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Introduction
The exhaust flexible joint on my car had suffered damage due to excessive flexing
caused by worn engine mountings (naturally,
according to Murphy's law, this was the newest part of the exhaust system!)
and was blowing and getting worse. I decided that, since the rest of the system
was at least two years old (the length of time I had owned the car), this was
an opportunity to fit an upgraded exhaust system. I intend to add power upgrades
in the near future, and feel that a free-flow exhaust system, apart from adding
some top-end power and reducing turbo lag, will reduce stress on a tuned engine.
I considered three systems: the stainless steel system from Abbott Racing, an
aluminised steel 2.5" system from Jetex and the 3" aluminised steel
"JT" system from Speedparts in Sweden.
Decisions, decisions...
Here was my decision-making process. Naturally, like choice of tyres,
this was based on my own priorities, which may be very different from those
of others. My criteria were:
- Performance improvement
The exhaust system must provide a worthwhile performance improvement, though
not necessarily on its own. I was planning ahead to other performance upgrades,
such as reprogrammed engine management, and intended that the new exhaust
system should help relieve stress from a tuned engine. I was hoping, however,
that a free-flow exhaust alone might reduce turbo lag and provide some small
power increase at high RPM.
- Discreet appearance
I was not in the slightest bit interested in having a tailpipe that marked
me as a "boy racer". The less conspicuous, the better. My ideal
system would have looked identical to the standard 9000 Aero exhaust system.
- Quiet
Although I wanted performance, the last thing I wanted was to turn my executive
car into a Formula-1 style "racing machine". Sometimes, though not
often, I have to drive hundreds of miles at a time. The Aero seats are the
most comfortable and supportive fitted to any 9000 - I didn't want to develop
a headache through exhaust noise (honestly, I have been told by one Saab owner
that the exhaust system on his 900 convertible gave his wife a headache!).
Again, I didn't want to sound like a "boy racer" around town.
So on to the systems I considered...
- The Abbott Racing stainless
steel exhaust system
Being made from stainless steel, this system should last a very long
time. It is not cheap, though. The combined catalytic converter/downpipe for
my '96 Aero alone costs nearly £500. This downpipe is still rather restrictive,
since it is simply a standard downpipe with a high-flow cat core substituted
for the standard core (the '96-on cars have the cat incorporated in the downpipe,
where earlier cars have a separate downpipe and cat). Abbott make a big noise
about the fact that their replacement downpipe for earlier cars removes the
restrictions of the standard downpipe. On '96-on cars, Abbott's solution retains
many of the restrictions since it is based on the standard downpipe. I would
have opted for the earlier-style system with a separate cat had I gone for
an Abbott system. This would have met UK regulations and cost just over £1000.
One thing in its favour is that this system has bolt-together fittings. I
couldn't determine the diameter of the system, but the 3" tailpipe appears
to be bigger than the rest of the system, so I conclude that it is nearer
to 2.5".
I recently spoke to someone who had fitted an Abbott system to a 9000 and
he was disappointed with the very noisy results on an otherwise civilised
car. It seems to be a general trend that stainless steel exhaust systems are
noisier than the equivalent mild steel item.
- The Jetex aluminised steel 2.5"
system
Having heard good reports about this system, I decided to investigate
further. Unlike the Abbott system, there is no option to replace the cat with
a high-flow unit. It is very cheap, though (largely due to the fact that it
doesn't include a cat - it is a cat-back system) at £275. They also
have a stainless steel range, but this does not include the 9000. I was ready
to order one of these, and when I spoke to Jetex in the UK, they promised
to check the stock in their factory, then ring back. They finally rang back
a few weeks later, by which time I had already ordered another system.
I have since learned that the single most important part of the system for
performance is the downpipe. I now feel I might have been disappointed with
the performance of the Jetex system, since it retains the standard downpipe
and cat.
- The Speedparts JT 3" system from Maptun
Control Systems in Sweden
While asking for opinions on Exhaust systems for the 9000 on the Internet,
I came upon a number of recommendations for the JT system from Speedparts
in Sweden. This is a 3" system from turbo to tailpipe including,
optionally, a 3" downpipe and freeflow catalytic converter. It
is an aluminised steel system. Their target market is Sweden (and
their web site is in Swedish), but one of their dealers, Maptun
Control Systems, is happy to export to the rest of the world,
and the proprietor, Johnny Johannsen, is both very knowledgable on
Saab tuning and an excellent English speaker. The person who persuaded
me to buy a JT system was not Johnny, but Bill Davies, a regular participant
on TSN and a fellow UK 9000 owner. Having read my concerns, he invited
me to visit him to see and hear the JT 3" system on his 9000
CSE. I spent a morning with him and was very impressed; first by the
discreet 3" stainless steel tailpipe trim, then by the lack of
"boy racer" noise, first at idle, then when he took me for
a drive and "let 'er rip". My mind was made up and I e-mailed
Johnny at Maptun and ordered
a system. The price (at then-current exchange rates) was just under
£500 including shipping (less than the Abbott downpipe alone!).
A 3" free-flow cat accounts for around £200 of this price,
making the rest of this 3" system, including downpipe, comparable
in price to the 2.5" cat-back (no downpipe) system from Jetex.
Installing the Speedparts JT system is what the rest of this article
is about.
Finally, the verdict...
While the JT system is louder than the standard exhaust system, is is
not obtrusively so, at least to my own ear. In comparison to "boy-racer"
cars with loud stainless steel exhausts, my car simply sounds "powerful,
but understated". As far as performance is concerned, turbo lag (more of
a problem on the manual Aero, with its larger turbo) is much reduced, making
the car more responsive. Top-end power, subjectively, was also increased, but
I didn't put the car on a dynamometer, so I can't quantify the improvement.
Maptun estimate an extra 10hp. Fuel economy is at least as good, and possibly
slightly better. It is difficult to tell as I now drive the car a bit harder
to make use of the new-found responsiveness.
Time required
Around 3-4 hours.
Tools required
- 13mm spanner.
- 14mm spanner.
- 1/4" T-bar and 13mm socket.
- Copper grease (copper anti-seize compound).
- Dismantling lubricant, such as "Plus-Gas" or "Liquid Wrench".
- Have a hacksaw ready, just in case.
Additional parts required
- 6 rubber exhaust mountings. Original Saab mountings were the best I could
find.
Note that I had to fabricate lengthened mountings for the cat (see below).
Preparation
Having received my system within ten days of Maptun receiving payment, I examined
it (I received it on a Monday, and intended to install it the next Saturday).
One observation I made was that the welds securing the pipes to the silencers
(mufflers) were already showing signs of rust. This was to be expected on a
mild steel exhaust system, but these welds are the usual eventual point of failure
of an exhaust system.
I purchased an aerosol can of "Hycote" high-temperature clear lacquer
and some rust remover. I de-greased the system with washing-up liquid and water,
applied the rust remover to get rid of the rust around the welds, then rinsed
and dried the components and sprayed with the lacquer. I'm hoping this will
prolong the life of the system somewhat. However, there was little I could do
about the welds on the inside of the pipe.
I spent some time under the car and noted the hanging points under the body
and subframes. I determined that I needed six exhaust mountings (the hangers
for the old-style cat are there but hitherto unused, since later cars like mine
have the cat in the downpipe). Stainless steel hangers are included with the
JT system, but the rubber mountings are not, so I went to my local accessory
shop and bought a selection of rubber mountings that I thought might do the
job (I bought their entire stock - apparently people in the UK usually take
their car to an exhaust shop to have exhausts fitted and only buy the odd rubber
mounting when one breaks!). I subsequently replaced most of these with OEM mountings
from Saab.
Had I had the foresight, I should have sprayed all the joint fixings with dismantling
lubricant while I was under there looking at the mountings.
It is recommended to obtain new locking nuts and washers for the turbo/downpipe
flange. After having problems keeping this flange joint tight with the old nuts
that would no longer lock, I fitted new nuts later on. More about this later...
Note: Later US-spec cars require a second oxygen sensor downstream of
the catalytic converter. To accommodate non-US and earlier US models, the JT
system does not come with provision for this sensor. The sensor should be mounted
at the front (female) end of the long straight pipe. To facilitate this, a hole
should be drilled and an M18 boss welded to the pipe.
What is supplied
The photographs below were supplied by Red Aero. Many thanks for his kind permission
to reproduce them here.
Procedure
I did not have access to a lift, so had to jack up the car to gain access underneath.
If you are fortunate enough to have access to a lift, then you won't need a
jack. Many thanks to MOTest in Hemel Hempstead for finding something else to
do for a couple of minutes while I stood under the lift and took photographs,
before they continued the MOT test.
- Raise the front of the car using ramps or a jack and axle stands.
- Working underneath the car, spray the bolts at the flange at the rear of
the downpipe liberally with a dismantling lubricant such as Plus-Gas or Liquid
Wrench and leave for a while according to the instructions supplied with the
product.
Using a good-fitting 13mm ring spanner or socket, remove the bolts.
- On cars with a separate cat, unhook the rubber mountings from the hangers
on the downpipe. On cars with the cat incorporated in the downpipe (like mine),
remove the 14mm bolt from the securing bracket above the cat. Again, dismantling
lubricant may be necessary.
- Working under the bonnet, unscrew the oxygen sensor from the downpipe using
an oxygen sensor socket or a 22mm ring spanner. It should not be necessary
to disconnect the sensor wiring. On my car, the oxygen sensor is located next
to the turbo. On some earlier cars, it is located further down, just before
the downpipe passes under the engine.
Move the sensor safely out of the way.
- Using a 13mm spanner or a 13mm socket with a small T-bar, loosen and remove
the three turbo flange nuts. If using a spanner, a ring spanner is best as
the nuts are made of copper and may be damaged by an open-ended spanner if
they are tight. Recover the three washers from the studs.
- Remove the flange plate from the turbo studs and lift the end of the downpipe
away from the turbo and lower it to the ground. From underneath, rotate it
down between the engine and the subframe front member and remove it.
- Important: check all of the turbo flange studs to ensure that they
are all screwed in fully. If any are not, lock two of the old nuts onto the
stud and use these to screw it back in. I had had a persistent noise from
some time before I fitted the JT system that turned out to be caused by a
leak at this flange. The noise persisted once I fitted the new system. On
subsequent investigation, one of the studs had partially unscrewed itself
during a previous removal of the original downpipe and the nut on that stud
was not able to pull the joint tight. By the time I found the cause of the
leak (long after I had fitted the JT system), the stud had seized in that
position in the turbo and I had to remove
the turbo to have the problem rectified.
The lesson is: find and fix any loose studs immediately. A few minutes' inspection
now may save hours of effort later.
- Lower the front of the car and raise the rear of the car, again using a
jack or axle stands.
- Using dismantling lubricant once again, and a good-fitting 13mm ring spanner
or socket, remove the nuts securing the mid-section to the rear silencer.
I had no luck with these as they were so rusty the corners rounded off. Since
I was not re-using any of these parts, I cut the studs with a hacksaw.
- Unhook the rubber mountings from the intermediate silencer, lower the entire
mid-section to the ground and remove it.
- Unhook the rubber mountings from the rear silencer and remove it.
- When fitting the new system, I started with the intermediate silencer, as
this is the only component that does not rely on any of the others to determine
its final position. I positioned every other component relative to this. I
have no idea how a professional would have tackled it, but this method seemed
to make sense to me.
Hang the new intermediate silencer under the car, preferably from new rubber
hangers. The long bracket goes to the left of the car, (just out of the photo,
unfortunately).
- Pass the short curved section over the rear axle and fit it into the rear
of the intermediate silencer.
- Locate the supplied U-clamp with the hanging bracket welded to it. Use
this to clamp the tailpipe to the rear silencer, with the bracket uppermost
and pointing towards the rear. Don't bother clamping it too tightly, as the
tailpipe will probably require adjusting once everything else is in place.
- Connect the rear silencer to the short curved pipe and hang the rear of
it, via the U-clamp/bracket, from two rubber hangers.
- Lower the rear of the car and jack up the front again (the instructions
with my axle stands say not to support both ends of the car at the
same time). Support it on axle stands.
- Apply a bead of copper grease (or other suitable anti-seize compound) inside
the mouth of the exhaust downpipe. This performs the dual function of helping
the downpipe seat squarely on the turbo and, once the grease evaporates to
leave the metal particles behind, sealing the joint.
- Place the downpipe under the car and manipulate the turbo end up between
the front of the engine and the front member of the subframe. On my '96 Aero,
there was barely room to work the pipe in between the turbo flange studs and
the water pump.
- Mate the downpipe to the turbo and slide the flange plate over the studs.
Using new copper nuts, fit the nuts and washers and tighten the nuts far enough
to hold the downpipe, but not ehough to stop it from rotating freely about
the turbo flange.
- To hang the end of the downpipe, two very long rubber mountings are required.
I estimated that 75mm diameter rubber rings would have done the job, but while
my local exhaust shop normally stock such an item (used on Volvos), they were
out of stock when I needed them. I had to fabricate hangers by connecting
an extra rubber ring to each Saab hanger. I held them together by wrapping
thick steel wire around them.
Subsequently (almost a year later), I found that the (cheap) rubber rings
had cracked badly. I had a new bracket fabricated and welded on that reached
much higher and allowed the standard Saab hangers to be used.
- If fitting a catalytic converter, connect the catalytic converter to the
rear of the downpipe and fit the band clamp/hanger supplied. Note that the
hanging bracket should be positioned on the underside of the clamp,
not on top, even though this makes it look upside-down. Hang the cat and downpipe
from the hangers on the car body. Note that the original position, as shown
in the photograph, is rather high. I subsequently re-aligned the cat and allowed
it to hang lower (the bracket engaged in the lowest position on the rubber
hangers).This also allowed the recommended 3" clearance between the cat
and the body of the car.
If not fitting a catalytic converter, substitute the cat bypass pipe for the
catalytic converter in the paragraph above.
- Insert the main pipe into the intermediate silencer.
If not fitting a catalytic converter, insert the end of the cat bypass pipe
into the end of the main pipe.
If fitting a catalytic converter, hold the end of the main pipe level with
the outlet of the catalytic converter (both female ends) and measure the length
of pipe that would be necessary to fit into both the main pipe and the cat.
Cut this length off the cat bypass pipe and insert this into both the main
pipe and the cat.
- To avoid leaks, I wrapped all joints (except those on the cat) with self-adhesive
aluminium tape, sold in my local parts store (Halfords) as "Exhaust Repair
Tape". However, the accompanying instructions state that it is not suitable
for use on catalytic converters.
- Fit the remaining U-clamps to those joints not yet clamped. Carefully aligning
the system so it hangs level and it avoids touching any bodywork or suspension
components, tighten up each of the clamps. Don't tighten up the tailpipe yet.
- Working in the engine bay, tighten the turbo flange nuts evenly. Access
to these will be more restricted than before, especially to the rear nut.
To reach the rear nut, I used a 1/4" drive sliding T-bar with a 13mm
socket. The official torque is 25Nm (18lbft),
but I couldn't get a torque wrench onto any of the nuts.
One thing to look out for is that the downpipe comes very close to the turbo
oil and coolant pipes. On my Aero, I found later that the downipe was pressing
against the turbo oil supply and return pipes. This must be avoided as the
pipes will eventually wear through, with disastrous consequences. My solution
(long after everything had been fitted) was to relocate the pipes slightly
by carefully levering them away from the downpipe. A better solution would
be to place something temporarily between the downpipe and the oil pipes to
act as a spacer (5mm or 1/4" should be enough) until the system has been aligned
and tightened up, not forgetting to remove the spacer before starting the
engine. This may not be a problem with cars fitted with the Garrett turbos,
but I have no experience of fitting the JT system to those cars.
- Apply copper grease (or other suitable anti-seize compound) to the threads
of the oxygen sensor and fit it to the downpipe. The torque setting is 55Nm
(41lbft).
- A number of people have recommended fabricating a bracket to fix the front
part of the downpipe (in fron tof the flexible joint) rigidly to the engine
with the aim of avoiding stress at the turbo flange joint. I didn't do this,
but my original cat/downpipe was fixed rigidly to a bracket at the rear of
the engine. I intend to fix the downpipe rigidly to the engine in the near
future.
- Lower the front of the car.
- Line up the tailpipe for best cosmetic effect and tighten the U-bolt clamping
it to the rear silencer.
- Start the engine and allow it to idle while looking for leaks. Leave the
engine idling until normal temperature is reached, to allow the anti-seize
compound at the turbo flange to harden.
- Allow the system to cool and re-tighten the turbo flange nuts.
- Adjust the basic boost pressure,
as the lower back-pressure of the JT exhaust system will lower the basic boost
pressure. The basic boost pressure on my Aero prior to fitting the JT system
was 0.48 bar (7PSI), which is just at the top end of the spec. After fitting
the JT system, it was 0.38 bar (5.5PSI), which is well below spec. I adjusted
it back up to around 0.48 bar.
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