This article was first published in 1999.
We've featured Nick Tsemitsidis' immaculate Supra turbo back in the early days of AutoSpeed
[See "Blood Rush"]
, but since then he's gone stir-crazy building up a mega-horse street engine. Yeah we know, pretty well anyone can make big power by fitting a massive turbo. But what makes this engine so vastly superior is its wide spread of torque, instant throttle response and bullet-proof reliability. Recollecting the days of the old stock-internals motor, Nick claims that the new 400-plus horse engine also returns similar fuel economy (around 12 l/100km around town and 9 l/100km on the highway).
And that was Nick's goal from day one - to end up with an everyday practical powerplant that pushed the heavy 2-door Supra very, very hard.
He'd received quite a lot of guidance and info on modifying Supra turbos through the Suprasonic website
and he drew a lot from their experiences. Another great source of help came from John Smith (aka "Smithy") of J.S. Motorsport. John used to successfully campaign Supra turbos in the Australian Group A race category back in the early '90s.
But enough nostalgia, here's how Nick's street motor all came together:
Ex-racer John Smith had an ex-'91 Bathurst race engine (minus its turbo, manifold and injection) lying around in storage, and had offered it to Nick a few years back. At the time Nick thought the price was a bit steep, and instead offered to buy some of the good bits off it - but to no avail. It wasn't until early this year the price of this complete engine was re-negotiated down to a more handsome amount of A$4200. Apparently the 1991 new price straight out of a crate was around A$60,000!
It arrived intact but in certain need of a freshen up, so it was immediately sent off to a reputable local engine builder - Stan Keen. Nick laughs when he remembers when engine was pulled down, Stan was "frothing at the mouth over the head studs"! And as more of the pieces were being pulled off, it was obvious some high-grade engineering had gone into the race engine. This included a 9-litre capacity magnesium oil sump and revised mechanical oil pump (around one-third higher flowing) to ensure reliability.
Another significant difference in the oiling side of things is that the turbo oil return line is fed into a lower part of the block.
Spinning with Swiss clock precision, there's also a super-strong steel crank that had previously proven capable of revving hard all day under race conditions without hassles.
Nick says the engines used in the cars raced in the '91 Bathurst race were totally reliable - except for one niggling power steering problem. A little surprisingly, the bottom-end uses only 2-bolt mains, but neither Nick nor any of his contacts has ever heard of problems in this area.
Standard-looking conrods are used that have since been converted to run fully floating centres, along with high quality rod bolts.
Mahle/TRD forged flat-top pistons (with significantly shorter skirts) were machined to accommodate standard Toyota rings, in order to improve potential engine life. The static compression ratio works out to around 7.7:1, taking into account the thinner-than-standard 2mm HKS metal head gasket and slightly machined head and block. This relatively high compression ratio is one of the main reasons the engine is so responsive and flexible off-boost. Note that on the other hand, the 1991 race engines used to run a low 6.6:1 CR, purely for optimum high-boost top-end torque. One flaw of most 7M motors is their tendency to blow head gaskets. This has been proven to be fixed by simply tensioning up the head studs more than standard - but not too much!
The twin cam, 24-valve alloy head came with a vastly different inlet path to allow for increased flow, extensive porting, slightly different standard sized valves (possibly sodium filled) and heavier-duty high-rpm valve springs. The only alteration that Nick has done is having the chambers cc'd.
The cam specs are unknown at this stage, but they are TRD products that deliver a lot more lift and overlap than standard - you only need to hear the engine idle to confirm it!
At the end of these are timing gears constructed from nothing less exotic than titanium, and a non-standard timing belt is used (although the standard belt just fits). As we implied earlier, top quality head studs are also taken aboard. Prior to assembly, the engine was also fully balanced.
On the intake side, the manifold is the same as stock, but it has been port-matched to the head and had its throttle body flange bored out. Overall, quite a lot of material has been machined out of the casting.
Because no turbo unit came in the A$4200 package, Nick retained the services of the one fitted to his previous engine. Adelaide Turbo Services tweaked the flow capability of the CT28 turbo by fitting a T04E compressor wheel, back-cutting the turbine wheel and giving it some custom porting. However, we're told the CT28 - even in modified form - usually starts to run out of puff at around the 400hp mark. In its current configuration this poor CT28 has to spin pretty hard, as Nick asks for some fairly major boost pressures. A peak of up to 27 psi can be seen on cold days, but it is capable of holding a constant 23 psi through the four (automatic) gears. Recently, the standard airbox was pulled off and replaced with a freer flowing HKS Super Mega Flow air intake kit.
The Supra's new air-to-air intercooler system is very swish to say the least. Instead of turning to a cut-down truck intercooler or some other one-off custom installation, Nick picked out a core from the HKS Japan catalogue. Measuring approximately one meter in length, the beautifully-constructed polished core has excellent heat-exchange properties and it nestles perfectly in the space in the car's nosecone.
Extending from its inlet and outlet pipes, is an HKS intercooler pipe kit from the US (that's been HPC coated) to channel induction airflow without restriction. The crossover pipe leading into the throttle body is an item Nick simply had to have. Sporting the high-profile HKS nametag, this piece of art that is apparently now very rare - so it was impossible to pass up the opportunity of having one!
Another gotta-have item was the HKS sequential blow-off valve whose unique bellow guarantees the attention of pedestrians whenever Nick backs off the throttle. The throttle body had been considered for replacement until it was realised that its reasonable diameter (60mm) is enough to flow for the engine's needs.
HPC ceramic coating has also been applied liberally to various parts in the name of thermal efficiency and cosmetic appeal. Pieces that have been treated include the rocker cover (which is also ground back for a smooth appearance), the inlet manifold and the airflow meter.
Interestingly Nick chose to steer clear of aftermarket programmable injection. Through his contact with Reg (the President of the Canadian Suprasonic club), he instead opted for a simple-to-fit upgrade kit comprising a larger diameter Lexus V8 airflow meter and 560cc RC Engineering (Lucas) injectors.
The kit was installed without a hiccup and it wasn't long before the factory computer had learnt its new working conditions. By retaining factory management, the standard 6500 rev limit is still imposed, and that means the engine must be producing large amounts of torque. To maintain the correct mixtures throughout the load range, a custom adjustable fuel pressure regulator is plumbed into the injector rail to provide 55 psi pressure at idle.
Making over 400hp, it was also decided to ditch the standard electric fuel pump in favour of a large capacity Bosch Motorsport pump, just to be on the safe side.
Out of interest sake, the six 560cc injectors were installed as a replacement for the massive (800-1000cc) "garden hose" injectors that had come fitted to the race engine. So boy, those race guys must have thrown in a heap of fuel!
The only other change to the factory management system is the inclusion of a piggy-back fuel cut defender. Nick says the airflow meter/injector kit was supposed to overcome the factory fuel cutout, but he found that if he wanted to go up to 27 psi he needed to keep the defender module as previously fitted. The ignition is 100% stock other than a set of cold NGK-R spark plugs that help to ward off detonation.
In the future, there is still the possibility of going for programmable injection (such as MoTeC). You see, Nick's trying to convince his friend Dino (the owner of the blue Supra turbo that we've also featured previously) to have an aftermarket system fitted and tuned on an engine dyno. That way, Nick can grab the right fuel and ignition maps without having to torture his engine on the dyno! Very cunning.
With the engine barely run-in, Nick set off to see what the new engine had by way of performance. Unfortunately it seemed to ping quite a lot, preventing any real testing. Nick spoke to a few people but up until this moment, the solution has been to run a 50/50 mix of premium unleaded and Avgas. The introduction of a leaded fuel to a factory exhaust gas oxygen sensor often results in a faulty sensor, but Nick plans on keeping an eye on it and replace it if he needs to. At the time of writing, the cam timing was also about to be checked in relation to the detonation problem.
So how fast is it? The car in its previous form had managed an official 13.5-second pass at 108 mph, and Nick had the realistic intention of cracking 12s with the new motor. All things seem to indicate this will happen, but a makeshift timed run with a G-tech indicated a 13.1. Nick will probably kill us for telling you about this time anyway, but this was done with two people onboard, only 18psi, no Avgas, a full tank, very poor traction and a headwind. True! Rest assured at the next local drag meeting he'll be there to prove that it does in fact pull 12s!
Obtaining a realistic power-at-the-wheels figure is next to impossible. Even in its previous guise, the car would wheel-spin wildly on the rollers - let alone now. However, based on information from the 'States and previous engines, Nick (who's a realist) estimates it has around 430-450hp at the flywheel. And as he points out, it's torque output is the major advantage over other modified 7M-GTEs that might possibly have more peak power.
Throttle response from the new 3-litre capacity turbo engine is excellent. Despite its lumpy cams, the use of high-ish compression, a mildly sized turbo and a well-sorted EFI system allow for instant acceleration - bearing in mind the auto trans kicks down as well. When we rode in the car, we loved its supreme flexibility (for a turbo engine) and the controlled rate at which torque was delivered. There's no sudden whack-in-the-back, just a relentless urge that seems to go on and on. Boost came in as early as 3000 rpm under normal driving loads, and you could hold the throttle in one position, allowing boost pressure to gradually compound and accelerate you along.
Lastly, the engine sounds magnificent. There's a deep cam-induced burble at idle, that builds to a busy-sounding rush of airflow when the boost needle starts to move. But when that needle is swung over to around 27 psi, you're senses suddenly change from taking in the sounds to watching the road in front - with wide eyes!
Adelaide Turbo Service
+61 8 8377 2511
Stan Keen - Turbo Tune
+61 8 8297 1030
+61 2 957 9577