Boosted folks with taller final drives... happy?
11-01-2015, 12:16 AM
#22
I've got the Getrag 3.28 swap in my car. And coming from the MSM 4.10 w/6 speed which I pretty much hated once I started making power; I absolutely LOVE it.
Running 20psi ~ 275whp, there's still enough power to smoke the RS3s in 1st if they're not warmed up, second feels a little long, but everything else is great.
Running 20psi ~ 275whp, there's still enough power to smoke the RS3s in 1st if they're not warmed up, second feels a little long, but everything else is great.
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11-01-2015, 10:03 PM
#26
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I've run a 6-speed with 4.10s, 3.909s, and 3.636s.
4.10s are ideal for track cars under 240whp or so. 3.909s work between 270 and 350whp, and north of 350whp, you want 3.636s for better traction in 3rd and 4th. 3.63s are too tall for ~270whp cars - 5th gear feels doggy on track with so much gear.
On the street, 3.636s are great, 3500rpm at 78mph, and you're never beating on the car in 5th on the street (or at least you shouldn't be), and the other gears are short enough that you don't feel like you NEED to downshift to go someplace.
I wouldn't mind a little more rev drop on the freeway with the 6sp/3.63s. A T5 box with G-Force's .75 overdrive will solve that, though.
4.10s are ideal for track cars under 240whp or so. 3.909s work between 270 and 350whp, and north of 350whp, you want 3.636s for better traction in 3rd and 4th. 3.63s are too tall for ~270whp cars - 5th gear feels doggy on track with so much gear.
On the street, 3.636s are great, 3500rpm at 78mph, and you're never beating on the car in 5th on the street (or at least you shouldn't be), and the other gears are short enough that you don't feel like you NEED to downshift to go someplace.
I wouldn't mind a little more rev drop on the freeway with the 6sp/3.63s. A T5 box with G-Force's .75 overdrive will solve that, though.
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11-01-2015, 11:03 PM
#27
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I think the main problem everyone is trying to solve here is that high power turbo miatas are incredibly slow off boost and incredibly fast on boost and the transition happens about the middle of the rpm band.
This means that pretty much every first gear that is short enough to not bog off the line will bounce off the rev limiter once boost hits and any first gear long enough to not spin will either bog or eat clutches trying to get off the line fast. If the miata had a flat torque curve from 1500 rpm to redline, everyone would just run 50 mph first gears and call it a day.
The best solution (short of going SC or v8) is probably to just run a shortish first gear and limit power until 2nd/3rd to prevent spin. How hard would it be to rig up a 1st/2nd gear sensor for the miata? Once you have that, lowering the boost would be easy.
edit- I suppose you could just derive gear from the speedo cable- ie, below 30mph turn off boost control or substitute a pulse width of your choosing (selectable with a dial on the dash?)
edit2- wait a second I just remembered the miata uses a cable rather than electronic speedo cable... so where is my ECU getting the car's speed from? Anyone remember where to get a speed signal on the miata for something like an arduino?
This means that pretty much every first gear that is short enough to not bog off the line will bounce off the rev limiter once boost hits and any first gear long enough to not spin will either bog or eat clutches trying to get off the line fast. If the miata had a flat torque curve from 1500 rpm to redline, everyone would just run 50 mph first gears and call it a day.
The best solution (short of going SC or v8) is probably to just run a shortish first gear and limit power until 2nd/3rd to prevent spin. How hard would it be to rig up a 1st/2nd gear sensor for the miata? Once you have that, lowering the boost would be easy.
edit- I suppose you could just derive gear from the speedo cable- ie, below 30mph turn off boost control or substitute a pulse width of your choosing (selectable with a dial on the dash?)
edit2- wait a second I just remembered the miata uses a cable rather than electronic speedo cable... so where is my ECU getting the car's speed from? Anyone remember where to get a speed signal on the miata for something like an arduino?
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11-02-2015, 11:38 AM
#28
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Also, why are the ONLY two options bog or bounce redline? Are we talking on the strip or the street? Because I'm reasonably confident that a turbocharged application can be reigned in with throttle management. Unless the pedal is pinned to the carpet, I can be reasonably sure of keeping it off the revlimiter.
The best solution for me is to stretch ALL the gears rather than invoke even more pain with electronic management that further removes me from the decision making. The only place I *might* consider electronic management is in 6th gear, and ONLY because the NC's 6th gear with ~350tq applied tends to rip off all the teeth. Since I have zero interest in EVER going for land-speed records, I have considered using some gear-aware EBC just to ensure I keep it low and slow in 6th.
Based on the other feedback in this thread, it looks like my head is in the right direction. The lowest I've found (native, factory option) for the NC is the 3.72 set, but I can also see other options either with replacement pumpkins or special kits to retrofit other R&P sets.
For what I'm trying to accomplish, the 3.7 is probably fine.
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09-16-2018, 11:31 PM
#29
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I'm awaiting shipment of Mfactorys 3.33 ring and pinion for my 2.4L ecotec x MSM 6mt setup. Car makes a lot more tq under 4k than probably most turbo miatas and really want to take advantage of that on the highway and any future forced induction plans. Won't get the gears installed till christmas time ish so you'll see me complaining about my 6mt x 4.10 setup for a while.
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09-17-2018, 04:40 AM
#30
Megasquirt has boost by gear built right in, NB has the speed sensor in the trans, NA gets it from the cluster.
i went from 3.9 to 3.63 with a 6 speed in my NB and it was a great move with ~250hp. 60mph in 2nd. The shift points were much better at summit point and mid Ohio and will keep me out of 6th gear now that I can get 135mph in 5th.
i went from 3.9 to 3.63 with a 6 speed in my NB and it was a great move with ~250hp. 60mph in 2nd. The shift points were much better at summit point and mid Ohio and will keep me out of 6th gear now that I can get 135mph in 5th.
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