Compressor housing repair

[JLGsDad]

I've just got a cast aluminium compressor housing that has been machined to take a bigger wheel. However, I'm not convinced that the profile is accurate enough; the gaps between the wheel and housing may be too large.

When I get chance I'll check the clearance by putting a soft material such as paint on the housing and abrading it with the wheel. I had 0.3 - 0.4 mm as a working clearance.

Getting another housing isn't an option. Clearly, any form of filler is a poor substitute for aluminium, not least through the risk of it breaking off, and I have to take great care not to damage the compressor blades. However, if push came to shove, is it feasible to profile the housing, for example by using JB Weld?

[JLGsDad]

Thanks.

The machining wasn't done for me and, even if it was, I can't see an easy repair if they've machined too much away.

What clearances do you think there should be?

I had a quick look and saw that Belzona products are available (the name is for the manufacturer and individual products are specified by a product number), although to say any of its fillers/glues isn't cheap is a bit of an understatement.

That abradeable coating is interesting. I'm not surprised that no-on else followed suit; the cost is prohibitive for the competitive car turbo market and it does have disadvantages.

[JLGsDad]

Thanks. Paint would certainly be easy to apply and sculpt/abrade to shape, and if there is any interference then it would wear away rather than damage the compressor wheel lips.

However, I suspect it won't last or adhere for as long as I want at the temperatures I expect the housing to get to, particularly when heat soaking after use (I've not seen any figures though). If I use the housing then it will be buried away and removing it to reapply a coating isn't practical. That said, I may be wrong and will do some research tomorrow when I have more spare time.

[JLGsDad]

Thanks.

I don't have a similar turbo to measure. It's for a journal bearing turbo with a new CHRA so I don't have to worry about sloppy bearings straight away.

I was using paint purely because it was softer and easier to remove. I'm building it up in several layers.

Unfortunately, getting another housing isn't an option; it's from a hybrid turbo that had a limited production run well over 10 years ago and has a large A/R unique to this application. I can get housings with the correct wheel profile but they all have A/Rs that are 15-20% too small; this is also true of the turbine housing, where the A/R is 25% higher than the standard turbo from which it was derived. .

Belzona is just the manufacturer's name and their products are defined by a 4-number code. The ones used for construction work are less suitable than the 1000 series, for example the 1131 used for bearing material (ostensibly a good choice as it is intended to wear, thus sacrificing itself to protect the wheel if rubbing occurs, but that may not be true for the aluminium of the wheel). I don't mind paying for quality, and, to be fair, per weight Belzona prices look quite reasonable; it's just that the minimum pack size is quite large so RRPs are all over the £100 mark. I can get some 1000 series at decent prices on eBay that may do, but not the ones that I think are best for the job. I've emailed them for a recommendation.