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The performance chip is the "best bang for the buck"
for $250, you cannot go wrong. 30 min later you will have
between 15 - 40 more Hp under the hood.
The OEM chips are programmed to work with the weaker gas octane
and to reduce fuel consumption.
Changing the chip will raise the rev limit and remove the
top speed limit.
BmwE34.net recommendation: Mark D'Sylva's Chip.
HP gains: 15
to 40 Hp
Avg. Price:
$250.
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2- Air filters and
cold air boxes (K@N and others) |
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There is a big controversy about replacement filters. The
E34 air box is well designed and isn't restrictive. It shields
the filter well against the warm air of the engine.
Changing the filter will make the exhaust note deeper. Maybe
a little increase of acceleration and it will be the last
time that you'll buy an air filter (if you clean and oil it).
I must warn you that some people think that the K&N type filters
do not filter the air as good as the stock filter and might
harm your engine.
BmwE34.net recommendation: If you
really have to, get a K&N filter replacement and remember
to clean it.
HP gains: -3
to 0.5Hp (yes it is a minus 3)
Avg. Price:
$40 (filter) - 150 (cold air).
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3- "Performance" ignition wires
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Pure waste of money, maybe you can buy them if you want a
touch of colour in the engine compartments. Changing the well
designed OEM wires with "performance" ones is asking
for trouble. Your engine might run worse.
BmwE34.net recommendation: Stick
to OEM.
HP gains: 0
Hp
Avg. Price:
$170.
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4- Sport exhausts
(without headers) |
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Sorry, but you don't have a Honda. There is little to no
gain by changing the exhaust system.
The change could be justified if your exhaust is in bad shape
or if you want a deeper note.
As I already said: " no engine makes more power with
a muffler than an open header exhaust. " But I strongly
discourage anyone to do that.
The muffler out of the way, what about the catalytic converter?
Again, the BMW cat. is non restrictive. And it is illegal
to remove the catalytic converter.
BMW designed the exhaust very well, keep your money for other
upgrades. Adding a cat after an emptied cat on my E28 didn't
increase the power at all....
BmwE34.net recommendation: get nice
chrome tips instead, or get stainless steel if you keep the
E34/E32 for ever.
HP gains: 0
to 3hp
Avg. Price:
from $200 up.
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5- Sport exhaust headers
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Headers makes the exhaust gases come together more smoothly
than stock before entering the cat.
They can be expensive (up to $1000), but there is still a
couple of RD headers on ebay sometimes.
BmwE34.net recommendation: Definitively
get it if you have a modified intake with a polished cylinder
head.
HP gains: 7
to 30Hp (with forced admission)
Avg. Price:
from 600 up.
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6- Bigger throttle body |
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The Power principle is to enter as much (cold) air as possible
into the engine. So you could think that a bigger throttle
body should help right? Yes, only if you have a MAF (see below),
else it is a waste of money because the Air Flow Meter is
very restrictive.
Forget about the Dinan and other (BMP) overpriced throttle
bodies, take yours to a local auto machine shop. They can
do as good as a job as the professional tuners for way less
money.
Check also in Bimmer magazine: Ed Mazula's ad (CA) (800)
792-9338. Next day service.
BmwE34.net recommendation: Definitively
get it if you have a modified intake with a polished cylinder
head.
HP gains: 0
to 1.5?Hp (with MAF)
Avg. Price:
from $200 up.
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7- Mass Air Flow Meter (MAF) |
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This is another interesting upgrade. The E34 MAF (at least
in the M30 engine) is quite restrictive. The stock Air Flow
Meter (AFM) is the large metal box on top of the engine valve
cover. One end takes the air from the air box, the other is
connected the the throttle body.
The principle is a metal door monitoring the flow through
the AFM. As you can imagine, this setup is very restrictive.
The MAF uses a heated wire to monitor the flow through a tube
which almost create no restriction. Only problem is the price:
$1000 for split second and $500 for Modern Performance.
BmwE34.net recommendation: A good
power upgrade (I am working on a setup for less than $400).
HP gains: 5
to 10Hp
Avg. Price:
from $400 up.
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8- Fuel pressure regulator / Bigger injectors |
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This is a great upgrade if you have added a turbo or supercharger
to your car. Or else, you need a highly modified engine to
gain from this upgrade.
Same comments for bigger injectors.
BmwE34.net recommendation: Most
of us don't need that.
HP gains: 0
to 2?Hp
Avg. Price:
from $170 up.
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9- Ported intake manifold |
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This is a great upgrade, a must do if you have to remove
the intake to change the gasket or rebuild the cylinder head.
The intake is restricted and doesn't match the holes in the
cylinder head.
This upgrade + headers is a great combo. This will give you
some extra power in the upper RPM range.
Don't go Dinan, as this is waste of money. Get a local shop
to modify it for you.
BmwE34.net recommendation: Easy
and cheap modification.
HP gains: 0
to 2?Hp
Avg. Price:
from $100 up.
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10- Performance camshafts |
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This isn't an easy upgrade, but perfect if you are having
some work done on your cylinder head. There is a couple of
different camshaft profiles you can choose from. The Schrick
Cam delivers a noticeable increase in power, especially above
3000 rpm where the engine seems to come on cam. This is an
improvement over the standard E34 engine which seems to come
on cam at 3400 rpm. And of course, above 4000 rpm's the Cam
really makes itself felt (high performance springs and retainers
are recommended).
BmwE34.net recommendation: Go for
it if you have the extra cash.
HP gains: 5
to 10Hp
Avg. Price:
from $400 up.
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11- Different differential gear ratio |
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This isn't a cheap upgrade, and not an easy one. A used differential
cost between $500 and $900 and you still have to install it
on your car...
For example: a 3.91LSD diff. from a 525iA installed to replace
the stock 3.46LSD in the 535i will give you a mileage loss
of about 2/3 mpg on the highway. But it is more than justified
by the drastic increase in acceleration.
The 535i 3.46 doesn't seem to fit the '95 525 5-speed.
BmwE34.net recommendation: Great
upgrade for acceleration increase.
HP gains: 0
to ?Hp
Avg. Price:
from $500 up.
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Model
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OEM ratio
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Suggested ratio
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525i M20 89-91
5 speed |
3.73
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4.10
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525i M20 89-91
Automatic |
4.10
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4.45
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| 525i M50 92-95 5 speed |
3.23
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3.46
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| 525i M50 92-95 Automatic |
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| 535i 5 speed |
3.46
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3.73 or 3.91
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| 535i ->6/90 Automatic |
3.91
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4.27
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| 535i 7/90-> Automatic |
4.27
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4.45
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| 530i 5 speed (M60) |
3.07
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3.46
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| 530i Automatic (M60) |
3.15
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3.46
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| 530i 5 speed (M30) |
3.64
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3.91
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| 540i ->3/04 |
2.93
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3.25
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| 540i 4/94-> |
2.81
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3.25
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| M5 3.6 ->7/91 |
3.91
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4.10
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| M5 3.6 7/91-> |
3.73
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4.10
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12- Performance flywheel |
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This is another great upgrade because the dual mass flywheel
in your E34 is probably making some weird noise each time
you shut the car off.
A lighter rotating mass will give your E34 better acceleration
and faster throttle response. The new flywheel might affect
your idle.
BmwE34.net recommendation: Perfect
if you have your clutch changed.
HP gains: 0
to 2?Hp
Avg. Price:
from $600up.
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Now, what is left?
At reasonable cost, not much... Modification of the Automatic
Transmission to a higher stall Torque Converter. And if that's
not enough, and you have money left, then look at either an
M5 Engine Conversion or Supercharger/Turbocharger installation,
or a Supercharged/Turbocharged M5.
Me... I keep dreaming of a BMW E34 M5 Bi-turbo....
The following results are from a Dyno Test on an E34 535i
with 3.73 Diff Ratio, Free Flow Exhaust, K&N Air Filter
and a Jim.C. Chip.
The test results:
Maximum HP: Up to 229HP (171kW) from 208HP (155kW)
Maximum Torque: Up to 243lb/ft (332Nm) from 223lb/ft (305Nm)
Information from Richard Nott
Some information about exhaust systems
from Matt Evans:
no engine makes more power with a muffler than an open header
exhaust.
This could be construed as saying mufflers never help power.
I believe this could be more accurately put: if you just lopped
off your exhaust after the headers, you would very likely
get a torque _and_ power decrease.
A subtle amount of backpressure of course helps torque (while
too much limits top end power, of course). However, just as
header length and tuning helps with gas scavenging and optimizing
power at a certain rev range, the over all length of the system
is an important consideration in exhaust design. Simply replacing
the well designed OEM exhaust system with a random cobbling
of big mandrel bent pipes is very unlikely to give good results.
The best combination will be properly tuned headers, and the
right collector/crossover pipes, and finally the mufflers/horns/what
have you that bring the system to the correct total length.
Optimizing the entire system for weight, cost, performance,
sound, and space requirements is obviously tricky. I don't
know even a faction of the fluid dynamics required to do even
an amateurish job at improving upon the BMW design. Most people
don't. The only significant improvement on the stock BMW systems
are going to properly designed headers in place of the EPA
friendly manifolds, or switching to an exhaust of similar
design and layout, but made of lighter materials, as you point
out.
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