how do the stock seq. turbos work?
11-30-01, 03:38 PM
#1
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how do the stock seq. turbos work?
i know the boost pattern is 10-8-10 the first turbo putting out 10 psi. but i dont know what happens after that. the 8 is the transitional phase where i dont get do both turbos put out 8 psi each then the final stage to both turbos again put out 10 psi each or 5 psi each making it 10?
thanks
thanks
11-30-01, 05:46 PM
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Ok here goes....
Before 4500rpm, only the first turbo is spinning. As you get closer to 4500rpm, the prespool actuator begins to open to send additional exhaust over to the 2nd turbo to get it almost up to speed by the time it hits 4500rpm. During this prespool up period, any boost being created by the 2nd turbo is being vented. There is also a small door which prevents any boost from the 1st turbo to mix with the 2nd turbo at the moment.
Once 4500rpm hits, the turbo control actuator opens up a flap allowing an exual amount of exhaust to reach the 2nd turbo, the vent flap closes, and the between the 2nd turbo and the 1st turbo is opened. The STOCK ECU only controls the wastegate past 4500rpm, so now both turbos are being regulated by the wategate.
One of the ways of controlling primary boost pressure is by adjusting the prespool. The more prespool you have, the more exhaust gases are directed to the 2nd turbo, but this is what can cause a boost spike at 4500rpm. The DIP at 4500rpm is caused by the 2nd turbo not being up to full speed yet. It takes just a few moments to speed it up to the regular boost pressure. Prespooling the 2nd turbo may cause less primary boost pressure but WILL enable the 2nd turbo to spin faster at 4500rpm to have less of a dip. Prespool the 2nd turbo TOO much and you get the 4500rpm boost spike.
This is why so many people get boost controllers and Home Depot Valves. When you start opening up the exhaust, it becomes a pain to control the entire thing, and the stock ecu doesn't do a very good job at it.
It gets MUCH more detailed than this, but this is a good start on how it works.
Before 4500rpm, only the first turbo is spinning. As you get closer to 4500rpm, the prespool actuator begins to open to send additional exhaust over to the 2nd turbo to get it almost up to speed by the time it hits 4500rpm. During this prespool up period, any boost being created by the 2nd turbo is being vented. There is also a small door which prevents any boost from the 1st turbo to mix with the 2nd turbo at the moment.
Once 4500rpm hits, the turbo control actuator opens up a flap allowing an exual amount of exhaust to reach the 2nd turbo, the vent flap closes, and the between the 2nd turbo and the 1st turbo is opened. The STOCK ECU only controls the wastegate past 4500rpm, so now both turbos are being regulated by the wategate.
One of the ways of controlling primary boost pressure is by adjusting the prespool. The more prespool you have, the more exhaust gases are directed to the 2nd turbo, but this is what can cause a boost spike at 4500rpm. The DIP at 4500rpm is caused by the 2nd turbo not being up to full speed yet. It takes just a few moments to speed it up to the regular boost pressure. Prespooling the 2nd turbo may cause less primary boost pressure but WILL enable the 2nd turbo to spin faster at 4500rpm to have less of a dip. Prespool the 2nd turbo TOO much and you get the 4500rpm boost spike.
This is why so many people get boost controllers and Home Depot Valves. When you start opening up the exhaust, it becomes a pain to control the entire thing, and the stock ecu doesn't do a very good job at it.
It gets MUCH more detailed than this, but this is a good start on how it works.
11-30-01, 07:22 PM
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Here's a good site with some more info for ya
http://home.istar.ca/~dvandit/TurbochargerOverview.htm
http://home.istar.ca/~dvandit/TurbochargerOverview.htm
11-30-01, 09:26 PM
#5
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Originally posted by Flybye
Ok here goes....
Before 4500rpm, only the first turbo is spinning. As you get closer to 4500rpm, the prespool actuator begins to open to send additional exhaust over to the 2nd turbo to get it almost up to speed by the time it hits 4500rpm. During this prespool up period, any boost being created by the 2nd turbo is being vented. There is also a small door which prevents any boost from the 1st turbo to mix with the 2nd turbo at the moment.
Once 4500rpm hits, the turbo control actuator opens up a flap allowing an exual amount of exhaust to reach the 2nd turbo, the vent flap closes, and the between the 2nd turbo and the 1st turbo is opened. The STOCK ECU only controls the wastegate past 4500rpm, so now both turbos are being regulated by the wategate.
One of the ways of controlling primary boost pressure is by adjusting the prespool. The more prespool you have, the more exhaust gases are directed to the 2nd turbo, but this is what can cause a boost spike at 4500rpm. The DIP at 4500rpm is caused by the 2nd turbo not being up to full speed yet. It takes just a few moments to speed it up to the regular boost pressure. Prespooling the 2nd turbo may cause less primary boost pressure but WILL enable the 2nd turbo to spin faster at 4500rpm to have less of a dip. Prespool the 2nd turbo TOO much and you get the 4500rpm boost spike.
This is why so many people get boost controllers and Home Depot Valves. When you start opening up the exhaust, it becomes a pain to control the entire thing, and the stock ecu doesn't do a very good job at it.
It gets MUCH more detailed than this, but this is a good start on how it works.
Ok here goes....
Before 4500rpm, only the first turbo is spinning. As you get closer to 4500rpm, the prespool actuator begins to open to send additional exhaust over to the 2nd turbo to get it almost up to speed by the time it hits 4500rpm. During this prespool up period, any boost being created by the 2nd turbo is being vented. There is also a small door which prevents any boost from the 1st turbo to mix with the 2nd turbo at the moment.
Once 4500rpm hits, the turbo control actuator opens up a flap allowing an exual amount of exhaust to reach the 2nd turbo, the vent flap closes, and the between the 2nd turbo and the 1st turbo is opened. The STOCK ECU only controls the wastegate past 4500rpm, so now both turbos are being regulated by the wategate.
One of the ways of controlling primary boost pressure is by adjusting the prespool. The more prespool you have, the more exhaust gases are directed to the 2nd turbo, but this is what can cause a boost spike at 4500rpm. The DIP at 4500rpm is caused by the 2nd turbo not being up to full speed yet. It takes just a few moments to speed it up to the regular boost pressure. Prespooling the 2nd turbo may cause less primary boost pressure but WILL enable the 2nd turbo to spin faster at 4500rpm to have less of a dip. Prespool the 2nd turbo TOO much and you get the 4500rpm boost spike.
This is why so many people get boost controllers and Home Depot Valves. When you start opening up the exhaust, it becomes a pain to control the entire thing, and the stock ecu doesn't do a very good job at it.
It gets MUCH more detailed than this, but this is a good start on how it works.
11-30-01, 11:11 PM
#6
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The STOCK ECU only controls the wastegate past 4500rpm, so now both turbos are being regulated by the wategate.
11-30-01, 11:42 PM
#7
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Originally posted by neevosh
Are you sure that's right?...
Are you sure that's right?...
Yep, you are wrong :p
Quote STRAIGHT from the shop manual:
High-Speed, Heavy-load range
In the high-speed heavy-load range, the turbo control valve is opened, and maximum boost pressure is created by the primary and secondary turbochargers. When both turbochargers are actuated, supercharged pressure control (duty) is done by the wastegate control valve.
There is also a chart in the manual showing, actually, that the wastegate is 95% closed during boosting of only the first turbo.
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12-01-01, 07:20 PM
#8
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Boost Control During Low Power
Wastegate closed
Primary (front) turbo spinning but no boost
Precontrol, charge control, turbo control valves closed
Charge relief valve open
Secondary (rear) turbo not spinning
High Power < 4500 RPM
Primary turbo spins up and creates boost
Wastegate opens to prevent over-boost
Precontrol valve begins to open to spin up the secondary turbo
Turbo control valve closed
Charge control valve in Y-pipe is closed, preventing secondary turbo from supplying boost
Charge relief valve is open, venting boost created by secondary turbo
High Power > 4500 RPM
Primary turbo creating boost
Wastegate open to prevent over-boost, wastegate can be overwhelmed on highly modified cars causing boost creep
Precontrol valve full open
Turbo control valve opens to supply secondary turbo with maximum exhaust
Charge relief valve closes - stops venting secondary turbo's boost
Charge control valve in Y-pipe opens to allow secondary turbo boost into Y-pipe creating a momentary boost spike
Wastegate closed
Primary (front) turbo spinning but no boost
Precontrol, charge control, turbo control valves closed
Charge relief valve open
Secondary (rear) turbo not spinning
High Power < 4500 RPM
Primary turbo spins up and creates boost
Wastegate opens to prevent over-boost
Precontrol valve begins to open to spin up the secondary turbo
Turbo control valve closed
Charge control valve in Y-pipe is closed, preventing secondary turbo from supplying boost
Charge relief valve is open, venting boost created by secondary turbo
High Power > 4500 RPM
Primary turbo creating boost
Wastegate open to prevent over-boost, wastegate can be overwhelmed on highly modified cars causing boost creep
Precontrol valve full open
Turbo control valve opens to supply secondary turbo with maximum exhaust
Charge relief valve closes - stops venting secondary turbo's boost
Charge control valve in Y-pipe opens to allow secondary turbo boost into Y-pipe creating a momentary boost spike
Although some state primary boost is only controlled by the precontrol WG, my testing suggested it works in parallel with the main WG to control primary boost. PLEASE, someone with a stock set-up, plug the line to the WG solenoid valve, and see if primary boost drops (this would reassure me, and be proof for doubters). Mine did, but I tested my car with heavy mods. This test is safe.
Kevin Kelleher
Kevin Kelleher
:p
12-01-01, 08:41 PM
#9
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Hehe
This came from http://home.istar.ca/~dvandit/TurbochargerOverview.htm
Now the Mazda Service Highlights Shop Manual NEVER mentions boost pressure being controlled by the wastegate during Low-speed/Light-load range or the Medium-speed/Medium-load range. It's only reference towards wastegate control is during the High-speed/Heavy-load range which is when boost pressure is created by both turbochargers, and you know boost pressure is created by both turbocharges at 4,500rpm+.
My manual: 1
My funky website: 1
Total = 2
You and Rob's site: 1
Total = 1
I think to finaly solve this, I'm going to have to connect a T between the wastegate and the solenoid. If the solenoid is not allowing pressure to build up in the wastegate to open it to vent exhaust, then you know it's not being used to control boost during primary charge, but my FD is in pieces right now because of a few things I'm doing, so I guess YOU are going to have to conduct this little test
0 to 3,000 RPM
In this RPM range, boost is produced by only the Primary Turbocharger. At this time, most of the the exhaust is directed to the Primary Turbo by the Turbo Control, and the Secondary Compressor is isolated from the Primary by the Charge Control. Boost pressure is regulated by the Turbo Pre-Control.
In this RPM range, boost is produced by only the Primary Turbocharger. At this time, most of the the exhaust is directed to the Primary Turbo by the Turbo Control, and the Secondary Compressor is isolated from the Primary by the Charge Control. Boost pressure is regulated by the Turbo Pre-Control.
Now the Mazda Service Highlights Shop Manual NEVER mentions boost pressure being controlled by the wastegate during Low-speed/Light-load range or the Medium-speed/Medium-load range. It's only reference towards wastegate control is during the High-speed/Heavy-load range which is when boost pressure is created by both turbochargers, and you know boost pressure is created by both turbocharges at 4,500rpm+.
My manual: 1
My funky website: 1
Total = 2
You and Rob's site: 1
Total = 1
I think to finaly solve this, I'm going to have to connect a T between the wastegate and the solenoid. If the solenoid is not allowing pressure to build up in the wastegate to open it to vent exhaust, then you know it's not being used to control boost during primary charge, but my FD is in pieces right now because of a few things I'm doing, so I guess YOU are going to have to conduct this little test
12-02-01, 02:53 AM
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Wow, I really learned a lot about the sequential system trying to argue this topic. I had a general understanding before but now I really know what's going on. I think you may be right about the pre-control but I still think the wastegate controls boost somewhat with the 1st turbo. I went non-sequential a few months ago so I can't test it either. I wish some more people could've gotten in on this discussion. Oh well, looks like it ends here with me admitting defeat.
11-01-04, 07:26 AM
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If anyone notices, both rods have to push out to open the valves
Yeah this next pic is big, but be happy it is
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