And it seems that we both missed a fun time. I’ve come along much later and found it impossible to untangle the claims, counterclaims, wishful thinking, egos etc. and I’m not going there. From what I have seen here is a quick summary:

Mazda Australia raced FDs in the local production car series. They won the premier race 4 years running, the first 3 at Bathurst. They then homolgated the RX-7 SP which won the 4 the year at Eastern Creek. Only the circuit cars were fitted the larger specially developed Hitachi turbochargers. For some, the terms SP and Bathurst have come to invoke mythical powers. Mazda used the Bathurst moniker for a (not that) special version later sold in Japan.

Sasha – The Doctor – FDMotorsports – had a run of larger than stock Hitachi turbos made and sold them as Bathurst SP turbos. The exact relationship of these to the racing SP turbos appears unclear. Shasha's power claims for these turbos were widely challenged on this forum.

As far as I can tell Sasha – The Doctor – FDMotorsports have disappeared from the scene.

It appears that Raceonly took the Bathurst SP turbos up for a while but have since gone their own way.

Marcus Read - MATEY - is still operating and is highly active on Facebook. Raceonly have a view on his turbos. MATEY no doubt sees things differently. Each have their fanbase.

 

Are those turbos specially developed by Hitachi, the KAI turbos many of us in the States and Australia bought around 5 years ago and were available from Hitachi for a few years?

Mike

 

This coming from long time contributor, an owner of KAIs, and poster of an actual compressor map:https://www.rx7club.com/3rd-generati...nyway-1153932/ speaks to the confusion left as the players from long ago leave the scene.

Most likely the SP race turbos were a one off production. According to https://www.ausrotary.com/viewtopic.php?t=157658:Sounds like a reliable enough source.

 

Sasha was working with Marcus for a bit. I think they had a falling put at some point, he tried to sell his "own" version of the high flowed Hitachi turbos and U type intercooler setup. I think he has burned a lot of bridges.

There are a lot of guys running Marcus's high flow Hitachis on ethanol, so they are working a lot harder than factory turbos in terms of total load, obviously plain/thrust setups have limitations, I think from memory he has changed a few things on the assemblies over time. Marcus did play with Garrett Roller cores for a while, I think he still has a set in the shed he showed me one time I picked up some parts. I'm not personally interested in sequentials as I don't need to fit a racing class and not having a transition dip or delay is more attractive to me. I think with sensible port combinations and using existing components with modern turbos you can get a very flexible engine package, but I understand that it appeals to some and having some instant boost from very low rpm is nice.

If I was going to try an all out sequential setup I think I'd be attracted to Garrett style roller core arrangement myself.

 

And while all the arguing was going on, USA-based BNR Supercars continued to build upgraded bolt-on twins for the FD3s. I ran one of Bryan Nickell's first sets non-sequential back in the year 2000 on my old VR R1 FD. Back then not a ton of options and from memory made the 40 to 140 mph pull in 14 seconds on the street. In 2017 I ported and built an engine for my brother's SSM and he set the sequential record for pump gas sequential BNRs: