blowers

« **on:** January 22, 2010, 07:46:57 PM »

so in my ponderings of life, i have been wondering what in the hell does 6-71, 8-71, 10-71 and so on really mean other than blower size?
cause i have no focking idea

and yes i am working on my post count

« **Reply #1 on:** January 22, 2010, 07:59:40 PM »

I believe it has to do with the diesel motor they originally came on. The 71 series diesel motors were 71 cubic inches per cylinder. so the 6-71 came on the 6 cylinder and the 8-71 came on the 8 cylinder and so on and so on.

« **Reply #2 on:** January 22, 2010, 08:08:00 PM »

It's from the original purpose for them, which was deisel engines, a 6-71 was designed for 6 cyl engines, the 71 is the cubic inches they would scavenge, or add, to the engine's size. In the old days you had your choice of a 6-71 or , nothing. Now there are 6-18 /71 blowers, the sizing is based on the volumetric efficiency of the supercharger. A 12-71 will charge roughly twice the amount that a 6-71 does, but you already knew that.

Mind you this is from about 15 years ago, after many, many beers and a 3 hour conversation with a guy that helped to develop them for the US Army Air Corps in the 40's.

There's some crazy ass math to calculate the cubic inches that blowers add, too much for my simple mind.

I had a 4-71 on a 296 CI flathead Ford, on the street, sucking through 4 Stromberg 97 2 BBL carbs, that was a handful!

« **Reply #3 on:** January 22, 2010, 08:14:01 PM »

thank you boys

i had no

idea now i am ejumakated

« **Reply #4 on:** January 23, 2010, 11:35:12 AM »

thats correct

« **Reply #5 on:** January 23, 2010, 12:58:03 PM »

If anyone needs more tech. stuff about s/chargers...feel free to contact my friend Tim @ www.superchargerusa.com

Question for ya:

Who knows why the rotors in a blower are alum. instead of steel ??

« **Reply #6 on:** January 23, 2010, 01:03:44 PM »

Quote from: enginedoctor on January 23, 2010, 12:58:03 PM

If anyone needs more tech. stuff about s/chargers...feel free to contact my friend Tim @ www.superchargerusa.com

Question for ya:

Who knows why the rotor in a blower is alum. instead of steel ??

Because...

Am I close?

GT

« **Reply #7 on:** January 23, 2010, 01:25:14 PM »

haha....A+ GT.......I shoulda known you'd nail it.....but I kinda wanted "Wet dream" to reply

« **Reply #8 on:** January 23, 2010, 01:27:12 PM »

Quote from: enginedoctor on January 23, 2010, 01:25:14 PM

haha....A+ GT.......I shoulda known you'd nail it.....but I kinda wanted "Wet dream" to reply

OIC, sorry enginedoctor, I didn't pick up on that....

Want me to edit, maybe she didn't see it...

« **Reply #9 on:** January 23, 2010, 01:30:45 PM »

« **Reply #10 on:** January 23, 2010, 01:32:49 PM »

Quote from: GT Jets on January 23, 2010, 01:27:12 PM

OIC, sorry enginedoctor, I didn't pick up on that....

Want me to edit, maybe she didn't see it...

Nope...imma justa havana gooda tima

« **Reply #11 on:** January 23, 2010, 01:41:08 PM »

ok guys and gals thanks for the input, now, splain when you overdrive it

« **Reply #12 on:** January 23, 2010, 01:45:30 PM »

Quote from: Ralph Brunt on January 23, 2010, 01:41:08 PM

ok guys and gals thanks for the input, now, splain when you overdrive it

From what I was told, a blower normally runs @ a 1:1 ratio with the crank speed. When you start changing pulleys you increase the speed that the rotors turn, thereby overdriving it. You can also underdrive them depending on your needs.

You want to see a cool setup, look up a Potvin blower. They're more efficient therefore they make more power for the same power taken to spin 'em.
Trouble is, they're kinda akward to set up

Here's a pic of a Potvin Blown 328 SBC

Here's a pic of the Hank Bender/Ronnie Hier blown Chevy on the cover of Nov. '58 Hot Rod mag. Very sanitary 283 with pruned 4-71 Potvin assembly. If I remember correctly, it was the World's Fastest Chevy at the time. Notice the port nozzles. This in '58. Fuel injection pump ran off of mag drive. Chevy kits were developed a little later and always had a common intake plenum. Made even more logical by Chevy's lack of valley cover. PDP

« **Reply #13 on:** January 23, 2010, 01:48:42 PM »

thanks skip

now does it matter what size pulley goes where? the reason i am asking is because willis has a real big pulley on the crank and a small one on the blower. The boys were giving him a hard time about it.

« **Reply #14 on:** January 23, 2010, 01:52:00 PM »

The bigger pulley goes on the crank snout, though you can run any size you want. Think of it like a 10 speed bike, the biggest sprocket on the cranks to the smallest sprocket on the rear wheel makes the most torque, also makes your legs tired faster, you go big to big and you're now making way more rpm, it's all dependent on the engine's needs.

« **Reply #15 on:** January 23, 2010, 01:56:56 PM »

Quote from: Ralph Brunt on January 23, 2010, 01:41:08 PM

ok guys and gals thanks for the input, now, splain when you overdrive it

ralph.....overdrive/underdrive . = it's the same principal as a naturally aspirated engine....To Low or To High C/R.

Depends on what u wanna build

« **Reply #16 on:** January 23, 2010, 06:06:37 PM »

Quote from: Marcsrollin on January 22, 2010, 07:59:40 PM

I believe it has to do with the diesel motor they originally came on. The 71 series diesel motors were 71 cubic inches per cylinder. so the 6-71 came on the 6 cylinder and the 8-71 came on the 8 cylinder and so on and so on.

Exactly right. Be careful of the 6V-71, 8V-71 etc. Not the same animal.

Quote from: Ralph Brunt on January 23, 2010, 01:48:42 PM

thanks skip now does it matter what size pulley goes where? the reason i am asking is because willis has a real big pulley on the crank and a small one on the blower. The boys were giving him a hard time about it.

Quote from: enginedoctor on January 23, 2010, 01:56:56 PM

ralph.....overdrive/underdrive . = it's the same principal as a naturally aspirated engine....To Low or To High C/R.

Depends on what u wanna build

1 to 1 is when both pulleys are the same size (Usually counting the gilmer teeth). Overdrive is the crank pulley larger than the blower pulley, and vice-versa. 1 to 1 Almost never used for our purposes. HdRider can explain all this much better than me, but I'll give it a shot. When to underdrive/overdrive really has to do with PSI of pressure induced at what rpm and the compression ratio of the host engine and cylinder pressures.

It's all about efficiency of the system for it's intended purpose.

Perfect, for the street or us, would be where your boost guage holds a pre-determined PSI reading across it's used rpm band, and cylinder pressures are not near excessive for the hardware in the bottom end. (More PSI for a lower C/R and less PSI for a higher C/R). Over/Underdriving becomes somewhat of an experiment for most of us to get there, but others, (Barry, Dave, Tom, etc) have the experience to get it right on a guess usually.

As far as Willis, depends on how much o/d it really has. If it's a huge difference, he could be spinning the blower nearly twice for every revolution of the crank which is going to wear the blower out but QUICK! I would think. He needs a bigger blower and probably more compression. Also, the faster you spin a blower, the more HP it takes at that speed, to spin it and the less effective it is! Could be why he's being given a hard time.

Then theres straight cut and helical cut rotors, sealed oil systems or shared.........etc, etc, lol.

Ray

« **Reply #17 on:** January 23, 2010, 06:15:13 PM »

Quote from: IRRebel on January 23, 2010, 06:06:37 PM

Exactly right. Be careful of the 6V-71, 8V-71 etc. Not the same animal.

1 to 1 is when both pulleys are the same size (Usually counting the gilmer teeth). Overdrive is the crank pulley larger than the blower pulley, and vice-versa. 1 to 1 Almost never used for our purposes. HdRider can explain all this much better than me, but I'll give it a shot. When to underdrive/overdrive really has to do with PSI of pressure induced at what rpm and the compression ratio of the host engine and cylinder pressures.

It's all about efficiency of the system for it's intended purpose.

Perfect, for the street or us, would be where your boost guage holds a pre-determined PSI reading across it's used rpm band, and cylinder pressures are not near excessive for the hardware in the bottom end. (More PSI for a lower C/R and less PSI for a higher C/R). Over/Underdriving becomes somewhat of an experiment for most of us to get there, but others, (Barry, Dave, Tom, etc) have the experience to get it right on a guess usually.

As far as Willis, depends on how much o/d it really has. If it's a huge difference, he could be spinning the blower nearly twice for every revolution of the crank which is going to wear the blower out but QUICK! I would think. He needs a bigger blower and probably more compression. Also, the faster you spin a blower, the more HP it takes at that speed, to spin it and the less effective it is! Could be why he's being given a hard time.

Then theres straight cut and helical cut rotors, sealed oil systems or shared.........etc, etc, lol.

Ray

..........Good coverage!...Thanks!

« **Reply #18 on:** January 23, 2010, 06:46:40 PM »

In willis's case he is drag racing blown fuel jet and is running a PSI blower at over 30 psi for a corrected compression ratio of over 50:1 compression. The whole boat is set up on a stand alone engine management system and is tuned with a laptop.

« **Reply #19 on:** January 23, 2010, 07:06:56 PM »

Drag racing, of any sort, is a different matter altogether.......and not to a certain degree.

I remember talking to Kenny Bernstein's crew cheif (His chassis were made ,back in the day of his Budweiser King F/C days, by a guy working out of a 4 car garage near Oil City, PA where I worked. Bill Kachek was his name) Anyway, he told me at the traps, the 14-71 they were using took over 400 hp to turn it over and they were running well over 45PSI at that point, if memory serves me correctly.

That is the extreme, not the norm. As I said, depends on it's intended purpose!

Today, I don't think they're approaching this pressure number, and are far exceeding any number Bernstein ever even approached at 1320 feet and they're doing it in 1000 feet today. (Bernstein was among the first into the 300 MPH club).

Ain't technology great?

I was talking street and daily use stuff, BTW, but if yu want to break chit and run on the ragged edge, that's a totally different matter.

Ray

« **Reply #20 on:** January 23, 2010, 08:16:03 PM »

Quote from: enginedoctor on January 23, 2010, 01:56:56 PM

ralph.....overdrive/underdrive . = it's the same principal as a naturally aspirated engine....To Low or To High C/R.

Depends on what u wanna build

As long as blowers don't have impeller charts I'm good!!!

« **Reply #21 on:** January 23, 2010, 08:37:43 PM »

Quote from: Stevecat on January 23, 2010, 08:16:03 PM

As long as blowers don't have impeller charts I'm good!!!

X2!!! Blower pulleys can be changed out easy! Impellers??? well..........

Ray

« **Reply #22 on:** January 26, 2010, 07:18:08 PM »

I made an excel spread sheet that will give you the underdriven or over-driven ratio by putting the numer of teeth in a cell for the upper and lower pullies. I am going 10% overdriven this year and a dyno tune as well. I was underdriven 10% last year and only 6.5 Lbs of boost.
Anybody who want the spread sheet just let me know.
T.J.

« **Reply #23 on:** January 26, 2010, 07:44:37 PM »

Quote from: TJS Nordic on January 26, 2010, 07:18:08 PM

I made an excel spread sheet that will give you the underdriven or over-driven ratio by putting the numer of teeth in a cell for the upper and lower pullies. I am going 10% overdriven this year and a dyno tune as well. I was underdriven 10% last year and only 6.5 Lbs of boost.
Anybody who want the spread sheet just let me know.
T.J.

TJ-

I'd love to have that spreadsheet. Can you email it to me? luckiestiff@gmail.com

« **Reply #24 on:** January 26, 2010, 07:56:04 PM »

Quote from: Luckie Stiff on January 26, 2010, 07:44:37 PM

TJ-

I'd love to have that spreadsheet. Can you email it to me? luckiestiff@gmail.com

Sent.
T.J.

Ralph Brunt

Marcsrollin

Luckie Stiff

Ralph Brunt

wet dream

enginedoctor

GT Jets

enginedoctor

GT Jets

GT Jets

enginedoctor

Ralph Brunt

Luckie Stiff

Ralph Brunt

Luckie Stiff

enginedoctor

IRRebel

enginedoctor

Marcsrollin

IRRebel

Stevecat

IRRebel

TJS Nordic

Luckie Stiff

TJS Nordic