3.0d Turbo lag issue..

[Ohsoslow]

Hey guys, have been searching for last few months, have replaced and checked all I've come up with off google etc, but still no solution. Perhaps my problem is normal.. I didn't notice it on other x5s I have driven though, but then didn't drive them all the time!

Basically it feels like I have next to no power under ~2500rpm, then it goes really well. Is this amount of lag normal? I can hold car in 6th, and put foot down and boost will slowly climb from ~2200rpm, but if I hit a slight incline and I'm below 2200rpm, car will slow down.

basically, is this normal? If not, any ideas on what might be wrong?

Have changed maf twice, checked vacuum canister and lines, solenoid for turbo, all seems good. Removed intake manifold, removed egr, cleaned that all out best I could. No fault codes relating to engine. (Frustratingly a tcm fault has appeared today..)

[blakamin]

I haven't had a BMW 6cyl that was any good under 2500rpm.

After 2500, all good!


And I've had a few... (look below).

[Crowz]

I have a few turbo diesels but not a bmw one.

Here is what I found on google maybe it will help some. This is from someone that owns an x5 similar to yours.

My engine starts boosting roughly at 1800 to 2000rpm, and full boost at about 2400 to 2500 rpm, so recon yours should also be in that area.

I also can't promise the turbo is 100%. if the impellers are worn, this may also cause lack or late boost. If the exhaust wheel is worn, it must have much more engine rpm to spool. If the compressor wheel is worn, it may need much higher turbo shaft rpm to make sufficient boost.

Problem solved
after I took it to BMW Secunda and they gave me a quote of
R51 568.99
I decided to go through everything I could
I had the Cat's removed and still no deference
So this weekend I removed the turbo and cleaned it
When I stripped the exhaust side I noticed that the vanes did not move with the ring that was supposed to open and close it (see attached image's)
I cleaned everything and reassembled it and now has boost all the way through so I just saved R51 568.99

[Ohsoslow]

Thanks heaps guys!! So it does sound like maybe it's quite normal, and I'm just expecting a bit too much from it down low.

In my googling I came across a fair bit about the turbo and it not operating properly. But, The actuator definitely moves, boost when it does come on is solid and consistent through to redline.

There is a fair bit of info about vw guys using mr muscle oven cleaner to clean their turbo, have been tempted to try it, but bit of a pain to get it into turbo! And will gut the cat converter one of these days when I can be bothered, but I don't think that would affect power down low much.

[wpoll]

I've recently seen a similar issue on a 2009 Kia Sportage 2.0d and after being told it was everything from the EGR to the fuel pressure sensors etc. we fixed it by sorting the vacuum actuator for the variable vane turbo. Power was flat as until you got the rpm up, then it was OK. After sorting the vacuum actuator (clogged filter) the car has a lot more bottom and mid-range power, as the VGT is now working as designed.

In your case you have confirmed the actuator is working so it's possible that the vanes themselves are stuck (although I would have thought that would also seize the actuator too).

One test you could try is to disconnect the vacuum lines from the actuator (or the tank - access is better!) and connect a vacuum hand pump. Then you can control the VGT manually, drive it both with no vacuum and with full vacuum and see the difference. With an extension line you can even bring the hand pump into the car and vary the vacuum while driving but be careful about setting the vanes fully open at higher RPMs as you can generate too much boost!!

Even if this test only shows how bad the power is when the VGT is in the wrong mode for the current RPM (vanes closed at low RPM should make the car flat as heck...) at least you'll then know that any issue you have (if you have one) is NOT the VGT.

E Max have cheap vacuum pumps (good for bleeding brakes too!).

https://www.emax.co.nz/index.php?mai...oducts_id=3188

[wpoll]

Another thought I had is that I read that the M57 engine is prone to cracking the exhaust manifold (it's welded stainless). I imagine a cracked exhaust manifold could reduce exhaust gas pressure to the turbo...

I'm sure you would have spotted this by now if it were the case. Symptoms such as a change in engine sound and a crap load of exhaust soot around the exhaust manifold would be obvious.

I took closer note of the boost in my 3.0d today, driving around town. Up steep inclines, the boost is noticeable by 2,000rpm, kicking harder by 2,500rpm and taking off like a two-stroke power-band by 3,000rpm.

[Ohsoslow]

Hey Wayne, thanks heaps for replying! I had a play with the vacuum lines to turbo, nightmare to get to actuator btw! :p and does seem to confirm the turbo is working properly. Unless the vanes are partially stuck.. Eg not able to close or open fully.

The only other thing I've found that might be an issue is the air temp sensor after Intercooler. Have no way to test it, but if it's covered in oil, perhaps it's reading wrong, (high) and ecu isn't putting in enough fuel. *shrug*

No sign of cracked manifold thankfully. And ultimately car does drive great, just seems a lot flatter off boost than I was expecting.

Maybe it's a sign I should compound turbo it. :p

Oh and I am getting together parts for a water/meth kit, anyone on here added one to their diesel?

[Ohsoslow]

Figured I’d just add to this post rather than start new thread. Just wondering if anyone is smart in regards to air flow dynamics etc.. basically I’ve put a hose tail at 90degrees to my intake pipe, to feed to a pressure sensor to trigger water injection kit. But it’s only occasionally turning on.

Would having the hose tail at 90degrees cause a Venturi effect and be stopping pressure from reaching sensor? (Even though the air in intake is under pressure, it’s obviously flowing pretty fast into engine..)

[wpoll]

Originally Posted by Ohsoslow

Figured I’d just add to this post rather than start new thread. Just wondering if anyone is smart in regards to air flow dynamics etc.. basically I’ve put a hose tail at 90degrees to my intake pipe, to feed to a pressure sensor to trigger water injection kit. But it’s only occasionally turning on.

Would having the hose tail at 90degrees cause a Venturi effect and be stopping pressure from reaching sensor? (Even though the air in intake is under pressure, it’s obviously flowing pretty fast into engine..)

I don't know much about fluid dynamics but here's an image showing air flow pressures at a bend (actually a Tee but it shows the effect...)



And BTW, my post-intercooler air temp sensor is also oil-soaked - I'm just going to replace it. The switch itself is leaking. Worrying how much oil is in the intake system though..

[Ohsoslow]

Thanks for the pic Wayne, unfortunately it doesnt mean much to me, I’m a bit thick! Also after googling it more, I don’t think Venturi is even the right word for what might be happening.

And yeah, after doing my intake manifold etc, now have a thin film of oil all over everything again. Will be making a catch can when I get the chance at work, 12hr days in this heat isn’t much fun at the mo! Then need to remove intercooler and give that a clean out too!