[QUOTE=RGlbk,Apr 3 2007, 05:01 PM] Ok, Ok!

I believe all of you have very valid points.

There is car/human interface and so it would be unfair to blame just the car.

BTW, the car crunches in the 1>2 and 2>3 at low rpm shifts as well. Even after the fluid has warmed up.

I am thinking of purchasing the Competition Clutch Flywheel which weighs 11 lbs.. So that mght help!

 

I should add that the shift RPM will affect rev matching delay as well. At higher RPMs, the engine's rate of deceleration will be higher due to more friction.

 

One problem with the car is that the shifter throws are so short that on a 1-2 shift most drivers shift too quickly. You need to hit the clutch-deep breath- shift to 2nd. I think my lighter flywheel helps as well, as the rpms drop more quickly.

 

I think forced shifts are more a function of excessive force being applied to the shifter than they are a function of short throws. A shorter throw actually provides less leverage for forcing the shifts. The RPSS I have in my car has a slightly shorter throw than the stock shifter, and requires slightly more pressure for a given shifting speed, but it also presents more resistance, and it certainly doesn't make the car shift any faster. I'd really rather have the improved feel of the billet shifter without the shorter throw, but that's not an option.

What the short throws of the stock shifter (or the RPSS) do is make it a lot easier to miss a shift. Our Miata has much longer throws, and it's almost impossible to engage second instead of fifth accidently. We've had the Miata since 1991 and I've never missed a shift in the car. Can't say the same about the S2000 though. I find that the S2000 shifter is more enjoyable, but also more error prone.

Personally, I love the short throws, even if I have missed a couple shifts. That's my fault, not the fault of the car.

 

Good point. Shifting an AP1 from first to second a 4,500 RPM takes a lot longer than shifting it from first to second at red line. The same shift at 3,000 RPM takes even longer. Same thing has to apply to the AP2. Grinds come when the timing is off, and you can get a grind from shifting too slowly just as easily as shifting too quickly. In my case, I'm actually more apt to blow a shift and get a little crunch when I'm short shifting, because when I'm short shifting I'm taking it easy and not always totally focused on the driving task. I don't recall ever getting a crunch when shifting at red line (though I have managed to totally miss shift a few times).

 

A lighter flywheel speeds rev matching, making smooth shifting faster.

 

True, and the situation for people with used cars is even worse; If you bought the car used, and are getting a crunch, you don't have any way to know for sure whether it's due to previous abuse or something you're doing yourself. With a car that has had several owners I suspect the odds of the transmission having been abused goes way up.

Being the grinch is a dirty job, but somebody's got to do it.

[QUOTE=slipstream444,Apr 4 2007, 04:51 AM]Too many people get frustrated with their cars the first time they screw-up a shift, and blame their mistake(s) on the machine.

 

[QUOTE=RED MX5,Apr 5 2007, 01:54 PM] A lighter flywheel speeds rev matching, making smooth shifting faster.

 

^
which lighweight flywheel do you use?

how is ACT fw and ACT pp combo?

 

So here is a thought!

In order for the Synchros to really do there job, you want the input shaft turning at the same rate as the output shaft for the gear you are going to select. Rev matching as some of you call it. Or, you can even double clutch to get the input shaft to slow down which is in effect rev matching the input shaft with the output shaft for the gear selected.

So here is a thought!

Why would anyone want to use a MT Fluid that is lower in viscosity than the Honda MTF? It would seem that the lower viscosity would not slow down the input shaft as fast as a higher viscosity MT Fluid.

For example, Honda MTF is about a 10W-30 while GMSMFM is about a 10W-High 20W oil. So because the viscosity is less for the GMSMFM, the inut shaft will not slow at the same rate as it would with the Honda MTF.

Also, if you take into account that the GMSMFM is part synthetic, and therefore more slippery than the Honda MTF, the input shaft should slow down at an even slower rate!

In general, Synthetic oils reduce frictional drag right?

So what I am trying to say is, we maybe going the wrong way, rather than use a 10W-30, or the 10W-High20, why not use a 10W-40 weight oil? This shouuld increase the drag a little bit. Is it enough to increase the rate of the input shaft slowing down, I don't know, but in theory it should work.

Especially when the secondary shaft is basically immersed in the MT fluid and all the gears are in constant mesh.

So my vote would be to increase the viscosity of the MT Fluid to 10W-40 weight oil.

Perhaps, this is why some folks running redline MT-90 swear by it. MT-90 has a viscosity of 15.6 versus Redline MTL which has a viscosity of 10.6. So the viscosity is about 50% different at 100C!

I have to think this difference in viscosity is going to slow the gears down a little faster and therefore the input shaft. Thus the synchros will not have to work as hard to slow down the input shaft.

Any thoughts?