A question on counterweights..
#1
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A question on counterweights..
Ok, so this is a kind of random situation..
I have asked this question of individuals in the past but I didn't get a clear response. I am getting very close to sending my FD off to a shop to finish up getting her back on the road and I'm slightly concerned that my engine setup may not be fully compatible.
I'm running a streetported 13B-rew with an rx-8 e-shaft, 2mm superseals and S4 NA rotors that have been lightened, clearanced, and balanced. I went with the S4 NA rotors solely due to the thicker casting. Initially the plan was to use the S4 counterweights because of the S4 rotors, which I did along with the appropriate front stack. However, prior to my last engine suffering an untimely death I noticed that there was a decent amount of vibration at idle. My motor died due to oil starvation because the t-stat mounted to the motor worked itself loose and dumped all my oil on the highway. I think the vibration played a part in this. It was a bad way to end DGRR
Anyway! When my rotors were lightened they were brought down to almost an identical weight as the stock FD rotors, which leads to my question... Are the correct counterweights for an engine based on rotor weight or something different? If they're based on the weight of the rotors, as opposed to how the rotors are individually balanced, then choosing the correct counterweights would no longer depend on series once you get into aftermarket lightening, correct?
I want to ensure that I'm doing this correctly BEFORE I drop the motor into my car and have it towed off to the shop, it would be far easier for me to redo the front stack now, as opposed to once I'm paying shop time..
Thanks for humoring me and I'd love to hear peoples opinions and the basis for them!
Cheers,
Levi
I have asked this question of individuals in the past but I didn't get a clear response. I am getting very close to sending my FD off to a shop to finish up getting her back on the road and I'm slightly concerned that my engine setup may not be fully compatible.
I'm running a streetported 13B-rew with an rx-8 e-shaft, 2mm superseals and S4 NA rotors that have been lightened, clearanced, and balanced. I went with the S4 NA rotors solely due to the thicker casting. Initially the plan was to use the S4 counterweights because of the S4 rotors, which I did along with the appropriate front stack. However, prior to my last engine suffering an untimely death I noticed that there was a decent amount of vibration at idle. My motor died due to oil starvation because the t-stat mounted to the motor worked itself loose and dumped all my oil on the highway. I think the vibration played a part in this. It was a bad way to end DGRR
Anyway! When my rotors were lightened they were brought down to almost an identical weight as the stock FD rotors, which leads to my question... Are the correct counterweights for an engine based on rotor weight or something different? If they're based on the weight of the rotors, as opposed to how the rotors are individually balanced, then choosing the correct counterweights would no longer depend on series once you get into aftermarket lightening, correct?
I want to ensure that I'm doing this correctly BEFORE I drop the motor into my car and have it towed off to the shop, it would be far easier for me to redo the front stack now, as opposed to once I'm paying shop time..
Thanks for humoring me and I'd love to hear peoples opinions and the basis for them!
Cheers,
Levi
#2
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i'm under the impression that the S4 front CW doesn't fit under the FD front cover? easy to check!
since its not a factory assembly, you should balance it.
since its not a factory assembly, you should balance it.
#3
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I'm running a streetported 13B-rew with an rx-8 e-shaft, 2mm superseals and S4 NA rotors that have been lightened, clearanced, and balanced. I went with the S4 NA rotors solely due to the thicker casting. Initially the plan was to use the S4 counterweights because of the S4 rotors, which I did along with the appropriate front stack. However, prior to my last engine suffering an untimely death I noticed that there was a decent amount of vibration at idle. My motor died due to oil starvation because the t-stat mounted to the motor worked itself loose and dumped all my oil on the highway. I think the vibration played a part in this. It was a bad way to end DGRR
Anyway! When my rotors were lightened they were brought down to almost an identical weight as the stock FD rotors, which leads to my question... Are the correct counterweights for an engine based on rotor weight or something different? If they're based on the weight of the rotors, as opposed to how the rotors are individually balanced, then choosing the correct counterweights would no longer depend on series once you get into aftermarket lightening, correct?
Anyway! When my rotors were lightened they were brought down to almost an identical weight as the stock FD rotors, which leads to my question... Are the correct counterweights for an engine based on rotor weight or something different? If they're based on the weight of the rotors, as opposed to how the rotors are individually balanced, then choosing the correct counterweights would no longer depend on series once you get into aftermarket lightening, correct?
For reference, attached is the checklist from MazdaTrix that lists all the parts they would ask you to ship them if you wanted them to balance the entire rotating assembly. That's for a race motor and probably overkill for a street motor that won't rev much beyond 9K, but it gives you an idea of what all the spinny bits are.
Also, I agree with J9FD3S about getting the assembly balanced, since it isn't a factory setup anymore.
Last edited by Pete_89T2; 01-23-19 at 01:17 PM.
#4
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The assembly was definitely balanced, it's just been so long now that I can't remember if I sent the S4 counterweights off for the initial balancing or not.
I know right! The wife has finally graduated, I've gotten a grown-up job, and I've paid off all my reoccurring debt (minus my mortgage, which is manageable) and so now I can finally focus funds on getting the car running again BEFORE we have a brood of crotch-goblins.. So yeah, I'm going to strike while the iron is hot and I can still pull the guilt trip of "I paid for all your college, so let me prioritize my car now" to get permission from the wife...
Originally Posted by Pete
I'm no authority on this, but my understanding is you want to keep the whole rotating assembly balanced, so for a simple stock build, you'll just use the CW part that matches up with the series rotors being used (i.e., S4 with S4) and trust Mazda's engineers. BUT since you had your rotors lightened, when you say you had it "balanced" in that first paragraph above, were you referring to the whole rotating assembly (i.e., rotors, shaft, CW, etc.) or just the rotors? What actually got balanced when you had this job done? Anyway, since your lightened rotors weigh in close to the stock FD rotors, I'm guessing the FD CW would be the right one to use.
For reference, attached is the checklist from MazdaTrix that lists all the parts they would ask you to ship them if you wanted them to balance the entire rotating assembly. That's for a race motor and probably overkill for a street motor that won't rev much beyond 9K, but it gives you an idea of what all the spinny bits are.
Also, I agree with J9FD3S about getting the assembly balanced, since it isn't a factory setup anymore.
For reference, attached is the checklist from MazdaTrix that lists all the parts they would ask you to ship them if you wanted them to balance the entire rotating assembly. That's for a race motor and probably overkill for a street motor that won't rev much beyond 9K, but it gives you an idea of what all the spinny bits are.
Also, I agree with J9FD3S about getting the assembly balanced, since it isn't a factory setup anymore.
I think I'll just have to trust that I'm being hypersensitive and that everything is done correctly. If the balancing is off then I'll find out when we start the car because their will be a catastrophic failure which will make any errors self-evident.. At that point all the "hard" work will have been completed and stripping the motor down to correct the issues will be a straightforward task
#6
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From what I'm gathering it really doesn't matter, whatever CW's you send in to have the assembly balanced with will be modified to make it all work together. So in this situation I'm pretty much stuck with the S4 CWs and front stack, not because my rotors were originally from an S4 but because they are what were provided with the original balancing. If I had just sent in my FD CWs when I sent the rest of the rotating assembly in then I would need to keep using my FD counterweights for the S4 rotors.
Ultimately it should make little difference with regards to the engine being balanced, the main difference will now be in the front stack used.
At least this is how I'm now understanding it. I'd love to be corrected if I have it wrong though
#7
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Also, I should clarify: While I was talking with Chip yesterday he said that any vibration at idle or low rpm would likely be caused by something unrelated to the RA. Since the RA isn't rotating at a high enough speed at idle it wouldn't really cause vibrations.
I inferred that if it WAS out of balance enough to cause noticeable vibrations at idle then it would get progressively/significantly worse as the car is driving and run up the rev range.
I inferred that if it WAS out of balance enough to cause noticeable vibrations at idle then it would get progressively/significantly worse as the car is driving and run up the rev range.
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#8
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Also, I should clarify: While I was talking with Chip yesterday he said that any vibration at idle or low rpm would likely be caused by something unrelated to the RA. Since the RA isn't rotating at a high enough speed at idle it wouldn't really cause vibrations.
I inferred that if it WAS out of balance enough to cause noticeable vibrations at idle then it would get progressively/significantly worse as the car is driving and run up the rev range.
I inferred that if it WAS out of balance enough to cause noticeable vibrations at idle then it would get progressively/significantly worse as the car is driving and run up the rev range.
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its really easy to mill the front CW to use the bigger needle bearings, its probably a good idea to do it
#10
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I don't plan on going nuts and abusing the car in any sort of seriously competitive driving, so it'll most likely be fine with the front stack it has currently.
#11
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^That's all very true... Remember, your rotors spin at 1/3 the E-shaft RPMs, so at say 1K RPM idle on the tach, they are only spinning at 333.3 RPMs. Are you using stock or Mazda competition motor mounts, or something much stiffer (i.e., delrin mounts)? If it's something stiffer, I bet that's why the vibes were noticeable.
I'll be running the FFE engine mounts this go around, and I'm strongly tempted to get rid of my old tranny brace in favor of one of the ones that the guys at Banzai have put together (or just nothing extra at all!)
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