Is there a danger of speeding w/out a spoiler?
 

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?

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.

Can I ask why you are doing 150.

Speedo says 180...lol

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

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. :)

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...

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 shit 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.

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....

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)

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 :D

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.

And suspension.

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.....

Re: Is there a danger of speeding w/out a spoiler?
 

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

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...

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.

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!

Re: Re: Is there a danger of speeding w/out a spoiler?
 

LOL good point mightyslash!

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.......:(

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

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

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.

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

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.

How do you know this?

Apparently, there was some vague evidence that the there was zero downforce on the rear on a R1. Is that NET zero downforce?

If the R1 front spoiler adds downforce to the front, it may unload the rear. If there is NET zero downforce on the rear of a R1, doesn't that mean that there is downforce being added by the R1 rear spoiler.

As I stated before, I want scientific proof that the R1 rear wing adds no downforce by itself(i.e. without a front spoiler).

WHO HAS THIS PROOF THAT THE R1 REAR WING ADDS NO DOWNFORCE?

I would think that as anal the engineers were at Mazda for weight savings they wouldnt just put a wing on to make the car look better for no added benefit. I would also like to see proof that the rear wing provides no downforce.

Actually, the R1/R2 front lip does quite a bit to add downforce. Let me find some numbers.


------------------------------Baseline RX7------RX7 - R-2
Drag Coefficient----------0.29-----------------0.31
Lift Coefficient, front-----0.16-----------------0.10
Lift coefficient, rear------0.08-----------------0.08

You'll also notice that the rear wing does next to nothing for downforce (I can't say it does ABSOLUTELY nothing, because these numbers are only taken to the nearest hundreth, and because the rear wing wasn't tested seperately from the front lip)

An Australian racing team performed analysis and found the following...

RX-7 base model (no spoilers)
drag coefficient (Cd) - 0.29
lift coefficient, front (Clf) - 0.16
lift coefficient, rear (Clf) - 0.08

RX-7 R-model (front and rear spoilers)
drag coefficient (Cd) - 0.31
lift coefficient, front (Clf) - 0.10
lift coefficient, rear (Clf) - 0.08

Unfortunately, no analysis was done on a car with only the R1 front spoiler, so the data is therefore incomplete. Here's what they had to say...

'We tested the rear spoiler in three different guises out here (Eastern Creek),' informed Garry Waldon: no spoiler at all, the factory spoiler and the high mount version - which won favour. 'The small standard spoiler proved it was faster around Eastern Creek than no spoiler at all but the high-mount was around six-to-seven-tenths quicker again.' The notorious Turn One sweeper is where the rear spoiler benefits most, raising the car's corner speed 5km/h 'You can really feel the increased downforce around here,' added Waldon who hustled through the sweeper during the race consistently over 200 km/h.

Every source (except the above) that I've read over the years has said that the original R-model rear spoiler was merely decorative, and did not provide an real measureable downforce. (The '99 rear spoiler, with its adjustable center section, does of course)

However, the above quote seems to indicate that the early R-model rear spoiler does indeed provide measurable downforce and that the lack of change in the coefficient of lift at the rear of the car is the rear spoiler acting in complement with the front. One might conclude that if they had done testing with an R-model front spoiler and no rear that the coefficient of lift at the rear might have increased, but we'll never know unless someone wants to pay for wind tunnel analysis of that combination. :)

It would be interesting to see this kind of data for a few nice aftermarket spoilers or the 99 spec spoiler.

STEPHEN

Jimlab,
We had this discussion in a different thread on this forum.

I pointed out the fact that if the rear lift coefficient does not change in the R1 set up, the rear wing probably is adding downforce to the rear IF one believes that the front spoiler induces lift at the rear.

So I don't think there is any scientific evidence that the R1 rear wing does not add downforce at the rear.

Ed

PS I know my rear wing adds downforce since I have switched to the 99 wing:D

How is that in contradiction to what I posted? Looks like we are saying the same thing... :)

"However, the above quote seems to indicate that the early R-model rear spoiler does indeed provide measurable downforce and that the lack of change in the coefficient of lift at the rear of the car is the rear spoiler acting in complement with the front. One might conclude that if they had done testing with an R-model front spoiler and no rear that the coefficient of lift at the rear might have increased, but we'll never know unless someone wants to pay for wind tunnel analysis of that combination."

Agreed. I believe that those who have seen the identical coefficient of lift numbers for the rear of the car have interpreted them to mean that the rear spoiler does not provide additional downforce, when I believe that it is more likely that the net change is zero precisely because the rear spoiler is adding downforce.

Jimlab,

Actually, I did not say that it was in contradiction to what you posted.

I was merely pointing out that we had already had this same discussion before where someone(I think it was you Jimlab) stated that there was no downforce applied by the R1 rear wing quoting the same lift coefficents and I disagreed stating my interpretation of those numbers.

I am glad that you see it my way :p:

Ed

I found that thread in which we had a discussion about the merits of the R1 rear wing.

https://www.rx7club.com/forum/showth...ft+coefficient

Anyway, I maintain that an effective front spoiler will induce lift at the rear. And this is an important assumption if we are to believe that the R1 rear wing is effective in decreasing lift at the rear.

The last poster of the above thread believes that the front spoiler does not induce lift at the rear.

I tend to believe otherwise and I fear for all the Touring drivers on a top speed run with a front spoiler only. :eek:

Interesting thread
 

I read somewhere that the tall GT aluminum style rear wing is good for stability up to 160mph. So it seems to me that the higher up, the more downforce which kinda sucks for me cause I really want the Hammer Shark Wing (covers up the R2 wing holes like RB wing):(

Does anyone know what affect the new curvy type GT wing (by CWest)has on down force? ...or why the curvy shape?

Oh btw: To whomever wanted the RB font spoiler ad on. You can get a replica from Wings West (I think RB made it to replica the Feed Type I front air damn.)or you can get a lower 1/2 spoiler by RMagic (I beleive).

And sometimes you just have to go that fast and upwards of 180, if modded, i mean when those damn porkers are on your tail, you can't let them stay there.......Yea i'm crazy. So what about aftermarket wings, how do they effect downforce and aerodynamics ?

What's wrong with the word vacuum as a description? This is plainly the idea behind both the Can Am and quickly banned F1 car. A vacuum is a device that imparts suction, just as those fans and skirts in tandem simply 'sucked' the cars to the ground.

No spoiler on the FD isn't really cause for concern. As one person pointed out, they're mostly cosmetic in 99% of road cars. What is dangerous though is a loose spoiler at speed. Make sure your rear wing is secure before hand. Otherwise the wing will 'catch' air and create lift, the back end will swing out unprovoked.

And, downforce creates drag. Ie. to increase top speed, decrease wing angle. The tradeoff here is decreased stability obviously.

Bottom line is that no road car is designed to go 180mph safely. Less maybe the Porsche GT1 or McLaren.

When the server was down last night, I lost over 2 pages written in Word when I did not save the file and the post didn't go through. DAMN IT!!! I'm not gonna write it all again, so I'll just read posts and bite my lip.

Mr. Eccentric- Vacuum by definition is "a space with nothing at all in it; completely empty space or a space left empty by the removal or absence of something usually found in it; void..." I must refute your claim that vacuum is acceptable when talking about the underside of a car at ANY speed. It sounds like your "suction" definition is with the idea behind a vacuum cleaner. The actual physics behind it involve differences in pressures on opposites side of a fan (simplified, however pressures exist). It does not mean that you totally remove all the air on one side as the two sides exist in the same atmosphere. The Can Am cars used the same idea of a vacuum cleaner while trying to remove as much air as possible from under the car by attempting to create a closed system and thus being more efficient. It is not a true vacuum, but very close to it, so the pressure exerted by the air on the top of the car has a greater effect on the car because the air underneath isn't putting up much of a fight... But the fans did not pull the car to the ground, they just made it easier for the air over the car to push it down.

I agree that the wings are mostly cosmetic, but the numbers don't lie and I will accept the fact that there is a difference, but is the difference as noticable as many claim?

Downforce created by wings and any turbulence create aerodynamic drag. Underbody aerodynamics such as our Can Am and F1 "vacuum" :) cars do not increase aerodynamic drag. They do in fact create drag because the downforce creates a higher normal force on the tires and creates higher rolling frictional drag between the tire and the road, however, it's not aerodynamic.

As I stated before though, if you want to increase speed, trim the car out so you can keep your power down, and to keep the front wheels touching, anything else is hurting you.

180mph safely is not only particular to car, but also to driver. 911 GT1 and McLaren owners are few in number, but those "safe" at 180 are nearly non-existent.

Richard

i think the stock spoiler works if racing beat put this spoiler on their record setting FD...242mph!!! :D

http://www.racingbeat.com/Gallery/95%20Boneville.jpg

I think you need your eyes checked. :)

i think not...

I didn't say they were the same spoiler did I?

I'm sorry if you don't see the similarities between the two...

Maybe you should take another look at a stock R-model rear spoiler. It looks nothing like the NASCAR-style lip on the back of the RB Bonneville car, and the nose on that car is a completely modified one-piece unit, as well as the additional fins on the roof, and side moldings. As far as spoilers go, there's nothing on that car that bears any resemblance to the stock R-model spoilers.

I fail to see how the RB Bonneville car has anything to do with the effectiveness (or not) of the R-model rear spoiler, unless you were just trying to be funny...

What about the downforce of the '96-'98/ Efini Style rear wing vs. the R-model rear wings vs. '99 rear wing ?? The '96-'98 seems to sit up a bit higher than the R model wings or am I wrong ?? Here are some pics of the '96-'98/Type RS/Efini rear wing. Anyone ??

https://www.rx7club.com/forum/attach...&postid=825279

https://www.rx7club.com/forum/attach...&postid=825282

https://www.rx7club.com/forum/attach...&postid=825296

https://www.rx7club.com/forum/attach...&postid=825284

There is a video on the net somewhere of that car taking flight during a top speed run.

The nose started to climb up just like a plane taking off and then it flipped over like the MB during the LeMans Race a couple of years back.

I guess the rear wing was making too much downforce causing lift at the front.:D :D :D

What about these?
 

'99 JSpec wing -VS- any GT Wing?

...or better yet
CWest Carbon Fiber GT (strait)Wing
-VS-
CWest Carbon Fiber GT-2 (wavy) Wing?

Mr. Stock, I was thinking of that video while reading this whole thread... hehe

I uploaded it for those who haven't seen it.

http://www.ggowned.com/215mph.avi

The only thing we really learn is that going 215mph with rear spoiler and without front spoiler is not a good idear... ;)

I don't especially considering all the RX-7's Mazda sold with the front lip and no rear wing as standard fare(referencing Series VII 96-98 models). The real fear out there is for the Ricers and the mondo wings they put on their cars(some of which are on upside down :eek: )

There's a professional aerodynamics expert on the big RX-7 list by the name of Stephen Lee. He stated that the rear wing is essentially useless and provides no real downforce. While the anecdotal evidence and layman theories are interesting and fun to talk about, they don't really answer anything. For those who are truly interested, it may be worthwhile to search the list archives for S. Lee and ask him since his background seems to exceed those of everyone on the forum.

What exactly do these numbers mean?

That was the video that scared me and caused me to back off. Could that actually happen under 200 mph??

It means there is lift at both ends, rather than downforce. The bespoilered version has less lift in front, so should be more stable at speed.

A lot of us have also modified our ride height, so the height and rake of the car might also lead to different aerodynamic conditions.

-Max