While searching for info on external wastegates, I came across this post in the list archives. I'm sure most of you already know this info, but it helped me understand our trucks a little better. It will probably help other newbies out there. Thanks for the nice write up BG.
Zac
_______________________________________________________________________
To: rwenson@suncoastcreations.com
Subject: Re: [ISTA] Catalytic Q... (Brians Boost control 101 Posts... Long!)
From: Bullyhart@aol.com
Date: Mon, 18 Oct 1999 07:14:04 EDT
The modification you are contemplating have caused some folks in the past to
experience boost spikes and boost creep. The thoughts in the past were that
the wastegate orifice was not large enough to bleed off enough exaust presure
to maintain the desired boost level, when backpressure was lowered. Ivan has
recently been doing some research on whether our whole Turbo exaust housing
may be a contributing factor to undesired boost characteristics, when one
lowers the backpressure in our application.
See Brians old Boost 101 post below for the whole story.............
-----------------------
This is a topic that comes up often on the list, and we get many questions
about it....so after a few requests i wanted to post to the list about the
full boost control system on the Sy/Ty. Most understand the system, but
many of the newbies don't understand the full concept at all, or are a bit
fuzzy on it.
First the wastegate. The turbo spins via exhaust gas pressure, exiting the
turbo thru the exhaust housing. It spins the exhaust turbine, spinning the
compressor wheel, creating a pressurized environment in the
intercooler/intake. The boost level is now determined by the amount of air
moved by the turbo. The turbo's amount of air moved (not considering turbo
efficiencies here) depends on the the rpm of the turbo, and that is directly
related to the amount of exhaust gases/pressure present in the exhaust
housing of the turbo. So at more load/higher RPM, there is more exhaust
gas, leading to more boost. So, how is boost controlled? Exhaust gas
pressure needs to be lessened in the exhaust housing. So exhaust pressure
needs be leaked out at a controlled rate, either before the turbo or
directly from the exhaust turbine. In the stock syty system we have an
integral wastegate (integral to the turbo, part of the exhaust housing).
Many use an external wastegate, not part of the turbo, and before the turbo,
at a crossover pipe, or part of the exhaust manifolds. The integral
wastegate has an oriface that directly leaks gas out of the exhaust turbine.
The wastegate puck seals this oriface shut, so no gas can leak out. Think
of it as a door letting exhaust gas out or not letting it out. Depending on
its position (from fully closed to fully open) the exhaust exits at
different rates, or not at all. This puck is connected to an arm, that is
visible outside the turbo. Move the lever back and forth, that is the
wastegate opening and closing. No resistance at that part (there shouldn't
be). It is connected to the actuator, and actuator arm. The actuator is a
pneumatically operated device that converts air pressure to a linear motion,
using a diaphragm and spring. The actuator will move the arm fully open at
~10-12psi of pressure. So with no solenoid in the system, and a boost
pressure source connected directly to the actuator, you will (should) get
10-12psi, as that is when the wastegate will be opened by the actuator
directly. Now why do you get more boost with a different chip/boost
controller? The solenoid is a device that goes between the boost pressure
source and the actuator. This modifies the actual pressure/air that goes in
the line to the actuator. So if you have 13psi, and the solenoid is
restricting air to the actuator, it may not see that full amount of
pressure, maybe 10psi. So the wastegate does not open yet. When it is
15psi boost, the actuator may modify the source so that the actuator 'sees'
12psi, and now opens. The solenoid does this by using a duty cycle of a
small mechanism (I tore one open the other day, looks like a small needle
valve with spring tension). With varying duty cycles, the solenoid lets
more or less air through, out of the solenoid. On diacom this will read as
100% when the wastegate is clammed shut (desiring more boost) and much less
than that (30-70%) when the ecm is commanding the solenoid to let full boost
thru to open the wastegate via the actuator. With the stock
ECM/calibration, and some aftermarket controllers, this is a closed loop
type of operation, meaning it reads the boost via a map sensor, then adjusts
the wastegate duty cycle based on the desired boost level, in order to
increase boost (close wastegate a bit) or decrease boost (open wastegate
more).
Boost Control for newbies
Part 2
Wastegate Arm Adjustments
The wastegate arm (or wastegate rod) is the connection from the wastegate
actuator to the wastegate lever itself. The wastegate lever itself is free
moving, swinging freely. If it does not move freely (when disconnected from
the wastegate rod) there is a problem, something impeding movement, and this
needs to be fixed. Some stick intermittently, or only when HOT. The
wastegate actuator is spring loaded, clamping the wastegate closed when
there is no boost source. When pressure is applied to the actuator, the
actuator opens the wastegate. The rod's length can be adjusted. This will
mean that the wastegate itself will have a different rate of bleeding of the
exhaust depending on the adjustment. Good pictures and diagnostic tests are
in the Syclone/Typhoon Service Supplement (on the CD Rom I believe). The
wastegate rod is connected to the wastegate lever. The lever has a pin, the
rod slips on to it, and a retaining clip thru the wastegate lever hold the
arm/lever together. If you pull the pin, and slip the rod off the lever,
the hole on the arm and the lever's pin should overlap slightly. In the
manual it states to look for 1/2 overlap, so you'd have to pull the arm out
of the actuator slightly (tight spring tension here) to connect the arm to
the lever's pin. I believe the overlap spec has been updated so factory
specs are now 7/8 overlap (basically a looser/longer rod setup). The arm's
length can be adjusted as the rod end is threaded onto the rod. Tightening
the end will shorten the wastegate, loosening lengthens it. If the rod is
shorter, the wastegate is clamped more tightly shut. If the rod is longer,
the wastegate is held loosely shut. If the rod is shorter, the actuator
requires more boost pressure to open the wastegate the same distance as if
it were adjusted longer. Result - more boost, faster spool up, as the
wastegate is not opening quite as much, and not as quickly. The opposite
goes if you lengthen the rod. If you are using a feedback type of control
(3 bar chip/ aftermarket high performance controller) the adjustments won't
have the same exact effect as it would on a non feedback type of control
(ANS controller, bleeder valve, stock chip if you are running more than
15psi, as it cannot feedback control boost levels it cannot sense). On the
non feedback controlled setups, adjusting your wastegate rod will adjust
your boost level, and its response. On a feedback type of control,
adjusting the rod will adjust the response more than the full boost level
reached. It will affect the actual boost level, but it will usually take a
more extreme response to do so, since your control system will take this
change into account (with minor changes that is, but if you tighten TOO
much, the wastegate may not be able to reach full open to bleed off enough
pressure, not to mention what your wastegate can flow period). So you can
dial in your wastegate rod to give you results closer to what you desire, as
long as your system is working up to par. The actuator can also be out of
spec, and there are full diagnostics for making sure it is working as it
should.
External Wastegates
An external wastegate is a wastegate that is designed separate from the
turbo itself. Some externals have been used in designs that mount it near
or on the turbo itself though (Turbonetics has some designs like this, the
ATR setup for syty's is this way). Externals typically have a lot more flow
capability than integral wastegates (sometimes you'll see HP ratings for
wastegates). Most have dual port actuators also. This setup uses two ports
on the actuator diaphragm in order to initiate movement of the wastegate's
shaft/puck. This can make for a quick opening wastegate, for better spool
up/control. Many people mount externals on the crossover pipe on syty's (on
Buicks as well) with great results. Kenne Bell headers have a mount for a
Richard Lee external wastegate on their crossover pipe. If you want to use
one on a stock type syty, you'll need to custom fabricate a mount for your
wastegate. Most external wastegate kits include a flange for mounting
purposes. If you are making a HIGH HP ( 500+ ) syty up, an external (or
multiple) is the ONLY way to go. The output of these wastegates can be
routed back into the exhaust, or vented to atmosphere (LOUD!!). If you do
vent to atmosphere, you can put a pipe/muffler on the output to quiet it
some. I use an HKS wastegate mounted on my crossover pipe, with a simple
regulator for control. Boost is rock solid and easily controlled.
some links:
www.turbonetics.com See Deltagate/Racegate
www.hksusa.com HKS has 2 models of wastegate also
Aftermarket Boost Controllers
In my book, there are 3 different types of aftermarket controllers. The
first being non electronic, basically adjustable bleeder valve/regulator
types. These are no more than hyped up pressure regulators, as used in air
compressor systems, fish aquariums, industrial pressure applications. The
hardware is usually just a knob actuated device with vacuum connections.
This design works fine, as long as you have a wastegate that works GREAT.
Otherwise, these are subject to spikes and boost creep. Definitions - boost
spike - when the boost level spools up and shoots past the set limit, then
settles back down. Boost creep - boost slowly rises over the set boost
level. The main thing here, is that if you think of using one of these, you
can pay a lot less by buying one from a different source (usually $20-50
rather than $75-150). I usually think of the last two (electronic
controllers) in two different categories. The simpler one being basic
controllers that will put out a simple duty cycle to your solenoid, or use a
different solenoid that just varies duty cycle on twists of the adjustment
knob. These are usually cheaper, and don't provide for the same performance
as the higher end electronic controllers. The duty cycle remains the same
on the solenoid, letting the wastegate start creeping open. Also, should
creep/spikes occur, the controller does nothing to fight this. The more
complicated electronic controllers (Greddy Profec, HKS EVC, Apex, Blitz etc
etc) use a feedback control setup. They know what the boost level is, via a
map sensor (usually internal), and will adjust their controls based on what
the current level is. When installed correctly with a good performing
wastegate, they provide for solid control with great spool up. The fuzzy
logic ones claim to 'learn' the characteristics of your turbo system,
supposedly making them able to eliminate spikes and creep. These setups are
more expensive, and can be a pain to install and program. From what I've
seen, if you have a bad performing wastegate, one of these setups won't help
matters. If your wastegate is up to spec however, one of these controllers
will work fine, and may even give better performance.
I hope this is helping someone understand the subject better
Brian Green
Syclone 160
STG
Zac
_______________________________________________________________________
To: rwenson@suncoastcreations.com
Subject: Re: [ISTA] Catalytic Q... (Brians Boost control 101 Posts... Long!)
From: Bullyhart@aol.com
Date: Mon, 18 Oct 1999 07:14:04 EDT
The modification you are contemplating have caused some folks in the past to
experience boost spikes and boost creep. The thoughts in the past were that
the wastegate orifice was not large enough to bleed off enough exaust presure
to maintain the desired boost level, when backpressure was lowered. Ivan has
recently been doing some research on whether our whole Turbo exaust housing
may be a contributing factor to undesired boost characteristics, when one
lowers the backpressure in our application.
See Brians old Boost 101 post below for the whole story.............
-----------------------
This is a topic that comes up often on the list, and we get many questions
about it....so after a few requests i wanted to post to the list about the
full boost control system on the Sy/Ty. Most understand the system, but
many of the newbies don't understand the full concept at all, or are a bit
fuzzy on it.
First the wastegate. The turbo spins via exhaust gas pressure, exiting the
turbo thru the exhaust housing. It spins the exhaust turbine, spinning the
compressor wheel, creating a pressurized environment in the
intercooler/intake. The boost level is now determined by the amount of air
moved by the turbo. The turbo's amount of air moved (not considering turbo
efficiencies here) depends on the the rpm of the turbo, and that is directly
related to the amount of exhaust gases/pressure present in the exhaust
housing of the turbo. So at more load/higher RPM, there is more exhaust
gas, leading to more boost. So, how is boost controlled? Exhaust gas
pressure needs to be lessened in the exhaust housing. So exhaust pressure
needs be leaked out at a controlled rate, either before the turbo or
directly from the exhaust turbine. In the stock syty system we have an
integral wastegate (integral to the turbo, part of the exhaust housing).
Many use an external wastegate, not part of the turbo, and before the turbo,
at a crossover pipe, or part of the exhaust manifolds. The integral
wastegate has an oriface that directly leaks gas out of the exhaust turbine.
The wastegate puck seals this oriface shut, so no gas can leak out. Think
of it as a door letting exhaust gas out or not letting it out. Depending on
its position (from fully closed to fully open) the exhaust exits at
different rates, or not at all. This puck is connected to an arm, that is
visible outside the turbo. Move the lever back and forth, that is the
wastegate opening and closing. No resistance at that part (there shouldn't
be). It is connected to the actuator, and actuator arm. The actuator is a
pneumatically operated device that converts air pressure to a linear motion,
using a diaphragm and spring. The actuator will move the arm fully open at
~10-12psi of pressure. So with no solenoid in the system, and a boost
pressure source connected directly to the actuator, you will (should) get
10-12psi, as that is when the wastegate will be opened by the actuator
directly. Now why do you get more boost with a different chip/boost
controller? The solenoid is a device that goes between the boost pressure
source and the actuator. This modifies the actual pressure/air that goes in
the line to the actuator. So if you have 13psi, and the solenoid is
restricting air to the actuator, it may not see that full amount of
pressure, maybe 10psi. So the wastegate does not open yet. When it is
15psi boost, the actuator may modify the source so that the actuator 'sees'
12psi, and now opens. The solenoid does this by using a duty cycle of a
small mechanism (I tore one open the other day, looks like a small needle
valve with spring tension). With varying duty cycles, the solenoid lets
more or less air through, out of the solenoid. On diacom this will read as
100% when the wastegate is clammed shut (desiring more boost) and much less
than that (30-70%) when the ecm is commanding the solenoid to let full boost
thru to open the wastegate via the actuator. With the stock
ECM/calibration, and some aftermarket controllers, this is a closed loop
type of operation, meaning it reads the boost via a map sensor, then adjusts
the wastegate duty cycle based on the desired boost level, in order to
increase boost (close wastegate a bit) or decrease boost (open wastegate
more).
Boost Control for newbies
Part 2
Wastegate Arm Adjustments
The wastegate arm (or wastegate rod) is the connection from the wastegate
actuator to the wastegate lever itself. The wastegate lever itself is free
moving, swinging freely. If it does not move freely (when disconnected from
the wastegate rod) there is a problem, something impeding movement, and this
needs to be fixed. Some stick intermittently, or only when HOT. The
wastegate actuator is spring loaded, clamping the wastegate closed when
there is no boost source. When pressure is applied to the actuator, the
actuator opens the wastegate. The rod's length can be adjusted. This will
mean that the wastegate itself will have a different rate of bleeding of the
exhaust depending on the adjustment. Good pictures and diagnostic tests are
in the Syclone/Typhoon Service Supplement (on the CD Rom I believe). The
wastegate rod is connected to the wastegate lever. The lever has a pin, the
rod slips on to it, and a retaining clip thru the wastegate lever hold the
arm/lever together. If you pull the pin, and slip the rod off the lever,
the hole on the arm and the lever's pin should overlap slightly. In the
manual it states to look for 1/2 overlap, so you'd have to pull the arm out
of the actuator slightly (tight spring tension here) to connect the arm to
the lever's pin. I believe the overlap spec has been updated so factory
specs are now 7/8 overlap (basically a looser/longer rod setup). The arm's
length can be adjusted as the rod end is threaded onto the rod. Tightening
the end will shorten the wastegate, loosening lengthens it. If the rod is
shorter, the wastegate is clamped more tightly shut. If the rod is longer,
the wastegate is held loosely shut. If the rod is shorter, the actuator
requires more boost pressure to open the wastegate the same distance as if
it were adjusted longer. Result - more boost, faster spool up, as the
wastegate is not opening quite as much, and not as quickly. The opposite
goes if you lengthen the rod. If you are using a feedback type of control
(3 bar chip/ aftermarket high performance controller) the adjustments won't
have the same exact effect as it would on a non feedback type of control
(ANS controller, bleeder valve, stock chip if you are running more than
15psi, as it cannot feedback control boost levels it cannot sense). On the
non feedback controlled setups, adjusting your wastegate rod will adjust
your boost level, and its response. On a feedback type of control,
adjusting the rod will adjust the response more than the full boost level
reached. It will affect the actual boost level, but it will usually take a
more extreme response to do so, since your control system will take this
change into account (with minor changes that is, but if you tighten TOO
much, the wastegate may not be able to reach full open to bleed off enough
pressure, not to mention what your wastegate can flow period). So you can
dial in your wastegate rod to give you results closer to what you desire, as
long as your system is working up to par. The actuator can also be out of
spec, and there are full diagnostics for making sure it is working as it
should.
External Wastegates
An external wastegate is a wastegate that is designed separate from the
turbo itself. Some externals have been used in designs that mount it near
or on the turbo itself though (Turbonetics has some designs like this, the
ATR setup for syty's is this way). Externals typically have a lot more flow
capability than integral wastegates (sometimes you'll see HP ratings for
wastegates). Most have dual port actuators also. This setup uses two ports
on the actuator diaphragm in order to initiate movement of the wastegate's
shaft/puck. This can make for a quick opening wastegate, for better spool
up/control. Many people mount externals on the crossover pipe on syty's (on
Buicks as well) with great results. Kenne Bell headers have a mount for a
Richard Lee external wastegate on their crossover pipe. If you want to use
one on a stock type syty, you'll need to custom fabricate a mount for your
wastegate. Most external wastegate kits include a flange for mounting
purposes. If you are making a HIGH HP ( 500+ ) syty up, an external (or
multiple) is the ONLY way to go. The output of these wastegates can be
routed back into the exhaust, or vented to atmosphere (LOUD!!). If you do
vent to atmosphere, you can put a pipe/muffler on the output to quiet it
some. I use an HKS wastegate mounted on my crossover pipe, with a simple
regulator for control. Boost is rock solid and easily controlled.
some links:
www.turbonetics.com See Deltagate/Racegate
www.hksusa.com HKS has 2 models of wastegate also
Aftermarket Boost Controllers
In my book, there are 3 different types of aftermarket controllers. The
first being non electronic, basically adjustable bleeder valve/regulator
types. These are no more than hyped up pressure regulators, as used in air
compressor systems, fish aquariums, industrial pressure applications. The
hardware is usually just a knob actuated device with vacuum connections.
This design works fine, as long as you have a wastegate that works GREAT.
Otherwise, these are subject to spikes and boost creep. Definitions - boost
spike - when the boost level spools up and shoots past the set limit, then
settles back down. Boost creep - boost slowly rises over the set boost
level. The main thing here, is that if you think of using one of these, you
can pay a lot less by buying one from a different source (usually $20-50
rather than $75-150). I usually think of the last two (electronic
controllers) in two different categories. The simpler one being basic
controllers that will put out a simple duty cycle to your solenoid, or use a
different solenoid that just varies duty cycle on twists of the adjustment
knob. These are usually cheaper, and don't provide for the same performance
as the higher end electronic controllers. The duty cycle remains the same
on the solenoid, letting the wastegate start creeping open. Also, should
creep/spikes occur, the controller does nothing to fight this. The more
complicated electronic controllers (Greddy Profec, HKS EVC, Apex, Blitz etc
etc) use a feedback control setup. They know what the boost level is, via a
map sensor (usually internal), and will adjust their controls based on what
the current level is. When installed correctly with a good performing
wastegate, they provide for solid control with great spool up. The fuzzy
logic ones claim to 'learn' the characteristics of your turbo system,
supposedly making them able to eliminate spikes and creep. These setups are
more expensive, and can be a pain to install and program. From what I've
seen, if you have a bad performing wastegate, one of these setups won't help
matters. If your wastegate is up to spec however, one of these controllers
will work fine, and may even give better performance.
I hope this is helping someone understand the subject better
Brian Green
Syclone 160
STG