Twin charged Cobalt

Its been awhile since i have had some crazy off the rocker idea and then BAM! all of a sudden it hit me.

The early Cobalt SS was supercharged The newest Cobalt SS is turbocharged.

So with a little bit of parts searching you should be able to, if you wanted to, make a TWIN- charged Cobalt SS using mostly factory parts.

Am i nuts? Is this doable?

Probably doable, but not worth the trouble.

its fun though! right?

I've never really understood what benefit you actually get from twin-charging.

Someone care to explain it?

I assume that the turbos are ahead of the supercharger, i.e: air filter-->turbo-->intercooler-->supercharger-->intake manifold

I just can't seem to get my head wrapped around situations like...

... what happens when the supercharger is "creating" more boost than the turbos currently are (i.e., the blower is sucking more than the turbos are pushing)? Do you have some sort of one way valve that allows air to be sucked in if the vacuum in the intermediary pipe exceeds a certain threshhold?

...what happens when the turbos are pushing more than the blower is sucking? Is that solved by a blow-off valve? Does the turbo boost just "push through" the supercharger? Isn't the supercharger actually costing power at that point (being an air restriction), if that's the case?

...or is it some sort of mulitplicative effect, i.e. the turbos compress 1 atm into 2 atms, then the supercharger, which normally compresses 1 atm into 1.5 atm, now compresses the 2 atm into 3 atm? (atm probably not being the correct abbreviation for atmosphere, i.e. 14.7 lbs).

Someone beat me with the clue stick!

Seems more complicated than just running twins. and alot more compicated than just getting a boost controller.

Mini guys seem to have luck with it.

http://sportcompactcar.automotive.com/66696/0506-sccp-2004-mini-cooper-s-twin-turbo/index.html

Doesn't VW have a twincharged engine it runs in Europe in polos and golfs? I know i guy who has a twincharged sunfire and it worked well for him, didn't seem too complicated, he just added a turbo to his factory supercharger kit and the dyno results were pretty solid.

PaulY wrote: Doesn't VW have a twincharged engine it runs in Europe in polos and golfs? I know i guy who has a twincharged sunfire and it worked well for him, didn't seem too complicated, he just added a turbo to his factory supercharger kit and the dyno results were pretty solid.

Any more info than that?

Difference in peak hp numbers? Meat under curve?

Anything that couldn't be done as well with a single source of boost?

I don't remember the exact details since it was a bit since I've talked to him, I remember seeing an in progress dyno graph of something like 275hp with a very meaty curve. I think a basic gm supercharger kit on that motor should put out about 190hp.The supercharger would take up the low end and the turbo would take on the higher end. His dad was an engineer that dealt with flow systems so the proper calcs were done. Part of it was to show it could be done, part of it was for a fun fast car. I know he was aiming for more but I don't know what happened after, I'll have to ask him how it's going.

Does anyone have the link to the Ecotec build book that basically has a chapter for a 250hp build, a chapter for a 350hp build, another for a 500hp build and another for a 1000+hp build? I found the "GM Sport Compact" build and the "Ecotec LSJ Build Book" free to download here: http://tunersource.gmblogs.com/Racer-Tech but they don't seem to be what I remember from a couple of years ago. The books show how to get massive amounts of power out of an Ecotec, whether NA, supercharged or turbocharged.

On Edit: here's the link to the book I was thinking of, the L61 Build Book, which seems to be an earlier version of the Sport Compact book above. (Pop-up warning - my pop-up blocker stopped some pop-ups, but I still got a Partypoker pop-up and Spybot gave me a warning about some adware - Caslemedia or something) http://members.shaw.ca/warped00/bcjbody/buildbook.html Theres a chapter for stock to 250hp, 250-600hp and 600-1400hp.

I think adding a turbo to a supercharged Cobalt could be a nice benefit, but adding a supercharger to a turbo Cobalt would be a waste of time considering how easy it would be to just upgrade the turbo.

Anyways, if you haven't looked around that site (the GMBlog one), do it. It will make you route for GM to survive, simply because they're giving so much info to enthusiasts for free.

Bob

I was under the impression that you had to buy that book. I believe my friend has the hard copy of the one your talking about. He put a turbo ecotec into a 2nd gen sunbird vert.

Nope, GM gives away the pdfs for free on their website. See the edits in my post above.

That Sunbird sounds like a cool sleeper. Does he have a website or anything about it?

Bob

ReverendDexter wrote: I've never really understood what benefit you actually get from twin-charging. Someone care to explain it? I assume that the turbos are ahead of the supercharger, i.e: air filter-->turbo-->intercooler-->supercharger-->intake manifold I just can't seem to get my head wrapped around situations like... ... what happens when the supercharger is "creating" more boost than the turbos currently are (i.e., the blower is sucking more than the turbos are pushing)? Do you have some sort of one way valve that allows air to be sucked in if the vacuum in the intermediary pipe exceeds a certain threshhold? ...what happens when the turbos are pushing more than the blower is sucking? Is that solved by a blow-off valve? Does the turbo boost just "push through" the supercharger? Isn't the supercharger actually *costing* power at that point (being an air restriction), if that's the case? ...or is it some sort of mulitplicative effect, i.e. the turbos compress 1 atm into 2 atms, then the supercharger, which normally compresses 1 atm into 1.5 atm, now compresses the 2 atm into 3 atm? (atm probably not being the correct abbreviation for atmosphere, i.e. 14.7 lbs). Someone beat me with the clue stick!

I think you're overthinking.

The basic theory (in a perfect world) is that the supercharger gives the grunt at the lower rpm's until the turbo spools up.

Still, yeah--it's a bit of a Rube Goldberg approach.

I'll refer back to the HKS twin-charged MR2 from 1995-ish. That was rad as hell.

I like the idea of twin charging.

I like the idea of running two different sized turbos into a single intercooler.

I like the idea of running two different sized superchargers into one intercooler.

I like the idea of running a turbo and a supercharger into one intercooler.

I REALLY like the idea of running a big turbo and a small supercharger into one intercooler.

Anyone see a pattern yet?

super charger spools the turbo faster...little turbo=fast spool, little-ish power. big turbo=wait for spool then WOAAAHHH. Superchrger+big turbo=no lag and WOAAHHH on demand.

nuff said

Yes and no... In a nutshell: It makes good power but drives like crap... One of the early kit-sellers (Helix) doesn't push them at all anymore. For those who want serious power in an R53, there are now better options. FWIW, the TC in a MINI goes: Turbo -> SC -> IC -> intake. Running two IC's is a hose-routing nightmare in a MINI...

A turbo needs to flow air. A supercharger uses screws, or lobes, to compress the air. Wouldn't that impede the flow that a turbo is trying to create?

Twin-charging works because it does compound the boost. What, nobody has ever looked at a Detroit Diesel 6V92 in a Coast Guard Motor Life Boat? All big marine diesels use compounding boost like this:

Air > Turbo > Supercharger > Aftercooler (seawater/freshwater) > Engine

Some have bypass valves that use the S/C exclusively on the low end and switches to the turbo once it spools up. Others get even more complicated with twin turbos (little one and a big one) plus the blower but they leave the S/C functional all the time (no bypass) to compound the boost.

p71 has it right, compounds das boost. I really see no point in it, just a huge mess of plumbing, wiring, and so on. Plus the new Cobalt SS engine is Direct INjection turbo, the Supercharged is an old school style fuel injection engine.

The SS/SC cars were pretty under-rated in the HP numbers. GM rated them at 205hp, but people were getting higher numbers on the dyno in stock form.

The new turbo cars are getting ~300 hp at the wheels with very little work, very little lag, and the stock turbo+direct injection hardware...that's an awful lot for a FWD sporty-car. If you added a supahchajah, you'd be adding another charger just for grins, it would have nothing to do with power output and a lot to do with tinkering.

Bryce

I forgot to say that Republic successfully twin charged their P-47 in the forties. Turbo into a two speed supercharger. Don't bitch about routing tubing until you look at this:

We have a local company here in Phoenix that is running around with a ~2006 STi that is twincharged. I might be able to drag up a picture here.....

Yup, these guys do good work- http://www.forcedairtech.us/gallery/fat-rides/

oooooh I think I need to excuse myself after seeing that pictar

Group B. Think of it like this: Picture a roots-type supercharger with the screws turning.As the lobes "open"(move away from each other) they create a low-pressure area that pulls in the air.The air is then compressed as the lobes move toward each other and it is forced into the engine.With the turbo mounted upstream the air that enters the supercharger is not pulled in,it is pushed by the turbo.(when it is spooled up) A larger volume occupying the same space.As it cycles through the supercharger it is compressed further still and then released into the unsuspecting engine.

Back to the original question. Yes CK1 I think the idea you have would work.

But I would not use a 2.0L version of the engine.

Use a 2.4L version, add the supercharger and turbochargers and their manifolds. Since the Cobalt supercharged uses an intercooler I would replace the intercooler end cap with a dual inlet piece and tune the blow off valve to handle the boost overlap.