MR2 V6 Conversion

22-Sep-2012

We recently visited a customer (Terry O'Beirne of Road and Track in North Ipswich) carrying out a 2GR conversion into a turbo SW20 MR2. The engine and related electronics from 2009 Australian Aurion sedan.

Below are the details on Terry's project that we will be documenting from start to finish

Arrival

The engine package comprised engine as removed, air-box with intake piping, plastic incoming fuel line, security ECU with matching key & transponder, air-con compressor pipes, engine ECU & matching harness, special harness for the security system & the electronic throttle pedal.

Despite "assurances" about gearbox fitting, we quickly found only some E code boxes come close to fitting properly. The pre-93 MR2 boxes only have 3 holes that line up, and one of them requires the block to be helicoiled. A later E153 box had 7 bolts that lined up. Any MR2 turbo box post Oct 93 should be OK, except it will have ratios unsuited to the V6.

Gearbox & axles

A 3VZ V6 Camry flywheel with matching bolts, was found to fit perfectly.

After studying the gearbox situation, we concluded the existing early SW20 box will not suit. We selected a late model V6 gearbox due to a combination of better ratios and it bolts up much better. The V6 Camry gearbox however requires complete dismantling & the shifter mechanism reversed (we have made tooling to do this job) . The speedo gears in the V6 box wont suit the MR2 speedo, so these have to be changed. A TRD plate type LSD was fitted while we had it apart.

 

MR2 SW20 3sgte

3VZ wide-body camry V6

diff

60/14=4.285

58/16=3.625

1

42/13=3,231

43/12=3.583

2

44/23= 1.913

45/22=2.045

3

39/31=1.258

40/30=1.333

4

34/37=0.919

35/36=0.972

5

30/41= 0.732

30/41=0.732

A number of issues quickly became evident.

  • The MR2 clutch slave cylinder hits the block and grinding the block away will remove part of the factory engine number.Spacing it out away from the block will result in a poor shaft angle and likely a short cylinder life, so that idea was rejected. The entire SW20 clutch cylinder and bracket has been relocated with a specially made adaptor, and the untrained eye would never notice the change.
  • none of the various 3SG rear engine plates will suit the V6, so we will leave it out. as its mostly a seal plate, this wont be a problem on this conversion as the V6 box seals against the block OK.
  • the axle seal plate on the side of the box, hits the block. this can be fixed with minor grinding of the plate and block. This plate on the V6 box is not the same as MR2 as it is missing 1 bolt that is part of the engine mounting bracket. The MR2 plate will be refitted.
  • The support bearing on the long axle had to be moved 10mm to allow it all to align with block mountings

A 3VZ V6 flywheel was lightened ( down to 6.6kg) and we have made an uprated organic clutch based on a stock GT4 unit. By increasing the pressure plate clamp force, we should have a reliable clutch that is still nice to drive.

Wiring & electrics

A 2-volume wiring manual was obtained and we quickly sorted out where most of the wiring went. We also found out the Australian built Aurion has unique harness/ECU, so info from other conversions in the USA and UK is not 100% useful.

The engine loom has a few un-used plugs for radiator & air-con fans that we taped up securely, as removing them totally from the loom would take many hours. Various sections of the 3SGTE harness were removed and others merged with the 2GR harness to make connections into the fuse box etc, much easier. The Australian Aurion engine operates with a complex security system which must be retained and integrated into the MR2 to get the engine running. The only alternative to this is to use a non-standard computer, however this will preclude fitment of the Qld approved modification plate, so we did not go down that route.

For the engines first test run, the electronic throttle was temporarily connected down in the boot with the ECU. We later obtained some special 7 core cable and the electronic pedal was finally mounted where it should be, using a custom made alloy bracket.

The stock tacho was modified to suit the new ignition signal.

The wiring took 8 solid days of work to get it looking like a factory install, with everything working as expected. Another one would be much quicker, but merging the harnesses neatly will never be a few-hour job.

Engine

We obtained some specially made exhaust manifolds and engine mounting brackets from the USA. The manifolds required re-machining to make the gasket faces flat and the mount adaptors had to be re-machined to get full engagement of the nuts on the mounts. The manifolds have no provision for oxy sensors (essential-engine wont start without them), so these have been relocated further down the pipe. Each pipe has sensors either side of the catalytic converter, with 1 pair being special wide band ones. Because they are heated sensors, the location proved not be a problem. Mini hi-flow catalytic convertors were fitted and the exhaust goes over the subframe to give sensible ground clearance, unlike some US conversion we have seen pics of. A sump "bash plate" is planned to protect the bottom of the engine and the wiring to these senors.

The water transfer pipe on the V6 was modified by us to accept a 3SGTE sender unit for the dash gauge and accept a hose from the stock MR2 water filler. Other hoses required minor alterations.

These V6 engines are fitted with a return-less fuel system and we decided to change that, rather than convert the tank and hoses to the Aurion system. We retained the snap-lock connector on the end of the rail, but added an external adjustable regulator to incoming line. This took a bit of fiddling with to get pressure right.

Fitment

With the gearbox mounted, the entire package fits into the bay OK, with more room in some places than the stock GTE engine. The lower part of RH engine mount purchased from the USA had to be re-machined to allow the 2 vertical studs to fully engage on their nuts . The oval holes in it top half had to be elongated to move the bracket further so it would not hit the water pump pulley. The alloy casing around the Toyota mount was machined down for more clearance. With this mounting arrangement, changing the serpentine belt will always require mount removal. A much shorter belt was used as we not longer have the Aurion power steering pump

The alternator power output wire hit the metal insulation plate on the firewall, and we had to "massage" the panel to give clearance. The air-con compressor is a very tight squeeze and refitting this was not a simple job. A special belt was located. The final "plumbing" is yet to be finalised as the owner was un-concerned about this.

The plastic cover over the engine was refitted after the drivers side was modified to clear various hoses found in the MR2 body. A short length of new vacuum line was required to joint the intake manifold to the MR2 brake booster pipe over by the right strut tower. An engine bay cooling fan from a NA model, was fitted where the inter-cooler used to be. The engine bay cross brace has to be packed upwards at the strut end to clear the plastic cover.

A Ford FPV enclosed pod filter was supplied by the owner and adapted by us. This was much harder than needed, and we would not do this again. We normally use an enclosed K&N pod on most conversions as they come in a kit with plenty of suitable hose etc, and are dead easy to mount. The hardest part of any air intake conversion is fitting the MAF sensor. These sensors are very sensitive to location and positioning in the pipework as the flow in a pipe is not uniform across the diameter.

Driving

The owner is ecstatic. Performance is shattering. The custom exhaust make a glorious noise but will still pass a noise test. We are really glad we changed the gearbox ratios and we could still deal with a taller final drive ratio.

Do it again

We look forward to doing this again and would suggest this is a better option than a heavily modified 3SGTE. Despite issues, we would probably use the US sourced manifolds and mounting plates again as its cheaper than custom made ones here. Changing to a taller final drive would be no real hassle. We would certainly not use the Ford FPV air filter again.

We are happy to undertake jobs like this, but please realise we are not a free consultancy service. If you want to do conversion yourself, then do your own research & experimentation using the above as a guide. We are unfortunately unable to respond to email or phone requests for free advice on wiring problems, emisions , computers etc.


MR2 V6 Conversion
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