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For a while now I've been thinking supercharging and turbocharging. Turbo's are good for power but theres lag and no power in low rpms. Superchargers are good for throttle responce and good power everywere (fixed displacement), but being driven off the pully system, they suck power from the engine where
the turbos power is basicly free. I cant decide which one I want.
What about combining a supercharger and and a turbocharger? Using a supercharger driven off the pullys and use a turbo, but modify the turbo:
Remove the intake turbine part and attach gears (turbos spin very fast) and a pully to it. Set up the pully so it can freewheel one direction but not the other so the turbo can only help the engine not drag it down. Wrap a belt around it and have the best of both worlds.
I kind of wonder how the turbo would like being limited on how fast it can spin though... Maybe setup a blow off valve type wastegate to release some exhaust if it creates too much pressure?
I know theres the typical twincharge setup, but maybe this would be better because it could help drive your whole pully system - AC, Power steering , alternator, all being drivin off otherwise waisted power.
Baked
http://www.popsci.c...004eecbccdrcrd.html
VW jumped on this a while ago, unfortunately it is only availabe in Europe. [Twist, Dec 22 2006]
Scania Turbocompound system
http://www.scania.c...logy/turbocompound/
This uses a second exhaust turbine geared to the crank through a torque converter, downstream of the turbo [Ned_Ludd, Aug 22 2007]
Turbocompound described
http://en.wikipedia...rbo-compound_engine
[Ned_Ludd, Aug 22 2007]
Wright R-3350 cutaway photo
http://www.enginehi.../3350with%20prt.JPG
One of the three blowdown turbines can be seen at the bottom left [Ned_Ludd, Aug 22 2007]
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So thats a faster spinning geared supercharger then. And the turbo's power isn't free, it is taking power from the engine. If it isn't we could solve the worlds power problems by running the worlds biggest turbo off a moped engine and attaching zillions of generators to it. |
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Ok, I guess I didn't make it clear - I meant wrap a belt around ALL of it, including the crankshaft pully. the only time the turbo would do anything is when it is spooled up - and then it would help the crankshaft drive the accessories. |
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The "typical twincharge" method is having a turbo, a intercooler, then the supercharger, then another intercooler then the intake. That way the when the turbo spools up it pushes the supercharger, or bypasses it letting the supercharger freewheel, taking the load off the pully system and supplying additional boost. |
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My way would just be a supercharger, an intercooler and the intake. The turbo would directly power the pully system, because the supercharger can supply the amount of boost I want. I just want to use the turbo to free the power that the pully system + accesories + supercharger is sucking from the engine. |
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Isn't this already halfbaked in the supercharged Turbocharger (above)? |
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The typical twincharge set/up has been used for 30/40 years on the General motors Detroit 2 cycle diesel eng quite succesfully.
Typicaly it was two/stage--Turbo feeding a rootes supercharger and aftercooled. nothing new guys; |
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The typical twincharge set/up has been used for 30/40 years on the General motors Detroit 2 cycle diesel eng quite succesfully.
Typicaly it was two/stage--Turbo feeding a rootes supercharger and aftercooled.
nothing new guys;blackie oct 12 03 |
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You guys are missing the point Ignore the supercharger or twincharge part. I know twincharging is nothing new, It was only in there to explain why I would use this turbo setup. |
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The Idea is hooking up a turbo to the pully system!
What do you think about that? |
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there is something called compound supercharging. Turbo Magazine built a Toyota MR2 with this setup. A intercooled turbo system is plumbed into a supercharger; the supercharger is used as a intake manifold if you will. the exaust energy created from the boost from the supercharger and the intake energy from the supercharger helps a turbo spool more quickly. no switches or anything to switch between the sc or t. It is as if you are using a supercharger with great all-around powerband and efficiency |
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I don't think most of you are getting the idea. The turbo isn't compressing any air in this system... heck it doesn't even have a compressor housing. Imagine a centrafugal supercharger, but with the exhaust impellar half of the turbo instead of the compressor half (IE take a turbo, throw out the compressor and attach a pulley with a one way bearing in its place). |
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The only addition I'd have to this idea is that you'd need to have a wastegate on the turbine that was open based on some electronics that read the exhaust pressure and engine rpm. You'll get to a point when the turbo spools up and the rpm of the turbo pulley and SC/crank pulley are equal (the oneway bearing isn't slipping anymore). The belt will try to keep them all turning together at the same rpm. If the wastegate is left closed and the exhaust backpressure to climb the engine will either lose power due to the exhaust back-pressure (and eventually stall) or the belt would slip, heat up, and break prematurely. Luckily the electronics for this already exist as a programmable electronic boost controller... but instead of opening and closing the wastegate to controlling intake pressure they'd be controlling exhaust back pressure. |
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I think its a great idea! |
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If I understand you, you're trying to recapture energy the engine is "losing" pumping air, and directly input that energy into the drivetrain. I don't think anyone here belives that the power you will lose by increasing the backpressure will be greater than the power you capture with the exhuast turbine. Maybe it would under certain conditions, such as decelleration, but you don't need more power then anyway. |
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Hey Guys check your history. WW II aircraft. This idea is called turbo compounding. It worked great but with the development of the jet engine, the idea was no longer needed. |
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Turbo compunding is great in theory, but very hard to pull off correctly in the numbers game. I've looked into this for quite some time and found a guy at knight superchargers that said he would be able to do it on my twinturbo Mitsu. However in talking with him and others, they suggested that for the money, and headaches I should just upgrade my turbos (and all that goes along with it). Though I would have lag, properly ported/clipped systems, can produce huge HP gains for the price. Also, you are probably better off with a nos boost at 25hp just to get off the line then use the turbos through the power curve, then reintroduce the nos on the top end. Another thing was mentioned to me. I could use smaller turbos in series with the larger turbo, assuming I could find enough room under the hood for the piping. Id also need to fabricate a nice way to keep everything cool. But buy using a small turbo in series with a large turbo, the small turbo provides low end boost while the large one provides high end boost, cutting lag drastically. I always wanted a triple charged car, but it was more the idea of having it rather than the practicality. In my opinion, and those expressed to me, it can be done to a factory turbocharged car for between 8-15k, but your better off sticking with one type or the other for the money. |
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Like many others have said, it is FALSE to say that turbo's take "wasted" power from the exaust and use no power of there own.. If this was true than your idea would be a great one. The reason that a normal turbo "super charges" the engine rather than having a belt that adds power to the crank on the enging are basic laws of physics. The same reason the perpetual motion doesn't work (on earth). As long as you have resistance (friction) of any kind, there will be a loss and not a gain.
The reason for this is bacause of exaust back pressure. Try taking an 800bhp racing enging and plum it through a stock honda exaust. It would probaby blow the honda exause to shreds due to the back pressure, but before it blew up you would relize huge power loss due to the restriction. This is why the tin can (fart) exaust systems on the rice rockets.
Turbos get their power by robbing it from the exaust system thus causing back pressure.
This is still efficient and only screw, centrifical, and scroll super chargers can match a turbo in efficenct. They are also much more expensive than a turbo. |
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The only way this would actually contribute to engine power would be to harness the exhaust power after it has left the exhaust pipe. Then you wouldn't get anything usable at all. Maybe 20W if that much. Any use of the exhaust gases within the exhaust system would give you a net loss of power because harnessing it increases the back pressure. |
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geoffrie, I think I know what you're saying. Effectively, you want to replace the compressor section of the turbo with a positive displacement-type supercharger, such as the Roots or twin-screw, via a belt system? |
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I too thought of an idea like this, however there will be some drawbacks that will probably give it no advantages over the typical turboed/supercharged/twincharged setup. |
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Say you use the twin-screw setup because of its efficiency, you may as well go with the twincharged setup because you're going to have to buy half a turbo and the twin-screw anyway. Assuming you did go ahead with your idea, you would definitely need to gear down the supercharger, as turbos typically spin at 100,000+ rpm, while twin-screw/roots max out at ~12,000rpm. However, you're still going to have lag because you're using the exhaust gases to spin up the supercharger. Unless, you could also drive the pully system from the engine at low rpms, then using a magnetic clutch (like an A/C system), disconnect it at the higher revs and use the exhaust gases to drive the supercharger. |
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Still, this is very similar to a twincharged system, and I also think it would be very hard to connect a belt up to the turbo. |
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Anyway, me head hurts now :) |
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The idea here is to use a positive displacement supercharger at the intake, and an exhaust-driven turbine to add power back into the drive train via a belt-and-pulley arrangement in place of the original centrifugal compressor. |
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WWII aircraft had this fully baked. The P-38 Lightning is one notable aircraft that used this method, and it was so successful that it was declared top-secret and photos of the Lightning from any angle that showed the turbine exhaust were prohibited. Although the system was geared, not pulley-driven, the functional principle was the same. The B-17 engines also had a similar system fitted, as did several other radial engines. It was one of the mission-critical systems that allowed the B-17 and P-38 to extend their range so far. |
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Good idea, but sorry, [marked–for–deletion] Baked. |
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I had to get one last word in, since I was going to post this idea myself. |
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The key factor here that most people seem to be missing is the *one-way pulley* (basically just a racthet) driving the turbo. |
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At low speeds, when the pully is spinning faster than the turbo, it acts like a centrifugal supercharger. When the turbo speeds up faster than the pulley though, the ratchet-type mechanism disengages and the turbo spins like a normal turbo, driven by the exhaust. |
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It's really pretty simple. Just extend a small shaft off the end of an otherwise conventional turbocharger, slap some sort of one-way hub on it, and belt/gear it to the crankshaft. |
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[freefall] that something exists or is "baked" is NOT grounds for deletion. |
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For those who know aviation well (and you know who you are), this may be "baked" but I don't consider it to be widely-known-to-exist and, so, I am letting the idea stand. |
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This has been churned back up by [Twist]'s link, above. |
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I feel the need to explain something here, possibly in neon letters. The idea, and attached annotations, say that the exhaust gases would drive a turbine, which would assist the engine in doing its job. |
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The supercharger would charge the cylinders. |
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Note: Turbocharger puts power into the transmission; it does _not_ pump air into the cylinders. |
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For the benefit of the next auto geek who wants to prove his auto uberness, yes, twincharging exists. Great. You knew. Now go back and read the idea again. He's not proposing a twincharger. |
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This is baked, but not as an aftermarket accessory for supercharged road vehicles, which is what I'd like to see. [+], therefore. |
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Yes, there is useful power to be got from an exhaust power recovery or blowdown turbine, possibly more than a supercharger drive belt would be able to handle. This is because the effect of supercharging is to create an effective compression ratio appreciably higher than the expansion ratio and, therefore, an increase in surplus energy available in the exhaust. |
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The need moreover for rotational speed reduction in the order of 20:1 suggests a gear drive rather than a belt (underslung worm drive on the crank nose?) |
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The Formula is: E + S= $x and E + S + T = $x2 |
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E = normally aspirated engine
S = Supercharger
T = Turbo
$ = Money |
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In other words if you have enough money anything is possible... |
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