Sequential Turbo Setup question

[Drftn280zxt]

(this is not for a Z but thought you guys might be able to help since some of your have some pretty crazy things going on with your engines as far as turbocharging go's)

 

think 2JZ-GTE engine

 

I have a somewhat awkward question. As we all know the the Supras had the option of a turboed model. Of which was a sequential setup. Has anyone every created another type of Sequential setup. Here is my first idea. Two turbos (obviously) one small one large, two exhuast manifolds, two wastegates, and the two turbos. Plumb the "cold side" of the small turbo to the cold side input of the big turbo. The second exhuast manifold just feeds the big turbo, the bypassed gas from the first turbo would be fed into the a pipe that would koin exhuast gases from the other manifold prior to the second wastegate and also help spool the big turbo . Obviously after all pressurizing the air would be intercooled. What is your take on this idea. Inefficient?

 

Second idea, use one exhuast manifold two wastegates and two turbos. Set the wastegate on the small turbo to become open at a designated pressure. Allow the small turbo generate about 10-15psi. The dumped gas is then sent off to turbo number 2. Getting this done could be done via reentering the exhuast manifold or by plumbing a tube that is outside of the manifold but joins the gas flow prior to the second wastegate to feed the second turbo. Also mind you that the small turbo would always be spinning and pressurizing the big turbo. When the small turbo is being spooled the pressurized air would be routed to the inlet of the second turbo. Then the final air volume pressurized by the big turbo is intercooled.

Your take on this idea?

 

Third idea. By far the most complex. One manifold two wastegates two turbos and a two way valve on the small turbos "cold side outlet". The idea should allow for the least amount of lag an great power thorughout the powerband. Make the small turbo generate about 10-15psi. The valve on the outlet of small turbo would allow air to go directly to the intercooler up till the maximum set boost for that turbo 10-15psi. Then the valve would redirect the air to the big turbo for the remainder of the powerband in order to help spool the big turbo. The valve is used to not lose boost at low rpm due to resistance by the big turbo. Note that once the 10-15psi is met by the small turbo, not only would the output boost pressure spool the big turbo but the gases redirected by the wastegate would also help spool the big turbo. Not sure if the big turbo would need a fresh air supply on the inlet of the cold side when air is not being bypassed to it from the small turbo. If needed two pipes could be spliced onto the big turbo; one that would come from the small turbo the other being a fresh air supply.

 

with the thrid setup the lower rpm and low midrange woud look like Small turbo feeding 80-90% of boost and minimal boost coming from the big turbo

The high midrange and high rpm would look like 80-90% boost coming from big turbo being "prespooled" consistently with 10-15psi of air pressure and bypassed exhaust gases from the small turbo. The most obvious problem with this setup would be plumbing.

 

I need some opinions. Goals are this, a linear powerband, not a huge power jump at high rpm. Good low end power and hig low end torque and a peak horsepower over 900hp. Essentially I'm researching to find a minimal lag system that can generate a lot of power and offer good power at all rpm. The engine is the infamous

2JZ-GTE engine. What is your take on these ideas?

 

Feel free to criticise, as it can only enrich my knowledge of these complex systems. I see it this way. One big turbo, lots of lag huge power jump at high rpm, no good. Two small turbos working in parallel, consistent power low lag, lack high horspower potential. Sequential setup, could be the holy grail for little lag, power everywhere, and high horsepower capabilities.

[Phyxius]

The main problem i see with sequential setups is not overspeeding or surging the smaller turbo once the bigger one comes on. It may not be that big of a deal, but it seems like something you may want to consider.

[OlderThanMe]

Low pressure turbo= big turbo

High pressure turbo= smaller turbo

 

The general concensus is that you can't have low spool and have good power. I think this is narrow minded and not willing to think outside the box.

 

There is the concern of the smaller turbo limiting the boost of the larger one since it has a smaller input size. Once the larger turbo spools it will pull a vacuum on the smaller turbo.

 

I came up with a solution to this problem. Setup a valve (like a wastegate) to vent air around the small turbo. Connect a tube just before the high pressure turbo on the intake side and then the valve, and then connect it just before the low pressure turbo's air intake. I have a little sketch I made that I'll post up soon.

 

You would just plumb a manifold to the high pressure turbo like normal with your external wastegate and then have a 90 degree bend after the high pressure turbine and feed down right into the low pressure turbo. You can wastegate around the low pressure turbo but you won't need a big wastegate as the low pressure turbo will flow really well.

For the high pressure turbo you will want a big wastegate so that when you finish boosting with the high pressure turbo that you will get good flow to your low pressure turbo for it to spool quickly.

 

BTW you would want a sensor placed inbetween the turbos so that if there was ever vacuum you would actuate the valve and open the path to bypass the high pressure turbo.

 

I came up with this solution for using on an L6 but it would work on any inline engine. You could do it with an opposed motor or a V-type motor but you would have to be creative with plumbing.

 

Some dodge diesels use a consecutive setup like this but don't use a high pressure turbo bypass valve. Maybe that is because it is an OEM design..

[naviathan]

2JZ=6 Cyl.

2 Manifolds = 3 cylinders per turbo

Turbo 1 = Small compressor large turbine wastegate to second manifold

Turbo 2 = Large compressor Small turbine single standard wastegate

 

 

The larger turbine on the smaller turbo allows it spin up fast and reach peak boost quickly. The smaller turbine on the larger turbo spins up slower and is given a quick burst as the first turbos wastegate opens allowing the second turbo to maintain the boost into the upper RPMs. I think you covered this idea in your lists up there, but it was a little confusing the way some of that was worded. I think this would be optimal though.

[OlderThanMe]

Yes he covered that idea but the turbo placement was a little confusing.

The main problem is that three pistons would be making low end power and the other three would make high end power because of the different backpressures of the turbos. Let me rephrase that: some would have low end restriction and others would not.

 

There would be some negative effects(don't know them all) of the different backpressures that I think it would compromise the reliability of the engine. The top set of problems may not be right but I can think from the backpressure differences you would have problems.

It is an interesting idea but you want to treat all 6 of your individual engines, that are connected together inline, the same.

[naviathan]

Yes balancing the system would be difficult, but with a standalone engine management it would be possible to balance each cylinder individually. You could account for the difference in back pressures through the AFR. The initial setup would be the hardest part as you would need an oxygen sensor per cylinder, but I think the overall results would be incredible.

[OlderThanMe]

That is possible and the O2 sensors would be expensive as heck...

The true sequential setup would be easier to setup I think. I don't know if the effort would be worth setting up a side-by-side unequal size turbo system. I would not want a chance to waste a shortblock in experementing with a side-by-side uequal turbo setup.

[naviathan]

Yes a series sequential turbo setup would be easier, but there is a lot less efficiency in it. You loose a lot of flow to the second turbo because of the first turbo. The parrallel turbos would be expensive, but if you're not looking at cost it seems to me it would be the way to go for all out power throughout the RPM range.

 

On side note, I think it's funny we haven't heard from the thread originator since the first post.

[OlderThanMe]

Here is a sketch I did of a CTS (Consecutive Turbo System)

[Alex_V]

Id say you'd want some sort of massive bypass valve to divert the exaust around the small turbo to the big one....think about it, your going to have 400+ HP worth of it flowing, gotta make sure its not restricted before the turbine.

 

Other then that looks like a great setup, Id love to see it done.

 

~Alex

[OlderThanMe]

Yes. You are correct. Probably the biggest one you can find...not afford...find.

Maybe one of those HKS ones. I have been thinking about a custom one using an actuator from a regular wastegate but not using a valve: use a butterfly valve with a good seal. And yes 400++ hp from this turbo setup with very little lag. boost from ~2500

There are plenty of guys making 500 hp but you don't have that power for very long in the power band. A 400hp turbo motor that boosts for 4000 rpms should be faster than a 600hp motor that boosts for 2000 rpms. The higher horsepower motor would be good for drag racing with a good auto tranny but for a road racing/rally/autox you want a really wide power band and long gears.

I hope to get started on my motor build this summer and use this type of turbo setup. Of course I won't be boosting much at first. It will take a little time to get the boost up and get the turbos and EFI tuned together.

[antimanifesto09]

I hope to get started on my motor build this summer and use this type of turbo setup. Of course I won't be boosting much at first. It will take a little time to get the boost up and get the turbos and EFI tuned together.

 

so, how's the build coming? did you ever get going on this project?