Tuning guide for 25/45/ZR/ZS cars

I’ll describe how I’d tune these car and list some arbitary budgets in mind to spend on it and what you may achieve. I’ve assumed at each stage that all the previous stages have been done. These are my own views and so other people may disagree. Read up and make your own decisions.

N.B. I have assumed in this guide that the MAF sensor is good and doesn’t need replacing. These VERY commonly degrade over time and give poor performance. Make sure this is ok first before you start any tuning, otherwise you’ll just be masking the fault.

Step 1 –

Swap the injectors for injectors from a bubble shape 200/400/600. These flow more fuel and so increase performance. Adding the injectors also usually give a small boost level increase so please check the boost level and set it to a max of 19psi for reliable operation.

Cost £20-100

Power achievable ~130bhp/210ftlb

Step 2 –

Add a decat to remove the catalytic converter and this’ll improve the turbo spool a little.

Cost £0~50

Power achievable ~135bhp/210ftlb

Step 3 –

We are starting to run out of big wins in terms of performance. The 2 things that we’ve not yet done are the air filter and the exhaust. In my opinion the exhaust is more important than the air filter, but many people will already have fitted a cone air filter by now. Most people will plumb for green cotton cone filter such as the K4.80

Then we need to look at the backbox. There is only one silencer in the exhaust so a performance backbox can help release the final few ponies. Custom jobbies aren’t going to be cheap,

Budget – £100-200

Power achievable ~140bhp/210ftlb

Step 4 –

The finishing step is usually to remap the ECU to optimise all the other mods. You can have a remap done at any time but if it was my money I’d do it last of all so that I don’t need to do it again when I add another mod.

Budget – £150-200

Power achievable ~150bhp/230ftlb

This is about the limit of “cheap” tuning for the intercooled models. If you are after more power than this then you’ll need a bigger turbo.