Turbo help required.
Discussion
My Boxster has an after market turbo fitted, which has failed. The mechanic who currently has the car believes that this has been caused by the gravity driven oil return from the turbo being too restrictive in that a) it is too horizontal for gravity to have a proper effect, and b) the 90 degree bend at the engine end may cause a flow restriction. Both the kit supplier (US based) and the company that fitted the kit (UK based) say that they've never had a problem with any of the other kits that have been supplied and fitted. Does anyone with turbo expertise have an opinion? Picture below from fitting manual, not my actual car.
The pressurised inlet to the turbo is out of sight behind the gearbox top left. The return line is quite flat, which is why the concern has been raised. I've found a reference by Googling that suggests the return line should be no more than 15 degrees from vertical, and this is definitely more than that.
From what I've been told, 911 turbos use a scavenger pump to get the oil back to the engine, so I'm wondering if I'll have to do the same.
From what I've been told, 911 turbos use a scavenger pump to get the oil back to the engine, so I'm wondering if I'll have to do the same.
Edited by VladD on Monday 11th July 14:55
dom9 said:
VladD said:
The pressurised inlet to the turbo is out of sight behind the gearbox. The return line is quite flat, which is why the concern has been raised.
But if it is a pressurized inlet then the outlet doesn't necessarily need to be gravity fed, if there is 'enough' pressure.I'm just trying to think why yours has failed where others maybe haven't. Have you ever put a pressure gauge in the inlet and outlet lines of the turbo to check?
Will it run at all, safely? Could that be done?
dom9 said:
Bearing in mind that the head gain from a 10cm height differential (and it doesn't even look to be that) will be less than 0.01 bar, which is probably eaten up by frictional losses, I'd say you'd want some pressure from the other side.
A gravity return might be common on engines where the sump is well below the turbo (which often sits at head level), on an upright engine but your turbo looks all but inline with the flat engine/ sump, which means any G-forces or loss of pressure could mean zero oil return.
OK, so you seem to be of the same opinion as the mechanic, which is good in that there is some consensus. As I said earlier, the 911 uses a tank and pump to get round the issue, so I think I may have to do the same.A gravity return might be common on engines where the sump is well below the turbo (which often sits at head level), on an upright engine but your turbo looks all but inline with the flat engine/ sump, which means any G-forces or loss of pressure could mean zero oil return.
I should also point out that the car is my daily driver rather than a weekend toy and my commute to work is pretty slow with a bit of stop/start, so it could be that it's also the manner in which the car is used that has contributed to the failure.
Edited by VladD on Monday 11th July 15:36
jontysafe said:
The turbo oil feed will probably have a restrictor so there will be very little if any pressure on outlet hence gravity drain.
As mentioned on 911 you can put a small pump on drain line or treat the turbo as a 25,000 mile service item. A recon job by CR TURBOS isn't expensive.
Pump for oil drain is just another failure point as well.
That's interesting. The company who supply the turbo have quoted $995 for a refurb.As mentioned on 911 you can put a small pump on drain line or treat the turbo as a 25,000 mile service item. A recon job by CR TURBOS isn't expensive.
Pump for oil drain is just another failure point as well.
stevieturbo said:
Some details would help.
What type of turbo is it ?
How long did it run for in this configuration ? And did it run well, where there any indications of problems ?
You say it failed....exactly what failed ? That will very much tell you whether it is oil supply ( and drain ) related or not, but may require the turbo to come apart.
And yes if there have been symptoms of poor oil draining then a scavenge pump would be an option. But you dont seem to be saying there have been any such problems ?
And you also seem to say this is a kit, that works on other identical engines without a scavenge pump ?
Hi Stevie, the turbo is proprietary from the kit manufacturer. It's just a basic turbo as far as I'm aware, not twin scroll or anything like that. It's run for about 25k miles on the car. The exhaust is blowing a lot of smoke, so it seems to be pushing oil past the seals. The mechanic believes this is because there has been oil back pressure. The company that fitted the kit have fitted about 10 others in this country, so there's not a huge number around, but they claim noone else has had the problem. Mine may have been fitted for more years than the others though.What type of turbo is it ?
How long did it run for in this configuration ? And did it run well, where there any indications of problems ?
You say it failed....exactly what failed ? That will very much tell you whether it is oil supply ( and drain ) related or not, but may require the turbo to come apart.
And yes if there have been symptoms of poor oil draining then a scavenge pump would be an option. But you dont seem to be saying there have been any such problems ?
And you also seem to say this is a kit, that works on other identical engines without a scavenge pump ?
stevieturbo said:
The way you word it...makes it sound like the turbo is chinese junk ? Otherwise you'd be saying it's a Garrett, Turbonetics, BW, etc etc etc
Are there any ID tags or better info as to turbo type ? It most certainly will not be anything unique that could not be repaired locally...unless it really is some chinese junk.
The exhaust is blowing smoke now...ok...but did this happen suddenly, over a period of time, have others or yours ever had oil consumption or smoke problems ? If not then it would be hard to say the oil drain is the culprit, as bad as it does look.
And 10 kits are enough to know whether that design does work, unless the others dont actually drive their cars ?
Have you ever spoke to the owners of any other kits ?
The turbo is manufactured by the company that makes the kit in the US, so it's not Chinese and it's not an off the shelf unit.Are there any ID tags or better info as to turbo type ? It most certainly will not be anything unique that could not be repaired locally...unless it really is some chinese junk.
The exhaust is blowing smoke now...ok...but did this happen suddenly, over a period of time, have others or yours ever had oil consumption or smoke problems ? If not then it would be hard to say the oil drain is the culprit, as bad as it does look.
And 10 kits are enough to know whether that design does work, unless the others dont actually drive their cars ?
Have you ever spoke to the owners of any other kits ?
The exhaust has always smoked a little, but is now smoking a lot. I'm talking big clouds, usually when pulling away from stationary.
I've not spoken to anyone else who's had the conversion as I don't know anyone else with it. I did some more Googling last night and it appears that it has happened to others in the US, but is not that common. One guy has fitted a scavenger pump and after having the turbo refurbished no longer has any smoke problems, so I think that may be the way to go.
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