I'm bored at work....working my notice before I start a new job
So thought I'd type this out; Nothing intersting for the majority but a good first read for new Z20LET owners.
Z20LET Tuning Guide Basics
This is the engine in the Astra Coupe Turbo, GSi, Zafira GSi and Sri Turbo.
They all produce the same power. Some will have more updated ECU software than others depending how old it is, this is however not an issue.
Air box modifications
These are what most people start with, there are many induction kits out there; The BMC CDA and the APEXI air filter are some used. However the general consensus is that it’s cheap and effective to do the following;
Derestrict the air box; this involves removing two pipes from the air box and is about 10 minutes work, there is another guide for this.
Add a Vectra C inlet pipe; again a simple mod and costs a few quid from a Vauxhall dealers. Part No’s are Main Pipe 9177099, Adaptor to Air box 9177104
Get an up rated Panel filter; Ram Air Filter, K&N, Pipercross etc.
Depending on how far you want to take your tuning, depends on how much of your exhaust you will replace.
If you’re going above stage1 then you will ideally need to replace your entire exhaust system. This consists of; Cat back (back box and centre pipe), Precat replacement pipe and main cat.
Be aware that Astra Coupe Turbos’s before 2002 had an all in one piece precat and main cat so you will either have to replace both the pre and main cat or have bits welded to your existing one.
The two main exhaust manufacturers used are Miltek Exhausts and Blueflame Performance – both can be mail ordered. Both sell complete\part systems to bolt onto your car; including sport-cats…which allow more gases to escape the exhaust by filtering less but still allowing MOT’s to pass emission tests.
Again if running higher than a typical stage1 you will need to change your intercooler. Two types exist FMIC’s – Front Mount Intercooler and SMIC’s – Side Mount Intercooler.
They both do the same job by reducing inlet temps and allowing more air to the turbo. There are arguments for and against each manufactures design but the general feeling is that they are all better than the poor one fitted as standard to the LET. Manufacturer’s include; Courtenay\Regal\Pace.
The most tried and tested spark plugs on the LET have to be NGK Iridium BKR6EIX. These are one grade cooler than standard plugs and allow for a better spark. The standard plugs in the LET are the same as what’s used through out the majority of the Vauxhall range so aren’t the best.
Get these from www.sparkplugs.co.uk . These plugs have been used on stage3 and above successfully.
This is when the software on your ECU is changed to cater for your mods and allows more aggressive settings to achieve better bhp/torque etc.
Different manufacturers have different levels of tune for different modifications and the trust worthy ones will only let you have the right map with the required engine mods.
There is now a variety of Vauxhall tuners;
Always read up before going to a tuner and see other member’s opinions; this way you know what to expect.
Also a good tip is; “you get what you pay for”.
There are a lot of other tuners out there as equipment becomes more readily available. Some are good, some are bad – so choose carefully when you give them your pride and joy to tinker with.
The way I see it is a tuner that will tune any car brought to them can not have as much experience as one that specialises in a particular make; Vauxhall’s\Volkswagens\BMW’s etc. They more likely only have generic maps and they will not cater for your mods etc.
There are many now available; the bargain of the century has to be the Z20LEH Turbo. As used in the Astra VXR which includes solenoids, actuator and manifold. This will allow a remap with more boost to be used, so is a great upgrade. This is 99% the same fitment as the Z20LET’s turbo so is a basic swap over for a competent mechanic.
There are plenty of other mods out there;
VXR Injectors, Water Injection, nitrous etc... It all depends how deep your wallet is.
A couple of links here for some more good information on turbo charging. They include the basics so that you can understand how your turbo works, to more advanced mapping of aftermarket turbos.
This website is particularly interesting with different pages for beginners, novice and advanced information: