Melted turbine wheel?
#24
I realize engine harmonics (vibration at high rpm) cause TB hardware failures, thus all the focus on isolation/bracing the TB in high revving race cars. But this was on a new TB with <5 track hours on it before the failure in 100whp SSC Miata, stock rev limit. Shaft was cracked/split at the screw hole.
#25
Back when I was researching the throttle shaft problem, I was under the impression that everyone was doing this to their TBs unless they had upgraded to the Skunk2 TB - kind of like using Inconel turbo hardware to prevent exhaust leaks. The epoxy not only prevents breakage by strengthening the throttle shaft assembly, it changes the mass of the throttle shaft which changes it's resonant frequency and prevents future cracking.
Here's where my throttle shaft broke, both times:
My epoxy job:
Here's where my throttle shaft broke, both times:
My epoxy job:
#28
I have heard from more than one engine/racecar builder that this was an issue for high revving four cylinder engines. Both builders made said isolating the TB from vibrations was done with compressible gaskets between the TB/manifold and manifold/head, along with bracing the intake manifold. Perhaps that's why Mazda put a brace on the manifold - not for weight/load. In my particular failure I suspect it was overloading of the shaft due the fact that the cable was properly adjusted before the race. After the race the throttle pedal was bent when fully mashed to the floor (aka stomper in the SM world) which of course altered the throttle cable tension. Unfortunately I neither have data to prove or disprove what caused my failure. But I can say that in the following 15 years of racing Miatas after that incident it never happened again on that car, nor five others.
#30
It doesn't feel quite as hard as JB Weld, but it's hard enough that my fingernail doesn't leave a mark on it.
With the scuffing and cleaning I did to prep the surfaces before applying the epoxy, I'm far less worried about ingesting the epoxy than I was about ingesting a throttle plate screw.
With the scuffing and cleaning I did to prep the surfaces before applying the epoxy, I'm far less worried about ingesting the epoxy than I was about ingesting a throttle plate screw.
#36
Emilio,
I propose using an accelerometer board to be able to log the G's that the throttle body is being subjected to. This little guy is $37:
EVAL-ADXL326Z Analog Devices | Mouser
It's a 3-axis unit which will measure up to 16 gees. I can build you a little interface circuit to output a 0-5 V DC voltage proportional to peak G's, all 3 axes if you like that you can then datalog. Then we can look at g's vs. RPMs (and MAP or TPS).
This way we can look and see if there is a particular RPM where the IM resonates at, and see if the manifold brace changes the peak value or the resonance RPM, etc.
I propose using an accelerometer board to be able to log the G's that the throttle body is being subjected to. This little guy is $37:
EVAL-ADXL326Z Analog Devices | Mouser
It's a 3-axis unit which will measure up to 16 gees. I can build you a little interface circuit to output a 0-5 V DC voltage proportional to peak G's, all 3 axes if you like that you can then datalog. Then we can look at g's vs. RPMs (and MAP or TPS).
This way we can look and see if there is a particular RPM where the IM resonates at, and see if the manifold brace changes the peak value or the resonance RPM, etc.
#38
Next step up I could find is 100 G's. Too much?
I also like the analog outputs. You could go and capture a data stream, but it'll be around 3 kHz x 3 axes, and then you'd have to process the data, filter it, and extract the amplitudes and frequency (RPM). And log MAP too. With an analog output and a simple AM circuit, you get a simple 0-5V signal you connect to an aux input of an ECU.
I also like the analog outputs. You could go and capture a data stream, but it'll be around 3 kHz x 3 axes, and then you'd have to process the data, filter it, and extract the amplitudes and frequency (RPM). And log MAP too. With an analog output and a simple AM circuit, you get a simple 0-5V signal you connect to an aux input of an ECU.