Been looking for the original $2 T-piece mod for days and couldn't find it ... so I thought this post would be helpful for new SP owners wo would like to give it a try.
Original Set-up
In late 2001 and early 2002, the Mazda NB8B MX-5 SPs were modified pre-sale for Mazda Australia in Broadmeadows, Victoria by Prodrive (the UK company that bought out Tickford)
Prodrive followed the Allan Horsley, Mazda Motorsport manager’s modification plan including the design for plumbing in the Garrett GT2560R turbo’s actuator and the boost pressure take-off outlet in the piping just after the turbo.
The distance of the connecting hose between the outlet and the actuator was less than 200mm. The actuator therefore received its boost pressure reading from the very hot air spooled from the turbo
When an actuator senses the pre-set limit the actuator opens the waste-gate so that the boost pressure actually delivered was regulated to maximise at that pre-set value.
The boost pressure at the intake plenum has been estimated to be some 2psi below that pressure in the hotter area immediately after the turbo.
This happens because of the combination of pressure drop as air passes through the intercooler piping, and heat loss from the pipework.
What the T-piece mod Does
The T-piece mod changes the site of the boost pressure take-off point (going to the actuator) from its original position to between the BOV and the vacuum outlet on the top of the intake plenum.
T-piece mod does not change the pre-set point when the actuator opens the wastegate it just changes the place where the reading is taken..
When that reading is taken from just above the turbo the pressure drop meant that the actual maximum boost after the intercooler was up to 2psi less than that registering at the original take-off point.
The T-piece changes the location from which the boost reading is taken so the engine receives the full level of boost without that pressure drop impact.
Materials and Tools needed.
Sadly it’s not the $2 T-piece mod any more … more like a $30 mod.
Here is a list of the materials and tools
• 1 metre of 4.8mm (3/16th) 3.4 Bar (50psi) fuel line … Gates brand model 4219XL-SAE 30R7 available from Repco ($8.00 perM)
• Three way T piece to suit 3/16 hose (brass preferred) … Champion Brand model HC8 available from Repco`($8.00)
• Brass Hex taper plug 1/8 BSP around 10mm long…. Champion Brand model HC50 available from Repco ($5.00)
• 5 X Clamps for fuel line (8-10mm) eg Tridon nut and bolt clamp 5/16-13/32 ($1.40 each)
• Screwdriver for clamps
• 7/16 spanner for brass hex taper plug and to remove existing out-take piece
• Stanley knife
How to Do It
1) First, read all the way through and understand the instructions and importantly be sure that you can positively locate all the bits and lines that need to be accessed
2) Assemble your materials and tools
3) Find the black rubber vacuum line that runs from the vacuum outlet on the top of the intake plenum (driver’s side of engine of course) that runs between it and the BOV.
4) Measure 150mm down from the intake plenum towards the BOV on this rubber line … be bold and cut it there.
5) Fit a hose clamp to each of the ends you just cut and also to where the hose met the vacuum outlet
6) Take the T-piece and insert in the line so that it joins them and the naked end points horizontally to the passenger side
7) Don't do up the clamps you just fitted yet
Go to passenger side of engine ..find the black hose line between the turbo actuator (gold coloured canister) and the out-take on the silver piping just above the turbo9) Disconnect both ends of the black hose (we will replace the hose on the actuator with a longer hose that reaches across the front of the engine to the T-piece)
10) Using the 7/16 spanner remove the male brass out-take hose barb on the silver pipe
11) Fit the Brass hex taper plug to where you just removed the male hose barb using the 7/16 spanner …
12) Fit a clamp to the end of your new piece of hose … and fit the end to the intake on the canister (don’t cut the hose yet)
13) Do up the clamp securing one end to the canister (actuator)
14) Run the hose across the engine to the T-piece
15) Cut the hose to length, fit on a clamp and tighten all 3 clamps
16) Make sure all tools are accounted for and take the car for a test run.
Just be sure that you use always at least 98 octane fuel with this mod.
That’s it
Notice the positioning of hoses to and from the BOV…. This is the way that Mazda Australia delivered my car.
Regards
