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OSG Diff - NC Miata

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Hey All


I'm considering adding a differential particularly a OS Giken unit (also open to Tomei) to my track focused NC, however, I had a few questions about the default factory settings and whether it would work for my particular application. Any insight would be much appreciated.


Background: my NC1 is primarily a track car (currently I participate in HPDE events with the intention of competing in TT or Time attack in the future). As of now, modifications to the car involve suspension (coilovers and sway bars), wheels and tires (200tw - RS-RR), however, in terms of power modifications, the car is approximately at stock power level (future plans include 2.5L swap). Note: the car currently has an open diff. In terms of driver experience, I’m at the point as a driver where I've developed enough to where I'm starting to push the limits of the car and would like to further improve my times. For comparative purposes, I'm within a few seconds of spec Miata lap times at MSRH, although this is not impressive, there are clear differences between spec Miata and my NC in terms of how early power can be applied, suspension handling characteristics and tires. Without considering upgrading suspension or running R-Compound tires, this has lead me to consider adding a diff. with the thought process being that it will allow me to get on the throttle earlier on corner exits. 


As for selecting a differential - I'm considering the OSG unit because from what I have read it is best suited for track use with the least amount of adverse handling characteristics compared to other options. I've considered going the factory OEM diff. route however, I want to future proof the car and not have to acquire another diff down the line should my build change and the OSG unit might be something that I can grow into as I continue to develop as a driver. I've also consider the Tomei unit as I've read that it will handle the power levels up to about 300hp. Any input here would be helpful as well.


In regards to the OSG diff, I have some concerns about the diff. particularly the default set up  from factory. Note: the OSG diff comes from factory as 1.5way ) Would it be necessary to further setup the OSG or would I be able to drive it with the factory default settings and still benefit from the diff for my application (<200hp) on track? Based on what I could find on the internet there is mixed feedback, certain individuals state that even with default set up, the diff will perform well on the Miata. Others albeit from an AutoX perspective have stated that the default settings from OSG have too much lock for stock Miata power levels. it's not exactly clear if this the case, if anyone with experience with this setup could chime in and provide insight, it would be tremendously helpful. If additional setup is required, what is the recommended settings for the diff for my application?


Super appreciative of any insight or suggestions for someone who is starting out!


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It is an interesting question.   On my NA miatia I have a limited slip differential.   In my case I am not able to get the car over 80 mph so let’s just say the differential is not at the top of the priority list I am more interested in safety equipment!  

i changed the differential in my s2000 when the old one broke and changed the ratios to give me more torque.  Like all mods it changes the car I I have enjoyed to mod on track  and on the street. 

While I was working my way up the drivers food chain of performance I tended to always do one more thing just to drop my lap times a keep up with everyone in my run group.  Now I just focus on staying safe improving my driving while using the cheapest slowest car  at the track. 

Therefore rather than focus on the technical merits of your next mod I would recommend you continue to beat on it as is ,have fun and stay safe.  


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An OEM diff is a fraction of the OS Giken's cost and it is doubtful you would notice the difference at this point. You can likely get what you paid for it when you wanted to upgrade. 

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