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- - Airbags ... seriously (https://www.ft86club.com/forums/showthread.php?t=21790)

Quote:

Originally Posted by EarlQHan (Post 794615)

I drove a BRZ on bags for the first time today and it was a very strange experience. I will try to give my most honest, informed, and unbiased opinion of bags as a suspension option; not talking about a specific brand/price. I don't know which brand the bag system I drove on is so please don't ask me.

I don't know much about how to build and setup a bag system because I had never really thought about it as an option. What I noticed is the amount of spring rate adjustment you can get is insane. The system I drove on changes ride height according to pressure, I don't know if this is true for all systems. So the lower the car is, the softer it rides, but then if you're too low, there's the possibility of scraping stuff. Being scared to scrape stuff since it's not my car, I drove it at a higher pressure for a higher ride height. BIG MISTAKE. Even on what seemed like a perfectly smooth road, the bumps were magnified. It almost seemed like the suspension was creating bumps out of thin air. It was so bad I felt like I was going to throw up (meaning the car was probably oscillating around 4 Hz). On visible bumps, the rear wheels would hop and the traction light would come on.

I pulled over and dropped the pressure about 20 psi in each corner, and the car felt better. It was still firm and the preset had a high rear bias so the car pitched forward over bumps as expected with a biased spring rate. I dropped the rear pressure and the car felt much better. It felt a lot like your typical Japanese coilover (take that how you will). The final pressures were 35 psi front, 45 psi rear, but I don't know if that's a universal spring rate among different brands.

I will admit there's a certain cool factor to having bags and being able to dump it on the ground when parked, then driving away at a normal-ish ride height. However, I'm an impatient guy and like to just get in and drive. I don't like having to wait for the compressor to fill up the bags. It's just a nuisance to me. It's also overly complex and if a bag fails or blows out, it's a catastrophic failure, leaving the car immobile. If a coilover has a spring failure, you've probably hit something.

The weight aspect probably isn't as bad as most people make it out to be. The tank is typically placed right up behind the rear seat, so the weight is in between the wheelbase. People adding turbochargers/superchargers are adding weight right on the nose which will upset the balance more than adding bags. Most aftermarket wheel/tire combos are adding rotational weight and inertia. Hell, people who get interior mods like those "86" plaques are adding useless weight.

Now the interesting part about bags is the vehicle dynamic possibilities. You can change your spring rates and ride height on the fly. This is as close to active suspension as you can get on a car at this price range. The difference is, the spring rate changes, not the damper curve. Also, air being a compressible fluid, the spring rate is progressive. In a very basic sense, it means over small bumps the car can remain softly sprung, but under roll in hard cornering, the car stiffens up. This means you can get rid of anti-roll bars if tuned properly (a la McLaren MP4-12C, except they use hydraulics in a Z-bar fashion but I digress). That also means you can offset some of the weight from the bags, although the CG will be raised. It is my understanding that current air bag systems are adapted to conventional off-the-shelf dampers. However, if you could build a damper curve around a certain bag pressure or use dual-bag setups to run the spring in parallel, I don't see why it couldn't simultaneously be more comfortable and handle better than any coilover system on the market. However, to engineer something like that properly, you'd need a damn good controls engineer who excels in state-space matrices to figure out the complexities of the spring-mass-damper system.

Hope that helps. If any engineers out there think I've completely missed the mark on this, please chime in, I'm definitely intrigued by the bag system and its intricacies and I would love to learn more.

EDIT: Just read in this thread they have auto leveling systems. If it can pressurize/depressurize the bags fast enough the keep it very level this means your aero platform is now stable. If you can get a bag/damper system that is quick enough (we're talking in the magnitude of milliseconds) I highly doubt any conventional coilover would be able to keep up with its performance. Unfortunately, I don't think that kind of bag system is available yet. On top of which you'd need a MR damper with ECU. AFAIK, Beijing West and Ferrari have patents on that technology.

I appreciate your feedback, my question is did your friend (assuming your friend) have a preset ride height that he was aligned on? You were riding on pressures that were out of the alignment spec. Although this is good for testing and seeing how more pressure/less pressure effects the ride, you should have really been driving on a predetermined, aligned setting. Also, did you mess with the dampening on the struts? There should have been adjustable dampening on them.

Also, the brand of bag will also play a part in how it rides. Example, AirRex has double bellow bags in the front and rear, my AirLift system has double bellow front/sleeved rears.

Bag fill time - Also depends on your setup. I have a 444c compressor to a 3 gallon tank, and if i'm aired out, it literally takes 6 seconds or so to fill to my ride height, and off I go. If you are pulling away faster than that, well I don't know what to tell you.

There is no universal spring rate - you go by feel with a pressure based system. The eLevel (which I had previously) predetermines ride height for you. It seems if you were to do a bag setup this would be the most convenient thing for you. I must admit, theres just a lot less thinking involved with a height based system. But I am happy I switched to pressure based because you really understand how to fine tune the ride and see whats going on.

overly complex? its basically coilovers, with air line and a tank/compressor, lol. A bag will not blow out, unless you are a complete moron or there is some kind of defect. The only thing you have to check for is leaks (which is easy, you check your gauges/controller and see if pressure drops after parked for a while). That kind of blank statement is just that - my buddy had a spring rust out and break on him. When do you see that everyday? It would be stupid for me to say that springs will fail and explode just because of one incident. Most times if there is a bag failure, it is because something is rubbing the bag (whether it be the tire/wheel, or against the body of the car - yes some kits are universal and need a little "work" to fit)

As far as the elevel and automatic adjustments, it makes them every 45 seconds to make sure you are consistent with that predetermined ride height it has chosen for you.. They are very small increments and is done pretty much instantly since its not like you are filling each corner with a lot of air.

Not trying to attack anything you said, just trying to add my two cents. i'm eager to hear your reply regarding the ride height settings.

Quote:

Originally Posted by xxscaxx (Post 795183)

Thanks for the insight on setting up a bag system. I'm not attacking bags, it's just from what I've seen, but it's only the tip of the iceberg. You're right, springs can rust and break, but that's only one failure mode. A bag can blow out or a line can leak. That's two. With a traditional coilover setup, there's only a damper and spring. With bags there's the damper, the spring, the lines, the compressor, and the controller. It's more complex. I'm not saying it's rocket science, but over a coilover, there's more thought needed to setting it up. I've seen people who don't know how to setup the ride height with double height adjustable coilover, imagine if you gave them bags. Also, as bags compress, they bellow out, so you have to consider the expanded size of the bag when it's compressed. I've saw a bag that got rubbed through because that was neglected. The clearance was fine when the car was static, but it slowly rubbed through because it would contact the wheel over bumps.

To be honest, I don't know anything about the setup. My friend literally showed me how to adjust the pressure then tossed me the keys. I didn't mess with any of the damper settings, to be honest I didn't know there was damper adjustment. Also it's not my car so I don't want to mess around with it.

As for the e-level and 45 second increments for adjustment, that is SLOW. The OEM hydraulic and MR dampers are capable of adjusting the damper settings in milliseconds. Also for filling up the compressor, 6 seconds is still 6 seconds more than I want to spend, but that's me.

It seems like there's a lot more thought involved with setting up a proper air system, but if it's properly developed, and since I don't know enough, I can't make a proper judgement. However, I can see its benefits massively outweighing its drawbacks. Just like with any other technology, as the market size increases, the technology improves, the quality improves, the price goes down. I'm not 100% convinced yet, but there is a LOT of potential. You can do a lot more with it than a traditional coilover system, including handling/performance. As for naysayers who brush it off, you can't blame them. People are scared of the new and foreign, it's our nature but I'm sure more people will consider air as the systems become more refined.

you are reading me wrong. The eLevel CHECKS to make sure the height is at its predetermined level every 45 seconds. It takes milliseconds for it to adjust. Maybe a second at the most.

Good points, all very valid. Yes there are more issues that could arise, but a properly installed system will be just as reliable is my point. Nevertheless you are right - more areas of concern than a tradtional coil. If that bag you saw that got rubbed through was tested properly they would have caught that. When I set mine up, I jacked each corner to make sure there was clearance for the lines and the bags. You would notice that immediately if it was rubbing, or even coming close to the frame. Again this is kind of null since these "kits" are specifically made for the application and that is something thats checked by the manufacture before its sold.

Do you have your foot to the gas as soon as the car is turned on? :) Also, my managagement system along with the elevel have "rise on start" which will go automatically to your ride height as soon as its powered on. So that 6 seconds just turned into 2-3 lol.

Also, I wasn't saying you were attacking bags, and its the reason why I also said i'm not attacking your comment because I know it could easily be seen that way. Just engaging in conversation :D

Shame on your friend for not showing you the ropes ;)

The ONE thing I don't like so far about these pressure based systems is that going from aired out to ride height is not always 100% accurate, where as the height based system (elevel) always was, and if it wasn't it would get adjusted out anyway automatically. Thats my only gripe. I went from aired out to ride height, started backing up and heard my exhaust scraping when I hit a few bumps in my friends driveway and was like wtf? So now I go from aired out, up to a higher setting than my ride height, down to my ride height. Yes its kind of stupid lol.

I did misunderstand the adjustment. Your systems seems more intelligent but I also did a similar start procedure. My friend told me to fully pressurize the bag, to stretch them out since it makes adjustment more precise. I don't know if that's true or not, but that's what he told me and that's what I did. That's why I'm saying it just takes a lot longer to get going. Thanks for clarifying though, I'm always open to learn more.

And yes, straight to the gas. If you're not first, you're last!

https://www.clubdata.com.au/Attachme...rickybobby.jpg

lol its all good man. I never heard of stretching the bag out, but I do the same procedure just because it hasn't failed yet on getting to my predetermined height when going from a PSI over my ride height - ride height.

Wish more people were open to this like you are, but its finally cool to see someone who hasn't experienced a ride in an air equipped car give feedback, rather than someone just going off hearsay. :clap:

Thanks for informing more about what kind of options are out there. I'm an engineer by trade, so I'd be a bad one if I wasn't open to learn more about technologies. I think with a proper setup and more development there's a huge performance potential. But, to get a really good, balanced system, I think the complexity goes up exponentially. Off the top of my head, you can already get rid of cold day problems by using blanket warmer. If you use the ideal gas laws, PV=nRT, you can use the blanket to warm the air to a constant temperature. But, that's more weight, more complexity, and a big current draw, etc. Also, your auto level system should monitor the ride height at much shorter intervals, but you need a good algorithm and control system to make sure it's not trying to change height every half second. I think a good control unit could improve performance a lot too.

There's definitely merit to air, if anyone else thinks otherwise, they should just crawl back into their caves and rub sticks together. Just because show cars use it, doesn't mean it can't have performance potential. On the flip side, look at the people who put performance parts on show cars and hard park (looks to people with full Voltex aero and TE37s... makes awkward eye contact... looks away)

Love this conversation. I am also going to a air ride system. I am going to use airlift struts and the Ridetech airpod system. This will be my first air ride system so i will have lots of trial and error finding the right psi for ride height. I know every system is different but can some of you chime in with what psi you are riding at?

AIRREX system does not keep adjusting for ride height. It is pressure based but not like the height based system that accuair system has. Accuair system will always try to keep the car at the preset height. SO as you load the car it will adjust. The airrex system is just a pain simple pressure based set up with auto leveling.. so all it does is get you to your preset pressure that determines how high the car is.

AS for performance on the AIR system there is a certain way to set these set ups correctly for the track. Most coil over systems on the market are just basic dampers for everyday use. AIRREX we dont usally offer promote this option as we do have a race set up thats is made for racing. But our basic setup that everyone has performs well on the track.

AIRREX and AIRLIFT prices for the struts are almost he same price. the only reason an airlift kit comeout cheaper is becuase they have a cheaper management system that is not as easy to install as the AIRREX AMS and it is not wireless controlled like the AIRREX Controller is.

AIRREX systems have been proven winner on the race track..

Quote:

Originally Posted by eight08customs (Post 813082)

Can you share what the main difference is between track and street setup is? Can you also post some examples of track cars using your kit?

airlifts system is extremely easy to set up.

Power, ground, 12v. Connect power and ground for the compressor. Run air lines.. done. I know the airrex system is an "all in one" so i'm guessing its the same exact thing minus the two wires for the power and ground.

The elevel is more complex to set up.

Just wanted to bump this for an update.

I had previously said that my airlift system wasn't very accurate at times when going from fully aired out (0psi in each corner) to my driving height.

I enabled "ride height on start", and it seems that it is pretty much dead on now. I also talked to Jeremy @Airlift and he told me that if you are seeing inconsistencies/inaccuracy with it hitting target pressure, you can adjust this within the settings. I didn't even realize this.

It comes set at level "5" out of the box. You can adjust it 1-10. 1 being less sensitive, 10 being more sensitive I believe. I was going to recalibrate it but it seems that I don't need to.

Just wanted to share that in case anyone reads this thread, I don't want to turn them off from the Autopilot v2.

Quote:

Originally Posted by DekaMori (Post 736965)

M Technica by Memoryfab =)

What are the specs of the wheels and tires ?

Accuair: D2 front & Rear Air Suspension kit any review about the build quality of their air struts for the frs/brz?

NOT* E-level.

Quote:

Originally Posted by MVLSCROWNZ (Post 1742411)

Accuair: D2 front & Rear Air Suspension kit any review about the build quality of their air struts for the frs/brz?

NOT* E-level.

LOL

is this the same d2 as the recolored ksports d2?

cause if so quality doesn't belong in the same sentence

Quote:

Originally Posted by Model Citizen (Post 1742575)

is this the same d2 as the recolored ksports d2?

cause if so quality doesn't belong in the same sentence

That'll explain how come people mix match between Airrex bags and Accuair management system.