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General Category >> Classification questions >> 1993 Miata 1.6 for STS

Message started by Graham Brockley on Nov 3rd, 2017, 7:40pm

Title: 1993 Miata 1.6 for STS
Post by Graham Brockley on Nov 3rd, 2017, 7:40pm

Hi there!  i just joined your club online. I live in Duncan and hope to come down for some Solo II fun this year!

I have a 1993 Miata that is stock and in need of some attention - close to 300,000 km and overdue for a timing belt.  I want to prepare it for STS and have a few questions:

1) Flyiin Miata sells subframe connectors that stiffen the chassis up by 30% they claim.  According to the rules apparently these can only be attached with 3 bolting areas - front, middle and back.  Would that be two bolts per area so a total of 6 bolts per subframe connector?  The FM comes with (as far as I can make out) an intended 12 bolts per subframe connector so 24 total.  

2) The engine needs rebuilding but the smallest OEM oversize piston according to our local Mazda dealer is 0.025” over whereas the rules state 0.020 is the maximum overbore…is it ok to use 0.025” if that's all that's available?

3) How much can be ground off the head?  The rules in Street (but not STS or STR) state the head can be milled but don’t specify an amount.  Milling the head 0.020” would increase the compression from 9.4:1 to about 10:1.

4) Flying Miata also sells braces that strengthen where the sway bars attach to the chassis since this area tends to fail.  I’m not sure if these would be legal.

5)  I am planning to use the Flying Miata Fox suspension.  Do you see anything illegal here before I order it?

I tried to post links to the products mentioned above but I guess I'm only allowed to do that after 5 non-annoying posts.

Thanks!  I’m sure I’ll have more questions as I order parts and hopefully get things ready before January!

Title: Re: 1993 Miata 1.6 for STS
Post by KarlR on Nov 5th, 2017, 10:19am

Hi Graham and welcome to the club.  We'll be looking forward to having you join us for the 2018 season starting on January 14.  The Miata is a great car and with the right mods will do well in STS.

1. The sub frame connectors are not allowed in STS and would move the car to CSP.  
2. I would investigate further to find what the maximum factory overbore allowed would be. If you exceed it you will again move to CSP.  
3. Again, we are seeing a trend here, you can mill the head to factory rebuild specs and not beyond.
4. I would have to know more about the bracket you are talking about adding.  You can add larger sway bars in STS but cannot modify the mounting points.  This mod may actually move the car to SSM.  
5. You can add coilovers and such for STS but again, I do not know all of the components you would be replacing with the Fox suspension.  This could move you out of STS as well.  

I usually caution new drivers about making too many mods all at once.  If you have never done slalom before, the car, even in it's current state will be better than you are.  I would recommend coming out, even to watch and learn from others before going crazy on the mods which may not benefit the car.

The one mod you have not mentioned and is the best dollar value is tires.  Having a good slalom tire will equal all of the mods you have mentioned above.  See you in January!

Title: Re: 1993 Miata 1.6 for STS
Post by Graham Brockley on Nov 5th, 2017, 7:53pm

Thanks Karl.  I finally got around to doing a compression test today and it was surprisingly good so I think I will just do the timing belt for now.  I found a drip which is explaining the oil consumption,  I do have 7.5 inch wide 15 inch Konig Hypergram wheels (have yet to buy tires).  The shocks seem to be in pretty good order too so I may take your advice and fend off the modification impulses for a bit.  Thanks for your feedback!

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