I’m looking to build my 04 Mazdaspeed Miata to its true form. I want run a Borg Warner 6258 .80 Twin Scroll and 9.5:1 on pump gas 91-93 is the best octane I’m able to get as of my current location. I want to know if this is remotely possible or is this me chasing a dream?

 

It will work fine but you are going to be knock limited around 280-290 whp.

Dann

 

Im running a standard T25 6258, and make about 300whp at 17-18 psi. on 93 pump gas.
rods only motor build with pistons out of a 94 miata. these supposedly have lower compression 8.8:1 or so.

280-300hp should be doable for you with proper dyno tuning.

 

 

lower compression pistons. 8.6:1 is ideal for high boost pump gas motors. pistons are pricey though ~$500 plus you need to bore out block.

 

 

I, too, choose to sacrifice performance from 2200rpm-7500rpm in order for a small bit of extra pickup between 1200rpm and 1800rpm

 

 

then your max hp ceiling will be knock limited. how much limited? no one knows. but you will find out when dyno tuning and listening for knock.
another way to reduce knock is methanol/water injection. i've never done it, so dont have much info about this.

im pretty sure you should be able to hit around 300hp with 9.5:1 pistons. on pump gas.

 

 

8.6:1. I also build engines and sell the best Borg Warner turbo systems on the market for these cars, FYI, so I have a bit of experience doing exactly what you want to do.

 

 

 

10-15psi will get you 220-280ish whp.
you can do that on stock pistons. Just install stronger rods.

or get forged pistons if money is no issue. With 8.6:1 CR.

9.5:1 pistons is for e85

 

You will never notice, and you would be hard-pressed to measure the difference.

 

 

 

 

Raceland or begi

 

Check out my website or call me for specific recommendations. We also do complete longblocks custom-built to your intended usage.