Landracing Forum
Tech Information => Technical Discussion => Topic started by: Jonny Hotnuts on November 16, 2009, 05:32:41 PM
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Lets say you mount a turbo on a NA engine.
On this engine you remove the compressor side of the turbo.
On the shaft to the remaining turbine you connected a drive mechanism (belt, gear or other) that would mechanically drive the turbine faster than it would spin with the exhaust flow spinning it with 100% efficiency.
I would think that you could (especially with proper cam timing) be able to gain motor efficiency by reducing pumping losses (and even go into positive numbers) to increase HP on any NA motor without calling it supercharged. I am not sure but I could also see that with cam timing overlap you could also begin bringing in air/fuel into the cylinder.
I am not suggesting I am going to try this.....
I am only bringing this concept up for discussion on the viability of the concept.
BTW:
If anyone sets a record using this....remember where you heard of it and make sure to call it the "hotnuts suck charger".
~JH
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Sounds like a really cool experient. :cheers:
For LSR, first problem would be convincing someone it was not "turbo-compounding" which I guess is illegal. It would look just like it.
Creating a partial vacuum at the exhaust port during the exhaust cycle is normally done by the design of the exhaust header. You might even make things worse by trying to scavenge with a pump.
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JHN,
How fast do you think the turbo on you motor turns? Probably over 100,000 rpm at big boost so to get the compressor driven up to this speed you would need to have probably a 10:1 ratio between the engine crank and the compressor snout. That will typically require at least a pulley ratio and one gear set that will give you the 10:1 ratio. And if you look at it this is exactly what people like Pro-Charger are doing.
I have proposed several times on this forum that you need to mount a Pro-Charger on your engine and then the hot side of a turbo, and make it BIG, then connect a shaft between the turbine and the Pro-Charger with a sprag type over riding clutch. So the engine drives the blower but when the exhaust driven tubine gets up to speed it will start driving the blower and if it is really large it will also start driving the engine thru the blower's drive system. This is a compound engine. And remember at 60,000 rpm it only takes an additional 100 inch- pounds of torque from the turbine to make 100 hps being added to the engine crank. Now this would be efficient as you are using heat from the exhaust, which is approx 35% of the total power made by the engine, to drive both the compressor but also the engine.
Only time and money prevent me from doing this!!!
Mostly money!!
Rex
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I'd think that if you hooked a supercharger or turbocharger to the intake or exhaust and were driving it -- it would be supercharged to the SCTA.
Stan
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I'd think that if you hooked a supercharger or turbocharger to the intake or exhaust and were driving it -- it would be supercharged to the SCTA.
Stan
Stan, I hear ya.
But every definition of "supercharger" states that it is a device to force air "INTO" a motor. I could see an argument for saying that there is nothing about a vacuum device to suck air out.
If I were a SCTA official....I would have a problem with it!
JHN,
How fast do you think the turbo on you motor turns? Probably over 100,000 rpm at big boost so to get the compressor driven up to this speed you would need to have probably a 10:1 ratio between the engine crank and the compressor snout. That will typically require at least a pulley ratio and one gear set that will give you the 10:1 ratio. And if you look at it this is exactly what people like Pro-Charger are doing.
Pro-Charger, Vortex, Paxton....these are all models of how I thought the experiment unit could be driven....that and a larger than needed turbine section if it was used as a traditional turbo on that engine. Maybe something off a big diesel truck?
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My thought is that you'd get the mixture through faster, but it's on the wrong side so wouldn't be able to compress any air in the cylinder once the exhaust valve had closed. I think the boost would be minimal and you'd still have the parasitic drive using up power. Might be a loss rather than a gain.
Just my thoughts.
Pete
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If you really want to do this i have a Mack turbocharger that is pretty big or one off of an 8:92 Detriot that I could donate to the effort.
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....pushing it in, or pulling it in is still creating a super-charge.........
and definately not normally aspirated...
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I'm just saying that the effect is on the wrong side of the valve so that you'd get a vacuum after the valve rather than a compression before it. I doubt that there would be very much benefit if at all.
Pete
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I doubt it could beat tuned-length headers. Still sounds fun though.
And yes, you'd have to use the compressor side of the turbo. Hay goes in the other end of the horse.
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My thought is that you'd get the mixture through faster, but it's on the wrong side so wouldn't be able to compress any air in the cylinder once the exhaust valve had closed. I think the boost would be minimal and you'd still have the parasitic drive using up power. Might be a loss rather than a gain.
Just my thoughts.
Pete
To compress any more air in the cylinder you would have to rethink all intake manifolds that work with a "vacuum exhaust system." Meaning, some type of NA intake system such as those Ram-Air manifolds on Dodges and Plymouths back in the mid 1960's to take advantage of the exhaust suction. No? Perhaps a gain of power then.
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Joe hit it on the head. "Normally aspirated" are the words that kill this idea.
You can word it and re-tinker it any way you want, it won't pass in unblown class.
If you say "why?" the gods of SCTA say "because I said so."
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Page 46 of the 2009 rulebook.
4.FF
Nope.
Matt
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Jonny, I got to hand it to you - I'll be thinking this one over for a couple of days.
The question is if you could really get the converted compressor/vacuum-extractor turning fast enough to completely evacuate the cylinder of any remaining exhaust, and thus completely fill the cylinder with a clean charge. A full, clean cylinder charge would be an advantage.
The problem I see is that you'd be trying to extract a gas that's still expanding as it leaves the exhaust port, and thus, as both RPM and heat increase, so does the need for the vacuum extractor to turn proportionally faster to draw higher vacuum than the approaching exhaust.
It might fatten up a torque curve at low RPM and make your cam sound less lumpy, but I suspect the advantage would fall off at high RPM's.
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I agree with Pete.
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I think you might have better luck driving it with a high speed electric motor than a belt due to the rpm's your talking about.
The verbiage on SCTA superchargers and turbochargers is somewhat limiting IMHO, and might cause issues.
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Jonny,
Since most exhaust gases go out under pressure, I don't know if the HP required to drive the turbo would offset the power gained if any. Would not be legal in NA classes.
Tom G.
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I think you might have better luck driving it with a high speed electric motor than a belt due to the rpm's your talking about.
Hmmm . . . more to ponder . . . Thinking out loud here
Interesting thought, but if Rex is right, you need 100,000 RPM.
1. Is there a 12 (or 24) volt electric motor that will turn 100,000 RPM with enough power to stay sufficiently ahead of the exhaust discharge to be of assistance in overcoming pumping loss, evacuating the cylinder during valve overlap and promote filling of the intake charge? I genuinely don't know.
2. If so, what kind of amperage would such a motor draw?
3. Driving the turbine directly, how would someone insulate such a motor from the exhaust? I suspect direct drive would take heat right off of the impeller straight to the armature and windings. A belt might act to insulate the motor.
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OK, the goal is to first "suck" out the spent gases, then to push back into the port. During the overlap phase, should the TurboSuck work, it will draw some of the intake charge out, reducing the density. Whereas a well designed exhaust header will pressurize it slightly. Or maybe not.
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I think there would be a much larger issue than just running an electric motor at 100,000 rpm. The issue is going to be regulating the RPM of the electric motor through the entire RPM range of the engine. You can't just make a huge vacuum at a static 100,000 RPMs at idle and at WOT and not expect VE to be effected adversely. Not to poo-poo the idea, but I think that the complexity of basically of a turbine powered, externally driven pump used to create a vacuum in the exhaust flow is way too complicated.
If you were wanting to create a vacuum in the exhaust that will pull in additional air through the intake, a simple designed veturi in the exhaust plumbing powered by an "afterburner" type setup would be a much more simplistic approach. It would have at least three benefits:
- It would not rob any additional power from the engine.
- It would be driven from fuel already carried on board
- It would look cool spouting flames out the exhaust on a run!!!
I would be surprised if the actual gain in power or flow would be worth the effort.
In the words of the great Dennis Miller: but that's just my opinion, I could be wrong.
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I got a better idea . . .
Rig the steering to turn the car directly into the wind, thus harnessing the headwind to supercharge the mixture. But, then again, it might not overcome the aero disadvantage. Could be hard to get a timing slip with all the changes of direction. That's it, use a roadster! This may take some more work.
Stan
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There was a car running many years back that used N2O to cool the turbo. The car ran on gas and the N2O never entered the motor. because there was N2O on board the car was required to run in the fuel class. I would assume that having the turbo on the car weather being used for forced induction or not the powers to be would put it in the blown class. Just a guess.
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There was a car running many years back that used N2O to cool the turbo. The car ran on gas and the N2O never entered the motor. because there was N2O on board the car was required to run in the fuel class. I would assume that having the turbo on the car weather being used for forced induction or not the powers to be would put it in the blown class. Just a guess.
Probably could have got away with C02.
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There was a car running many years back that used N2O to cool the turbo. The car ran on gas and the N2O never entered the motor. because there was N2O on board the car was required to run in the fuel class. I would assume that having the turbo on the car weather being used for forced induction or not the powers to be would put it in the blown class. Just a guess.
Dallas,
As I recall a few years ago the rule for supercharging was being abused. One or two entries put non functioning blowers on their vehicles to get into the supercharged class. Now to get into that class your supercharger must be functional and put out boost, or you will not be allowed to run in the supercharged class. For what that is worth that is what I remember. LOL
Tom G.
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I believe you're fight, Tom. I usually do. And I think they'd think the same about suck as they do blow. (Am I on the right forum?)
Stan
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I think you might have better luck driving it with a high speed electric motor than a belt due to the rpm's your talking about.
Hmmm . . . more to ponder . . . Thinking out loud here
Interesting thought, but if Rex is right, you need 100,000 RPM.
1. Is there a 12 (or 24) volt electric motor that will turn 100,000 RPM with enough power to stay sufficiently ahead of the exhaust discharge to be of assistance in overcoming pumping loss, evacuating the cylinder during valve overlap and promote filling of the intake charge? I genuinely don't know.
2. If so, what kind of amperage would such a motor draw?
3. Driving the turbine directly, how would someone insulate such a motor from the exhaust? I suspect direct drive would take heat right off of the impeller straight to the armature and windings. A belt might act to insulate the motor.
There are motors that will run that fast, but none that I have seen at 12-24V. You would probably have to run much higher voltages, but guess you could call the batteries ballast.
Amperage? I suppose it's possible to calculate from the the turbine how much power would be needed, but not certain how to start that.
Heat on the motor would be a real issue, but running a belt that fast is also.
Dunno, interesting nutty idea for sure though.
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A 12v starter motor can drive a centrifugal supercharger into boost for a few minutes with the correct gearing. I do not know an electric motor that can spin at 100K but this would imply a "direct drive" configuration (and this is not realistic, for that matter most of this discussion isnt!) and whose to say you would need 100K RPM, again why not oversize the unit and spin it at 50K with a 10 to 1 gearbox and a 1000 rpm motor.
For argument sake I would still say a mechanically driven geared centrifugal supercharger (such as a paxton, procharger ect) could be used....if they wouldnt melt!
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If you were wanting to create a vacuum in the exhaust that will pull in additional air through the intake, a simple designed veturi in the exhaust plumbing powered by an "afterburner" type setup would be a much more simplistic approach.
Okay, let's really get nutty. What about an inline turbine?
Forget the words, "Supercharger", "Turbocharger", "Blower", etc.
We'll call it an active exhaust system.
Question - Is there enough oxygen in a piston engine's exhaust to mix with fuel and drive a turbine? :roll:
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As far as I recall aux. driven blowers etc. are dis allowed. This came up a few years ago. Something to the effect what happens if the race engine blows and and the Aux. blower or turbo is still turning full speed. It's a safety feature. Run it by the rules committee before you spend the time, engineering and $$$$$
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Hey, Glen -
I suspect that this thread is more an exercise of "what if", and not so much, "let me go grab my wallet and I'll get started". :-D
And that's all good!
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Pretty sure you could not do it on a big inch blown engine. There is an awful lot of violence coming out the pipe at full boost.
An N/A motorcycle would be the likely candidate.
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Really don't understand this.
If there's no boost (defined as positive pressure before the intake valve, yes?), it's not boosted.
A non-functioning blower (read above) is not a blower.
End here, unless you're going to re-write the rules.
Advantages:
1. overlap can be anything you want.
2. CFM size for carb no longer limited to 1/2" Hg WOT
3. added vacuum BTDC initiates flow earlier (why wait for the piston?).
4. pumping gain ABDC on exhaust stroke (vacuum assists rising piston).
5. duty cycle = 100%: exhaust opens @ BDC.
6. controls bleed off vacuum from the turbine by solenoid valve when manifold conditions dictate.
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If you want some interesting reading on exhaust pressure:
Comparison of two Exhaust Manifold Pressure Estimation Methods
http://www.vehicular.isy.liu.se/Publications/Articles/CCSSE_01_PA.pdf (http://www.vehicular.isy.liu.se/Publications/Articles/CCSSE_01_PA.pdf)
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activeley scavenging the exhaust would require the pump to work harder to produce the same effect as pre-charging because of the smaller valves. Also, if exhaust were to drive the system, by the time you considered gear-box losses to overspin the compressor to work as a vacuum, you would probably not net very much gain do to the trapped heat and backpressure that would be created.
Someone mentioned an exhaust afterburner. That would be cool. Hope the "push" vehicle survives!