Turbos and Superchargers

[Dom]

What happens if you have a turbo/supercharger system where the turbo blows into the supercharger?

[brettp]

the car goes really fast theres a bloke in hot rod magazine done twin turbos on a super charged mustang think that was around the 1000 bhp mark

[emu]

Nissan did it years ago, to a fairly unlikely subject. Had quite an effect on its performance though........

 

http://autospeed.com/A_110662/cms/article.html

 

Lancia did it to the Delta S4 too

 

The way i understand......The supercharger provides the boost at the lower revs then a big turbo, which would normally be dead laggy, takes over at the top end.

[Dom]

I've contemplated this a few times. I've read numerous threads where people go down the route where the supercharger disengages at a certain RPM/boost and the turbo takes over (as in the case of the Super Turbo) but I don't really fancy that.

 

Would having the supercharging compressing the already compressed air effectively multiply the pressure? Like a 2 stage system or something?

 

I fancy the whine of a supercharger and the whoosh of a turbo

[Lardy]

when i had a mk1 mr2 there was a bloke in the states(where else!)who had a turbo and supercharger he said and remember this is from memory that it drove superb over 350bhp pulled from the off no lag supercharger cut off and turbo took over supposed to be a bit slow i dont think

[Dom]

Right well if anyone's got a pinto turbo manifold they want to get rid of then gimme gimme gimme

[Conor]

What happens if you have a turbo/supercharger system where the turbo blows into the supercharger?

 

Err, that's not really a good idea and usually its the other way round - the supercharger being there to cover the period before the turbocharger kicks in.

 

A turbocharger only blows once the engine has reached a certain speed. A supercharger blows from the start.

[Vista]

What happens if you have a turbo/supercharger system where the turbo blows into the supercharger?

 

Err, that's not really a good idea and usually its the other way round - the supercharger being there to cover the period before the turbocharger kicks in.

 

A turbocharger only blows once the engine has reached a certain speed. A supercharger blows from the start.

 

Agreed, Stick the hair drier before the blower and it will just act as a restictor on the inlet until it winds up to speed.

[Dom]

Hmmm seems to be a fair few mixed views, either it'll be a big restriction on the inlet or it'll make big power.

 

I've just ordered a book on turbo/supercharging and one on nitrous. I shall consult these tomes

 

 

But I guess there really is only one way to find out

[bmxdave]

A Supercharger can only compress so much air. Once its reached its point its cant compress anymore. So once the turbo spools up, if it creates more boost then the supercharger wouldnt it then become a restriction on the turbo?

 

Wouldnt you need some sort of electromagnetic or mechanically weighted cut off (which i believe the Eaton chargers from the SLK had some sort of cut off) and then some type of bypass for the turbochargered air to go through?

 

Its been done before but i think it has as many cons as pros.

[Dom]

Well my thinking is this, I know it's not true to all blowers as there are several types. (got all the main three!)

 

A supercharger compresses air with a static compression ratio, the main drawback is that the amount of air they can move per revolution is the same no matter what the RPM. Supercharger RPM is governed by the size of the pulleys driving it, the larger the crank pulley or the smaller the charger pulley the faster it will spin. This is when they are over-driven to get more boost from the same engine RPM, this increases the parasitic drag of the charger and decreases its efficiency which leads to increased charge temps, the more overdriven a charger the less power it creates compared to the increase of power taken to drive it. If a charger running at peak efficiency that had a static ratio compression ratio of 1.5 was boosting 7psi it would mean that it was compressing the atmospheric pressure of 14psi (roughly) and that the resulting manifold pressure would be 21psi in total (atmo + 7psi boost).

 

If a turbo was added that had boost set at 7psi the pressure between the turbo and the supercharger inlet would be 21psi instead of the normal atmo 14. This would turn the charger into a boost multiplier and the resulting boost from the charger would be (7psi inlet x 1.5 cr) 10.5psi. Discounting the atmo air.

 

My idea is instead of increasing the amount a supercharger can boost by, increase the pressure of the atmosphere into the charger by using a turbo. Then using an electronic boost controller you can vary the amount of boost by varying the turbo speed/pressure. This should hopefully increase the efficiency of the charger as well.

 

 

 

Phew! This is all rattling around in my head at the moment so I needed to write it out. Hopefully it all makes sense even though there are many factors to consider, other ratios and sizes and pressures etc etc as well my mathematical skills aren't great so I've probably made a hash of those calculations.

 

Hopefully someone will catch my drift