OK I am trying to figure this out..

I was told not to run the twin scroll..
I was told all I had to do was not hook the vac line up to the TS actuator

what I am curious of is..

with the actuator not working is the flapper closed off right now only allowing for one exhaust port to blow or is the flapper in the "open" position which should be giving me max boost?

 

If I pull the turbo off this is what u would currently see




does this mean that right now I would be at full boost or not?

 

I believe it is closed. If you dont want to remove your manifold, you can wire it open. I removed it when the manifold was off, the bushing for the flapper was easy to break on mine. Once the bushing was driven in, the flapper arm came right out. Tapped the hole 1/4" I believe, (may have been 1/8") and put in a plug.

 

ok so right now I am only running at partial boost?

 

That is open...just saw your pic.

 

ok so right now I would be at full boost then

I take it the way it works is if it was hooked up the arm would flot up and cover half of the opening

right now it is considered open and getting max flow?

 

Yes. You are correct. I am just wondering what is holding it in the open position? When I got mine the actuator was removed and the flapper was wired open. If you have the time remove the flapper. One less thing to worry about.

 

the actuator is holding it open... the way I understand is IF I had the vac hooked to the actuator when I start the car the vac would pull the actuator arm in so it would close... then as vac went away (via boost) the arm would extend back allowing it to open up..

 

Yes, the actuator is holding it open. If the flapper and actuator is working, I don't see why you want to disable it. You will boost normally, but it may take it a little longer to spool.

At low loads (vacuum in the manifold/actuator) the actuator pulls the flapper shut, directing all exhaust through one port, which allows for higher velocity at a certain angle on the wheel, helping keeping it up to speed. Start opening up the throttle, vacuum goes away and the flapper opens.

 

I dont have it functioning.. dont want it functioning.. I'm happy

 

So basically it help spool the turbo quicker, right? Or just helps keep it spooled on shifts? I guess the only reason for removing it would be if you have a aftermarket single scroll turbo?

 

You could go S5 and scrap the twinscroll all together. Plus you have a bigger wastegate. All you need is the manifold and turbo hotside. This link will show some pics of the 2.


https://www.rx7club.com/2nd-generation-specific-1986-1992-17/twin-scroll-removal-746913/page2/

 

and the turbo to manifold gasket and he manifold to block gasket and the downpipe for a S5 (or are the down pipes the same for S4 and S5)

 

and S5 oil drain and oil feed and coolant lines right?

 

That was the theory, smaller passage equals hotter faster exhaust charge at lower RPM.

I don't believe it did much on shifts.

If you bought an aftermarket turbo it probably won't fit on that manifold. Almost always you need a different manifold wen upgrading turbo's, with the exception of hybrid ones.

IIRC, the twin scroll worked better in theory than in practice. There is really no downside to removing it, and without it there it could give slightly better airflow (probably not noticable on any level though). For the most part it simplifies things and makes sure that the flapper won't get stuck closed for any reason, which would cause a loss of power.

 

ARRRRGH, this thread makes my head hurt. I'm not an expert, but I do know twin scroll is worth using (on S4 TII. S5 TII has the twin scroll built in, there are no solenoids or such controlling it). I have ~1500 miles on my streetport rebuild and I'm currently running stock boost. The other day, I ran 7.65 0-60 and 17.0* 0-100, and that was with the twin scroll inactive because the banjo bolt was broken (no vacuum leak, I stuck a solid bolt in there). Yesterday, a nasty afterburn blew out my turbo to mani gasket (meaning that even after tightening the turbo down over the remnants, I cannot boost quite as well as before). Today, I tightened the turbo down and also fixed the twin scroll banjo bolt. Under pretty similar engine temp, weather conditions, and same place as that prior time trial, I ran 6.8 0-60 and 16.1 0-100. Both times had basically identical shift points as well, and while I think my technique improved slightly since the last time, there's no way I overcame less boost to get such better times.

In short:
A tad less boost, especially up high, yet with the twin scroll active, the car is faster. Use your twin scroll, it is completely worth it.

Oh, and today, after fixing my twin scroll? I squawked the tires twice going into second gear from high in first. I was never able to do that before.

*edited for posterity. somehow I knew what I meant to type, but completely failed the delivery

 

What I did with my TwinScroll was completely pull the flapper door out, weld the bolt hole shut and port matched the turbo runners. a little laggy at first but overall way more flow.

 

^^^ Probably best for higher RPM focused driving?

Long story short though, no matter what you do to the stock exhaust manifold it's fairly inefficient.

 

Drove fine all around...

My stock TII with the Twin Scroll still intact feels a tad less laggy.

 

I'm not saying it wouldn't drive well at all RPM's, I just figured any performance gains would be seen more toward the high end.

 

I removed the flapper on mine. Not much point to boost in rpms low enough to trigger the flapper to close. Your power is higher than what the twin scroll helps. In 3rd gear at about 50mph, I can go from vac to boost in a second or two. Just take a moment to examine the exhaust flow from the front rotor around the flapper. It just hinders the flow.