making the low pressure area under the front of the car even lower in pressure (or, if your mind works easier this way, it increases the vacuum under the car)

Hey, variable aerodynamics... the time has come Just like juggling the bushing materials around in the rear suspensions so that the rear tires toe in under certain conditions and toe out under other conditions, depending on what the desired effect is. I do believe Mazda pioneered the science and has used it on all designs since the FC.

What would be really neat would be something they tried in Can-Am days but got outlawed... attach the aerodynamic aids directly to the wheel hubs. That way suspension height, and therefore the chassis dynamics, aren't altered by downforce... it just goes directly to the contact patches without compressing the suspension first.

Ah well, can't have everything...

richjackson7

i nhave gone 180 have a witness to vouch for me and when we were doing 160-170-180 he goes so how fast ae we goin. i reply 178 he goes dam this **** is smooth and stable..... then i changed lanes and the car responded just as well if i was going 20. the rx7 rocks and is built for top speed. those who say less are just scared.

R Xplicit

there is a top speed thread here a page or 2 back, and there is little discussion of this. i owned 2 fd's. one of which is now totalled, we won't get into that. however, there are some stability issues to be addressed between the 2 fd's that i own. both were touring, the one i no longer have, a black/tan stock wheel-tire sizes.....NO WING/FRONT LIP. i ran that car close to 180mph, the car was mildly modded. i did not have an intercooler upgrade. the car felt great. not like i was looking to do some agitated steering, but i was not uncomfortable. i can say that i WAS thinking about the re-910 tires i was on at around 160. but....kept going.

the car felt planted and showed no signs of lift or front-end-flight. that is not to say there was none. i do not think that the addition of a rear wing or R1 front lip would have helped [hurt] me at all.

my other 93 touring has a rear [stock] spoiler on it, but have not attempted anything over 160 in it. the main reason for that is due to the tracking of the larger wheels and tire on this car. i do not feel comfortable attempting higher speeds now b/c of the exaggerated ruts that cause the tracking. i am sure that most of you guys with the larger wheels and tires know what i am talking about, and will agree that most of the roads around are unsuitable for this kind of driving.....

not to be too far off topic and ramble, but those are my thoughts, couples with the fact that IMO i think that the wing and front lip might add a marginal amount of [un]noticable stability, and do not do a thing for the car. top speed might be affected more by the drag coefficient by adding the rear wing....

Roadracing7

iTrader: (2)

Peejay,

I can see you know a thing or two about aero, however, I still cannot believe that the front lip is going to stabilize the car to any noticeable amount. I can see two possibilities the lip has to generate downforce, one is acting as a wing, and the other is acting as a splitter. I hope you only considered the splitter. Mainly because the R1 lip is connected to the front bumper by around 10 widely spaced bolts. If you were to push the lip down, or even pull it towards the ground, you will create gaps between the bumper and lip. As you probably know, this is not good and will create a lot of turbulence under the car which will result in whatever air is allowed under the car from it's nearest to laminar flow. Not to mention that the underside of that lip is nowhere near optimal for directing air! I hope you would agree that for any suitable amount of force to be transmitted to the front tires (yes, through suspension unfortunately), you would have to have a very solid mounting piece, and would have to have a pressure above be substantially higher than a pressure below (just talking about the lip right now) and would have to be an aerodynamic load of at least you sitting on the front bumper to have any noticeable effect on the stability of the car (we're talking about 1400lbs static load on the front, to increase normal force for tires to produce noticeably more grip, a good amount of force will be required).
Your explanation of a deforming lip to decrease the cross sectional area under the car does not lower the pressure under the car. If we were talking about Can Am or any other flat bottom or tunneled race car, this would be a very good point, but take a look under an FD and think about how much fun the air rushing under the car at the target 160mph has to look forward to. Taking your idea of less cross sectional area under the car, you would in effect have fewer air molecules being allowed under the car, thus overall lowering the pressure under the car. Theoretically, this is correct, but with this particular design of a car, there's a lot more to correct to achieve real amounts of downforce. However, like I said, the overall effect on the car's stability would also be affected by the fact that the underside of an FD is a cheese grater, air is being displaced more toward the side of the car (which is good if you have a way to keep it there), and air is getting under the car from the sides due to the very high ride height of a street FD. The 1/2" that the front lip decreases cross sectional area with the turbulent underside of an FD doubtfully will produce a difference of pressures great enough to achieve 50lbs, 100lbs, 150lbs whatever we decide will noticeably affect high speed stability.

I believe the R1 lip's primary function was to take air into the dedicated brake ducts. Most people only remember that the R1s have a tower brace, extra cooler, seats, stiffer suspension, and spoilers, but the brake ducts are usually forgotten. That's a new topic as to how well they are designed at cooling the brakes, but I will stand by my statement that the front R1 lip does not increase stability either by acting as a wing and transmitting force to the tires, or by reducing underbody pressure to effectively increase downforce.

Richard

Also, please don't explain with a vacuum under the car, that's sinful! And if I remember correctly, Formula 1's first wing developments mounted the wing directly to the wheel hubs as well, it's the most logical, but was quickly outlawed, just as the rubber side skins and vacuum cleaner for reducing underbody pressure. Imagine the forces we could achieve without "rules"! I'm sure you have seen the flexible barge boards Ferrari's F2002 has as well. Talk about variable aerodynamics! (FIA claimed that it was not the design, but the characteristic of the material, Ferrari gets away with everything, but it's progress, hehe)

ejmack1

my wingless, front and rear, FD held quite nicely at 155, went over a small hill at that speed and she was sturdy as could be, damn it felt like a roller coaster though

bajaman

I'm still searching like hell to find that article that basically said the rear wing did nothing but induce drag.....I KNOW we all talked about this a few months ago....I wonder what friggin' thread it was.......

I am no aerodynamicist, but usually, and I emphasize USUALLY, the most effective item on stock road cars is the front air dam, as it USUALLY gains the most benefit from the relatively 'slow' speeds we usually encounter. Any appreciable downforce created by a really effective rear wing would effectively rob several mph off the top speed of the car. When used right, wings and spoilers and the like can add literally TONS of downforce to a car chassis, but at the cost of speed. Look at the juggling act that CART and F1 cars do, trying to find a good balance between top speed and downforce.

mightyslash

And suspension.

R Xplicit

to add, as Roadracing7 stated, the lip on the r1 cars do help channel the air to the brake ducts, however little air that is.....But remember, when talking abut high speeds, we all know that more air is coming into the front of the car and from that we are able to conclude that this rise in pressure will lead to the front of the car being flighty. i have not experienced this first hand in my fd at speeds, but i did feel a trmendous amount of the charachteristic *loose* steering feel in my buddies ws-6 at just over 140mph. even with its girth and sheer weight, even it is not safe from the pressure build up under the hood. this is where a vented hood would help out, relieving the pressure and then assisting with the downforce on the car by eliminating the lift.......now that comes right back around to the FD, and the fact that owners are saying how stable it feels to drive at higher speeds. like i said in my post above......the only thing about my car that makes me weary about driving high speeds it the tracking effect due to the tire widtoh yeah, and the OTHER drivers on the road.....

mightyslash

Well, you made it home and posted here....So I guess it's fine

jf4828

Just my 2 cents..... I had a touring as my first 3 g and I never put a lip on the front. Anything over 140 and the car felt really light in the front. Aerodynamics of that little flimsy r1 front spoiler play a huge part in diffusing air from under the car, trust me! When I travel over 140 now in new rx w front spoiler, I feel much more stability. Doing 180 w/ out a front lip spoiler and on an open road @ that is just suicide.... Although, I don't know where you are @ in your life?? As far as the rear spoiler, I do beleive that air would barely touch the rear spoiler @ 180...... Get one of those groovy 2 foot tall aluminum spoilers then you might have df from a rear spoiler @ 180...

cash money

i found a nice straightaway on I5 the other day and i hit 150, it felt very stable, i went over a small hill and i was sticking to the ground. not like my 91 N/A FC, which felt very unstable at 130 mph.

jd93rx7

Well thanks for the input guys. I feel better about this now, but I still want the racing beat front air dam whether it helps or not because it looks cool. The car felt ok, but my brakes were squeaking noticeably louder around 140-150 and that is why I backed off. I am getting those checked this week when I get my friggin 5th gear synchro fixed. Btw, is the synchro prob just in 93's or later models too? If I do this again, I will have an alignment done. Also, another reason why I was a little scared is because there was someone else in the car!

jd93rx7

LOL good point mightyslash!

bajaman

At one-eighty you are doing about 265 ft. per second.
Keep in mind that the BEST human reflexes are going to take about 500 milliseconds to react to a situation, or in other words you will travel about 130 ft. before you even REALIZE you have a problem.

I don't have a problem with fast driving, but I question where you do this. Me, I have a 12 mile section of absolutely flat farmland where one can see for MILES around, and on this is a recently re-paved 2 lane that is literally traffic-less most of the time. THIS is where I do my speed runs. Just be careful where you choose to 'FLY' is all I am saying.

What mods are you running to do 180, by the way?

Another thing I have wondered is why there are not vents in the hood to release the underhood pressure? Jaguar noticed this in the '50s with their D type and later E type cars. The XKE has always made me think of the similarity to the FD, they have nearly the same weight and nearly the same stock horsepower. I would love to see some actual data with professional windtunnel testing. I wonder what the pressure rise under the hood is at say 150?

I have been to 150 + several times in my car, and though I don't notice appreciable 'lift' at these speeds, I do recognize a "dartiness" in the car, ANY little paving imperfection makes itself patently noticed!

Everyone just needs to be cool at triple digit speeds, as they WILL scrape you up with a spatula in the event of a wreck.......

BlackR1

good points bajaman

fastest I've ever taken it was 157... car gets really darty at those speeds... very dangerous if you have to change lanes at that speed

thatoneguy

Make sure you put your antenna down when driving at high speeds. Mine curved really bad going 180.

jimlab

Just as I'm amazed that people buy a second-hand 3rd gen. and start modifying without bothering to change the fuel filter or checking the condition of the injectors and fuel pump, I'm amazed at people who travel at high speeds when they may have no idea of the condition of their tires or suspension components.

There are two major things that can make the car "darty" at high speeds... the overly helpful power steering, and worn bushings or ball joints. Anything that allows the geometry of the steering to change at those speeds is going to be magnified, and even a small change in steering wheel position or a change in wheel alignment relative to the road will move the car substantially.

Before taking your car to speeds you can't walk away from, it would be a good idea to inspect your power plant frame (PPF) and suspension components for cracks or other damage, check all suspension and PPF fasteners for tightness and correct torque values, and ensure that your bushings and ball joints are in good condition. While you're at it, check your tires, shocks, and springs, too. If you're going to travel at speeds over 100 mph, replace anything that appears questionable. Would you bet your life on a $47 bushing or a $100 shock?

And yes, the front R1-style spoiler makes a great deal of difference in the relative stability of the car over ~130 mph. I've been to 150+ mph myself many, many times, and to 180 mph once without a rear spoiler, but with no power steering, and for all intents and purposes, a brand new suspension and tires rated for that speed.

If you're going to do it, do what you can to ensure that your equipment is sound beforehand, and only with great visibility, in straight lines, and don't change lanes or pass cars at those speeds. You may think the car feels perfectly stable, but at those speeds, it only takes something minor to upset the balance of the car, and as bajaman pointed out, you have almost no time to react to it. Keep it as safe as possible.

Hyperite

I know the 93-95 rear spoiler provides nearly zero downforce, but how about the '99? Do we have any specs on that thing?
~Tom

Mr. Stock

I would recommend not hitting the brakes unless it is necessary at very high speed. It will shift the weight to the front lightening the rear end which can cause oversteer.