Nothing
on a stock car is top-of-the-line... everything could use improvement. Finding
flaws in the car's design is valuable horsepower just waiting to be unleashed.
In that respect, the Probe's exhaust system is a virtual goldmine. The conservatively
build exhaust system on the Probe is good at muffling the exhaust and keeping
the Probe's price tag low, but extremely bad at keeping the exhaust gases flowing
smoothly. Ford is also restricted by Environmental Protection Agency guidelines
on the overall design of the exhaust system since the Probe is a high production
car. The EPA is not concerned with horsepower and torque, but rather the effects
of your car's exhaust gases on the world around us. Aftermarket sources for
exhaust products don't have any of the restrictions Ford has, giving us a way
to give our cars the exhaust systems they need. The downside is we do have local
state environment and emission codes that we must adhere to in order to keep
our car street legal. Although most companies keep their products within these
codes, it's very important that you check all laws in your state before upgrading
any part of your car's exhaust. I don't condone anyone altering their vehicles
that may infringe on any federal or state environmental codes. If anyone has
a question of why these codes exist, take a look at this CNN
article.
The main
thing to remember is that the hotter the exhaust gases are, the more velocity
they have. Oversized exhaust pipes and thin material can cool exhaust gases,
slowing down flow and causing more backpressure.
This
section is for performance exhaust systems that yield more power, not more sound.
I see a lot of people (mostly kids) buying exhaust parts and mufflers based
on how 'loud' they are. This is totally absurd and this site will never promote
that type of amateurish thinking. It's like buying a steak based on how the
cow moos. Personally I'm sick of people upgrading their cars trying to make
them louder... they're loud, obnoxious, and I don't even need to see the car
to hate it when I hear one go by.
Key
Pros:
The benefits of a particular upgrade.
Cons: The down side of a particular upgrade.
Cost: Approximate price range based on numerous quotes and price sheets.
HP Gains: Estimated increase in horsepower you can expect from a
particular upgrade. Not necessarily peak horsepower.
Manufacturers: Examples of particular companies that sell a particular
upgrade.
Availability: Which Probes the upgrade is for.
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Cat-Back
Systems |
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Cat-back
systems consist of all exhaust parts behind the catalytic converter. Sold
as kits, these usually consist of larger, mandrel bent piping, high-flow
resonator, and a performance muffler. These kits are usually direct fit,
easy to install modifications that significantly increase power, especially
at high rpm.
In
1996, the Probe received a minor exhaust change. The new exhaust was designed
for OBD-II. If you try to use a '93-'95 cat-back system, you'll come up
about 6" short. To get around this, you'll need to have a 6"
piece of pipe custom made for the gap. Any muffler shop can do this.
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| Personal
Experience: I installed a Borla turbo-back
exhaust system on my '92 GT. The system was completely stainless steel and
mandrel bent, with a Borla dual intercooled tipped muffler. Exhaust tone
is louder and deeper without being obnoxious and with no interior droning.
There was almost no low range torque loss and had considerable mid and high
range power improvements with faster turbo spool up. |
| Pros:
Greater decrease in backpressure, more horsepower. |
| Cons:
Increased exhaust sound, possible state emissions
codes. |
| Cost:
$150-$700 |
| HP
Gain: 10-15hp |
|
Manufacturers:
Borla, Bosal, Brullen, GReddy, HKS, PaceSetter
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Availability:
All, '96 & '97s may require modifications |
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Catalytic
Converters |
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The
catalytic converter is a part of the exhaust system that converts exhaust
gases into carbon dioxide and water vapor through chemical reaction. Stock
catalytic converters are designed for function with a budget in mind, not
performance. A high flow catalytic converter can add a few horsepower while
staying within state emission codes and federal EPA laws. This may only
appeal to people looking to get every bit of horsepower they can from their
cars since it's one of the highest cost per horsepower modifications available. |
| Personal
Experience: Currently looking into. |
| Pros:
Decreased backpressure, some extra horsepower. |
| Cons:
None. |
| Cost:
$100-$250 |
| HP
Gain: 2-3hp |
|
Manufacturers:
Random Technology |
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Availability:
All |
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Downpipes |
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The
downpipe is the piece of exhaust pipe that connects between the exhaust
manifold or turbo and the catalytic converter on 4 cylinder engines. V6s
instead have Y-pipes under the engine connecting the two manifold sets to
the catalytic converter. This is the most restrictive part of the exhaust
system. The downpipe, which is less than 2" in diameter, is press bent
and includes numerous 'steps' from welding material that lessen the pipe
diameter even more.
Since
there are only a few direct fit replacement downpipes, the best thing
to do is go to a muffler shop and have one custom made. The main point
to remember is to have the pipe mandrel bent. To keep the gases hot and
engine compartment cool, ceramic coating is highly recommended. Most aftermarket
headers include the downpipe.
|
| Personal
Experience: The exhaust system for my '92 GT
included everything from the turbo to the muffler. The downpipe was much
wider then stock and made a big difference in turbo spool up. When I purchased
the Hotshot headers for my '89 LX, the headers included a mandrel bent downpipe. |
| Pros:
Greater decrease in backpressure, more horsepower. |
| Cons:
Possible drop in low end torque. |
| Cost:
$100-$300 |
| HP
Gain: 5hp |
|
Manufacturers:
Bosal |
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Availability:
1st Generation |
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Exhaust
Pipes |
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When
upgrading your exhaust system, it's important to remember that the hotter
the exhaust gases are, the more velocity they will have when flowing through
and out of your exhaust system. When it comes to the exhaust pipes, unlike
what most people think, bigger necessarily isn't better. On a stock Probe,
3" exhaust pipes will reduce the backpressure over, but will allow
the exhaust gases to cool, slowing overall flow. For up to 150hp, 2-1/4"
pipes would be sufficient. For engines from 150hp to about 250hp, 2-1/2",
and for engines from 250hp-300hp, 2-3/4"should be fine. If you're not
too worried about low end torque, you can add a 1/4", but any
bigger could drastically reduce low end torque.
The
stock exhaust pipes on the Probes are press bent. Although cheaper, this
method will cause increased backpressure in the exhaust system. Any pipes
you get should be mandrel bent to keep exhaust gases flowing smoothly.
|
| Personal
Experience: All exhaust pipes on my '92 GT
have been upgraded. My '89 LX's exhaust pipes will be replaced with custom
made pipes. |
| Pros:
Greater decrease in backpressure, more horsepower. |
| Cons:
Possible drop in low end torque. |
| Cost:
$100-$500 |
| HP
Gain: 5hp |
|
Manufacturers:
Borla, GReddy, HKS, PaceSetter |
| |
Availability:
All, '96 & '97s may require modifications |
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Headers |
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Exhaust
headers offer the best improvement along the exhaust system. When the exhaust
valves open and release the burned fuel/air mixture from the cylinder, the
exhaust gases are usually called a pulse. This pulse goes through the manifold,
into a collector where it meets the pulses from the other cylinders. The
collector simply forces all the pulses into one pipe where they travel through
the exhaust system and out the muffler. Headers can improve this flow in
three ways:
- The
pipes are mandrel bent to allow smoother, unobstructed travel of the
pulses, reducing backpressure.
- Each
of the header's pipes have a calculated length to allow one pulse at
a time to enter the collector, instead of all being forced together.
As each pulse enters the collector, it creates a vacuum behind it which
effectively pulls the next pulse smoothly along behind it. This allows
for smoother exhaust flow decreasing backpressure.
- Most
headers today are ceramic coated. This keeps the exhaust gases hot,
allowing the gases to flow faster, as well as keeping the engine compartment
cooler, keeping intake temperatures at a minimum. If you have a set
of headers that aren't ceramic coated, it's highly recommended that
you have them coated.
|
| Personal
Experience: I bought Hotshot headers for my
LX. Although I haven't tested them out yet (engine's still being rebuilt),
the weight difference alone is worth a note... the stock manifold with downpipe
weights a hefty 26 lbs. The HotShot headers, on the other hand, with the
included downpipe weights only 9 lbs... a drop of 17 lbs.
The
only problems I can see with the HotShot headers has to do with installation.
First of all, one of the bolt holes were off centered, which I had to
use a Dremil to fix. Not very impressive. Also, with the air conditioning
compressor in the way, removing the stock manifold may be a bit difficult.
|
| Pros:
Increased horsepower. |
| Cons:
Possible drop in low end torque, possible state emissions
codes. |
| Cost:
$150-$600 |
| HP
Gain: 10-15hp |
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Manufacturers:
Bosal, Brospeed, Hotshot, PaceSetter |
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Availability:
1st gen 4-cyl non-turbo, all 2nd gen |
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Hollowed
Catalytic Converters/Straight Pipes |
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The
catalytic converter is a part of the exhaust system that converts exhaust
gases into carbon dioxide and water vapor through chemical reaction. Replacing
the it with a straight pipe or removing the inner material from the device
will decrease the backpressure in the exhaust system and add a few extra
horsepower. Although a seemingly easy way to boost horsepower, doing so
may put you at risk of state emission code violations. In New York, for
instance, there's a $1500 fine for removing or hollowing the catalytic converter.
I don't know which states, if not all of them, have laws pertaining to catalytic
converters. Check local laws where you live before attempting this. Your
car will not pass state inspections where emission tests are required.
Replacing
the cat with a straight pipe is the best method. It provides a better
exhaust flow and frees you up of the extra weight of the cat... they usually
weigh 15-20 lbs! All you would need is a 2-1/4" pipe about 18"
long, which you could get from a local muffler shop for a small price.
The only drawback of this method is that the missing catalytic converter
is very apparent.
Hollowing
the cat is the cheapest method... and sneakiest. All you would need to
do is remove the cat, and break out the brittle inner material. This can
be done with a long screwdriver or tool. The best part of this method
is that the shell is still on. You can't tell the catalytic converter
isn't functioning unless you take an emissions test. A good method for
states like Texas that only look to see if the cat is there.
|
| Personal
Experience: Right after I got home from getting
my LX inspected, I hollowed out the cat using a drill with a long drill
bit, and a screwdriver. There are 3 sections of asbestos type material locked
into place by flat metal rings. I drilled straight through the cat from
one end to the other then used the screwdriver to break the rest out. The
metal rings could then be worked out with the screwdriver or pliers. Barely
noticeable power increase, but the deeper exhaust sounds tell me there's
less backpressure.
When
I got the GT I swapped the LX's cat for the GT's. It had a very little
bit more noticeable power then when it was on the LX. I'm currently looking
into a high flow catalytic converter to make everything legal.
|
| Pros:
Decreased backpressure, extra horsepower. |
| Cons:
Legality, possible state emissions codes. |
| Cost:
$0-$25 |
| HP
Gain: 5hp |
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Manufacturers:
None |
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Availability:
All |
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Performance
Mufflers |
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The
muffler, obviously, muffles the sound of the exhaust gases coming from the
engine. The stock muffler on the Probe is badly designed for consistent
exhaust flow, since its number one priority is to tone down the sound, while
staying inexpensive. Performance mufflers use better sound absorbing materials
along with a better flow design to lessen backpressure in the exhaust system,
while keeping the noise level at a tolerable rate. There are a wide variety
of performance mufflers on the market, ranging anywhere from a decent one
from Midas, to a top-of-the-line one from Borla... the only barrier being
cost.
When
purchasing a muffler, remember that there is a fine line between a deep
performance exhaust tone, and an annoying, obnoxious exhaust racket.
|
| Personal
Experience: The exhaust system I installed
on my '92 GT included a Borla muffler. This muffler is perfect, since it
had dual intercooled tips rather then one large tip, which I strongly prefer.
These tips are perfectly sized since they are big enough for smooth exhaust
flow, but not so big that they don't look like they 'could' be stock.
I
installed my GT's stock muffler on my '89 LX for an improved flow, but
with a stock look.
|
| Pros:
Decreased backpressure, some extra horsepower. |
| Cons:
Increased exhaust sound, possible state vehicle codes. |
| Cost:
$100-$700 |
| HP
Gain: 3-5hp |
|
Manufacturers:
Borla, Brullen, Dynomax, GReddy, HKS, PaceSetter,
Remus |
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Availability:
All |
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