How much hp does it take to turn a blower ?

Hey guys, I'm wondering how much hp it would take to turn a 471 on a flathead ?
I know its all relative, but just a basic idea please.
thanks

 

All depends on the amount of over or underdrive you have, pulley and belt type also.
R&P BLOWER SERV. 319-234-8679

 

There is a 671 on a BBC and the owner mentioned that with the ratio it is currently driven (underdriven due to heating problems), he is making the same amount of HP with it as he would without the blower. ie, the blower is eating up quite a bit of HP - looks cool though.
This was stated after a close race with a normaly aspirated single carbed 400SBC in similar type/weight cars

 

Not sure how much it takes but we will soon find out!

 

You are gonna be negative HP......

 

oops

 

My memory is a bit foggy, but I recall that a 6-71 at 1:1 was something like 120HP to turn at full street boost of like 8, but it made enough to justify the loss. I'd 'guess' a 4-71 to be 2/3 of that? I hear a top fuel blower takes over 800HP at full boost if that helps. These days it might be more.

 

There is a thread, or somewhere in a thread that tells what the HP loss is.
I can't really remember, I drink way to much....

 

no matter what hp it uses. nothing looks more bad ass than a blower.

 

As stated above, it's relative depending on boost. However, you could reasonably expect ~50 hp to turn a modest 4-71 blower at street boost levels.

 

Not much help. But with my 427 BBC with no blower it took 100HP to make 430HP

 

chain drive!!! the question is not how much hp its gonna take to to turn it, it's how many fingers your gonna lose 1

matt

 

Pussy

 

^^^^ haha

 

Yeah, because sticking your finger in a Gilmer drive won't hurt at all.

 

im not against it fucko, relax

 

lol

 

If I remember correctly the rule of thumb is that it takes approximately 30% of the power out put to drive a Roots type blower. Higher boost and horsepower means higher losses, but the percentage stays pretty constant. This is a very elementary number based on typical street engine inefficiencies and gasoline. Rcve motor's will consume a much lower percentage at high Boost
So in other words if you are making 400 HP at the crank with a blower it is taking about 120 HP to make that power ~ in other words if you could make the blower 100% efficient, you would be making 520 HP.
In a Top Fuel car, they figure somewhere between 900-1100 HP is being eaten up by the Blower at the 50-70 lbs of boost that they run. Remember also that Screw Blowers are more efficient than Roots blowers and Nitro changes everthing

 

Not much because I have not smoked the belts yet.

 

Part of it is likely to be whether the basics of the motor are set up to optimize the use of a blower or not. You can't just stick a blower on any motor and then do a straight comparison. A non-blower motor will make more hp when set up properly as such than a similar motor that has been set up to use a blower but that doesn't have one on it. I am no expert by a long shot, but things like compression ratio, timing, cam and intake/head flow all are going to affect how efficient a blower is going to work for a motor. Obviously the key is for it to produce more power than it consumes whatever the situation. Assuming net max. hp output is a driving concern. But with old hot rods, that isn't always the biggest thing anyway. Pretty much any new car of decent performance can blow away an old hot rod anyway. So, no use in pumping up your chest with hp #'s when some punk in rice rocket could smoke you anyway.

 

I am running 2 5/8 v belts and the blower pulley is made from two rulleys from a large deck lawn mower. I am running low boost about 3 to 5 psi. I am guessing about 10 t0 20 hp with engine developing about 100 hp.

 

Hey Woodypecker, can I see some pictures of your pulleys, upper and lower and how you have your fan and generator set up ?
thanks man..

 

lets see 60 hp -20 to turn the blower +10 gain .50hp youll be down 10.i think my lawn mower makes 35.hhmmmm

 

Big Daddy had a display in his museum with his experimental dragster that used
a pressurized tank to replace the blower on the theory it took over 1000 hp to
turn the blower. Was not a successful experiment- but he tried it.

 

Would have had to have been a hell of a big tank at a very high pressure to have been enough to feed a 392+ hemi competitively down the 1/4 mile. I'm not sure what the uncompressed volume of air would be needed, but I guess someone with more brain power than me can figure it out based on cu of the block, total rpms/run and compression needed. But, my guess is a bored out 392 block would need a heck of a lot of compressed air to feed it for just one run. I can't imagine there is anyway to compress enough air into a small enough tank to make it work.

In theory, you don't even need the combustion if you have enough compressed air. If you can safely compress it that much, just let the air do the trick.

way OT but interesting:

 

I'm using my flathead JUST to turn my 471...don't really care about the end result, it just sounds SO COOL.

 

It would be nice to have a figure to kick around bench racing, but in the end, it just doesn't matter. Bolt on that 4-71, mind your timing, boost pressure and fuel and drive the shit out of it. Even at a mild 4-6 lbs of boost that little flatty will make some nice power (for a flathead....no offence) You might even spank a few Chevvie crate motors.

For reference, my 389 inch Pontiac makes 186 more horse at the wheels with the blower at 10% vs naturaly aspirated. She used to run 12s, now she runs 10s. I drive it every day but I have no idea what it takes to turn the blower...

Good luck, -Abone.

 

Hey guys this will not be any more guess work then any other response on this thread. Our experience with blowers is with a Top Alky Dragster,
Back when there was a war between helix and screw blowers.

At that time, Bob Drazey (PSI superchsrgerd) ran Hemi engines on a dybo. Results showed that a 14/71 helix blower used 735 HP to turn with air temp of
Around 350f. The screw blower used 275 HP with air temp of 175f. Blowers use power! You GUESS how much.
Mouse

 

Thanks for all the replies guys, I think this is goanna be fun no matter what.
Iv never had a blown engine, but I do have 4 running flatheads to play with,

 

We have an ex-V.P. monitering the raising of the atmospheric pressure as we speak.

This may make supercharging obsolete...