Differences in Series 7 and Series 8 engines
 

Were there any changes inside the engine (sorry if this has been asked before)?

I just read this, which mentions an intercooler fix and a turbo-to-intercooler pipe "bomb" issue in the Series 7 that I hadn't heard of before (hopefully fixed in a recall):

AutoSpeed - Last of the Line RX-7

It looks like their are just describing the Y-pipe which changed in 96.

I guess it would be a vivid memory if it happened while you were driving fast.

The series 8 uses a Mikuni OMP which is different than the older Denso unit...and also they upgraded the oil injectors as well. Thats all I know...

Good info. This is the stuff that I'm looking for... I was also wondering if they played with the seals or ports, plating alloys, rotating assembly, etc. Most people treat them all the same, but enough time has passed that some of the details have gotten out. I don't remember reading anything much about Series 7 or 8 internals in Brian Long's RX-7 book, for example.

I'm also curious about stuff like the progression in spring rates, suspension bushing durometers, etc... just wondering which directions Mazda went in the FD's relatively long life (at least in Japan) – I know a lot of the info is scattered through the internet, but there hasn't been a lot of official documentation. I'd like to apply some of the newer technology to my '93, if possible.

Don't know if you read this, but you might be interested:

99 RX-7 Updates

'99 FD3S

The only internal change in the engine was going from 3 piece apex seals to 2 piece. Same material just not cut into 3 pieces.

that didn't happen until the Rx8 came out, 2003.

the intercooler pipe they are talking about was upgraded in 1996

Thanks, guys! This is really helpful – it looks like almost every change improved performance.

It's kind of hilarious that the most exhaustively detailed technical information is presented in Comic Sans on a white and blue page (anyone remember WordPerfect?). A classic case of substance over style.

I guess some of the other stuff (e.g., metallurgy, etc.) could be considered a trade secret – something Mazda wouldn't want to patent or publish papers on, for example.

there are usually SAE papers... and then we also recently have acquired the JDM parts catalog

The turbo to intercooler Y pipe is absolutely not a "bomb" or whatever sensationalist thing an article would have people believe.

Simply, the plastic pipe joins to the turbochargers via a very poor quality factory rubber coupler, measuring 75mm diamter by 75mm tall. Under boost and with small amounts of PCV oil vapor that gets pushed through that pipe, over years, eventually the rubber coupler softens and loses its grip on the plastic pipe. You bring the car into boost, and the pipe coupler loses grip and 'farts' a bit of boost out, worse case it falls off completely, and no boost. Just a bit of a deflating feeling when driving- you put your foot down, and it does not go fast. Nothing too memorable about that, and I had it happen to me. Some writers like to hype things up, because in reality they don't know what they're on about.

The cheap fix on the stock standard car is to remove the old oily soft rubber coupler and clean the end of the Y pipe and the boost pipe, and fit a quality silicone coupler and quality clamps.

If you're really pedantic and have the $$, then change to the aluminum bolted pipe from the later cars, which IMHO is more $$ and time than I can be bothered with- I've daily driven my car for nearly five years and suffered the stock rubber coupler losing grip during year 2. Changed for black silicone (changed out every nasty rubber coupler in the engine bay) and had no further issues.

In the later cars, there were minor rear subframe & suspension updates and changes. Also, the brakes got bigger and bigger through the years, as the power increased, due to the more efficient redesign of the twin turbos, and the factory air intake was improved to eliminate hot air reversion into the intake from the intercooler.

Interior wise, the quality of the interior improved dramatically as years went on. Cluster and instruments went from the orangey-red lit, to green backlit on most models, and the smooth peeling interior coating was dropped for the hard textured plastics.

There was not a huge deal of change really, which is a testament to how close/how well engineered the cars were when initially designed. I've owned one of most years, from 1992 to 2000, being in Australia. The Series 8 cars are much nicer and have more of that wow factor, being the best evolution of them. But to improve a Series 6 to an 8, there is not a lot of work to do. Just small things.

It's interesting to me how Mazda attacked the engineering problems on the FD vs. the aftermarket. Less overkill and over-selling, more small things. They obviously had modest resources to develop this low-volume sports car, which reminds me of their Le Mans racing program... passionate, but obviously an underdog effort.