V8KILR

Interesting article. I'll read it in more detail later on. However the table 1.2 on page 40 (42 in the article) that shows the 7 different options that they considered does not have my setup described, so it's still a unique design to my knowledge and is not discussed in that article. Not true. The swing check valve lets flow from the #2 turbo through as soon as it exceeds pressure at the other side of the check valve. This is exactly how the 2JZ-GTE setup works with the reed valve. Also my pipe merge design in post #46 should allow the flows to merge much sooner then the 2JZ-GTE setup does. What they said is: "However, the series-sequential system has a narrower flow range because the entire mass flow has to go through both compressors." They are actually talking about the compression side of a compound setup and mine doesn't do that as the compression side is not compounded. This is also not true for my design on the exhaust side either as the two 60mm wastegates on my system bypass exhaust gas around the turbines to prevent that very problem. As my compound setup will extract more exhaust energy then a parallel or sequential setup possibly can, it will overcome the inertia at lower rpm.

By running the two turbos in series on the exhaust side, I'll be able to extract more energy from the exhaust system versus running them in parallel. For example if one turbine can extract 60%, then two in series can extract 84% (60% + (40% x 0.6)). This means the #2 turbo will spool quicker as the turbines are extracting more energy from the exhaust system. The exhaust part of my setup is basically the same as the Boost Logic setup and they got 20psi at 2800rpm from their ~50mm #1 turbo. My #1 turbo will spool very quickly as it has a proper 6 into 2 divided manifold which is utilizing the exhaust pulse energy which the BL system did not. To make it spool even quicker, I plan to re-use my existing divided manifold QSV on the #1 turbo to add another 4-500rpm of spool as well. Both these will result in much more exhaust gas at lower rpm, which will also help spool the #2 turbo quicker.

Thank you all for your condolences and kind words. I will pass them on to Lindsay's family and friends.

The red Supra belonged to my best mate Lindsay. Sadly he passed away early this morning. :(

With the design pretty much finalized, the steps I see this setup should transition through are: 1. When running off boost the engine will draw airflow through both turbos with the majority coming through the #1 turbo. The EGCV is open and all wastegates are closed. The swing check valve (SCV) will be partially open due to vacuum from the engine. 2. As the #1 turbo transitions onto boost the airflow will switch to all going through the #1 turbo. The EGCV is still open and all wastegates are closed. The SCV is probably now closed. The #2 turbo is still just idling. 3. When the #1 turbo reaches 7psi boost, the EGCV will close and all wastegates are still closed. This will increase the exhaust flow through the #2 turbo which will now start to speed up. The #1 turbo spool speed will decrease in the rate of increase, but it will still continue to increase boost pressure. 4. When the #1 turbo reaches around 15psi, the #2 turbo should start making boost. The EGCV and all wastegates are closed. The SCV may start to open shortly depending on how quickly the #2 turbo boost pressure backs up in the #2 intercooler pipe. A small amount of flow from the #2 turbo may then pass through the SCV. 5. When the #1 turbo reaches 35psi, the #1 wastegate will be opened under ECU control. The EGCV and #2 wastegate are closed. The SCV will be partially open. 6. When the #2 turbo reaches 35psi, the #2 wastegate will be opened under ECU control. The EGCV is closed. The SCV will be fully open. 7. Win the race I was just having. Now all I need to do is to save the estimated NZ $10k needed to implement this system.

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Here's an updated design drawing based on the feedback from this and other Supra forums. The modified factory 54mm EGCV is always open until the #1 turbo boost reaches 7psi. This is to help spool the #1 turbo. The 65mm swing check valve is to stop reversion from the #1 turbo flow back to the #2 turbo. This replaces the reed valve and the IACV as it operates automatically and doesn't require any ECU control.

In case the idea above does not work, here is the backup plan. The IACV and the reed valve are really just one way valves but the IACV requires complicated ECU setup to control it. A far better way that requires no ECU control is to use a "swing check valve". e.g. Edit: Here is a better non-surge design: http://www.asiawaterbusiness.com/images/img_library/Untitled_1-6807.gif Using a valve like this will result in very low flow and pressure losses from the #2 turbo, probably not much more then the butterfly from the IACV does anyway. Without the need to control the IACV, the ECU setup has just been simplified by 90% and all that's now needed is two wastegates being controlled by the ECU. This has got to be the simplest sequential setup ever!

FYI, the second turbo in a diesel compound setup to receive the exhaust gas is often the large one. That's how they are normally setup. Compounding the exhaust flow works perfectly fine on petrol turbo engines. Boost Logic have done it and so have others and they all worked great! There is no question that the exhaust compounding part of the design will not work. What's wrong with the "jet pump" idea? It was invented in NZ after all.

Does this make sense as to why I hope to be able to get a lower pressure in the #2 intercooler pipe when the #1 intercooler pipe is at 35psi? A = #1 intercooler pipe B = combined intercooler pipe just before intercooler C = #2 intercooler pipe "As air is ejected from nozzle A, it mixes with the air in the tube at B. Imagine that the air from the nozzle mixes with two times as much air. Momentum is conserved, so this cloud of air, now two times as much as came out of the nozzle, is now moving at one half the speed of the jet from the nozzle. All that air moving to the right requires replacement air to be pulled in from the left. So we now have suction at C." The page that explains this is here: http://woodgears.ca/physics/venturi.html I would do this just as the two pipes join going in to the intercooler. This means there will be two, 2" pipes from the turbos combining into one 3" intercooler pipe. This will give twice the air volume for the 35psi air from #1 turbo to push along and create a pressure reduction in the #2 intercooler pipe. If this works, then air from the #2 turbo may be pulled through the reed valve at quite low pressures resulting in the #2 turbo creating air flow for the engine, even when it is at low boost compared to the #1 turbo. Just had a crazy idea. If it did work like this at all times (like a one way valve), that means I could eliminate the reed valve and the IACV altogether!

Probably, but it only needs to be 1-2 psi lower for it to not effect the IACV control. Edit: as long as there is a good high speed flow of air through the #1 intercooler pipe then it shouldn't matter what the psi is. E.g. If flowing 600cfm through the 2" intercooler pipe from the #1 turbo, then air speed will be 458ft/sec at 14.7 psi, which I'm guessing is around 190ft/sec at 35psi. I was thinking of joining the flows like this with the #1 turbo flow being the straight down pipe: http://www.industrialplasticpipe.com/pages/images/35129p.jpg

My first thoughts were the same as yours, but then I realized that the pressure on the other side of the IACV will not be 35psi despite the #1 turbo producing 35psi. If you type in "use air compressor as vacuum pump" in to Google, you will see my reasoning on this. Basically it comes down to the design of the merging pipes and using Bernoulli's principle to ensure the pressures are lower (venturi effect) in the #2 intercooler pipes between the IACV and the intercooler.

No replies on my IACV thoughts! Does that mean everyone thinks the IACV idea will work?

All very good points. Agreed, it's only a compound setup on the exhaust side. Using secondhand exhaust energy is how any compound diesel system works so that should be okay. This setup also gets firsthand exhaust energy that bypasses the #1 turbo once the #1 wastegate opens so it should spool the #2 turbo better then any diesel compound setup would. Also the #2 turbo is the same size as the #1 turbo, so easier to spool then a larger #2 turbo in a normal compound setup. I might not have mentioned it on this thread, but I have added an exhaust bypass to my design (using an altered factory EGCV) to bypass exhaust from the #2 turbo (rather then using a more complicated way of holding the #2 wastegate open) so as to improve the #1 turbo spool. This will mean the #2 turbo will only be idling (and not making any real flow) until the EGCV closes when it gets around 7psi boost from the #1 turbo. At that time there should be enough exhaust energy to start spooling the #2 turbo, so that it can start building up enough pressure to open the reed valve. I don't think you need similar flow while the #2 turbo is spooling as that's how a reed valve works. All you need is the same or higher pressure from the #2 turbo to be able to join the flows. I guess that will come down to tuning and how quickly the two wastegates and IACV can react to the TPS changes. If either of the two wastegates fails then it would over boost the associated turbo but this would happen on most turbo setups. If the IACV fails then #2 turbo will stall once it reaches the max psi it can create for the exhaust pressure it is getting.

The only part of my design I'm not happy with is the complexity of controlling the IACV. Toyota used a 3D map with engine speed (rpm), vehicle speed and throttle position as the three axis (axes) for controlling their IACV. The 3D map method seems to be a very complicated way of calculating the load on the engine and this makes for a very complex tuning requirement for a one-off setup like mine. So, in line with the general theme of keeping my compound sequential design as simple as possible, I've been thinking of a way to reduce this complexity. The factory setup seems to use the reed valve as a simple way to let the flow from the #2 turbo through to the intercooler until there was sufficient flow from the #2 turbo, that it could then completely open the IACV in one single step (is this correct?), or in other words the IACV is either open or closed. Perhaps a simpler way to do this would be to control the IACV at all times as if it was just like a wastegate, which would only require a closed loop 2D map. The steps I see are: 1. The #1 turbo is making full boost of 35psi (taken from the #1 turbo compressor outlet) and the #1 wastegate is opening (under 2D closed loop control) so as to maintain this boost level. 2. The #2 turbo should only be making around 20psi (taken from the #2 turbo compressor outlet) at this point (assuming an initial 15psi lag) but because the IACV is closed, pressure quickly builds up and reaches 35+ psi. 3. The IACV now starts to open (under 2D closed loop control) just as if it was a wastegate set to 35psi (taken from just before the IACV). However it only needs to open a little bit at this stage as flow from the #2 turbo is still quite low. 4. As the #2 turbo continues to spool up, the IACV will be opened more and more until it is 100% open, so as to keep the boost from the #2 turbo at 35psi. 5. Once the IACV is fully open, the #2 wastegate control is now activated (using a physical or virtual switch activated by the IACV reaching 100%) as it now needs to take over boost control of the #2 turbo. 6. The #2 wastegate now controls the #2 turbo at 35psi boost (while the IACV is 100% open), until easing off the throttle occurs. Then everything resets waiting for step 1. You have probably realized that I have not mentioned the reed valve at all in these 6 steps. This is because it is now redundant and can be completely replaced by the wastegate type control of the IACV, which is acting exactly like it is a huge reed valve. This means I could use the Turbonetics Newgen (or other type) wastegate in place of the factory IACV as it would probably allow finer control. Edit: Thinking about the reed valve a bit more, there may still be a small need for it under certain conditions, so probably a good idea to leave it in the setup as it works automatically anyway. Can anyone think of a reason why this simple 2D closed loop control of the IACV would not work?

Checking with Google, a CBV is exactly the same as a BOV so they both operate when the throttle is closed and vacuum occurs in the intake manifold. I think that the reed valve that comes with the factory IACV is all thats needed for a sequential setup.

Yes, I guess that makes very little difference if it recirculates as there is not really any vacuum in the compressor inlet. I think it would be heating the intake air a bit though, but recirculating may be a legal requirement in some countries.

No, if I did do this it would just be vented to atmosphere and with the #2 wastegate fully open there should not be much drive pressure anyway. Also, I would close it either before or at the same time that the #2 wastegate is closed, so that there was no risk of overspeeding. As Toyota did not see the need to do this with the 2JZ-GTE, I'm not convinced yet that it is necessary to do this.

Good thinking. It's also a thought that has crossed my mind as well. Toyota didn't use one on the 2JZ-GTE sequential system (because of the reed valve) so I'm not sure if it would be necessary or not which is why it has been left off the diagrams. Its very easy to add a very simple boost controlled compressor bypass afterwards if needed. Here's a pic of what I could use (by rotating the lever on the shaft 90 degrees) to do the job. https://jonbondperformance.com/images/TJ%20bypass%20assembly.JPG

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Thanks. I'm planning on doing closed loop for each wastegate based on the boost pressure feed directly from each turbo's compressor housing. I guess if that fails, I could try setting it up to use turbine speed. I'm thinking the IACV control (which probably needs to use 3D tables) will be even more difficult to get right for all driving conditions.

You make some very good points regarding the effects of the turbos on each other. I think it will come down to how quickly and how finely the ECU can control the two wastegates. If not very well then there will be boost cycling but if they can both be controlled very well the boost cycling will be very minimal. Anything less than 1/2 psi would be fine. Only testing will tell for sure.

The purpose of the two wastegates is to control the boost from each turbo seperately. Why do you think the wastegates will not be able to do that?

The BL setup requires very extensive tuning to get it working correctly, also according to BL. Basically I cannot see it working correctly without using two 3D maps, one for each wastegate and then another 3D map for the intake air control valve (IACV). That's all fine for BMW to do as they are doing it once for thousands of identical engines, but is very complex for tuning a one-off system. I believe this is why BL never offered it as a kit. Mine will need a 3D map for the intake air control valve (IACV), but the wastegate controls in my design are very simple in comparison, only requiring the normal 2D map.

I haven't seen pics of it either, but on one of the forum discussions, BL mentioned that they had to do this. Here is a quote from that discussion: "The max power issue has been resolved, a third wastegate was added to the charge pipe between the large turbo and the small turbo that will vent the charge directly to the intercooler pipe (bypass compressor housing of small turbo)." Edit: see post #70: http://www.supraforums.com/forum/showthread.php?548363-Compound-Turbo-Kit/page2 Yep, that's why I had already edited my original post to add "(on the compressor side)".