Couple of basic turbo questions..
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Joined: Apr 2008
Posts: 1,616
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From: Fort Worth Texas
Couple of basic turbo questions.. I am looking into a building a turbo for another build,,
I have a few questions,
1. What exactly is a blow off valve,, from my understanding it basically a pressure relief valve that opens and dumps excess pressure if the turbo starts spinning too fast and building too much pressure? Is the blow off valve another term for a wastegate?
2. Where does the wastegate go,, I know the turbine is spun up from the velocity of the exhaust gases coming out of the manifold/header and on the other side of the turbo the impeller supplies a pressurized air charge that has heat in it, If you push that charge into an intercooler,,, Does the wastegate go before or after an intercooler?
3. If you ran a twin turbo setup,, would you need a blowoff valve for each turbo? Or a blowoff and wastegate for each turbo?
4.I read that smaller turbos build up boost faster, but bigger turbos build higher boost but take time to spool up, So is it common to run two different size turbos?
Thanks for any experienced help on this, I am in the process looking before I leap..
I have a few questions,
1. What exactly is a blow off valve,, from my understanding it basically a pressure relief valve that opens and dumps excess pressure if the turbo starts spinning too fast and building too much pressure? Is the blow off valve another term for a wastegate?
2. Where does the wastegate go,, I know the turbine is spun up from the velocity of the exhaust gases coming out of the manifold/header and on the other side of the turbo the impeller supplies a pressurized air charge that has heat in it, If you push that charge into an intercooler,,, Does the wastegate go before or after an intercooler?
3. If you ran a twin turbo setup,, would you need a blowoff valve for each turbo? Or a blowoff and wastegate for each turbo?
4.I read that smaller turbos build up boost faster, but bigger turbos build higher boost but take time to spool up, So is it common to run two different size turbos?
Thanks for any experienced help on this, I am in the process looking before I leap..
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Joined: Oct 2006
Posts: 1,194
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From: IL
I am looking into a building a turbo for another build,,
I have a few questions,
1. What exactly is a blow off valve,, from my understanding it basically a pressure relief valve that opens and dumps excess pressure if the turbo starts spinning too fast and building too much pressure? Is the blow off valve another term for a wastegate?
A blow off valve relieves the pressure in the piping between the turbo and the throttle body. When the throttle body closes, the pressure that is left in the pipe needs to go somewhere otherwise it will fight the already spinning turbo and can cause damage. This is completely different than a wastegate which is used in the exhaust to regulate how much exhaust gasses go to the turbo. When the desired amount of boost is reached the wastegate opens to redirect the exhaust gasses away from the turbo so that it doesn't keep spinning faster and faster creating more boost, and will maintain the wheel speed/boost level.
2. Where does the wastegate go,, I know the turbine is spun up from the velocity of the exhaust gases coming out of the manifold/header and on the other side of the turbo the impeller supplies a pressurized air charge that has heat in it, If you push that charge into an intercooler,,, Does the wastegate go before or after an intercooler?
The wastegate goes in the exhaust between the engine and the turbo. Try to think of it like this. The wastegate is a bypass valve, and the blow off valve is a relief valve.
3. If you ran a twin turbo setup,, would you need a blowoff valve for each turbo? Or a blowoff and wastegate for each turbo?
If you run two turbos, you would need two wastegates (to regulate the exhaust gasses, and in turn the boost level, from each turbo). You would likely not need two blow off valves.
4.I read that smaller turbos build up boost faster, but bigger turbos build higher boost but take time to spool up, So is it common to run two different size turbos?
That is somewhat basic, but more or less true. It is not very common to see two different size turbos. Most common would be to use two moderately sized turbos (on a V8 application) that will give you the best of both worlds with very little trade off. They will spool decently quick (depending on a lot of factors), and will still get you the large boost/air flow of a single bigger unit. Again there is more to it than that, but that's the basics.
Thanks for any experienced help on this, I am in the process looking before I leap..
I have a few questions,
1. What exactly is a blow off valve,, from my understanding it basically a pressure relief valve that opens and dumps excess pressure if the turbo starts spinning too fast and building too much pressure? Is the blow off valve another term for a wastegate?
A blow off valve relieves the pressure in the piping between the turbo and the throttle body. When the throttle body closes, the pressure that is left in the pipe needs to go somewhere otherwise it will fight the already spinning turbo and can cause damage. This is completely different than a wastegate which is used in the exhaust to regulate how much exhaust gasses go to the turbo. When the desired amount of boost is reached the wastegate opens to redirect the exhaust gasses away from the turbo so that it doesn't keep spinning faster and faster creating more boost, and will maintain the wheel speed/boost level.
2. Where does the wastegate go,, I know the turbine is spun up from the velocity of the exhaust gases coming out of the manifold/header and on the other side of the turbo the impeller supplies a pressurized air charge that has heat in it, If you push that charge into an intercooler,,, Does the wastegate go before or after an intercooler?
The wastegate goes in the exhaust between the engine and the turbo. Try to think of it like this. The wastegate is a bypass valve, and the blow off valve is a relief valve.
3. If you ran a twin turbo setup,, would you need a blowoff valve for each turbo? Or a blowoff and wastegate for each turbo?
If you run two turbos, you would need two wastegates (to regulate the exhaust gasses, and in turn the boost level, from each turbo). You would likely not need two blow off valves.
4.I read that smaller turbos build up boost faster, but bigger turbos build higher boost but take time to spool up, So is it common to run two different size turbos?
That is somewhat basic, but more or less true. It is not very common to see two different size turbos. Most common would be to use two moderately sized turbos (on a V8 application) that will give you the best of both worlds with very little trade off. They will spool decently quick (depending on a lot of factors), and will still get you the large boost/air flow of a single bigger unit. Again there is more to it than that, but that's the basics.
Thanks for any experienced help on this, I am in the process looking before I leap..
Sean
