Toyota Six Power!

This article was first published in February 1999. However, even after all these years, the Toyota six cylinder turbo twins still remain amongst our favourite of six cylinder engines, bar none!

In this Toyota Six Super Special we take a look at the 1JZ- and 2JZ- engines. Both are relatively recent arrivals on the hi-po import engine scene, but the flow of both factory-official (in Australia the 2JZ-GE is in the Lexus GS300) and aftermarket Japanese import engines has recently become a flood. And in the US these engines have been available for years; the 2JZ-GTE since the '93 Supra.

We were prompted to look at the Toyota sixes by three things:

• on Allan Engineering's engine dyno we saw a 2JZ-GTE VVT-i pumping out simply extraordinary power and torque figures considering the lack of modification;
• we took a mildly modified twin turbo Supra for a drive and found that it went bloody hard on the road;

• and we found a complete 1JZ-GTE Japanese import half-cut (pictured here) at Jap-Parts in Adelaide (Australia) for just A$2800!

Jeez, if only we had the dosh to put that superb drivetrain in a mid-Eighties Cressida - what a refined and potent weapon that would be......

Anyway, we're going to start off with the Supra.....

Afterburner Supra

With the looks of an F-14 fighter and the thrust of a second turbo to help it approach Mach speeds, Toyota's current-shape twin-turbo Supra is a killer. Low, wide and aggressive, its overtly aggressive appearance sets it apart in the world of modern Japanese hi-po machines.

Powered by the 2JZ-GTE sequential turbo motor, its response and full throttle performance pushes the boundaries of rear-wheel-drive chassis dynamics. The engine's primary turbo comes onto boost delightfully low in the rev range, giving monstrous low-down torque and brilliant throttle response, while those keen enough to employ the secondary turbo will be mightily impressed by the next stage of the power delivery.

The 2JZ engine is the latest in ultra high performance engineering from Japan and shows a technological upgrade over the RB26DETT that propels Nissan's Skyline GT-Rs. There are strong similarities between the pair - both are straight sixes with a DOHC 24-valve head, two turbos, intercooling and of course EFI. However, Toyota's 2JZ-GTE has aced the RB26 by including VVT-i (variable valve timing) and a sophisticated sequential turbo system which improves the overall spread of boost (and therefore torque). The swept volume of the engine has also been pushed to 3 litres.

Driving it on the road, the sequencing of the turbos can be felt as the primary turbo works from remarkably low loads. From then on, torque feels strong and instantly available until the progression into the second turbocharging stage. You can't feel any torque dips as the second turbo comes on - but it might seem that way due to the power surge when it starts pumping freely.

Drew Dawson owns this 1994 model Supra twin-turbo that he bought as a low-volume import in late 1997. It came hung with every factory option available including leather seats, auto trans and all the electrics which are commonplace on top Japanese car these days.

Drew didn't need to do that much to the car to decongest it as it came fitted with some name-brand goodies ex-Japan. This included a cat-back 3-inch Trust mandrel exhaust system that is remarkably quiet considering there's just the single big chrome muffler at the rear. Adrian, an employee who often gets to drive the car, says he's wants that muffler to get the chop so the car has a little more attitude!

The intake filtering and ducting into the turbos remains stock to keep the factory under-bonnet look, but there is a TurboSmart blow-off valve to go pssht when the driver realises what speed they're doing and suddenly has to back off the throttle. As only mild boost levels are used, the standard air-to-air intercooling system remains at the front of the car. Boost adjustments set between 0.7 and 0.9 Bar can be dialled up on the APEXi electronic boost controller to give small but worthwhile power increases. Don't forget these things have a conservatively rated 280hp in stock trim!

For the moment the car rides on Toyota's good-looking original 16-inch rims clad in 225/50 Yokohama Avantis at the front and 245/50 Sumitomo HTRs at the business end. Adrian says the Sumitomos are much better than the previous Yokos, giving improved cornering adhesion to the point where the traction control system can be turned off under most conditions. On the topic of traction, the car has been tied down to a chassis dyno to record around 205kW (275hp) at the wheels on 0.7 Bar - but with major wheel slip problems. Adrian says it wasn't a proper reading, and the dyno guys didn't even bother printing out the graph. So what about on 0.9 Bar boost? Well the car thrashed and bucked on the rollers to achieve an indicated 245kW (328hp) - but that's a very rubbery 245kW...

When we took the car for a hoot, our first impressions were of the interior's very concentrated gauges and controls. Everything is aimed directly at the driver in true fighter cockpit style, and the placement of the gear selector fell very close to hand. The steering is perfectly weighted and inspiringly precise, the ABS brakes felt very powerful and there's bags of torque everywhere in the rev range. What wasn't as positive was the amount of rear and side/rear vision - the big sculpted pillars, high boot line and rear wing all conspire to make reversing as difficult as possible. But still, who cares - it looks absolutely sensational!

And for sure, the Supra is as big a car as its 80's predecessors - just looking out across the huge bonnet is enough to convince you of that. But the styling of the panels hide this to some extent, its goggle headlights, daring round tail lights, side vents and massive wing all grab the eye at first glance. In Japan huge rear deck wings are all the rage - Imprezas, Lancers, they've all got them. But the Supra goes one better with its retractable front spoiler which extends closer to the ground at just over 110km/h, helping to stop air getting under the car.

The Supra TT is certainly a major player in the ultra hi-po market - but just imagine if it were AWD! Then we'd be truly be in heaven...

So that's the car on the road, but how good are these engines on the dyno?

On the Engine Dyno...

Allan Engineering in Adelaide (Australia) were given a VVT-i 2JZ-GTE sequential twin turbo engine that had just been imported from Japan by Japanese Motorsport. The engine was only a few thousand kilometres old; basically brand new but with just enough run-in time to allow the guys at Allan Engineering the chance to put some load on the mill...

The customer asked Allan Engineering to fit Autronic programmable engine management and then to see what the engine would do. The engine's owner wasn't after a balls-to-the-wall performance; rather they wanted about 300kW (400hp) without spending a heap more cash. That directive meant that tricky bits like new turbos were out of the question. Not that this financial limitation mattered in the end; this engine was just so strong that it blew the father and son combination of Craig and Adam Allan far away! With the superb smoothness and sheer grunt that the six pack rolled out in basically factory spec, that's not surprising. And we might add that the Allans aren't all that easily impressed - the older Toyota engines that they've seen on their dyno haven't done much for them at all....

Strapping the engine to the eddy-current Schenck dyno was easy; making the Autronic management control the engine's electronic throttle and variable intake cam timing wasn't! In order that the set-up be simplified, Allan Engineering used a manual throttle butterfly and permanently set the inlet cam timing 30 degrees (two teeth) advanced. The crank angle sensor was modified and various other sensors altered or replaced so that the engine would work happily with the new management system.

In order that air mass consumption could be measured, a hotwire airflow meter was mounted on the inlet to the two turbos. The Autronic management system used MAP sensing, so the airflow measurement was just for data logging.

Six Bosch coils were used to direct-fire the spark plugs, which remained standard in heat range and type.

Air/fuel ratio analysis was carried out with an Autronic air/fuel ratio meter using an oxygen sensor input. Exhaust gas temps were measured with a K-Type thermocouple. Very efficient water/air intercooling was used on the dyno - better than you'd be able to achieve on the road or track.

As indicated earlier, the two sequential turbos remained standard. They don't look overly big, but they certainly can flow some gas....

With the engine fired up and running 10-14psi boost, it soon become obvious that they way in which the two turbos were brought on strongly influenced the end result. One turbo uses a valve to restrict its inlet and a second valve to restrict its exhaust, allowing this turbo to be brought on-stream progressively. In addition, both turbos use wastegates. With the turbos run simultaneously (ie both spinning up together) the bottom end torque at 1500-2000 rpm was strong at 200 ft-lbs - strong, but not breathtaking! The blue line on the graph shows the torque output with simultaneous turbos. Spinning up just the turbos sequentially (brown line) gave much better bottom-end boost and so the torque was much higher - in fact, as high as 350 ft-lbs (475 Nm) at 2000 rpm! This is staggering bottom-end torque from a turbo 3 litre six. However, care had to be taken with the technique used to bring on the second turbo. It was very easy to have a 75 ft-lb (100 Nm) drop in torque when the second turbo was fed gas - the exhaust flow then being split between the two turbos and so the boost figure dropping until both turbos came fully on stream.

In fact this area of turbo sequencing was so tricky that Allan Engineering decided to wait until the engine was in a car to set this up correctly. They expect to have to pulse width modulate (PWM) one of the control valves to set up the turbo to very progressively come one stream.

This graph shows the power output of the engine in simultaneous turbo from (blue line) and sequential turbo form (brown line). And what about the peak power? As you can see from the graph, the guys saw a peak power of 400hp (~300kW). But what the graph doesn't show is how easily this was achieved - in fact, a restrictor on the inlet to the two turbos was needed to control the boost as the wastegates were having some difficulty bringing boost back down! Also, the injectors were running at only around 75 per cent duty cycle with the standard Toyota pressure regulator - well within their capabilities.

Ok - wanna forget the techo stuff? - these engines are just monsters in their power development capabilities!

The JZ engines....

Lexus in Adelaide (Australia) very kindly made available to us the GS300 workshop manuals which cover the naturally aspirated 166kW 3 litre 2JZ-GE. While it may not have the same punch as the twin turbo, remember this engine's still pumping out 74 hp/litre - and in a luxury car that requires a dead-smooth idle and superb manners! And that doesn't mean that its torque peak is at stratospheric rpm - max torque of 298Nm is achieved at 4000 rpm, while that 166kW power figure comes in at 6000 rpm.

One of the ways that the engine achieves this is through stepless variable valve timing of the intake cam. Compared with the previous non-VVT-i engine which had an intake cam timing opening of 3 degrees BTDC and closing of 50 degrees BTDC, the VVT-i 2JZ-GE engine uses inlet valve opening timing of -12 degrees through to 48 degrees BTDC, with closing times of 65 - 5 degrees ABDC. The intake came timing is varied by this 60 degrees by the use of a movable piston that is placed between the outer and inner gear portions of the intake camshaft drive. Oil pressure to the piston is controlled by an oil control valve which is ECU driven. The ECU looks at engine rpm, intake air volume, throttle position and coolant temp before deciding on the optimal camshaft timing to be employed.

In summary the following intake camshaft timing changes occur:

• Idle: cam timing is retarded to give smooth idle;
• Medium load: cam timing is advanced to give improved fuel economy;
• Low load: cam timing is retarded to "ensure engine stability";
• High load, low to medium rpm: cam timing is advanced to improve torque;
• High load, high rpm: cam timing is retarded to improve volumetric efficiency;
• Engine started and stopped: cam timing most retarded;
• Low temperature operation: cam timing is retarded.

The 2JZ-GE engine is a "square" engine with a bore and stroke of 86mm. Its compression ratio is 10.5:1 and it requires fuel with a RON of either 93 or 95 (depending on the market in which it is sold). The connecting rods are made of high-strength vanadium steel and the engine uses short skirt pistons with minimal valve recesses in the crowns. Standard stainless steel exhaust double wall extractors (headers) are fitted and where required, twin cats are located immediately after the primary pipes. On the intake side a heat-resistant phenol resin intake gasket is used to reduce the conduction of heat to the intake system, improving cool air induction. For the same reason, the flow of engine coolant through the throttle body assembly is controlled by a separate thermostat, preventing the intake air being heated to a greater degree than necessary.

The standard engine management is very sophisticated. It incorporates electronic throttle control (ETCS-i), cruise control, and an immobiliser, in addition to engine control functions. The electronic throttle means that the ECU calculates the best throttle opening for the driving condition and uses a throttle control motor to provide that opening. Idle speed control and Vehicle Stability Control is incorporated into this system. Incidentally, on the GS300, a 3-speed electric cooling fan is used, with the two fan motors connected in series or parallel as required.

The 1JZ- and 2JZ- engines (all DOHC 24 valve in-line sixes) are available in four main complexions, as shown in the following table. However, as with most Japanese engines, the engies were available in various states of tune, depending on the year of release and the vehicle for which the engine was destined.

The 1JZ and 2JZ engines were first released in Japan in 1990-91. In almost all configurations the engines have been rated as shown in the following table. However, note that Japanese power figures can be a little rubbery - the Japanese agreed limit of 280hp (or, more accurately, 280ps) is frequently stated when in fact the power is higher than this, and engine tunes differ slightly depending on the market in which the car is to be sold. This explains the 4 per cent difference in the quoted power figures in this article for the 2JZ-GE.

Engine	Compression Ratio	Power at rpm	Torque at rpm
1JZ-GE	10:1	134kW at 6000	235Nm at 4800
1JZ-GTE	8.5:1	209kW at 6200	363Nm at 4800
2JZ-GE	10:1	172kW at 6000	284Nm at 4800
2JZ-GTE	8.5:1	209kW at 5600	431Nm at 3600

Conclusion

Over the years the Japanese have built some of the very best in-line sixes ever. Witness the L-Series classic from Nissan, followed by the famous RB-series of engines. The Nissan RB26DETT twin turbo might be the one to have when you're chasing 1000hp, but we reckon that the variable valve timed JZ engines from Toyota might be the ones to have for pure street performance...

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