one WG on divided manifold ?
Feb 2, 2011, 08:26 PM
#17
Dual gates would be better. Duals will give you better turbo spooup. As you can set the initial gate to open later since there will be a second gate to back it up.
Duh. For example .. Let's say that your target boost level is 27#: With two staged gates you could set the first gate really tight to 25# and the second gate to open at 27#. Otherwise if you only had a single gate then you would have to calibrate it looser and your turbo spoolup would suffer.
Of course, you probably have a different point of view. But that is OK. Needless to say, with dual gates you can run the 1st gate tighter since the 2nd gate backs it up. So, you will achieve faster turbo spoolup.
Duh. For example .. Let's say that your target boost level is 27#: With two staged gates you could set the first gate really tight to 25# and the second gate to open at 27#. Otherwise if you only had a single gate then you would have to calibrate it looser and your turbo spoolup would suffer.
Of course, you probably have a different point of view. But that is OK. Needless to say, with dual gates you can run the 1st gate tighter since the 2nd gate backs it up. So, you will achieve faster turbo spoolup.
Another good reason for single wastegate is if you have a wastegate fault.
If one doesn't open, you're applying massive pressure to two cylinders (1 scroll).
If it doesn't open with a single wastegate (or leaks etc) then you'll know about it right away.
And if it's a racecar, then weight and simplicity is very important.
I disagree with it spooling faster with dual gates. I'm sure Ted B can comment on his setup. You will prob lose a little power when the gate opens as the scrolls can bleed over into each other, but it will depend on how long the wastegate pipe is etc...
Feb 2, 2011, 08:38 PM
#18
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With a single 44mm gate then you would have to set cracking pressure at a lower PSI to be able to handle the total volume of exhaust gas flow. Whereas, if you had a dual 44mm WG setup then you could set cracking pressure on the first gate higher since the second gate would totally bleed off what the first gate couldn't handle. I don't know what you can't understand.
Feb 2, 2011, 09:10 PM
#20
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RSMike: I am probably equating apples to oranges. I used to run a dual gated setup on my old Buick GN. The integral gate on my Garrett TE50 turbo couldn't control boost by itself. So, we would incorporate an additional turbonetics WG on the crossover pipe of the V6 engine design.
This setup would allow us to run a much tighter spring pressure on the integral gate as the volume of the second gate would easily handle the excess volume of exhaust gas flow.
Take care. And don't bring Tedb into the fray as he will surely whump my poor ****.
This setup would allow us to run a much tighter spring pressure on the integral gate as the volume of the second gate would easily handle the excess volume of exhaust gas flow.
Take care. And don't bring Tedb into the fray as he will surely whump my poor ****.
Feb 2, 2011, 09:37 PM
#21
Dual 44's will flow as much as a single 62mm wastegate. Either way though a single 44 is known to flow enough gas for a lot of power. I would just use a good ebc with a single gate and not worry about it. A good ebc can keep the gate closed as long as possible without causin spikes.
Feb 2, 2011, 09:46 PM
#22
Dual 44's will flow as much as a single 62mm wastegate. Either way though a single 44 is known to flow enough gas for a lot of power. I would just use a good ebc with a single gate and not worry about it. A good ebc can keep the gate closed as long as possible without causin spikes.
The more boost, the less wastegate you need.
The bigger the turbo the less wastegate you need.
(all else being equal)
Divided and or twin scroll turbo setups do not need two waste-gates but they do need two separate exhaust paths between the port and the turbo, if they don't then you lose some of the added efficiency of the split pulses.
I like evodan run two tial 44-'s with about 22 lbs of pressure on the gate.
Scorke
Feb 3, 2011, 03:37 AM
#24
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if you run different opening pressure for each runner what happens to your backpressure in the manifold and the tuning to compensate?
Another good reason for single wastegate is if you have a wastegate fault.
If one doesn't open, you're applying massive pressure to two cylinders (1 scroll).
If it doesn't open with a single wastegate (or leaks etc) then you'll know about it right away.
And if it's a racecar, then weight and simplicity is very important.
I disagree with it spooling faster with dual gates. I'm sure Ted B can comment on his setup. You will prob lose a little power when the gate opens as the scrolls can bleed over into each other, but it will depend on how long the wastegate pipe is etc...
Another good reason for single wastegate is if you have a wastegate fault.
If one doesn't open, you're applying massive pressure to two cylinders (1 scroll).
If it doesn't open with a single wastegate (or leaks etc) then you'll know about it right away.
And if it's a racecar, then weight and simplicity is very important.
I disagree with it spooling faster with dual gates. I'm sure Ted B can comment on his setup. You will prob lose a little power when the gate opens as the scrolls can bleed over into each other, but it will depend on how long the wastegate pipe is etc...
i know that one of the old cummis engine had only one wg, only on one dvider, but is it good for egine ? i don't think so
Feb 3, 2011, 01:55 PM
#26
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don't get me wrong, i was thinking about when let say (for simplitycy) we have on cylinder 1&4 wg and on 2&3 we don't have, so on 1&4 we have almost non backpressure and on 2&3 we have preaty big BP
Feb 3, 2011, 03:44 PM
#27
The problem with pulse flow is that simply because only half of the cylinders are going through it does not mean the port can be half the size. This is why you need a larger A/R housing on a divided setup to make the same power as an undivided housing.
Let's say you take a 44mm gate and split it into two ports with a 3mm divider wall and you put a 1.5mm radius on the inside corners. The 44mm valve has a flow area of 1520mm^2 the divided setup has a total area of 1385mm^2 or 693mm^2 per pair of cylinders.
As an exhaust pulse reach the wastegate on the undivided housing, it has 1520mm^2 of potential wastegate flow area to flow through. On the divided setup, that same exhaust pulse now only has 693mm^2 of flow area to go through, which is about the same as a 30mm wastegate. It's also not round, so the "hydraulic diameter" is smaller and the flow losses will be even higher.
To offer the same pulse flow capability of a 44mm gate with a divided single gate, you would need like a 60mm single gate. If you used something like a 60% scaling factor that can be used on turbine A/R ratios, then you might want something like a 50mm gate. Or a divided 44 would be similar to a single 38mm gate.
Let's say you take a 44mm gate and split it into two ports with a 3mm divider wall and you put a 1.5mm radius on the inside corners. The 44mm valve has a flow area of 1520mm^2 the divided setup has a total area of 1385mm^2 or 693mm^2 per pair of cylinders.
As an exhaust pulse reach the wastegate on the undivided housing, it has 1520mm^2 of potential wastegate flow area to flow through. On the divided setup, that same exhaust pulse now only has 693mm^2 of flow area to go through, which is about the same as a 30mm wastegate. It's also not round, so the "hydraulic diameter" is smaller and the flow losses will be even higher.
To offer the same pulse flow capability of a 44mm gate with a divided single gate, you would need like a 60mm single gate. If you used something like a 60% scaling factor that can be used on turbine A/R ratios, then you might want something like a 50mm gate. Or a divided 44 would be similar to a single 38mm gate.
Last edited by 03whitegsr; Feb 3, 2011 at 03:46 PM.
Feb 3, 2011, 08:41 PM
#28
A wastegate can have an effect on power if the wg is too small and cant bypass the proper amount of exhaust the backpressure will go up. If the WG is too small it will also cause boost creep issues. Too large a wg will cause boost too fall off. A lot of wastegate dynamics have to do with the flow of the exhaust and the turbine housing. You can do a lot with a 2in 2' long exhaust. You are oversimplifying.
Wastegate size is not related to power. It's related to the size of your motor, the size of your turbo, and how much boost you plan to run on it.
The more boost, the less wastegate you need.
The bigger the turbo the less wastegate you need.
(all else being equal)
Divided and or twin scroll turbo setups do not need two waste-gates but they do need two separate exhaust paths between the port and the turbo, if they don't then you lose some of the added efficiency of the split pulses.
I like evodan run two tial 44-'s with about 22 lbs of pressure on the gate.
Scorke
The more boost, the less wastegate you need.
The bigger the turbo the less wastegate you need.
(all else being equal)
Divided and or twin scroll turbo setups do not need two waste-gates but they do need two separate exhaust paths between the port and the turbo, if they don't then you lose some of the added efficiency of the split pulses.
I like evodan run two tial 44-'s with about 22 lbs of pressure on the gate.
Scorke
Feb 3, 2011, 09:33 PM
#29
Single 44mm WG on a twinscroll manifold right here. The way it's designed, it doesn't isolate 1/2 of the WG valve when that valve is opened, so functionally it isn't 1/2 WG per side. No issues, no boost creep here. But then again, I don't do a great deal of 'wasting' ... well not until 4th gear anyway. 
Whoomp! There it is ...
http://www.youtube.com/watch?v=Z-FPimCmbX8
http://www.youtube.com/watch?v=Z-FPimCmbX8
