does anyone know how much the polyurethane injected crossmember costs from mazda?

its the one that comes on the shinka's and the new R3. thanks for the help

nope

nope

lol ok seriously anyone?

Why would you want that? Waste of money.

Why would you want that? Waste of money.

because the shinka's have it and its one reason why they handle better than other rx8's...

because the shinka's have it and its one reason why they handle better than other rx8's...


Your kidding right? The differences in the Shinka means nothing on a track. Obvioulsy you don't autox or track. There are many other tracks mods to be done that would be way more beneficial.

Your kidding right? The differences in the Shinka means nothing on a track. Obvioulsy you don't autox or track. There are many other tracks mods to be done that would be way more beneficial.

wha what?! the shinka's on the track are superior to other rx8's. the poly injected crossmember helps with stability and the shinka's also get upgraded bilstein shocks and a different limited slip.

as far as other track mods, well if u had the crossmember it would only be one more thing on top of w/e else you get anyway thats better.

EDIT: if this wasnt so, then they wouldnt put this stuff on the new top of the line performing R3's now would they....

Well if the Shinka was that much superior...Wouldnt all the RX8's running B Stock at Nationals have a Shinka?

And how many of them had a Shinka that were in the top...20...

None

:)

Well if the Shinka was that much superior...Wouldnt all the RX8's running B Stock at Nationals have a Shinka?

And how many of them had a Shinka that were in the top...20...

None

:)


it wasnt that much superior, but that little bit helps it make it better slightly.

like i said before, would the new R3's have the stuff if it didnt do anything?

EDIT: also, shinka's had a limited production run compared to other rx8's and usually go for more so the odds of one being raced are slimmer compared to the "run of the mill" rx8's

wha what?! the shinka's on the track are superior to other rx8's. the poly injected crossmember helps with stability and the shinka's also get upgraded bilstein shocks and a different limited slip.

as far as other track mods, well if u had the crossmember it would only be one more thing on top of w/e else you get anyway thats better.

EDIT: if this wasnt so, then they wouldnt put this stuff on the new top of the line performing R3's now would they....


Whatever dude, your clueless. The driver mod is what you should be worried about.

Oh, and by the way, the non foam injected cross member MSRP's for $714.39. You should get it and teach us all a lesson.

The R3 is not really any faster than the GT. Period.

The R3 is supposed to handle better because it has Better Shocks...

The R3 is supposed to handle better because it has Better Shocks...

Mass produced bilsteins are so JDM racer yo!

ok well at any rate thanks for the info on the non filled ones. i was just wondering how much they costed.

im looking into my rx8 and am debating whether to spend the extra money on one later on thats all. seeing if its worth it

ok well at any rate thanks for the info on the non filled ones. i was just wondering how much they costed.

im looking into my rx8 and am debating whether to spend the extra money on one later on thats all. seeing if its worth it

Look man I'm giving you shit but it's all in good fun (for me anyway :lol:) and I truly hope you realize that a lot of little BS the manufacturers don't really add up to real world performance.

In reality it was just an excuse to charge way more for the Shinka. I remember way back when I got my car there was a Shinka on the floor next to mine and it was almost $10,000.00 more!!! I know prices have dropped dramatically but the the differences in the Shinka are just not worth anything in terms of performance.

Hell for about $2,000.00 you can get a set of decent coilovers and sways. But honestly you can have every mod in the book and get whooped by $5,000.00 Miata. If your just buying mods for the sake of modding then it's all good, just don't hype the performance aspect of those parts.

Nothing I hate more than for a guy to tell me how awesome his JIC coil overs are when his car has never, ever been on a track or Autox course.

it does nothing, seriously...the shinka is another run of the mill rx8, with a different "title" and interior...what you would spend on a shink as apossed to GT, you could make it "handle" a lot better

OP name Rotarypiston...just wanted to say that

this thread...

:lol:

Just a minor point of clarification: Tokico (not Bilstein) on the '05 Shinka.

wha what?! the shinka's on the track are superior to other rx8's. the poly injected crossmember helps with stability and the shinka's also get upgraded bilstein shocks and a different limited slip.

as far as other track mods, well if u had the crossmember it would only be one more thing on top of w/e else you get anyway thats better.

EDIT: if this wasnt so, then they wouldnt put this stuff on the new top of the line performing R3's now would they....

Everyone knows Shinka's come with a 20B./

I always figured the foam filled cross members were for a better ride quality.

By concept the foam filled cross members would give a little bit more of a stiffer ride, but that's it.

Actually, a little more shock absorbing (damping) GT ride.

By concept the foam filled cross members would give a little bit more of a stiffer ride, but that's it.

The shock absorbing done is by the foam to assist with the cross members to resist flexing/bending thus, stiffer.

Look man I'm giving you shit but it's all in good fun (for me anyway :lol:) and I truly hope you realize that a lot of little BS the manufacturers don't really add up to real world performance.

In reality it was just an excuse to charge way more for the Shinka. I remember way back when I got my car there was a Shinka on the floor next to mine and it was almost $10,000.00 more!!! I know prices have dropped dramatically but the the differences in the Shinka are just not worth anything in terms of performance.

Hell for about $2,000.00 you can get a set of decent coilovers and sways. But honestly you can have every mod in the book and get whooped by $5,000.00 Miata. If your just buying mods for the sake of modding then it's all good, just don't hype the performance aspect of those parts.

Nothing I hate more than for a guy to tell me how awesome his JIC coil overs are when his car has never, ever been on a track or Autox course.

o i know i give people shit all the time too. and believe me im one to say the same about people who get suspension upgrades and dont actually race them. not saying its a bad thing but why invest in something ur not going to really need.

OP name Rotarypiston...just wanted to say that

:rofl: :mdrmed: ya i know catchy huh lol

Just a minor point of clarification: Tokico (not Bilstein) on the '05 Shinka.

i did not know that thanks for the info.

The shock absorbing done is by the foam to assist with the cross members to resist flexing/bending thus, stiffer.

thats what my understanding is as well

Concur. The shock absorbing done is by the foam to assist with the cross members to resist flexing/bending thus, stiffer.

Imagine taking a Mustang for a canyon cruise. Come back for coffee and have your ace mechanic glue styrofoam to the rear axle housing. Wow, the handling must be really good now ....

Imagine going into mammoth cave with 4 tour bus fulls of kids on energy drink. Call up urethane express to go, and have them spray the inside of the cave with foam. Is it stronger? Nope. Is it quieter? yep!

If there's a benefit, it's less NVH. Any handling differences would be indistinguishable.

Thimk.

I'm sorry, but this is a gross oversimplification with obviously no regard for automotive engineering principles.

Think (spelled properly).

Imagine taking a Mustang for a canyon cruise. Come back for coffee and have your ace mechanic glue styrofoam to the rear axle housing. Wow, the handling must be really good now ....

Imagine going into mammoth cave with 4 tour bus fulls of kids on energy drink. Call up urethane express to go, and have them spray the inside of the cave with foam. Is it stronger? Nope. Is it quieter? yep!

If there's a benefit, it's less NVH. Any handling differences would be indistinguishable.

Thimk.

Which specific principles am I not understanding? Foam is foam and has little strength in compression, tension, or torsion. What it does do is dampen vibration, i.e. convert motion into heat. "Thimk" was spelled as I wished it, based on a widely-circulated series of posters representing engineering disasters. Humor, I thimk it's called.

does anyone know how much the polyurethane injected crossmember costs from mazda?

its the one that comes on the shinka's and the new R3. thanks for the help

If you're that desperate, then drill a hole and fill 'em yourself. Make sure you use a high density polyurethane, not the stuff you find at Wally World.

I am planning on doing this, and going much farther than just a crossmember.

For those who are curious, the foam isn't for noise damping. Filling a crossmember wouldn't do that. The foam does make the crossmember stiffer.

If you take any solid piece of material (let's say steel) and measure stress as it is flexed you will find that 90% of the stress is being placed on the outside of the material. The inner material doesn't really see much stress from bending. All the inner material is doing is keeping the outer material from collapsing in on itself. A prime example is a steel I-beam. They are nearly as strong as a solid steel beam, but weigh much less. The load is taken up by the top and bottom of the I-beam, and the center is just there to keep the top and bottom from collapsing. The forces trying to collapse the top and bottom towards each other are much less than the forces the outer layers see as the I-beam flexes, thus the center piece doesn't need to be as strong.

This is what Formula One chassis builders do when they build a car from carbon fiber. You think those things are solid CF? Nope! They lay it over foam. Why? Because the stresses exerted during a race are placed on the outer layers. All the inner core needs to do is keep those layers from collapsing towards each other. Again, the forces that this foam encounters are far less than the outer layers see, thus it doesn't need to be as strong as the outside walls. A CF board with a foam core is nearly as strong as a solid piece of CF, yet it weighs significantly less. A car that weighs less is faster.

This same principle applies to our crossmembers! Since the average crossmember is not filled, there is nothing to stop the outer walls from collapsing towards each other as it flexes. However, the crossmember on the R3 is filled with a high density foam and should be much stronger because there is something keeping the walls of the crossmember from collapsing as it flexes. This is simple physics.

Now, is a single, stiffer crossmember going to make that much of a difference? Probably not, since there are other parts of the car that flex a good bit and need damping. However, comparing the two side-by-side, there is a significant difference.

P.S. "Dampening" is getting something wet, like a towel. "Damping" is removing energy from a system, like a shock absorber or the foam filling.

"In Principal" sure. In practice, not so much. For the foam filling to have much effect in this way, it needs to be incompressible, which the standard sort of foam is not. The main effect of foam coring fiberglass structures is to seperate the layers of fiberglass in much the same way the web seperates two bands of steel from each other in an I beam. (The stiffness of an I beam goes up as roughly the 5th power of the web depth.) Structures are hollow in the first place because most of the strength of a piece comes from the "skin", not the "filling", so making a piece slightly larger more than compensates for the removal of the material in the middle with a large net savings in weight. If one was to take advantage of "refilling" a structure with something, it would best be done during the design process.

NVH for cars is "easy" because the car is coupled to an essentially immovable object called Earth. With airplanes, this coupling is much weaker so there's an increased awareness that vibration results in noise results in destruction of vital pieces if the vibration is not dampened (turned to heat) in a safe way. An efficient way to control vibration of a piece is to bring it into close mechanical contact with something of very different resonant characteristics. A good example is our aluminum hood meshed with the 1/2" or so sound blanket that Mazda provides on its undersurface. I suspect that will be the main effect of filling the chassis crossmembers with foam. It probably won't hurt anything at least. I suspect that the primary use for the foam in this case is to justify a big bump in the MSRP over the non-shinka GT.

The foam dampens vibration, plain and simple, which augments the GT ride quality. The magnitude of same is a feel of the beholder item.

btw: I had some experimental True Temper golf shafts a number of years back that were urethane filled. They really did do an exceptional job of damping vibration.

wha what?! the shinka's on the track are superior to other rx8's. the poly injected crossmember helps with stability and the shinka's also get upgraded bilstein shocks and a different limited slip.

as far as other track mods, well if u had the crossmember it would only be one more thing on top of w/e else you get anyway thats better.

EDIT: if this wasnt so, then they wouldnt put this stuff on the new top of the line performing R3's now would they....

:confused: You got bad information.

ok well at any rate thanks for the info on the non filled ones. i was just wondering how much they costed.


That is such a gross misuse of the word "costed" that I just have to point it out... couldn't help myself. Now, back to the regularly scheduled misunderstanding of Shinka parts.

The only thing on the Shinka that makes it handles better and go faster is the paint. It's a proven fact that Copper Red is aerodynamically and better suited for track use.

The foam dampens vibration, plain and simple, which augments the GT ride quality. The magnitude of same is a feel of the beholder item.

btw: I had some experimental True Temper golf shafts a number of years back that were urethane filled. They really did do an exceptional job of damping vibration.

whatever ya'll can attribute this to....

i've had no les than 4 people tell me my shinka was much smoother on the road than another stock 8. only two of them knew enough about rx-8's to know mine was a shinka, and only one of those knew about the crossmember and shocks. the other three all asked what i had done in suspension mods to make it so much nicer....

then again, i cannot tell the difference between my car and any other 8...?

Not to beat what looks to be a dead horse, but would foam crossmember make any noticeable difference in general ride quality?