Vauxhall did a good job on the GSi from the factory. So much so that Coupe owners often swap their front bumper for the GSi item! It’s really a matter of complementing the styling than transforming it. An Irmscher or Steinmetz cross hatch grille is a good start, while both companies do a range of top quality spoilers and skirts. Also well worth a look are the Reiger and Lumma products available from Online Autosport. If your budget doesn’t stretch that far, though, excellent results can be achieved by removing the bump strips and badges and going for a smooth look.
2. ENGINE TUNING
Regal Autosport offer their EDS IPF Flash tool for the GSi, which you can connect to your PC to download a variety of maps at home, dependent on your car’s specification. With no other modifications, a Phase I map can see you up to 235bhp. Phase II tuning involves adding a high flow intercooler and hotter map, which will give another 20bhp. Swapping the standard turbocharger for one from a VXR can then lift power by a further 20bhp. The Regal maps work in conjunction with the car’s traction control system to limit boost in first and second gear, improving driveability. Following on from this, bigger injectors can be fitted to increase power further. Beyond this level of tuning, many Astra owners are now fitting the Z20LEH engine from a VXR, which is a tougher unit and will run on the standard GSi management (the VXR has a full CAN Bus setup and is not yet transferable). If you want to crack the 300bhp barrier, this is something you should seriously think about, as the VXR also benefits from the excellent M32 six-speed gearbox, which is far superior to the standard GSi five-speed. Uprated internals, tubular manifolds and bigger turbos can see you reach over 400bhp, but you’ll need deep pockets to get that far.
The GSi comes with 17in ‘Snowflake’ wheels as standard, which are good looking for a factory rim. 17s are generally considered the best size for the Astra if performance is your number one criteria. The most sought after upgrade for the GSi are wheels from later VXRs, with 18in and 19in options available both new and secondhand. They can be very expensive though and, while 19s look amazing, the car will develop a tendency to tramline. In terms of aftermarket alloys, try Compomotive, OZ or Speedline for a classy motorsport look.
4. INDUCTION & EXHAUST
There are plenty of improvements to be made here. A simple panel filter swap is a good start, but for the ultimate in breathing mods, check out Regal Autosport’s Dbilas range. Their Flowmaster Dynamic air induction kit uses a cast metal airbox and scoop, along with a K&N panel filter. This item can net you 10bhp. Also from Dbilas is a brand new inlet manifold, which simplifies the air intake, increases low down torque and eliminates flat spots. The complete exhaust system can be upgraded too. Removal of the pre-cat is a must, with replacement front pipes available, along with sports cats. There are numerous options for exhaust systems, with one of the most popular choices being Scorpion’s 57mm stainless cat back item.
The Astra handles well from the factory, but there’s definitely room for improvement. LMF can supply Bilstein adjustable dampers and Eibach Pro springs, which are considered the ultimate upgrade combination, while companies such as Spax do excellent fixed rate and adjustable kits. Many Vauxhall owners also recommend Avo and Koni kit highly. If that’s still not enough, how about a set of Whiteline anti-roll bars from Courtenay Sport, which are reported to improve the Astra’s cornering control considerably.