I believe the smallest GM blower is a 3-73 according to the records. I'm sorry but I am unable to attach the file but it is available on Google
I run 6psi of boost, but I wouldn't say my motor is old....all new with the exception of the block and crank. 6psi gives me 48% by my math...
That's a cool blower. 4-5 psi of boost won't put 30-40% more power to your ass. 6 psi isn't putting 48% more to your ass either. The math you guys are using isn't inclusive of all that's going on. It takes power to turn the blower, and turning it faster takes more power. Making boost increases heat and heat spreads out the air molecules and that reduces power. What you can figure out with singular equations is the effective compression ratio that the engine will see but don't forget to factor in the elevation above sea level. Guys in Colorado can run way more boost than guys on the Cali coast. There is a point of diminishing returns, and after that point things begin to go negative.
Chopped, Not to hurt your math or expectations at all. Running the calcs is a good t starting place to give you an idea of what you may expect from a given modification. It is a good staring place at best. I use math and believe that math is a good thing so don't misunderstand what I am trying to suggest. In order for the calculations to be in the least bit accurate you have to taker into account every other aspect of your build. Volumetric efficiency for example, is a big factor. But don't count out something as simple as combustion chamber size and design, or cam selection, or valve size or even valve grind and angles of the vale surfaces. We could go on forever with this but there is no reason. I sometimes fathom a guess when someone says if I build this engine this way what can I expect but I always have to admit that it is a guess. An engine dyno is a good place to actually get percent of performance change but one must first establish a baseline and go from there as an engine dyno vary and even the exact same engine with the exact same tune can show major performance differences from one dyno to the next. Gary you are correct that an under driven blower makes less boost that an over driven blower. the heat that some of us are referring to has to do as much with blower size as it does boost. But yes an under driven blower should make less boost and theoretically produce an intake charge at a lower temperature. A lot of the discussion here has to do with blower size and efficiency. A larger blower that produces greater CFM because it has a larger surface area in theory should produce an intake charge with a lower temperature at a given boost pressure number then the smaller with less surface area. yes the larger compressor can be under driven to produce the same volume of air as the smaller one @ 1:1 but it is not necessarily the fact that it is under driven that makes the charge less heated. It is an efficiency factor that produces the same amount of boost at a lower temperature.
well, if I take into account the power loss of driving a blower AND the huge HP used to spin an automatic transmission, My car will hardly move under it's own power.....you guys kill what used to be a fun hobby....sigh. I guess I should scrap the whole thing....
well, if I take into account the power loss of driving a blower AND the huge HP used to spin an automatic transmission, I guess I really won't see a 48% increase. Fixed it for you Quit your bellyaching and whining. That's what takes the fun out of learning. Would you like it better if no one cared enough to highlight the facts and push the reset button. Easier on the ego for you if folks just sat back and laughed instead of posting? No Johnny, 6x7 is not 38. Johnny says fuck you, quits school and licks boots now.
Based on 14.7 PSI atmospheric at sea level, 5 PSI would be 1/3 more air flow = 1/3 more HP. But, friction in the drive line would not increase so if that friction ate up part of your original HP, the 1/3 boost would feel like more. McCulloch claimed a 40% increase in rear wheel HP with 5 PSI boost and this is quite possible. I might add, it is hard to get that much increase with a conventional hop up without reducing power at low RPMS (while increasing it at high RPMS). It is true that a positive displacement blower takes more HP to drive, than a centrifugal blower. How much it would take to drive such a small blower with low boost I don't know, but if they drove it with 2 V- belts (see picture in original post) I doubt it was more than 10 HP. This is all pretty academic anyway. What difference does it make exactly how much HP it is worth. Nobody is going racing with such a setup at this time. If it gives the old flatty a little extra pep, and looks cool, what more do you need?
A good cheese burger. I seldom take a vendors/manufacturers word for performance claims. They are in the business of selling you something. I remember a guy that I worked with that was going to have a 500 hp 327, he took the claimed performance gains for each part he was going to bolt on, headers, air cleaner intake and etc. I chuckled inside myself (yes it was a day that I had a little self control) and just let him dream. We all got to have dreams.
it seemed to have plenty of power as I drove it into the lake this morning. Now I need to find something to fill the void in the garage....maybe a hot tub.
I don't know how much HP a GMC 2-71 blower will give a flathead but it should do something. Who cares how much if you are not racing it. Have some fun, look cool, a little extra HP is always nice.
I thought this was pretty cool: http://www.jalopyjournal.com/forum/threads/extremely-rare-bandimere-supercharger.356581/
I went looking for pics of a 1-71...the blower looks almost like someone just slapped the endplates together with no ham in the sandwich! Stolen image...Now I hope Moriarty finds one of these...and builds a lawn tractor. And maybe an extra blower, to add to his current lawnmower!
Be careful with them hot tubs, they can hurt your feelings too Ok so you believe that your math gives you 6psi boost and that means 48% more power. Since there's a something for nothing factor in this math, let's take it out by a thought experiment. So we will stick your engine in the dyno and run it to get a base line and measure the boost. Next let's take the blower belt off of your crank and affix the blower belt to an separate engine placed next to it, this pony engine will turn the blower. Dyno run 2 - the pony engine is making 6 psi boost for your engine. Question, does your engine show more power or less with the boost the same provided by the pony motor? Of course is shows more and significantly more than if your engine were driving the blower. Dyno run 3- the goal of this run is to match baseline power by varying the boost provided by the pony motor. We want to know 2 things, how much boost is needed and what the pony motor is using for power to do it. The. We take those numbers and use them to figure out the inefficiency and what's being wasted out of your 48% something for nothing. Yes the engine is getting 48% more air but that's at a cost so the engine is not making 48% more at the flywheel. There's a huge drag at the front of the crank, that is a negative value in the equation. Maybe another way for you to look at it.
well, until I drag it out of the lake, I'll never know...but I'm sure you can calculate how to do that too...
Not really, I've never had a temper tantrum and done things like that so not much practice reversing them
The engine itself has friction and pumping losses so the stock HP will be - those. If you add a supercharger those losses will not increase, in fact the pumping loss may be less thanks to the supercharger. But, the supercharger will use up some HP. The upshot is, you may not get 1/15 more HP for every pound of boost but it should be in the ballpark.
Here is a thought, an HP gain is an HP gain whether it is usable HP or not. lets do a hypothetical, suppose one bolts a blower on engine A which makes a base HP 20. We screw a blower on it that makes it have a 10% increase in HP. so now it has 20+10% or 20+2. Now engine A makes 22 HP but it takes 3 HP to drive the blower, so your usable HP now becomes 19 HP but it still has to make 22 HP in order for you to drive the blower and have 19 HP to use. Yes the blower was wasted time and money but you still increased your HP to 22 HP.
They need to do exactly that. Stupid should hurt. Well fellas it has been fun but I have to go make bread. Not to be confused with get bread.
Do you use one of those bread making machines or do it by hand. How do you calculate the thermal efficiency of the yeast rising at sea level?
You should know that a 6-71 driven by an electric motor is a superior tool for kneading your bread dough... also, the mild heating provided by the thrashing rotors is perfect for the yeast. Be sure to rinse off any nitromethane before use.
Life is a shit sandwich, the more bread you have the less shit you have to eat. Unless you possess the secrets to defy physics and the laws of energy. Then you get the something for nothing synergy thing going. That's when you get bread for nothing and your chicks for free
holy shit strap the blower on the flattie forget all this other shit and drive it...........done and happy......
I no longer live at sea level and while I would like to give it a whirl I haven't tried to cook bread in death Valley yet so below sea level is entirely out. I haven't tried a roots blower to knead the dough yet but I will, I happen to have a 4-71 to play with, won't make as much bread but won't cost as much bread to turn. I will give you all this, I seldom eat shit sandwiches and bay at the moon, I don't really like bread that much.
I think that was just Bruce Lancaster's rye wit, Beaner. Bread from a blower ain't for Eaton. It would taste Dyer.
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