What's the highest rear end ratio availible for our cars? - Miata Turbo Forum - Boost cars, acquire cats.

Welcome to Miataturbo.net   Members
 


General Miata Chat A place to talk about anything Miata

Reply
 
 
 
LinkBack Thread Tools
Old 08-08-2010, 12:18 AM   #1
Want fries with that?
Thread Starter
iTrader: (3)
 
Join Date: Oct 2009
Location: Twin Cities, Minnesota
Posts: 2,023
Total Cats: -1
Default What's the highest rear end ratio availible for our cars?

So I've been pondering about this for a while... All the calculators tell me the top speed for each gear in our Miatas, yadda yadda.

Mine are... Different. From both 4.10 and 4.30.

Top speed of mine (GPS confirmed) are:

1st: ~30
2nd: ~50
3rd: 80 (Almost exactly)
4th: 100 (Again, almost exactly)
5th: Dunno, haven't got it there yet.

Calculators and even stuff from m.net show the top speeds of each gear to be higher, and significantly higher when you get into 3rd and 4th.

Sorry if this is a retarded thread, if I'm missing something someone please tell me.

Any thoughts?

EDIT: I'm on stock tires (185-60-14). '96, so it should have a 4.10.
rider384 is offline   Reply With Quote
Old 08-08-2010, 12:43 AM   #2
Boost Pope
iTrader: (8)
 
Joe Perez's Avatar
 
Join Date: Sep 2005
Location: Chicago (Over two miles from Wrigley Field. Fuck the Cubs. Fuck them in their smarmy goat-hole.)
Posts: 26,315
Total Cats: 1,913
Default

A 3.9 R&P was standard with all 6-speed equipped Miatas. Apart from 4.10 and 4.30, that's the only other ratio that was stock on a Miata in the US.

3.636 R&Ps were never standard on the Miata, but were found on all '79-'82 Mazda 626s, and are available from Mazdacomp. They are not particularly common, but some folks do retrofit them. (I've got a set sitting on the shelf.)

A more comprehensive listing: http://solomiata.com/RingandPinion.html

Which tires are you running, specifically?
Joe Perez is offline   Reply With Quote
Old 08-08-2010, 01:32 AM   #3
Want fries with that?
Thread Starter
iTrader: (3)
 
Join Date: Oct 2009
Location: Twin Cities, Minnesota
Posts: 2,023
Total Cats: -1
Default

Quote:
Originally Posted by Joe Perez View Post
A 3.9 R&P was standard with all 6-speed equipped Miatas. Apart from 4.10 and 4.30, that's the only other ratio that was stock on a Miata in the US.

3.636 R&Ps were never standard on the Miata, but were found on all '79-'82 Mazda 626s, and are available from Mazdacomp. They are not particularly common, but some folks do retrofit them. (I've got a set sitting on the shelf.)

A more comprehensive listing: http://solomiata.com/RingandPinion.html

Which tires are you running, specifically?
Would the 4.44 truck ratio fit in the Miata diff housing? 'Cause I put in all the numbers with that and everything is damn near exactly what I'm getting.

Tires are Altimax HP all-seasons in 185-60-14.
rider384 is offline   Reply With Quote
Old 08-08-2010, 02:31 AM   #4
Boost Pope
iTrader: (8)
 
Joe Perez's Avatar
 
Join Date: Sep 2005
Location: Chicago (Over two miles from Wrigley Field. Fuck the Cubs. Fuck them in their smarmy goat-hole.)
Posts: 26,315
Total Cats: 1,913
Default

So, here's the bad news. When I run the numbers for your quoted top speeds and tire, I get an RPM spread of roughly 750 highest to lowest, assuming a 22.7" tire and a 4.10 R&P.

That's more than 10% measurement error.

If this is really killing you, jack up the rear end, mark the tires with chalk, put the transmission into 4th (which is 1:1), and spin the crank over 4.1 times by hand.

Or just have a drink and assume that some fool didn't decide to tear apart the diff in your car and install a rock-crawler gearset into it.
Joe Perez is offline   Reply With Quote
Old 08-08-2010, 02:34 AM   #5
Want fries with that?
Thread Starter
iTrader: (3)
 
Join Date: Oct 2009
Location: Twin Cities, Minnesota
Posts: 2,023
Total Cats: -1
Default

Just Forza 3'd my car, once with a 4.10 and once with a 4.44. The 4.44 was DEAD ON what my car does. Exactly. 100%. And yes, I know that Forza is over 9,000% accurate.

So, ITT: ****.
rider384 is offline   Reply With Quote
Old 08-08-2010, 03:43 AM   #6
Elite Member
iTrader: (1)
 
NA6C-Guy's Avatar
 
Join Date: Feb 2008
Location: Birmingham Alabama
Posts: 8,038
Total Cats: 43
Default

Why a 4.44 and not a 4.3? I bet it's 4.3
NA6C-Guy is offline   Reply With Quote
Old 08-08-2010, 03:47 AM   #7
Murderator
iTrader: (76)
 
18psi's Avatar
 
Join Date: Apr 2008
Posts: 36,165
Total Cats: 2,573
Default

are you hitting the limiter in each gear?
could be your tacho is off and reading higher and you're short shifting?
18psi is offline   Reply With Quote
Old 08-08-2010, 04:20 AM   #8
Junior Member
iTrader: (2)
 
Join Date: Nov 2006
Location: N/A
Posts: 360
Total Cats: 0
Default

Quote:
Originally Posted by NA6C-Guy View Post
Why a 4.44 and not a 4.3? I bet it's 4.3
this
mikeflys1 is offline   Reply With Quote
Old 08-08-2010, 11:34 AM   #9
Want fries with that?
Thread Starter
iTrader: (3)
 
Join Date: Oct 2009
Location: Twin Cities, Minnesota
Posts: 2,023
Total Cats: -1
Default

It's not a 4.3. 4.3 still reads too high in each gear. By a significant amount.

I could be short shifting. I'll take a log and see.

EDIT: Hmm, very possible it's a 4.3 I guess. I'll double check.
rider384 is offline   Reply With Quote
Old 08-08-2010, 11:48 AM   #10
Elite Member
iTrader: (24)
 
chriscar's Avatar
 
Join Date: Dec 2007
Location: Carrollton TX
Posts: 1,702
Total Cats: 13
Default

Take your readings at 3500 rpm for each gear and calculate from there. This way you don't need to bang the rev limiter, and your speedo error will be lower.
chriscar is offline   Reply With Quote
Old 08-08-2010, 12:01 PM   #11
Elite Member
iTrader: (2)
 
fooger03's Avatar
 
Join Date: Jan 2009
Location: Columbus, OH
Posts: 4,132
Total Cats: 187
Default

My '94 with 4.10 would hit the rev limiter at about 110mph in 4th gear way back when it was stock.
fooger03 is offline   Reply With Quote
Old 08-08-2010, 12:21 PM   #12
Junior Member
 
Join Date: Mar 2009
Location: maine
Posts: 224
Total Cats: -1
Default

http://cgi.ebay.com/ebaymotors/Honda...Q5fAccessories
i don't know if this has been tried yet. but i'm told the rear carrier in the s2000 is the same as he mazda speed miata and the mazda speed miata is interchangable. This one is made by mazda and does fit he s2000 so it might work. mazda designed that diff for the honda as well.
94blackmx5 is offline   Reply With Quote
Old 08-08-2010, 12:42 PM   #13
Elite Member
iTrader: (12)
 
Join Date: Aug 2006
Location: Central-ish VA
Posts: 4,449
Total Cats: 16
Default

Mazdacomp made a 4.8 also. I bought an open diff one time that came with one.
neogenesis2004 is offline   Reply With Quote
Old 08-08-2010, 01:00 PM   #14
AFM Crusader
iTrader: (18)
 
olderguy's Avatar
 
Join Date: Oct 2004
Location: Wayne, NJ
Posts: 4,437
Total Cats: 84
Default

Speedometers are very inaccurate. Check against a GPS before using it to calculate ratios.

My 1991 with a 4:3 speedometer became extremely accurate when I put in a 4:1 torsen, but then my odometer is now off
olderguy is offline   Reply With Quote
Old 08-08-2010, 01:10 PM   #15
Boost Pope
iTrader: (8)
 
Joe Perez's Avatar
 
Join Date: Sep 2005
Location: Chicago (Over two miles from Wrigley Field. Fuck the Cubs. Fuck them in their smarmy goat-hole.)
Posts: 26,315
Total Cats: 1,913
Default

Well, he says in the first post that he did use a GPS, though my experience mirror's Olderguy's- when I installed a 4.10 into my '92, without changing the speedo pickup gear, the speedometer went from being quite optimistic to being accurate to within about a needlewidth at 70 (again GPS-verified.)

And, as Chriscar suggests, so do I concur- with an addendum: the stock tachometer isn't exactly NIST-traceable either. You'll want to reference your logger to get an accurate RPM indication.


.....Or, just do what I said in the first place and measure it directly. In fact, you don't even need to muck about with the engine and tranny now that I'm thinking more clearly. Put it in neutral and just rotate the propshaft by hand while observing a reference mark on the diff input flange.
Joe Perez is offline   Reply With Quote
Old 08-08-2010, 03:31 PM   #16
Elite Member
iTrader: (12)
 
Join Date: Apr 2008
Location: Springfield IL
Posts: 2,750
Total Cats: 24
Default

Quote:
Originally Posted by Joe Perez View Post
And, as Chriscar suggests, so do I concur- with an addendum: the stock tachometer isn't exactly NIST-traceable either. You'll want to reference your logger to get an accurate RPM indication.
x2 on that!

With a 7400-7600rpm limiter, my needle used to run WELL past 8k. Now with a 6400rpm limiter, it went to mid 7's before smacking the limiter
chpmnsws6 is offline   Reply With Quote
Old 08-08-2010, 05:35 PM   #17
Junior Member
 
Join Date: Mar 2009
Location: maine
Posts: 224
Total Cats: -1
Default

Quote:
Originally Posted by neogenesis2004 View Post
Mazdacomp made a 4.8 also. I bought an open diff one time that came with one.
from a bit more research i think this is actually the factory ring & pinion from the RX8
94blackmx5 is offline   Reply With Quote
Old 08-08-2010, 09:02 PM   #18
Elite Member
iTrader: (12)
 
Join Date: Aug 2006
Location: Central-ish VA
Posts: 4,449
Total Cats: 16
Default

Seeing as it was out WAY before the RX8 was even on the market, I'd say you're wrong.
neogenesis2004 is offline   Reply With Quote
Old 08-08-2010, 10:00 PM   #19
Elite Member
iTrader: (1)
 
NA6C-Guy's Avatar
 
Join Date: Feb 2008
Location: Birmingham Alabama
Posts: 8,038
Total Cats: 43
Default

Again I say, I bet $20 it's just a 4.3. No way a tack is accurate enough to tell a 4.3 from a 4.44, plus there is a very slim chance it is a 4.44 and not a 4.3, so I'm going with a logical assumption that it's a 4.3.

EDIT: I see you are saying these speeds are GPS confirmed? What is the history on the car. I just have a hard time believing the gears would have been changed to a less standard one than the 4.1 or 4.3, like a 4.44 or 4.8.

Your top speeds also look strange. What other Mazda 5 speeds fit the Miata, or what are the chances it's a modified trans using some other gears? Mostly 3rd gear looks too low to match the others.
NA6C-Guy is offline   Reply With Quote
Old 08-08-2010, 11:06 PM   #20
Junior Member
 
Join Date: Mar 2009
Location: maine
Posts: 224
Total Cats: -1
Default

Quote:
Originally Posted by neogenesis2004 View Post
Seeing as it was out WAY before the RX8 was even on the market, I'd say you're wrong.
what does that have to do with my statment? How would you say i was wrong?

The 6spd rx8 comes with a 4.77 ring and pinion. i never said anything about who released what first.
94blackmx5 is offline   Reply With Quote
 
 
Reply

Related Topics
Thread Thread Starter Forum Replies Last Post
[CT] 1999 Mazda Miata 10th Anniversary Edition - $5800 Jike Spingleton Cars for sale/trade 3 09-20-2016 05:33 PM
Twitchy car (tail happy problem) bigben Race Prep 16 09-11-2015 04:41 PM
Project DDoS: '99 "Budget" boost build ProjectDDoS Build Threads 1 09-09-2015 02:52 PM
ME221 Now has Autotune and Long Term Fuel Trim Tables Motorsport-Electronics ECUs and Tuning 0 09-05-2015 09:02 AM


Thread Tools

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 02:01 AM.