JAY4SPEED

Hi,
I was curious about how many miles can you get out of a Roots type blower such as a 6-71 or 8-71 before you have to get the teflon on the rotors replaced?

Thanks,
Jay

ede

depends on how fast you spin it. i had a friend with one on a 65 chevy II that he drove vert little, 1000 miles a year and he changed seals ever winter, but i tihnk he just liked doing it.

83 Crossfire TA

iTrader: (2)

Roots blowers with Teflon edge seals were not designed for street use, and you'll be replacing them a lot.

Some positive displacement blower manufacturer’s have started coating their rotors with an epoxy to increase efficiency, which works by taking up the clearances between the machined surfaces instead of sealing the edges.

JAY4SPEED

Thanks for the info!

I was under the impression that teflon lined blowers were on the streets. I need to check with BDS and see what they have. I'm very interested in learning as much as I can about roots blowers. I'm trying to do all the research I can to get my feet wet. Is there any particular websites that you might recommend to educate me on blower efficency and tuning. As for as I understand to this point, its better to get a bigger blower that puts out more displacment and turn it slower than getting a small one and turning it faster. I've learned about the teflon seals a while back and was wondering typical usage out of one set. I guess a non lined rotor would be better for the street. Am I on the right track?

Thanks again!

Damon

A bigger blower turning slower will be more efficient. They rate the blowers in terms of their adibiatic efficiency. A measure of it's efficiency in pumping a volume of air and how much it heats it up while doing so (that's an over-simplification). A centrifugal style blower that uses an impeller wheel will typically be around 70%. Roots blower will be more like 55-60%.

However, only a roots blower will make full boost from the instant you nail the gas. A centrifugal builds it fairly linear with engine RPM.

Teflon lined rotors are, as stated by others, not for the street. They help prevent any back-flow past the rotors but they wear out real quick on the street. Street blowers typically just run tight tolerances between the rotor lobe and blower case. On the order of .008-.012" clearance. Yeah, some air leaks back through and hurts efficiency but there's no seal to ever wear out. If you keep dirt from getting sucked in (always run a good aircleaner) they'll last just about forever.

I just installed a little Weaind 142 roots blower on my 78 Malibu (my third such installation of a roots blower- I'm no expert) and just poked around on different manufacturers websites and made a few calls.
There are books available from all the usual places (Summit, or your local speed shop) that deal specifically with supercharging in it's various forms. I beleive it is put out by HP Books.

Kingtal0n

I've got a B&M 144 Teflon-Sealed "Street Blower" It works great, never replaced the seals, puts out 8 PSI on my crazy 355. Has been in use for over 2 years without problem, although I like the idea of weiand's new non-teflon 142 blower, and will probably go to that soon. There are advantages to using a smaller blower and spinning it faster, such as there is less time for air to leak back out because its spinning so fast, and it takes alot less horsepower to turn these things than a big clunky 671. Also, I have seen 671 being "Streeted" and they tended to be a little un-friendly at stoplights... I have had experiences with both big and little blowers and prefer the little blowers, but thats just me. Its all about fun right?

83 Crossfire TA

iTrader: (2)

Out of curiousity, what's 'unfriendly' about them at stop lights? Is it idle/surging issues?

One thing that most people don't realise about positive displacement blowers is the increadable pressure pulses that you can get out of them, the rotors feed the engine 'gulps' of air. On brother's car tuning was initially really wierd because we were finding that these pulses were almost timed with the capture frames that the Haltech that he was using was displaying, so every other frame would read something like 8psi, and all the ones in between would read something like .2psi.

The way to fix that in anything that is boost refrenced is to put a restriction and a blead so you basically see the average, something that he hasn't tried since we got a good tune like it was.

BTW, his setup is seeing between 2-3000 blower rpm at idle, so he fixed the wonky idle from the blower by setting up the bypass to only close at WOT...

Kingtal0n

thats what i meant, the big gulps of air would pull the car forward and cause a really bouncy idle... it was fun for a while, but got very annoying. the sound it made was very Odd too, the idle of the car would jump up and down real quick... made a cool sound... i suppose a bigger converter would have helped with the brake pulling... but would have also removed some of that low end torque these blowers are great for. bigger cams seem to make the bouncy idle worse...

JAY4SPEED

I really appreciate the info guys! Before I put down my hard earned cash, I will be buying those books. I've though about going centrifucal but my car isn't fuel injected its carbed. I didnt want to go to the expense of fuel injection just to get a centrifrucal blower on there. I have seen the hats you can put carbs on and the pressure boxes you can put the carbs in. To me, nothing has WOW factor like a polished blower peeking through the hood. But now 'yall have me thinking that the roots setup may not be the best for my setup I was planning. I have a 406 with a Th350 and a 3500 stall 3.73 gears. I know the roots would be building boost most likely as i'm stalling up the converter. The car typically stalls at 3200 before the brakes cant hold it back. I was just hesitating because I'd lose most my benefit from the boost of initial torque increase because of my high stall converter. I have minimal traction isues, the car hooks really well. Am I going the wrong way here?

Christos

I can agree with you there! The roots blowers look awesome.

I e-mailed Ati 3 years ago about their C-supercharges, and asked them if it could be used with a carb, like on a ZZ4
crate engine, and I was told, "yes we have a kit".

So I would contact them first. You can run a centrifugal s-charger with a carb.

I like those best, because roots create lots of heat, and aren't as efficient as the new centrifugal superchargers. ATI is my personal favorite, because it includes an intercooler. More boost, less detonation.

Kingtal0n

I would go lower with the stall. I had a 3800 converter 10" on mine and it was like a rocket, but I got bad gas mileage and I lost all my low end wonder... I went to a 2400 and its just as fast, and more economical not to mention I can creep out of the hole from a stoplight and no one hears my blower then I nail it and the tires light up... so much fun.