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850 / S70 & V70 '96-'99 / C70 '97-'05 General Forum for the 850 and P80-platform 70-series models |
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T5R boost question / help pleaseViews : 6337 Replies : 118Users Viewing This Thread : |
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Sep 6th, 2021, 22:36 | #11 |
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[/QUOTE] My dash gauge goes to about 4/5 into the white on stock boost, I get the fuel cut jerks if I try to go higher by tweaking the waste gate.[/QUOTE]
Jammin - I'm sure you know the risks - but just for the uninitiated boost junkies: shortening the actuator rod will cause the turbo to build more boost low down in the RPM range and potentially bend rods. Without a forged bottom end you may wish you'd left it at stock. However, that said, it is an easy way to get lots of whoosh for very little spend. Risky...but cheap. |
Sep 6th, 2021, 23:01 | #12 | |
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Sep 7th, 2021, 07:12 | #13 |
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Thanks guys so far I don’t have access to any fancy vacuum/pressure stuff to do the wastegate sadly, but will certainly attack the vacuum lines and see what that does and go from there. Is the TCV still a readily available part?
The turbo was rebuilt by a reputable company in the south west (Owen Developments) so I’d like to think the turbo should be ok although I am surprised the ropy vacuum lines are still being used. I say ropy, they may be ok but feel crumbly to the surface like rough sand paper, old rubber I guess. Another query, which may or may not be relevant. The car appears to reach operating temperature really quickly or at least the gauge gets to half really quickly. It sits there and never moves however and the fans cut in if you allow it to. The top hose gets hot and I’ve put a new ‘green’ coolant cap on the expansion tank only because it had an original grey one. Coolant levels are fine but it seems to reach operating temperature quickly. The paperwork shows it had a new thermostat and coolant last year when the cam belt was done. Any thoughts?? Does the temperature have links to the TCV i e holding back boost if it’s too hot? With regards to the stage 0, it has new cambelt and tensioner, new plugs, leads last year, the oil and filter plus fuel filter were done last week so it’s pretty much had most stuff done. The PCV was done last week but it still seems to smoke a little from the oil dip stick which is another head scratcher!! Please keep all thoughts coming!! Thanks in advance Mark Last edited by Pupbelly; Sep 7th, 2021 at 08:27. |
Sep 7th, 2021, 11:45 | #14 | |
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http://www.vpcuk.org/forums/showthre...o-they-compare The standard settings for the T-5R are 11 p.s.i. on overboost (which supposedly lasts for up to (but not always) 30 secs, and 9.5 p.s.i. under normal conditions. 11 p.s.i. corresponds to fractionally over 2/3 into the white, 9.5 p.s.i. is a bit under 2/3 into the white. My own standard T-5R (automatic), when I kick down, shows initial surge for 3 or 4 seconds with the needle about 5/6 into the white zone (roughly 13 or so p.s.i.) dropping back to the 11 p.s.i. point and then slowly easing back to around the 10 p.s.i. point. These have all been confirmed using an accurate additional gauge temporarily plugged into the vac tree. I've also attached the vac diagram for the T-5R. Assuming all your vac pipes and turbo pipes are sound and clipped up tightly, the most common causes of poor boost seem to be firstly, a damaged diaphragm in the TRV (turbo recirculating valve) followed by a faulty TCV (Turbo Control Valve). Neither of these would be audible. Wastegates are surprisingly reliable, even at huge mileages, but can fail due to weak springs and/or poor seals. If the wastegate is the issue, I would replace with one from Forge. They even tell you how to set it up easily without gauges, spring balances etc. The turbo itself is unlikely to be a problem as at that level of poor boost, there would be other symptoms from the turbo (oil burn/noise) I'm sure. Worst case scenario would be a split intercooler but you would almost certainly hear the escaping boost. Hope this all helps to some degree. John
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Sep 7th, 2021, 12:32 | #15 |
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Thank you JohnM 855 T5R Interesting to get some idea on boost figures there, that points to a certain boost loss as I thought. I've ordered some silicone pipework to do the vacuum hoses. How available are the turbo control values and turbo recirculating valves? Is there a way they can be checked before I purchase new / replacements?
I gave the car a detour to work this morning and it is lacking in 'go' for sure. My daily driver is an Impreza and ok its a totally different car but there is no surge or oomph at all to the point where I feel the turbo is not offering anything of value. Disappointing because it has been a looked after car. It just needs a little something, but I need to establish what that 'something' is without just throwing money at it. Helpful VPC link too - Thank you. Last edited by Pupbelly; Sep 7th, 2021 at 12:46. |
Sep 7th, 2021, 13:16 | #16 | |
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The TRV has a diaphragm inside which can split or pinhole. A diaphragm and spring kit is freely available on eBay. Get one made by Kinegawa (they are the original manufacturers) and costs about £30 or so. Easy to fit (one of the bolts is a little fiddly). Just take out the bolts on top of the TRV, pop the new spring and diaphragm in (make sure to use the standard spring which I believe is green). You can get the whole Kinegawa unit for not much more. I replaced mine with a Forge piston type TRV at £150. Supposedly more reliable in the long run but as you see, expensive! You can get this from Forge Motorsports direct or via Parts For Volvos. The original TCV can be ordered through your Volvo dealer via GCP and costs about £130 - ouch! Alternatively, I believe you can fit the Pierburg unit for the early V70 and is available online for about £40 ish. They are not, I believe, specific to each turbo model - the same part works on all 850/early V70 turbos. You can strip the TRV and inspect the diaphragm but once you gone to that bother you might as well stick a new one in. I don't know of any test you can perform on the TCV. I replaced mine because it was cracked and resulted in wild overboosting. Regards John
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Sep 7th, 2021, 13:26 | #17 |
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I think the TRV has been replaced. The penny just dropped when I Googled it. The turbo has been rebuilt and the triangular area facing the engine block (from memory) is shiny and new so I will assume it is all new, so I guess that lead us back to the turbo control valve possibly? I'll try and get a photo later after work.
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Sep 7th, 2021, 13:56 | #18 | |
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Sep 7th, 2021, 13:58 | #19 | |
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Sep 10th, 2021, 20:59 | #20 |
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Very interesting thread for me, this is, as my V70T5 is also lacking "vigour", I'm sure it's not boosting anything like as much as it used to.
Sorry for piggy-backing onto this thread, but I think I probably need to look at replacing my TCV and vacuum pipes too. Can anyone tell me what diameter vac pipe is used to and from the TCV please? Also, any good sources for non-silicone vac pipe? Thanks!
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