Wastegates: dump to atmosphere or route back to DP?
12-26-2006, 11:41 AM
#22
Originally Posted by Snyper
Dont wastegates start to open before peak boost is reached?
The really good gates with a good controller don't. That is how you reach max boost the quickest. If the valve cracks up off the seat then you are bypassing exhaust energy that would otherwise be entering the turbine housing.
12-26-2006, 01:16 PM
#23
Originally Posted by DrTurbo
The really good gates with a good controller don't. That is how you reach max boost the quickest. If the valve cracks up off the seat then you are bypassing exhaust energy that would otherwise be entering the turbine housing.
12-27-2006, 11:27 PM
#24
I like the way you're thinking, but there is still a piece of the system to consider. Will a turbo spool faster with more backpressure on the tailpipe or less backpressure on the tailpipe? The one with less backpressure on the tailpipe will spool faster.
Dumping the wastegate back into downpipe will create backpressure when the wastegate is closed. While the wastegate is closed, the air passing over the merge point will create a vacuum in the wastegate tube. This leads to backpressure in the downpipe. More backpressure means slower spooling.
Will the difference be significant? I really don't know...
Dumping the wastegate back into downpipe will create backpressure when the wastegate is closed. While the wastegate is closed, the air passing over the merge point will create a vacuum in the wastegate tube. This leads to backpressure in the downpipe. More backpressure means slower spooling.
Will the difference be significant? I really don't know...
Originally Posted by Dragframe
Turbo spool happens before the wastegate even comes into play!!!! so how would its piping effect spool?
12-27-2006, 11:43 PM
#25
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Got ya..
Its an area of low pressure .. Pressure always moves from a higher to a lower point..
Good point
But like Dr.Turbo said... If you do have a good boost controller you would prolly have that problem..
SO that would leave the rest... Wastegate cracking open before peak boost..
Its an area of low pressure .. Pressure always moves from a higher to a lower point..
Good point
But like Dr.Turbo said... If you do have a good boost controller you would prolly have that problem..
SO that would leave the rest... Wastegate cracking open before peak boost..
12-28-2006, 12:42 AM
#26
4" should handle more than suggested above.
That said, a waste gate will generally function more precicely when vented to the atmosphere. It will also unleash a few ponies... dont integrate unless you must for noise reasons. It will certainly increase the evil turbo devil called backpressure.
Rememberthe wastegate valve starts opening quite early in the boost so it will reach a position to stabalize boost when boost reaches as desired maximum. A gate set at 10 psi will often start to open at 5 psi (wasting energy!) Thats a flaw in the whole design...we let off energy so readily. What ever happened to the VATN controlled turbos!
That said, a waste gate will generally function more precicely when vented to the atmosphere. It will also unleash a few ponies... dont integrate unless you must for noise reasons. It will certainly increase the evil turbo devil called backpressure.
Rememberthe wastegate valve starts opening quite early in the boost so it will reach a position to stabalize boost when boost reaches as desired maximum. A gate set at 10 psi will often start to open at 5 psi (wasting energy!) Thats a flaw in the whole design...we let off energy so readily. What ever happened to the VATN controlled turbos!
Last edited by Jammer; 12-28-2006 at 12:47 AM.
12-28-2006, 08:43 AM
#28
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FastKat,
You’re essentially restating what I said up in post #4 - improvements in the D/P will result in better spool. I was thinking more along the lines of bigger dia., less bends, etc...
As far as significant and measurable gains in spool and a reduction of back pressure [while the wastegate is closed] from removing the discharge tube itself, I think the smart money would be on ~zero. I just can't see any real difference on the kits/designs that are out there, but I haven't done a controlled experiment either.
It would make an interesting test though - maybe log 0 to full boost with 3 setups: wastegate merged, wastegate dumped with discharged tube still connected but capped at the wastegate mounting flange, and finally a wastegate dumped with the discharge tube removed from the DP.
You’re essentially restating what I said up in post #4 - improvements in the D/P will result in better spool. I was thinking more along the lines of bigger dia., less bends, etc...
As far as significant and measurable gains in spool and a reduction of back pressure [while the wastegate is closed] from removing the discharge tube itself, I think the smart money would be on ~zero. I just can't see any real difference on the kits/designs that are out there, but I haven't done a controlled experiment either.
It would make an interesting test though - maybe log 0 to full boost with 3 setups: wastegate merged, wastegate dumped with discharged tube still connected but capped at the wastegate mounting flange, and finally a wastegate dumped with the discharge tube removed from the DP.
Originally Posted by FastKat
I like the way you're thinking, but there is still a piece of the system to consider. Will a turbo spool faster with more backpressure on the tailpipe or less backpressure on the tailpipe? The one with less backpressure on the tailpipe will spool faster.
Dumping the wastegate back into downpipe will create backpressure when the wastegate is closed. While the wastegate is closed, the air passing over the merge point will create a vacuum in the wastegate tube. This leads to backpressure in the downpipe. More backpressure means slower spooling.
Will the difference be significant? I really don't know...
Dumping the wastegate back into downpipe will create backpressure when the wastegate is closed. While the wastegate is closed, the air passing over the merge point will create a vacuum in the wastegate tube. This leads to backpressure in the downpipe. More backpressure means slower spooling.
Will the difference be significant? I really don't know...
12-28-2006, 09:08 AM
#29
As far as improving the design of the wastegate, when the gate is open, less bends and less angle, etc, will give you better flow. That should help reduce backpressure when the gate is open, which will help your EGT's.
According to Corky Bell in his book “Maximum Boost,” it would be a good idea to dump the wastegate line back into the exhaust no less than 18 inches away from the turbine outlet. He says that moving the wastegate dump back 18 inches or more will help to distribute some of the turbulence. I think a lot of turbulence is created at the turbine outlet and also where the wastegate pipe reenters the exhaust system. Spacing those areas out is supposed to help.
According to Corky Bell in his book “Maximum Boost,” it would be a good idea to dump the wastegate line back into the exhaust no less than 18 inches away from the turbine outlet. He says that moving the wastegate dump back 18 inches or more will help to distribute some of the turbulence. I think a lot of turbulence is created at the turbine outlet and also where the wastegate pipe reenters the exhaust system. Spacing those areas out is supposed to help.
Originally Posted by Eddiep
FastKat,
You’re essentially restating what I said up in post #4 - improvements in the D/P will result in better spool. I was thinking more along the lines of bigger dia., less bends, etc...
As far as significant and measurable gains in spool and a reduction of back pressure [while the wastegate is closed] from removing the discharge tube itself, I think the smart money would be on ~zero. I just can't see any real difference on the kits/designs that are out there, but I haven't done a controlled experiment either.
It would make an interesting test though - maybe log 0 to full boost with 3 setups: wastegate merged, wastegate dumped with discharged tube still connected but capped at the wastegate mounting flange, and finally a wastegate dumped with the discharge tube removed from the DP.
You’re essentially restating what I said up in post #4 - improvements in the D/P will result in better spool. I was thinking more along the lines of bigger dia., less bends, etc...
As far as significant and measurable gains in spool and a reduction of back pressure [while the wastegate is closed] from removing the discharge tube itself, I think the smart money would be on ~zero. I just can't see any real difference on the kits/designs that are out there, but I haven't done a controlled experiment either.
It would make an interesting test though - maybe log 0 to full boost with 3 setups: wastegate merged, wastegate dumped with discharged tube still connected but capped at the wastegate mounting flange, and finally a wastegate dumped with the discharge tube removed from the DP.
12-28-2006, 11:25 AM
#31
His book discusses theory and application of theory. He has a little experience - "With over 25 years of experience in designing, building, and installing turbo systems, author Corky Bell..." He also worked as an engineer with Bell Helicopters for 12 years, participated in amateur auto racing for 16 years, and opened and ran his own auto an light aircraft engineering and fabrication businesses.
Also, did the turbo Indy cars dump to the atmosphere or route back into the exhaust system? Usually that's a good place to see what works best... you can bet they test them.
Also, did the turbo Indy cars dump to the atmosphere or route back into the exhaust system? Usually that's a good place to see what works best... you can bet they test them.
Originally Posted by Smearin
But his book is also based more on his opinions than real facts to boot..
12-28-2006, 12:20 PM
#33
FormerVendor
Unless I'm building a system with open downpipes I always re-route the wastegate plumbing. I think it sounds horrible vented to atmosphere on a street car with an exhaust system.
And as others have stated, it cannot effect spool time as the wastegate only comes into play as you have neared your target boost level. Theoretically, some power can be gained, but most have enough downpipe that the difference is usually zero. (unless maybe you're running dual 2in downpipes).
Also, I have experimented with re-routing the gate right after the turbine discharge then moving it 3ft downstream of turbine discharge and there was zero difference in horsepower.
And as others have stated, it cannot effect spool time as the wastegate only comes into play as you have neared your target boost level. Theoretically, some power can be gained, but most have enough downpipe that the difference is usually zero. (unless maybe you're running dual 2in downpipes).
Also, I have experimented with re-routing the gate right after the turbine discharge then moving it 3ft downstream of turbine discharge and there was zero difference in horsepower.
12-28-2006, 12:35 PM
#34
I think my arguement is that more backpressure is created in the exhaust system when the WG is routed into the downpipe rather than vented to the atmosphere. More backpressure = slower spool.
And about rerouting the gate... was there any change in the torque curve at all or are you just referring to the peak, after spool, where the wastegate would be open?
And about rerouting the gate... was there any change in the torque curve at all or are you just referring to the peak, after spool, where the wastegate would be open?
Originally Posted by INTMD8
And as others have stated, it cannot effect spool time as the wastegate only comes into play as you have neared your target boost level. Theoretically, some power can be gained, but most have enough downpipe that the difference is usually zero. (unless maybe you're running dual 2in downpipes).
Also, I have experimented with re-routing the gate right after the turbine discharge then moving it 3ft downstream of turbine discharge and there was zero difference in horsepower.
Also, I have experimented with re-routing the gate right after the turbine discharge then moving it 3ft downstream of turbine discharge and there was zero difference in horsepower.
12-28-2006, 12:38 PM
#35
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Originally Posted by NassyVette
Anyone have pics with the wg routed back to the dp? I wouldn't mind doing a test once my kit is done...but thats gunna be a long time from now.
). The wastgate was mounted on the driver's side of the crossover pipe. From there, it discharged back into the downpipe which runs over the driver's side k-member between the motor mount and the frame. The discharge side was very short, since the wastgate location on the crossover was only a few inches away from the downpipe.
12-28-2006, 12:56 PM
#36
FormerVendor
[QUOTE=FastKat]I think my arguement is that more backpressure is created in the exhaust system when the WG is routed into the downpipe rather than vented to the atmosphere. More backpressure = slower spool.
[QUOTE]
Well for the wastegate to contribute to backpressure in the downpipe it would have to be open and flowing exhaust, and it will only open after the system has nearly reached peak boost.
So basically spool is not effected as there is no wastegate flow until the turbos are allready spooled.
[QUOTE]
Well for the wastegate to contribute to backpressure in the downpipe it would have to be open and flowing exhaust, and it will only open after the system has nearly reached peak boost.
So basically spool is not effected as there is no wastegate flow until the turbos are allready spooled.
12-28-2006, 02:40 PM
#37
Air passing over a void in an otherwise smooth surface creates a vacuum on that void. Air passing over a closed wastegate dump in a downpipe creates a vacuum on that wastegate dump. That vacuum creates backpressure. More backpressure (while the wastegate is closed) = slower spool.
[QUOTE=INTMD8][QUOTE=FastKat]I think my arguement is that more backpressure is created in the exhaust system when the WG is routed into the downpipe rather than vented to the atmosphere. More backpressure = slower spool.
Well for the wastegate to contribute to backpressure in the downpipe it would have to be open and flowing exhaust, and it will only open after the system has nearly reached peak boost.
So basically spool is not effected as there is no wastegate flow until the turbos are allready spooled.
[QUOTE=INTMD8][QUOTE=FastKat]I think my arguement is that more backpressure is created in the exhaust system when the WG is routed into the downpipe rather than vented to the atmosphere. More backpressure = slower spool.
Well for the wastegate to contribute to backpressure in the downpipe it would have to be open and flowing exhaust, and it will only open after the system has nearly reached peak boost.
So basically spool is not effected as there is no wastegate flow until the turbos are allready spooled.
12-28-2006, 02:49 PM
#38
FormerVendor
Originally Posted by FastKat
Air passing over a void in an otherwise smooth surface creates a vacuum on that void. Air passing over a closed wastegate dump in a downpipe creates a vacuum on that wastegate dump. That vacuum creates backpressure. More backpressure (while the wastegate is closed) = slower spool.
12-28-2006, 06:18 PM
#39
Originally Posted by INTMD8
Well for the wastegate to contribute to backpressure in the downpipe it would have to be open and flowing exhaust, and it will only open after the system has nearly reached peak boost.
So basically spool is not effected as there is no wastegate flow until the turbos are allready spooled.
Originally Posted by FastKat
Air passing over a void in an otherwise smooth surface creates a vacuum on that void. Air passing over a closed wastegate dump in a downpipe creates a vacuum on that wastegate dump. That vacuum creates backpressure. More backpressure (while the wastegate is closed) = slower spool.
