Difference between small and big superchargers? Norval, help!
Race Director
Joined: Nov 2002
Posts: 12,142
Likes: 54
From: Taylor Michigan
Thanks, I know little about blowers this makes sense, I did know that
blowers create some heat thats one more reason I was wondering
how they get away with the compression on pump gas. It seems like from
reading on this thread that you would want to start out with very low
comp. have the blower turning at least crank speed or overdriven, if you
start out with high comp. turn the blower very slow sounds like you kind of end up with a lazy supercharged engine.
blowers create some heat thats one more reason I was wondering
how they get away with the compression on pump gas. It seems like from
reading on this thread that you would want to start out with very low
comp. have the blower turning at least crank speed or overdriven, if you
start out with high comp. turn the blower very slow sounds like you kind of end up with a lazy supercharged engine.
This National Champion is both, show and go......
Le Mans Master
Joined: Apr 2006
Posts: 5,403
Likes: 95
Sort of, lazy yes. some of this is correct but for sure you wind up a loser. Roots {GMC} blowers are instant HP or they are set up wrong. No waiting around. There's usage of show, go, or both. Most are the first scenario unless it`s a track {strip} usage. We use tight magnesium case tefloned superchargers and overdrive the hell out of them. When stabbed the response is immediate and I mean "immediate" and constant. How else would it be possible for Top Fuel Dragsters to cover a 1/4 in 4.5 seconds while driving with several G`s pushing you back in the seat. And that's done almost before you can say the phrase. ...
This National Champion is both, show and go......
This National Champion is both, show and go......
Like I said I know little about supercharges but believe I would
go with pretty low comp. a small enough blower for some overdrive.
Underdrive is not sounding good to me. That lincoln looks like my 63
and those funny cars look a little dated.
Last edited by Little Mouse; Nov 6, 2007 at 07:50 PM.
Le Mans Master
Joined: Apr 2000
Posts: 5,202
Likes: 10
From: cincinnati ohio
St. Jude Donor '09
"Also, yellow72 what's the deal with the Pro Street 250 and 256 blowers? I've never even heard of them. What applications are they good for?"
They look like shorter (read smaller) versions of a 6-71
http://www.holley.com/types/Small%20...0%20Series.asp
They look like shorter (read smaller) versions of a 6-71
http://www.holley.com/types/Small%20...0%20Series.asp
Le Mans Master
Joined: Apr 2000
Posts: 5,202
Likes: 10
From: cincinnati ohio
St. Jude Donor '09
You never know who you may be talking with on the net
http://www.nitroalley.net/theJourney.htm
Le Mans Master
Joined: Apr 2006
Posts: 5,403
Likes: 95
Altereds my friend not funny cars
You never know who you may be talking with on the net
http://www.nitroalley.net/theJourney.htm
You never know who you may be talking with on the net
http://www.nitroalley.net/theJourney.htm
Race Director
Joined: Nov 2000
Posts: 11,872
Likes: 12
From: Waterloo ontario Canada
Torque/horsepower
4000/730T/560HP,
5000/790T/750HP,
6000/760T/870HP,
7000/710T/950HP.
You don't put that power to the ground with street tires. I once had the car go completely around at the top end of 3rd gear when I got a little too cocky with the throttle.
But when it comes to playing with other hot cars it is like taking a gun to a knife fight.
Nobody stands a chance.
Le Mans Master
Joined: Apr 2006
Posts: 5,403
Likes: 95
This is a typical torque/horsepower rating for a motor like mine. Again it depends on how fast I spin the blower.
Torque/horsepower
4000/730T/560HP,
5000/790T/750HP,
6000/760T/870HP,
7000/710T/950HP.
You don't put that power to the ground with street tires. I once had the car go completely around at the top end of 3rd gear when I got a little too cocky with the throttle.
But when it comes to playing with other hot cars it is like taking a gun to a knife fight. Nobody stands a chance.
Torque/horsepower
4000/730T/560HP,
5000/790T/750HP,
6000/760T/870HP,
7000/710T/950HP.
You don't put that power to the ground with street tires. I once had the car go completely around at the top end of 3rd gear when I got a little too cocky with the throttle.
But when it comes to playing with other hot cars it is like taking a gun to a knife fight.
Nobody stands a chance.system from Blower Drive Service. I know you have the carbs well worked out, but carbs give it a street car look the fuel injection
gives it even more of the race car look that a blower gives.
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Race Director
Joined: Nov 2000
Posts: 11,872
Likes: 12
From: Waterloo ontario Canada
I have roughly $20,000 in the motor and this is the end. I don't want to spend any more. I did up the drive to 27% overdrive and it should give about 8 more pounds of boost but that is it. No more big modifications. I will spend more time with the horse if future.
Burning Brakes
Joined: Jan 2007
Posts: 1,057
Likes: 4
From: Concord Calif
You are right as far as GMC is concerned. Don't care what Hot Rod or such thinks. 8 is the number of cylinders and 71 is the Cubic Inch cylinder it is used on. These blowers are just that, they in stock form do not make boost, they blow out the exhaust from the chamber on a two cycle disel engine.
Burning Brakes
Joined: Jan 2007
Posts: 1,057
Likes: 4
From: Concord Calif
The 6-71 is a good blower to use if you have the room and all it requiers to run a GMC style blower. One thing to think about is how much boost you think you will need or want. 10 pounds boost is alot to use for a stock GMC. Trying to make much more at RPM will stall the air and litterally back the air back out the intake. That is one reason for teflon rotors but not the only one. One way that works well for me is the "air trap" the blower. That is machine a step on the leading edge of the rotors that act like an air scoop. This will increse the boost at a much lower rpm much like a teflon blower. I would not recomend a teflon blower on the street at all either air trap it if you need more. And yes do keep the rpm down below 6,000 for sure on the street no more than 5000 would be good.
Le Mans Master
Joined: Apr 2000
Posts: 5,202
Likes: 10
From: cincinnati ohio
St. Jude Donor '09
You are right as far as GMC is concerned. Don't care what Hot Rod or such thinks. 8 is the number of cylinders and 71 is the Cubic Inch cylinder it is used on. These blowers are just that, they in stock form do not make boost, they blow out the exhaust from the chamber on a two cycle disel engine.
Burning Brakes
Joined: Jan 2007
Posts: 1,057
Likes: 4
From: Concord Calif
Drifting
Joined: Sep 2003
Posts: 1,325
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From: FRANKLIN GA
There was a guy on here a while back that was fabricating a fuel injection sys for his blower. Did anyone hear if it ever worked?
Burning Brakes
Joined: Jan 2007
Posts: 1,057
Likes: 4
From: Concord Calif
Don't know about that person trying but any of the mechanical injection systems out there can be made to work on the street with proper tunning. The biggest issue in those systems would be in the starting as the fuel drains from the fuel pump when not running and requiers priming to start up. Mounting a tank higher that the pump will not work well as the fuel will drain into the engine. But a "sruge" tank with a float system on it would work or an electric pump could also be used for starting. In any case too rich is how you want to erra on and not lean as that is a back fire and costly. The system I run can be made to run just fine at slow speeds and wide open also. Just requiers an understanding of whats going on in the system.
Race Director
Joined: Nov 2000
Posts: 11,872
Likes: 12
From: Waterloo ontario Canada
Don't know about that person trying but any of the mechanical injection systems out there can be made to work on the street with proper tunning. The biggest issue in those systems would be in the starting as the fuel drains from the fuel pump when not running and requiers priming to start up. Mounting a tank higher that the pump will not work well as the fuel will drain into the engine. But a "sruge" tank with a float system on it would work or an electric pump could also be used for starting. In any case too rich is how you want to erra on and not lean as that is a back fire and costly. The system I run can be made to run just fine at slow speeds and wide open also. Just requiers an understanding of whats going on in the system.
That jet seperates the idle from the cruise from the main jets and remember main jets don't come in until higher then normal speed limits.
The side effect of this jet is a big increase in gas mileage.
As for running lean the word lean only applies to wide open throttle and not cruise conditions. YOu can not run too lean at idle.
Maximum temperature is at 14.6 or 7 and leaner mixtures then that just produce a cooler running motor.
Maximum fuel economy is at 15.4 or leaner.
Again why is mechanical fuel injection better then a well set up carb???
Burning Brakes
Joined: Jan 2007
Posts: 1,057
Likes: 4
From: Concord Calif
What is the advantage of fuel injection? If you have to go to all that trouble why is it better then a carb?? Our carbs LACK a transfer port jet. Add that and you really improve a carb's mileage.
That jet seperates the idle from the cruise from the main jets and remember main jets don't come in until higher then normal speed limits.
The side effect of this jet is a big increase in gas mileage.
As for running lean the word lean only applies to wide open throttle and not cruise conditions. YOu can not run too lean at idle.
Maximum temperature is at 14.6 or 7 and leaner mixtures then that just produce a cooler running motor.
Maximum fuel economy is at 15.4 or leaner.
Again why is mechanical fuel injection better then a well set up carb???
That jet seperates the idle from the cruise from the main jets and remember main jets don't come in until higher then normal speed limits.
The side effect of this jet is a big increase in gas mileage.
As for running lean the word lean only applies to wide open throttle and not cruise conditions. YOu can not run too lean at idle.
Maximum temperature is at 14.6 or 7 and leaner mixtures then that just produce a cooler running motor.
Maximum fuel economy is at 15.4 or leaner.
Again why is mechanical fuel injection better then a well set up carb???
Well the word "better" depends on what one wants from the system. A carb system probaly be best for any kind a fuel economy. A carb may be better for the masses that would run a blower also from the stand point you can buy it to work pretty close out of the box. But the mechanical system will make more power bar none and be ajustable at every pointin the rpm range based upon fuel presure which is rpm related. And not sure where your coming from the stand point you say you can't run to lean? and that it just runs cooler, I have burst panels and blower pieces that says you do and came run way lean and hurt these things. I have had a panel pop at ideal also from being to lean. But anyway people just need to run what makes them happy and that they understand some. These will always be someone who will make more power than you and do it with less also. So run what makes you smile.
Thread Starter
Melting Slicks
Joined: Sep 2004
Posts: 2,412
Likes: 3
Ugh, what is this a debate of FI vs. Carbs? Pros and cons to both, Norval is making 1K hp, how many of you need a k when listing your hp? He obviously knows what he's doing. Show some respect. 
Le Mans Master
Joined: Apr 2006
Posts: 5,403
Likes: 95
I only brought up the fuel injection as a race car looks thing, the
BDS fuel injection would not make any more power or any better fuel milage I know Norvals not going to just throw away $1600 dollars
or whatever he payed for them worth of carbs to go buy fuel injection.
I think it was probably eight/ ten yrs ago BDS showed up at the
street rod nationls with the fuel injection, I watched them start up
a 6/71 small block run it for a couple minutes, it was inside a
building. Someone starting from scratch with a new blower project
might want to go with the fuel injection but it would cost more then
two carbs you would have to want it for the looks value.
BDS fuel injection would not make any more power or any better fuel milage I know Norvals not going to just throw away $1600 dollars
or whatever he payed for them worth of carbs to go buy fuel injection.
I think it was probably eight/ ten yrs ago BDS showed up at the
street rod nationls with the fuel injection, I watched them start up
a 6/71 small block run it for a couple minutes, it was inside a
building. Someone starting from scratch with a new blower project
might want to go with the fuel injection but it would cost more then
two carbs you would have to want it for the looks value.
Last edited by Little Mouse; Nov 8, 2007 at 04:34 PM.