T5R boost question / help please

[Pupbelly]

What level of boost should be displayed on the stock boost gauge under full boost?

The needle on my car goes about 1/4 into the white section, and there doesn't feel to be the surge of power I would expect. Are there any obvious things I can check? I've looked at the lines from the turbo to the TCV and everything is now connected (the blue line to the fresh air link wasn't connected at the tree ). The hoses do feel a bit crumbly on all three so could there be a boost issue there as a result?

It doesn't feel as urgent as I think it should, so any advice would be welcomed.

Many thanks
Mark

This is a recent purchase (two days old!) so I'm still learning the quirks of the car. It has near full history. Recent turbo rebuild, and the PCV has just been done. Looking for guidance please as I learn to hopefully gain trust in it!

[ITSv40]

I cannot help with the boost issue, but just wanted to say glad you have found a car that appealed to you and hope you have many happy miles in it.

[Pupbelly]

Originally Posted by ITSv40

I cannot help with the boost issue, but just wanted to say glad you have found a car that appealed to you and hope you have many happy miles in it.

Thank you! More details to follow in another thread, but in theory it should be a joy. 99.9% original and has led a charmed life very little use over the last few years, however I just feel it's lacking 'oomph' so as I'm a newbie to the world of Volvo ownership I'm looking for some guidance.

I'm hoping it could be just ageing vacuum lines but if there are any other pointers then hopefully someone on here can help. Whilst the turbo gauge does show negative on the scale then just into the white on the dashboard, it doesn't feel like I think it should i.e. a good linear shove of power, or even an old school wallop of boost at around 3k.

Vacuum pipes, intercooler hoses...?

Anyone??

[andrewc1267]

You could really do with an accurate boost gauge and also as regards to lack of power it all depends on what you are comparing to. I have said before in previous posts that I find the standard T5 engine lazy especially compared to modern cars.
Once you have an accurate reading of the boost pressure firstly I would get back to basics check or better replace all the vacuum hoses and check all boost hoses intercooler ect for leaks I use a smoke Pro for this. I remember on my me7 v70r it was the wastegate control valve caused an issue where the car would be savagely quick then nearly no boost

[Pupbelly]

Originally Posted by andrewc1267

You could really do with an accurate boost gauge and also as regards to lack of power it all depends on what you are comparing to. I have said before in previous posts that I find the standard T5 engine lazy especially compared to modern cars.
Once you have an accurate reading of the boost pressure firstly I would get back to basics check or better replace all the vacuum hoses and check all boost hoses intercooler ect for leaks I use a smoke Pro for this. I remember on my me7 v70r it was the wastegate control valve caused an issue where the car would be savagely quick then nearly no boost

I’ve ordered some replacement 5mm silicone pipe plus clips and I’ll replace the lines from the turbo to the turbo control valve (the thing with the coloured lines leading to it) although one of them seems to connect almost under the turbo which looks a cow to get at!
If that offers nothing then I’ll do the intercooler pipes.

I would have thought a T5-R with circa 240bhp would have a good shove when on boost.

One thing I noticed tonight, if I rev the car with the airbox lid lifted I can hear the turbo but there’s a momentary whistle briefly, not turbo whistle and actual as though a person were to whistle a short sharp “peep” as you blip the throttle. Is this an indication of a leak somewhere that is being voiced through the airbox lid??

All thoughts welcomed!!

[Pupbelly]

Where does the turbo control valve take its electrical information from? Could it be faulty?

[andrewc1267]

Originally Posted by Pupbelly

I’ve ordered some replacement 5mm silicone pipe plus clips and I’ll replace the lines from the turbo to the turbo control valve (the thing with the coloured lines leading to it) although one of them seems to connect almost under the turbo which looks a cow to get at!
If that offers nothing then I’ll do the intercooler pipes.

I would have thought a T5-R with circa 240bhp would have a good shove when on boost.

One thing I noticed tonight, if I rev the car with the airbox lid lifted I can hear the turbo but there’s a momentary whistle briefly, not turbo whistle and actual as though a person were to whistle a short sharp “peep” as you blip the throttle. Is this an indication of a leak somewhere that is being voiced through the airbox lid??

All thoughts welcomed!!

If you remove the turbo air intake pipe it makes the the connection on the compressor housing you need a bit easier to get to I did mine recently

[JohnM 855 T5R]

Originally Posted by Pupbelly

What level of boost should be displayed on the stock boost gauge under full boost?

About 1/4 into the white zone corresponds to roughly 4 p.s.i. Full scale in the white zone is approximately 16 p.s.i. Here is a link to a useful page.

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

[Pupbelly]

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.

[JohnM 855 T5R]

Originally Posted by Pupbelly

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?

Opinion is divided as to whether silicone is the best way to go. The silicone pipes have a tendency to eventually slip off unless they are very well secured. I've put silicone hoses on mine and I purchased new stainless jubilee clips to secure them. I've had no problems.
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