Ralgh

We have been working on making my brothers car non sequential. We have tons of documentation and have started the project. After seeing all that I can only conclude it was designed on a bet. Some engineers must have said to some other engineers I bet you couldn't make this kind of system work. After looking at torque and horsepower curves the sequential systems only advantage is getting boost a little sooner. Yet is tremendously complicated. 76 individual vacuum lines just to make everything happen at the right time. Oh boy these engineer types are crazy.

j9fd3s

iTrader: (3)

actually mazda had been working towards the goal of a flat torque curve all through the 80's. it starts with the 6 port 12a in 81. the 84-91 6 port 13b's. then they have the twin srcoll for the 85-88 turbo motors. then the vdi for the 89+ na's, then they have the twin turbo system in 89 for the cosmo.
the next step is the renisis, that one is going to have valves and stuff too.

mike

Benjaminaco

actually, I believe the 87 porsche 959 twin turbo used sequential turbo charging as well... though making it work on a rotary engine is another matter all together I am sure

-Ben

Ralgh

Oh I'm just joking around. But that system is super complicated. Plus the HP and Torque curves I saw show a flatter curve on the non sequential.

turbojeff

iTrader: (30)

I know your kidding but this is the REAL deal. The 76 vacuum lines aren't entirely for the seq system. Many of them are emissions related, ACV, double throttle control, purge control, OMP. Take a look at a TII, very simple turbo system and they still have tons of vacuum lines.

Jeff

rx7will

iTrader: (6)

I think the TIIs have a pretty flat torque curve, i remember seeing it somewhere. The TII does have a few vac lines but nothing like the fd. I used block off plates on my TII and i think i was only using like 5 vac lines. Simplicity is nice.

turbojeff

iTrader: (30)

The power curve of a TII sucks in stock form. NO POWER until 3500rpm, in the summer with the AC on, forgetaboutit.

The seq are very good for street driven mildly modded cars, also very good for auto-xing. Boost comes on at 1700rpm in my car, much better than 3500rpm.

It isn't so much the power curve that you see on a dyno, it is the real world response time. ON a dyno they run the car at WOT from some low rpm giving the turbos a chance to start spooling early. Try running both of them at ~3000rpm at a cruise and floor both of them (real world situation of driving in traffic). The seq FD will pull pretty good nearly instantly.

Single turbos and non-seq have there place but the twins are really nice for the driving most people do. Lots of posers on here "mod the car for the track" but never get on the track. They end up with a sucky street car.

Jeff

johnchabin

iTrader: (2)

Well said. Made me laugh.

kwikrx7

I agree with turbojeff on this one, in real-world street driving and just pure pleasure, there is nothing like the sequential setup. There is a turbo simplification setup on rx7turboturbo.com that gets the sequential system down to 25 vacuum lines - might want to try that - you can remove the rack and all - I know SPOautos has done it if you want to PM him. There is no benefit to non-sequential except about 30 more hp from 4K-5K rpms but lag is very apparent. Full boost comes on in the best of non-seq FDs at 3300-3700 rpms. There's no transition at all but transition can be almost be eliminated by the PFC. I have always been a non-seq fan because it eliminates all boost problems and it's simple but power and responsiveness is down in the low rpms. Non-seq is more reliable as it creates less heat for the second turbo but I would only convert if you cannot solve your boost problem.

Ralgh

My Subie has just the one turbo and boost comes quickly. Yes I know different car different system.

I guess the big thing is what are you going to use the car for. My brother will use his almost exclusively on race tracks so low end won't matter. Plus most of his vacuum lines are hard and brittle which is giving him trouble.

Mine is a track car too but the sequential part is working just fine and I believe don't mess with it if it works. Especially on an RX-7

Drag racing and daily driving require different priorities.

rpm_pwr

A few quick points about NS:

You'll hear a lot of people say they get 12psi by 3750rpm. What they dont tell you is that this is generally in 4th. Ask them what they get in first/second.

The power/torque curves don't compare. I run the turbo solenoids with an aftermarket computer and can easily switch to NS. Sequential owns NS for power under 4000rpm and there's not much in it after that.

I'm dynoing again next week, I'm thinking about doing a NS pull just to post here

-pete

MMcrack

Sounds like its time for another bet...

hahaha

Ralgh

Ok but I'm not really sure what you are arguing here.

On the track you are almost never in second gear and rarely below 4000 rpm. Since he is open tracking his car, based on your statement, he will be better off non-seq. No drag racing here.

On the other hand my car works as advertized so I'm not changing anything.

Don't drive angry.