BUILD THREAD 86 GP 2+2~Blown 6.0
- Thread starter 81cutlass
- Start date
HOLY JMOLY Batman! This is upgrade time. No matter what you find, a Set of Moser or Strange axles with 1/2" studs, as wingnutks, mentioned would be money well spent. You had to be close to a mess with this.
Again, congratulations!
Thanks!
Yeah these are Moser 30 spline axles that are drilled for 7/16-M12 press in or 1/2-20 screw in studs.
I think I am going to drop a set of 1/2 screw in them. I am surprised to see they are bent over like that, I am honestly pretty attentive to checking them every 2-3 passes. They don't ever loosen up & although I don't use a torque wrench I do use a breaker bar that's 2ft long which I have mind-calibrated my brain to know where ~90ftlb is. I think spec on a M12 lug is 80-90ftlb. Regardless, it's not enough. I need more torque to gain more clamp load apparently.
I am going to check break away torque on the lugs with my electronic torque wrench tonight and see where I am, I expect to be enough. I run that 1/4" alum spacer to get the wheel away from the frame a bit so it doesn't rub on launch. I don't think that's causing that much of a problem as there is no indentation due to the clamp load
I can run up to 120ftlb on a 1/2-20 so I might need to look at that & carry my electronic torque wrench set to 120 next time.
Math bomb incoming..... I was accused of being an overthinker by one of the sponsor/professional performance shop/tuners at Drag Weekend. He's totally right.
An M12 to 90ftlb gets 11,500 lb of axial clamp, x5 = 57,500lb of clamp load. Coeff. of fric of clean steel on aluminum is .61 so there is 35k lb of clamp load on each wheel or 70k for both wheels.
A 1.57 60ft gets 1.33G
And the car weighs 3800lb (rough guess) so there is 5050lb of force that is see between the tires and the road. At a 28" tire, that's 14" radius so there is 5900ftlb of torque at the axle. 5900ftlb at 4.75 diameter bolt circle, or 2.375" radius is 30,000 lb.
Basically, for a 3800lb car to 60ft in 1.57s, there has to be 30,000lb of clamp load between the wheel and tire at 4.75" bolt circle to prevent the wheel from spinning on the rotor. I should have 70,000lb of total clamp load BUT that's for both wheels. If at any point only one wheel is taking 100% of the load which is possible, each wheel only has the capability of holding 35,000lb.
So the math checks out. A 1/2" stud @ 120ftlb gets 20% more clamp load which gets each wheel up to 43,000lb of clamp load. 1.43 safety factor instead of 1.16.
A 1/2" stud has something like a proof strength of 20klb so I could run it up to 140ftlb if need be. Should be fine on a steel wheel.
Oh and to-do items?
I need to find a way to limit boost, or at least power, in 1st gear. I have done about everything logical with suspension tuning (shocks, tire pressure) and if the car is running a 1.58 60ft, that's pretty darn good for my power level! If it doesn't spin it would probably be even better.
Looking back when I was running 9.5-10 psi on the big pulley at Byron & Cordova it was boarderline folding the tire in front of the centerline (below). I think these Hoosier DR2 are a bit 'floppy' compared to a M/T. At 10psi the tire would jitter/fold up about 1 second into the run, maybe 25-30ft out from the launch. At 11.5 psi it did the same wrinkle for the first 25ft or so but when the power came in off the 2 step it would always spin. I tried tuning it out but I am basically out of options. I think the tire is getting two distinct power loads ,on the clutch slipping, (4400 rpm) and clutch grabbed, full power, 5000+ rpm, no slip, and that transition from on the 2 step to off the 2 step is too abrupt and it's shocking the tire into a spin.
5000 RPM, 17 degrees, 11.5 psi at ~1 second off the launch is too much. 10 psi was boaderline. I bet 6-8 psi would be great. It ran a 1.57 60ft spinning about 1-1.25 seconds into the pass. It fully grabs maybe 2 seconds in?
So I can either
A) kill timing, possibly by shorting the IAT out in 1st gear? Issue there is I don't get IAT data (mostly unimportant), but I could trigger that in 1st gear only easy.
B) use the blower boost bypass valve and a needle valve with a solenoid that's triggered off the 1st gear clutch delay activate switch to open the bypass valve and bleed some boost off. Think old school GN boost control on the dash, just controlled with the 1st gear switch.
I need to find a way to limit boost, or at least power, in 1st gear. I have done about everything logical with suspension tuning (shocks, tire pressure) and if the car is running a 1.58 60ft, that's pretty darn good for my power level! If it doesn't spin it would probably be even better.
Looking back when I was running 9.5-10 psi on the big pulley at Byron & Cordova it was boarderline folding the tire in front of the centerline (below). I think these Hoosier DR2 are a bit 'floppy' compared to a M/T. At 10psi the tire would jitter/fold up about 1 second into the run, maybe 25-30ft out from the launch. At 11.5 psi it did the same wrinkle for the first 25ft or so but when the power came in off the 2 step it would always spin. I tried tuning it out but I am basically out of options. I think the tire is getting two distinct power loads ,on the clutch slipping, (4400 rpm) and clutch grabbed, full power, 5000+ rpm, no slip, and that transition from on the 2 step to off the 2 step is too abrupt and it's shocking the tire into a spin.
5000 RPM, 17 degrees, 11.5 psi at ~1 second off the launch is too much. 10 psi was boaderline. I bet 6-8 psi would be great. It ran a 1.57 60ft spinning about 1-1.25 seconds into the pass. It fully grabs maybe 2 seconds in?
So I can either
A) kill timing, possibly by shorting the IAT out in 1st gear? Issue there is I don't get IAT data (mostly unimportant), but I could trigger that in 1st gear only easy.
B) use the blower boost bypass valve and a needle valve with a solenoid that's triggered off the 1st gear clutch delay activate switch to open the bypass valve and bleed some boost off. Think old school GN boost control on the dash, just controlled with the 1st gear switch.
P01 yes. For auto, sure, for stick, no. I don't think there's a way for the PCM to know what gear it's in with a manual. Which is another problem, it's an auto 60e OS because there is no such thing as a DBW, flex, t56 OS, and nobody has created one from my research.
So a bit of other updates. I mentioned Sunday one of my blower idlers blew up. I noticed after my 3rd pass that there was some melted plastic on the back side of the accessory drive when I popped the hood and checked over everything after the pass. I looked and noticed the idler had reached terminal velocity and shot pieces off.
Luckily the guy parked next to me had a 3" idler, this one was a 2" but easy swap. Just had to notch the water pump slightly and bingo-bango we were back up.
Anyways, I went through my film and processed it thru racerender.
You can see the tire wads up and about 15ft out from the launch. No matter what I did it kept doing it. I don't think it's something that tire pressure or shocks can change because I fiddled with a bunch of stuff to no improvement.
Too much powah
Not enough stud
I was thinking maybe it just bent the axle flange locally but nope, the studs are bent. They were about 80ftlb checked with my digi torque wrench.
1/2-20 screw in studs incoming
Not enough stud
I was thinking maybe it just bent the axle flange locally but nope, the studs are bent. They were about 80ftlb checked with my digi torque wrench.
1/2-20 screw in studs incoming
