Come along on my journey for a destroked 1.7L Miata
 

Heya folks!

Call me foolish but I'm starting a long-term project to make a wild setup.

• BP8 block bored and sleeved to 85.5mm
• Billet crank with 75mm stroke (1.722L)
• 1.97 rod ratio (shortened pistons & longer rods)
• Custom cam profile
• & of course a host of supporting mods

Should be able to turn 10,500 RPM, with a mean piston speed of 26.1m/s with a peak of 40.5m/s and peak acceleration of 56829m/s/s at TDC.

Working on quotes for all this right now. Budget = yes. First order of business after verifying I can get all of this is ordering the billet crankshaft and sleeved block.


https://cimg4.ibsrv.net/gimg/www.mia...f1fc5fbfac.png
(I also have the data for a stock BP8 at 7500, not pictured)


Why you ask? Because I want to hear this thing scream.

I applaud your aspirations but i have to ask. Why not just buy a k20 and swap it if you want a high revving 4 cylinder? If you have the budget for this you have the budget for a screamer all motor k20.

Can a BP head flow the volume needed for 10.5Krpm of air?

It simply comes down to me being passionate about the BP8. I really like it as a platform and want to push the limits.

It's roughly ~33% higher flow at redline. That shouldn't be an issue with porting and FI. But we'll see!

I appreciate your passion. Looking forward to your updates.

Sounds wild. You used math so I assume you know what you're doing.

The BP is a weird engine to be enthusiastic about, but more power to you (literally!).

In for the results, hope it works out.

Short stroke crank in the UK
 

Hi folks
I am embarking on a similar journey in the UK,
I had a quote 18 months ago for a custom crank, short stroke !
I will be using 85mm pistons in a BP4W block I want to build a high reving motor with 1796 cc for a roadgoing sprint and hillclimb car.
My local class is 1400cc to 1800cc then 1800cc to 2800cc
I already have some of the parts I need. I will be collecting a donor engine in the next couple of weeks.
This is for an ITB build !!!
I am already at 169 BHP with a stock BP4W block and mild diy head work + cams. aftermarket ecu and bike throttle bodies.
Tuned at https://enginetuner.co.uk/

This is awesome. Both @TowerCrisis and @DickieRSLTD!

Looking forward to your progress and results.