Does this boost look normal?

[Chapster]

2007 R51 YD25 Auto (Spain built). DPF and EGR deleted.
I fear the amount of boost I am getting is sub-par and would be keen to get a second opinion if possible. On another thread the guru Old Tony suggested to another punter:

"Take the car for a drive, as you pull away from the kerb with anything over half throttle you should see full boost (20-22psi) once you pass about 2,000rpm. I think the Garrett 2056V tops out at about 24psi above 3,000rpm, but if you're seeing around 20psi under normal acceleration then your turbocharger is performing pretty well."

At this point I cannot really relate to that!

Here is a chart of my car's performance about a month ago on a ~30min unladen drive on country roads with a sharp hill climb towards the start, a handful of stops and some decent straight(ish) stretches doing 90-100km/h:

- Boost mostly sits in the 0 - 4 psi range. Avg for trip was 2.2 psi
- Doing ~100km/h on the flat at 1900-2000rpm boost sits around 2-4psi (12:39 - 12:45)
- Max boost was 19.5 psi @ 3,400 passing up a steep hill (12:29). Pretty sure I floored it on that one.
- Other than that climb, boost only scraped past 10psi on 4 occasions at around 2,600rpm.
- On the handful of take-offs I would say I accelerated away at between normal and moderate pace

Am I just being paranoid or does it look like an under-performing turbo? Unfortunately I have not driven many turbo diesels so I am not entirely sure what feels "normal"

Most vac lines were already replaced at the time of that drive though I had not yet got to the fiddly one on the d/s under the inlet manifold. That was replaced last weekend at the same time the manifold got a thorough clean. My wife and I are driving to Toowoomba tomorrow so I will record that trip too and see if there is any change in the numbers.

 

[Chapster]

Hey All, an update on this one. Keen to get some input on my boost levels if possible. Trying to work out what is "normal".

First chart is 30 mins of highway driving yesterday around 95-110km/h. Avg speed 99km/h.

- Avg boost 4.2psi
- Max boost 10.54 psi @ 2473rpm
- Avg engine speed 2123 rpm. Max 2583 rpm

Second chart is 30 mins of low-speed commute today:

- Avg speed 27.4km/h. Max speed 78 km/h
- Avg boost 1.46 psi (ignoring negative readings)
- Max boost 10.39 psi @ 2752rpm
- Avg engine speed 1262 rpm.


I think most concerning, in light of Old Tony's quote above, is engine exceeds 2000 rpm while accelerating over 30 times and boost only exceeds 10 psi once. In fact it only gets over 8 psi 5 times.

Am I correct to believe I have a boost problem?

I thought it worth mentioning too that when sitting at idle, I typically have negative boost pressure between -0.05 and -0.34. Never while accelerating though.

Any feedback gratefully received!

 

[Sypro]

Not sure what normal boost is suppose to be but my d40 boosts between 10-22 psi with an average of 15, it does drop off below 10 at higher rpms (above high 2k range) but I've heard that's due to me running a stock hot pipe, which expands at higher rpms.

 

[Sypro]

I'd say check your turbo actuator to see if it's sliding up and down at idle and then get someone to rev it to 2.5k rpms and check if it still reacts, at idle if you have negative boost its possible you have a faulty boost solenoid. I'd start with checking my vacuum Hoses from the boost to the actuator. You probably just need a new boost solenoid. There are YouTube vids on testing the Actuator and the boost solenoid. So I'd start there.

 

[Chapster]

The actuator rod definitely responds when the vac line is removed and then replaced at idle, though it doesn't materially jump around when connected. I was testing on my own so was not able to get someone to give it a rev while monitoring. All vac lines are new and appear tight.

I did however bypass the BCS by connecting the vac pump line direct to actuator and do two tests: a stationary rev (to ~3,800rpm) and a take-off under moderate acceleration to around 80km/h.

I can post the charts up easily enough if helpful but in my view (which may not be correct) there was not a big difference to when the BCS is connected:

Stationary rev:
BCS connected: Max boost 2.7 psi @3844 rpm (throttle 15%)
BCS bypassed: Max boost 2.7 psi @3847 rpm (throttle 16%)

0-80km/h:
BCS connected: Max boost 10psi @2662 rpm (throttle 45%) Speed: 66km/h
BCS bypassed: Max boost 13.6 psi @2807 rpm (throttle 49%) Speed 68km/h

Yes there is a material difference on the take-off but I suspect this is more the difference in throttle position.

In fact charting the boost what I consistently see is boost is much more linked to throttle position than engine speed. On my way home after the above tests I floored it a handful of times (with BCS connected) and with throttle at 100% I hit 18-20 psi consistently:

Max boost 20.54 psi @ 3542 rpm. When I look at those results I wonder if everything is working okay.

So with "normal" driving it seems I consistently have < 5 psi of boost (max of 8-10 psi accelerating) because I drive with such a light foot. I make no apology for that because fuel economy is my priority day-to-day. But that is also why I am so keen to sort this boost issue out because I want this little engine to get all the help it should.

I suppose I am back to my original question: Are such low levels of boost with non-aggressive throttle normal and I should only expect decent boost when I am hammering it? Or am I right to expect more boost with "every day" driving?

And if the answer is yes, might this still be a BCS issue, even though on the above tests bypassing it did not make a great deal of difference? They are somewhat inexpensive (on ebay at least) so I am not opposed to just giving it a crack. But if other owners are like "Nah mate, low boost is just your lot in life when you drive those autos soft" I am keen to hear too.

TIA for any input.

 

[Sypro]

While driving my boost dies off at 3k+ so 20psi at 3500rpm seems pretty good in my opinion, i mean your max boost is very close to spec (driving) so if anything maybe something is a little dirty with the turbo, intake, tb etc.. but otherwise seems fine compared to mine. I'm getting a silicon/solid hot pipe soon from forefront industries, which is suppose to alleviate the boost drop at higher rpms due to hose expansion.

 

[Chapster]

Hmm my top end boost is okay but it's still the lag which bugs me.

As I understand it one of the major advantages of these VNT turbos is boost coming on at low RPM and consequently a steeper, more reactive boost response than I am experiencing. Spotting this fella's readings in a pretty much identical vehicle did little to allay my suspicion that current performance is sub-par.

Some thoughts i've had:

1. While I understand it's more common for the vanes to seize up in the closed position and lead to over-boosting, might my vanes be seized in a more open position with carbon build-up preventing the veins closing far enough to provide low RPM boost? If yes, any tips on cleaning/servicing the vanes and control ring mechanism without removing the whole turbo? Maybe a good whack of oven cleaner and then manipulate the actuator to loosen up (if that's the issue)?

2. Maybe someone fiddled with the actuator rod and it needs to be shortened.

3. I've read elsewhere here the vac pump also supplies the brake booster and I confess my brakes right now are not wonderful (which i presumed was my current need for new pads on the back and a good bleed which is scheduled for next weekend). But if I have a vac problem over there, I presume that would also manifest in vanes not closing (or not closing enough) while higher RPM boost remains okay as less vac is needed as vanes open. Any suggestions on how to test this?

4. Something else??

 

[BarneyB]

I can't answer all your questions, but I can share some info from my Nav.
I usually drive it with the Torque App running and various live data on my phone, including boost.
It's a 2008 VSK YD25 M/T 4x4.

- Zero or slightly negative boost pressure at idle is normal.
Remember boost is not intake manifold pressure. Boost is additional pressure above manifold pressure (that's why it's called "boost")

- When my BCS was connected, the most boost I ever saw was about 19.5 psi. And that was when I was fairly aggressive with the pedal. But more importantly, the spool-up response from, say, 8-9 psi to, say 17-18 psi was very fast from about 1900 rpm onwards. And then the factory BCS system is designed to pull boost back as soon soon as the pedal movement stabilises (or you change gears). You can watch it doing this rapidly while you drive. The boost jumps back down quickly as soon as your pedal stops moving further.

- I have recently fitted a Tillix valve and needle valve. I would recommend this to you for a few reasons...

1. It gives you control over the maximum boost allowed. And it's quick & easy to adjust.
2. It makes the BCS redundant, which simplifies trouble shooting.
3. It can be set-up to improve fuel economy.
4. Even if your car has a half-buggered t/c or another issue, the Tillix won't hurt anything and is still a good long term mod IMO.
5. The needle valve allows adjustment of the spool-up time which it sounds like you're having trouble with.
6. The Tillix can be adjusted to allow a higher level of boost than the ECU will tolerate (limp mode protection) so if you install the Tillix, and slowly adjust it upwards, one of three things will happen:
1) You'll find a good setting somewhere around a max. of 20-21 psi and if your spool-up time is acceptable you'll know that the now redundant BCS was the problem.
2) You'll be unable to achieve max. boost of 20-21 psi with the Tillix wound fully in. And then you'll know your issue is likely with the t/c and/or actuator.
3) You'll exceed the maximum tolerable boost level (23+ psi), either deliberately to prove a point, or accidentally, and trigger limp mode. Then reset the ECU and know your t/c is fully capable.

Other things that come to mind in no particular order:
- cracked/leaking intercooler
- cracked/leaking i'cooler pipework.
- failed i'cooler pipework couplings/clamps
- dirty MAF sensor
- damaged t/c compressor blades
- leaking exhaust manifold gasket
- failed t/c bearings or seals
- blocked air filter

 

[Chapster]

Cheers Barney for the detailed advice. Firstly, thanks for detailing your own boost figures and clarifying the negative boost. That helps. Thanks for the Tillix valve suggestion too and sharing your reasoning there.

I'm reluctant at this point though to plumb in a Tillix valve or other BCS alternative if its papering over a turbo or vacuum problem (or both). I want to get to the bottom of that first. Plus I am increasingly confident the BCS is not my (biggest) problem. If the ECU via the BCS prevents boost coming on while reving in neutral, then I expect I should have seen boost present when I bypassed the BCS in the test above, but the figure was the same: a miserly max of 2.7 psi @3844 rpm.

Well, that's my theory anyway. Anyone care to do a stationary rev test with BCS bypassed and tell me what their boost curve looks like?

Re your trouble-shooting checklist, MAF sensor is clean and air filter replaced < 2,000km ago. Cannot see any oil sneaking out around intercooler or pipework suggesting a leak but can take a closer look. My thinking though is if I am still seeing 18-20 psi at full throttle then I probably don't have a leak. I feel like all roads are pointing to turbo, possibly sticky/seized vanes, or inadequate vacuum.

 

[Erick]

If u have a variable vane turbo , it’s the first place I’d look. It’s their one big fault, vanes getting stuck/not working properly. Really sounds like vanes are not moving until vacuum builds sufficiently to force them to instead of just coax them.

 

[Chapster]

Okay an update on this one:

With the help of a mate I have given the hot side of the turbo a thorough cleaning such that I am now confident the vanes are all moving free and easily uninhibited by carbon build-up or other nonsense.

(I might post a separate thread about that one in due course as it was a fairly detailed job and others may benefit from some of our learnings on the way)

A few test drives and I'm still pretty unsatisfied with my low rpm boost / turbo lag (and fuel economy):
- Around town driving average boost is still < 3psi (rarely exceeding 10 psi)
- Highway driving: avg speed 96km/h | avg boost 4.29 psi | 2049 rpm (avg)

But top end boost is still fine: I hit 21.27 psi @ 3490 rpm booting it up a hill on Friday night (throttle 71%).

So next I turned my attention to the vacuum.

Here are some of my measurements:
1. Vac pump -> brake booster: 28 in/Hg
2. Vac pump -> BCS: 22.5 in/Hg
3. Vac pump -> BCS with booster hose blocked: 27.5 in/Hg
4. BCS -> turbo actuator: ~12.5 - 18 in/Hg (oscillating at idle)

Manual suggests vac pump output is 27.76 - 28.38 in/Hg so I am content the pump is in good shape.

Clearly there is a loss of vacuum to the turbo (5 in/Hg) when the booster is connected. Is this to be expected or within spec? I cannot find a figure for what amount of vacuum should be making it to the BCS, but I presume there should be minimal loss?

So I did some tests on the booster. My brakes are not great so I expected the booster might be dodgy, but it seemed to pass most tests okay (I think my issue is a failing master cylinder):

(a) switching off engine then intermittently pressing and depressing brake, it lifts with each press until fairly hard at the top;
(b) pressing brake with engine running then turning off engine the pedal holds for 30 secs no problem under mild pressure;
(c) pumping brakes with engine off (to clear all vacuum), applying the brake and starting the engine, the pedal softens and moves in okay. On this one though it keeps going a long way (hence my suspicion of a bad MC);
(d) connecting hand held vac pump direct to the booster and testing it also seemed nice and airtight with negligible loss over 30 secs.
(e) the only odd thing I noticed is applying the hand held vac pump to the booster the max figure I could pump it to was a smoodge over 15 in/Hg. It would not drop from there (see (b) and (d) above) but it definitely would not go higher. Manual says to test check valve air tightness apply 19.7 in/Hg and monitor for less than 0.39 drop over 15 secs. Well, I have not applied the pump to the valve in isolation but certainly in place on the booster I cannot get it to that test level.

Sorry, a crapload of content there. Any thoughts on those vac figures to the BCS? And if I am right to investigate vac loss over at the booster, can you see anything in those test results?

Many thanks for anyone able to offer some insights.

 

[Chapster]

* Sorry I probably should clarify the vac pump I am referring to in (d) and (e) above is a hand held vacuum pump for testing, not the car's vacuum pump (which I am referring to everywhere else). Sorry for any confusion. I will edit if I can...

 

[Chapster]

Just to add to the above, this morning I popped the hand held vac pump back onto the line in to the BCS and applied vacuum. Bit like when I applied it directly to the brake booster, the maximum I could get it to was 15 in/Hg (when warm; 13 in/Hg while cold). But once at that level it seems to hold there fine without loss.

If I start her up vac jumps up to around 23 in/Hg (same as test in above post), but once the engine is turned off it drops quickly back to around 15 in/Hg and holds.

So in terms of my ongoing quest for low RPM boost, I need to decide whether my next step is:

(a) go hunting for the cause of this 5 in/Hg loss in vacuum to the turbo when the booster is connected (and possibly also find the reason it can't hold at a level higher than 15 in/Hg); or

(b) presume 23 in/Hg is enough vacuum to keep the turbo side happy and move to the 3rd possible culprit: an incorrectly calibrated actuator. To that end my plan would be the follow the helpful guide @Scott52 posted here.

As always any guidance gratefully received!

If someone who is getting good low RPM boost could test their own vac in to the BCS and/or test what vac their brake booster can happily hold that would be truly epic.

 

[Old.Tony]

I think it's time to jump in here!

Usually the actuator arm isn't fiddled with, but there is obviously a chance that over time, due to vibration and thermal changes, the nut comes loose and the arm adjusts itself. That's entirely possible and well worth checking if you're not getting the boost range.

However, in your case you do appear to be getting the range, just not when you need it. This could be because of a faulty BCS (common), vac leaks, ballooning IC pipes, boost leaking (possibly through EGR valve), exhaust leaking (either through a crack or a hole in the EGR tube) and finally a leaking brake booster.

A way to check that the brake booster vacuuum is not interferring with the turbo is to isolate the booster - either clamping off the vac hose or removing it and plugging it. WARNING: your brakes WILL suffer from this, so do NOT do this in traffic! Either an isolated stretch of level-ish road or a race track should be used. Brake boosters are fairly reliable - I've only ever heard of a couple of these failing (maybe 3).

Personally I have a Tillix valve but I've bought a new BCS and will be installing that in the near future, just so I can test out an eBay cheapy and see how it performs. The Tillix valve is nicely adjustable but doesn't respond as quickly as the BCS to throttle inputs since it's a reactive device.

 

[Chapster]

Thanks so much for your response Tony and my apologies for the delay. Been a busy ol' time but I have recently jumped back into it.

This could be because of a faulty BCS (common), vac leaks, ballooning IC pipes, boost leaking (possibly through EGR valve), exhaust leaking (either through a crack or a hole in the EGR tube) and finally a leaking brake booster.

If I am still hitting 20+ psi of boost, am I correct to believe that would rule out boost leaks or bulging IC pipes?

Re the BCS, I bypassed it and didn't notice any discernible difference in boost whether driving or revving while stationary (results posted above) so kind of ruled that one out. Nonetheless, for the sake of thoroughness and knowing they are notorious for playing up, I ordered a new one from ebay to compare. I installed it and it performed much worse than my existing one (max 10 psi and bugger-all low RPM boost). So I sent it back, was convinced to get a new one instead of refund (silly me), gave it a crack last this week and exactly the same result - another dud out of the box. So it will be going back shortly too and I will try a different vendor (open to suggestions on that one!)

The EGR cooler is blanked both ends so I don't think I am losing exhaust there. Can't detect any leaks around the manifold or turbo either.

I have also replaced all vac lines, including that hard to reach one on the driver side under the manifold. Also, as mentioned above, I have tested the vacuum I am and still getting 23in/hg at the BCS. Though a circa 5in/hg loss in vac compared to when the booster is blocked, I think that's still well within range to operate the actuator, no?

In any event I took it for a drive with the booster vac line blocked (as you have also suggested) and again I did not notice any difference in boost. I could chart it if that would be helpful but I was pretty confident based on both feel and what I was seeing on the app. Top end boost still fine but tonnes of lag at low RPM. Oh and a nicely chiselled calf pulling her up

Which all kind of leads me back to the actuator and whether it is correctly tuned. I have been working on that this evening and will post my thoughts on that after one more quick test I want to do, but I think I may have found the problem (or at least part of it)!

 

[Chapster]

So, I turned my attention to the actuator, following @Scott52's excellent guide here.

As suggested I applied max vacuum to the actuator then adjusted the stop screw to meet the lever at its max position (to find the base as he says) then backed it off 1 turn so vanes not full closed. The stop screw came a surprisingly long way down.

Next I struggled to adjust the actuator rod because the last bloke working on it did the lock nut up ridiculously tight and rounded out the nut, so I removed the actuator to free it up and replaced the lock nut. With the actuator removed and the lever arm on the turbo moving freely I reset the stop screw and base. This time it set much higher (which I thought was good). Seems I missed the base by quite a bit when using the actuator to pull the lever up to its "max" position, which I initially put down to the rod length perhaps being wrong.

I reinstalled the actuator and applied vacuum to test when it made contact with the stop screw. The rod and lever moved fine up until about 12in/Hg but then lifted no further, even though well short of the stop screw. Strange. Odd thing is I could continue to apply vacuum to the actuator and it would go up to 20in/Hg, and hold there, but the actuator rod would not lift any higher than where it stopped (at 12 in/hg).

Which also explains why I could not lift the rod with vacuum in order to set the base.

Does this suggest the actuator is stuffed? I am wondering if the rubber diaphragm has maybe lost its malleability such that it holds vacuum okay but doesn't have the necessary range of movement anymore. Or something else in there is buggered.

As a post note tonight I decided to pull the actuator out again and bench test it. Sure enough, applying vacuum to it with no resistance the rod only moves from from 0 to 12in/hg and zero movement from 12 - 20 in/hg.

So I think my actuator is knackered.

I think that would also explain why low RPM boost is woeful. Even under max vac the actuator can't lift the lever high enough to close the vanes. Top end boost is fine though because the default with no or low vac is the vanes stay open.

Feel free to shout out if anyone thinks I am missing something, but at this point I am going to try and find a new actuator.

 

[Chapster]

I installed the new actuator on Friday and have to say I am very happy....I believe my lag problem has been solved. It takes off way better and with significantly more boost below 2,000rpm.

At the top of this thread I charted a trip out to my folks' place. Here is (very close) to the same drive two days ago with the new actuator installed:

Comparing figures:

- Boost mostly sits in the 0 - 4 psi range. Avg for trip was 2.2 psi Average now 5.5 psi
- Doing ~100km/h on the flat at 1900-2000rpm boost sits around 2-4psi (12:39 - 12:45) Doing ~92km/h on the flat boost is around 3-8 psi (average 5.4 psi)
- Max boost was 19.5 psi @ 3,400 passing up a steep hill (12:29). Pretty sure I floored it on that one. Max boost 21.41 psi @ 3861 rpm pinning it on a flat
- Other than that climb, boost only scraped past 10psi on 4 occasions at around 2,600rpm. Most pleasingly, boost exceeded 10psi FORTY-FIVE (45) times.

I'm not sure whether I should still expect better, but based on the marked improvement on what I was getting before I am very pleased.

I have not got through a tank of fuel yet but I am curious to see how the economy improves with the better boost. So far I have only driven 130km on the tank and the ECU's estimate until empty (for what its worth) has already improved by about 65km since filling.

For the record I was not able to find someone who would sell me a genuine actuator without the balance of the turbo. Even wreckers did not get back to me. There were a couple of knock-offs on ebay for about $120 but in the end I went with this one out of China for $80.29. So far so good.

Thanks again everyone for your input! Whether great or small, it has all been richly appreciated.