When I first noticed my boost creep I was unsure of what was going on with my turbo as all this was quite new to me. However, after some extensive research and a few road tests I realised my TD05 turbo suffered from boost creep. As boost creep occurs due to not enough exhaust gas flowing out of the wategate from before the turbine wheel, I was left with three options to solve my problem. 1 was to fit a more restrictive exhaust 2 was to simply port out the standard wastegate hole to a larger diameter and 3 was to completely block it off and modify the manifold to use a much larger external gate (this is the expensive option).
Since the fitment of my 3 inch exhaust was due to wanting more power, I wasn’t about to go fit restrictive mufflers onto my exhaust and since Australian legislations state that aftermarket external wastegates are not permitted for street use. I was left with no other option but to modify my standard internally gated setup to have a larger hole. The answer was to port.
Before I began I thought it threw and not long after a second turbine housing was purchased. This ensured my car would not be off the road for the whole period of the port job as It is very time consuming. After having a look at the newly purchased second hand housing it became very clear to me on what needed to be ported. Some measurements were taken and the standard waste hole was measuring in at approximately 20mm inner diameter and the flap to cover was 30mm, this left the flap with 10mm to seal around the hole. Since I wanted to make full use of the ability to port, the flapper needed to be modified or replaced the with a 34 mm exhaust grade washer as the new flap. Now this would leave 14mm to cover the hole, but since I only need about 3mm on either end in order to not leak exhaust gas, I would be left with 8mm to port (that being 4mm on each side of the hole). This being a 40% increase in diameter over that of standard.
After some further observations, I noticed that the path leading from the manifold to the wastegate was a near 90 degree turn. This being quite restrictive to flow I decided that once i began porting I would also concentrate on knocking off the wall leading to the wastegate entrance. This would make the exhaust flow much easier whilst not having to take such an abrupt turn.
Equipment needed:- Safety glasses and gloves
- Metric spanner set
- Vice
- Rotary tool with carbide bits for grinding and other 80grit bits for smoothing.
- Solvent (to remove carbon build up)
Method:Safety being priority, first thing is to dress appropriately, remembering to wear safety glasses and gloves as a bear minimum.
Before i began, this is what the o2 housing looked like. As can be noticed the wastegate hole can not yet be seen.
After some significant porting the progress began to look as such. You should notice the wall blocking the entrance slowly being removed.Dremels take forever! I found that music helped pass the time. At this point I was about 5 hours in.
Continuing to port, focusing on the wastegate entrance, just porting away with the rotary tool and some carbide attachments. After about five hours, the entrance was complete and my attention was now turned to the entire inlet as an oval shape was obtained from porting to one side. To reobtain the conical shape like from standard, I began focusing on the rest of the inlet. It can be seen that the wastegate is now easily accessible with far less effort. Here is a picture for comparison.
After completing the inlet my focus went onto the wastegate hole. So I began porting to achieve the calculated 28mm which I was after. This step took about 4 hours as I was using a dremel and being quite cautious, remembering to continually check the size of the wastegate. By comparison, the difference can be seen.
Now that the 28mm was finally achived, progression took place to the final stages of my project. A new 34mm flapper was purchased and shortly after it was installed. Fitment took about 2 hours and here is the end result.
The porting and fitment on the 34mm flap is now complete and the o2 housing is ready to be fitted onto the turbo.
To remove the turbo the following steps were taken:
1. I drained the engine oil and coolant from the engine to prevent major spillage which could occur when removing the coolant and lubrication lines from the turbo.
2. Disconnected the dump pipe (beginning of exhaust system) from the turbine housing (also known as o2 housing), and oil and coolant lines from the turbo.
3. Removed the bolts which connect the turbo to the manifold to release it then pulled it out from the engine, there are four bolts in total.
4. Once removed from the motor the band clamp from the turbo was removed. This separated the o2 housing from the rest of the turbo.
5. Now that the o2 housing was out, fitting the modified one was a simple reversal of the steps above.
Conclusion Porting the turbine housing solved my boost creep completely. The car now has the ability to hold set boost to redline (peak RPM). This project was simple and cost effective however very time consuming. Enjoy