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V300 Debug & Enhance

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Please excuse the length of this post (my first).

Owning a 1999 Aristo V300 Vertex in Australia is a lonely experience. Mine is one of three, brought in as personal imports. The government here tightly controls Jap imports, bowing to pressure from the majors. Lexus/Toyota in Australia refuse to help. Dealers are threatened with de-registration if they are caught even selling spares, let alone buying or selling an import.

After 2 years of driving, I can offer the following:


1. Drive-by-wire throttle suffered increasingly regular failures until throttle position sensor replaced, lightening wallet by AUD$650/BP250. Turns out to be known fault with local Lexus GS300 also.

2. (major fault) Japanese spec not well suited to hotter Australian climate and lower grade fuel. Knock sensor often shuts down fun by dumping boost and retarding timing by 25+ degrees, whenever:

- Driving for longer than 30 mins in all conditions. Suspected to be caused by heat buildup in engine bay. Jap fix is to replace bonnet with carbon fibre unit with built in vents. Expensive. I removed the plastic tray under the engine with limited success. Next step is to design an air duct system to cool the turbo area, similar to brake cooling ducts on race cars. Anyone else have this problem?

- Air temp over 18C/75F

- Fully loaded with passengers and/or luggage.

- Using any fuel less than 98 octane (Oz spec). I've tried Nulon ProStrenth octane booster with some success. Down side was build-up on spark plugs, causing misfiring after 20,000km of use.

3. Warped RR brake rotor. Isolated problem, fixed by machining.

4. Radio frequency convertor and external electric aerial from Camry fitted.

5. Shocks and springs replaced with stock local GS300 units on arrival in Oz. Japanese owner lowered with HKS springs, same spring rate but so low that destroyed shocks within 5000km through continually bottoming out on bump stops.


The time has come to make a few improvements. I would welcome thoughts/ideas on the following:

1. Fit 18*10 rear and 18*8 front wheels with suitable tyres.

2. Replace rear steering unit with solid mount to reduce "nervous" handling characteristics caused by unwanted rear wheel steer.

3. Replace diff centre with limited slip unit from Supra, hopefully with slight higher ratio to improve acceleration and provide drive out of corners.

4. Deactivate the VSC. On the web I found after market units in Japan but at horrendous cost. The wiring diagram for the local GS300 shows a pinout on the ECU but I have not tried to find/exploit it yet.

5. Upgrade shocks and springs to reduce limo float feel and improve handling.

6. Increase power output by around 30-40%. Still exploring the best/cheapest ways to do this. Fixing problem 2. above is a prerequisite.

Any and all input gratefully appreciated. Thanx in advance.

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where do you get your parts from you ship in from japan

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Thankfully most parts are compatible with other local Lexus or Toyota models. The Toyota Supra has been a permitted import to Australia (along with the Soarer, Surf, Harrier, Nissan GTR, Pulsar GTI, Silvia, FTO and a few others) so there is an established network for the 2JZ-GTE. New legislation that comes into force 1 Jan 2003 will reduce import models and volumes by about 75%, thanks to the Australian car industry and their political muscle.

The only part I had to import was the throttle position sensor, which took about 3 weeks. Having 2 friends who work for Toyota Australia certainly helps (eg getting access to the Toyota Intelli-Tester).

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> Problem 2 is the biggest drama for me. Assuming ducting doesn't completely

> solve the problem, would you try water injection next? Any other

> thoughts as

> to cause? Is there a way to remap the advance curve to reduce

> pre-detonation

> while increasing boost?

The biggest cause of detonation or knock is

1: lack of fuel or

2: high air/fuel mixture temperatures.

Lack of fuel can often mean lack of GOOD fuel. I ALWAYS run the Supra engine on Super Unleaded which is a UK term for fuel at least 98RON.

95RON which is our normal unleaded fuel is absolute rubbish, so it DOES make a hugh difference.

2: Air/Fuel mixture temperatures are normally all to do with the temperature of the air. The air in a turbo charged vehicle is subject to extra heating through the turbo chargers, as air is compressed and molecules smash into one another causing heat. The intercooler attempts to cool this down again whilst maintaining the high air pressure.

So you have a number of problems.

The intercooler will only be about 60% efficient anyway. Meaning at best it can cool the compressed air down to 60% of the outside ambient air temp. A 100% efficient intercooler would cool the air charge down to exactly ambient. But even the best intercooler in the world won't help if the ambient air temperature is high. So if you live in a hot country a turbo-charged car has problems.

There are a number of ways to help the poor efficiency of the intercooler.

1: fit a larger intercooler, bigger volume has a better chance of cooling more air.

2: spray cold water onto the external fins of the intercooler to help heat evapouration

3: Make sure the ambient air coming in from the outside is as cool as possible. i.e. don't go fitting some aftermarket air filter and expect it to be as cool as with your stock air filter system. You need to make sure the air is as close to ambient as possible. i.e. not allowing the engine to heat up the air coming in, called heat soak.

4: duct cool ambient air to the external fins of the intercooler.

Ducting is a method of directing the incoming airflow to only go through the intercooler and not around the outside. Ducting must have sealed edges and corners etc.

It is NOT neccessary for the frontal area to be the same size as the intercooler area and the rule of thumb that it should be at least 1/4 the size.

SO!!! You don't have to go cutting great holes in the front spoiler but you WILL and DO need to make a good duct. Which is why the undertray of the engine is very important, not least of all for high speed stability but also cooling. Don't remove it expecting more air to get in. It won't! Plus your high speed stability will be affected.

However DON'T DUCT the incomming air to the air filter. These turboed cars are NOT RAM air systems. The ambient air intake must be placed in a cool but large volume of air so the car can suck as much as it wants.

Coming back to ducts. The best ducts are those that are smaller on the outside than the inside.

There's a picture in Maximum Boost by Corky Bell. A very good book to read on the subject of turbo-charged cars.

ISBN 0-8376-0160-6

I would have attached it but I don't know how.

> What process would you follow to increase power? Exhaust? Air

> filter? Boost

> control & FDC? Other?

Remove Catalytic converters and fit straight through exhaust pipe.

ONLY fit an aftermarket air filter if it comes with a kit to shroud the filter to prevent heat soak from the engine. Otherwise you might as well stick with the stock one. You may be able to fit a better insert into your stock system though. I don't know.

Boost can be raised easily with the addition of a simple bleeder valve fitted in-line with the turbo control pipes. Or an electronic boost controller will do the same thing with more control and flexibility.

Increasing boost will mean you hit a boost/fuel cut limitation so a fuel cut controller is next (

Larger intercooler or intercooler spray would be next. Or like me I've fitted water injection which inject water internally to the incomming air flow and mixes with the hot air.

There are so many things you can do but first you must sort out your fuel! ALWAYS use the best fuel you can buy.

Try fitting cooler grade spark plugs as well. That will help at high RPM.



Mr P.Betts

TRL Performance

the Automotive products division of

Temporal Reality Ltd

a DSP Design Consultancy.

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nice reply pete........ive taken alot of that onboard for my upcoming conversion B)

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Thank you for your extensive reply. I'll see what I can do about improving airflow to the intercooler. It's pretty well hidden away under the right headlight with no direct air path.

I always run 98RON fuel (Shell Optimax or Mobil 8000). As mentioned above, I even added octane booster to every tank to increase the RON to 101. Unfortunately it fouled the spark plugs pretty quickly and didn't resolve the pre-detonation problem. In Japan, premium unleaded is 100RON, which is the diet recommended for the 2JZ-GTE.

On the Japanese Aristo Club website I stumbled onto an entry that talked about high ambient temperature build-up (80C/178F) towards the rear of the engine bay on the turbo side after extended driving. I assumed this exacerbated the problem of intake air being heated by the turbo. Toyota has added a 2" square plastic duct into the undertray (looks like an afterthought) that directs air onto the turbos. My thought was to increase the air flow onto the turbos with a bigger duct, then replace the undertray.

The Australian HKS site lists 2 models of front-mount intercooler kits at AUD$3,000 or AUD$4,000. (There are approx 3 Aussie pasos to the British pound). Water injection kits are about AUD$2,500. Does this sound about right to you? If I fix the predetonation problem I will look at buying the boost controller and FCD from you. Can you tell me a little more about the DCX Infinity. Also will the SLD allow the cruise control to be set above 110KMH?

The Japanese Aristo owners seem to change the 2 rear mufflers as a few effort. I don't know if this is for show, noise or performance.

How many heat ranges cooler would you go with the plugs? The standard plugs are NGK R BKR6EKPB 11's.

Again, thank you for help.

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>>In Japan, premium unleaded is 100RON,

>>which is the diet recommended for the 2JZ-GTE

I know. But none of the 2JZ-GTE Supras in the UK have a problem with 98RON Optimax. I run 18psi with no problem.

>high ambient temperature build-up (80C/178F) towards >the rear of the engine bay

Same deal with the Supra. The UK Spec car has a bonnet vent, ducting air to the turbos.

>>My thought was to increase the air flow onto the turbos

>>with a bigger duct, then replace the undertray.

Yes, or come from the top down with a bonnet scoop.

>Water injection kits are about AUD$2,500.

ERL sell the Aquamist system which when I last looked was about £350, so just under $1000 AUD

You're being done!

with an Australian distributor....

MRT Performance

(Middleton Rally Team)

Professional Rally components

82 Belmore Street

Ryde NSW 2112


TEL: +61 2 9809 2110

FAX: +61 2 9809 2286



Contact: Brett Middleton

>>Can you tell me a little more about the DCX Infinity.

Can you mail me privately.

>>Also will the SLD allow the cruise control to be set above 110KMH?

Yes, the DSC+SLD will allow this, but again can you mail me privately on this.

>The standard plugs are NGK R BKR6EKPB 11's.

Go for the 7 series.




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:o ..........WOW.

pete the Tuning encyclopedia :D

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Just an update on the heat related performance problem identified in my original post.

Along the back edge of the engine bay is a rubber seal (looks like a door seal) that seals the engine bay when the bonnet is closed. Remove the rubber seal (carefully, it tears easily as I found out) and hey presto. Trapped heat in the engine compartment can now escape, reducing heat soak that translates into more sustained performance.

The only down side is a very marginal increase in engine noise. And hey, that ain't a bad noise.

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Remove foglights, the right fog on the V300 is blocking the intercooler.

I replaced mine with some gauze/wire air will blow directly onto the intercooler now. Cheap and effective.

Worrying to find there is damage to sparkies with octane booster, I run TRD iridiums so will change them soon.

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