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| Turbocharger power input (consumption) |
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| firewalker:
Does anyone know what amount of power a car turbocharger need in order to spool and produce the needed pressure? Is there any first-hand rule to calculate it? E.g. a T25 turbocharger needs X amount of power input etc. I was looking at an electrically driven turbocharger and motor was about 7 kWatt at 48 volts. The equivalent motor driver was also at that range. Alexander. |
| joeqsmith:
--- Quote from: firewalker on March 25, 2020, 11:02:57 am ---Does anyone know what amount of power a car turbocharger need in order to spool and produce the needed pressure? Is there any first-hand rule to calculate it? E.g. a T25 turbocharger needs X amount of power input etc. I was looking at an electrically driven turbocharger and motor was about 7 kWatt at 48 volts. The equivalent motor driver was also at that range. Alexander. --- End quote --- There are a few turbocharger forums that would be more appropriate than one for electronics. I've seen some stupid videos on electric turbochargers based on leaf blowers and such. Some of these, they had their cars on some sort of roller dyno to attempt to measure the gains. It seems there was one using gas powered leaf blowers that made some small amount of boost. A general rule would be 1/3 goes into friction losses, 1/3 is available for work and 1/3 exits the exhaust in heat. For an engine, the amount of charge you want to pack in there will vary. Pump gasoline maybe they run 7PSI vs a methanol engine running at 60PSI. The volume of air required will be dependent on the engine as well. You can imagine if you were to pump up tires of a road bicycle to 120PSI, vs an off road at 30, which one will be more difficult to fill. But again, I did say that a 1/3 is available at the exhaust. If you know the flow and pressure, you could calculate the power ballpark the efficiency from the curves for your particular compressor. In your case, 7KW / 745 is roughly 10HP. I use small turbos like your T25 on my bike engines. Even if these were stock, they can output more than 100HP. That's a lot more than 7KW available to the turbocharger. |
| unknownparticle:
Think that an ICE is typically between 30-40% efficient. So for a given power rating there is upto 70% of the actual available power of combustion going out to cooling system, friction and exhaust. I think the typical rule of thumb is that as much power as the engine produces goes out of the exhaust. So that is alot of available power for a turbo to convert, more that 7KW in almost any automotive engine and then some! Electric turbos are just a joke, especially the early versions that used a PC fan!!!! The electrically assisted turbos that are now being developed, actually, they might even be in use now, are a different matter. Here, an electric motor is used to spool the turbo to minimise or even eliminate turbo lag, but the motor is not used to develop actual boost pressure. |
| firewalker:
If I understand correctly Audy uses two turbochargers. One electric and one on the exhaust manifold. Both produce boist. The electrical one in low rpm ti fux the lag issue. |
| joeqsmith:
Garrett is apparently planning to release one next year as well. The goal is not only to improve matching the turbo to the engine and reduce lag but to use the motor as a generator to help in recovery. That's a big difference from having a 7KW motor trying to create boost. Another thing we have tried was VGTs. Around this same time, I want to say New Departure Hyatt was working on a sealed turbo that required no external oil system. I've moved onto ceramic bearings but not to reduce the lag but rather hoping it is more forgiving with the oil system. I saw a more recent system that did not use oil as well. They still require water cooling but that was it. In my particular application, lag isn't an issue. The motor sits on a stutter box (rev limiter, low speed governor, 2-step...) with the throttle held full open. The turbo spools up under this condition and will create 7+ PSI of manifold pressure (boost). Once the clutch is released and the engine is no longer limited, you have all the boost you want. I want to say it's up at full pressures in well under a half second. If you like, I can show you plots of boost vs time from my own setup. |
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