The purpose of this article is to give 240 Turbo owners an organized modifications plan for the B21FT engine. With the stages, we have arranged the modifications in a safe and comprehensive manner, so you get good results without the trauma experienced by the pioneers who learned the hard way.

Every stage is a preparation for the subsequent stages. For instance, you could skip the first four stages and go directly to raising the boost to 13 psi. This might or might not yield desirable results in all cases since I can't guarantee that your engine has the needed preparation to avoid detonation, fuel starvation, overheating, accelerated wear, inhaling oil into the intake, and in the end, total engine failure.
If your car is completely stock, you have to make sure it performs at its best in stock form BEFORE doing any modifications; that's why we have included a "STAGE O".

Keep in mind that a B21FT running 16 psi of boost has an effective compression ratio of about 15.5:1 at that boost level. So in order to avoid engine failure we have to ensure the following:

The first stages are the simplest and least expensive. Things get somewhat steep over about 200 HP, as Philip Bradley puts it: "The first 50 hp costs $250. The next 50 hp costs $2500. It really is not worth chasing unless you are a little crazy". Then it sounds like we have quite a few crazies in this club!

This article is still a rough draft, comments, modifications, or additions are HIGHLY welcome.

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" is boost.

• 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 them off.


• 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 do.


• 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 seals failure.


• 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 yours truly)

• Modify the airbox intake tract: see Jon Glommen´s Airbox Modification article


• 2.5-3" catalytic converter: if laws allow..... delete the thing from the system!


• 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..

WARNING: 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.

• 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.

• 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.

• 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.

• B23/ B230 EFI Intake manifold and throttle body: better airflow, it has tunned runners.


• "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: :amorales@chiriqui.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.

• 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 applications.


• 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 control systems.

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 APC brain.

• 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.