Highest Speed with Stock Aerodynamics
 

What is the highest speed for an FD with the stock aerodynamics (front and rear spoiler)?

i forgot the page that shows the CD and CLR of stock aero, but u will not be flyin till 170 i guess. dunno much on this subject :)

A friend of mine did 170 indicated twice on his way back from Vegas. This was WITH a passenger in the car. He said he could have gone a little faster.

done 155 around a large sweeping turn with passenger. speed was still climbing and felt rock solid to the pavement. tires are old so i let off

An FD is faster without the stock rear wing. The rear wing adds more drag than actual downforce.

My car started to lift (the steering got lighter) at 145. I'm in a base model and my bushings are going out all around.

I got 150 and let off becuse it started to feel real light. I have no spoiler. She still felt like she had alot left in her.

so would an aftermarket body kit increase your aerodynamics? the feed or stock 99 kit i would think would increase it, but some of the kits like the veilside.... they may be a bit too much.
also lowering the car should help too.
if you plan on going over 160mph, make sure you have "Z" rated tires, or may not live to tell what your max speed was.

quickfini, what type of wing adds downforce instead of drag? does the stock wing cause downforce at lower speeds? it looks like you have the 99spec spolier in your pic, how is it operational wise?

Racing Beat's car went airborn at over 215mph on the saltflats. Other than being extremely lowered and having aerodynamic wheel covers, it had a virtually stock body (including the R1 wing).

i wnet 265km/h in my car didnt' feal liek btu i was scared my tires would blow. dotn think any body stuff helped i thougth the gay wign ont aht back that came with my car was goin to rip off but it held on for life.
joel

150 car full of luggage. I stopped accelerating due to the self-preservation instinct not a lack of power.

Some of you guys are hilarious. If you think that an aftermarket body kit designed solely for looks improves the aerodynamics of a car that Mazda spent hundreds of hours in a wind tunnel on, you need help.....

BTW, I've heard from more than one source that the Veilside kit damn near shakes itself off the car at speeds above 120 mph due to the terrible aerodynamics of the kit....

what about the 99 spec?

I agree.

I just wanted to add that the car was still pulling pretty hard when I let off. The rear end certainly made some strange noises when I let off though...

lol so true i think the kit that was on my car when i bougth it was going to all off the front and the wing. if it did woudl ahve more of a reason to spend more moeny ont he car. oh well veilsid will be gone soon. and then my project finaly starts:d
joel

Don't even try. I've been preaching it for years and they just won't listen.

body kits migth have a better flowing bummber but i still think mazda has the aero dynamics down unless a kit was tested and stuff. so othere then flow and looks thats all i think they are for:d
joel

I read a post or an article somewhere that said the one of the things that would help an FD would be some type of diffuser system that ran the length of the car, similar to the Enzo Ferrari. If you look at "back in black" Racing Beat's second Gen 3 that went 242, the rear spoiler was SIGNIFICANTLY larger, almost like the porsche duck tail design. Even then, big Jim almost lost it as the rear end got light. Only the parachute opening kept him from losing it again!

topped my out a few weeks back in ideal weather conditions and hit 172 which was way too fast for me kinda scary and thats with a passenger

Gotta remember about that Bonneville run, that ground is not solid. The power to the ground required to hit those speeds most definately has to keep the powered wheels spinning faster than you are moving. Let off throttle and they slide. I bet that is what happened on the second run as opposed to it being an aerodynamic issue.

Okay first of all, the speedometer gets more and more optimistic the faster you go. So while the dash says one thing, you're going a good bit slower. That is of course unless you are running tires with a diameter that is hugely smaller than stock.
You can't "increase" aerodynamics. There are basically three aerodynamic forces that act on a car in motion: lift, downforce, and drag. Lift sucks the car up off the pavement, downforce pushes it down, and drag pulls it backwards. You can also have negative lift where the car actually sucks itself down to the pavement, this is not the same thing as downforce. Generally it is impossible to change the way a car responds to or creates one of these forces without also changing its response/creation of the others. For example if you set up a wing to create more downforce, that also creates more drag.

If you're looking to actually improve the aerodynamics of the car the source to go is Mazdaspeed. They're pretty much the only aftermarket company that has the resources to test their kits in wind tunnels. Some of the companies that make body parts for circuit racing are also probably designed with aerodynamics in mind such as RE-Amemiya, FEED and Pan Speed. But aside from this stuff most of the kits otu there are just for style and probably do more harm than good to how the car moves through the air.

what does the car do stock ? HOW FAST? mph wise

Maybe with an older cable driven speedometer, but I took my car up to 180 mph indicated on the dyno and it was off by 2 mph (178 mph measured).

Electronic speedometers are fairly accurate when calibrated properly. Inaccuracy can creep in with the comparator circuit's conversion to output usable by an analog needle indicator, but it's still much more accurate than the cable driven speedometers.

i did 120 on a slight up hill/offcamber turn and it started to get floaty, then again... slight up hill/offcamber turn haha

You're comparing two things that are both essentially measuring how fast the wheels are spinning. Of course they'll be similar. What I mean is that even if the mechanism or circuit or whatever controls the speedometer is in perfect working order, they tend to be optimistic about the actual vehicle's speed while in motion.

The problem is that the only way to figure out how far off any particular car's speedometer is from actual is to use testing equipment that measures something other than the rotation of the wheels and most of us don't have radar guns or GPS test boxes. At least I know I don't.

How do you think law enforcement vehicle speedometers are calibrated?

Go to any shop offering speedometer calibration and certification and you'll find a set of rollers involved. Not radar. Not GPS.

this might be a stupid question but what about hoodpins? when i did 165 in my car, the hood unlocked and started to shake. i have fixed the latch and now have installed hood pins for extra protection. will those make a difference that you can notice?

I could be wrong here but I do not believe that law enforcement vehicle speedometer readings are admissable as evidence in a court of law--only speed gun readings are.

Honestly I have no way of knowing whether or not the FD's speedo is indeed accurate at high speeds or not. It has been my observation however that when in-car speedometer readings are compared with those from external testing equipment, the speedometers *generally* are on the optimistic side even if properly calibrated for lower speeds.

Yes, they are, and law enforcement vehicles used for traffic patrol are required to be certified on a yearly basis. The certification card may be presented as evidence of the vehicle's speedometer accuracy in court, then returned to the records department afterward. That is why "pacing" is a legal method of ascertaining another vehicle's speed.

Well, in my experience it's fairly accurate, even in the upper extremes.

The comparator circuit which receives AC pulses from the VSS (vehicle speed sensor) located in the vehicle's transmission is responsible for converting those pulses to an analog output so we can watch a needle move on the gauge face.

Any time you convert from digital to analog, there's a chance for error. For example, the analog speedometer in my Z06 was sometimes in disagreement (only by 1 mph or so) with the HUD's digital speed readout on the windshield.

The quality or calibration of the comparator circuit on some cars may be the problem, especially since there's no regulation of how accurate the speedometer needs to be beyond 60 mph or so, and there's an acceptable margin of error even at those speeds.

Getting back to the topic...

My car has an R1 front spoiler, no rear spoiler, and was lowered about 1.5". At 150-160 mph, it felt rock solid, which is not to say that a bad dip in the road wouldn't toss you into orbit. These aren't F1 cars we're talking about. They can't travel inverted at speeds over 120 mph because of the amount of downforce generated by their spoilers. :)

Mazda knew the top speed of the cars was 158-160 mph in stock form, and I suspect they were designed to be very stable up to and including those speeds. Beyond 160 mph, however, all bets are off in my opinion. You're out of the operating range set by the manufacturer, and on your own.

Although the FD was wind tunnel tested extensively during the design phase, I've never heard or read any evidence supporting the belief that Mazda wind tunnel tested the cars to anything above the stock attainable speeds. The C5 Corvette was wind tunnel tested and designed to be stable at 200+ mph, which is where the "billboard" rear end came from (it was a functional choice, not a design choice), but I've never found any information of this kind for the 3rd gen. RX-7. If anyone knows different, I'd like to hear it.

That said, although I've been to 150-160 mph many, many times, I have been to an indicated 180 mph once and only once, and I know there are others who have done it also. I was on a ~5 mile straight stretch of road, the car was fully modified with stock twins in non-sequential configuration at the time, and it still took awhile (relatively speaking) to climb that last 10 mph or so. The car still felt "OK", but not nearly as stable as at 150 mph. I won't do that again, nor would I recommend anyone else try it.

Personally, I'd recommend people with stock aero combinations (stock front and/or rear spoilers, '99-spec front bumper, etc.) stay under 165 mph if you value your skin. If you have a body kit, I would not assume that it had any sort of testing whatsoever, and it'd be a pretty shitty way to find out by having something going wrong on a top speed run because the body kit you bought was designed for the car show circuit, not for 100+ mph speeds, if you know what I mean. :)

I think stock aerodynamics with front/rear diffuser and full flat underbody tray with 1 or 2 strakes would be highly beneficial.

Base model front lip and no rear wing: I've seen 170 mph and there was maybe one or two mph left. Quite a bit of lift on the front end at that speed; I wouldn't have tried go around any curves. Any downforce at the rear at all would be bad in this case (assuming the R1 wing actually makes downforce) as it would pitch the car even more nose high and make the front float even more. In my car the front end really lightens up at 150+.

Haven't tried it with my front splitter in place though. Fastest I have run the splitter at the track is about 115 but since the corners aren't near that speed I can't say if it helps reduce front lift at all. I wouldn't expect it to though.

That doesn't mean a hill of beans if you're on rollers. All you need to know is the exact circumference of the roller and at what rpm that roller is spinning. From that you can get a velocity (ground speed) which you can compare to what the speedometer in the car indicates. In actuality this is the most accurate measure of speed possible; not GPS or radar guns.

Actually, if you sacrifice ground clearance, I'm sure it's easy to improve on the amount of lift on a stock front end. Also, aren't most of those kits modeled after race cars ? I would think that if they are solid, and solidly mounted, they should be fine.

I'm pretty sure that the Mazdaspeed bodykits are windtunnel tested. As well as (obvisouly) the R1 spoilers. And I would imagine that the '99 spec body parts are tested as well.

Correct. I'm not talking about MS or 99-spec stuff, which actually is an ENGINEERED product.

That was meant as a joke right? If not, you obviously have no understanding of aerodynamics and are giving C-west, Veilside, Ings, etc, far too much credit.

Egads...simply "modeling" (read: styling) a piece of bodywork "after a race car", and actually replicating an engineered product are two different things entirely...

I don't think you understand aerodynamics. You don't need wind tunnels, although I'm sure they help. Pretty much anything that blocks air from flowing under the car will be good for aerodynamics (reduced drag and less lift). This is why "air dams" work. Its actually better to block the air than to let it flow under the car.

When you're talking about something as simplistic as an air dam, sure, but even then, at the elevated speeds that this thread is referring to, simply throwing any old "lip" to block the air can create just as many problems as it might solve.

There are countless instances where race teams have been chasing an instability problem, and found that the slightest modification to the bodywork paid major dividends in stability and aerodynamic efficiency, air dams included.

[QUOTE]Originally posted by Kento
When you're talking about something as simplistic as an air dam, sure, but even then, at the elevated speeds that this thread is referring to, simply throwing any old "lip" to block the air can create just as many problems as it might solve.

There are countless instances where race teams have been chasing an instability problem, and found that the slightest modification to the bodywork paid major dividends in stability and aerodynamic efficiency, air dams included. [/QUOTE}

Actually I don't think you will create problems by limiting lift, which is what is dangerous at speed. Maybe if it broke and you suddenly had more lift. More to the point, I don't think driving your fd at 165 mph is safe just because the front end is "engineered" and wind tunnel tested. Do you ? If your body kit is unstable you'll probably feel it. If it broke off at speed, that might be a real problem.

How is negative lift not the same thing as downforce...

You know, after reading Fred's posts in this thread (no offense, but damn...) and the shit that Greg Schroeder is trying to pass off in the kills forum, I'm starting to think that they don't teach Physics in Arizona... :p:

https://www.rx7club.com/showthread.p...hreadid=256477

https://www.rx7club.com/showthread.p...hreadid=251537

You don't need physics. Just limit the airflow under the car. Look at bonneville cars. They just lower them to the ground. Physics explains it, but it is a simple concept.

BTW Jim, feel free to post some physics equations that explain the aerodynamics of stock and aftermarket front ends, so we can discuss.

What's the point... you just lower the car a lot, which is why a McLaren F1 is stable at 240 mph, and an FD flips at somewhere around 215... right?

I don't know about the F1, but I'd like to find out. :-)

Wow! Yeah, Jim! By this logic, some of the retarded Civics around my house should be stable at speeds approaching 250! :crzyeye: Guess I better watch out for them from now on...

:rofl:

[QUOTE]Originally posted by Fred Sickert

Quote:

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Originally posted by Kento
Actually I don't think you will create problems by limiting lift, which is what is dangerous at speed. Maybe if it broke and you suddenly had more lift. More to the point, I don't think driving your fd at 165 mph is safe just because the front end is "engineered" and wind tunnel tested. Do you ? If your body kit is unstable you'll probably feel it. If it broke off at speed, that might be a real problem.

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:rolleyes: Crikey...the way some people on this board try to "read into" someone's reply with blinders on...

Did I ever say that driving the FD at 165 mph is safe? Did I say that you can "create problems by limiting lift"? All I was stating was that your own post implies that all these aftermarket bodykits "modeled after a race car" are safe to use at those speeds, and that you "don't need wind tunnel testing" just because whatever lip or air dam looks good enough to block airflow under the car. You speak of blocking airflow under the car as the end-all to high speed aerodynamics, but that is a totally misleading statement.

Suffice it to say that simply "blocking the air" from going under the car with any old bodywork that looks like a race car will be "OK" at high speed is backyard engineering at best, which is why production and race car manufacturers use a wind tunnel in the first place.

Would I "feel safer" driving at high speeds in a car that has actually been wind-tunnel tested and engineered, versus a car with bodywork that uses "race car styling" as its design basis? Yes.

Also, I wonder if the FD driver that Jim speaks of sensed that his car was unstable just before it flipped...

I had heard that Mugen actually wind tunnel test their products but that was about the only aftermarket firm that does (I don't count Mazdaspeed since its part of Mazda now).