Twin Turbo?

[Swordsmith]

I was chatting with one of the mechanics at my local auto shop and he mentioned a twin turbo arrangement he is looking at for his Trans Am.

As he describes it, it is a second turbo placed after the muffler, which works together with the original turbo to create a substantially higher total boost level.

Poking around on the web, I haven't found the specific system he's talking about, but I do see several mentions of the basic idea. It seems there are two plans

1: Sequential operation. Primary turbo runs as normal, but at a certain point it dumps boost and then builds up again together with the secondary. Most people seem to be opposed to this due to the "valley of death" effect where the boost dumps in the middle of each shift range.

2: Parallel operation. Both turbos run all the time. Down side here is that you don't get the potential benefit of effectively having a small turbo and a large (really two small combined) turbo available. Up side is you get a bigger turbo without having to install a bigger turbo.

Dunno much about this yet, just thought I'd see if there were opinions here!

 

[ThatTmoGuy]

IDK how it would be tuned for it but you may want to take a poke around at ststurbo.com

 

[$ub$onic]

A muffler like this?

Lol , I have never hurd of a turbo after the muffler. I have Hurd of them right after the header or under neath the cad of a truck then get the intake piped to the tb

 

[Maddmatts]

I've heard them being called remote-mount turbos. And they usually replace the muffler. Either way, they achieve the same effect with different complexities.

 

[Eric Smit]

yep, remote mount turbos. some people love them, some hate them. pretty cool, if you ask me.

 

[Opticon]

Compound turbocharging. The charge air runs through a smaller compressor first then through a larger one before entering the intake manifold. The idea is that the small compressed creates boost at lower engine RPM and helps spool the larger compressor which takes over once the engine RPM and flow increases.

This is very complicated setup because the smaller compressor can begin to surge and act as a restriction if the larger compressor demands too much air. Compressor sizing, turbine sizing, and wastegate setup is critical and you may even need to divert the intake charge around the smaller compressor when the large compressor spools up.

I really don't see the point of positioning the smaller compressor at the back of the car because it's purpose (quick spool) is hindered as it moves further away from the heat (energy) of the engine.

 

[Preloader]

VG turbos, while expensive, are a much more viable option. In the near future, they should become more common, and thus less expensive.

 

[Opticon]

Usually it's huge diesel trucks or extreme dragsters that play with compound setups. All in all, this setup is almost never worth the extra money and complication on street cars. You can create the same powerband effect on a small scale with variable vane turbines and on a larger scale by increasing low end flow through the normal means (stroke, bore, port, cam) then just spool a larger turbo with your newfound flow...

or just shoot nitrous oxide into the thing.

 

[Preloader]

Usually it's huge diesel trucks or extreme dragsters that play with compound setups. All in all, this setup is almost never worth the extra money and complication on street cars. You can create the same powerband effect on a small scale with variable vane turbines and on a larger scale by increasing low end flow through the normal means (stroke, bore, port, cam) then just spool a larger turbo with your newfound flow...

or just shoot nitrous oxide into the thing.

I'm sayin'.

 

[pwntbywombat]

Usually it's huge diesel trucks or extreme dragsters that play with compound setups. All in all, this setup is almost never worth the extra money and complication on street cars. You can create the same powerband effect on a small scale with variable vane turbines and on a larger scale by increasing low end flow through the normal means (stroke, bore, port, cam) then just spool a larger turbo with your newfound flow...

or just shoot nitrous oxide into the thing.

I disagree. Compound on an engine as small as the one in the Sonic would get you nothing but benefits. Low end torque from the small turbo, with top end power of a larger turbo. But finding a clutch and whether or not the bottom end could handle THAT much torque down low, has yet to be discovered.

 

[sx sonic]

I just got too thinking about this and aren't the majority of the vehicles that are setup for compund charging diesels?? They have a much narrower RPM range that does mitigate a fair amount of problems as far as flow matching turbos. Just a thought that crossed my mind.


I see it as a colosall waste on the sonic and an engineering nightmare

 

[Eric Smit]

I wouldn't see it being a waste at all. it would definitely be expensive, but considering that we don't really have much room under the hood, it would be nice to run a bigger turbo out back and keep the stock turbo for low RPM.

 

[rdss]

Lol , I have never heard of a turbo after the muffler. I have heard of them right after the header or under neath the car or a truck, then have the intake piped back to the tb.

Hurd..... nice! I hurd dat!

I disagree. Compound on an engine as small as the one in the Sonic would get you nothing but benefits. Low end torque from the small turbo, with top end power of a larger turbo. But finding a clutch and whether or not the bottom end could handle THAT much torque down low, has yet to be discovered.

Staged clutches already exist. How much the transmission can handle has not. Well, other than DP and his 5 mt.....

 

[slitzell]

The block is pretty strong as well, tranny will def go first.

 

[firstorbit84]

What about a supercharger and a big turbo?

 

[rdss]

That's another viable option but we have to have a S/C'r first....

 

[Foxbox]

One of my best friends has a compound turbocharged Eagle Talon. Before his most recent engine build he drove it on the street. Idk if he plans on keeping it streetable after his current build or not. I'd assume so though.

It was funny and so cool to see it sitting in his apartment complex parking lot next to regular cars.

http://www.forceengineered.com/searchresults.asp?cat=1825

It goes 9.7@140MPH.

 

[cndctrdj]

The technology is there to not need a multi stage setup. It has been done in a lot of areas Ina lot of cars. The benefits never seem to outweigh the problems.

And a trans am like the op said, will never need anything to help spool up a turbo. It already has displacement on its side

 

[Opticon]

Compound on an engine as small as the one in the Sonic would get you nothing but benefits. Low end torque from the small turbo, with top end power of a larger turbo.

For the money you will spend on that setup you could bore and stroke the 1.4t then port it well enough to spool a Garrett T3 around 2000rpm and support over 300whp. Which is far more power than then existing clutch, trans, and axles will ever be able to handle.

My 28 year old 8 valve 2.2 liter spools a Super60 under 2000rpm and pulls like a Boeing jet to 6000rpm. I'm sure the Sonic's head would flow even better.

"Keep it simple, stupid."

 

[pat]

For the money you will spend on that setup you could bore and stroke the 1.4t then port it well enough to spool a Garrett T3 around 2000rpm and support over 300whp. Which is far more power than then existing clutch, trans, and axles will ever be able to handle.

My 28 year old 8 valve 2.2 liter spools a Super60 under 2000rpm and pulls like a Boeing jet to 6000rpm. I'm sure the Sonic's head would flow even better.

"Keep it simple, stupid."

I beg to differ. The cast manifold/turbine housing and 2.5" vband exhaust are the perfect starting point for a compound set-up. A hardware compound kit could be put together for under 1500 including the cost of the turbo downpipe - this is something Andrew, wombat, and I will be looking at in the next couple of months.. Stock spool, 300whp, and low 20s psi are a good place to be.