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.
Is it gravity fed? Looks like it is tapped into something other than the sump so may well be pressurized.
Having that line hanging under the car like that would worry me but could this be an oil starvation issue when cornering (turbo spinning faster than the engine, so perhaps wears quicker than say the crank bearings)? Is the sump baffled?
Having that line hanging under the car like that would worry me but could this be an oil starvation issue when cornering (turbo spinning faster than the engine, so perhaps wears quicker than say the crank bearings)? Is the sump baffled?
Ok, sorry - that's the return line, so it does have a pressure feed somewhere?
It may be the angle of the photo but the line does look very 'flat'.
If you need gravity to do a job, it helps if there is sufficient height/ head.
Having said that, if it's pressure fed at an inlet and this is a return, hopefully it's still under some pressure in that return line, driving it back to the engine?
It may be the angle of the photo but the line does look very 'flat'.
If you need gravity to do a job, it helps if there is sufficient height/ head.
Having said that, if it's pressure fed at an inlet and this is a return, hopefully it's still under some pressure in that return line, driving it back to the engine?
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
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:
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?
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.
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.
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
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.
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.
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.
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 ?
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:
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 ?
Where that 90 degree fitting it tapped into the cam cover, that is actually the lowest point in the cover & directly above it runs the oil scavenge pumps that are fitted to each head, I'd guess there is some auction there at least, unless the pumps have been fitted incorrectly (which it is possible to do 180 degrees out, as there circular)
VladD said:
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.
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 etcAre 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 body and fittings of that turbo will still be the same as a lot of others, I.e T25 or T3 flange, outlet will be 2". There will be multitudinous turbos that will fit.
Take the turbo off and take it to a specialist.
If you can change the turbo to something like a Garrett GT28 you may well see a marked performance improvement as well.
Take the turbo off and take it to a specialist.
If you can change the turbo to something like a Garrett GT28 you may well see a marked performance improvement as well.
Gassing Station | Engines & Drivetrain | Top of Page | What's New | My Stuff