7.3L Powerstroke Diesel Turbo Stall

This article deals with the common problem of
turbo stall and turbo surge experienced by many modified
Powerstroke diesels. The condition known as turbo surge or
stall occurs under heavy load conditions where boost pressures
are elevated. The root cause is generally an imbalance of
essures between the turbine side and the compressor side of
the turbo. When the forces on the turbine are no longer strong
ough to drive the compressor side of the turbo adequately,
stall occurs. Often on Powerstrokes the stall will manifest
self as a surging and the boost pressure in the manifold
will fluctuate as the vehicle surges and you can hear an
dible cyclic sound which corresponds with the
surge.


The truck used for this article is my own 2001, F250
Powerstroke, crew cab, long box 4×4. The truck has a 4″
exhaust, aFe intake, gauges and Banks Big Hoss 120hp chip. I
uld experience turbo stall/surge when towing a 30′ travel
trailer weighing about 10,000# over the passes at highway
eeds of 65-75mph. When the boost would reach 17-22psi the
stall/surge would be very strong and the boost would oscillate
4psi while making a wooh-wooh sound. If the throttle were
pressed further so the boost would climb to 23-28psi boost the
rge would go away, but its hard to explain to the state
patrol why you are pulling a trailer at 90mph up hill.


The following is some information about our experience with
this problem, its causes and how to fix it.  The fix
self was quite simple, we installed a Banks quick turbo and
compressor wheel and a Big Head actuator.  This resolved
e problem completely.  The following are some photos
and things which were observed and changed while the truck was
art.


Performance with Banks Turbo

When the truck was driven with the Banks turbo housing,
compressor wheel and Big Head actuator no apparent performance
in was recognized. In fact the turbo comes on slower in the
low end than the stock unit and we experienced considerably
re turbo whistle than the stock unit as well. Mid range and
high end performance seems about the same as stock with the
me top boost pressures experienced at about 28psi. Under
load towing where severe surge was experienced, absolutely no
rge with Banks.

Next we tried the Banks Turbo housing
with Big Head actuator and the stock compressor wheel. This
duced the whistle and helped bring back some of the low end.
However under heavy load conditions an audible surging sound
present, but the boost gauge does not fluctuate. We
suspected that the sound was being caused by the waste gate
ying to open so a ball was placed in the tube leading tot he
actuator to plug it. With the ball in place a noticeable
duction of the sound previously heard under heavy load
conditions was present. The plugging of the Big Head actuator
d not completely stop the sound but reduced it by more than
half.

From this experience it would appear that the
jority of the turbo surge or stall experienced with modified
trucks especially those using large horse power chips which
oduce high boost pressures is associated with the waste
gate. It would seem that the exhaust pressure against the
ste gate is at least a contributing factor in unseating the
waste gate allowing it to flutter effecting the pressures in
e turbo charger.

The combination of the Banks turbo
housing, compressor wheel and big head actuator work together
resolve the surge because the turbo housing is larger and
flows more reducing the back pressure behind the turbine. The
mpressor wheel reduces the amount of drag on the
wheel reducing the load on the turbine. The Big Head
actuator with its larger, stronger spring helps to keep the
waste gate shut.  Since this was initially done we have
found most cases of turbo strall can be resloved by replacing
the stock compressor wheel with the Banks wheel and either
plugging the actuator line to the waste gate or replacing it
with a Banks Big head actuator.  It is probably best to
use the Banks Big Head so that control for opening the waste
gate is not dependant soley on exhaust back
pressure.















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This is a photo of the original turbo housing waste
gate. It is evident in the photo that the waste gate
sealing is rough and has been leaking around one side.
We suspect that the waste gate opening and closing
against the spring of the stock actuator was at least
part of the problem causing the surge and stall
problems. Under high load conditions exhaust pressure
builds up behind the turbine would act to try and open
the waste gate and the stock actuator spring was just
not enough to keep it closed. The new Banks Big Head
actuator has a much stronger spring and holds the waste
gate shut much tighter than the stock one. Also the
waste gate seat area of the Banks quick turbo housing is
better and seals tighter than the stock
one.



















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This is a picture
of the intake manifold where it connects to the
compressor housing.  It is hard to see in the
photos but the interior surface of the intake manifold
was very rough so it was decided to smooth it out while
the truck was apart.










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Stock intake manifold before
smoothing.

 












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The stock “Y”
pipe that connects to the turbo is very rough inside and
the passenger side makes almost a 90 degree turn into
the turbo, so we decided to smooth this part as
well.









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This is a top
view of the turbine and turbo charger mount.  The
exhaust gases enter the turbine from the mount side and
exit the turbine towards the bottom of the
picture.









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Intake manifold after a little work to smooth it up.
The intake manifold is actually fairly easy to do this
to as it is aluminum. We used a die grinder with course
tootsie rolls to knock off the big bumps, then followed
that with a flapper.


 








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Intake manifold
after smoothing.  The grinding and smoothing of the
entire intake manifold took about 1 hour.






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This is the “Y”
pipe after smoothing.  I don’t think I would do
this again.  The “Y” pipe is very difficult to get
out of the truck and even more difficult to get
aligned properly with the turbo when putting it
back.






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This photo is the
inside of the compressor housing.  The center
opening is the intake to the compressor and is where the
compressor wheel is located.

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This picture shows the difference between the stock
compressor wheel on the left and the Banks compressor
wheel on the right. Every other fin on the Banks
compressor wheel is shorter than the fins on the stock
wheel. Also the Banks wheel is made of a different alloy
than the stock wheel to resist bending under heavy load.
The Banks wheel does whistle more than the stock wheel
and whistles through a larger boost range as
well.


The combination of the Banks quick turbo, compressor
wheel and Big Head actuator gave about the same
performance as the stock parts with a slight increase in
turbo spool up.  The main thing is that the turbo
stall and surge were completely
eliminated.

Article by Dave Meheen of Diesel Power Products.

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