Mr. Stock

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?

2-Rotor

I would think that as **** 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.

martini

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)

jimlab

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.

SPOautos

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

STEPHEN

Mr. Stock

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

jimlab

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.

Mr. Stock

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

Ed

Mr. Stock

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.

GoRacer

iTrader: (2)

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).

TriTurboGen3 RX-7

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 ?

Mr. Eccentric

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.

Roadracing7

iTrader: (2)

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

DRAG0NEER

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

jimlab

I think you need your eyes checked.

DRAG0NEER

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...

jimlab

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...

badass7

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 ??

Mr. Stock

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.

GoRacer

iTrader: (2)

'99 JSpec wing -VS- any GT Wing?

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

Leprechaun

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...

JspecFD

iTrader: (2)

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 )

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.

jd93rx7

What exactly do these numbers mean?

jd93rx7

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

maxcooper

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