Super- and turbocharging - 'twincharging'

[doglegracing]

Interested in twincharging - where a supercharger assist with boost in low boost situations and the turbocharger taking over once it has spooled in high boost. This can be either in series where the S/C blows into the turbo or in parallel (where surge may be an issue).

Any suggestions on how to do this?

 

[NeilRoshier]

Kimbo perhaps you should read the book. The author has written 3 tuning books and is a well respected tuner with international experience. As I said it is best to take the statement in context, and that context should be the contents of the whole book.
I think I stated above that I was interested in mechanically driven forced induction for some of its specific advantages, and that is still the case. I am not anti-turbo in any way but wanted to find out more information of something that gets less 'press' than turbo's. I have not driven a turbo car on a track in a race. I did speak to a GT3 racer who was frustrated that he was being overtaken by the exiges as he had to be so careful (his thoughts not mine)
In the latest edition of EVO Gordon Murray has answered the question "presumably working on the SLR you've come to embrace the SC as a different way of gaining performance" His reply
"No. Given a totally open choice I'd always go for normal aspiration, for everything: weight, complexity, effecieny, drivability. Supercharging is much better than turbo charging for all the obvious reasons but also has its drawbacks. If you want 500hp, net, you've got to make 700 because 200 goes to driving the SC, and then you've got to cool that power. The small throttle response problem you can get over with byass valves and things. It'll never be normally aspirated but it's certainly a hell of a lot better than turbocharging"
I have not made my mind up which is better for me is this application, but again I am contibuting nothing to dongleracing's thread and will sign off. This is perhaps as discussion item for another thread if anyone has the energy!

 

[ProgressiveRacing]

Didn't realize there'd be as much "high-horsing" on this website, being an engineering forum and all.

kimbo,
Which turbo books do YOU recommend? I still haven't figured it all out, so I'm willing to read and learn. How bout that GT2 class racing... Corvette and Viper aint doing too bad.

-Allen

 

[patprimmer]

No arguement that turbo's produce the most power for the least parasytic loss.

However the claim that they convert lost exhaust gas heat is only partly true, as they also increase blow down pressure on the exhaust stroke, which pushes against the rotation of the crank, thereby creating a relative small parasytic loss.

I did own a Toyota Soarer MZ20 which had the M7GTE motor and automatic transmission. While it was a very comfortable, high performance, reliable, true GT coup, it had two interelated drawbacks.

When pushing hard through corners, that required controlled acceleration for best results, it either kicked down a gear and came strongly onto boost, or it changed up a gear and lost boost, sometimes 2 or 3 times in the one corner.

The option of manual overide of the automatic was not that successfull, as the shifter was vague and the gate design poor, which meant that it was hard to know what gear you were in, and it was to easy to overshift and select neutral.

With a supercharger, I could have squeezed the throttle without a downshift and got controlled, instantainous acceleration.

The technique of allowing for lag, can be usefull on a race track, but it still does catch a driver out occasionaly, such as when moveing through slower traffic, and someone does something unexpected, or the competitive driver deliberately hesitates at a critical time and therefore baulks you.

Turbo's are more efficient, but at times, they do create drivability problems. A positive displacement blower and a turbo compounded could give the best of both, but with relativly high parasitic losses compared to straight turbo.

I doubt if it is worth the extra complexity and weight, but it will give better power than a roots blower and better response than a turbo. It will still suffer somewhat if trying to feather the throttle on an automatic transmission car through a part power corner.

To dogledracing's question, It all depends on exactly what you want to do, and what is the net effect all the compromises for your particular application. Isn't that about the situation with almost every consideration when designing a car, or just about anything else.
Regards
pat

 

[Whittey]

That sounds like a problem with all automatics. Change the automatic to a stick and the problem goes away. Change turbo to naturally aspirated and you're still going to have a problem. Perhaps a reprogram of the tranny is in order?


-=Whittey=-

 

[kimbo1]

OK I agree this is taking too much energy - but one last breath!

The original question has been answered many times above,so this hijacking has not been wasted. the answer being - no there is no point twincharging. A lot of work and money for very little gain -the Lancia engineers seem to have come to that conclusion too.

Supercharged cars feel much better to drive - no argument about that from anyone

A turbocharged car is the way to go for racing if rules allow it - you don't need calculators or books to see this, but I agree as an engineer myself they will help you understand why. The guy driving the twincharged or supercharged car will be able to console himself that whilst he didn't win at least he had good throttle response.

Progressive racing - I don't recommend any books as I don't read them - my seemingly controversial opinion comes from 3 years of dyno tuning and driving some pretty good machinery myself. The most notable a turbocharged RB25 in a 240Z that made peak power at 7000 rpm, During a test drive I launched it at 2500 rpm with the ability to create huge wheelspin, and a 700 HP 535 BMW with flat torque curve from 3000 rpm which the owners grandmother could drive comfortably - and yes they both had lag, but minimal. That my friends is what I was talking about when I mention the latest technology.
but I'll butt out now anyway!!

 

[evelrod]

In reference to the "highjacking" of this thread---
I think this thread has been quite informative and I believe we have all learned something, EXCEPT, "doglegracing" who has not logged onto these forums since his original post on March 10,2003 !!!
No argument about street applications and few disagreements about race related blowers. New technology is improving supercharger science and whether mechanicaly or exhaust driven, we can (IMO) look forward to seeing many more OEM applications in the near future.
I also agree that it is possibly time to put this thread to rest.

Rod