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MIGClub Member
14,789 Posts
Discussion Starter · #1 ·
Fitting a Z22SE Airbox on a Z20LET

Please note that this is a guide only and MIG takes no responsibility for any damaged caused to yourself or vehicle whilst using this guide. If you are unsure how to do something leave it to the professionals. Your Insurance and warranty might be invalidated if this modification is done.

Why do this mod?

• More direct route to the turbo, thus decreasing pressure loss in the inlet and theoretically increasing power.
• The shorter route increases noise from the turbo making the dump valve more audible. (This is possibly why Vauxhall did not choose this arrangement as standard). The extra noise may or may not be desirable.
• Less heat soak due to removal of the metal crossover pipe, theoretically increasing power.
• Easier to change spark plugs as they are no long obstructed.
• Tidies up the engine bay.



Parts needed

• 2.2 Airbox part no. 9129077. This comes complete with everything you need to fit including a new standard air filter. Retail £48.95 + VAT
• Silicon hose - AFM to Turbo. 70mm reducing to 63mm through 90 degrees. Samco part no. RE90.70.63. £19.50+vat.*
• Silicon hose - Airbox to AFM. 70mm to 70mm through 45 degrees. Samco part no. E45.70. £22.50+vat.*
• Pipercross crank case breather filter part no. C9025. £19.23+vat.
• 1m 20mm ID crank case breather pipe.

Samco hoses can be ordered from Merlin Motorsport on 01249 782101. Prices are correct at time of writing.


1. Remove the following parts - Standard airbox, crossover pipe, air flow meter (AFM) and all hoses as far as the turbo inlet. Cover the turbo inlet with a cloth to stop anything from falling into it. Jubilee clip bolts are usually 7mm. Make sure you disconnect the AFM from the loom, and remove the breather pipe from the underside of the crossover pipe.

2. Open up the airbox (strangely uses trox bolts instead of the usual metal clips) and remove the filter element. Connected to the inlet and outlet of the box you will see two extra tubes. These are designed to reduce noise, but at the same time, they cause a restriction to the air flow. Remove both of these parts by pressing down on the clips and levering them out of place. This can be a bit fiddly. Refit the standard air filter element and reassemble.

3. Fit the 2.2 Airbox - it sits directly onto your existing mountings. However it is worthwhile de-restricting the airbox before it is fitted. I recommend keeping the standard panel filter as aftermarket filters contain oil to help hold particles. Many believe that this oil is what causes AFM failures.

4. Cut down the 90 degree silicone hose as much as you can leaving about an inch either side of the curve radius. Ensure all debris is removed, then fit the 63mm end onto the turbo inlet. Now fit the AFM the correct way around (note the arrow on the unit) to the other end of the hose and align it as in the photos.

5. Hold the 45 degree silicone hose over the assembly and look down on it. You should be able to see where you need to cut it in order to make it fit. This can be done easily by eye.

NB. To cut a silicone hose straight, fit a jubilee clip over the pipe and cut along the edge of the clip. Always make sure that there is no debris left in the pipe and around the cut edge before fitting.

6. Fit the final pipe into place. You may need to fiddle around with the pipes, bending them in places in order to get them to connect together correctly, as it is a tight fit.

7. Once you’re happy that everything is lined up correctly, refit your existing jubilee clips and tighten, making sure you do not over tighten.

8. The AFM wiring will no longer reach the AFM, so this will need to be extended.

If you are lucky, your loom may have excess wiring inside the loom tray at the rear of the engine. To check, remove the top of the loom tray at the rear of the cam cover and locate the AFM part of the loom. If there is enough slack to reach the AFM, make a new exit from the loom tray approx 1" from the end and make the existing loom exit here. This may give you enough length of cable to plug straight in.

Alternatively, you can simply cut the loom and extend it (recommended). Make sure you do one wire at a time so that you eliminate the risk of connecting the wrong wires together, cover all new wiring in black insulating tape. Try and route the wires away from moving and hot parts.

9. The breather pipe that connected the back of the cam cover to the crossover pipe no longer has anywhere to go. If you really want, you could plumb a connection into the 90 degree silicone hose, but 1 suggest allowing these fumes to breathe to atmosphere. An advantage of doing this is that your inlet will stay cleaner, less risk of contamination on the AFM element and a slightly lower induction temperature.**

From the back of the cam cover, fit the new breather hose to the breather outlet and at the other end of the hose, fit the Pipercross crankcase filter. The hose may be a tight fit to the back of the cam cover, so hold the end of the pipe in boiling water to soften it up before fitting. The filter can be positioned where you wish – the photo below shows a suggested location.

Once complete, give the car a test drive. You should notice an increased in induction, turbo spool and dump valve noise. You may also notice that turbo spool-up is quicker and an increase of power.

* The use of silicone hoses is optional although recommended. It is possible to use the pipes removed from the original setup instead, although they require some modification. It is also unknown if these pipes are designed to endure the extra heat experience by connecting them directly to the turbo inlet. If you on a budget, certainly give this a try. Note, that making any modifications to these pipe will mean that it will be more difficult to revert back to the standard setup at a later date.

Z22SE Airbox using original hoses from standard setup.

**Please note: that at the time of writing, we are unsure if venting the crank case fumes to atmosphere would be an MOT failure. If it is, it may be necessary to revert back to standard for your MOT. This is not a problem as it would take no more than 10mins to revert back – just keep all the old bits somewhere safe.

Many thanks to Geoff Fewkes for his help with this article.
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