Twin (Compound) Charging - Anyone?

BLSTIC · 26-03-2007, 09:11 PM

Hi people, after reading about so many people turbo-ing their e-series, I was wondering whether anyone has gone completely crazy and fitted some kind of compound supercharging system to their car.

By that I mean one compressor feeding into the inlet of another, be it turbo-turbo, turbo-supercharger, or supercharger-supercharger.

I imagine that there would be enough room in the e-series engine bay if a water-air top mount were used as the final intercooler. With an overly large turbo on the driver side of the engine bay, and a centrifugal supercharger on the passenger side. The intake air would come from a duct similar to the standard duct, but on the other side, through your (insert massively oversized turbo here), out to the front of the car, through a front mount, into the (sane sized centrifugal blower), out of the blower, through water-air intercooler that also turns the air through 180*, and into the throttle.

I would have to have a really close look at my engine bay, but having a look at the CAPA website reveals that their kits are entirely located on the inlet side of the engine bay (if you don't tick the front-mount box), leaving a large amount of room on the exhaust side. The intake path in the pic below could be replaced by a water-air intercooler, which can be designed in pretty much any shape you like, as you can concentrate on the airflow patterns internally without having to worry about the coolant flow as much.

Thoughts?

cya
Ben

dansedgli · 26-03-2007, 09:15 PM

Do it. Good thread here:

http://www.performanceforums.com/for...t=twincharging

http://www.performanceforums.com/for...t=twincharging

Allen · 26-03-2007, 09:15 PM

Why would you? What gains would you achive?

People buy e-series, because they are a relativly cheap car, and easy to modify... I doubt people would go to the troube of turboing their car, and then saying, "bugger it, I'll spend even more money on a supercharger too... even though i'll be running the same boost levels as before"

Fine for mega buck show cars such as Gary Myers Mustang, and Steve from RDP's Torana, but totally un suited for driving... or power...

dansedgli · 26-03-2007, 09:16 PM

You do it for super reponse and massive top end.

Bloke on PF has 5 psi from idle.

Allen · 26-03-2007, 09:22 PM

I doubt the theory behind it... using two units in parallel is fine, such as a twin turbo into a common plenum, but where are the gains of running already compressed air into another compressor?

Everyone knows that compressing air generates large gains in the air's temp, so why would you do it twice? It will just be a restriction... Not to mention that a supercharger, roots or centrifical uses large amounts of engine power to run.
So, not only will it increase intake temps, but it will rob power...

BLSTIC · 26-03-2007, 09:23 PM

yeah pretty much. If you use a screw blower as the 2nd supercharger, you are guaranteed 10psi (or whatever) from idle-redline, MULTIPLIED by the boost that the turbo/other supercharger would make on its own.

ie your turbo is capable of making 15psi at any given flow rate, or a 2:1 pressure ratio (it isnt, but hold with me here), giving 30psi absolute (15 psi boost + ~15psi atmospheric pressure) as the intake for the supercharger. The second compressor also normally makes 15psi, or also a 2:1 pressure ratio. Multiply your 30psi (absolute) by two, and you get 60 psi. Take the ~15psi atmospheric pressure off that and you end up with 45psi boost, keeping both the turbo and the supercharger spinning relatively slowly (to compensate for the extra airflow the turbo has to deal with, you just choose a huge one, or get two).

Thats a brief theory. There is more to it than that though...

dansedgli · 26-03-2007, 09:27 PM

Quote:

Originally Posted by fairlane_ghia

I doubt the theory behind it... using two units in parallel is fine, such as a twin turbo into a common plenum, but where are the gains of running already compressed air into another compressor?

Everyone knows that compressing air generates large gains in the air's temp, so why would you do it twice? It will just be a restriction... Not to mention that a supercharger, roots or centrifical uses large amounts of engine power to run.
So, not only will it increase intake temps, but it will rob power...

Running a supercharger doesnt generate much heat. The extra exhaust gasses this creates helps spool a large turbo quickly.

A roots blower gives boost from idle and helps spool a larger than normal turbo which can make more power than a smaller turbo without having to deal with the extra lag.

Allen · 26-03-2007, 09:29 PM

Have you ever studied fluid dynamics?

Atmospheric pressure is totally disregarded, as the air in the inlet tract, is under pressure.

If you run 15psi, into a compressor that is compressing air out at 15 psi, no air will be compressed... it will just be a restriction.

Sorry, but that theory goes against everything taught at uni...

Dan, theoretically that is correct, but one is eventually going to become a restriction to the other.

If after one charger, you have 10psi then the next charger can't flow more than 10psi as the air simply will not be there to compress, unless you have a bypass system that allows the first charger to be bypassed at a certain pressure level.

BLSTIC · 26-03-2007, 09:35 PM

the idea is not to compress it to the same pressure, but compress it (the VOLUME of intake air) by the same amount. Ie if your compressor normally has a flow rate of 300cfm input, and only 150cfm output, it is halving the volume (and doubling the pressure). This change of volume happens regardless of whether or not the inlet is under pressure.

Allen · 26-03-2007, 09:38 PM

The point is, air will be pumped into a plenum at a given pressure, after which it cannot be pumped out at a higher pressure, as that will create a vacume between the two compressors.

If you want to run more than one compressor, they should be run in parallel into a common plenum... Anything else is a **** really...

dansedgli · 26-03-2007, 09:42 PM

If a supercharger supplies a constant 10psi and a turbo blows into the supercharger wont the boost that the turbo supplies add to the boost of the supercharger?

sphell · 26-03-2007, 09:50 PM

Quote:

Originally Posted by fairlane_ghia

If you run 15psi, into a compressor that is compressing air out at 15 psi, no air will be compressed... it will just be a restriction.

That's exactly what I would have thought. The whole concept sounds like a massive headache. If you want to run a big turbo for massive boost, chuck a bottle of NOS in the boot, that'll help it spool. Even designing a sequential type turbo setup would be easier IMO.....but then again why would you bother when there are tried and tested methods that are easier, probably more reliable and cheaper?

Allen · 26-03-2007, 09:51 PM

Well, a supercharger will never supply a constant pressure, being liniar with engine speeds... but the only way to efficantly "add" the pressure from the two compressors is to run them into a plenum...

Its kind of the same theory behind the rubbish ebay electric superchargers... they simply cannot keep up with the airflow and therefore become a restriction, except this would work in the opposite way... The first compressor cannot keep up with the second, so it becomes a restriction.

Allen · 26-03-2007, 09:53 PM

Quote:

Originally Posted by sphell

That's exactly what I would have thought. The whole concept sounds like a massive headache. If you want to run a big turbo for massive boost, chuck a bottle of NOS in the boot, that'll help it spool. Even designing a sequential type turbo setup would be easier IMO.....but then again why would you bother when there are tried and tested methods that are easier, probably more reliable and cheaper?

Exactly... and if you want to help spooling of turbos, do what the WRC teams do and run an injector in the exhaust to keep the turbine speed up.

ROOSTA · 26-03-2007, 10:05 PM

If i remember correctly back in the day one of the Car manufacturers made a factory SUPER-TURBO 3 or 4 cylinder.. Any one remember this.. Might help answer the big questions..

Cheers,
Nik

ROOSTA · 26-03-2007, 10:12 PM

Just found this info on the MINI COOPER SUPER-TURBO KIT..

1 - Cool air is inhaled through the HKS filter, which has the factory grille scoop blowing onto it
2 - Cool air enters the turbo compressor
3 - After being compressed and heated by the turbo, hot air travels toward the throttle body
4 - Hot air enters the throttle body and travels into the supercharger
5 - After being compressed and heated by the supercharger, very hot air exits the supercharger - it has been heated twice now (compressor efficiencies are multuplied) so if the turbo is 70% efficient and the supercharger is 60% efficient, overall efficiency would be 42 %
6 - Very hot air enters the intercooler. Intercoolers deliver a % temperature drop, so if the intercooler is 80% efficient, it removes 80% of the difference between the very hot air and ambient
7 - Cooler air (still very warm, I'm sure) exits the intercooler and enters the intake manifold.
8 - After combustion, exhaust gases exit the cylinder head into a custom exhaust manifold and are routed through the turbo, exiting on the left into a custom downpipe.

Cheers,
Nik

sphell · 26-03-2007, 10:15 PM

Quote:

Originally Posted by dansedgli

If a supercharger supplies a constant 10psi and a turbo blows into the supercharger wont the boost that the turbo supplies add to the boost of the supercharger?

I would have thought that once the turbo starts to supply more boost than the supercharger as the RPM rises, the supercharger basicly becomes a very expensive restriction in the intake. The supercharger will only ever spin as fast as the RPM allows and if the turbo is trying to blow say 20psi through a compressor that can supply a max of 10psi (for example), then the supercharger is slowing down the rate at which the air can enter the engine.

Allen · 26-03-2007, 10:17 PM

Doesn't say anything about the pressure drops between the turbo and supercharger, or what kind of pressure is used at all.

Overall efficiency is only 42% Which could be bettered by a single turbo... Pretty expensive and inefficient way to do things...

dansedgli · 26-03-2007, 10:18 PM

I dunno. There is too much crap to wade through on PF.

Its all about pressure ratios and stuff, not psi as such. I used to know why it was good but cbf learning it all again.

Big turbo + nitrous or antilag ftw.

Some trucks use compound turbocharging to force like 100psi into some deisel motors. A single turbo cant do it so they use 2 and feed 1 into the other. http://www.performanceforums.com/for...compound+turbo

FYI I wouldnt bother doing it and thought it was pointless as well. But it is interesting and depending what you want in a car it can be suitable.

ROOSTA · 26-03-2007, 10:21 PM

Feel free to have a read of this thread.. Shows dyno graphs and the like..

http://www.mini2.com/forum/engine-dr...o-charger.html

250hp at the wheels in a mini wit no traction through the 1st 4 gears.. AWESOME!!! Imagine the sound of a twin spooled beast..

Cheers,
Nik

private9 · 26-03-2007, 10:29 PM

Quote:

Originally Posted by ROOSTA

If i remember correctly back in the day one of the Car manufacturers made a factory SUPER-TURBO 3 or 4 cylinder.. Any one remember this.. Might help answer the big questions..

Cheers,
Nik

Yep, import Nissan Micra/March. 3 cylinder started off with super at low revs and then when turbo starts to spool, some sort of valve switches and feed the engine the turbo boost instead.

private9 · 26-03-2007, 10:31 PM

Quote:

Originally Posted by BLSTIC

Hi people, after reading about so many people turbo-ing their e-series, I was wondering whether anyone has gone completely crazy and fitted some kind of compound supercharging system to their car.

By that I mean one compressor feeding into the inlet of another, be it turbo-turbo, turbo-supercharger, or supercharger-supercharger.

I imagine that there would be enough room in the e-series engine bay if a water-air top mount were used as the final intercooler. With an overly large turbo on the driver side of the engine bay, and a centrifugal supercharger on the passenger side. The intake air would come from a duct similar to the standard duct, but on the other side, through your (insert massively oversized turbo here), out to the front of the car, through a front mount, into the (sane sized centrifugal blower), out of the blower, through water-air intercooler that also turns the air through 180*, and into the throttle.

I would have to have a really close look at my engine bay, but having a look at the CAPA website reveals that their kits are entirely located on the inlet side of the engine bay (if you don't tick the front-mount box), leaving a large amount of room on the exhaust side. The intake path in the pic below could be replaced by a water-air intercooler, which can be designed in pretty much any shape you like, as you can concentrate on the airflow patterns internally without having to worry about the coolant flow as much.

Thoughts?

cya
Ben

I have read about this sort of stuff being used in tractor pull competitions where they need massive torque instantly. Apparently very popular in those comps.

ROOSTA · 26-03-2007, 10:34 PM

Yer i just found info on the micra.. apparently they had an clutch based supercharger similar to a air-con setup so you could switch the supercharger off for better fuel economy.. then on again if ya needed more boost.. Thats pretty friggen sweet..

Cheers,
Nik

Obriza · 26-03-2007, 10:36 PM

a mate of mine tried this to his commodore... the outcome was that he couldnt have them boosting at the same time... the only way he got it to work was to have the charger going from idle then once it hit 3000rpm the charger turned off and the turbo started. Maybe his setup was wrong but thats where his was at

RMCprime · 27-03-2007, 12:47 AM

looks like a v8 twin turbo into a supercharger to me.

Mr_4.0 · 27-03-2007, 02:52 AM

Quote:

Originally Posted by fairlane_ghia

Have you ever studied fluid dynamics?

Atmospheric pressure is totally disregarded, as the air in the inlet tract, is under pressure.

If you run 15psi, into a compressor that is compressing air out at 15 psi, no air will be compressed... it will just be a restriction.

Sorry, but that theory goes against everything taught at uni...

Dan, theoretically that is correct, but one is eventually going to become a restriction to the other.

If after one charger, you have 10psi then the next charger can't flow more than 10psi as the air simply will not be there to compress, unless you have a bypass system that allows the first charger to be bypassed at a certain pressure level.

for a start, most fluids cant be compressed, however, air and gasses can. so fluid dynamics do not apply.

go and tell gary myers his setup was a load of c.rap?

Allen · 27-03-2007, 08:06 AM

Err... air (which is a gas) falls under the fluid dynamics catagory... Fluids are not limited to liquids.

Ever notice how Gary Myers removed the twin supercharger setup and replaced it for a single blower? Same with the RPD Torana, IIRC its running a NOS 350 Chev now... these cars are show cars, with nothing practible about them...

Its all well and good to build these things to impress people with lots of shiny stuff, but they are trailer queens that would never be run for long periods of time.

steven95falc · 27-03-2007, 08:53 AM

i have worked in the pump industry for several years now and when running 2 pumps in series it will effectivly double the presure from each pump but the maths and so forth in mtching the pumps is not worth it even tho people have done it ive never seen anything that has won anything dyno shootout thru to circuit cars that runs both the headaches must outweigh the gains

BLSTIC · 27-03-2007, 02:21 PM

Quote:

Originally Posted by fairlane_ghia

The point is, air will be pumped into a plenum at a given pressure, after which it cannot be pumped out at a higher pressure, as that will create a vacume between the two compressors.

It can, the idea is that the first compressor flows more air than the second, keeping the plenum (or piping, intercooler, whatever...) at 15psi.

The idea is that this blower knows nothing about the second blower, all it 'sees' is that it is moving 600cfm of air into a space, and it is being drawn out at 300cfm (incedentally at 15psi, or 30psi absolute). Whether or not that air is being drawn out by an engine or another supercharger has no effect on the operation of the first supercharger.

The second supercharger sees 30psi absolute. I believe this is where most people get lost. The second supercharger's job is NOT to compress the air to 30psi absoloute, its job is to compress the air further (in this case, we have a rootes blower flowing twice the amount of the engine, giving a pressure ratio of 2:1). The second blower doubles the pressure again, giving a 60psi absolute output, or 45psi above atmospheric.

hope that explains it.

As far as I am aware for efficiencies, even with the previously mentioned 45% efficiency, it would probably compare favourably to a normal setup compressing that same amount (ie a 4:1 pressure ratio).

cya
Ben

eMpTy · 27-03-2007, 06:04 PM

Along similar lines to this but a totally different setup.

Scania trucks released a turbo compounding setup in either 2001 or 2002 (attended a workshop training weekend but forget which year it was) that ran the main turbo off the manifold and a 2nd smaller turbo further down the exhaust, both into a common plenum.
Idea was that the smaller turbo would generate boost in the low-mid rev range and the larger one would perform as normal. I forget the exact figures but there were significant gains in torque.