SCCAITS

iTrader: (3)

In my research I saw the postings in the 2nd gen section. I've already pulled my tranny and since I am having that rebuilt again, but this time trying Miata gears, I want to replace my driveshaft because it's the very last part on the car not to have been rebuilt or replaced.

Am I going to get anything from the Mazdatrix aluminum driveshaft other than less money in the wallet and a couple pounds off the car? If I could free up 1-2 hp or get increased acceleration then I'm all for it. If not, I'll just go with the steel one they have as I don't need to lose any more weight.

I've already got most of the other good stuff, 5.12 rear, aluminum flywheel, 2 piece rotors, top HP motor, etc so I'm getting close to having everything maxed out.

rob81gsl

iTrader: (3)

take your stock one to a clutch/drivetrain shop and get one made, should be way cheaper than buying theres.....

SCCAITS

iTrader: (3)

Thanks for the idea but the two I talked were both more expensive than Mazdatrix. One could do steel and the other steel and aluminum, but nothing at the price Mazdatrix had - only more.

So, back to the aluminum vs. steel driveshaft. Any REAL performance advantage? I need to get one ordered this week.

jgrewe

iTrader: (1)

Just so you know the owner of mazdatrix doesn't even run the aluminum ne in his EP car.

Read my old thread before you spend https://www.rx7club.com/showthread.p...eshaft+daytona

Stock is the best bet for the money, carbon fiber is next if you want to spend a grand.

SCCAITS

iTrader: (3)

Thanks John. I would have thought Dave ran the aluminum one. I would also think both the aluminum and steel versions he sells would hold up to the high RPM but it looks like you are recommending a new OEM replacement as the best solution for the money.

SCCAITS

iTrader: (3)

Spoke to Mazdatrix, makes sense Dave does not run it in his EP car as he's not running the stock tranny. Mazdatrix claims the aluminum one will improve acceleration like a lightweight flywheel. The also say both the steel and aluminum versions they sell both can take a 9k RPM motor.

a2dadamm

iTrader: (1)

go for it. I was looking into the aluminum mazdatrix ds as well, if you do decide to go for it please fill me in on how you eel about it.

Thanks

jgrewe

iTrader: (1)

He didn't run one when he had a Miata gear set in the stock tranny, I don't know what he has gone to now for a gear box. Remember, they're trying to sell you something, this comes from an email straight from Dave a couple years ago when we were trying to figure out what to do with the car your diff came out of.

wrankin

That's a funny claim about "can take a 9k RPM motor" since the driveshaft spins in proportion to road speed, not engine speed.

Curious.

-bill

AWDRFTR

i have yet to do a alu prop shaft in my fc, but i have already done it in my s13 and to many other cars, it mainly comes down to physics...rotating mass and torque transfer. it takes a larger amount of effort to move a larger amount of mass. the alu prop shaft has less RM than steel. however, with steel having more density, it wont flex as much as alu. but then it also comes down to how much torque is being transfered. that is why my porche and evo customers, my suggestion, have theirs CF filament wount. because CF does not flex. but then question comes on, how much do u want to spend? Alu prop shafts r not bad, heck they use them in lemans ( Corvette, aston marton, and porche {they have alu half shafts since they have transaxles} have Alu shafts) and corvettes from C4 to C6 have them stock, and they produce 380lbs of torque and up. C4 vette has 380. just in case u r wonderin wer the number came up. i say its a good investment for the acceleration u want.

AWDRFTR

how much r they charging u? because alu tube is not that expensive. i spend at the most..$300 to get mine made, only because it was for a 62 ranchero ls1 swap and it was pretty long. for my 240, it actually cost me $240, thats cuz it was made to adapt the vq tranny to the s13 rear diff. my fc is gonna be the cheapest.. i know because im gonna pull the engine down and back furher, so less material is cheaper cost, and the fact that they r short to begin with.

AWDRFTR

another thing you mant to look into is to bring your engine down and back further. the streighter and shorter the distance from trans to diff, the better and easier it is for the engine and trans to transfer torque to the rear wheels.

wrankin

I imagine that engine relocation is pretty much a no-go when running in a limited prep production series like NASA PT. Although you never know - they probably have a points cost scale for it somwhere. ;-)

-b

SCCAITS

iTrader: (3)

Move the engine up to 10 inches for 7 points! I won't be doing that though, while I am running it in NASA PT I would like to keep it more like an SCCA EP car as maybe one day I'll want to go back to SCCA and run it there. It will never be an ITS car again, that's for sure.

The costs for shafts are all about the same...

Mazdatrix aftermarket steel - $267
Mazda OEM from Mazdacomp - $306
Mazdatrix aftermarket alum - $382

I still have not made up my mind as my new tranny won't be ready for at least another week, right now leaning towards the OEM shaft.

cpa7man

iTrader: (2)

Now that's a plan! Just go for the alum shaft. That should help a little. I've got a bad vibration and am going 2 piece mazdacomp.

SCCAITS

iTrader: (3)

I was able to get in contact directly with Dave himself. He told me OEM was the best way to go for a race car b/c we spin so much faster than a street car. He could have tried to sell me his and didn't. Thumbs up for Mazdatrix.

jgrewe

iTrader: (1)

And that, my friends, is why I try to deal with them as much as possible.

Silkworm

I want you guys to think carefully about how your drivetrain works and then explain to me why your driveshaft spins at any higher RPM than other cars.

wrankin

Probably referring to higher average road speeds plus in many cases a higher rear-end ratio when compared to a street car. But that only really puts you at maybe 2x over your average highway cruiser, so it does seem kind of an odd statement.

-b

Silkworm

seen plenty of 3/4 tons with 4.56 rear gears, and 4.10s have been a common mod for cars like my F-body for years, so the RX-7 isn't geared out of line with a lot of cars.

Not saying Dave at Mazdatrix is wrong to suggest steel over aluminum for race applications, just suggesting that structural failure due to high RPM use is probably not the reason for suggesting it.

jgrewe

iTrader: (1)

And how tall are the tires on those trucks with the 4:10's and 4:56 gears? 30"? 36"?

As for the T/A, how long do you spend above 130 mph with that 4:10 and how tall are your tires?

Now do the math with a 5:12 final drive and 22-23" tall tires.

At Daytona an E Prod car will spend over 1 minute above 130mph each lap, I could pull some data and give you an exact number but my laptop is at the shop.

We ran the numbers and found the driveshaft was well over 10,000 rpm for a long time each lap. Plug that rpm into your examples and you'll see that you would probably well over 200mph to see those driveshaft speeds on either one.

The problem isn't failure at first, its balancing. The shaft will wobble around and do ugly things to u-joints, bearings and bushings, thats when the sh*t hits the fan.

Silkworm

On the TA, tires are 25". I don't spend a whole lot of time over 130, but I've got one friend who ran the open road races in the unlimited class in Nevada with a Camaro several years ago, averaging 170 for however long the course was, but well more than a minute I'm sure, but I don't know what kind of driveshaft he ran, I'll have to ask him.

I know my car will hit 125 at the end of T-hills straight and then I'm down until 100 for turn 1, but then I also don't run an aluminum driveshaft for rules requirements. I do run an aluminum one on the Trans Am, but back when I tracked the TA I was still pretty clueless and probably never topped out any faster than the 7 does on the straight.

I'll have to defer to your experience with the EP car, although I'd also say that most road racers never sustain 130 for more than a minute on any course other than a super speedway. How many other folks here really do that?

PaulC