Giving all the engineering hurdles, budgets, and reliability issues...it seems like a big waste of money and time.

Was it simply so they could say "we did it!"

Perhaps just a marketing scheme?

Far as I see it...

Seq = faster spool less power
Non seq = slower spool more power

Is the slightly faster spool really worth the hassle?

I'm really curious as to WHY Mazda choose to make the worlds first production sequential turbo setup?

 

You're forgetting that the Eunos Cosmo had sequential twins back in 1990 (20B and 13B-RE). And "gee wiz" technology sells high end luxury cars.

Mazda just adapted those systems to the FD. The FD is a little more modern than the 13B-RE with a different crank angle sensor, better mounting, etc.

 

You're a bit too generalized mr OP.

significantly faster spool, very slightly less power.
versus, significantly slower spool, very slightly higher power.

If you are doing large track driving, then sequential is pretty pointless as you will rarely drop below the rpm threshold to revert back to primary turbo operation only... if you are autocrossing, sequential is great.

If you were selling a car that is going to be driven mainly on the street... which is what 90%+ of rx7s are driven on.... wouldn't you want it to lend itself perfectly to that environment? sequential operation makes for a VERY fun car to drive in town. even short burst of speed are easily achievable and you are not required to break the speed limit every time you hit boost. Though many people like to track these cars, Mazda still had to make something that would sell itself on a test drive.

 

Maybe Mazda didnt forsee reliability issues. And when/if they did they realized it would be too expensive for a car in this price range to solve.
However you should read the thead here somewhere that posts quotes and so forth from mags that tested the car 93-95. They are very good reviews for the most part.

Had they gone non-seq, they may have surpassed peak power of the competition but the powerband would've been too narrow. IMO
In order to sell the car to more than just enthusiasts (who would've actually said "gee whiz") they needed to have some low-end torque of the seq system.
The competition (300zx, et al) had the torque and driveability of a v6, plus tt.

 

You must don't know Mazda too well!

Mazda's focus (when it came to the rotary) was to always engineer the vehicle around the engine. Handling and response has always been Mazda's biggest theme. Hp was secondary. All the other manufacturers build their sports car the other way around. Now as far as the turbo system. It's simple! The Fd is still a street car. That means 99% of it's life will be on public roads. Stop and go traffic, low rpm cruising, ect. An engine with more torque is always more pleasurable to drive around. Two rotors don't have any. Since the Fd was to only be turbo charged, the sequential system was the best option in improving the bottom end for the smallish engine.

 

Quoted for truth.

There have been other manufacturers that have done sequential turbos, or having a supercharger for low-speed punch that gave way to a turbo charger at higher rpms. Turbo lag is THE #1 complaint amongst cars with turbocharged engines...so Mazda was very wise to develop the system they did.

 

they could've used a larger version of the FC's twin scroll turbo and still had good response, but when every other manufacturer has two turbos and you've only got one it's going to hurt marketing

 

no actually they were looking for 10lbs/hp in the FD and the FC single turbo couldn't do that*, without loosing the low rpm response that everyone complains about anyway.

rant! even if the FD came with some 400hp single turbo engine that ran 11's off the showroom floor, the magazines would have complained about the lack of torque under 3000rpms...

i actually got to drive an FD with a hybrid FC turbo on it, and its nice, it goes about like stock, but has a real boring power delivery. the twins are complicated and stupid, but they are FUN on the street. there is NOTHING else that delivers power like that

*in production, emissions legal warrantable trim.

 

They still can...

 

and do!

 

If memory serves the first production car with sequential twin turbo's was the 959 in 86.

~S~

 

Most people buy a car to drive, not to jerk off over high rpm dyno numbers. (Please don't mention reliability or simplicity - if you want those, buy a Camry.)

 

959, then came the Cosmo, FD, JDM Subaru Legacy and the JZA80 (MKIV) Supra.

 

mazda likes to do things frst!

1.8L V6 in the MX-3

Miller Cycle Engine in the Millenia (now in use in all hybrid vehicles as an Atkinson cycle which is the same sans supercharger)

etc etc

 

You also have to remember that during the era of the early RX7's the 'gentlemans agreement' was still around (look at most Japanese sports cars from around the early 90's, and all will be slightly less than 280/270HP). I doubt Mazda had any urge to build more power, much less change the whole turbo system just to gain 15 hp or so.

 

I would have to disagree with the less power statement. A friend of mine that had his car built at defined autoworks made 360whp fully sequential. In fact my friend was adamant that the sequential system worked, and worked properly. I only made 334 non sequential on my car. I don't think many people decide to put the time and effort into there FD to really find out what works. Mazda had allot of time and research go into the FD. Mazda is also a very small company, and had money trouble at the time of the FD. I don't think mazda would have wasted there time or money if they did not feel the sequential system was much better. In my opinion a working sequential car gives a better feeling than a non sequential.

 

I would not label the 959 as "production" with 337 units made between '85 and '88 including 8 in '92 of which 37 were prototypes and pre-production, 37 race cars and 8 were post production parts assemblies.

Quote:

Originally Posted by neit_jnf

mazda likes to do things frst!

And add first production hydrogen engine (rotary)

 

why do people always say that? where does the more power come from? above 4500 RPMs both setups are flowing the same CFM...

 

With a few less flapper doors, and waste gates in the way, a non seq system could likely flow a tab bit more. the problem is you pick up lots of power when you port the waste gates and get good stable boost, something that is usually done when going non seq, but non done so many stock seq setups.

You guys are comparing 3 things here, not 2.
stock seq
modified non-seq
Modified Seq<- king for any rotary setup under ~450rwhp.

 

True but not truly classed as a production car. Besides, Mazda never claimed to be the 1st sequential only the first affordable.

 

because sequential!

 

Basically EVERYONE who has ever driven a rotary complains about lack of low end power, so Mazda was looking to resolve this issue.

FD sequential is still a dog from 1,000rpm to 2,000rpm.

Starter/generator/electric-supercharger with engine cut at stop is the answer for rotary for this and many other woes.

 

Add a couple cats to your non-seq FD and show the dyno graph.

Seq works great for the street. Nice singles make more power but the are 10-20yrs ahead of the development of the seq FD and would never have the response or power with cats to pass Federal emissions tests.

Now a bunch of V6 Mustangs, Altimas, etc are almost as fast in a straight line as a stock FD.