FACTS AND MODIFICATIONS: TOYOTA SUPRA ENGINE:
5MGE

 

The 5MGE 2800cc DOHC (dual overhead cam) was introduced in the U.S. Supra in 1982. This Twin Cam was also used on the U.S. Cressida in 1983. This engine was the first production 6 cylinder Toyota Twin Cam- since the 3M Toyota 2000GT (a limited production model). This power plant was one of the main reasons the Supra became very popular, and a Toyota milestone model. In 1984 the EFI (electronic fuel injection) was updated to a digital system and the compression raised, this brought the horsepower up from 145 to 160.

In Japan, a 6MGE 3000cc model was introduced in 1986 that was rated at 200 HP. The engine was identical to the 5MG in design, but related parts to the pistons and crankshaft were different. It is interesting to note that the 6MG was rated by Toyota with the same horsepower as the successor 7MGE 3000cc (a 24 valve model) but with a better torque band! In fact it used a 7MG crankshaft before the 7MG was introduced.

The Twin Cam head is a G type- meaning Sports Type. Also a first for Toyota- the head featured hydraulic valve adjustment, eliminating the shims (which most mechanics feared). This engine allowed Toyota to position the Supra above all the other Japanese models and on par with the leading European manufacturers.

Toyota's philosophy in product design, which is based on continuing evolution, shows distinctly in this engine. The M block started life as a 2000cc, became the 2M 2300cc., the 4M 2600cc., and the 5M 2800 cc. The 5MG and 6MG Twin Cam (12 valves), which preceded the 7MG (24 valves), allowed Toyota Twin Cam power in a whole new market segment (the 6 cylinder Twin Cam heads were previously available only in the 3M). Toyota's vaunted dependability and reliability is evolved. The Twin Cam head is a crowning act on Toyota's legendary block.

In competition  the 5MG-powered Supras were used for showroom stock racing (SCCA SSA) and in the IMSA Firestone Endurance Series. The cars ran trouble free, won a lot of races, and even held track records in Willow Springs. As a real GT (Grand Touring) the 5MG was incomparable to any engine in its class.

This engine ignited a lot of interest for aftermarket parts manufacturers. Engine kits for 2900cc and even 3100cc were available, but very expensive. Powerboat racing saw many 5MGs screaming in open sea events- another testimony to the engines durability. In power boat racing the engines are revving flat-out like in 1st gear all the time.

MODIFYING THE 5MG/ 6MG

BLOCK: The 5th generation 5MG has a tested and proven bottom end. The 5MG responds extremely well to the 2900cc conversion or the 3100cc engine kit. In 2900cc form it was proved that the Supra will out accelerate Mustangs and Camaros in the racetracks and actually outrace them on the straights. Basic block preparation is all that is needed, no secrets here. The head gasket can cause serious wear on the block surface, so it is a good idea to deck them. A cost effective upgrade is to go 6MG.

Although the 6MG looks externally similar- internal components are different. You cannot drop a 6MG crank on a 5MG without changing related pieces- timing cover, pulleys, pistons, etc. For practical and cost purposes if you want to have 3000cc., get a complete 6MG. The 5MG / 6MG has a durable bottom end and will out last the cylinder heads before needing attention.

CYLINDER HEAD: The cylinder heads suffer from abnormal wear from carbon build up. The EGR causes oil to deteriorate sooner than some engines and leaves a lot of accumulated carbon. Prepare the head with a port and polish treatment, this is a good value in terms of added performance. Headers and exhaust systems will help allow the engine to breath since the cars they powered were tuned for quiet GT luxury touring.

The 6MG intake manifold uses bigger intake runners. This will bolt to the 5MG head, but does not have provisions for EGR. In fact, if you are upgrading to a 6MG- you have to transfer all the related 5MG EGR pieces to the new engines. Everything is transferable. Make sure that the EGR is clean and decarbonized- it will ensure passing smog requirements.

There are aftermarket cams available, but unless the compression is raised the cams are of no use. Adjustable cam gears are also mandatory because these engines are very sensitive to camshaft settings. The cam towers need close inspection during rebuilding. Since the cams have a tendency to wear out- the towers may also be bad.

TURBO-UPGRADE: For all-out power Turbo charging is the way to go. Mandatory forged pistons will allow the engine to see and survive boost levels higher than the 7MGTE. An advantage is that the valves are bigger (although less in number) which will survive the heat better than the smaller valves of the 7MGTE (24 valves). Under boost the advantage of 24 valves is minimized. EFI upgrades are necessary to maintain the correct A/F ratio. There are Twin Turbo manifolds available from HKS. Properly set-up, a 5MG Turbocharged easily outrun 7MGTs similarly equipped with upgrades (the bodies were considerably lighter and the engines responded better- pound for pound of boost.

FUEL SYSTEM: The fuel injection system was upgraded in the later models, but the effect on performance was from raised compression. Unless the engine is turbocharged there is no need for any modification.

IGNITION SYSTEM: Any modified engine will need step colder spark plugs. The standard ignition is adequate, but can be supplemented with ignition upgrades. Although advancing the timing setting helps, be conservative (past the factory specs) since the knock sensors will automatically retard the ignition.

SOME RECOMMENDED SET-UPS:

For Stock configuration- The six cylinder in-line engine is a smooth power plant. The Twin Cam head allows it to rev much higher than any head configuration. This provides a smooth and powerful power source. Upgrade to the 84 pistons if you need to oversize. The cylinder head can be ported with no effect on emissions. Use a machine shop that is experienced in working with these aluminum heads and thoroughly inspect the cam towers also.

For Modified configuration- The 2900cc piston set or the 3100cc will be the ultimate set-up in naturally aspirated form. These will produce over 230 (2.9L) / 250 (3.1L) HP with no further modifications. Head preparation must be done to allow the bigger displacement to breathe properly.

The 6MG is a cost effective alternative. The fuel injection system on the late 5MG and 6MG are the same, to install the 6MG in an early 5MG- all the sensors including the TPS (throttle positioner sensor) must be transferred.

For Racing configuration- Race regulations allow specific limited modifications. If allowed the displacement upgrades will be ideal. Radical camshafts will need a reprogrammed ECU or an entirely new one (Tech II or similar unit). Anticipated horsepower over 400 will need new connecting rods, the crankshaft will be fine with correct bearing clearances and chamfered oil holes. Disable the EGR. There are available a limited number of Triple side draft manifolds- which will also need a direct fire ignition system (since the distributor is disabled).
 
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*******On this website I am sharing the things I find out along the way. I do not guarantee that these modifications will work on your specific vehicle, any damages caused as part of the installation or use of these modifications are the the responsibility of the person who performed the installation.