Wait, pat.... What suspension are you running currently?

 

Are you pre-loading the drivetrain so there is zero slack on launch? Axles can shear like that when you get a whiplash type effect through the drive train due to backlash in cvs and diff... and I'd imagine it would be 10 times worse with a trans brake and instant power.

That or it's just too much torque.

 

I think it's making 400whp right now, so yeah V8 power. I like the idea of a ford IRS setup. Those things can be built to be bombproof I know. From my time at the track, ford diff > chevy diff in drag racing so I think I'd lean towards the ford setup, probably the 8.8.

I will do my own diff mounts if I go this route. I think the kit is like 500-1000 and it's just a few pieces I'd have to weld in anyway. I'll look into the getrag, but I hear they aren't that strong, and some of the V8 folks break them. I need to research this if it's cheap, cause I'm on a budget. But if I do have to do all the work to swap a diff, I want something that will take 1000hp (aka, I'm never gonna break it, ever. My trans is rated for 1,000hp and I've seen people put 1,400whp through it)

On their website they have axles for the regular miata diff, but not the MSM. I have a MSM diff. I could still call, maybe they have them or can make them.

I have poly bushings in the rear, with 250lb/inch springs on adjustable perches, on stock not-bilstein shocks, stock ride height. Shocks work, but they have stock damping which is almost no compression dampening, and not a lot of rebound damping.


Yes. I foot brake the car to stage like normal, keeping the drivetrain/suspension all loaded with a few PSI boost, then hit trans brake and floor it as soon as I get my second yellow and let the transbrake go when I get to the desired boost.


Question- So if I can get axles for 800 from the drive shaft shop rated for "400hp", should I? I'm making at least 500 flywheel hp, and with drag radials/trans brake, that's the perfect combo for twisting axles in half. Seems like that could be a waste if they aren't much better than what I already break.

Basically, it's probably gonna be 3K to swap in a ford diff (2K for DSS axles, 1K for everything else with DIY mounts for the diff). Should I save up and do the ford setup, or spend 800-1000 on custom axles and find out how much a MSM diff can take or if the new axles are any stronger? Tempted to just save up and do a ford setup and never worry about it again, but that will be a down-the-road upgrade.

 

Are there any beach marks on the break surface? Surface finish does a lot for cyclical fatigue. Might want to try finishing a stock set to see if that does it.

 

Yeah there is, it started from the outer surface as expected, right where the radius begins on the axle near the outer CV. it's a lathed surface, and the crack started the the minor-diameter of the groove from the machine work. I think finishing a set of axles would definitely help. Maybe I should do that and save up incase that's not the fix.

 

You can make a chunk of the diff upgrade cost back by selling the beefy MSM diff and axles to someone else, perhaps.

 

VIDEO VIDEO VIDEO VIDEO!!!!!!!!!! I FINALLY GOT A VIDEO FROM FRIDAY AT THE TRACK!!!!!

The turbos are so loud, it's sounds nuts outside the car. Sounds like a jet engine going down the track.

https://www.youtube.com/watch?v=sm11...ature=youtu.be

 

https://v8roadsters.com/shop/uncateg...al-conversion/

$1500. Find a $300 getrag in the junkyard.

Good to go.

 

Lovvvvvvvvvvveeeeeeeeee it

 

Very cool video, amazing launch!

 

Very nice!

--Ian

 

Glad you guys like it! I watched the video, and I slammed my head into the seat on the launch... LOL I had my helmet on after that.

I emailed V8 Roadsters and Martin about 8.8 conversions, and sent an email to thedriveshaftshop and Raxle axles about axles options. See if I get any replies, or I'll just call tomorrow if I loose my patience. I can probably buy axles and broached hubs and fab the rest, but wanna see what a kit cost since that's surely faster/easier.

 

Pat
Congrats on setting your new personal bests. That is a seriously quick car!

Did you try putting in a lower value of MAP, say 60 kPa, and try blipping the throttle? This would make it easy to test anyway.
Also, I do know that for some of the programmable outputs, if you change the settings, you need to turn the MS off and then back on, for the changes to actually take effect.
Only other thing that comes to mind, is to confirm you have nothing else that could be also trying to use the injector out F pin as an output.

Would love to see an in car video, when you get the chance

 

Holy crap man, congrats on the runs

 

Almost did a wheelie there LoL

 

Did you just ask DSS to put S2k inner CVs on a set of miata axles for you?

 

I'll double recheck and let you know.

Thanks!


It was close. The back of the car didn't squat as much as it used to, so I'm happy with that.


I did not. Just asked some questions about their 8.8 axles. Still undecided right now what I'm going to do. I have 4 or 5 spare MSM axles, a spare MSM diff, and the MSM diff and axles in the car now (of which one of the axles has like 10 miles on it with no hard driving at all, the other axle and diff have been abused but otherwise work great). So I can definitely sell all the MSM stuff and recoup some of my money on a ford swap. It's got me looking into the cost and work it would take to do the ford conversion.

 

Yea, beach marks propagating from an initiation point that's at the root of a lathe cut. That was cyclical fatigue initiated cracks... although not that many cycles. Smooth that bitch out and polish it up real nice and see what breaks next.

 

And Shot Peen, if available, to have outer 'fibers' in compression.

 

Going ford 8.8 aluminum Diff and DSS 900HP 31 spline axles. Probably run 3.55 gears, probably running TrueTrac LSD. Diff and axles already ordered, and diff has 3.55s in it already. Still reading up on various LSDs for this, but TrueTrac seem to be a good one and strong.

Going to put my spare MSM diff/axles up for sale soon! Will also sell the stuff in the car after the swap is done.

EDITED for more detail.