Boosted folks with taller final drives... happy? - Miata Turbo Forum - Boost cars, acquire cats.

Welcome to Miataturbo.net   Members
 


Suspension, Brakes, Drivetrain discuss the wondrous effects of boost and your miata...

Reply
 
 
 
LinkBack Thread Tools Search this Thread
Old 10-30-2015, 12:37 PM   #1
Junior Member
Thread Starter
 
Join Date: Sep 2015
Location: Memphis, TN
Posts: 165
Total Cats: 19
Default Boosted folks with taller final drives... happy?

Gents,

For those of you pushing serious power, have you swapped for a taller ring/pinion set? For the NC's, the 6spd was the stronger transmission, but the gearing is so low as to be nearly pointless.

I'm strongly considering a swap to the 3.72 final drive. Sure, it's only ~10% different than stock, but that's enough to see 60mph in second gear and certainly enough to shave a few hundred RPM off cruise speed. Since my car will spend most of its life as a street bruiser, this seems like a no-brainer.

Thoughts? Flames? Abuse-the-n00b time?
albuquerquefx is offline   Reply With Quote
Old 10-30-2015, 01:56 PM   #2
Junior Member
iTrader: (5)
 
Join Date: Oct 2011
Location: San Diego, CA
Posts: 402
Total Cats: 21
Default

You have an NC? I'm not sure what final drive ratio you're coming from.
slmhofy is offline   Reply With Quote
Old 10-30-2015, 02:54 PM   #3
Junior Member
Thread Starter
 
Join Date: Sep 2015
Location: Memphis, TN
Posts: 165
Total Cats: 19
Default

All the 2009++ NC's have 4.10 final drive.
albuquerquefx is offline   Reply With Quote
Old 10-30-2015, 03:00 PM   #4
Senior Member
iTrader: (1)
 
Join Date: Dec 2010
Location: Farmington Hills, MI
Posts: 878
Total Cats: 93
Default

NC's came with 4.10's... which is 10% higher than 3.72.
acedeuce802 is offline   Reply With Quote
Old 10-30-2015, 03:07 PM   #5
Senior Member
 
Join Date: Jun 2015
Location: TAMPA, FL
Posts: 644
Total Cats: 27
Default

As a boosted guy with an NA 5 speed, 1 feels too short and you could probably space the others out a bit to compensate. When/if I upgrade to a 6 speed, I'll go to at least 3.6 or maybe 3.3 rear gears.
AlwaysBroken is offline   Reply With Quote
Old 10-30-2015, 04:03 PM   #6
Junior Member
Thread Starter
 
Join Date: Sep 2015
Location: Memphis, TN
Posts: 165
Total Cats: 19
Default

Not sure if I'd go so low as 3.3's, but good to hear someone's opinion. Also this thread demonstrates that I need to set up my autosignature...
albuquerquefx is offline   Reply With Quote
Old 10-30-2015, 04:41 PM   #7
Elite Member
iTrader: (15)
 
patsmx5's Avatar
 
Join Date: Aug 2007
Location: Houston, TX
Posts: 8,797
Total Cats: 248
Default

My setup at 18 PSI, 4.10's are shorter than I'd like with a 6 speed. I think a 3.636 gear would suit this car very well at the power it's making now. It's driveable with 4.10s, but you're shifting a lot. If (when) it has more power I think I'm going to install a numerically lower R&P gear.
patsmx5 is offline   Reply With Quote
Old 10-30-2015, 04:43 PM   #8
Senior Member
iTrader: (1)
 
Join Date: Apr 2011
Location: Columbia, SC
Posts: 1,342
Total Cats: 78
Default

Quote:
Originally Posted by patsmx5 View Post
My setup at 18 PSI, 4.10's are shorter than I'd like with a 6 speed. I think a 3.636 gear would suit this car very well at the power it's making now. It's driveable with 4.10s, but you're shifting a lot. If (when) it has more power I think I'm going to install a numerically lower R&P gear.
When did you last have a revlimiter lower than 8k though? lol
Schuyler is offline   Reply With Quote
Old 10-30-2015, 04:45 PM   #9
mkturbo.com
iTrader: (24)
 
shuiend's Avatar
 
Join Date: May 2006
Location: Charleston SC
Posts: 13,780
Total Cats: 1,106
Default

3.3 gears don't exist for NA/NB miatas.
shuiend is offline   Reply With Quote
Old 10-30-2015, 04:47 PM   #10
Senior Member
iTrader: (1)
 
Join Date: Apr 2011
Location: Columbia, SC
Posts: 1,342
Total Cats: 78
Default

Quote:
Originally Posted by shuiend View Post
3.3 gears don't exist for NA/NB miatas.
MiataRoadster definitely sold some for a while. Came from a diesel B2000 if I'm not mistaken.
Schuyler is offline   Reply With Quote
Old 10-30-2015, 04:47 PM   #11
Elite Member
iTrader: (15)
 
patsmx5's Avatar
 
Join Date: Aug 2007
Location: Houston, TX
Posts: 8,797
Total Cats: 248
Default

Quote:
Originally Posted by Schuyler View Post
When did you last have a revlimiter lower than 8k though? lol
Actually at 7.5K right now. Look at me trying to be nice to my engine!
patsmx5 is offline   Reply With Quote
Old 10-30-2015, 05:03 PM   #12
Junior Member
Thread Starter
 
Join Date: Sep 2015
Location: Memphis, TN
Posts: 165
Total Cats: 19
Default

Yeah, the 7500RPM redline in the NC MkII and later helps a little bit. Looks like the 3.72 might be a good way to go.
albuquerquefx is offline   Reply With Quote
Old 10-30-2015, 05:15 PM   #13
I take big bites
iTrader: (1)
 
turbofan's Avatar
 
Join Date: Sep 2010
Location: Hurricane, UT
Posts: 6,926
Total Cats: 526
Default

I had a 4.10 with the MSM 6-speed. It was horrible.

Did the 3.63 over the winter. At just 230 whp I'm happy I did it. When I up the boost I will be even happier.

For people with NA/NB's, it'd be silly to do anything other than the Getrag. I see it this way: I had an MSM torsen, which is easily worth $700. I bought gears for $400 (which was a steal) = 1100. Cost me about $300 to install = $1400. And I now have a spare set of 4.10 gears (worth about $3).

Getrag swap is $1500, plus diff probably another $400 from what I've seen people buying them for = $1900. But then I have stronger axles, and I'm left with a full torsen swap (axles, driveshaft, and diff) to sell (worth about $800-1000, maybe more) making this course of action considerably cheaper than dropping the 3.6 in an existing pumpkin.

None of this applies to you. BUT this thread will come up in searches.

TL;DR... go with taller gears. Tell us what's available in the NC world.
turbofan is offline   Reply With Quote
Old 10-30-2015, 05:18 PM   #14
mkturbo.com
iTrader: (24)
 
shuiend's Avatar
 
Join Date: May 2006
Location: Charleston SC
Posts: 13,780
Total Cats: 1,106
Default

Quote:
Originally Posted by Schuyler View Post
MiataRoadster definitely sold some for a while. Came from a diesel B2000 if I'm not mistaken.
The one that came in the B2000 does not fit in the miata diff, [email protected] found one and posted about it on the locost7 forums, here is the thread. MR or one of the other vendors tried to get a group buy going to get them made. It never happened though due to cost and quality issues.
shuiend is offline   Reply With Quote
Old 10-30-2015, 06:05 PM   #15
Moderator
iTrader: (11)
 
sixshooter's Avatar
 
Join Date: Nov 2008
Location: Tampa, Florida
Posts: 15,680
Total Cats: 1,561
Default

Just swapped from 5speed 4.10 to 6speed 3.63 and it is a fine combo. The first 5 gears are similar in ratio to previous but there is about a 300rpm drop in top gear at 80mph versus prior setup. My speedo is off now but I can fix that with a Revlimiter adjusted gauge face.
sixshooter is offline   Reply With Quote
Old 10-30-2015, 07:38 PM   #16
Junior Member
iTrader: (5)
 
Join Date: Oct 2011
Location: San Diego, CA
Posts: 402
Total Cats: 21
Default

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.
slmhofy is offline   Reply With Quote
Old 10-30-2015, 08:48 PM   #17
Elite Member
 
Join Date: Jul 2005
Posts: 6,454
Total Cats: 80
Default

I dearly miss the ratios of my 5 spd with 3.9. Even at 220 whp. The 6 sp with 3.9 sux, and I upgraded to 270 whp.
I drove a turboed Focus with ratios close to a miata 6sp + 3.3 and it very very nice.

The above is all about street driving.
JasonC SBB is offline   Reply With Quote
Old 10-30-2015, 08:52 PM   #18
Murderator
iTrader: (76)
 
18psi's Avatar
 
Join Date: Apr 2008
Posts: 36,196
Total Cats: 2,584
Default

street bruiser means you want them as long as possible. so as low as you can go on the fd
over 300 the 6sp+3.6 can light up 1st at ease, 2nd with ease, and 3rd depending on temp and tires

I guess you should also define what "serious power" is to you
Many of us very different perceptions on power
18psi is offline   Reply With Quote
Old 10-30-2015, 09:10 PM   #19
Junior Member
Thread Starter
 
Join Date: Sep 2015
Location: Memphis, TN
Posts: 165
Total Cats: 19
Default

Quote:
Originally Posted by 18psi View Post
street bruiser means you want them as long as possible. so as low as you can go on the fd
over 300 the 6sp+3.6 can light up 1st at ease, 2nd with ease, and 3rd depending on temp and tires

I guess you should also define what "serious power" is to you
Many of us very different perceptions on power
Serious power in my case will be 350-ish at the tires and a wet weight of about 2550lbs.
albuquerquefx is offline   Reply With Quote
Old 10-31-2015, 04:30 PM   #20
Senior Member
 
Join Date: Jun 2015
Location: TAMPA, FL
Posts: 644
Total Cats: 27
Default

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?

Last edited by AlwaysBroken; 10-31-2015 at 04:44 PM.
AlwaysBroken is offline   Reply With Quote
 
 
Reply

Related Topics
Thread Thread Starter Forum Replies Last Post
Turbo ND? Cool car Corky Bell Prefabbed Turbo Kits 23 02-11-2016 02:42 PM
Ok flame me but idle question 90 Turbo MEGAsquirt 11 11-16-2015 08:13 PM
My Flyin' Miata v-maxx review from track records to cruising with my gal blkmkiii Suspension, Brakes, Drivetrain 15 11-05-2015 11:58 AM
AFRs read rich and car bogs on acceleration Chiburbian MEGAsquirt 6 10-27-2015 03:27 PM
Anyone in the Sacramento, CA area have storage space? miata, tools, one set of tires thumpetto007 General Miata Chat 2 10-26-2015 01:58 AM


Tags
nc boost ring pinion n00b

Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



All times are GMT -4. The time now is 09:21 AM.