I managed to find a used Greddy Turbo kit and noticed that the housing already has a built-in restrictor. Is this something normal? Would I still need a restrictor?

 

Yeah , you still need a restrictor . That one will allow too much oil through.

 

My turbo guy sees a lot of TD06H turbos and recommends a 2.5mm restrictor for them...(Greddy = TD06H)

 

that sounds too big ......

 

https://www.rx8club.com/series-i-maj...ght=restrictor

 

Yeah, he told me my current 1.5mm restrictor was too small to cool it properly, recommending a 2.5mm restrictor. I mentioned concerns about blowing seals, but he's adamant that he hasn't seen any issues and it's the way to go.

My turbo's coming apart this week so the level of coking should give some indication of whether there was enough oil flow through it. If the coking is bad I'll go 2.5mm. If it's fine I'll go 2mm.

I've also found a crack in my turbine housing between the WG port and the turbine wheel outlet. Obviously caused by heat. It could be due to lack of oil or from running AFRs of low 12s for the last few months. More oil would probably have helped avoid this though.

 

I better post up my coking results - looks like that link above is saying 1.5mm (0.065") is possibly too big.

 

A restrictor is not the way to go, read any turbo manufacturing documentation and they will mention specifically not to use them. Not to mention that these turbos are not designed to see the oil pressure that they do in a rotary. An oil pressure regulator is the way to go, that is what I did.

 

Maybe he hasn't but ths forum has ...... how many of those TD06hs were on rx8s ?

Don't worry about it , my turbo did the same and was still going strong after 100,000 odd kms since i first noticed it .

 

May be a silly question..... But is it possible to buy a feed line with a restriction built into it?

 

Yes you can buy an inline restrictor from ATP.

 

Okay thanks, I'm trying to remember from 5+ years ago when I bought my kit; but I inquired with the vendor I purchased from about restricting the oil feed and he told me that the line he was providing was already properly restricted and wouldn't need any additional restriction from what was provided. More out of curiosity than anything; haven't had any issues in regards to my turbo seals.

 

Yeah at stock oil pressures they seem to last okay depending on mileage and use. But even then I know a few Greddy guys who went thru a rebuild every 20-30k.

 

Yeah I'm at around that 20k mark, only thing to fail so far is my WG actuator diaphragm is leaking under higher boost but that is my own fault because I accidental put a little to much pressure through it while checking for boost leaks. Ironic really

 

I've read that ball bearing turbos are much more sensitive to oil pressure than journal bearings. For a TD06H journal bearing turbo it's hard to justify the added complexity/expense of a full blown oil pressure regulator setup. Many OEM turbo cars use restrictors rather than pressure regulators, so while it may not be the ideal solution, it's often the most practical one. Apparently it's more common to run the restrictor at the top of the oil feed line, at the far end from the turbo. Not sure what benefit that gives - mine's at the turbo end.

I take the point that the 2.5mm restrictor size may be good for other cars, but may feed too much oil to be drained effectively in the Greddy low mount position.

I re-checked my restrictor size this morning and turns out it's actually about 0.75mm. Could have sworn it was 1.5mm, but never thought to measure it during initial install. My turbo has been in for a year with this small restrictor, and done about 10k miles. After the tear down this week the results are that the bearing housing needs replacement, and there's a lot of coking in that specific area, indicating that there was definitely not enough oil. The take away point is that you should not run less than 1mm restrictor. That's already pretty common knowledge but nice to confirm. I'll be drilling mine out to 2mm and if it leaks, swap it out for a 1.5mm restrictor. Apparently with this turbo if it leaks some oil due to too much oil pressure it doesn't typically damage the oil seals, so no long term damage with this approach. Not sure if this is the case with ball bearing turbos.

 

 

Yup, that was the exact word that came out of my mouth.

$200 later, I have a new bearing housing installed. I'll be measuring EVERYTHING before I install it from now on. Sheesh