Note: If your not in the mood to read a scenario-type idea, just skip the first paragraph.
So, you just bought a brand new turbocharged car with direct injection and want to "trick it out" a little. So what do you do? You could get a bigger turbo that provides more boost, but that would sacrifice any low-end torque you once had plus create a higher boost threshold. You can't upgrade the intake, since it's already pre-tuned to provide the best flow for the turbo. You can't change the camshafts since they already have top-of-the-line continuosly variable valve timing. So the only thing that's left is to modify the exhaust. The most obvious solution would be bigger exhaust tubing since the turbochargers provide enough backpressure at any rpm, but you notice a problem. The catalytic converters are also providing backpressure, making a modified exhaust system pointless while also converting usable hydrocarbons into many things (including water, which will be quite corrosive to the turbocharger assembly with time). But wait, why not just remove the converters, the engine has direct injection right? Surely that would make it lean enough to pass any emissions test, just like the european version of the Audi A3? Wrong. Direct injection or not, high performance cars (especially super/turbocharged ones) have rich mixtures when the throttle is fully or mostly open. So what can you do?
In low throttle and lean mixture conditions, there would be a tube that bypasses the turbo and goes into a seperate exhaust pipe. In the main system, there is a tube from the bumper of the car (with a butterfly valve in it) that connects with the exhaust headers and tubing. In that tube, there would be a compressor (like in a gas turbine) to take the air from the front of the tube and compress it into the exhaust flow.
When wide open (or close to wide open) throttle occurs, the butterfly valve opens for the air compressor and the valve for the tube that bypasses the turbo closes. The electric motor (hooked up by a CVT) immediately spools up the compressor to prevent the exhaust gases from flowing out the front of the car. Spark plugs ignite the hydrocarbons and the extra compressed air helps them burn. The exhaust flow plus the added bonus of combusting otherwise wasted hydrocarbons would help the turbo to make more boost than it could otherwise.
Then, when you lift your foot up, the exhaust is immediately re-routed into the bypass tube. The Butterfly valve for the exhaust air inlet closes. The electric motor that is used to spool up the compressor is now acting like a generator (which it can do since it is hooked up via CVT) to slow down the compressor and harness its energy (which will be used to recharge the battery and, in turn, be used to spool up the motor once again). The blow off valve would be hooked up to a sensor which (unlike all current blow off valves) would automatically lean the mixture. The air from the blow off valve is then fed into the compressor to spin the generator a little more and mainly slow down the turbo signifiganty (since in this way it would indirectly be hooked up to the generator). This way when you turn the car off, everything slows down relatively quickly (which is good since when the car is off no oil is getting to the turbocharger).-- acurafan07, Feb 19 2007 catalytic converters* http://www.answers....catalytic-converter [quantum_flux, Feb 19 2007] Ram Jet Fuel Saver http://www.ram-jet.net/ [J Vander, Jun 17 2007] For several years, Mazda rotary engines used compressors to force air into the exhaust manifold to burn up excess hydrocarbons, but I think that was before they used turbos. Most rally cars nowdays have "anti-lag" systems that dump fuel into the exhaust in between gear shifts in order to keep the turbo spooled up.
Your idea certainly sounds possible, but I'm not sure if it would be worth the trouble. Burning the fuel in the manifold, while it would make the turbo go faster, would probably create backpressure in the engine, since the turbo is essentially driven by backpressure. So I'm not gonna vote until I see what other people have to say.-- discontinuuity, Feb 19 2007 So... Basically, it's an ignition system in the exhaust manifold to reburn the exhaust, boosted by an electric supercharger?
I think the power drain from the supercharger would be much too great. Additionally, slowing the turbocharger may be handy when you turn the car off, but is quite bad for performance when actually driving. Besides, modern turbos no longer suffer from seizing due to lack of oil on shutdown. How do you think Subaru/Audi/Saab get away with not using turbo timers?
Also, the picture you linked doesn't really explain anything. It's just some turbines.-- 5th Earth, Feb 19 2007 The electric motor is only to spool it up (which would actually help prevent lag), afterwards the combustion would be enough to keep the compressor running like in every other gas turbine. The part about slowing down the turbo is optional.-- acurafan07, Feb 19 2007 *sigh*
Classic Acurafan.-- jhomrighaus, Feb 19 2007 Uh... Is that my cue to delete the idea? Believe it or not, I actually did do research on gas turbines and turbochargers before posting this.-- acurafan07, Feb 19 2007 I would never delete any of your ideas if it were me, its just you are still trying to fix things that one might argue don't need to be fixed. Now if this were powered by a giant clock spring that was wound during braking, or if the turbine was fart gas powered by the occupants(a farbine?), that would be a different story.
The main issue here is that you would burn more fuel keeping the turbo spooled than you would save by the power gained.(did that make sense?)
It is a little different that your usual fair but still to close to the safety zone to be a real wow.-- jhomrighaus, Feb 19 2007 Criticisms of catalytic converters from www.answers.com (see above link)*
Catalytic converters have two adverse environmental impacts in use (ignoring the pollution caused in their manufacture, which would not exist were they not mandated):
1) The requirement for the engine to run at the stoichiometric point means fuel economy is not as good as that of a "lean burn" engine running at a mixture of 20:1 or weaker. This increases the rate at which fossil fuel resources are consumed and the carbon dioxide emissions of the vehicle.
2) Catalytic converters are estimated to account for 50% of total nitrous oxide (dinitrogen oxide, 'laughing gas') emissions to atmosphere. While N2O emissions in these concentrations are not harmful to human health, it is a potent greenhouse gas, accounting for around 7% of the overall greenhouse effect despite its small concentration in the atmosphere.
Therefore one conclusion is that catalysts have reduced toxic emissions and the incidence of smog at the expense of increased global warming.-- quantum_flux, Feb 19 2007 Well I'll be damned, I remember mentioning in one of my previous ideas that catalytic converters are a cause of "global warming", and no one seemed to believe me. As to the trade off, this idea is to try and burn off the excess toxic emissions that would otherwise flow out the tailpipe (or into the converter). I think a better setup for this idea would be to have the exhaust gases first run the turbine, then exhaust them into the compressed air and ignite them, and then finally have the turbine after all of that to harness the pressure of the exhaust + the added combustion of the hydrocarbons. I'd also make everything out of titanium (yeah it would cost like $5,000 but after all this is the half bakery).-- acurafan07, Feb 19 2007 So, your saying to reroute exhaust gases back through the engine to catch unburned fuel? I believe it's already in action. Check out the link for the Ram Jet.
Also, the Pantone MFP does this.-- J Vander, Jun 17 2007 random, halfbakery