spekdah

I dunno.
For the last hour I've been thinking about my full non-seq setup and dont get me wrong cos I love it , but I cant help thinking that there was something cool about the stock Seq setup, something uniquely Mazda. I dont really consider any single Turbo setup on an rx7 as being ' uniquely Mazda' . turbos are pretty much a generic bolt-on be it aftermarket or stock, but there IS something uniquely mazda about their twin Seq setup on an FD.
In my haste to move to a simplified turbo setup that was DIY and cost effective, I think I overlooked the reasons for owning an FD and , essentially, tore out one of the only two things that are truley at the Heart of an FD, its 1.Rotary engine setup boosted by a 2. sequential turbo setup.
This has led me to question what it is I actually love about these cars and after sometime i can safely say that , for me, it all comes down to one word, ' history ' .
For me this means that when I look at the aesthetics, performance, handling and technology that goes into an FD I also understand that it wouldnt be this without the Mazdas willingness to develop and refine the Rx7 down through the generations and perservere with their belief in the Rotary engine from the earliest RX models right through to todays RX8.
But its when you hit the 3rd Gen that you see Mazda's , somewhat, riske approach to the Turbo system. Instead of a simple single they decided to invest their Money and development into a Seq twin setup and once I thought this was a crazy Idea, in fact I wouldve called it ' Turbo ****" all them vacume hoses, pre-control this, Charge relief that, Turbo pre-control ..etc and it goes on ( as you know) not to mention just learning to understand it all as well, It was easy to question the sanity of Mazda bolting this complicated mess to the side of , what was once, their lastest RX gen offering to a Rotary performance market and arguabley their best 13b to date ( some may say the RENESIS wins over with overall reliability, but for me the 3rd Gen 13b is ample relaible enough and hoggs the performance limelite for a god reason ).
I suppose you need to look at how ' market driven ' the RX7 wasn't and yet how 'market driven ' an Rx7 with good all round drivabilty with its seq setup was.
If there is some truth to this then the lengths that Mazda went to could be seen by some as nothing short of ludicrous. the reasearch that must've gone into and settled on a 10-8-10 pattern, the turbo pre-control system and 4500 transition, the charge relief setup and all the accompanying check valves, solenoids and vacume tubes all researched and tuned to drivers market ( cos it certainly wasnt tuned to a high performance market, not in seq setup anyway ) . Could we consider Mazdas foray into the seq turbo setup as one of being uniquley Mazda driven? or was the seq system a market driven setup that , in the end, inevitably ended up looking like turbo ****?

How do you see it?

quicksilver_rx7

Mazda "adopted" the sequential turbo system because it added to the balance that the RX-7 presented. First, the rotary has no low-end power in N/A form, as we all know. A single turbo would only pronounce this problem. While this is acceptable in the aftermarket world of track cars and dragstrips, it is not when trying to market a street-driven sports car (or at least not at the time when the RX-7 was new). Mazda knew this, thus the sequential idea was adopted to enhance overall low-end power, thanks to Porsche. Which, oddly enough has always been the role model for the RX-7. If you want to know what Mazda was thinking at the time that the RX-7 was designed and built, go back and look at the progress of Porsche over the years and that will bring some light to the topic. It does appear that Mazda has abandoned this approach with the advent of the RX-8 and only time will tell if Mazda will return to those roots and if we will have another pure sports car like the RX-7.

Joe

Improved FD

it's a hopelessly complex and poorly engineered system

take a look at a Mark IV Supra sometime

dgeesaman

iTrader: (7)

I think it's a fascinating solution to the broad rpm range that Mazda engineers were trying to boost. Given that Mazda was trying to make a sellable car, but still deliver at the top end, it was the only option.

In the hands of a true enthusiast/racer, the broad coverage of sequentials is kinda pointless, since that driver *should* be willing to stay in the powerband. But in the hands of 90% of owners, the sequential system is a joy and engineering feat in that it *did not* have the lack of top-end that the 300zx did. The z compromised overall performance for that low-end punchiness that made for sales, the FD did not - it retained both.

I think the complexity is mostly due to their interest in making a good transition. The Charge Relief valve, precontrol, etc were all added to make a 10-8-10 instead of what may have been a 10-3-5-7-9-10. The other element of complexity that is hard for us to deal with is the small but significant side effects of raising boost and adding bolt-ons. IMO, with stock bolt-ons, the sequential system is remarkably consistent when the components are working.

Dave

F0RSAKEN

I cant help but think that the system could have been better designed, and simpler, with electronic control instead of vacuum, but I agree, there wasnt anything (for me) like driving my FD for the first time. The immediate power was awsome heh.

YELLOWGSLSE

iTrader: (7)

^Meaning what^?? What exactly are we looking for?

dgeesaman

iTrader: (7)

I can't help but suspect that if they put a fully electromechanical set of valves that the sticker price would have gone up $5000 and we'd all be cursing it even more now. I think that the US requirement of a precat is the biggest problem.

Dave

WaLieN

Over the years of owning this car, I have done a fair amount of sequential work (making small parts/troubleshooting). After all this, I have a perfectly working sequential system that makes a full 13PSI @ 3,000RPM. My sequential system works like a charm. /knock on wood

As mentioned before, most of the issues are due to the hundreds of hours of heat from the stock pre-cat. In addition, many people overboost the stock solenoids, which in most cases, hardly meet the stock turbo pressures. The sequential system was simplified later on (w/ the 16bit ecu).

Also, what about the Supra Sequentials? They're a tiny bit simplier.

BryanDowns

iTrader: (2)

ditto.

While it is genious in its design, the engineering specs on the reliability of the components, as well as the component selection itself in a very high heat environment is very poor.

Want proof? How many FD's have you saw w/ over 100k miles on them that havent had work on the seq stuff and still boost a perfect pattern?

100k miles isnt some great feat here. Nearly every car on the road is capable of doing it with hardly any work besides an FD. Even FC's....

Theres my rational.

edit: and no its not uniquely mazda. Porsche did it on one of their cars using mechanical vaccum stuff before mazda did.

Joe Geiman

My FD has 85,000 miles. I've had to replace only one check valve. It works perfectly.

scotty305

iTrader: (2)

I think that it was a great system given the state of technology in the late 80's (when the FD RX-7 was designed). It would have been nice if they had used a purely electro-mechanical system, relying on electric solenoids, microcontrollers and wires rather than vacuum lines for signal routing. It's likely that cost and reliability concerns kept an all-electric system out of production.


In Mazda's defense, the vacuum-actuated system was pretty standard for the 80's, and the RX-7 fails safely. Note that the FD loses power as a result of a vacuum line failure, as opposed to overboosting and blowing a motor.


Using today's technology, I believe that a properly-sized ball-bearing turbo with a well-designed electronic wastegate control system would yield a powerband similar to our vacuum-controlled twin setup. A variable - (housing) geometry turbo system would be even better.


-s-

G's 3rd Gen

iTrader: (11)

not this arguement again.......

Improved FD

if it's so "genius", why do later model japanese spec FDs have a dramatically simplified system?

it's about as "genius" as the plastic AST and a host of other plastic engine parts on a car that runs hotter than just about any other

dgeesaman

iTrader: (7)

1) The later JDM cars have the exact same solenoids, actuators, check valves, and chambers running the sequential system. The main difference is they consolidated some of the solenoids into one chunk that also removed some of the vacuum lines.

2) The rest of the stuff that might have been taken out is simply because there was so much in the USDM FD that was there for corny US emissions standards. If you take the time to get to know what's under there, you'll realize that at least half of the rats nest and vacuum lines aren't even part of the sequential system.

Dave

spekdah

There is no arguement bro, I think this is inspired debate over something that only FD drivers can really talk about, and Its good to post a topic and come back 2 days later and see some awesome sensible feedback

nocomply24

I think the setup makes the FD and FD. I really think that most of the problems people expierence are because they way over boost and they redline all day every day. With stock everything....i think it is a great setup, and is a joy to drive. With out it an FD is not an FD...

Improved FD

to be perfectly honest (I'm not just saying this to defend the money spent), since upgrading to non-sequential BNR Stage 2s with the lightweight flywheel, full exhaust, and fully ported "rich man's non-sequential turbo manifold" (thank you David Garfinkle) I do not miss the sequential cluster for even one second....boost comes on about the same, just a tad bit later (about 3200 rpm, only really noticeable in fifth), and when it does, it builds in a smooth rush, no "spike", no "transition", none of that stuff!

Mazda messed up, only a purist would maintain loyalty to such a goofy system, you couldn't pay me enough to go back to that mess! I can actually see the engine now and get to stuff, instead of half a million little rubber hoses and solenoids running everywhere

spekdah

A couple of good questions arise from this -

1. was it at all possible that Mazda couldve sat down and thought about the whole Seq direction and looked at other directions e.g. lighter flywheel etc as a less complicated way to address low end torque / street driven sports cars issues

2. Even if Mazda did explore different options to address these issues, were there other options as cost effective as the one they opted for ( seq setup)


More and more it seems that the the reasoning behind the seq system primarly lay with addressing the low end lag issues of the rotary engine and I have to say that, I myself ,wouldve preferred Mazda had invested a little more time and money come up with something that wasnt so " goofy ".

put simply they did the turbos " on the cheap" when it came to the 3rd Gen which is a collosal let down considering it was competing with other Jap sports cars on the market at the time ( r32 gtr, supra....) which was a pity.

History aside, its official, its turbo ****

Nghtstlkr7

think about the market and available materials at the time. also consider the fact that its likely Mazda put a budget on the project... only allowing the engineers a finite amount of options to go with in making a car that can compete with the other japanese, american and german sports cars of the time.

... the car was to be an affordable alternative that could compete with, and in some cases out-class, cars like the MKIV Supra, 300ZX, Corvette ZR-1 (i think thats what it was), 911, NSX, etc.... if mazda had opted for newer technologies and materials the FD probably wouldve been hideously expensive, even today. Twin Turbo MKIV Supras STILL go for upper 20k-30k... im not looking to spend that much in a car thats nearly as old as mine.. and lets not talk about the NSX.

... consider the possible time constraints. the competition was churning out cars at around the same time as the FDs debut. Mazda wanted to hit the market as quickly as possible in order to give the consumer something else to look at. in that rush then yes, perhaps the engineers cut corners, but in my opinion they did the best job that they could with the money and materials that they had access to.

when properly maintained and not abused the seq. system is an engineering marvel... all things being considered.

Improved FD

they should have just put a small to medium single turbo in it, like the old FCs, especially in keeping with the "weekend racecar" theme....they knew most of the owners would modify the car, it's just like the race replica bikes, just about everyone who owns one puts a race pipe and different shock on it

the engineers needed this stamped on the their forehead: KEEP IT SIMPLE AND RELIABLE (ROBUST)! that's the number one rule of any car intended for even recreational racing use

think of everything they could have done to accomplish that goal...if they did, the car would likely still be here, giving the EVO fits

FLA94FD

Considering that it still has losts of lag it's a total wast time and money. Working perfectly sequential thank you. I would easily trade 500-1000 rpm for the dangerous transition. How many FD's have been lost in careless driving right after transition.

These cars are torqueless below 3000 even with lots of boost. I also make 14psi @ 2500rpm. The fact is they just don't start to pull good until you reach around 4k, look at any dyno chart.

GARCO MOTORWORKS

My 94 had stock working system , then I worked with it to get a 10 - 9 1/2 - 10 boost at 4500 rpm . All was good then I started working with the non seq setup and I liked the simple set up ,easy to maintain .A little slower down low but totaly faster when 4500 rpm came around . Then the major change, The BNR stage three screw up ,I got a set .Brian was trying to find a solution for everyone .After alot of talking on the phone he sent me the new design Stage 3 supersized .After more thought the production stage 3s were out with the stock cold sides . Now I started porting and changing things on the main manifold ,hot sides,and wastegate .Now with the richmans non seq , I would never build a stock setup for myself on one of these cars .I think The car is more fun than before .People around Murfreesboro sure hate it . Boost starts low enough and I do not wait for 4500 rpm before the rush is on . The stock setup with aftermarket modified turbos was better than stock for me but the BNR and richmans non seq is what I will stay with .I have no desire for a single on this car ,maybe if I build a car to race that needs way more power .I am not pushing any system ,do as you like . I like my setup and that is all I am saying .

Improved FD

you obviously have never been in an FD with a medium sized single turbo, what "dangerous transition" are you talking about??

Alpine

I think the fd seq. system is a very impressive system, but I wish they would have put the solenoid racks somewhere else !! it would make it much easier to diagnose and keep it away from the heat.