Turbo 240 in the UK, a brief how-to/overview

[Bugjam1999]

Hi all,

I’ve written the overview guide below to answer the most frequently asked questions about turbo converting a 240. Please have a read through and let me know if anything isn’t correct or needs adding and I’ll edit the post.

The idea is that it should be moved into the technical articles section, but I’ll leave it here for a week or so, so I can collect suggestions and edit.

Cheers

Turbo 240 in the UK.

This mini guide covers the basics of a Volvo 240 turbo conversion in the UK. It is not exhaustive, it is merely an overview with answers to the most frequent questions assuming that you want to take the engine from a 940 and bolt it into a 240 without making any major changes. If you do want to make major changes you may already know more than what’s in this guide.

Firstly some very brief history of the Volvo Redblock engine – this was originally manufactured by Volvo back in the 70’s and the same basic design was used by Volvo through to 1998, with some internal improvements along the way. Used in the 244/245, the 240, the 740 and the 940, the original engines were 2.1 with a carburettor, then came mechanical fuel injection (also called k-jet), the latest engines were 2.3 turbo with electronic fuel injection (also called 2.4lh). The main point to note here is that because the same engine block was used across those models and remained basically unchanged externally through the production run, a late engine will bolt into an earlier car / different model of car without difficulty.

The best engine acquire for a turbo conversion is a 2.3 turbo from a 940 from 1993 or later (later engines got stronger rods (13mm not 9mm) and piston skirt cooling oil squirters) in as good condition and as low mileage as you can find.

Engine mounts: unbolt the 940 engine mounts and bolt on the 240 ones.

Gearbox: if you have a manual 5-speed M47 in your 240, the 940 engine will bolt up to it with no modifications. If you want to fit the later m90 5 speed from a 1995 onwards 940, then there is some modification to do (fabricate a gearbox mount, have the prop lengthened, shorten the gearstick support rod and the gearstick actuator rod) there are plenty of threads about this online.

Overall the best gearbox is the m90 (from a 1995 onward 940) which is stronger than an m47 (the standard 5 speed from a 240) - search for instructions online to weld the third gear synchro for more longevity. This may be overkill for most, but worth knowing about.

Flywheel: you will need a flywheel which has the 60-2 timing notches in it for the crank sensor to read. Either use the dual mass flywheel from the 940 (if you’re putting in the m90 gearbox), or source a late model single mass flywheel with the notches in it - look for a 240 or 940 with an m47 gearbox and 2.4lh. There are various aftermarket options available. Note – the flywheel needs to be timed correctly for the engine to run; with the engine at TDC, the 2 blank notches need to be pointing at the hole in the crankcase for the starter motor.

Clutch: you’ll need something better than the standard 240 clutch – aftermarket clutches are available, or for the m90 a 940 turbo diesel clutch is a popular choice.

Fuel lines: if your car was originally equipped with a carburettor then you’ll need to plumb in a flow and return line for the fuel injection. If your car was originally k-jet or 2.4lh, the flow and return lines you need are already there.

Fuel pump: the intank pump and main pump combination on a k-jet or 2.4lh car will work fine for moderate levels of boost on a fairly standard 940 turbo engine. Various options exist for increased flow but if you’re looking at a highly modified/boosted engine you’ll know that anyway.

Intercooler: a 740 or 940 one with entry and exit at the top (rather than half way down) will bolt into the 240 using combined radiator / intercooler mounts from a USA car (the USA got turbo 240s). A mid entry/exit intercooler can be made to fit fairly easily although you’ll need to fabricate some mounts for it. There are various threads online about fitting a different intercooler.

Fan: the 940 ecu will control a two stage fan relay and electric fan, but they can kick in a bit late meaning the car runs hot in traffic. Use an external adjustable fan controller or a two stage thermostat switch in an adapter in the radiator top hose. Alternatively a mechanical fan will fit.

ECU and EZK: you will need these from a turbo car, the fuelling map in a n/a car ECU doesn’t go far enough for the fuelling meaning the engine will run very lean whilst on boost and go bang as a result. You will probably need chips for them to remove the immobiliser function. Various people online can supply chips, usually with a higher rev limit and a richer fuel map at full throttle. The chip can be swapped in the ecu without difficulty, not all ezk s have the required daughter board which is where the swappable chip sits- gold ezk s have the daughter board, as do occasional black ezk s. A kit to solder a daughter board into an ezk that previously didn’t have one exists.

Wiring: potentially the biggest headache. For a late model 240 with 2.4lh, the ECU and EZK boxes should be removed and replaced with the turbo ones and that’s the extent of the wiring. For the carburettor or K-jet cars a transplant of a new wiring loom will be required – either from a 940, cut down to suit or from a late model 240. There are various threads on this online, but don’t underestimate how long this will take! Aftermarket looms for people carrying out engine swaps are available, unless you really like wiring you should consider this as it will save a lot of time. You will need to use the ignition amplifier from a 2.4lh car – they look the same as for a k-jet car but work differently internally.

Injectors: the 940 uses low impedance injectors as standard, with a resistor pack as part of the loom. The loom in a 2.4lh 240 does not have this resistor pack as the injectors it uses are high impedence. You cannot use the standard 940 injectors with a 240 loom unless you solder in a resistor pack, if you do you’ll burn out the injector driver in the ecu. A much easier solution is to buy injectors from a later model 850 t5, which are high impedance, fit into the fuel rail and don’t require any changes to the wiring.

Distributor: the 940 has this at the back of the cylinder head, but there isn’t space for it in this location in the 240. The distributor from the 240 engine needs to be transplanted onto the 940 engine block in the 240 position. Firstly, to enable this, the auxiliary shaft that turns the oil pump in both engines and the distributor in the 240 engine needs to be transplanted into the 940 engine - various threads online.

Also, take care to time the distributor correctly. With the engine at TBC, the distributor arm should be pointing at number one cylinder, there’s also a notch on the distributor edge – there are various pictures online. Similarly, the blanking plug from the back of the 240 head needs to be transplanted to the back of the 940 head – where the 940 distributor was removed from.

An alternative is to use a wasted spark board- an additional aftermarket circuit is added to the ezk box, meaning no need for a distributor or the swapping of the aux shaft to turn it. Other parts are needed- various threads online.

Cooling - the 940 uses an oil to water interchanger to dump excess heat from the oil system into the radiator system, this is on the right hand side of the engine and has the oil filter on the end of it. It will fit in the 240 engine bay unchanged. The Use the 940 expansion tank hose hose as it has the tee for the turbo coolant return.

Exhaust - downpipe for the 940 won’t fit unchanged, but it can be cut and rewelded to fit. The section of steering column between the bulkhead and the rack can be flipped upside down to gain some more space in this area. If you’re building a full custom system a 3inch downpipe can be made to fit. 2.5inch probably more common.


So- what have I missed?

[Bugjam1999]

Things to add:

Extend maf wiring in a 2.4lh equipped 240 as the maf on a turbo engine is on the drivers side of the car, not the passenger side

Swap the instrument cluster temp sensor over from the 240 cylinder head to the 940 cylinder head as they’re different

Cheers

[mylittletony]

More observations than changes.

On my carb car I used the carb fuel feed line as the return. The sender and in tank pump cradle needs swapping if you have a carb car. It's easiest to fit a large (255lph) in tank pump to do the job of both.

I think the front panel differs on the early cars making intercooler/radiator fitting more of a custom job.

You can get a 940td clutch to suit the m47 as well.

I used a separate oil cooler instead of the 940 arrangement, but it's pretty busy behind the alternator. I've seen people move the alternator and use the 940 elbow thing pointing forward.

Oh and do oil seals while the engine is out.

Otherwise excellent work