ExpensiveHobby22

I agree. By "good" driver I should have said "professional driver" with experience improving car in this manner.

dgeesaman

iTrader: (7)

I would be concerned that these changes in ride height would mess up the suspension geometry and angles. Unless the range of motion were designed with this kind of thing in mind, the elevated stance would have to be for non-road / non-performance driving (like a dyno ramp or other low-clearance situation).

Dave

FDNewbie

iTrader: (10)

Alberto, thanks for the info! I do, however, share the same concern as Dave. I've always heard that airbag suspensions (which is pretty much what these are, from what I've read on their site) make your handling go kaput. But if this is only the case when they're inflated, and when deflated it's as if they're not there, I wouldn't see a problem w/ them at all. My use for them is very much like Dave mentioned: keeping my car in one piece when I lug it around town. Speed bumps, driveway entrances, ramps, etc are a MAJOR issue at many times, even when you take them sideways, and at other times there simply isn't enough room to take the entraces at such an angle.

Another concern I had was it seems this is a complete suspension replacement. I don't know anything about this suspension, and how it would compare to a very nice set of coilovers, because when it comes down to it, I'll take the better performing suspension over the more convenient one.

I'd love to give TireRack or Praxis a call, but a) TireRack guys are...well...not the most knowledgeable staff (if it's not OEM), and b) I'm sure the Praxis guys know a hell of a lot more than I do, so I wouldn't get very far w/ them given the knowledge gap.

Very good point Dave.

Yea I've wondered that myself. I think he told me once before, but it escapes me now. Whatever it is, he sure knows what he's talking about.

FDNewbie

iTrader: (10)

Dave (and others who are interested in the Praxis suspension), check out this thread: http://forum.e46fanatics.com/showthr...8&page=1&pp=20 and also the thread mentioned in the very last post (http://forum.e46fanatics.com/showthread.php?t=202658) Lots of good info.

Apparently this system is it not an airbag system; it's controlled from the cockpit, monitors dynamic load levels, allows you to change and customize spring rates and dampening values very quickly and on the fly, and corner balances on the fly (in track mode), AND doubles as a compressor you can use to inflate your tires! The load leveling always occurs and will adjust for driver, fuel, and even passenger and luggage differences. The air springs become stiffer as they get lower. The lower you go, the stiffer it is going to get.

You can set the settings as you'd like ONCE, and they'll always be precisely as you like them in the future. And when you drop the suspension, it will camber in the wheels to the right setting for each height.

The system adds about 30 lbs total, and it's mounted low, as to not impact the center of gravity. Also, it's NOT an airbag system; it's actually a system of concentric air springs, much like the one on the M5. Mercedes, Lexus, and Volvo also use adaptive suspension s w/ air spring systems on their cars. The strut is designed off-center so as to provide doubling of the spring rate on each lower setting.

I really like that you can dial in and SET your settings (so you don't have to redial them), you don't have to pull off the wheel to change the ride height, it's quick, and of course it's convenient to be able to check and inflate your tires from your car lol. But I'd love to hear opinions and $0.02 from you guys, esp. criticism.

~Ramy

Kento

Yeah, you better believe that statement "the lower you go, the stiffer it's going to get." The problem with using compressed air as a spring is that it's extremely progressive; far more than a metal spring. There's a reason why so many racecars still use metal springs to handle the dynamic ride height function of suspension (and why racing motorcycles tried it years ago, but dropped the idea). Without going into a long post about suspension theory, basically what happens is that as the suspension travel gets farther into the stroke, the resistive force of the compressed air quickly overpowers the rebound damping, leading to a "pogo" effect unless you stiffen up the rebound damping rates at that point. This leads to compromises in damping rates to compensate for the rapidly rising spring rate.

So basically with this kit, it's either having cool adjustable ride height, inflating your tires, etc. on the fly, or having proper spring and damping rates in your suspension.

rotorbrain

wow, a lot of this stuff is pretty much way over my head. . . i DID dabble in underbody trays for a friend of mine who was racing go-karts (circle track) for a little bit. its very hard. especially when you have a giant sitting in such a little compartment. hahaha. the first one that i made (using lexan) was an UTTER failure. we made ducts in the underbody tray (take note: winning a race with a go-kart isnt necessarily having the fastest ride on the track. . . it has a lot to do with MESSING UP the drivers around you), the ducts were routed to the rear of the go-kart. the idea was to create a turbulent area behind the "winning" driver that would keep other go-karts from being able to draft effectively. while it worked in that department, it ABSOLUTELY FAILED in the stability department. the driver wasnt able to keep the kart steady in turns. it wanted to push to the outside BADLY. very unstable. the next design was with no ducts. . . but it was flat. it worked a little better FOR THE DRIVER. he was only able to drive the go-kart on one track that way, because he ended up "retiring" to his new family. . . totally understandable. i WANTED to use aerofoil technology in the next pan, but for obvious reasons wasnt able to. it was basically gonna be a "make and play" application. . . and im sure it would have proven to be VERY INTENSE testing. hes a good driver and communicated well, but a lot of the technical aspect of it was beyond our knowledge. if he were still into the scene, id be doing it w/o a doubt, but thats neither here nor there.

the nice part about the kart was that it was already flat on the bottom. . . just needed a tray. this differs greatly on a car. . . especially one that is ALREADY designed to be so low. ground clearance issues would be greatly effected. very interesting. . . im sure ill be dabbling with it in the future. . . again. . . THANKS RAMY. . . . hahahaha.

FDNewbie

iTrader: (10)

Wow...that's some good insight. I guess for a show and no go car, this would be great to have, but if you say traditional coilovers are still the best way to go, I'll take your word for it.

You know what's interesting? The NSX (at least the old ones...I was looking at a '91) has a FLAT bottom, w/ NO undertray. I was greatly surprised/shocked. But I mean when I say flat...I mean flat. And for a very good length of the car...maybe (the middle) 3/5 of it.

Not sure for what lol... I'm just brainstorming, and I think all my ideas were shot down but that's all good. As I told Kayin the other day...I'm more afraid of being an idiot than being called one (hence my lack of fear in asking 1001 questions)

~Ramy

rotorbrain

haha, i was thanking you for getting me interested in this again. . . just a tad bit of sarcasm there. hahaha. . . my wife will be cursing me/you.

FDNewbie

iTrader: (10)

CrispyRX7

iTrader: (139)

Ramy,
Sorry I'm late but a few basic cryptic thoughts which basically ask what the real need and benefit of these items is. Keep in mind ANY time more complexity is added to an equation the greater the propensity for failure

Ride height control: Others use it as well but mostly high end SUV's like Range Rovers I believe. So you want the ride hieght to drop the faster you go, eh? The purpose to reduce aero losses at high speed. For a DC area street car I doubt you will ever see that gain. On a BIG floaty SUV sure but more for rollover stabilty at highway speeds than for areo gains. Stick with a fixed hieght suspension is my opinion. PS consider also tire and wheel clearence with changing ride heights.

Air pressure monitoring: primarily intended for use with run flat tires. Are you going to use run flat tires on your FD? Is so then yes definitely. Other wise it migth be a neat system to have and can probably be easily retrofitted. Howver nice the data may be you have to knwo what top do with it to make full use of the system other than to tell you whan you have a flat tire. Even on the track twiddling with tire pressures between sessions is going to tough without knowing what the proper or appropriate target pressures are.

Traction control: Racelogic seesm to be the ticket. And sure I'd tink it potentially a good idea if you car is driven in limited traction situations. Me, I never drive my car in the rain anyways so I'm not too bothered

Sequential twins: In todays day and age a quick spooling single can be just as effective. Sequential twins are 90's tech. Stress: my opinion.

Underbody design: Unless you have a windtunnel at your disposal this will be a long road to travel. Evne the aftermarket diffusers I see IMO have questionable merits given the lack of any other underbody cladding inder an FD. My concern with enclosing the underside of the FD is one of heat rejection. Close it all up and where is all that heat going to go? It's hard enough cooling an FD as it is but now you will have a boxed up tranny, exhaust, etc etc. Think that most fully underclad cars are rear or midengine mounted dont; have the same issues as an FD does.

A few crytpic thoughts,
Regards
Crispy

scotty305

iTrader: (2)

Bump for a fun thread. I'd like to hear more people's opinions on this subject, and there's no need to limit the discussion to just the things that Ramy (FDNewbie) mentioned.


-s-

stephentross

I was doing some research on upgrading electrical systems a few years back. Interesting thread.

See this link
http://www.danielsternlighting.com/t...ys/relays.html and this one

http://www.dimebank.com/Light-up.html

As for air pressure monitoring I think that this is something every car can benefit from having. No matter how much you check your pressure, you will never be able to check it as much as one of these babies, plus you gain more piece of mind than is possibly imaginable.

Neo

iTrader: (3)

This is a very interesting thread...

The majority of the cars on the market today can't go on without having 4-8 airbags, traction control, adjustable suspension, etc... and these are the things I hate about modern cars! Yes, that's right, I really don't like the idea of having 4-8 airbags in a car. Let alone traction control... Granted, some people really like the idea but I don't. Probably because I deal with computers all day... lol

There's 1 thing I really want to put on the car and that's the diffusers. I've been looking at some of the ones avaliable and I'm not convinced.
However, I've found these "undercovers" avaliable from Mazdaspeed! Now we know Mazdaspeed must have tested these components in the windtunnel, right??
My problem is trying to find them!!

My front undercover is torn up a bit and kinda hangs from the roll bar points... the reat plastic lip close to the exhaust has melted (damn those N1's! lol ) So I've been trying to find these pieces and the only place I've seen them listed is on Mazda's website in Newzealand!

Does anyone know where I can find these undercovers???

Lates,

FDNewbie

iTrader: (10)

Scotty, honestly, I'm amazed, because there just doesn't seem to be THAT much room for improvement in the FD. If the motor was a bit more reliable, that would be awesome, but then again, what do you expect when ppl are trying to make double the hp outta the block? It ain't a 2JZ that's simply a hp MONSTER...

Neo, I can get those diffusers for ya no problem. Just a warning ahead of time: have you ever priced a genuine Mazdaspeed part? Cuz it ain't pretty... PM me if you're seriously interested.

~Ramy

EDIT: The Mazdaspeed rear diffuser will fit on the stock rear bumper, but it may take a bit of work to fit onto the stock 93 - 95 front bumper, as it was designed to mate with the 99spec bumper (I think that's obvious from the pic).

neit_jnf

iTrader: (17)

One of the latest FD's in Japan had adjustable ride height or was it adjustable damping? The RX-8 has drive by wire throttle, Traction and stability control and trie pressure monitoring system.

Mazda also developed an electrically assisted turbocharger for the hydrogen RX-8 that spools at 1000 rpm thanks to the electric motor, then when the exhaust gas velocity and energy are high enough they drive the turbo conventionally...

So, apart from the underbody design, Mazda already has worked with these ideas and it's possible they'll be incorporated in the new RX-7 if it ever becomes real.

Kento

Unfortunately, modern safety and driver aids like airbags and traction control are a necessary component for cars to survive in the market these days, whether through regulation or sales marketing.
I'm thinking the reason they haven't developed this further is because being able to use a larger turbo with this setup will only cause more problems with the fuel consumption characteristics of the rotary that Mazda has been struggling with since day one.

neit_jnf

iTrader: (17)

The latest rotary car Mazda displayed has a gasoline electric hybrid direct injected Renesis, direct injection may be the solution to the gas consumption characteristics inherent to the rotary design.

Skeltah

One word... Lasers
you know you want em

scotty305

iTrader: (2)

I think neit_jnf has hit the nail on the head. Direct injection would practically eliminate preignition/detonation problems as well.


-s-

F0RSAKEN

How so? Is the fuel injected later in the compression cycle, after the rotor has gone past TDC? (not even sure if rotaries have TDC/BDC).

Julian

iTrader: (14)

Lotus has done the most work on active suspension. Best bet is to search professional engineering society publications.

Kento

Not necessarily a "solution", but it will help. The big problem with the rotary is that it has a comparatively huge combustion chamber surface area that is rectangular in shape. The rectangular shape not only isn't very efficient for combustion (flame fronts in the combustion chamber travel outward in an expanding circle, not square), but the surface area means that a lot of combustion heat is absorbed by internal engine components. That means that thermodynamic efficiency (which produces power) goes down, and that absorbed heat has to be transferred somewhere (the oil, which is why track-run FDs need major oil cooling), otherwise you suffer engine meltdown.
Direct injection allows more precise fuel delivery and better combustion chamber turbulence that permits leaner a/f ratios to be ignited, but that doesn't guarantee that preignition/detonation will be eliminated.