hi there
i was just thinking ( usually a very bad idea ), can you fit a small supercharger to feed the turbo ?. the idea being a small charger takes car of the low revs areas and once you reach a certain revs it switches off and allows the big turbo to do its business ?( using some sort of trigger switch, not very difficult to find)

or have i lost it this time

there must be a draw back somewhere or it would have been done before right ?

 

I think Lancia did this in the Group B rally days (on the 037). ISTR it took them a long time to get it right -- and I suspect their resources were a bit bigger than yours

 

Why ont just throw away the turbo and fit a supercharger ?

 

Unless there was some seriously clever ducting and valves at work the supercharger would become a liability to the system when the turbo took over and needed to such air past the charger. Turbo cars give better fuel economy (in theory) than supercharged cars as the boost is only present when required by engine loading, rather than all the time as in a S/C. S/C systems make for a nice predictable delivery of power and torque, which is a big advantage in rear wheel drive cars.

Moray

 

very good point moray, but surely you can make the system bypass the supercharger at a certain point. so the s/c does not act as a big restriction.

 

Sam,

Nitrous Oxide is also used for this effect (in very small quantities) - it also cools the intake charge well below ambient.

The I-Club guys in the U.S. have been using this:

 

Sam,

Sunday's pretty busy for me so it's unlikely I'll make it along. Give me a rough idea what time you'll be there from/to and I'll try to squeeze a quick visit in. Failing that maybe see you at Knockhill next time around (mid-Sept?)

 

Super chargers usually run @ 5 to 7 psi way short of a turbo. Sounds like you are trying to reinvent the wheel. If thats what you want then thats what they do on the twin turbo so its already done for you

 

but i thought in twin turbo, each turbo supplies only two cylinders ?

is there a twin turbo set up with a small turbo feeding a bigger one ?

 

Eeeeerrr, that would be a sequential system

DJ

 

Sam wrote:
<I>"is there a twin turbo set up with a small turbo feeding a bigger one ?"</I>

Yes, the Legacy GTB has twin sequential turbos... and I pick mine up tomorrow

 

"sequential system " thats what i meant


colin
are you bringing it to star performance on sunday ? it will be good to have a look at how it is done

 

Hence my comment about seriously clever ducting and valves.

 

ooooooh

 

gavinP
i may actually have a problem with my inlet temps being too low . compared to a lot of people but this a different thread. last night i was trying sooooo hard to get 30 degrees but i have failed miserably.

colin
i will be there from 10:00 on wards probably as i will be measuring the inlet temps on all the cars going on the rollers. if not i will be going to KH on the last thursday of the month to try the car out.

sam

 

Isnt Nitrous Oxide the way for you to go Sam. After all you must have an unlimited supply at work?? You could buy a 50hp kit and connect a boost switch so that it switches off when you reach a certain boost pressure.Therefore eliminating lag while not overloading your engine. A push button would give you an extra 50 hp when you want it.
Beastie

 

Sam,

You mean like this?

 

Need for Speed (https://www.needforspeed.co.uk/index.asp) sell universal supercharger kits, they've fitted one to a 90BHP Saxo (VTR or VTS), it ran 146BHP on the rollers without lowering the compression ratio but as for using them to counter-act turbo lag, the super charger is belt driven so it will sap low-end power. The problem with using nitrous is you need to have the throttle open all the way to be the most effective which will not help the build-up of turbo pressure though the cheapest nitrous kit for EFI cars from Wizords Of Nos can deliver an approximate increase of 100BHP (engine probably won't) but it's supplied with 25BHP jets which are a waste of time

 

I would think that a 25bhp jet would work quite well on the Impreza - bear in mind that it only being used for a low-down kick and to pre-chill the intake tract.....

Thanks

Gavin

 

thanks guys keep them coming

so if it is such a good idea what has not anyone tried NOS then ?

where can i research this. i could be tempted

 

Sam,

 

This is going to be long post, I can feel it........

I run 50BHP jets on a Ford KA (Don't laugh!!!), it was supplied with 25BHP jets which isn't a lot, but given a standard KA is a mere 60BHP that's nearly a 50% increase but it didn't make much of a difference so I doubt a scoob will benefit from 25BHP jets, there are two major draw backs of using nitrous, the first being it needs a good air-supply, I know someone who blew up his KA on a Dyno because there wasn't enough air so be carefull!! The second is the fact that there are only a handfull of companies around the UK that will sell you Nitrous Oxide, I've still to find a local supplier :-( If you're considering using nitrous as an anti-lag device then why use it just for that purpose?!? I'm sure if a KA (1.3) can take 50BHP a scoob will take at least 50BHP :-) :-)

 

so what are you guys saying can you actually programme NOS to come at a certain revs ? or even better come in until a cetain boost pressure 10psi for example and then a pressure switch of some sort to switch it off ?!!

but i thought NOS was one of these all or nothing things so once it is on that is it.

sam

 

Bobfrog,

I think the issue with the amount used is more to do with trying to avoid high cylinder pressure at high revs - hence the low down use only.

I haven't used NOS so you certainly know more than I do but I would think using it at low revs will increase the percentage of NOS in the intake air anyhow(?)

I would speculate that the cooling effect may do more for power on an Impreza than the presence of the NOS....

The thread on I-Club discussing NOS is here:

 

Gavin, sorry for going off on a tangent, tend to do that often!! Anyhow to answer Sam's last post: The nitrous is activated by a switch under the throttle peddle, I use a progressive controller which with 50BHP jets will let 25BHP's worth of gas out then you can control the build up time to 100% over 2-10 seconds, this saves stress to the engine and saves gas. If anyone is interested in finding out exactly what Nitrous will do for you whether you then contact Trevor from Wizards of Nos on noswizard@highpower.freeserve.co.uk

 

the fastest groupB rally car of all was both supercharged and turbocharged.

That was the lancia delta S4


The turbo and supercharger were run in parallel.

The Lancia 037 was only supercharged using a 3 port roots unit linked with Kugelfischer mechanical fuel injection.