So figure this, let’s say you have a turbo which is not perfect for your application, meaning that the boost you are running, the turbo is not at its maximum efficiency.
Is this a possibly that one will set a boost level on the first wastegate (on the manifold), to the maximum efficiency that turbo will produce (at the flow rate of your car).
And with a second wastegate, mounted on the intercooler piping, you set it to whatever boost level you want.
Interesting idea or what?:ylsuper
Controlling boost with a 2nd WG on intercooler pipe
-
Checkered-Member
- Posts: 1593
- Joined: Wed Sep 24, 2003 7:14 am
- Car: 1998 Nissan Altima (modded)
2003 Audi A6 2.7T (stock) - Contact:
-
C-Kwik
- Moderator
- Posts: 8070
- Joined: Thu Aug 01, 2002 9:28 pm
- Car: 2013 Chevy Volt, 1991 Honda CRX DX
If I am reading this correctly, you are speculating about using a wastegate to control boost to a point where the turbo is running most efficiently and then using a BOV or wastegate to bleed off excess pressure in the intake side? Just reiterating so that you know if I am understanding you correctly or not.
I don't think it will be a good idea in application. I do like that you are trying to think outside the box. But here's my take. The only time I see there being any potential benefit is if you are running a boost level below or t the left of the peak efficiency island. While you would need some way of getting the exhaust wastegate to stay closed to a higher pressure level than what it sees in the intake manifold, that aside, you could potentially run it in a higher efficiency area of the map. However, keep in mind to increase the flow and/or pressure in the turbo, you must use more exhaust energy. Secondly, by increasing boost at the turbo, you are ending up with a higher air temperature than you would at a lower boost, even if you do it under a higher efficiency island. The efficiency only reflects that it heats up the air only a certain amount more than the laws of physics dictates. As we know air heats up when we increase it's pressure. 100% efficiency would mean that you've not heated the air in the compression process anymore than it needs to. 75% efficiency would mean you heated it 25% more. So naturally, the higher boost level will be hotter. You may cool down the charge slightly when you release some of the pressure in the intake side, but even assuming you decrease pressure with 100% efficiency lose 25% efficency over all(assuming 75% compressor efficiency). Couple that with the additional energy you use to get the turbo to drive more pressure and air, and chances are you will be losing power. sometimes keeping things simpler is just more efficient.
In a circumstance where your car boosts over or to the right of the peak island, there's not much you can do about it. Adding any further boost pressure or flow would result in even lower efficiency.
Sizing the turbo properly would likely be cheaper, simpler and more effective than trying something like this.
I don't think it will be a good idea in application. I do like that you are trying to think outside the box. But here's my take. The only time I see there being any potential benefit is if you are running a boost level below or t the left of the peak efficiency island. While you would need some way of getting the exhaust wastegate to stay closed to a higher pressure level than what it sees in the intake manifold, that aside, you could potentially run it in a higher efficiency area of the map. However, keep in mind to increase the flow and/or pressure in the turbo, you must use more exhaust energy. Secondly, by increasing boost at the turbo, you are ending up with a higher air temperature than you would at a lower boost, even if you do it under a higher efficiency island. The efficiency only reflects that it heats up the air only a certain amount more than the laws of physics dictates. As we know air heats up when we increase it's pressure. 100% efficiency would mean that you've not heated the air in the compression process anymore than it needs to. 75% efficiency would mean you heated it 25% more. So naturally, the higher boost level will be hotter. You may cool down the charge slightly when you release some of the pressure in the intake side, but even assuming you decrease pressure with 100% efficiency lose 25% efficency over all(assuming 75% compressor efficiency). Couple that with the additional energy you use to get the turbo to drive more pressure and air, and chances are you will be losing power. sometimes keeping things simpler is just more efficient.
In a circumstance where your car boosts over or to the right of the peak island, there's not much you can do about it. Adding any further boost pressure or flow would result in even lower efficiency.
Sizing the turbo properly would likely be cheaper, simpler and more effective than trying something like this.
-
Checkered-Member
- Posts: 1593
- Joined: Wed Sep 24, 2003 7:14 am
- Car: 1998 Nissan Altima (modded)
2003 Audi A6 2.7T (stock) - Contact:
Yes that is exactly rightC-Kwik wrote:If I am reading this correctly, you are speculating about using a wastegate to control boost to a point where the turbo is running most efficiently and then using a BOV or wastegate to bleed off excess pressure in the intake side? Just reiterating so that you know if I am understanding you correctly or not.
I never though it would be practical, the first most important point, is that if a certain psi is being produced by the turbo it also means that it is producing back pressure, but since some of the air is being bleed off to the atmosphere, less air is entering the combustion camber to over come this back pressure, lowing power like crazy, I guess that is why, when you have even the smallest air leak, you lose huge amounts of power.
the problems I see are that first, the turbo would be spinning but the engine not seeing the boost... its wasted power. The turbo still poses a restriction in the exhaust but the engine doesn't reap the reward of the boost.secondly, if you have a bov, thats a pretty small little valve, and it can make your boost gauge go from 20 psi to 0 just by opening. could a wastegate open just enough to regulate boost on the cold side??
-
Checkered-Member
- Posts: 1593
- Joined: Wed Sep 24, 2003 7:14 am
- Car: 1998 Nissan Altima (modded)
2003 Audi A6 2.7T (stock) - Contact: