Supercharger for the exhaust????

[rennat]

So after reading about all of this twincharger stuff (SC + turbo). I was thinking... Could you have a belt driven style supercharger that sped up the exhaust gases before it hit the exhaust turbine so you could get boost sooner, and then even flow more at the top end? I realize its a crazy idea (to me at least) but could it be done?

Thanks for any input.

 

[mavisky]

I don't see how that would work at all, it'll just provide a huge restriction for the turbo.

 

[dave99gst]

Twin turbo with 1 of the turbo's being smaller provides this function.

 

[RayPeters]

So after reading about all of this twincharger stuff (SC + turbo). I was thinking... Could you have a belt driven style supercharger that sped up the exhaust gases before it hit the exhaust turbine so you could get boost sooner, and then even flow more at the top end? I realize its a crazy idea (to me at least) but could it be done?

Thanks for any input.

The theory has been tested before. The supercharger would help scavange (draw exhaust ) out of the engine, but the limit is the engine itself. The supercharger on the intake side of the engine has the unlimited air of the world to draw in and compress, but put on the exhaust it is restricted by the engine displacement so the amount of available gas to compress is no more than the air that has already gone through the engine. The turbo already gets that much now. The limit of the performance improvment this will net you is the change in pressure at the exhaust valves of the engine. Lower that say 4 psi and you have the same thing as 4 more PSI boost. But after you factor in the pumping losses of the device, it is better to just use the pistons we're already moving. .



So the short answer is no it wouldn't do what you want. Sorry,

 

[Defiant]

Turbochargers are spun more by exhaust heat than gas flow.

What became of the electric-assist Garrett was putting on some SAAB turbos?

 

[brute]

Twin charging works, but it is no where near financially effective. The theory is good, it's just that in real life there are so many other factors that need to be addressed and ultimately cost more money. For example, say the supercharger was for low-end, pushing into the turbo. Once the turbo spooled, the supercharger would still be spinning, but at a much faster RPM. This would make it go into a terrible efficiency. So to combat this, you might be able to use a clutch on the pulley, almost like the a/c clutch. Have something to disengage the supercharger at a certain point.

But I digress. If you are worried about turbo lag, get a smaller turbo. Besides, lag is overrated anyway.

For more info about twin-charging setups, you can Google the twin-charging kit HKS used to make for MR2's. Also check out the old Class B Lancia rally car. That thing was banned because it killed people.

 

[rennat]

Well i just got done researching the lancia, and that thing was amazing. Kind of a sad story though...

I was just wondering about the idea though... Ya never know if anybody else has the same idea or question...

And its a semi-twin turbo kit. I was thinking if you just had the supercharger hooked up to the exhaust, then it would eliminate the extrea intake piping, and all of that garbage. I dont really like TT setups because of that... I think it would be a crazy idea... no idea how it would work though... maybe one day they will make it happen.

Thanks for the input though.

 

[Raph]

Twin charging works, but it is no where near financially effective. The theory is good, it's just that in real life there are so many other factors that need to be addressed and ultimately cost more money. For example, say the supercharger was for low-end, pushing into the turbo. Once the turbo spooled, the supercharger would still be spinning, but at a much faster RPM. This would make it go into a terrible efficiency. So to combat this, you might be able to use a clutch on the pulley, almost like the a/c clutch. Have something to disengage the supercharger at a certain point.

But I digress. If you are worried about turbo lag, get a smaller turbo. Besides, lag is overrated anyway.

For more info about twin-charging setups, you can Google the twin-charging kit HKS used to make for MR2's. Also check out the old Class B Lancia rally car. That thing was banned because it killed people.

Going a bit offtopic,the Class B was amazing!

But back tom present day, notice how the WRC cars of today seem to be just as fast as the Class-B of yesteryear? Funny huh? technology has come a long way.

 

[spinninfwdlaser]

It would be kind of like the variable geometry turbo, but not as effective. Porsche uses VGT on the new 911 with insane sucsess. That would be a good route.