*** Special on Magnuson Heartbeat this Fall **
09-12-2017, 08:43 PM
#1381
Le Mans Master
I'm going to play devils advocate here... 
Bernoulli's principle;
As flow increases, pressure decreases. Normal venturi effect, right? However, as the speed slows down later (past the restriction), the pressure increases.
I cannot remember (will have to go search) exactly where the low pressure was measured from, but if it was "around" the restriction, that's to be expected.
Check out this animation - when the tester changes the location of the air supply here. Notice how the small diameter flows faster (thus much lower pressure), but then the pressure is actually HIGHER downstream when the flows slows back down...
Playing in refining flow dynamics & trouble shooting makes me curious here...
Now this would be worthless if the low pressure exists downstream of the restriction.
Found image:
It would be curious to learn what the pressure is just upstream of the rotor, PAST the TB restriction...
Bernoulli's principle;
As flow increases, pressure decreases. Normal venturi effect, right? However, as the speed slows down later (past the restriction), the pressure increases.
I cannot remember (will have to go search) exactly where the low pressure was measured from, but if it was "around" the restriction, that's to be expected.
Check out this animation - when the tester changes the location of the air supply here. Notice how the small diameter flows faster (thus much lower pressure), but then the pressure is actually HIGHER downstream when the flows slows back down...
Playing in refining flow dynamics & trouble shooting makes me curious here...
Now this would be worthless if the low pressure exists downstream of the restriction.
Found image:
It would be curious to learn what the pressure is just upstream of the rotor, PAST the TB restriction...
09-13-2017, 12:32 AM
#1385
I'm going to play devils advocate here...
Bernoulli's principle;
As flow increases, pressure decreases. Normal venturi effect, right? However, as the speed slows down later (past the restriction), the pressure increases.
I cannot remember (will have to go search) exactly where the low pressure was measured from, but if it was "around" the restriction, that's to be expected.
Check out this animation - when the tester changes the location of the air supply here. Notice how the small diameter flows faster (thus much lower pressure), but then the pressure is actually HIGHER downstream when the flows slows back down...
Playing in refining flow dynamics & trouble shooting makes me curious here...
Now this would be worthless if the low pressure exists downstream of the restriction.
Found image:
It would be curious to learn what the pressure is just upstream of the rotor, PAST the TB restriction...
Bernoulli's principle;
As flow increases, pressure decreases. Normal venturi effect, right? However, as the speed slows down later (past the restriction), the pressure increases.
I cannot remember (will have to go search) exactly where the low pressure was measured from, but if it was "around" the restriction, that's to be expected.
Check out this animation - when the tester changes the location of the air supply here. Notice how the small diameter flows faster (thus much lower pressure), but then the pressure is actually HIGHER downstream when the flows slows back down...
Playing in refining flow dynamics & trouble shooting makes me curious here...
Now this would be worthless if the low pressure exists downstream of the restriction.
Found image:
It would be curious to learn what the pressure is just upstream of the rotor, PAST the TB restriction...
The 5 in. of vacuum was observed at the orifice circled in yellow on that cutaway image. Bear in mind that image depicts a Camaro blower with a much shorter inlet. With the C6 inlet, the throttle body, and the "Venturi" is actually about 4" ahead of that port, which is actually located in the blower inlet cavity, well ahead of the rotors. I didn't expect to find that kind of vacuum there, to be honest. I'm no physicist or airflow engineer, but based on my rudimentary understanding of these things, that must mean that the rotors aren't getting unrestricted airflow, hence the vacuum, no? Or have I just confused the f@ck outta myself??
09-13-2017, 12:33 AM
#1386
I was starting to wonder if he builds them...
09-13-2017, 01:38 AM
#1388
Okay, I think I stopped laughing enough to type again, LOL...
I'm only - for the sake of discussion - proposing this *possibility*.
So, the pressure drops very low at a restriction, then increases again after the restriction. The faster the flow has to go, the lower the pressure will drop. It's a weird phenomena in that the pressure goes from high to LOW back to (almost as) High..
Imagine the restriction the TB.
See diagram for visual aid. So it would be expected the pressure is low at the restriction, but higher again when the velocity slows back down (wider flow area) AFTER the restriction.
So typically, pressure profile would be:
P1 = 10
P2 = -1
P3 = 8
In a carb, the venturies are used to vaporize the fuel from a sharp drop in pressure and fine atomization & mixing with the fast air.
So if P3 pressure is still really low I'd guess you'd gain big time from bigger TB. If it's not much lower (at P3) then I'd guess not much gain. I started to say specific " Hg but I would be totally guessing.
You're gonna gain, just slinging theory on how much you're gonna get...
I'm only - for the sake of discussion - proposing this *possibility*.
So, the pressure drops very low at a restriction, then increases again after the restriction. The faster the flow has to go, the lower the pressure will drop. It's a weird phenomena in that the pressure goes from high to LOW back to (almost as) High..
Imagine the restriction the TB.
See diagram for visual aid. So it would be expected the pressure is low at the restriction, but higher again when the velocity slows back down (wider flow area) AFTER the restriction.
So typically, pressure profile would be:
P1 = 10
P2 = -1
P3 = 8
In a carb, the venturies are used to vaporize the fuel from a sharp drop in pressure and fine atomization & mixing with the fast air.
So if P3 pressure is still really low I'd guess you'd gain big time from bigger TB. If it's not much lower (at P3) then I'd guess not much gain. I started to say specific " Hg but I would be totally guessing.
You're gonna gain, just slinging theory on how much you're gonna get...
Last edited by Chiselchst; 09-13-2017 at 02:01 AM.
09-13-2017, 08:31 AM
#1390
This is all good stuff.
The science of airflow/aerodynamics really fascinates me, and always has. I wish I knew more about it.
But here's my thinking on the venturi effect. I know from experience that a 4 barrel carb, which has 4 venturi in it, sitting a couple of inches at most above the base plate, will generate significant vacuum in the venturi/boosters to pull fuel through the boosters and metering circuits and vapourize the fuel. Yet, it is generally accepted that any carb that generates measurable vacuum at the base plate (just a couple of inches below the venturi) will be deemed to be a restriction, and most of the time, extra power can be found with a bigger carb (with the requisite fueling adjustments). So, if I'm seeing 4-5in. Hg in the blower cavity, in front of the rotors, some 4 inches behind the throttle body, I do believe that's from a pressure drop from the venturi effect of the TB. But the million dollar question is, isn't that, in and of itself, the problem? Isn't that exactly what I want to eliminate? Won't that result in a power gain from the rotors getting better airflow? I have no idea, is my answer.
I really have no idea what I'm going to gain, because I'm sailing into uncharted waters here, and I won't have a dyno sheet at the end of it to prove what I've gained either. I am hoping that my scans will show that I'm getting more airflow.
But, Hell, at this stage, I'd settle to just have the frickin throttle blade not slam shut at the top of 3rd!
But I do know that the ZR1 guys do gain HP from just changing the air filter assembly forward of the TB (including that convoluted, twisted rubber bellows that we've inherited from the ZR1 on the Heartbeat) and have seen big gains from going up on throttle body size, with the requisite porting behind the TB. Ditto for the Holden, Camaro and Caddy Hbeat boys.
Now, I realize that most of them are spinning their rotors 20,000+rpm, whilst I'm spinning mine a maximum of 17,500, so I don't know if I'll even get 10hp out of all of this effort, but I'll take whatever I can get. Like I said, if I can just get the TB to stop flutter and slamming shut, I'll be happier than a hog in mud.
Look at the photo below. Now, imagine that you're an air molecule that had the misfortune to be sucked into that air filter and had to make your way through that twisted maze to get to the rotors of the supercharger. Imagine what that experience would be?
So, let's see what I can cobble together and whether it makes sense for anyone to waste time on this. I will share my results with you and be honest about what my findings are. And if, like the ECS tensioner debacle, it turns out to appear to not be worth the effort, then I'll share that too.
The science of airflow/aerodynamics really fascinates me, and always has. I wish I knew more about it.
But here's my thinking on the venturi effect. I know from experience that a 4 barrel carb, which has 4 venturi in it, sitting a couple of inches at most above the base plate, will generate significant vacuum in the venturi/boosters to pull fuel through the boosters and metering circuits and vapourize the fuel. Yet, it is generally accepted that any carb that generates measurable vacuum at the base plate (just a couple of inches below the venturi) will be deemed to be a restriction, and most of the time, extra power can be found with a bigger carb (with the requisite fueling adjustments). So, if I'm seeing 4-5in. Hg in the blower cavity, in front of the rotors, some 4 inches behind the throttle body, I do believe that's from a pressure drop from the venturi effect of the TB. But the million dollar question is, isn't that, in and of itself, the problem? Isn't that exactly what I want to eliminate? Won't that result in a power gain from the rotors getting better airflow? I have no idea, is my answer.
I really have no idea what I'm going to gain, because I'm sailing into uncharted waters here, and I won't have a dyno sheet at the end of it to prove what I've gained either. I am hoping that my scans will show that I'm getting more airflow.
But, Hell, at this stage, I'd settle to just have the frickin throttle blade not slam shut at the top of 3rd!
But I do know that the ZR1 guys do gain HP from just changing the air filter assembly forward of the TB (including that convoluted, twisted rubber bellows that we've inherited from the ZR1 on the Heartbeat) and have seen big gains from going up on throttle body size, with the requisite porting behind the TB. Ditto for the Holden, Camaro and Caddy Hbeat boys.
Now, I realize that most of them are spinning their rotors 20,000+rpm, whilst I'm spinning mine a maximum of 17,500, so I don't know if I'll even get 10hp out of all of this effort, but I'll take whatever I can get. Like I said, if I can just get the TB to stop flutter and slamming shut, I'll be happier than a hog in mud.
Look at the photo below. Now, imagine that you're an air molecule that had the misfortune to be sucked into that air filter and had to make your way through that twisted maze to get to the rotors of the supercharger. Imagine what that experience would be?
So, let's see what I can cobble together and whether it makes sense for anyone to waste time on this. I will share my results with you and be honest about what my findings are. And if, like the ECS tensioner debacle, it turns out to appear to not be worth the effort, then I'll share that too.
Last edited by CI GS; 09-13-2017 at 08:32 AM.
09-13-2017, 08:47 AM
#1391
Le Mans Master
If you flew for a living, you more than likely wouldn't have to worry about this as just about any commercially used aircraft doesn't have carbs any more. Heck, most of them don't have pistons either. Went to Alaska earlier this year. Even the float planes are nearly all turbine powered nowadays.
Yeah, the SS is gone. Traded it for a pickup. Figured I'd get a whole lot more use out of the truck. It's getting close to prime fishing weather and I didn't have a truck reliable enough to tow my boat any distance. That, and I'm transitioning into retirement. Income stream isn't what it was. I have a '69 Camaro SS in the garage with a sick 406 small block to play with. I'll fix the old motor if it's not too bad. If it is too bad, it's LS3 time
09-13-2017, 08:53 AM
#1392
Burning Brakes
Just dam fascinating. There has to be a aerospace engineer or tech that could throw you a bone on this quest. On the science of air flow. Please someone from Boeing or NASA chime in, Help Sammy keep his sanity
09-13-2017, 08:57 AM
#1393
Le Mans Master
This is all good stuff.
The science of airflow/aerodynamics really fascinates me, and always has. I wish I knew more about it.
But here's my thinking on the venturi effect. I know from experience that a 4 barrel carb, which has 4 venturi in it, sitting a couple of inches at most above the base plate, will generate significant vacuum in the venturi/boosters to pull fuel through the boosters and metering circuits and vapourize the fuel. Yet, it is generally accepted that any carb that generates measurable vacuum at the base plate (just a couple of inches below the venturi) will be deemed to be a restriction, and most of the time, extra power can be found with a bigger carb (with the requisite fueling adjustments). So, if I'm seeing 4-5in. Hg in the blower cavity, in front of the rotors, some 4 inches behind the throttle body, I do believe that's from a pressure drop from the venturi effect of the TB. But the million dollar question is, isn't that, in and of itself, the problem? Isn't that exactly what I want to eliminate? Won't that result in a power gain from the rotors getting better airflow? I have no idea, is my answer.
I really have no idea what I'm going to gain, because I'm sailing into uncharted waters here, and I won't have a dyno sheet at the end of it to prove what I've gained either. I am hoping that my scans will show that I'm getting more airflow.
But, Hell, at this stage, I'd settle to just have the frickin throttle blade not slam shut at the top of 3rd!
But I do know that the ZR1 guys do gain HP from just changing the air filter assembly forward of the TB (including that convoluted, twisted rubber bellows that we've inherited from the ZR1 on the Heartbeat) and have seen big gains from going up on throttle body size, with the requisite porting behind the TB. Ditto for the Holden, Camaro and Caddy Hbeat boys.
Now, I realize that most of them are spinning their rotors 20,000+rpm, whilst I'm spinning mine a maximum of 17,500, so I don't know if I'll even get 10hp out of all of this effort, but I'll take whatever I can get. Like I said, if I can just get the TB to stop flutter and slamming shut, I'll be happier than a hog in mud.
Look at the photo below. Now, imagine that you're an air molecule that had the misfortune to be sucked into that air filter and had to make your way through that twisted maze to get to the rotors of the supercharger. Imagine what that experience would be?
So, let's see what I can cobble together and whether it makes sense for anyone to waste time on this. I will share my results with you and be honest about what my findings are. And if, like the ECS tensioner debacle, it turns out to appear to not be worth the effort, then I'll share that too.
The science of airflow/aerodynamics really fascinates me, and always has. I wish I knew more about it.
But here's my thinking on the venturi effect. I know from experience that a 4 barrel carb, which has 4 venturi in it, sitting a couple of inches at most above the base plate, will generate significant vacuum in the venturi/boosters to pull fuel through the boosters and metering circuits and vapourize the fuel. Yet, it is generally accepted that any carb that generates measurable vacuum at the base plate (just a couple of inches below the venturi) will be deemed to be a restriction, and most of the time, extra power can be found with a bigger carb (with the requisite fueling adjustments). So, if I'm seeing 4-5in. Hg in the blower cavity, in front of the rotors, some 4 inches behind the throttle body, I do believe that's from a pressure drop from the venturi effect of the TB. But the million dollar question is, isn't that, in and of itself, the problem? Isn't that exactly what I want to eliminate? Won't that result in a power gain from the rotors getting better airflow? I have no idea, is my answer.
I really have no idea what I'm going to gain, because I'm sailing into uncharted waters here, and I won't have a dyno sheet at the end of it to prove what I've gained either. I am hoping that my scans will show that I'm getting more airflow.
But, Hell, at this stage, I'd settle to just have the frickin throttle blade not slam shut at the top of 3rd!
But I do know that the ZR1 guys do gain HP from just changing the air filter assembly forward of the TB (including that convoluted, twisted rubber bellows that we've inherited from the ZR1 on the Heartbeat) and have seen big gains from going up on throttle body size, with the requisite porting behind the TB. Ditto for the Holden, Camaro and Caddy Hbeat boys.
Now, I realize that most of them are spinning their rotors 20,000+rpm, whilst I'm spinning mine a maximum of 17,500, so I don't know if I'll even get 10hp out of all of this effort, but I'll take whatever I can get. Like I said, if I can just get the TB to stop flutter and slamming shut, I'll be happier than a hog in mud.
Look at the photo below. Now, imagine that you're an air molecule that had the misfortune to be sucked into that air filter and had to make your way through that twisted maze to get to the rotors of the supercharger. Imagine what that experience would be?
So, let's see what I can cobble together and whether it makes sense for anyone to waste time on this. I will share my results with you and be honest about what my findings are. And if, like the ECS tensioner debacle, it turns out to appear to not be worth the effort, then I'll share that too.
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CI GS (09-13-2017)
09-13-2017, 08:57 AM
#1394
Burning Brakes
The reason I asked was what you're describing happens when a carbureted airplane engine, with a fixed pitch prop, is slowed down to little or no load. Manifold heat has to be applied or the carb can freeze up...even with outside air temps well above freezing. With the throttle blades mostly closed, it creates a faster moving air flow, which cools the air. It's been a long time since I last studied that as I haven't owned an airplane in the last 30 years. I think I got it right..
If you flew for a living, you more than likely wouldn't have to worry about this as just about any commercially used aircraft doesn't have carbs any more. Heck, most of them don't have pistons either. Went to Alaska earlier this year. Even the float planes are nearly all turbine powered nowadays.
Yeah, the SS is gone. Traded it for a pickup. Figured I'd get a whole lot more use out of the truck. It's getting close to prime fishing weather and I didn't have a truck reliable enough to tow my boat any distance. That, and I'm transitioning into retirement. Income stream isn't what it was. I have a '69 Camaro SS in the garage with a sick 406 small block to play with. I'll fix the old motor if it's not too bad. If it is too bad, it's LS3 time
If you flew for a living, you more than likely wouldn't have to worry about this as just about any commercially used aircraft doesn't have carbs any more. Heck, most of them don't have pistons either. Went to Alaska earlier this year. Even the float planes are nearly all turbine powered nowadays.
Yeah, the SS is gone. Traded it for a pickup. Figured I'd get a whole lot more use out of the truck. It's getting close to prime fishing weather and I didn't have a truck reliable enough to tow my boat any distance. That, and I'm transitioning into retirement. Income stream isn't what it was. I have a '69 Camaro SS in the garage with a sick 406 small block to play with. I'll fix the old motor if it's not too bad. If it is too bad, it's LS3 time
09-13-2017, 09:10 AM
#1396
You sold the SS!?
What kind of truck? Whatever it is, I'm sure there's a supercharger in its future.
A '69 Camaro with a built, blown LS engine would be really cool. Just sayin...
09-13-2017, 09:11 AM
#1397
Flat tappet cams are nothing but trouble nowadays, since they've just about stopped formulating oil with zinc in it.
A roller cam make so much more power with less wear...
Last edited by CI GS; 09-13-2017 at 09:13 AM.
09-13-2017, 09:15 AM
#1398
09-13-2017, 09:25 AM
#1399
It's hard to figure out where most of the restriction is: the throttle body itself or a combination of that plus the bellows? That's why I'm changing them both.
09-13-2017, 09:26 AM
#1400
Le Mans Master
Truck is a new Chevy half ton 4x4 Z71 crew cab. I may leave this one alone and concentrate the craziness to the toys.