roots blower info

mopar or no car

mopar or no car

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Apr 9, 2008
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I'm not sure where to ask this, but can someone post the flow rates of roots type blowers and the air consumption rates of a stock 5.9. Thanks

Jordan
 
Strictly speaking, flow rates of Roots-type blowers aren't important... their volume is.

Large diameter 6:71s displace 411 cubic inches (5.505" rotors are only 339)

8:71s displace 436 cubes per revolution.

Obviously, these are theoretical displacements.
 
XLR8R said:
Strictly speaking, flow rates of Roots-type blowers aren't important... their volume is.

Large diameter 6:71s displace 411 cubic inches (5.505" rotors are only 339)

8:71s displace 436 cubes per revolution.

Obviously, these are theoretical displacements.
Click to expand...

Why wouldnt the 8:71 displace about 568 cubic inches? Just wondering... I always thought that it was based off a 71ci cylinder X the amount of cylinders.

But thats what I get for thinking..:bang:hehe:
 
he's right

XLR8R said:
Strictly speaking, flow rates of Roots-type blowers aren't important... their volume is.

Large diameter 6:71s displace 411 cubic inches (5.505" rotors are only 339)

8:71s displace 436 cubes per revolution.

Obviously, these are theoretical displacements.
Click to expand...

Thats right, i was thinking of the 8-71
I used to run a 6-71 years ago, lots of fun![ 411 cid ]


Aaron, i believe the number representes the engine that it feed. IE: a 6-71 feed a 6 cylinder diesel that was 426 cid, or 71 cid per cylinder. And so on, many of the others were made after market for the sole reason of racing, i know now that there are some 16-71's around, but many now are going to the big screws.
Ryan
 
if you want to mess around with a cheap roots type blower, find an Eaton M112 of the supercharged Cobras and Lightnings. It would be interesting to see someone make a mount that bolts to where the gridheater/intake manifold originally was and set the supercharger/water to air intercooler set up (oem cobra) just in front of the brake booster. Run a custom pulley on the alternator so you can add a belt, faba tensioner and figure out the gear ratios......yank off the throttle body on the supercharger and for the turbo, throw on a nice 71mm turbo and hold on? :ft:
 
98andahalf said:
if you want to mess around with a cheap roots type blower, find an Eaton M112 of the supercharged Cobras and Lightnings. It would be interesting to see someone make a mount that bolts to where the gridheater/intake manifold originally was and set the supercharger/water to air intercooler set up (oem cobra) just in front of the brake booster. Run a custom pulley on the alternator so you can add a belt, faba tensioner and figure out the gear ratios......yank off the throttle body on the supercharger and for the turbo, throw on a nice 71mm turbo and hold on? :ft:
Click to expand...

i can get a supercharger from a 01 lightning with everything for 800 if any one wants it
 
what the hell!?!?! someone stole my idea!!! back to the drawing board.....that is f-in sick, tho!!!
 
Smokem nailed it. I have seen that pic for a year or two, even have it in my phone, and just can't get it out of my head-and prob won't till its under my hood.

I want to build a project truck that is under boost at idle(2-3 psi?). Then depending on how it would run, it will have atleat one, maybe two turbos that would feed the blower. After its runnig, I might see about fabing a bypass around the blower, but to start-I'm not going to worry bout it.

I need to find lots of info. I need to find how many cfm the blowers flow at various rpms, as well as how many cfm the cummins will consume at various rpms so I can choose the right blower.

Ebay has blowers, and I have a good local detroit shop that prob has several laying around, but my question is-how hard is it to take a blower that was driven off the gear train of a detroit, and make it belt driven? There are several machine shops around locally that could prob fab something I'm sure, just wondering if a kit exists.

Thanks for any help,

Jordan
 
There's no need for a bypass around a downstream blower.
 
I tried to find books about blowers at the library, no luck. Can anyone reccomend one? One that helps a guy pick out the right blower. Or, can a detroit shop provide a lists of models and cfm per rpm?

Jordan
 
I'd just throw an 8-71 or 6-71 or whatever you can find on there and see how it works. Your CFM will depend on how hard you drive the blower.
 
Here, I'll give you a better answer....found this on another thread---

Here are some general displacement figures for standard helix (30 degrees of twist) roots blowers: A small rotor 6-71 displaces approx 339 cubic inches per revolution, a standard rotor 6-71 is 411 cubic inches, a B&M Megablower is 430 cubic inches, and an 8-71 is 438 cubic inches.
One thing to keep in mind, due to air leakage between the case and rotor tips AND between the ends of the rotors and the ends of the case, these blowers will not be able to move that exact amount of air/fuel per revolution, especially when the boost comes up. It will be less.
Another dimension to note is that a 6-71 rotor is 15” long, the 8-71 rotor is 16” long, a 10-71 rotor is 17" long, a 12-71 rotor is 18" long a 14-71 rotor is 19" long and the 16-71 rotor is 20” long. All rotors are the same diameter with the exception of the small rotor 6-71.

So that means at 3000rpm at 40% over, a normal rotor 6-71 would give

411x4200/1728=998 cfm.
 
The above pic of Piers' setup would be equivalent to what size blower? 4-71?6-71? 8-71? I'm thinking about going a little on the big side to make it easier to adjust blower rpms to provide adequate cfm.

Jordan
 
Also would be easier to fab the stuff once for a bigger blower, and only have to buy one blower.

Jordan
 
well i dont know how many cfm the stock ford supercharger flows but it keeps 8-12 psi on a 5.4 till 6000rpm depending on the size of the pully (i had a 01 lightning before this truck)
 
some thoughts

none of these roots style blowers start to make any serious boost untill higher rpms, and for the most part thier efficiency is marginal, unless your using one of the newer eaton/whipple style blowers. They also create tremendous heating of the intake air which is why many of the performance applications liek the Ford M112 uses an integral water/air intercooler.

So in order to get the rpm of the blower high enough to make decent boost you will need a to run a jackshaft, and step up pulleys

I've seen it done using a centrifugal blower like the procharger, on a Ford diesel with very good results boost and power wise,

Another issue is Packaging which becomes an issue, and also, none of these blowers bearings were designed for prolonged high speed running so longevity will also become an issue once jackshaft driven to get the necessary boost out of them.

I beleive, if memory serves, that is why the whipple setup in the previous pic became a dead end - they didnt run a jackshaft to get the rpm/boost levels up so the actual usable boost in our rpm range was marginal at best, and wasnt worth the cost and fabrication
 
The pic that smokem posted is from a thread on the tdr site. Here's what nascar mark said with the pic.
Here's a first look at what found it's way on to one of our 5.9's... 8psi at idle and 25psi with a blip of the throttle.
Click to expand...

I had forgotten what they were running for boost with that setup. 2-3psi at idle might be setting my sights too low. I'll have to re read the whole thread-all 14 pages.

Jordan
 
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