STAGED PERFORMANCE MODIFICATIONS FOR 240's
WARNING: excessive turbo boost combined with lean
mixtures, bad fuel and wrong ignition timing can cause major engine damage very
quickly. The Volvo B21FT engine does not have a fuel system with a lot of extra
capacity to support great amounts of horsepower without leanning out (lean mixtures
mean quick death to a turbo engine). Another weak link is the ignition retard
system; it does NOT have a knock sensor to retard ignition timing if detonation
occurs. If you can't detect light detonation by ear, don´t use high octane
gas, or are not sure about the air/fuel ratio at high boost, do not attempt
to raise turbo boost. Remember: "IF YOU GRAB A TIGER BY IT'S TAIL, YOU'D
BETTER KNOW WHAT THE HELL YOU ARE DOING!" In this case the "tiger"
STAGE 0 (165HP) - "Tune up".
This stage covers regular maintenance stuff, if you have taken great care of your
turbo motor, this stage will be the easiest!
- Perform a leak-down test: an engine with more than 10% leakeage needs to
be rebuilt, top performance achieved below 3%. If you need to rebuild the
engine, consider a B23FT or ´90-on B230FT bottom-end with custom 7.5-8.0:1
compression ratio for more displacement. If your goal is "extreme performance"
(way more than 250 HP, using a stronger transmission), then your first stage
should be a building super strong (maybe a 2500 cc. " monster")
motor with more displacement. Volvo made the parts to withstand 400 HP, you
only need to get custom low compression forged pistons.
- Replace plugs, wires, cap and rotor: NGK BP7ES work very well. A set of
high quality low resistance wires are a good investment. MSD wires are good
although the distributor boots need to be replaced with straight ones.
- Index spark plugs (optional)
- Adjust. initial advance at 12° BTDC.
- Check the boost retard diaphragm operation by gently applying some pressure
from say a bike pump and watch for retard at timing marks. Besides make sure
to use hose clamps for these little "vaccum" hoses, boost can blow
- Clean the fuel injectors: if you have more than 100 K miles and haven´t
used very good fuel, it´s a good idea to have the injectors professionally
cleaned or replaced. In some cases a good injector cleaner like Techron will
- Clean in-tank screen and ensure both fuel pumps are working correctly (no
noises or groans and at least 12 volts at the main pump)
- Remove intercooler and drain any condensed oil out
- Upgrade in-tank pump to late model or replacement high volume unit: if your
in-tank pump is weak, get a late model unit when replacing it.
- Backflush fuel pump internal screen: only if you are having fuel delivery
problems. The system should flow about 1.8 liters per minute through the return
line in the flow test..
- Check/ clean/ replace oil vapor trap: this is very important since a clogged
oil trap will create elevated crankcase pressures that will lead to engine
- Replace the 197°F thermostat with a 180°F unit: the lower temp.
will help the engine stay out of detonation.
- Replace the air cleaner: K&N recently launched the B21FT air filter
to the US market.
- Replace the fuel filter
- Check and adjust turbo boost pressure (10.5 psi over 4000 RPM)
- Use premium unleaded fuel only (92+ octane)
- Synthetic oils everywhere highly recomended (10W30 winter / 15W50 summer)
- Install a calibrated boost gauge. (The VDO cockpit is a drop-in replacement)
- Install an Air/Fuel ratio meter. (The Cyberdyne A/F meter being tested by
STAGE I (180 HP) - "Airbox modification and Free flow exhaust system".
- Modify the airbox intake tract: see Jon Glommen´s Airbox
- 2.5-3" catalytic converter: if laws allow..... delete the thing from
- 2.5-3" cat-back system with free flow muffler: a 2.5 inch system and
good performance muffler (Walker Dynomax, UltraFlo, Flowmaster, etc) is good
for almost 300 HP. Remember that turbo engines need very little muffling to
be quiet, straight-through designs work very well. You can even use a 3"
muffler even if your exhaust system is only 2.5 inch..
Power gain: 15-20 HP.
do not proceed to the following stages if you are
unsure about the proper Air/Fuel ratios and detonation recognition. An A/F meter
and 95+ octane fuel highly recommended (even higher required under hot weather).
Remember that the ignition system in the B21FT is "deaf"(no knock control
whatsoever) . Please read this: DETONATION.
STAGE III (195HP) - "Boost control device".
Here is where things get interesting and very delicate. If your engine is not
prepared for more boost, you are in for serious engine damage. Detonation and
increased exhaust gas temperatures will eat up your engine in no time. Remember,
the B21FT DOES NOT have safety systems to avoid detonation. Be prepared
to listen carefully for detonation when full boost arrives (specially between
3000 and 4000 RPM). If you hear any pinging, back off that gas pedal NOW!
Also remember that weather conditions vary the detonation threshold, cooler weather
being much better than hot weather. For example, even if your engine runs excellent
in 60 °F weather, it might ping badly in 90 + °F weather.
If you would like the engine to take care of itself, there is a safety system
that you could install called APC. This Saab system listens for detonation and
regulates boost accordingly. It allows the maximum boost the engine will take
without pinging. For information on this system, visit the Volvo
- Bypass boost control solenoid
- Set boost to 13 psi (intercooled models only)
- Extra fuel: you could use the cold start injector to spray fuel after 10
psi using a pressure switch. The porpuse is to richen the mixture and lower
the detonation threshold.
Power gain: 15 HP
STAGE IV (200HP) - "Ignition improvement".
- Perf. ignition system: our members have tried them all, and the MSD systems
are the favorite. The MSD 6AL (RPM limiter) is nice, but the MSD 6 BTM is
the nicest of all with the adjustable timing retard proportional to boost.
Power gain: 5 HP
STAGE V (200HP) - "Performance Clutch".
If your stock clutch is just a bit tired, it´ll let you know as soon as
you hit 200 HP. Since the M46 transmission won´t hold up at over 250 HP,
there is no point in installing a super strong clutch with this transmission,
a slipping clutch might help you save the tranny acting as a torque regulator.
- Centerforce I clutch: a stronger clutch is not recomended because the M46
needs a "torque regulator" to help dampen and survive shock loads
under agressive driving.
- Modified engine mounts: see Adam Smith´s engine
mounts modification article.
STAGE VI (220 HP) -"Perf. intake, exhaust and cam".
Notice that we are still at 13 psi, at this stage is where bolt-ons end. However,
you can skip this stage is you wish to keep raising boost and managing the fuel
and ignition curves.
This stage concentrated on improving Volumetric Efficiency,that will let
your engine make more power at any boost level and rev beyond 6000 RPM with
ease. You need to remove the head to install a better head gasket and maybe o-ring
the block for extra reliability. While you are at it, a valve job is a wise decision.
- B23/ B230 EFI Intake manifold and throttle body: better airflow, it has
- "A" grind cam and Volvo double springs: this cam can only be found
in the B21/B23A and B23/B230ET engines that were never sold in the US. This
cam will change your engine´s personality. It broadens the power band
by about 1000 RPM, making the engine rev easily to 6500 RPM. It makes the
transition from first to second gear (M46 with awfully wide ratios) much better..
Low end torque and idle quality will suffer, but not much (it idles at 17"
of vaccum). Advancing the cam 4° helps the low-end torque with almost
no sacrifice to the top-end.
We are not saying that this is the best cam for the B21FT, just a cam that
we have found to work well. We are still researching for new alternatives
such as the V, VX, VX3, T5, and custom grinds. If you have any experience
and real world data on any performance cam, please drop me a note at: :email@example.com
- ´90- on B230 exhaust manifold (Part #: 3514440): this manifold needs
to be machined for use with the Garret T3 Turbo style turbine housing.
- High performance head gasket: the Felpro gasket has been reported as being
a good performer. The OEM gasket is very good as well, however, get the
early non-TTY head bolts for extra torque capacity. Group 6 sells a copper
head gasket that is hard to seal with less than immaculate mating surfaces
and without weird sealants. The best option for ultra high boost (over 18
psi) is block o-ringing. If you can rent the Iskenderian tool, the block doesn´t
need to be removed from the engine. A stock gasket and o-ringed block will
hold 25+ psi of boost.
- Electric main cooling fans: this engine, with the thick A/C-condenser/intercooler/radiator
sandwich, needs a very powerfull 16 inch puller fan PLUS a 12 inch pusher
to work well. A higher output alternator is needed to power these fans
- Electronic 5th injector system: your stock CIS injection won´t
supply enough fuel for 215 HP. Turbobricks member, Denis L´Espérance,
is developing a low-cost, high performance, boost and RPM sensitive injector
controller with capacity for 4 extra injectors. HKS, Greddy, Select Sales
and others have AIC´s from $320-800. As a cheap alternative, you can
use the cold start injector or a small electronic injector (150 cc./min) placed
some 10 inches before the throttle body (to aid fuel atomization). You could
even install more than one using a separate pressure switch for each one of
the injectors. Say, one turns on at 10 psi and the other at 15 psi.
Power gain: 20 HP
STAGE VII (240 HP) - "High boost".
- Compressor bypass valve: this device will reduce turbo lag between shifts
and protect your turbo by avoiding compressor surge. 700 series turbos use
bypass valves, that´s one alternative. The aftermarket sells a wide
variety of these valves, some of them vent surge pressure to the atmosphere
making trick sounds (Greedy, HKS, etc). A good source for new Bosch bypass
valves is your local Saab dealer. You can install two of these in high power
- ADJUST FUEL CUT OUT SWITCH TO 19 PSI: if you don´t have installed
the APC system, this is your only safety device other than your sharp ears
and right foot.
- Set boost to 16-17 psi
- Water injection: an optional safety device.
- Octane booster or high quality gasoline.
TUNING: unless you have the APC system, you need to carefully tailor your
fuel and ignition curves and use high octane fuel to avoid the most feared enemy
of any turbocharged engine: detonation. First, you must provide a rich mixture under boost at any RPM. Remember
that a right mixture at 5000 RPM could lean out at 6500. A rich mixture is your
first step towards detonation prevention. How rich? As rich as it can run without
hesitation; in my experience, about 930-950 mV. of O2 sensor output (Bosch 3-wire).
Second, set your ignition timing at 10-12° BTDC if you don´t have
any aftermarket boost-retard system. This yields about 26-28° of total advance
over 3000 RPM and any boost condition, a bit too much under hot weather,
13+ psi and pump gas. Because of this, use power/boost with caution under hot
weather and when using pump gas, if you hear any suspicious noise under the
hood, back off the gas now!
Another thing to remember: adjust your maximum boost in 4th gear (going uphill
preferably) to avoid over-boosting due to boost creep with the pneumatic boost
Again, you can install an APC system and enjoy the peace of mind. It´ll
give you max. possible boost under the prevailing conditions. It´s like
having a competitive tuner under the hood adjusting your boost presure, keeping
the engine at the edge of detonation. You rest and watch how changes in fuel
quality, timing advance, ambient air temp, A/F ratios, etc, move the detonation
threshold up and down just by looking at the boost pressure provided by the
Power gain: 15-20 HP
STAGE VIII (250HP) - "Upgraded turbo".
Our last real stage, we have cars with this setup and it works very well. An engine
prepared up to stage VIII specifications can use higher boost given enough
high octane fuel through the aditional electronic injectors. The weak link at
this point is the M46 transmission, it won´t survive at over 250 HP. The
options are the Toyota Supra and Getrag transmissions with a Centerforce Dual
Friction clutch, these are strong enough for 400 HP. For more datails, read Jon
Glommen´s transmission swap article.
- Garret T3, Trim-60 compressor and 0.63 A/R Turbine housing OR T-3/T04 watercooled
hybrid turbo (H3-trim compressor & 0.63 A/R )
- Lower boost to 16 psi.
- 3" downpipe.
Power gain: 10 HP.
Contributed by: Angel Morales with Jon Glommen, and Anthony Hyde.