Despite Toyota's reputation for building efficient and reliable engines, it's very rare to hear of anyone getting stuck into modifying a Toyota product. Nissan's SR20DET and Subaru's EJ20 turbos have been done to death in this country, but - for some reason - the rival 3S-GTE gets overlooked.
To give you an idea of this engine's potential - and to stop you forgetting about them! - we spoke to Paul Brell of BD4s about his 270kW at-the-wheels MR2 turbo. We've covered the car previously ("A 1-OFF Creation") but since then the engine's been stroked and a host of other changes made.
And here's how he pulled so much power from this often kicked-in-the-guts engine...
Paul's locally delivered SW20 MR2 was purchased having already been converted to a S185 version of the 3S-GTE turbo engine (as came fitted to the Australian market 1990-1993 Celica GT4s). The S185 engine was treated to an assortment of quality aftermarket gear, but - ultimately - it never really made the outright power it 'should' have.
The biggest problem with this engine was its tendency to blow head gaskets; Paul claims the S185 suffers from flexing in the top-end.
Eliminating this problem and enabling a higher power output is the replacement S205 version of the 3S-GTE (the same design that came in the later-model Celica GT4 Group A). Paul's engine and gearbox assembly was sourced second-hand from a 1994 Japanese-market MR2 and it slid straight into the bay.
So what's the difference between the S185 and the later S205 engine?
Paul's identified that the S205 scores a 4-port intake manifold (non-TVIS), an improved sump, MAP sensor load input, 550cc injectors, the head casting is different with exhaust ports spaced further apart, a steel composite head gasket is fitted and - finally - a larger turbo delivers up to around 1.0 Bar. In short, the S205 version of the 3S-GTE offers increased strength, efficiency and tuning potential.
Prompted by a customer and the delayed release of an off-the-shelf HKS kit, Paul has bored and stroked his 3S-GTE from 1998cc to a claimed 2340cc.
The bottom-end is now equipped with a Toyota 5F-E crankshaft (as found in post-93 Celicas). Note that the 5F-E crank delivers a 8.6mm increase over the standard engine's 86mm stroke. Paul has also had this particular shaft knife-edged, nitrided and balanced - not to mention weighed at 16kg - while fitment into the S205 block required simply machining the journals. The bearings used were "nothing special."
A custom flywheel also had to be fabricated to suit the butt of the new crank and the ST205 clutch and pressure-plate layout. The opposite end of the crank is fitted with a GFB pulley, which is both lightweight and reduces the rotational speed of various engine accessories.
Prior to cylinder boring, Paul thought it'd be wise to send the block off to be tested. These images revealed there was plenty of lining material to get away with the planned 0.5mm overbore. To fill these slightly enlarged openings, a set of US-sourced pistons was fitted. Paul says these pistons deliver a static compression ratio of around 7.5:1, and have quite a short skirt in order to clear the increased crankshaft stroke. Each one - together with gudgeon pins - weighs 440 grams. Rings are of the gapped variety.
Despite the torque on offer, a set of linished and shot-peened S205 rods have - so far - held up admirably. Both the rod and crank bolts, however, were automatically upgraded to ARP units.
Atop of the machined block you'll find a HKS 'stopper type' 1mm steel head gasket. Unlike the S185 engine, there have been - again, so far - no sealing problems.
The DOHC, 16-valve cylinder head has come in for quite a bit of detail work. The ports have been tidied up, there's firmer HKS valve springs (working with the standard valves), new guides and JUN retainers. Because valve actuation is direct via buckets and shims, there are no rocker arms to be found in the 3S-GTE. Paul also made the point that these under-bucket shims won't "jump off" with a big rev.
Both camshafts deliver 272 degrees of duration on the inlet and exhaust, with 10.4mm lift on the inlet and 10.2mm on the exhaust side. HKS aluminium slide adjustable cam sprockets are installed, but the cam timing has not been altered.
Exhaust gasses are channelled through a bolt-on HKS 3mm thick stainless manifold, which comes complete with provisions for an external wastegate. Paul's car uses a HKS 3240 ball-bearing turbocharger, which the guys in Japan say performs well to approximately 1.6-Bar. Not coincidentally, Paul has set max boost pretty close to that mark - 1.75-Bar is the most you can dial up on his HKS EVC system. A big HKS external wastegate prevents over-boosting by dumping excess gasses straight into the exhaust system.
Running off the back of the turbine is a heat-wrapped 3-inch mandrel bent dump pipe, which immediately flares out to 3½-inch, passes through a braided flex joint, goes over the cross-member and tee's into twin 3½-inch pipes with no mufflers. HyperTune can be thanked for the exhaust fabrication.
You'll notice the exhaust captured in our photos is of an earlier system. This "streetable" set-up used a single 3-inch pipe splitting into twin 2½-inch pipes with Super Drager mufflers. Obviously, this configuration was much quieter...
Producing 270kW at-the-wheels, Paul tells us the untouched-from-factory intake manifold assembly is the bit holding power back (other than the strength of the near-standard rods). Although the current set-up sees 1.0-Bar boost at below 4000 rpm, the power output is ultimately down once you get to around 7000 rpm and beyond. Plans are to cut the standard intake runners, whack some ram tubes on the end and encase them in a custom plenum. A larger throttle is likely to be fitted also.
The rest of the intake system is about as serious as you could ever get. A new 4½-inch thick GT-R Skyline air-to-air intercooler core - with Plazmaman custom end-tanks - does a good job chilling the charge-air. Due to limited natural airflow through the core, however, there's a pair of 12-inch electric fans sucking air from beneath. Paul claims intake temperatures are typically around the 40 degree Celsius mark most days, but after prolonged testing on the chassis dyno it can still soar past 140 degrees...
Plumbing to and from the intercooler is 70mm diameter (fitted by Yosh of BD4s and Mark of HyperTune), while the end-tanks - at the time of our shoot - were equipped with twin HKS Super Sequential blow-off valves. These are currently removed from the scene, but Paul plans to fit a large-body HKS valve. This should eliminate the audible compressor surge that now - minus a blow-off valve - accompanies eager up-shifts. Oh, and this monster 3S-GTE breathes clean air thanks to a HKS Super PowerFlow air filter, which is fed by a moulded cold-air ram snorkel.
Of course, with anywhere near this level of power an aftermarket programmable injection system is a must. Paul's highly tuned 3S-GTE runs a quality MoTeC M4 management system to control both fuel and ignition.
Despite being relatively large, the standard S205 injectors have been replaced by four massive 1000cc HKS squirters, together with a HKS rail and pressure regulator. A Nizmo R32 GT-R in-tank pump supplies around 4.5-Bar fuel pressure at idle (as measured in the rail). "A lot of people are amazed - it's a system that idles beautifully," says Paul.
Under full load, you'll find air-fuel ratios are set to around 12.2:1 - but that's running good ol' C16 in the tank. We're told C16 allows a slightly leaner fuel mixture.
The ignition arrangement still needs a little sorting according to Paul. At the moment, it's the standard single coil augmented by a HKS amplifier - but the one-range colder platinum plugs are apparently prone to fouling whenever the tank is filled with race fuel. It's anticipated perhaps a MoTeC CDI will help things out. The existing MoTeC M4, however, is also used to enforce a 7000-rpm limit; Paul says torque tails off around that point, so there's no point spinning it to 8000+ revs.
As mentioned, the BD4s MR2 can crank out a highly impressive 270kW at-the-wheels (on a Dyno Dynamics chassis dyno). If you want to assume a 20 percent driveline loss across the transaxle you're talking a plump 324kW at the flywheel! Note, however, that 270kW ATW figure was achieved running the maximum 1.75-Bar boost and C16 ultra high-octane fuel. For street use, boost is limited to 1.0-Bar and Shell Optimax is good enough for around 200-210kW at the wheels.
Rather than assume things went 100 percent smoothly, you'll be interested to discover Paul's had a few problems on the way to 270RWKW...
Firstly, there were hassles keeping a lid on fuel temperature on the chassis dyno. Partly due to the covers that prevent airflow past the MR2's mid-mounted fuel tank, it was discovered fuel was bubbling in the injection rail. This was remedied by the fitting a fuel cooler on the EFI system return line.
Engine oil, too, had to be kept cool. Paul now runs a thermostat-controlled system that bleeds into an oil cooler (which is situated in the standard intercooler position, in the right side flank).
It's fair to say the overall driveline is pretty much near its limit.
Working with the aforementioned custom flywheel, you'll find a Daikin heavy-duty pressure plate and a 5-puck brass sprung centre clutch. Paul tells us it holds okay on the street, but he wouldn't expect it to stay together for many drag strip passes.
The gearbox, too, is treading a fine line. Paul's had a few gearboxes in the past - through both synchro problems and gear breakages - but he thinks he's now got the situation licked. By keeping the gearbox/diff fluid (Repsol Competition 75/90) at a stable temperature, he's kept the existing 'box together for a considerable amount of time - though, note the car only racks up about 3000 kilometres per year. This stable fluid temperature has been achieved using a large oil-to-air cooler at the rear of the car; this is fed by the MR2's standard in-built gearbox fluid pump.
The final addition to the driveline has been a second-generation TRD LSD unit. This has been "shimmed-up" by BD4s, and - other than some existing camber issues - traction off the line is very good.
So - now you know what's involved in a 270kW-at-the-wheels 3S-GTE - let's see a few more people goin' hard and fast in a Toyota!