View Full Version : Twin Turbo!

4th April 2000, 17:54
Anybody know/done twin turbo on impreza? the reason being to have power in the low region of the engine revs.Is it possible what would need to be changed and what sort of cost involved. I would want the small turbo to cut in really low in the rev range say about 750-1000rpm then switch to bigger one at 3000rpm nice and smoothly. I do like the kick from a turbo don't get me wrong it's just that when wife and kids are on board I won't to drive sensible so keep the revs low without losing out to lose of power or would i just be better off putting some sort of boost control so i could switch between ( http://bbs.22b.com/ubb/biggrin.gif and http://bbs.22b.com/ubb/cool.gif ) High and low boost. I know It is a bit of do you wont power or comfort(smoothness) I would like both, to have cake and eat it!
Thanks for any feedback Ian

4th April 2000, 17:59
Hi Ian...

you dont give up.... lol

Some subarus already have twin turbos... Legacy for example.

Dont bother with this route.. it is too complex.... and the sequentials will limit your power... *I realise you want low down power*.

If you are more interested in low down grunt... fit a smaller turbo... or up the compression.... but again.. these ideas will decrease the top end capabilities.


4th April 2000, 19:42
or a small squirt of nitrous would reduce the overall lag. Keep it sensible and fit a pressure switch to make it cut out when the boost comes on line and it should be okay.

4th April 2000, 22:07
Hi All,

Talking of using NO2 for anti-lag brings me onto my favorite subject of the moment. How to reduce the time from standstill to full spooling of the turbo.

Normally you have to wait until the car is moving (~2000rpm) before you get significant help from the turbo. Before this point you are driving a NA car with low compression.

Now there are various methods of anti-lag, most involving loud bangs and flames (yippee http://bbs.22b.com/ubb/smile.gif) but also involving lowering the life of the turbo/exhaust (boo http://bbs.22b.com/ubb/frown.gif).

NO2 squirt would get you going but even used like this (small amounts) is going to require refils from time to time (and it ain't cheap).

Does anybody know if any (serious) work has been done using an electical motor to drive the turbo shaft to provide boost before the exhaust gases can do their job ?

Stay with me. At idle nothing happens. As soon as you rev the engine or move off in 1st an electic clutch (like a/c compressors) links the turbo shaft to a powerful electic motor. The motor starts to spin as fast as possible using power from the battery (so no lost energy, unlike a supercharger). This *may* give a few psi of boost low down, say 1000 - 1700 rpm. As the turbo starts to be driven by the exhaust gases, the electronic clutch disengages. Hopefully the time between starting off and the time until the turbo is fully spooling would be reduced.

Once at speed, any power lost from the battery is restored.

Now I know there are a few problems with this such as electic motors not liking being next to very hot objects, i.e. turbos but I think it may have some merit.

Thoughts anybody (I am being serious by the way).



4th April 2000, 22:30

Its a valid idea....

And I am afraid Garrett already beat you to the patent.... I think it was last year they designed a turbo with a built in motor for just such an application...

I never heard anything more about it... http://bbs.22b.com/ubb/frown.gif

You can get forms of antilag without igniting fuel in the manifold.. or when the exhaust valves are open....

but these systems are quite limited... and do reduce the life of the turbo slightly....

How about using an accumalator... which is charged by boost.... and released when you go to WOT.... I suppose the capacity of the cylinder would have to be massive...

If you think about it....you will get out of it less than you put in... losses.. http://bbs.22b.com/ubb/frown.gif


4th April 2000, 22:42

Really ? Damn and ar*e. I have thought about that setup on and off for a couple of years. Dammit !

Accumulator ? Do you mean something like an air compressor ? I.e. compress a load of air during cruise/idle into a large cylinder using a small electic pump. On the application of WOT dump the whole lot onto the turbine blades to get it spinning ? That would work I think.

Only problem may be that dumping lots of cold air onto the turbine/into the downpipe would actually lower the efficiency of the turbo and scavenging a little (maybe) as that side likes to run hot. ??

Best idea I saw was from my 8 year old nephew (who is nuts about rally cars). He did a drawing with a small wheel and lots of gears and on the other end was a big fan. When accelerating, the wheel would be on the ground and through all the gearing would drive the fan really quickly powering the the air into the intake. http://bbs.22b.com/ubb/smile.gif http://bbs.22b.com/ubb/smile.gif http://bbs.22b.com/ubb/smile.gif (Serves me right for saying the turbo is just a very fast spinning fan).



4th April 2000, 23:01
Wasnt the Garrett idea thus :

at low exhaust gas volume an electric motor drives the turbine. When the gas speed picks up the turbo ends up driving the motor which becomes an alternator..and no need for extra boost control mechanims..the motor could limit the speed of the turbo.

great idea, but these turbos spin "quite" quickly..guess thats where the problems lay.

kit vara
6th April 2000, 13:44
Hi All

Ian i have read articles of motors with a supercharger such as in the G60 VW's that are mechanicaly driven and hence grunt at low revs to bring on the turbo. Would this route be what you're asking maybe?

Also in another article(this time in REVS April ed) a MK2 golf with a 2.8 VR6 with turbo and NOS. The NOS is injected not into the cylinders but into the tubo?

Would this give ealier spool at lower revs i wonder? or just get you quicker to boost revs?

Comments please.

Kind Regards

Ian Cook
6th April 2000, 14:50
Hmmm, I would have thought a Supercharger would do exactly what you want it too, although it does sap power, it works from word go, being directly driven from the engine by a belt ? no need for expensive electric motors etc, but i would think very expensive to actually do, ask the Americans some of them have put superchargers on their 2.5 RS's ?????

6th April 2000, 16:39
Was it Lancia who used to run rallycars with superchargers AND turbochargers fitted? Supercharger for fast low end torque and turbo lag reduction, turbos for sheer mid to high end grunt... would that be super-turbo-charging?


6th April 2000, 18:20
I think it was their Delta S4, could be wrong! http://bbs.22b.com/ubb/eek.gif

8th April 2000, 03:32
Well, nobody seems to ever mention it, but I have read in a magazine that the Evo IV and up road cars come with some type of anti-lag system. I even know of a website that has a photo of the anti-lag valve (no, I am not talking about the BOV). Somebody must know about it? Is it another dubious Evo feature, like the Yaw Control? How is it supposed to work?

27th April 2000, 02:41
Indeed it was the Delta S4.

Superchargers aren't that expensive (I believe that they are cheaper than turbo's... at least here in Australia) the problem would be where to put it in the engine bay, and the 'cut over,' mechanism.

Also with the twin turbo idea I don't know if there would be enough exhaust gas pressure to spin 2 turbos... and even if u are talking sequential turbo's the low-down one would have to be mighty small. BUT then again i know nada about this so I am probably wrong http://bbs.22b.com/ubb/smile.gif

Ben v.

Nova Turbo
27th April 2000, 13:38
Hi Ian, can I fit a twin turbo to my nova which is already turbocharged with a calibra engine in it. Its running at about 220 bhp on full boost, with alloy dump valve, and PACE chargecoolers. I would like to attain about 280bhp so that i can piss all over my mate Kippa who has a r5 1.7 hybrid turbo which he claims has an output of about 250bhp. Can anyone help me.........
By the way i bet you are still wearing your adidas sambas tied skin tight!!!

28th April 2000, 07:26
Nissan used to sell a Micra/March K10 in Japan called the Super Turbo which was both supercharged and turbo charged (and 1 litre!).

28th April 2000, 11:44

Which magazine are you talking about... I only ask this because I have occasionally read articles that ARE technically accurate in some of the mags, so there may be the chance that this is worth looking into... but I have my doubts! http://bbs.22b.com/ubb/smile.gif

Of course, there may be some way you could harness the power of a hyperactive dog to help reduce turbo lag... http://bbs.22b.com/ubb/wink.gif


3rd May 2000, 09:47
Another US company (can't remember the name, but looking for it...)also designed an electrical assistance device for turbo chargers...It uses a high speed electric motor fitted with an electromagnetic clutch...At idle/low revs the motor is engaged an spools the turbo to approx 75,000rpm to reduce lag and then disengages as boost builds/impeller speed exceeds a pre-determined threshold...Apparently it worked a treat but seems to have just disappeared...Anyone know whether they are still around???

6th May 2000, 00:51
I read about it in Sport Compact Car magazine, a US performance magazine and I think it is also mentioned on the website rallycars.com, but I'm not 100% sure. SCC does have some good technical info. but is not always the most professional or accurate.

Anyway if you go to this link you will see two pics of what is supposed to be the anti-lag valve. Maybe some Evo owners could at least look and tell us where the lines connecting to this valve go.

[This message has been edited by marcus (edited 06 May 2000).]