Roots vs turbo

[1974dodgecharger]

Is a Roots harder on the engine than a turbo engine?  I been reading about how guys with their 383s and 440s stock run 15 to 20 psi of boost using turbo, but we cringe when we put 10lbs of boost on a Roots blower? 

I have my opinions on each one, but would like to hear opinions......

[red79]

One big difference is that it's tough to intercool a roots blower, so when you crank up the pulley ratio the incoming charge is hot and detonation prone. Turbos have a plumbing advantage, it's easier to run more boost and still cool the charge before it gets to the intake.

Additionally, a roots blower is a positive displacement pump with an efficiency that starts to drop dramatically around 10 psi. At that point, it starts making more heat than boost, a combined with the lack of intercooling, has pretty much hit its practical limit.

The flip side of the coin is that roots blowers work very well at lower boost pressures, and will live forever at their comfortable, low-rpm speeds. They will reliably move air all the way through the rpm range--no turbo lag, no screaming centrifugal unit, instant power on demand.

[myk]

Fascinating stuff.  I'd still go the blower route, myself...

[440]

Can't beat the looks of a roots blower.

Out of curiosity wouldn't a centrifugal blower be the best of both worlds?

[funknut]

Great video from a dude that knows his way around a forced induction engine.  Covers all power adders (except nitrous).

https://www.youtube.com/watch?v=oyeotHRZ-XI

[440]

That was a great interview, thanks 

[1974dodgecharger]

WOW great interview by him....liked what he said under 900HP roots is great for street, but if you want over 1k HP for street a turbo will do!!!!!

[66FBCharger]

Great interview. Seems like a very knowledgeable guy.
Thanks for sharing the video.

[chargerbr549]

My daily driver is a roots type supercharger on my 98 Bonneville and puts out about 8-10lbs boost stock, I get around 20 to 21 mpg in mixed driving and up around 30 mpg on the highway if I drive it reasonable, anymore it would be tough for me to go back to a normally aspirated motor especially when you can have almost instant torque at the touch of the throttle, you don't have to wait for your power! It's kind of fun when you line up beside a flashy BMW or Mercedes and blow their doors off then when I get up to the posted speed limit I back off the throttle and settle in then they usually come flying by me at a high rate of speed to show me who's boss I guess. LOL

[funknut]

Another video out recently comparing the more common blower styles:

https://www.youtube.com/watch?v=EHg2uqJvLOk

[Rolling_Thunder]

I'm building a mild 440 with an 8-71 roots on it for my 1964 Polara project. It is more in keeping with the times in all honesty. The turbo systems will make massive more power but realistically I am aiming for 650-700hp...    not massive numbers at all. The roots will fit with the old street fighter look. 

If I was going to go for massive HP I would definitely run a twin turbo set up on a low deck stroker with EFI - spin it to the moon and see what parts gave up first.

All depends on what you're going for.