https://www.miataturbo.net/race-prep...7/#post1049820

 

Oh I must have missed the link.
That is a flat torque curve from 4500-8400 and the power is a climber

 

Awesome info. Amazing what you guys are doing to the BP motors.

 

Do these fully built engines rev out much smoother than stock miata engines?

I know sometimes some feel like they could vibrate to peices when nearing redline.

 

More power usually means more vibration. If you balance the entire reciprocating and rotating assemblies together (damper/crank/rods/pistons/flywheel/clutch), keep revs below 7000rpm, run stock cams, modest compression and OEM NB motor mounts with an NB2 engine block, JDM TB mass damper, USDM manifold brace.. you can make it a bit smoother than a stock NB2. You will not reach anything close to 200whp though. One or the other.

 

You lost me here. Never heard of that part before. Not sure why the throttle body would have a mass damper?

Lost my lower alternator bolt in a hundred miles of street driving when using /one/ MMR mount (since gone back to MS), so this gets my interest.

 

Solid MMR mounts make stuff fall off of Miatas. I suggest the 70D SuperMiata mounts. Stiff enough to keep the trans in place, not so stiff that the driver can't feel the front tires through the steering wheel and stuff does not fall off.

339 grams

 

I'd thought about the supermiata mounts, but it says 'not for street use.'

Are the 70D SuperMiata mounts worse than the MazdaComp for NVH?

 

I dont think I would daily them now as a 23 year old. They're fine for weekend trips and things like that. As an 18 year old I'd daily the **** out of them. At least on my car, below 3.5k rpm the cabin resonates, its nothing vibrating against anything else, its like the cabin is the cone of a speaker.

 

Have you driven the MazdaComp mounts to compare the two?

 

Not on the street and not for very long. I went from completely destroyed stockers that were separated and turning themselves into dust to AWR 70 duro units.

 

I don't find the MazdaComp objectionable on the street at all, except that they're still a bit sloppy. Thus the MMR experiment.

Definitely with solid diff mounts though. Right now I'm having major problems getting into third under load, and I was about to put in an order, so this is topical.

 

So...this mass damper...is this a possible solution for the failing TB shafts?

 

The TB shaft breaks due to stretching by jamming on the accelerator too hard. I am just guessing that the damper helps just a tad over stock by not making your fillings vibrate out of your skull.

 

So does the mass damper help/work on the Skunk2?

 

If you are crazy enough to run MMR solid mounts on the street, I assumed our 70D mounts would be a welcome respite.

No

Nope. Tested that theory.

Help what?

 

Yeah, the MMR came off. Quickly. MazdaComp is still sloppy, not bad with solid rear mounts.

Help with smoothness/stuff staying together on track.

IIRC, Andrew needs to tighten up the IM on Rover regularly, I don't believe that's a high rev engine? Not sure. Would like to avoid that kind of thing, so if I could attach a small weight to a Skunk2 throttle body to bring down vibes, that'd be awesome.

 

I remember spending a whole day fabricating a set of solid motor mounts. The motor ran for a total of five minutes before I pulled them off and threw them into a bucket.

 

So what causes the TB shaft to break? Poor metallurgy on the throttle shaft?

I am extremely curious since failure due to fatigue from tensile stress seems like a decent theory. Then again, IANAMS. (I am not a material scientist)

e: damn it, I am already thinking about how to set up a controlled experiment. Use a window motor to torque down on a pedal arm with a tact switch at the bottom to act as a counter for how many "hard stomps". I can't remember how the Arduino does it's numbering or if 8 bits will be big enough since fatigue cycles are measured in 10^n; however, the Arduino's PWM controls are perfect to control the motor.

 

Throttle shaft breakage - MX-5 Miata Forum

Vibration fractures a weak shaft design. Reduce vibration by not revving near 7000rpm and the problem vanishes.