ludeowner

If he is going to be doing it NS, then it shouldn't be that much harder then a single. I see where he mentions that he wants to run it NS, but his wording was kinda weird.

I was referring to a true sequential spool rate vs NS/single. But now we are talking about NS vs single since he is not doing true-seq. I would think that the spool rate should be pretty close.

EDIT: from what I've seen of the NS on FD's is that full boost is usually reached at 4K with a close to stock exhaust system. I think for open exhausts full boost was reached by about 3500-3800. I'ts been a while since I've looked at NS swaps though, so the numbers are probably off.

driftaholic

I think the ecu tell the vacume supply to switch on at a certian rpm/load

ludeowner

It's been a long time since I've looked at the seq control system, but IIRC the actuators are all controlled by pressure from the turbos (not vacuum). I might be wrong though.

Here is a thread that I started a while back. I wanted to understand how the turbo precontrol and WG control system worked, before I started messing with it. The only thing is it doesn't go into how the ECU plays a role in the seq control system.

https://www.rx7club.com/showthread.p...hreadid=216913

Kanaida

Running them simultaneously isn't going to spool all that fast really.... If you think about it, trying to spool two small turbos as compared to one big turbo would be about the same. The exhaust flow you get is going to be split in two to spool the twins at the same time, which would be probably as weak as all the exhaust flow forcing through a turbine of a large single. I'd think you're going to get equal lag either way.

But it would still be a fun project, and when completed, would be great for a show car if you can shine it up nice and pretty!

and by the way.. Simultaneous (Non-sequential) turbo chargers ROCK THE ******* HOUSE!!

Sesshoumaru

iTrader: (1)

It is done by ecu (stock)

Stock setup has the turbo precontrol using a soleinoid but can be replaced with a boost controller (pressure related then).

The wg is also ecu controlled. It cycles a solienoid at a set duty cycle. This can also be replaced via a boost controller (yes you can have two boost controllers-another pressure............ok so far )

then there are two solienoids for the turbo control. This is ecu related and uses pressure chambers.

The last one is charge relief for 2nd turbo (ecu controlled).

i'm doing the simplified conversion now and the only way u can seq is with the solienoids.

this systems allows the 2nd turbo to kick in at 4500rpm. If it was pressure related the driver wouldn't know when the 2nd turbo would kick in (varies day to day -cold,hot,etc). Alot of ppl crash around corners b/c oth extra 35hp or so catches them off gaurd. If it happened when ever it would be quite dangerous around corners (if not use to it).

btw sequential uses both turbos at the same time once it's out of sequential mode (4500 rpm). Just a better way of using them (they are identical in size)

Sesshoumaru

iTrader: (1)

This is what u have to deal with

NZConvertible

You don't control these things. Twin sequential turbos are no different in construction to two normal turbos; they just have valves in the manifold and pipework to control when they flow. If you wire open or remove all of the valves then the turbos work just like any other twin parallel turbos.

It doesn't work that way. Rotational inertia increases with the square of radius, so compared to a single turbo of equal flow potential, twins can spool faster even though each only receives half the exhaust flow.

If there was no advantage, nobody would have bothered with twin parallel arrangements, which have been around a lot longer than sequential set-ups.

No it isn't. None of that is there in a non-sequential set-up.

This really is a lot less complicated than people seem to think.

Sesshoumaru

iTrader: (1)

that would be non-sequential.

i'm talking about sequential.

non-sequential is just like a normal turbo. If you look at the manifold you can easily tell they are constructed differently than a non-seq twin turbo.

what would be the point in swapping if you didn't keep the seq?

NZConvertible

But the original poster wasn't.
No, they are basically the same as two single turbos, they're just mounted back-to-back to aid packaging.
See my post above.

Sesshoumaru

iTrader: (1)

they are exactly identical (hitachi HT 12 w/ 51mm 9 blade turbine and a 57mm 10 blade compressor)

If they were designed non-sequential the manifolds would be a lot different. The divided housings favor the 1st turbo greatly and the TC wastegate would not be needed in the 2nd divided housing.

if you can channel the same exhaust throw a narrower space it will create more velocity thus reducing lag allowing turbo to spool faster (garden hose when the end is squeezed- water shoots out faster). this is how they do it by using the TC.

an after market turbo would produce roughtly the same amount of lag compared to the non-seq if matched properly.

NZConvertible

I'll have to remember that analogy the next time I explain the S4's twin-scroll system to someone.
But that misses the whole point of the conversion. Find me a single aftermarket turbo and manifold and wastegate that flows as much, spools as quick and costs the same. You're talking about buying a new (and expensive) turbo and ancillaries. I'm looking at it as a cost-effective way to increase power without adding too much lag.

Like I said at the beginning, this conversion would only be worth it if you picked up the turbos for a good price and could do some/most of the work yourself.

Sesshoumaru

iTrader: (1)

i agree

J-Rat

iTrader: (2)

Post by driftaholic:

So whats esentialy needed is:

-another boost controler for the switching actuator and the turbos will run sequential based on boost presure (ie second tubo to kick in at 5psi)

-Custom pipeing to adapt the intake tract to the tubos in a Y fasion from the AFM.

-The outlet on the compressor side looks to be an easy fix to the factry location for the BOV and the TMIC.

-choped up FD downpipe mated to choped up FC downpipe.


The kind of questions I still have:

-How close will the FD kit be to te lower intake manafold?

-Oil and return lines? I have never seen these in person so I don't know where they come from or where they go, I am asuming that they will T into a single line and run roughly the same route as the FC lines.... mazda is cheap like that.

Anything I am missing? So far it seams like we have the stuff and skills needed between me (driftaholic), j-rat, carx7, and moremazda.

NZConvertible

It's not even worth thinking about sequential operation without using the stock ECU and solenoids. You have little to no chance of making it work acceptably with something as primative (relative to the ECU) as a boost controller. You only have to look at the schematic posted above to see that.
One custom pipe would seem smarter.
Oil is one supply that splits into two, with two seperate drains; I believe coolant has one supply and one return that both split to the turbos.

rx7joe

iTrader: (10)

No, it still needs a decent amount of porting or you'll get massive boost creep.

Greg

Rxmfn7

iTrader: (4)

Im really thinking about doing this as well.. I may sell my T04B hybrid and pick up a set of FD twins...then get to the modifications...

rx7joe

iTrader: (10)

-the twin turbo actuation is VERY complex, requiring pre-spool mechanisms to eleminate the loss of boost/torque when the secondary turbo comes online. A second boost controller will be ineffective at this. Plus you will have a huge dead area on acceleration. Trust me, those 75+vacuum lines are there for a reason.

-The FD turbos are VERY close to the LIM as it is and they will not clear a T2 LIM the last I knew. They would require a spacer which will push the downpipe further into the fram rails. My downpipe is pretty close, not as close as the FD clearance, but close. I'm not sure how big of a spacer is needed, but it will complicate things. I have an REW engine in my FC btw.

-oil lines run down from each turbo. The rear turbo drains into the rear side housing and the front turbo drains where the T2 does. I'm sure you could T them together with a little custom fab work, so I wouldn't worry to much about that.

-I'm not sure how you feel about emisions, but the ACV on the TII would stick out to far and most likely interfere with the twin piping out of the compressors.

My suggestions if you wish to continue with this project (though I agree it's not worth it), DO NOT try to run it sequential. It will be a headache and a half unless you are using a 93+ ecu to control it and then it's just way to complicated to switch onto a T2, though not impossible. The downpipe will interfere with the firewall with a spacer, mine did enough without any spacing, however a good exhaust shop should be able to get it pretty good.

There will be some gain over the stock t2 turbo such as marginally higher boost levels, though like many have said, running non-sequentially probably won't gain you much in the lag department. Another note is that because the twins are so small, they create an enormous amount of backpressure (compared to conventionaly sized turbos) and therefore generate a higher heat load. not impossible but something to think about.

Keep us updated with how things go.

RETed

Boy, people spit out a lot of bullshit when they haven't even tried it.

The FD twin turbos HIT the stock lower intake manifold on the FC3S 13BT.  If you try and grind down the lower intake manifold, you'll end up with HOLES in your lower intake manifold.  YES, it is that close.

The stock FD3S stock twins are a piece of **** - maybe you guys need to peruse the 3rd gen section to go find out how bad these things are.  The tend to puke their seals even more readily than the stock FC3S turbo.  They still run stock carbon seals, which will limit boost to 15psi - running more boost for a long amount of time will reward you with shattered carbon seals.  You should also price how much to rebuild those turbos - it is not cheap.

If you think you're getting away cheap because you're getting a used set for a good price, think again.  I put money those turbos are puking oil and need to be rebuild.  Try and price a rebuild for those things, and for the money you could've gone single turbo and making 400hp+.  Almost every set of twins I see come off an FD is puking oil - this happens almost 90% of the time.

fc3s.ORG sells their T04B turbo for ~$500!
HKS cast turbo collected manifold for under $300
Everything else is custom pipes and hoses
You could, in theory, pump out 400hp at about $1,000...

To me, those things are a waste of time.  There are probably more FD's with single turbos than with the original twins.  There's a reason for that - think about it...



-Ted