Subaru Ascent Forum banner
1 - 9 of 9 Posts

·
Registered
Joined
·
266 Posts
I think it makes sense to get rid of turbo lag. It would also make sense to simply fill up a canister of compressed air when you have excess air in the turbo, then release it in the couple of seconds it takes the turbo to spool, just to fill that gap. By the time your canister is empty, your turbo will be at full speed.

An electric motor is a bit more wasteful, since you are not recovering the kinetic energy from the exhaust gas. In the end the power to run that electric turbo will come from the alternator, so it becomes another load on the engine. But if you want the car to be responsive and don't care much about efficiency... it seems like a good idea to go electric.
 

·
Read Only
Joined
·
0 Posts
I think it makes sense to get rid of turbo lag. It would also make sense to simply fill up a canister of compressed air when you have excess air in the turbo, then release it in the couple of seconds it takes the turbo to spool, just to fill that gap. By the time your canister is empty, your turbo will be at full speed.

An electric motor is a bit more wasteful, since you are not recovering the kinetic energy from the exhaust gas. In the end the power to run that electric turbo will come from the alternator, so it becomes another load on the engine. But if you want the car to be responsive and don't care much about efficiency... it seems like a good idea to go electric.
...and the energy needed to compress stored air into a canister is any less wasteful than an electric turbo? You're going to have to show your work there, please...I don't see it

I think it's been proven in the racing industry that powertrain efficiency is best achieved with electric addons, as mechanical losses in accessories driven by motors are preferred to belt driven accessories. If you're not losing x% to this fan, and y% to this pump, there's all the more power to put to the ground.
 

·
Registered
Joined
·
266 Posts
...and the energy needed to compress stored air into a canister is any less wasteful than an electric turbo? You're going to have to show your work there, please...I don't see it
I meant when you are driving, after you accelerate to a certain speed you start driving at constant speed, your rpms are relatively high and your turbo is spooled. The car opens the wastegate and releases the excess pressure to the exhaust. My point was you could simply store this excess into a canister, you wouldn't use any more energy than you are already.
I agree with your assessment that electrical efficiency is higher in general, but you need energy to run the electric motor vs. just recovering energy from exhaust fumes that's being wasted anyway...
In any case, reading deeper into the article, they also recover this energy by using the electric motor as a dynamo, effectively recovering energy from the exhaust. So yeah, these guys thought of everything...
 

·
Read Only
Joined
·
0 Posts
The car opens the wastegate and releases the excess pressure to the exhaust. My point was you could simply store this excess into a canister, you wouldn't use any more energy than you are already.
you could store it into a cannister, but now you've added pressure vessel weight to the chassis, the required plumbing to control and pipe the pressure back into the front side of the turbo (remember you can't just dump the pressure back into the turbo from the back, the vanes are not set up for that...and you're literally introducing backpressure into a system that can't run on back-pressure), the added controlling devices etc. You're also adding friction loss from piping, heat considerations due to air being compressed & cooled, moisture, etc...

It's an interesting concept, but I don't think the return on investment, in terms of performance, would be worth the effort. ;)
 

·
Registered
Joined
·
1,162 Posts
I guess excess pressure could be stored in a canister, but it'd have to be a big one because the pressure is not that great and the required volume of flow is great. I'm thinking something half the side of the interior of the Ascent. That's just a rough guess.
 

·
Registered
Joined
·
266 Posts
I guess excess pressure could be stored in a canister, but it'd have to be a big one because the pressure is not that great and the required volume of flow is great. I'm thinking something half the side of the interior of the Ascent. That's just a rough guess.
Mine was just a wild speculation, but I don't think it's as far fetched as you might think...
Not exactly the same but on the same line of thought.
 

·
Registered
Joined
·
1,162 Posts
^^^They're using a separate electric compressor so they can store enough PV (pressure times volume) in a reasonable size can. I'd think using the electricity to directly spin up the turbo would be simpler more efficient solution.
 
1 - 9 of 9 Posts
Top