SQ-TTS Guide: Sequential, TTC, SQ/TTC Switching. Twins and Standalone ECU

[Mike2JZ]

 

Preface

As Supra’s get older it is not uncommon to hear of standard ECU’s failing, sometimes beyond repair. This will probably become more regular as time passes and presumably there will be a time where second hand ECU’s will cost so much that maybe going standalone might be viable as an alternative?

 

A common complaint from a lot of TT owners is that they would not like going to a standalone as it is not possible to run turbo’s in sequential mode and it was generally accepted that you would have to run in TTC mode if you used a standalone. Whilst this may have been true in the past, most popular modern ECU’s have the required hardware/software to support sequential turbo operation.

 

In addition to just running sequentially, I also figured out that by using some jiggery pokery of the ECU calibration, that it was also possible to switch between Sequential and TTC mode on the fly using a switch on the dash. This may sound familiar to the ETTC mod. In principal they are similar, however doing it through the standalone allows for a less messy install and allows you to switch between two separate turbo operations that have their own individual optimized boost, fuel & ignition tunes.

 

Having installed & tuned a few standalones on TT’s, where running sequential & TTC mode was a requirement. As a way of giving back to the community I shall explain in as much detail as possible how it was done, and how you could do the same for yourself/get a tuner to do it for you.

 

Warning: I do like to go on a bit, so incoming walls of text.

 

 

Disclaimer

I did not discover that sequential operation could be done via standalone. I am merely posting my processes & notes for other to learn from. Credits is given to Stu Hagen’s website resources, which gave me the knowledge required to begin with this adventure and opening my mind up to the idea that running sequential was possible on a standalone.

 

My testing has only gone as far as using Link ECU’s. I have not tested this with Syvecs, Haltech, AEM, Motec etc. Considering how competitive the standalone market is, I would be surprised if the same could not be achieved using any other popular modern standalone.

 

For the purposes of this guide, all technical talk will be in relation to the Link ECU. The principal will be the same across every ECU, though implementation will be slightly different. Happy to update the thread as of when I get to play with another ECU.

 

I will not take any responsibility for any damage you cause to your own engine/turbos. A certain amount of knowledge is expected and required to carry out the following modifications, not advisable if you cannot pick up a spanner, understand how engines work or have never worked with a standalone ecu. Please use this guide at your own risk. Be sure to test each modification safely. Using a trusted tuner to do this is advisable in most cases.

 

Back to Basics

 

Here’s a boring section going over the principals of the systems we are going to be playing with.

 

Another thread/website can and has been created about this stuff in more detail, this is just a summary of what I consider the most important bits to know about whilst playing with the sequential system.

 

How does the sequential turbo system work?

 

1. At low RPM’s all 6 cylinders exhaust gases are directed towards the first turbo, as actuators/flaps are shut. This is the first stage of the sequential operation and is what provides the low-down grunt.

 

2. Depending on what gear you are in and how much load is being produced at the engine, a transition period will occur around 3500-4500 rpm, which is where the second turbo comes online. Prior to this transition, exhaust gases will be bled off from the first turbo to start spooling the second turbo.

 

3. Shortly after, the exhaust & intake gases/air from the second turbo will be introduced into the exhaust/intake system. This transition is usually felt from the driver seat and can be described as a small dip in power followed by a surge of power.

 

4. Once the transition happens you essentially have 3 cylinders powering the 1st turbo, and 3 cylinders powering the 2nd turbo in unison until redline/gearshift.

 

 

 

 

 

 

How does the True Twin Conversion mode work?

 

At low RPM’s all TT valves/flaps remain open so both turbos are spooled in unison. Due to this, the turbo’s come on boost at the same time as a non-sequential twin system would (like a 1JZ-GTE non vvti).

 

The major trade off with this system is lag. Without 1 turbo being worked at low rpm, you will have to wait a small while for boost to kick in fully. You will have no low-end grunt, but power will be introduced more smoothly, like a single turbo. There is also evidence to suggest that more power can be had on the top end with this approach.

 

What are VSV’s & how do they control the turbo’s?

 

 

 

 

VSV’s are Vacuum Switching Valves.

 

In English they are a switch which can pass air (vac/boost) through them depending on if the valve is open or closed.

 

VSV’s have an input port and an output port, both connected to independent air hoses. VSV will normally open or close to allow pressure to pass through at a specific time to control something like an actuator arm or allow air to go somewhere where it shouldn’t be all the time.

 

From the factory there are 4 Vacuum Switching Valves (VSVs) that control the Sequential Turbo System.

 

WG VSV (Wastegate VSV):

This controls how much boost is regulated through either 1 or both turbo’s using a wastegate on the first turbo housing. It’s basically the factory boost controller. Though this could be wired up to be used with a standalone, however it is limited. It is better to take this opportunity to wire in a modern 3 port boost solenoid, which will allow you to boost higher if required.

 

EGBV VSV (Exhaust Gas Bypass Valve):

This controls when exhaust gases from the first turbo starts to bleed off to the second turbo to start pre-spooling it.

This a fun valve to play with. The earlier you open it up, the less power you make from the less turbo (more air bleeding off) but the less your transition feels like a dip as the second turbo is prespooled to a higher boost level (there is a limit to this). The later you open it, the more power you make on the first turbo, but the more noticeable the dip on transition will be as it takes longer to spool second turbo.

 

EGCV VSV (Exhaust Gas Control Valve):

This controls when the exhaust gases separate to those gases being bled from first turbo, can start flowing through second turbo.

This valve must be opened before the IACV valve is opened, otherwise you will either must wait even longer for boost to form, or it will not kick in at all.

 

IACV VSV (Intake Air Control Valve)

This controls when compressed air from the cold side of the second turbo can join the intake charged air system.

Generally, you want this valve to open very soon after EGCV valve. Not much gains to be had from delaying it.

 

 

Alright class over, back to how to get Sequential, TTC & SQ-TTS working

 

 

Sequential/TTC/SQ-TTC Requirements

What parts do I need?

• 2JZGTE Motor with sequential twin turbo’s (factory/hybrids)

• Healthy Sequential VSV/Vac Lines/Pressure Tank etc.

• Downpipes/Exhausts/Intercooler/Fuel Pump/Restrictor Ring if more power than factory required

• 3 Port Boost Controller (MAC/Pierburg etc)

• Standalone ECU

• Dash switch (Sequential/TTC Switching Only) or can used for boost map switching

• 2 Plug IACV / eThrottle / IACV delete (only required in some cases where not enough Aux Outputs available)

• Currently only manual transmissions supported, have not tested implantation on auto yet, but seems feasible.

 

Can I use a Plug & Play ECU or is a Wire-In ECU required?

 

Edited August 4, 2018 by Mike2JZ (see edit history)

[Mike2JZ]

Sequential/TTC/SQ-TTC Requirements Continued

 

Idle Control Valves + Auxiliary Outputs Conflicts & how this affects what ECU/setup you need

 

On most entry level Link ECU’s there are 1-8 main Auxiliary Outputs and several optional Aux Outputs designated to unused Ignition & Fuel drivers.

 

The main 1-8 Auxiliary outputs are the most desired Aux outputs to use as some can allow for high side outputs, and all 8 have advanced drivers that allow for high frequency support, or additional configuration options on Outputs.

 

The few optional Aux Outputs on unused ignition/fuel channels have basic output drivers in comparison which support lower output frequencies and basic output configuration.

So here is the problem on most factory setups wanting to run SQ/TTC switching with a factory IACV.

You will need 4 auxiliary Outputs to control 3 Sequential VSV’s and 1 for boost control. You will also need 4 auxiliary Outputs to control the factory 4 pin IACV. So that’s already your 8 most desirable output slots taken up.

 

Depending on your setup you may need to be creative with how you allocate your Aux Outputs as you will also need Aux Outputs for things like Speedo, Rev counter, VVT control, Check Engine Light, Fuel Pump Control, Engine Fans etc.

 

In some cases, you may just not have enough outputs to support everything you want to do. In this case, you have a few options:

 

• Run an alternative IACV valve like the PHR Ford IAC Adapter Kit for 2JZ-GTE. This IACV only uses 1 Aux Output, freeing up an extra 3 Outputs for other things.

 

• Using e-Throttle will also have more Aux Outputs left over as idle control is done through throttle and does not require an IACV valve.

 

• If push comes to shove, you could delete the IACV and use the throttle idle stopper screw to dictate your idle level, obviously not ideal in most cases though.

 

• Buy a high-end ECU that has a surplus of Aux Outputs that will give you more than you will probably need to use. Link Thunder would be an example of this.

 

• Compromise on some ecu functions and choose not to run as many (again not ideal in most cases)

 

How to get your VSV’s working with your ECU?

I am purposely not going to be talking about the basics of how to get a Link ECU running, I assume you know how to do this. We will instead focus purely on the two ways of getting your VSV’s working, depending on which ECU you went with.

 

Aux Output Pin Allocation for SupraLink PnP

The SupraLink PNP is a plug and play unit but does not support VSV control out the box.

 

To run the VSV’s and still retain most other factory features on the car you will need to be comfortable with a bit of plug repining and/or wire cutting/soldering/extending.

 

You may also have to sacrifice one of two features depending on what your requirements are, and how many Aux Outputs you have available. 1 or 2 Link Extension looms may also be needed if you need extra outputs to fulfil your requirements.

 

The 3 pins on the 2JZGTE loom that go to each VSV solenoid are unallocated on the SupraLink PNP ECU Pinout. The only way around this is to depin the 3 VSV pins on your loom ECU plug and swap them with any of the following aux output pins.

 

2JZGTE VSV Pinout Location & Functions

 

 

VSV 1 (B40) = IACV VSV

VSV 2 (B39) = EGCV VSV

VSV 3 (B38) = EBCV VSV

PMC (B60) = WG VSV

 

 

 

 

VSV Wiring for Wire-In ECU’s

VSV wiring is straightforward. Each VSV has a 2-pin plug connector

 

 

One Pin provides 12v from a switched power source which must be constant with ignition & engine running, the other pin provides a grounding signal from the ECU (Auxiliary Output)

The solenoid is not sensitive to which pin is positive or negative.

 

From the factory each VSV takes 12v from the Main EFI Relay output, as well as a signal ground direct from ECU. I’ve yet to see any issues with this approach so I replicate this wiring strategy.

 

VSV Testing

Once you have finished wiring/pinning in the correct wires to connect your ECU to the VSV solenoids, you can now test that the connection is correct.

 

As an example, if you have your IACV VSV connected to the Aux 4 pin on the ECU plug, choose Aux 4 from Link Software and copy the below settings.

 

 

You should hear your IACV VSV solenoid clicking. Go and physically check that the correct VSV is clicking and not another. If you are not getting any clicking, then you have wired it in incorrectly or have a dead VSV.

 

Do not set your frequency any higher than 20Hz for testing! Do not leave the solenoid in test mode for ages, do short tests.

 

Once you have tested all your VSV’s in this manner and everything is responding as it should, you are ready for the next step.

 

You must now decide if you want to run Sequentially Only, TTC Only, or SQ-TTC. Read the appropriate section below.

Edited August 6, 2018 by Mike2JZ (see edit history)

[Mike2JZ]

How To: Sequential Only Mode

Sequential Only mode means that the turbos will be working sequentially and there will be 1 fuel/ignition/boost map to control this operation. Pretty much a replica of how the stock ECU functions. Obviously, you can still run multiple maps for boost etc, but for the sake of this guide we will just say that sequential only runs 1 set of maps.

 

Whether you are running a P&P or Wire in ECU you will need to allocate 3 Aux Outputs to control the EGCV, EGBV & IACV VSV solenoids & 1 aux output to control your boost solenoid.

 

Your selection of Aux Outputs for VSV control can be from either the 1-8 Main Aux Outputs, or Unused Spare Ign/Inj Outputs! Using the spare Ign/Inj outputs will not support SwOffTimer functionality. It’s nice to have to protect VSV from being overworked in certain situation, but not end of world if you don’t have it.

 

Sequential VSV Configuration

Exhaust Gas Bypass Valve (EGBV VSV)

 

 

The logic above dictates that the exhaust bypass valve will either begin bleeding off air to second turbo when 3300rpm or 7psi manifold gauge pressure is reached.

 

 

Intake Air Control Valve (IACV VSV)

 

 

The logic above dictates that the Intake Air Control Valve will open when more than 30% TPS is used in conjunction with 3600rpm or more.

 

The 30% TPS requirement for IACV and EGCV is to help deter unwanted VSV activation whilst cruising/pulling away. The TPS variable could be changed for another condition but this seems to work pretty much like a factory car does.

 

 

Exhaust Gas Control Valve (EGCV)

 

 

The logic above dictates that the Exhaust Gas Control Valve will open when more than 30% TPS is used in conjunction with 3500rpm or more.

3 Port Boost Controller

 

 

With the BC aux output configured like this, you will be able to setup a boost map under boost controller settings.

 

Real Life Sequential Operation & Testing

With the VSV’s all configured, you are now ready to see if the turbo’s will work sequentially.

 

You should be able to feel if the turbos are doing their job. But just in case, you can log the following parameters.

 

You should expect to see very similar set of graphs to below whilst doing a pull from low to high rpm in 4th gear.

(Graph below uses boost control to make 0.9/1 Bar of boost for both 1st and second turbo, hence the dip at transition. Using stock boost levels will show less of a dip)

 

 

If your turbos are not reacting as expected and your Aux Output logging resembles the above, but the MAP graph is different then you most likely have a VSV or Vac Hose plumbing issue that needs rectifying.

 

How To: TTC Only Mode

TTC mode means that the turbos will be working together and coming online in unison. There will be 1 fuel/ignition/boost map to control this operation.

 

Whether you are running a P&P or Wire in ECU you will need to allocate 3 Aux Outputs to control the EGCV, EGBV & IACV VSV solenoids & 1 aux output to control your boost solenoid.

 

Your selection of Aux Outputs for VSV control can be from either the 1-8 Main Aux Outputs, or Unused Spare Ign/Inj Outputs! Using the spare Ign/Inj outputs will not support SwOffTimer functionality.

It’s nice to have to protect VSV from being overworked in certain situation, but not end of world if you don’t have it.

 

Please note that as we are electronically inducing TTC mode, there will be some lag time for all the actuators to build up enough pressure to open. The only way around this is to mechanically delete all the flaps/actuators on the sequential system or wire them open. This would be a semi/permanent modification, that will let the turbo’s come on boost mechanically. VSV’s controls would no longer be required through ECU. Google Permanent TTC mod if this is your cup of tea.

 

 

TTC Pinout & Wiring

If you are using VSV’s to induce TTC then see the Pin Out (P&P ECU) Or VSV Wiring (Wire-In ECU) section.

TTC does not require different pinouts or wiring for VSV’s. Only the logic controlling VSV’s will change.

 

TTC VSV Configuration

VSV settings are basically the same as sequential mode. Only now we want activation RPM’s for the VSV’s to be as early as possible (1500rpm is a good starting point). The quicker the VSVs are energized, the quicker all the sequential flaps open allowing both turbos to spool in unison.

 

Applying the logic below to your VSV’s will basically allow TTC operation to kick in when you give the car a reasonable amount of throttle. Interestingly if you are just pootling at low rpm/low load & only feather the throttle, you will still get a bit of first turbo kicking in to pull you around, which is cool.

 

Exhaust Gas Bypass Valve (EGBV VSV)

 

Intake Air Control Valve (IACV VSV)

 

Exhaust Gas Control Valve (IACV VSV)

 

3 Port Boost Controller

 

 

Real Life TTC Operation & Testing

(Graph below uses boost control to make 0.9/1 Bar of boost)

 

 

Here we can see that the VSV’s are energized in unison around ~1600rpm, where the TPS value goes above 30%.

 

The VSV graphs lines are overlaid on top of each other, so we can only see one line, but they are all on. Positive pressure starts building smoothly around 2500rpm, and both turbo’s online boosting hard at 3500rpm.

 

This run would have been a better model had TPS been at 100% from 1500rpm, but the above graphs are pretty much what you are looking to achieve running TTC mode.

Edited August 4, 2018 by Mike2JZ (see edit history)

[Mike2JZ]

How To: Sequential to TTC Switching (SQ-TTS)

We’ve now seen how to manipulate the VSV’s to run sequentially or TTC using a standalone.

 

Looking at the VSV control settings, there isn’t much between each mode of operation other than changing what RPM each solenoid kicks in. So, with that in mind, I figured there must be a way to change what RPM each solenoid kicks in, using a dash mounted switch to trigger the change in settings.

 

The LinkECU support team said this kind of setting switching was not supported, but with a bit of backwards thinking I managed to get another function reworked to fit the bill.

 

So previously we had been configuring the VSV settings by using an Axillary output channel with the function of “GP Output”. This is a configurable basic on/off switch that can output a signal.

 

However, there is another type of general purpose output which is only available on Aux 1-8 channels, known as “GP Output PWM”. This is normally used as an on/off switch that can output a certain pulse width which can be used to control various components that can take a varied input signal.

 

We aren’t really interested in the PWM aspect of this function, as the 2JZ VSV’s are only on/off. However, using the PWM function gives us a configurable table which gives us another dimension of conditions to play with.

 

SQ-TTS Pinout & Wiring

SQ-TTS does not require different pinouts or wiring for VSV’s. Only the logic controlling VSV’s will change.

 

However, it is very important now that you make sure you have your three VSV Aux outputs assigned to the main Aux Output channel (Aux 1-8), otherwise the ‘GP PWM’ function will not be available to select.

 

You will also need to add a dash mounted switch and configure this as a Digital Input on the Link.

 

The output of the switch should go to chassis ground, the input goes to the corresponding Digital Input pin/wire on the Link ECU Pinout/Wiring that you have elected to use.

 

 

 

 

TTC/SQ Switching VSV Configuration

As we are now using ‘GP PWM’ rather than ‘GP Output’, there will be a few extra fields you will need to configure. Importantly, you will also have a corresponding table that needs its X & Y axis to be setup as follows:

 

Exhaust Gas Bypass Valve (EGBV VSV)

 

 

For example, if you have your turbo operation switch assigned to Digital Input 2, then on your 3 VSV GP PWM tables, you will need to change the Y axis to use Digital Input 2 as a trigger to move between rows of the table.

 

The Digital switch is either On (1) or Off (O).

 

On the X axis, you need to have Engine Speed (RPM) selected. Don’t forget to add or remove new RPM points depending on when you want your VSV’s to activate. In the cells, either use 0 for VSV inactive, or 100 for VSV active.

 

 

Intake Air Control Valve (IACV VSV)

 

 

 

 

Exhaust Gas Control Valve (EGCV VSV)

 

 

 

3 Port Boost Controller

 

 

Real Life SQ-TTS Operation & Testing

 

 

So above is a nice log showing the switching in action out on the road.

 

The first pull the Turbo Switch is not active (0), and the turbo’s run sequentially.

 

Afterwards the Turbo switch is flicked on whilst driving and becomes active (1), other group of settings are used on the VSV controls and the next pull happens in TTC mode.

 

Result! I was super happy when I finally got this working. Super cool to be able to switch between modes depending on what kind of driving style I fancied from the comfort of the driver’s seat.

 

 

TQ-TTS Ending Thoughts

In the past people using the old school ETTC mod achieved a similar turbo switching technique, however running in TTC was never as good as it could be whilst on the factory ECU, due to the factory maps being optimized for sequential operation.

 

Using SQ-TTS you can now either map yourself or get your mapper to give you two optimized maps for sequential and TTC so finally you can have either mode working at its proper potential, especially if you have BPU mods which need a mapper to really optimize what you are running.

 

That one dash switch can trigger turbo operation, boost, fuel, ignition and several other cool maps depending on how in-depth your mapper goes.

 

Other than the cost of getting a standalone installed & mapped, this seems like a valid solution to get factory operation with all the cool features of running a modern standalone which hopefully will help some of you out there reading this.

Edited August 4, 2018 by Mike2JZ (see edit history)

[MRX]

Lots of useful info, thanks for taking the time to post mate!

[Samurai 20V]

Awesome stuff..

 

I've been one of those guys putting off mapping my stock twined car, this will help me make the decision for sure.

 

Appreciate the share!

[Mike2JZ]

Awesome stuff..

 

I've been one of those guys putting off mapping my stock twined car, this will help me make the decision for sure.

 

Appreciate the share!

 

I just remember that I completely forgot to send you a link map file with the sequential stuff on it. So hopefully the above makes up for that!

[Samurai 20V]

I just remember that I completely forgot to send you a link map file with the sequential stuff on it. So hopefully the above makes up for that!

 

No worries at all mate, that stuff is perfect.

I hadn't decided on an ECU, now I'm defintely getting the Link PNP.

 

I have the HKS EVC6 currently installed, you think I should remove it and let the Link control the boost or try and set it up with the EVC6?

[Mike2JZ]

No worries at all mate, that stuff is perfect.

I hadn't decided on an ECU, now I'm defintely getting the Link PNP.

 

I have the HKS EVC6 currently installed, you think I should remove it and let the Link control the boost or try and set it up with the EVC6?

 

Normally I run boost control through the link as it lets me create a boost map that can vary duty cycle according to rpm (or any other condition I see fit). Most boost controller won't let you do this, I can't remember if HKS EVC6 will. If it does then yeah you can still keep using it.

 

If you plan on running sequentially, then it is nice to be able to create a boost map which gives a certain amount of duty cycle for the 1st turbo, and a certain amount for when both turbos are online. As the duty cycle to make 1 Bar of boost on the first turbo won't be the same duty cycle to make 1 bar with both turbo's.

 

Most controllers will let you have an overall duty cycle setting, which does work, but does not give you as much freedom to run X amount of boost per turbo. This method works great for TTC mode though.

[Samurai 20V]

The EVC is one of the more advanced controllers, but still old tech.

 

It has an overall offset/duty cycle and a boost correction map/offset correction by speed or RPM as a function of throttle opening.

The limitation is the boost by gear is not known, so I get some overboost in the higher gears. Also the colder weather sees the boost creep up.

 

 

I'll change over to let the link control the boost and get the most functionality.

 

 

Thanks for all the help Mike!

[mellonman]

Mike that there is a great right up . Thanks for spending the time writing it up and sharing. This should be put into the tech FAQ as a sticky .

Great work

[SupraTRD_MK4]

Nice. It seems even more in depth explained than previous post I have read. Well done and keep it up mate

[Mike2JZ]

It's been a while but have an update.

 

Had an opportunity to try sequential & sequential/ttc switching using a syvecs recently. Can confirm it works a treat.

 

 

Using a combo of PWM outputs and Custom 3D tables, you can use the logic outlined in the opening post to make this work nicely on a syvecs. Even had the SQ/TTC switching feature working off Toucan touchscreen.

 

Need to get a hold of an AEM or Haltech next and see if it's do-able on those.

 

Edit: For anyone wanting to try this out for themselves using a Syvecs, please be aware that you will need 3 free driving low outputs. Depending on your Syvecs ECU & setup you may not have enough outputs available, in which case you will need to sacrifice some or buy an IO expander.

Edited January 17, 2020 by Mike2JZ (see edit history)

[alxns]

This is great stuff. It's been a while since I've looked into this... I was hoping years ago that someone would try making this work but IIRC it always involved some level of custom software/programming skills and a lot of wiring. I believe Stu "Twin King" Hagen used a Vipec on his hybrid GT28 sequential turbo Supra.

 

Plugin Link ECUs look great. I am definitely giving this a shot at some point. Combining this with a OBD bluetooth dongle would be interesting to see. I've been waiting for JF "ZF" Breton to have TOYOCOM OBD1 dongles back in stock. They offer custom inputs. I really want this to be my next project now. I would have to see how to make it work on export 2JZ-GTE engines (I have a euro spec). Aahh I have so many ideas flowing