Is it possible to run BOTH a supercharger WITH a turbo or twin turbo setup? I'm not talking about some sort of "dyno queen" superfreak. No no no... what I am interested in is achieving the bottom end torque and power that smoothly translates into top end power without the side effect of turbo lag.

Can it be done without placing too much stress on the engine via forced induction overlap? Can all that extra hardware even fit? Theoretically it sounds pretty good but is there any real benefit to this idea? What are the technical drawbacks to such an idea?

Yup, it's been done and makes for a very good combo.

Look up the Volkswagen 1.4L TSI Twincharger engine. Makes 170hp out of a 1.4L with virtually no lag. There's some obvious complexity involved.

I'm not sure if there are any dyno charts around, but the guys who were the first to turbocharge the Ford GT, they got bored and but the stock supercharger back on in addition to running the twin turbos. Made for an amazing torque/boost curve!

To somewhat lower/transfer the complexity, you can use a VNT turbo to eliminate the lag. However, there's only one VNT turbo on the market for gasoline engines and it comes on the Porsche 911 Turbo.

Oh yeah, another option is to run a series sequential turbo setup. You have a small and large turbo run in series. The small one spins up first (also generally a VNT turbo) until the second turbo gets spinning. Then the exhaust flow is managed between the turbo turbos. Many of the diesel passenger cars in Europe use this setup. Like the Peugoet 407, BMW 335d, new Jaguar, etc.

If you properly engineer your turbo system, its a waste, extra weight complexity, cost and load on engine.

What are the technical drawbacks to such an idea?

The simple answer is....... not that simple

doable, yes, practical in a HP to $$ sense, no.


Honda/Acura basically used a twin scroll turbo to get rid of some lag an a non-traditional way. It uses one scroll for low RPM/low exhaust volumes and then opens exhaust to the other as the exhaust flow/demand/load goes up.

You could jerry rig a twin scroll turbo charger to do something similar. Run all the exhaust to one side of the turbine housing with the manifold, plumb a large wastegate to the other scroll. (insert some real science about mass flow, exhaust energy, and velocity) That wastegate I guess would be best getting its pressure signal from the exhaust pre-turbo. I'd have to put more thought into it, it could work. Then you could run a second wastegate in a traditional manor to control turbo speed. Then you run into the issue of matching the turbine and compressor wheels to get the best trade off between spool, a broad powerband and not running into surge, assuming it'd even work. It's nothing that would be too crazy to put together with what is available already. But even that's a half cracked idea and not worth the trouble without some time and money to spare/waste and some desire to design a better mouse trap.

The only downside to the turbo system on my car is the stock engine runs out of potential before the turbo system does. If you set a realistic goal you'll be happy in the long run.

Thanks all. I wasn't even thinking of the added weight for such a setup. Not exactaly practical is it?

It's definitely heavier with both setups! There are some guys that add a turbo to the supercharged Mini Cooper S.

To do a proper twin turbo/series setup requires some very complex castings, control valves, and the control scheme to manage it all. It's really only 'practical' from an OEM standpoint where it's designed that way from the beginning. To try to do such a setup on a NA engine would be very very difficult.

The diesel truck, sled pulling guys like to run two turbos in series.

Twin Charging is relatively popular in the Mini Cooper S community and I even have a friend that runs the setup. Stock supercharger, has a slightly larger then stock pulley (less boost) and a GT28 Turbo. For engine management, he simply uses an SAFC and a wideband. It's certainly not the optimal way of doing things, but there aren't a lot of options for those cars.

Another option for dual turbos is a Compound setup, which can be seen on DSM Tuners in the fabrication section on a DSM with a full build log. The site seems to be down right now or else I'd post a link.

Ah, works now. Here you go.

http://www.dsmtuners.com/forums/cus...et-up.html

wow, that's a pretty cool setup.

The more I think about running a a twin scroll with the manifold feeding one side and a wastegate feeding the other side it seems feasible, but IDK. It seems more or less like it would be useful in manipulating intake vs exhaust pressures and tweaking VE more than anything...............

I found this video on the internet looking to see if maybe it had been done elsewhere, exact same concept different execution, hmmm. Completely doable using a twin scroll turbo and 2 wastegates with a purpose built manifold.

around minute 3 of the video

http://www.youtube.com/watch?v=QM7BhSfsO-k

I would put a well engineered turbo system against any of that stuff.

Posted By smartbomb on 07-15-2009 01:30 PM
I would put a well engineered turbo system against any of that stuff.

Just for the sake of conversation what kind of criteria could be used to determine which system outperformed the other?

FAT performance here in Az currently has built a few Subarus with the compound superchager and turbo setup. Interesting concept but I have yet see it proven worthwhile in reality.

Here is a link to the NASIOC post with a pic of the setup if your interested..

http://forums.nasioc.com/forums/showthread.php?t=1688562

HKS used to twincharge MR2's in the 80's.

Posted By Big J on 07-15-2009 03:22 PM

Posted By smartbomb on 07-15-2009 01:30 PM
I would put a well engineered turbo system against any of that stuff.

Just for the sake of conversation what kind of criteria could be used to determine which system outperformed the other?

Power and powerband

There's also the old Group B Lancia rally car.

From a DIY perspective, I think a roots blower and a turbo is the easiest approach. But the modern sequential parallel systems used on diesels are damn trick:

http://jalopnik.com/5119558/2010-jaguar-xf-s-diesel-better-faster-gets-35-mpg

My first thought was VW's 1.4L twincharger. Original Poster, google it; you should be able to find alot of specs and illustrations on how it works.

I wouldn't call the idea a waste, depending what your goals are. As someone said it makes the most sense from an OEM standpoint - VW's goal was fuel efficiency and drivability out of a small gas engine. In some countries you are taxed on engine size so it makes alot of sense for the buyer. IIRC the Golf V gets low or mid 40mpg's with this engine which is pretty darn good. The 200hp 2.0T for comparison can pull mid 30's at best. Imagine, if it responds to light mods like their other FI engines do, a spacious 200hp daily driver with a fat power curve that pulls 40mpg's is just a reflash away. Barring the diesel argument of course. If they offered this engine in the US, I'd probably buy another VW for a daily driver.

To mod an engine this way from a tuning standpoint, I don't know. There's more than one way to skin a cat. Tthere are a few companies recently developing twincharger kits...

compound FI engines are cool for the mere factor of having two forms of added HP production however cost effectiveness and overall up keep is a nightmare.

I remember in SCC there was an article that showed a Audi, i think, twincharged and showed the equation for proper boost calculations. Does anyone remember or know the actual equation to calculate the boost on a compound twincharged system?

I also first herd about this on the MR2.

The VNT really is my favorite~! If any one here ever gets a chance look into..... I believe it was corky Bell who even had his own kit out way back that used one of the VNT units. I think he has a book that has a large section about it.

Posted By emceesquared on 12-28-2009 09:46 AM
I remember in SCC there was an article that showed a Audi, i think, twincharged and showed the equation for proper boost calculations. Does anyone remember or know the actual equation to calculate the boost on a compound twincharged system?

It's easy, just convert the psi into pressure ratios.  That's how you need to think when using forced induction.  For example most Roots superchargers can run 10 psi of boost without a problem when properly sized.  So (10+14.7)/14.7 = 1.68.  So we put that on a car that has a turbo that runs 14 psi of boost.  That means the supercharger sees 28.7 psia of air at its inlet.  We multiply that 28.7 by 1.68 to get 48.2 psia, subract out ambient pressure (14.7) to get a total of  33.5 psi of boost at the intake manifold. 

I saw a twin turbo to supercharger setup on a convertible ferrari testarossa. Koenig I think.

In my estimation the whole dual forced induction think is over complicated for the benefits. The original engineers of these systems in the 80's were looking for a solution that has been provided to us in the form of ANTI-LAG and Ball bearing turbos and sophisticated engine management systems that allow us to build boosted engines with 10:1 cr instead of 7.5:1 cr...
Correct me if I'm wrong but 'Twin-Charging' is a cool science project but really not practical for motorsports