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Comprehensive tuning guide

"We look at the best tuning mods for the 1JZ engine."

The 1JZ engine was fitted to many models of Toyota and Lexus, from family oriented models to the more sporty models such as the Supra.

The 1JZ engine was a naturally aspirated 6 cylinder 2.5 liter engine with a variable valve timing system introduced in 1996 along with a revised cylinder head, making this the ideal base for your tuning project. A later turbo charged model was introduced with a GTE suffix and this makes an interesting proposition for the tuner.

Plan your 1JZ upgrades carefully, and don't be tempted to try and turbo a NASP block.

It was replaced in 2007 with the 4GR-FSE engine, to help meet ever tightening emissions regulations and requirements.

We are often asked if you can turbocharge a NASP 1JZ engine from people looking at the 2JZ setup and the 1JZ-GTE engine.

Whilst it is possible it is not really cost effective, especially when you can source a 2JZ or 1JZ-GTE engine with a turbo installed and drop this straight in.

If you insist on turbocharging you need to reduce the compression ratio, modify the head slightly and add an aftermarket ECU to control the fueling and turbo. Essentially you will commit to a costly strip down and rebuild of the engine.

The 2JZ engine is pretty much a drop in replacement and there are many around, or you could source the 1JZ GTE block as a replacement. So it makes economic sense to do an engine swap if you are looking for forced induction rather than converting your existing engine.

Fitting lower compression pistons, rods and sorting out the oil flow to the turbo are essential considerations, ideally you should also fit forged parts for added strength and resilience.

There is still plenty of potential to tune the 1JZ engine in it’s NASP form.

1JZ engine specs

Let’s look at the engine options in the 1JZ range and differences between them.

  • 1JZ-GE 1990-1996 lower compression ratio putting out 180bhp
  • 1JZ-GE 1996- revisions to the ignition system, higher compression ratio the VVTi variable valve timing and made around 200bhp.
  • 1JZ-FSE from 2000-2007 has a higher compression ratio thanks to the direct injection of fueling
  • 1JZ-GTE this was a turbo charged engined based around a twin turbo setup until 1996 when it was replaced with a single turbo. Both revisions of the engine made around 280bhp but the latter benefitted from a slightly higher torque output and much wider power band.

Weak spots, problems and issues on the 1JZ

Thankfully these engines are very robust and reliable but there are a few things to look out for. The VVT System can be problematic if not properly maintained and serviced, this usually causes a rough idle at first and later misfires and non starting issues. High oil consumption on older engines is usually down to worn valves and pistons, replace this if there is excessive smoke.

Spark plugs tend to foul up but it’s worth checking the ignition coils if there are misfires and other electrical issues.

You should be able to lift power to around 250bhp on most 1JZ engines, with the right modifications. Get a gas flowed cylinder head and port and polish the intake and exhaust to maximize flow through the engine. Fast road cams will give more peak power but if the profile is too aggressive you will suffer from a lumpy idle and the car will be hard to drive in traffic.

Power upgrades

A sports exhaust and high flow catalyst will also help the engine to make more power. If you balance the engine you can raise the red line and being an inline 6 this engine revs really freely and is silky smooth offering a lot of top end power.

The standard fueling system on the 1JZ is usually good for fairly substantial power gains and, unless you are adding a turbo should be able to cope with substantial power figures from the NASP engine.

A lighter flywheel will help the engine to rev more freely and we recommend fitting an uprated clutch when you start increasing the engines power beyond 250bhp.

A fast road cam is probably the single most effective mod for the 1JZ, adding around 20% more power. We have heard of people fitting the 2JZ cams to this engine, but you'll need to hone the journals to get them to fit. Porting and gas flowing the head, and adding larger valves also prove to offer a good return of power for your investment.

Most standard 1JZ airboxes flow quite well so we wouldn't recommend an air filter upgrade until you are pushing power levels around 30% more than standard.

Tuning the 1JZ GTE

The turbo version of the engine is quite a different beast from the NASP engine and is a great engine to work on. 17psi seems to be the safe limit for these engines, the standard ECU will be happy to around 15psi boost. If you want to go higher then you need a standalone ECU replacement or high quality piggyback ECU, we quite like the Greddy E manage Blue setup, thanks to it's flexibility and processing power and makes adding an aftermarket air flow sensor quite easy.

Adding a bigger turbo and good quality boost controller will take you to around 365bhp for 1.2 bars, around this point the air flow sensor starts to struggle and needs to be uprated. Most 1JZ GTE owners upgrade to a map sensor at this point.

A favourite turbo to upgrade to is the HKS2835 giving a little over 400bhp with the right setup and very little lag. The GT35R and 255 liters per hour pump, 650cc injectors will be good for 550bhp with the right engine management setup.

Many of our members mods on the 1JZ engine include parts from the 2JZ version, injectors, cams and fuel pumps are popular swaps.

A word of warning, the Decat option does seem to cause premature turbo seal failure. Many owners are reporting issues with the seals after a decat but no direct cause has been found.

Please help us complete this article, add your tips suggestions and corrections via the feedback form below, we do rely on user submissions to help keep our tuning tips at the cutting edge. Our forum is also a great place to go if you want more specific tips or are having trouble with your 1JZ engine tuning project.

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