SchmoozerJoe

iTrader: (2)

Well, more specifically the seat of my pants.
And FM's Pokey didn't have a transbrake... it had a six speed.
And S-drives on 17" MSM wheels.

patsmx5

iTrader: (16)

Pass 1, new personal record:





Pass 2, another new personal record:






Pass 3, another "record"






That axle survived 2 whole trans brake launches!

Luckily I had a couple friends at the track that offered to go to their home, get their truck/trailer, go back to the track, pick up my car, and tow it back to my home. I am lucky to know them, they are good people.


First launch was at 17 PSI @ 5,300, it blew the tires off and spun all the way through first and some of second. Yet the car just went STRAIGHT and was easy to control. The suspension work is amazing. Tires weren't hot enough to get grip.

Second launch was with hotter tires, and 8 PSI boost. It HOOKED and it went. 1.67 60' time! No wheel spin at all.

Third pass I meant to launch at 11.5 PSI but launched at 16 PSI @ 5200. Axle broke 0.12 seconds after letting go of the trans brake.

My hope is that the CV is busted, but the part that preloads the wheel bearing is ok. Won't know for sure till it comes apart tomorrow. Would suck to have to replace a wheel bearing with 200 miles on it.

Plan for now is to fix it and launch with a boost level that is safe, but I know I will have to upgrade something in the back if I want to launch good without breaking axles.


EDIT: Also, I got kicked off the track after the first pass, but luckily I went and talked to the guy at tech, and he talked to the owner and since I'm a regular, they let me run the rest of the night, but said I gotta have a fire jacket next weekend to run. I got a copy of the rules from them and will order the jacket soon. Apparently below a 6.39 and it's gotta have a certified cage. So I will for sure be stopping before that.

patsmx5

iTrader: (16)

Also I'm really hoping to get a video from someone at the track, but so far I got nothing. I was told the rear muffler dragged the ground on the launch. This despite the 2.5x stiffer springs in the rear??? I kind of want to see it for myself but multiple people said it was dragging the ground on the launch.

tehzack

That's a 10.8-10.9ish 1/4 mile. pos cat.

sixshooter

iTrader: (12)

FWIW, cv axles hold the most power without failing when perfectly straight. The greater the angle, the increased likelihood of breaking. If the springs were compressing a lot on launch it may be putting more stress on the joints.

Those are fantastic 60ft times for a Miata on street tires. And the mph is crazy for the eighth! So much HP!

Spend a few bucks on some little wrinkle wall slicks and let's see it pull the front wheels!

sonofthehill

iTrader: (1)

Congratulations on your times! Quick!

Condolences on your axle.

All very impressive.

Leafy

iTrader: (1)

Man, get some shocks too if you're messing with springs. Those showas aint happy even at stock spring rates.

miata2fast

iTrader: (2)

You hit a major milestone. Congrats!

I have a feeling there is a lot left to be gained.

18psi

iTrader: (76)

fast. real fast. congrats dude, 10 second car

curly

iTrader: (25)

Yes, do your best to keep the axles straight during their hardest stress periods (launch). Might consider raising ride height so they're straight under squat.

aidandj

iTrader: (5)

Guess he's finally even with Dom now.

patsmx5

iTrader: (16)

Thanks! Yeah it should definitely be in the 10s.

Thank you sir! I think your exactly right about the angle causing the axles more load and making them break since they see the most load when at the worst angle. I would like to try some slicks. Trapping over 100mph in the 1/8th is nuts The launch with a 1.67 60' is ridiculous and just pins you in the seat. I rode in a 2015 GTR that did a launch, pretty sure my car launches just as hard if not better.


Thank you. I feel bad for the axle too, it lived a short life but it was a life full of action.

Yeah, I know I need better shocks. Not sure what to buy, but on a budget right now.

Thanks! I never did get to turn the boost up, and certainly never launched at full power. I would assume I'll never be able to launch at full power. I broke an axle with a 16 PSI launch, I could launch at 40 PSI if I wanted to.

Thank you sir!

I think I'm going to try this next, that would be easy to do.
Finally.

Ok, so got an update.

I got the axle removed and swapped out with a good spare. The end that holds the wheel bearing in place was ok and still torqued up, so wheel bearing spared! Here's the next funny part - The CV joint was actually ok! It twisted the shaft off right before the CV joint.

Pictures of course.

patsmx5

iTrader: (16)

I'm having a problem with the MS. I setup an output to trigger an LED light when I hit 8 PSI, but it never turned the LED on. It's setup correctly in software, and if I put say, 20 as the trigger instead of 180, the LED lights since I idle at 38-40 kPa. Put a value above idle kPa and LED goes off. But when I do the launch, the LEDs never light. No idea why, but that is the reason I launched at 16 PSI on the last run because I could hear the thing was making a lot of boost but the LED never came on so I just launched. I gotta figure this out before going back.

Also I plan to do some kind of launch control tied to the trans brake that does a fuel cut at my target boost level, so it actually stays at that boost level.

In the future once that is working and not breaking anything, I'd like to try launching at say 20-30 PSI but use an ignition retard to pull the power back, and ramp in back in over say 1 second. That way I can launch with the turbos spooled up, and then ramp the power in as I get rolling to help prevent from breaking anything, but getting torque to the wheels as quick as possible.

aidandj

iTrader: (5)

Whats the hysteresis set to? Could have been changing too fast? Do you have a log? and tune?

patsmx5

iTrader: (16)

Hysteresis set to 1, MAP as the variable. This is what I ran.

miata2fast

iTrader: (2)

How about having a set of beefed up axles made?

patsmx5

iTrader: (16)

I would love to have stronger axles. Who, and how much is the question. I don't think I can DIY my own axles unfortunately. I think I'm going to tear this one down, clean it up, and inspect the failure better. I believe it cracked at the surface, possibly from a defect in the material (you can see a chip in the pics, I'm guessing that's where the crack started. The machining on these is very rough, you can see the machining grooves in the axles. I could polish/grind them smoother to improve the surface finish, which I know has a big affect on an axle. All the high end axles have a ground finish.

sixshooter

iTrader: (12)

You have to be making the power the V8R conversion cars do. Don't they use Getrag or Ford IRS setups? I wonder if they have built up axles.

mmmjesse

v8r with the beefy axles. hell, i bet you could just buy the axles they sell and make your own diff mounts. the getrag diffs with lsd selll for stupid cheap. like.1.6 diff cheap.

miata2fast

iTrader: (2)

Contact the Driveshaft Shop. They have a set for $800.00