The 740 and 940 turbos can be picked up for as little as 500GBP . For this price you can expect full leather interior, no rust, well looked after and a carefully driven model with service history and for a couple of grand more you can get 500bhp.
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Volvo also made the T5 so why hasn't it been mentioned? Well it's front wheel drive and with 250bhp, its a reaching the limit of traction. The 740 and 940 turbos are rear wheel drive so have no problem putting the power done and as a brucy bonus, can be taken drifting. Another aspect is the image, the T5 is though of as a bit cool. But how cool is it to blow by Imprezas on the straights and to leave BMW M3s standing from the lights?
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Volvo 740/940 Turbo Tuning
Volvo 740/940 Tuning - Engines
Only concern yourself with the 2litre and 2.4litre turbo models. They are both based on the he B23 block which was first brought in in the 70s. While the engine stayed largely the same there are some key differences which are crucial to know about if your looking at power outputs higher than 250brake.
The most important difference come in the bottom end, namely the rods.
In 1982 the B239ET was introduced and this is a tough engine and can hold 500bhp without blowing apart. However in 1985 it was replaced by the B230FT which can in 3 evolutions. The first version from 1985-1988 was designed as a low friction motor and therefore came with 9mm con rods instead of the 13mm con rods as found on the earlier B239ET and it also used smaller main bearings. These 9mm rod motors struggle with 250bhp, let alone 500.
The second version was lightly stronger but still suffered from con rod problems. In 1989 the third evolution was released and this reverts to using the 13mm con rods. The 3rd version has no distinguishing features from the 2nd version but there is a date stamp on the block and cylinder head. If the motor your looking at is made after 1993 it will also have a piston cooling oil spray bar.
Of these engines a 2litre and 2.3litre version available, they are both as tuneable as each other. The 3rd version of the B230FT had very strong cranks but the rods will be at their limit at 350bhp. Luckily forged rods are available form the states for the 198GBP and they can hold 700bhp. The forged rods can be available in standard length or in an 8m longer version. This is so you can choose between standard pistons and forged versions. There are no reports of these Volvo engine cranks snapping so there is no need to go down the forged route here. If you want to increase the capacity of the 2.3litre versions the crank from the Volvo Penta marine engine can be used with standard length rods. This will give a 2.5litre capacity but you will need to change the pistons and there is a 3mm difference in compression height. Pistons are available from StenParnerMotor.se.
Volvo 740/940 Tuning - Cylinder Head
300bhp is available with an 8 valve head simply by upping the boost. However porting the head will allow to same power output to be made with less boost.
The best head to start with is the 531, 531 will be stamped on the head in between the 2nd and 3rd exhaust ports. Normally 740 turbos were fitted with this head. the 530 head is also good, but not as good as the 531.
For the ultimate cylinder head 16valves is the way to go. 16valve heads can be found on the normally aspirated 155bhp version. If you go down this route the Volvo Penta AQ171 timing belt tensioner can be used along with pockets machined into the standard 8valve pistons. A custom turbo manifold will also need to be made up. The differences between an 8 valve head and a 16 valve head? For 500bhp from the 8 valve head you need 48mm inlet valves and 40mm exhaust valves and a wild cam. For 500bhp from the 16valve head you need double valve springs. Everything else can be left stock.
For the 8 valve head there are a number of cam options available. The most basic change is to swap out the M-Spec cam found on late 940 turbos to the cam found on early 740 turbos which was a bit wilder. Avoid NA cams. Cam manufacturers for these Volvo turbo motors can be found from KG Trimming, ENEM and IPD and can give 25bhp on a standard motor.
Low Pressure (LPT) & High Pressure Turbo (HPT) - The Differences
The engine are exactly the same except for the wastegate setting is different and the ECU map is different. Mechanically they are identical.
Volvo 740/940 Tuning - Transmission
There are loads of autos about but for power you want a manual. The one you want is the M90 and this was fitted to all 700 & 900s after 1994. The older M47 will struggle with 250bhp. The M90s can take 4-500bhp and the 97-98 boxes are particularly tough.
The problem with the M90 box is that you have to use a flywheel from the M47 box as the M90's dual mass flywheel cant take the power. The M47 flywheel needs to be used in conjunction with the Tdi M90 clutch plate and the M47 clutch cover. The combo will handle 300bhp.
Volvo axles are famous for their strength. Some of the Volvo diffs were limited slip versions, but only below 25mph. To get around this the diff can be modified to disable the governor. For the ideal solution is TruTrack LSD can be bought from the states for 250GBP as this is the same axle found in Jeeps.
Volvo 740/940 Tuning - Engine Tuning
Post 1990 740 and 940 cars can be taken past 200bhp with s simple boost hike from 7psi to 12psi. This can be done with simple manual boost controller.
Post 1990 740s and 940s moved to Bosch LH Jetronic 2.2 management and after to 2.4 which is more adaptable. The LH ECUs constantly learn and can therefore automatically adapt to higher boost levels. The 2.4 ecu is compatible with the 2.2 model.
Pre 1990 740s used a more basic Motronic setup that don't adapt so the chip will need to be remapped to compensate for the boost increase. Chips can be bought from Fred's Chips available through Turbobricks for approx 225GBP.
Boost increases on the pre 1990 models should be combined with the 76mm MAF found on the 1991-1994 960s. The standard MAF will max out on boost increases and lead to a cutting of fuel.
As with all turbo motors, sorting the breathing brings big gains. A 3 inch bore system should be used as this will also have enough flow for bigger power increases in he future. Volvo intercoolers are renowned for being massive and are fine up to 300bhp.
Keeping a close idea on your engines health is important so invest in a quality boost gauge as the standard one is crap and also get an A/F meter to get an idea of how rich your mixture. Lean mixtures will destroy ANY engine.
After 200bhp the LF ecu needs to be reprogrammed. Fred's Chip is a plug in item and will increase boot to 15psi. Combined with exhaust, air filter, AF meter and boost controller the motor will be up to 220-250bhp.
US Ford Thunderbird Brown injectors are a straight swap and so are 850 T5-R 390cc injectors.
All Volvo turbos use the same inlet and exhaust sizes. For the cheapest upgrades the S70 uses an 18T turbo and a C70 uses a 19T.
For an aftermarket turbo the Garrett GT35 is good for 500bhp. If your using the 8 valve head the post 1990 items are supposed to be good for +10bhp.
280bhp is the limit for the M-Spec cam, the earlier A-Spec cam from the 740 is a good low cost upgrade. Alternatively cams from he companies listed above are also good. At 300bhp a bigger intercooler would be a good upgrade. After 350bhp new rods are required and so is a new ECU.
A mappable stand alone ECU will give complete adjustability for any power upgrade. Coupled with forged pistons, steel rods, the right turbo and a 16valve head with double valve springs and 500bhp is a reality.
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