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#1
Kyle Freiheit

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Hey guys,

   I am getting rid of a bunch miata stuff and I have no idea what some of this stuff is worth. I was hoping the miata collective might point me in the direction of what this stuff is worth these days.

 

As some people are moving to the 1.8 or cusco diff its hard to gauge the worth of mazda comp diffs.

 

I have a :

1) 4.3 with mazdacomp that is less than 6 races old 

2) 4.88($500 brand new ring gear from mazdamotorsports) and a brand new mazdacomp, all set up with about 2 hrs on it.

 

 

What say you?

 

Thanks

 

Kyle



#2
Tom Hampton

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The mazdacomp is basically worthless.  But, I'll be happy to take it off your hands, if you pay for shipping....

 

:devil:


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#3
Kyle Freiheit

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#4
Blake Thompson

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There are faster, legal, options for the NA6.  Also there are better and more plentiful options for roughly the same asking price.  

 

I think if you got $300 out of it you'd be a thief.


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#5
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Interesting point referencing the MazdaComp L/S, rarley seems to be any for sale.  Recently found one gearless at $275.00 for a racing friend.


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#6
Blake Thompson

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Interesting point referencing the MazdaComp L/S, rarley seems to be any for sale.  Recently found one gearless at $275.00 for a racing friend.

saini is trying to re home one.  The whole reason they opened up the rule book is they're out of production and ticking time bombs.


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#7
Kyle Freiheit

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Blake,

I have heard the ticking time bomb comment before but have never had a failure with any mazdacomp diff.

To be honest, I know people had failures early on, but once they got set up right were very reliable. I know tons of people that have ran for 7-8 years on the same mazdacomp, Many of those never even checked it in that time.

 

Kyle



#8
Bench Racer

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saini is trying to re home one.  The whole reason they opened up the rule book is they're out of production and ticking time bombs.

I understand your input ^, bought a spare several years ago and have set up/assembly complete for when required. Knock on wood.

 

My comment, "rarely seems to be any for sale" referenced for all the Torsen's installed, where are the MazdaComp L/S, collecting dust, the MazdaComp it's self is pretty bullet proof.

 

What does "re home one" mean?


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#9
Blake Thompson

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he has one for sale.


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#10
Bench Racer

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he has one for sale.

For how many dollars and where is it located?


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#11
Kyle Freiheit

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Interesting info for sure. I also happen to have a full set of rebuild clutch discs for a mazdacomp too. I have way to much stuff. Off to ebay or craigslist!



#12
Blake Thompson

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Saini says his is sold and he got $350 so there's an answer for you Kyle.


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#13
LarryKing

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OMG, Saini is a thief!
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#14
Steve Scheifler

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I recently paid significantly more for a complete diff with the old MC unit which had just been gone through. We've broken a couple ring & pinions but not the LSD units, so to me they have represented decent value and I bought this one for the spare car.

I am curious to hear about the real-world benefits of the new Cusco units from someone who has used both. In theory they can be better, but how significant and what is required to achieve that benefit?
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#15
Ron Alan

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To say a mazdacomp is worthless when the replacement is $1200 is ridiculous. The ticking time bomb is a myth IMO. The ring and pinion is the weak link...as it is with the Cusco! There is a classified section here if you want to put up your stuff and test the market. Otherwise Google and do your research...price accordingly based on how quickly you want to sell!

Ron

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#16
SaulSpeedwell

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Wow.  Aside from humorous comments from smartass old-timers, this is potentially a very misleading thread for new folks, in my opinion.

 

The (discontinued) MazdaComp LSD for 1.6s is a great unit and near-bulletproof in anything with Miata/RX-7 levels of power.  I'll buy them for $375 ALL DAY LONG, feel free to email me if you have one on hand that you will sell for $375!  I tell customers and friends to buy a Comp LSD unit (installed in a carrier) from folks they trust for $650 minimum! 

 

My opinion, as I've told many people privately:  A full 1.6 carrier with a MazdaComp LSD ready to go is worth as much as $950, if it has been "looked over" by a reputable builder, or you are buying it from someone you trust and they are giving you a 4-weekend "gentleman's warranty".  

 

Any reliability issues with 1.6 diffs are due to the "undersized" ring and pinion gear and, to a much *larger* extent, BAD setups!  These have nothing to do with the MazdaComp LSD itself - in fact, the MazdaComp LSD will normally survive multiple explosions of rings and pinions, because the ring and pinion "shrapnel" is large and the Comp LSD clearances are very small.

 

For every car and driver we have A-B test data on, the 1.6 diff (whether MazdaComp or Cusco) is absolutely significantly faster than the 1.8 Torsen diff - the issue is setting up the 1.6 ring and pinion to survive, which some builders (and probably all builders that don't specialize in SM) have yet to figure out.  This is very old news, unless you don't know who Mike Backus or Jarrod Igou are  ... I think those guys blew up 1.6 diffs every 1-2 weekends!

 

(Hint:  Do NOT set up a used 1.6 diff per the factory service manual ... talk to a builder that caters to SM and knows what they are doing!)


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#17
SaulSpeedwell

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I recently paid significantly more for a complete diff with the old MC unit which had just been gone through. We've broken a couple ring & pinions but not the LSD units, so to me they have represented decent value and I bought this one for the spare car.

I am curious to hear about the real-world benefits of the new Cusco units from someone who has used both. In theory they can be better, but how significant and what is required to achieve that benefit?

 

I work on a lot of MazdaComps and Cuscos both.  To be completely frank, a used MazdaComp is the better bargain - because both the MazdaComp and the Cusco need "blueprinted" in order to be optimal for a low-powered car like Spec Miata.

 

It has been discussed several times over several years here, but LSDs are somewhat akin to go-karts with solid axles - the power to overcome the "breakaway torque" can only come from one place - the motor.  Have you ever pushed a solid axle go-kart with the steering wheel turned?  That's what your SM $6K motor "feels" when you turn the wheel and you have an LSD that has too much breakaway torque.

 

If you have 20 ft-lbs of breakaway torque?  Well, 20 ft-lbs divided by 4.3 rear end ratio is 4.65 ft-lbs (crankshaft) in 4th gear (1:1).. so that is 4.6 ft-lbs lost to the friction Gods any time you are not going absolutely perfectly straight. 

 

A properly blueprinted Cusco will (in theory) be faster than a MazdaComp, because the MazdaComp is fundamentally a 2-way differential (it drags anytime the outside and inside wheelspeeds are not exactly the same) and the Cusco can be set up as 1, 1.5, or 2-way.  If set up perfectly, a Cusco should never "drag" except when you need it to be "locking up".

 

Still, for most drivers, there is little reason to choose the Cusco over the MazdaComp for a SPEC MIATA - when properly blueprinted, a MazdaComp should cost you around 1.5 ft-lb of drag, and only when you aren't letting the car run "straight and free".  At power levels above SM, a Cusco should be considered mandatory.  The MazdaComp can't handle much more than 140 RWHP in terms of lockup capability. 

 


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#18
speedengineer

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I work on a lot of MazdaComps and Cuscos both.  To be completely frank, a used MazdaComp is the better bargain - because both the MazdaComp and the Cusco need "blueprinted" in order to be optimal for a low-powered car like Spec Miata.

 

It has been discussed several times over several years here, but LSDs are somewhat akin to go-karts with solid axles - the power to overcome the "breakaway torque" can only come from one place - the motor.  Have you ever pushed a solid axle go-kart with the steering wheel turned?  That's what your SM $6K motor "feels" when you turn the wheel and you have an LSD that has too much breakaway torque.

 

If you have 20 ft-lbs of breakaway torque?  Well, 20 ft-lbs divided by 4.3 rear end ratio is 4.65 ft-lbs (crankshaft) in 4th gear (1:1).. so that is 4.6 ft-lbs lost to the friction Gods any time you are not going absolutely perfectly straight. 

 

A properly blueprinted Cusco will (in theory) be faster than a MazdaComp, because the MazdaComp is fundamentally a 2-way differential (it drags anytime the outside and inside wheelspeeds are not exactly the same) and the Cusco can be set up as 1, 1.5, or 2-way.  If set up perfectly, a Cusco should never "drag" except when you need it to be "locking up".

 

Still, for most drivers, there is little reason to choose the Cusco over the MazdaComp for a SPEC MIATA - when properly blueprinted, a MazdaComp should cost you around 1.5 ft-lb of drag, and only when you aren't letting the car run "straight and free".  At power levels above SM, a Cusco should be considered mandatory.  The MazdaComp can't handle much more than 140 RWHP in terms of lockup capability. 

 

 

Definitely agree that an improperly setup clutch type diff can cause handling woes.  To add additional info, clutch pack preload creates what is referred to as a 'yaw stabilizing moment' that resists changes in direction and tries to keep the car traveling straight.  Thus, too much preload (static preload plus dynamic due to the ramp angles) will result in a car that will understeer unless a sway bar/ride height/alignment/other change is made to work around that.

 

Not sure I agree on the 4.65 ft-lb engine drag calculations.  I could be wrong, you have more experience with these than I.  That said, I typically find the fool-proof way to analyze drivetrain losses is to tackle them from a power standpoint, not a torque standpoint.  Consider this example:  20 ft-lbs breakaway preload on the diff.  The power being absorbed by that clutch pack is the 20 ft-lbs multiplied by the differential RPM of the two axle shafts.  Differential rpm is much lower than actual wheel RPM.  Making up a number, let's call it 5% which is approximate for a 100' radius corner.  If wheel rpm was 1400, with 5% differential speed, that's 70rpm slip on the diff clutch.  70rpm*20ft-lbf is 0.26 horsepower.  That'll be the same as engine hp.  If you want engine torque, you can simply convert.  Say 6000rpm, that's 0.23 ft-lbf.


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#19
SaulSpeedwell

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Definitely agree that an improperly setup clutch type diff can cause handling woes.  To add additional info, clutch pack preload creates what is referred to as a 'yaw stabilizing moment' that resists changes in direction and tries to keep the car traveling straight.  Thus, too much preload (static preload plus dynamic due to the ramp angles) will result in a car that will understeer unless a sway bar/ride height/alignment/other change is made to work around that.

 

Not sure I agree on the 4.65 ft-lb engine drag calculations.  I could be wrong, you have more experience with these than I.  That said, I typically find the fool-proof way to analyze drivetrain losses is to tackle them from a power standpoint, not a torque standpoint.  Consider this example:  20 ft-lbs breakaway preload on the diff.  The power being absorbed by that clutch pack is the 20 ft-lbs multiplied by the differential RPM of the two axle shafts.  Differential rpm is much lower than actual wheel RPM.  Making up a number, let's call it 5% which is approximate for a 100' radius corner.  If wheel rpm was 1400, with 5% differential speed, that's 70rpm slip on the diff clutch.  70rpm*20ft-lbf is 0.26 horsepower.  That'll be the same as engine hp.  If you want engine torque, you can simply convert.  Say 6000rpm, that's 0.23 ft-lbf.

 

Yeah, I see your point, the lazy 4.65 ft-lb math was, at best, only directionally illustrative ...

 

Having said that ... and I'm admittedly messing with you a bit here .... but to bring the thread back to the main point of the OP's question, if 0 differential RPM equates to 0 power absorption, what do you think a MazdaComp LSD is worth versus a welded axle?  

 

:spin:    


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#20
speedengineer

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Having said that ... and I'm admittedly messing with you a bit here .... but to bring the thread back to the main point of the OP's question, if 0 differential RPM equates to 0 power absorption, what do you think a MazdaComp LSD is worth versus a welded axle?  

 

:spin:    

I think that welded diff would be the hot ticket on the Friday fun night at the drag strip  :)  ;)  Not good for much else though!


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