Monk

iTrader: (3)

I was thinking this as well, but OP seems to be the type to overbuild things ( not a bad thing).

Savington

iTrader: (31)

It's nowhere near the truth, actually. Built Quaife boxes start at about $2500 for used boxes and ~$4k+ for brand new boxes including case modifications, synchros, forks, etc. You also assume that a built 5-speed is stronger than a stock 6-speed, and those of us who are following the gearbox thread in the Race Prep section know that to be false at this point.

OTOH, 6-speeds can be had for $600-800 depending on mileage. In no world is a built 5-speed "cheaper" than a 6-speed. The OP's desired power level (250whp) is well within the reliable limits of a 6-speed, and your opinion about the gear ratios is not one that is shared by very many people, especially in a motorsport application.

i lol'd IRL. M.net is not the place to be looking for advice on this sort of stuff

18psi

iTrader: (76)

m.net you're joking right?....right?

HMM, I wonder why FM would discontinue something? lol

I was being polite in that post. I didn't even get rude yet

Simply put: your claims are plain wrong. Way off. Not even close. So please stop spreading misinformation.

Mobius

iTrader: (2)

Nobody has been rude to you yet; you have actually been treated quite gently. You've been a member since June and you haven't figured out how this forum works yet?

You may not be in fact be a moron, but you are making factually incorrect, moronic statements. People that do so get banned quickly. Our moderators separate the wheat from the chaff and right now you're on the wrong side of that equation.

BadGT

Let me explain my train of thought and clarify a few things

When i said i can get a few 5 speeds for the price of a 6 speed i meant a few normal non - built 5 speeds

also when i said cheaper i was referring to doing that as apposed to possibly breaking 1 or 2 6 speeds

(can get the by the truck load at pick and save )

I assume with any used transmission, not just those used for racing most people will go through it post purchase and at least inspect it.

Why not just upgrade with internals and feel good about it. (again personal preference i have yet to read the post savington spoke of)

I am the type to way over build for the future so i avoid doing it again if i would like more power.

I found out after asking a few people FM discontinued the 5 speed upgrade kit due to people having unrealistic ideas about how much power the upgraded 5 speed could handle and they got complaints (is not actually confirmed by anyone working for FM)

Ill really have to read that thread after this im very interested. I helped a bit with the build up of a friends that is drag raced at our natural bridge track his has held up to hard launches for several years now. 1.8 @ 20~ psi does very well at our import night.

I also found out the photo i posted above was a 6 speed @ 272~ rwhp
Was used mainly for autocross


Yes i may prefer my methods and suggest them while others may suggest something else, that however does not mean i am attempting to mislead anyone just to be mean i am expressing my opinion based on my experiences. Which may or may not conform with what the masses consider standard.

Also i just preferred the 5 speed box, once again its a personal preference

paulw

I'll stick with the 5 speed oem box and see what happens. In sprinting we are never on high revs for long. The circuits are very technical. In my vauxhall engined racer I locked 5th gear out. 6 gears will be useless unless there is significant proof of them being stronger.

I will build a stronger box when I see if the 5 speed is a week point.

18psi

iTrader: (76)

You have a personal preference, cool, you're entitled to it, even if it may be extremely misguided and outside the norm. Tons of people do all sorts of weird things.

But that's a far cry from your original post, for which you got a bit of heat.

The gearing on the 6 is better for track. The 6 is significantly stronger. And when you say you can get a bunch of 5's for the price of one 6 you obviously don't consider the time or the effort swapping the trans. You're also ignoring the fact that there are a significant amount of broken built 5 speeds.

Search around, and you'll quickly realize why we have so many transmission discussions around here, and why everyone above 300whp is really itching for the "solution" that would work reliably and not break the bank. We've a lot of really long discussions about it here. And they are done by people making enough power and going fast enough on track to actually have something to say, not some m.net wine-n-cheezers or clubricer stancebroz

BadGT

Ill agree i should have worded it better. Ill take caution to do so in the future cheers

Mobius

iTrader: (2)

Well it will be interesting to see if the 5 speed survives for any length of time. If you really can get that chassis down to where it weighs less than Lewis Hamilton's underwear, maybe it will.

Savington

iTrader: (31)

1. there is significant proof of 6-speeds being stronger
2. gear ratios don't work like you think they do
3. 6-speeds are faster

BadGT

Just leave this here for the OP

All below values based on tire size 205/50/15 yours may vary slightly
All below values are based on the final drive of 4.10

5 Speed manual 1990-12
gear ratio mph @7200 rpm
1st 3.163 38.1
2nd 1.888 63.8
3rd 1.333 90.4
4th 1.000 120.5
5th .814 148.1
6th NA NA
-- -- --
6 Speed Manual 1990-05
gear ratio mph @7200 rpm
1st 3.760 32.1
2nd 2.269 53.1
3rd 1.645 73.3
4th 1.257 95.9
5th 1.000 120.5
6th .843 143.0

Stock rear end ratios for North America
1990-93 5-speed 4.30
1994-97 5-speed 4.10
1999-05 5-speed 4.30
1999-03 6-speed 3.909
2004-05 6-speed 4.10
2006- all trans 4.10

Ill attempt to explain as best as i can gear ratios and how they work for the op


Lets take a look at the 5 speed vs the 6 speed in 1st gear

5 speed

1st 3.163 38.1

6 speed

1st 3.760 32.1

now with the 5 speed the gear ratio is 3.163 this means for every 3.163 turns of the engine we are getting one turn at the rear end multiplying torque.

Now with the 6 speed its 3.760 so that means for every 3.760 turns of the engine we are getting 1 turn at the rear end

(the turns are actually measured at the output shaft of the trans i am just trying to make it easier to understand)

Now this means for several reasons the 6 speed is quicker

More torque multiplication and for turbo cars more time spent in the higher rpm range which is good for boost making more power.

Now you will find on almost every car forum or at any car meet guys arguing
I like the 6 speed its quicker i like the 5 speed its quicker!
This is because some people feel they would rather shift less and have a bit more room to use the boost they have made before shifting and having to start building boost again. The solution for this is almost always a upgraded head (valves, springs w/e) to allow you to safely rev higher.

Now lets look at the 4th gear of the 5 speed, and the 5th gear of the 6 speed.

These ratios are

5 speed 4th 1.000 120.5

6 speed 5th 1.000 120.5

notice the mph are the exact same? This is because its a 1:1 ratio meaning for everyone 1 turn of the engine (or transmission input shaft) you get 1 turn of the rear end (the output shaft)


Now lets look at the 5th gear of the 5 speed and 6th gear of the 6 speed

5 speed 5th .814 148.1
6 speed 6th .843 143.0

Now notice we have less than 1:1

The 5 speed 5th .814 148.1 meaning for every .814 turns of the engine (input shaft) we get 1 full turn of the rear end (output shaft) this is what is called an overdrive as the output shaft is spinning faster than the input shaft.


I hope i explained this properly and clearly.


adding some image below to help clarify the explanation.

18psi

iTrader: (76)

Don't forget though that the rear end fd changes those posted speeds quite a bit and the 5 and 6 come with different ones, not the same one

3.9 vs 4.3 is quite different

BadGT

Thanks cleaned up post to state that all values are based on the 4.10

paulw

Bloody hell guys what have i started

I'll chuck a bit more fuel on the fire then because we run very soft Avon slick tyres in sprinting and hill climbing and the best choice of tyres is in 13" that is what i run could BadGT scale the ratio to suit? I run 7.5/20/13

So a six speed would fit?

Paul

BadGT

Sure i can to properly convert it would you like the 4.10 rear end conversations to i can accurately get you the values?

And yes the 6 speed is very easy to swap in out in my opinion

18psi

iTrader: (76)

I used to play with the gearing calculator FM has online for hours.

6sp+3.6fd=purrfect

paulw

That would be cool cheers

The 6 speeds are quite expensive over here.

Paul

18psi

iTrader: (76)

here:
Flyin' Miata : Technical info : Gearing calculator

BadGT

thats even better

NiklasFalk

iTrader: (1)

6sp the same length as a 5sp, and the outer dimensions are not that much different either, swapping between then is easy.

Use a gear calc to find what total ratio you need at the fastest place for the hills/sprints you will run (rev and tire dependent).
Then use a 6sp and the highest final drive you can use. The higher you go in the gears the smaller the drop between gears.

In my case a 6sp with my 4.875 would be ideal (I don't need to go faster).

And there are 4.44, 4.77, 4.875 and 5.11 available beyond the Miata OEM list (which include 3.636 if you include EU and AUS markets).

Having two different rear ends to choose from would be vise, and better spend effort than doing anything more to a 6sp than changing oil. Even having OSG diffs in both may not change that judgement.