Here is some info: (
http://www.toysport.com)
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 we have 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 and we have a couple remaining, this includes a new plenum! 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. We have 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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