Hi all. Just hooked up my twin scroll (had it capped off at the twin scroll and the lower front vac nipple on the throttle body) and Im getting some weird issues. My boost hits FAST now, like tap gas and its boosting, but also I am hitting my fuel cut (hit 11 psi, my boost gauge holds peak) even in first gear! I have a line going from the twin scroll to the front bottom nipple of the throttle body, and I have the check valve pointing the direction from the twin scroll to the TB.

My question is ... Do I need to install the twin scroll solenoid? IS that why im getting such bad boost creep that I dont get with the twin scroll off?

Thanks.

 

correct me if im wrong, but if you didnt' use your twin scroll, one of your rotors isnt' flowing air to your turbo. sounds like a terrible idea to me

 

Now you have the boost creep that everybody gets. See this writeup on porting the wastegate.

http://www.aaroncake.net/RX-7/s4wastegate.htm

 

There is a check valve on the twin scroll line? Mine doesnt have one... either way Id say you need to keep the twin scroll. The boost creep can be fixed by porting the wastegate, otherwise your the only person Ive heard complain about fast boost.

 

I already ported my wategate, and no, having your twin scroll does not only run the turbo off 1 rotor. You are wrong.
Thank you.

I guess I have no choice but to take the twin scroll off again. Args ... or do the extreme wastegate porting..... whats weird is my friend runs 10 lbs all day, with the same ported wastegate and he has NO creep... *confused* He has twinscroll also.

 

triplicate threads merged.. and edited...only post one thread per subject... tweak- you should know better

 

i dont think he was trying to... and Tweak, Im still a bit confused on some things. Why did you remove the twin scroll in the first place? and what makes you think its the problem? Im not so sure the twin scroll could cause boost creap. As far as i know its just there to assist in faster spool...

 

The server (as always) crashed twice during my posts, and I was unable to edit / delete the previous posts. At the same time, Im excited that you know me.
Sorry that it happened though. I REALLY wish they would fix the servers.

And FCKing1995 - I didnt mean "remove", but I did just cap it off before when I Was having engine problems (Still am ) to eliminate it as a vac leak. I consider it a problem, when I have the twin scroll plugged in, I hit the gas in second @ 35 and 1 second later my boost gauge is flashing and blinking at me that Im at 8 psi, and then fuel cut hits. I unplug the twin scroll and I can sit @ WOT in 3 or 4th even, and hold 5 PSI ALLLLLLLL day. I just think I have something plugged in wrong, or I need the solenoid or something .... *Shrugs* I donno.

 

They are attempting too, but there are so many users with 1000+ PMs (including sent PMs) as well as so many long term dumb threads (like the board at work ones) that it is making it hard to do.

Make sure you clean out your PMs (including sent ones) so that you retain less than 500 PMs and when they reset the servers you will find a whole new board.

 

I am thinking that my twin scroll might not be opening up at the higher RPM / PSI, causing the air velocity to go crazy high and continue to cause massive amount of boost the even a ported s4 wastegate cant handle? Is that an option? Its closed when it sees vacuum, and then opens when it has no vacuum (but wont ever see boost because of the check valve)? Correct? What does the solenoid do?

 

The vac line should go from the manifold (top or botton nipple on the front of the LIM) to the check valve (arrow pointing to the manifold) to the solenoid valve (oriented as per the FSM schematic on page 4B-53) to the actuator. If any of this is wrong, the system won't work.

YES! NO SOLENOID VALVE = NO WORK.

No, something else has happened. There is no way the twin-scroll system can increase boost. No way, no how.

No, a closed flap would severly restrict the high-rpm breathing, and cause a boost and power drop. But this doesn't matter because...

You need the solenoid valve! I don't know how you expected it to work without it. The flap will simply open as soon as you put your foot down no matter what the engine speed is, which is pointless. And the check valve is there to keep the vacuum in the actuator when you put your foot down. The solenoid releases the vacuum to atmosphere at the correct rpm and the flap opens.

The flap is sprung open, and the system closes it. If the system isn't working the flap stays open. Lag is increased, peak power is unaffected.

 

Ok guys just an upgrade, I put the solenoid in there, and now everything is all good. Holding 6 psi all day, got the super fast spool, everything is awesome. Now I just need to figure out if I can put my stage 2 ceramic NA clutch in my t2. The normal clutch slips @ WOT over 5k rpm. Args. If my NA clutch fits, I know it can hold the power, its a NICE clutch.

Anyways, thanks guys for the help. It was weird how it was overboosting when it didnt have the solenoid. Im going to guess its cause it closed the flap the whole time, even high RPM, and the air velocity was just super high. Also my higher RPM power is back. Although I hate to use it cause I have a bad oil seal and I smoke anytime past 3800 RPM.
I guess because the oil pressure jumps up at 3800 rpm or something and forces it past the semi bad seal.

 

NA clutch will not fit in a T2

 

Congrats on fixing it. Now I have a request/question When i was putting all of my stuff back together after replacing all gaskets, I broke the banjo bolt at the side holes. SO instead of finding a new bolt (tough work) and reusing the hard line, I clamped a vacuum line to the remained of the bolt shaft and screwed it into the solinoid. Works fine it seems, but what is this check valve Im hearing of? Anyone have a picture of it? I cant recall seeing it before i took apart the engine, nor when putting it back together. I have the vacuum line running from the solinoid to the lower nipple on the front of the UIM. Is that ok? WHy must it be on the LIM? Thanks

I see it on the fsm, but where was it located? I know about what to look for. i guess I will go to my leftover parts box tomarrow and see if I see a check valve laying in it somewhere. Perhaps I overlooked it. If thats so \/

Also what effects will no check valve have? non operation of the twin scroll? Seems to not have any problems with lag, Im at full boost in all gears by 3500rpm give or take 250rpm...

 

I dont understand what the check valve does either. All I could think is it wouldnt allow boosted pressure to push the twin scroll open faster...

 

Now that I've thought about it a bit more, that probably is what was happening. Because you had the check valve in but not the solenoid, the very first time you started the engine after connecting it up like that, manifold vac would've sucked the flap closed like and the check valve would've held it there, just like it's supposed to. But with no solenoid there's no way for the vacuum to be released. It might had stayed like that the whole time since then, or air might have leaked in overnight to open the flap and then been sucked out the next time the engine started, closing the flap again. This would result in a boost spike, then a drop in boost and power.

Oil pressure should rise smoothly with revs until the pressure relief valve opens. It should've jump up suddenly.

My bad, I meant UIM. But without the check valve it won't work any way, as I explained in my post above.

Again, see my post above.

Third time, see my post above. Didn't you read it before posting?

If you search the 2nd Gen section for post by me containing "twin scroll" or "twin-scroll", you'll find dozens of posts where I tried to make it as clear as possible that if the solenoid valve or check valve are not installed correctly, the system WILL NOT WORK. If they weren't needed they wouldn't be there. If you're reinstalling the system after removing the vac rack, wouldn't you check to see if you're doing it right by looking in the FSM or searching the forum?

Let’s clear this up once and for all then.

The twin-scroll control system comprises a vacuum solenoid valve, a check valve, and a switching actuator connected to a flap in the exhaust manifold. The switching actuator has a spring in it that normally holds the flap open. This is how it sits when the engine is off.

The solenoid valve is a three-port valve, which means it has a Common (C) port, a Normally Open (NO) port and a Normally Closed (NC) port. The switching actuator is connected to the C port, the intake manifold is connected to the NC port (via the check valve) and the NO port is open-vented through a small filter. When the solenoid is de-energised air can flow between the C port and the NO port (i.e. between the switching actuator and atmosphere). When the solenoid is energised air can flow between the C port and the NC port (i.e. between the switching actuator and the manifold).

When the ignition is turned on, the ECU energises the solenoid and the NC port is opened, which connects the switching actuator to the intake manifold. When the engine is started manifold vacuum is applied to the actuator, which pulls the flap closed. Because the check valve is oriented so that air can only flow from the manifold to the solenoid, this vacuum remains trapped in the switching actuator regardless of changing manifold vacuum. The flap will be held closed for as long as the engine is kept under 2,700rpm.

When the engine speed does reach 2,700rpm, the ECU de-energises the solenoid and the NO port is opened. This releases the vacuum in the switching actuator to atmosphere, and the spring opens the flap, exposing the turbine's second scroll to exhaust flow. The next time the engine speed falls below 2,700rpm, the ECU re-energises the solenoid, vacuum is applied to the switching actuator, and the flap is closed again. This process repeats every time the engine speed rises or falls through 2,700rpm.

Does that clear things up?

 

******Does that clear things up?************8

Trust me, you'll be posting the same information within a week. Maybe not on this thread, but you'll be posting it again. Just save the answer above and cut and past the next time on the *next* thread. humor

Hmmm. And in my head I thought it was 2800 rpm as the trip figure b/t vacuum and no vacuum. Oh well.

Basically the twin scroll is bullet proof. If the solenoid fails or a vacuum line leaks, the thing fails to the wide open positon. That means full boost is available even if those parts fail. It will just spool up a tad later than if the system worked as designed.

At one point in reading this thread, I would have bet that the twin scroll actuator was getting confused with the wastegate actuator. Silly thought.

 

Well the reason I asked again was I was confused, as mine doesnt seem to be spooling later, and if it is, its only by maybe 200-300rpm, if that much. Hard to tell if it was working or not. I wasnt excactly 100% sure on what the check valve was for, or the complete operation of the Twin scroll. So I reasked to be 100% sure that i understood, so I wouldnt be one of the people reasking later Thanks for clearing it up though. Ill go see if I can dig it out of my parts box, if its still in there. I guess it was once housed somewhere in the mess of vacuum lines and wires under the UIM /throttle body? Guess it will now be located somewhere in front of the engine, as my line now runs past the OMP, and then to the front lower nipple on the UIM

 

FSM page 4B-5. It's labled.

 

Im guessing its the small one labeled under the picture of the Twin scroll solenoid? That picture doesnt exactly make it hard to trace the routing of hoses. BTW, what is the other check valve in that picture for? the one that plugs into the turbo inlet piping? I have forgoten what it went to and that picture is again no help

Unrelated, i noticed a few pages down it says the specs on the turbochargers boost pressure is 6.56psi... what is up with that?

Also, after thinking about it more... I no longer have the check valve or solinoid valve installed, so I guess having the hose running the the manifold is pointless anyway, is it not?

 

Correct.

You mean doesnt exactly make it easy to... I imagine it's much easier to follow in an original manual rather than the low-quality scan available online. You can't really complain about a free copy of a $150 manual though.

PCV system, FSM page 4B-88. It's a relief path for when the manifold's positively pressurised (i.e. boost).

What's wrong with that?

Correct. The flap will be open with manifold vaccum is high, and close when it's low, i.e. as soon as you put your foot down. This won't help with spool at all, because it'll be open when it's beneficial for it to be closed.

 

Replies above ^

 

No, otherwise that's what it would say.

 

Well why does everyone always say stock boost is 5.5psi? and my gauge also reads 5.5psi... never heard anyone say stock boost is 6.5psi?

 

^^Repeated Missinformation.... Original systems degrade^^