VDO turbo boost gauge buzzing, how to stop it?

Submitted: Monday, Jun 26, 2006 at 08:12
ThreadID: 35274 Views:10431 Replies:8 FollowUps:10
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Just installed a VDO turbo boost gauge on the 1996 2.8l TD Pajero, with a hose running from a 'T' in the fuel pump overfuel line, just above the turbo.
At most pressures, except full boost, their is a buzzing, like a high pitched rattle coming from the gauge.
Just the right pitch and volume to be really annoying.
Checking the hose from the turbo, there is a high frequency pulse in the air of the line, which seems to be converted to a buzzing in the gauge.

Any idea how to get rid of it?

Is the gauge faulty? It is a new gauge.
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Reply By: Snowy 3.0iTD - Monday, Jun 26, 2006 at 08:31

Monday, Jun 26, 2006 at 08:31
Had the same problem with a cheap Speco gauge I bought, in the end I gave up and spent the extra dollars on a quality AutoMeter gauge ( about $140).

AnswerID: 180355

Reply By: Mark T - Monday, Jun 26, 2006 at 08:39

Monday, Jun 26, 2006 at 08:39
Having been a distributor/service agent for VDO gauges for some 30 years I have some experience.

Inside the back of the gauge (where the pipe goes in) you made need to fit a restrictor. This is simply a small insert that reduces the inside ID of the back of the gauge.

Take your gauge to a VDO service agent and get them to fit one. I'm not sure where you are but if you are in Melbourne go direct to VDO in Heidelberg (they used to have a service department - not sure since Siemens took them over).

This should cure your problem.


AnswerID: 180356

Follow Up By: Truckster (Vic) - Monday, Jun 26, 2006 at 09:36

Monday, Jun 26, 2006 at 09:36
do you still have any contacts for them? I'm chasing a new gauge for my GU so i can leave the old one in the GQ when I sell it.
FollowupID: 436606

Follow Up By: Member - Oldplodder (QLD) - Monday, Jun 26, 2006 at 11:48

Monday, Jun 26, 2006 at 11:48

I am in Brisbane, and the VDO agent is only 10 minutes away.
Where I bought the gauge :-)

Have always preferred to use VDO.
FollowupID: 436629

Follow Up By: Truckster (Vic) - Monday, Jun 26, 2006 at 12:31

Monday, Jun 26, 2006 at 12:31
how much was yours Mr Plod? Been a efw yrs since I got mine, but at time i was working at Siemens :(
FollowupID: 436643

Follow Up By: Member - Oldplodder (QLD) - Monday, Jun 26, 2006 at 17:08

Monday, Jun 26, 2006 at 17:08
$59.00. Rang around to get the best price, I think Repco was cheapest. Agent matched it.
I think I got it for trade price, not RRP.
Flashed an ABN number for the price.

Plus a cheap non VDO pod for $20.00, which I had to modify to get it to fit.
Gauge was too long for the pod, so I cut a bit of some 2" PVC pipe I had left over from a previous job for an extension, and cut a black cap off a spray can of paint as a shroud.

I had some spare vacuum pipe and a bit of hose left over from installing the air bags about 6 years ago.

Had a buy a 'T' though for $2.00 from supercheap though. :-)

Just call me a scrounger!
FollowupID: 436677

Reply By: Michael Carey - Monday, Jun 26, 2006 at 12:41

Monday, Jun 26, 2006 at 12:41
I don't have an answer for you, but I'm going to monitor this thread 'cause my VDO boost gauge is doing the same thing. I've been putting up with it for a while now, but if it can be silenced, I will be most happy (as will my wife!)
AnswerID: 180395

Reply By: Flash - Monday, Jun 26, 2006 at 13:07

Monday, Jun 26, 2006 at 13:07
A longer feed line with a small restrictor (preferably closer to the manifold end) will definately cure the problem. Also it better to measure pressure further from the turbo- eg in the manifold just before the engine. That's what I did and no restrictor was necessary.
Don't toss the gauge- there's nothing wrong with it, though the pulses causing the buzz WILL eventually damage the gauge.
AnswerID: 180405

Follow Up By: Member - Oldplodder (QLD) - Monday, Jun 26, 2006 at 17:19

Monday, Jun 26, 2006 at 17:19
Great, thanks Flash.

When you mention a restrictor, what type of item are you talking about?
Just taking the pipe diameter down to something smaller?
Maybe a piece of foam from an aircleaner in the line, maybe 12mm long?
Or maybe use a disposable paper fuel filter in the line, something that will pass air, but take out the small pressure surges?

Yes, another option is to put the pipe for the gauge after the intercooler.
Was just trying to get it close to the wastegate to see what the waste gate is doing in real psi, and not having to allow for the pressure losses through the intercooler and associated piping. Assume there might 1 or 2 psi in that, but I may be wrong.

Might try VDO as above first.

But any help appreciated.
FollowupID: 436682

Follow Up By: Flash - Tuesday, Jun 27, 2006 at 10:34

Tuesday, Jun 27, 2006 at 10:34
I would put it after the intercooler, which is what the engine is seeing anyway.
I think that alone will cure your problem.
FollowupID: 436821

Follow Up By: Flash - Tuesday, Jun 27, 2006 at 10:45

Tuesday, Jun 27, 2006 at 10:45
Someone else mentioned it could be from the pulsations from valves in a 4cyl engine- this could quite possibly be true?
Anyway a restrictor will fix it. You need anything which will reliably restrict the pressure to a "trickle" such as an old carby jet or any small piece of metal etc with a tiny hole.
It will work best if at the manifold end rather than the gauge and obviously needs to be secured in the line in such a way that it cannot get ever sucked into the engine- not that there's ever any appreciable vacuum n a diesel.
I fixed that buzzing problem on a mates Paj using an old aluminium spray nozzle I had in a drawer for water injection (on a hot Torana- from many years ago in my youth)
It fitted nicely in the plastic line to the gauge.
FollowupID: 436824

Follow Up By: Member - JohnR (Vic)&Moses - Tuesday, Jun 27, 2006 at 11:20

Tuesday, Jun 27, 2006 at 11:20
I can't make out why is is stated to be Teed of the overfuel line rather than the boost pre or post intercooler. I guess it is off the line to the actuator or waste gate line.

I agonised over where my VDO gauge was to be connected Flash but reason that the boost from the turbo to the intercooler is what is controlled by the turbo systems. The POST intercooler pressure is subject to all sorts of things, like the pre-intercooler pressure, the restriction of the intercooler (and as to whether the engine can draw off air faster than the intercooler allows), the temperature of the ambient at time of day and it's impact on cooling. Too many variables to warrant rather than a pre-intercooler position.

I thought if I get serious about that all, I can put another gauge post-intercooler to get more knowledge as I think the Nissan intercooler is restrictive more than others.
FollowupID: 436830

Follow Up By: Chaz - Wednesday, Jun 28, 2006 at 02:04

Wednesday, Jun 28, 2006 at 02:04
Flash, when I mentioned that it was caused by the inlet valves, I should have elaborated. When the inlet valves open, the piston is travelling down which causes a pressure drop in the manifold. On a 4 cylinder, thats one induction stroke per revolution and that's why it's much more noticable on a 4.
Dampening the signal by restricting the line will solve this problem, but the gauge will be less sensative and slower to react. There is a happy medium there somewhere.
Personally I think the only downside to fitting the line on the turbo side of the intercooler is the heat factor. As long as the fitting and tubing can tollerate the heat it wouldn't be a problem because there is minimal pressure drop accross an intercooler, unless it's blocked, you would never see it on the gauge.
I chose the turbo side because I want to know what the turbo is producing and because my boost sensor is in the intercooler. Any major pressure drop will be noticable with power loss and the turbo working overtime.
FollowupID: 437027

Reply By: Member - Athol (NSW, 2527) - Monday, Jun 26, 2006 at 17:47

Monday, Jun 26, 2006 at 17:47
I fitted an inline snubber under the bonnet and cable tied behind some hoses so you can hardly notice it. It took away the noise and the Vibrating needle.
Not sure where to purchase them from but I aquired through the instument techs at work, I'd imagine you could try the likes of Blackwoods or industrial suppliers.

AnswerID: 180453

Reply By: Chaz - Monday, Jun 26, 2006 at 20:11

Monday, Jun 26, 2006 at 20:11
Hi Oldplodder,
The "buzzing" that you get from your boost gauge is caused by manifold pulsations as a result of your inlet valves opening and closing. This is normal and is more noticable with 4 cylinder engines and less noticable with 6 and 8 cylinders. Any sensative pressure gauge, weather it be boost or vacuum will do this. A simple fix (as previously mentioned) is to dampen the signal by restricting it or use a liquid filled gauge.
I have had gauges that only do it at full boost and others, like the one I have now, that only does it under decelleration. Just make sure that you have a "Boost Only" gauge for your diesel and not a "Boost/Vacuum" gauge.

AnswerID: 180477

Follow Up By: Member - Oldplodder (QLD) - Monday, Jun 26, 2006 at 21:07

Monday, Jun 26, 2006 at 21:07
Thanks Chaz,

Yes, it is only a boost gauge.
FollowupID: 436732

Reply By: S&N - Monday, Jun 26, 2006 at 22:19

Monday, Jun 26, 2006 at 22:19
the way i see it, if your using the boost guage as a diagnostic tool (making sure its not over-boosting) you should really spend the extra dosh and get a good one. in the WRX i owned, i put in BLITZ guages (boost and oil pressure). brands such as this and APEXi, have a great reputation for their accuracy. but if you just want it for the guage factor.....get what ever you want. I had a VDO and it was a couple of PSI out, and didnt hold steady at full boost, it wavered a bit. my BLITZ was rock steady and dyno proven to be right. if you want it to look real fancy, get the APEXi EL range. it comes with a control box that you feed all the info to and it runs the guages, and they have a guage for everything. and when they are off, they have a completely black face, when you turn them on they are back lit and shine through the black lens. BE WARNED, they are very pricey!!!!
AnswerID: 180508

Reply By: Member - Oldplodder (QLD) - Saturday, Jul 01, 2006 at 13:30

Saturday, Jul 01, 2006 at 13:30
Thanks every one for replying.

All very helpful.

There was one query about my connection in regard to 't'ing into the ovefuel line.

I have connected the boost gauge into the 3mm line which connects into the outlet of the turbo about 100mm above the turbo, and this line runs to the fuel pump, and I understand that when the fuel pump senses a high level of boost, it injects more fuel to suit.

This is just above the 3mm line that connects in here also and runs to the wastegate on the turbo so the wastegate can sense the out put and do it's job.

Trying VDO this week, and if no success, will put a restrictor in the gauge line. I may have a an old carby jet I can use (just got to find the old solex off the beetle), so thanks for that suggestion.
AnswerID: 181353

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