Outer Limits 4x4 Board

Have a 2.8 Isuzu Turbo Diesel. Connected some time ago a VDO turbo boost guage and from day one it rattled. An irritatting noisy buzz when you took your foot off the throttle. At no revs or at full boost it was fine.

So thinking that I had a dud guage, I bought another. Sitll a VDO and it did exactlly the same.

I had it plumbed in line with a pressue line going to my fuel pump. So, thinking it may have something to do with this I drilled a hole, tapped it with a 1/8 gas thread and put the correct connector into my inlet manifold. Still rattles, only worse. I guess that there must be some fluctuations in the input pressue to do this. Cannot be inlet valve issues (I hope) as I have only just got my motor back from being rebuilt.

Anyone got any ideas?

Cheers Rainsey

Interesting dude ..

I have VDO gaauges and I love it ..



I took the line from my throtle body and no deals with it ..

there are massive fluctuations in pressure in an inlet manifold due to the fact the the air flow is all but steady. these pulsations may be causing the rattle in the gauge. you could try restricting the flow to the gauge to damp out the pulsations. maybe just try a small kink in the line to restrict it. if that helps you could install a pneumatic flow control valve (needle and seat)
hope this helps

I had this when I put a boost guage on mine. Went to the local vdo dealer, told him the problem and he gave me a tiny little piece of plastic regulator thing. Had a tiny hole in it and went inside the 1/8"(I think) line that fed the guage. Did the trick and no more rattly guage.

what it is because your motor has a throttle butterfly when u back off it is reading manifold vacuum and it is pulsating if u put the restrictor in it it will take the pulsating air out of it

What size line did you use?
Using smaller lines can help, placing a restriction in the line will also work to dampen out the pressure pulses to the gauge.

I've put a shot of grease up the line before, worked very well.

when i purchased a boost gauge recently it came with a small brass insert which is goes in the line just after where you plumb it to the engine. it reduces the hole diameter to approx .3mm to stop that surge.

not sure if they are available a seperate item though.

sootygu wrote:not sure if they are available a seperate item though.

The guys I went to just gave it to me, said it was more hassle to do an invoice.

Hey guys, thanks for the feedback. Lets see in order of reponses:-

Tapage, spot on. In the old days I use to standardise on Smiths Instruments. Do not know if they exest any more. VDO always at that time used to be the next best option so I have stuck with them.

85LUX, Kiwibacon, sootygu... Fully agree with the fluctuation bit and have also seen the idea of restrictions. My old man years ago had a REDEX engine analyser that was nothing more than a vacuume / pressue guage and it had a tap on the side to screw up to stop the occilations in the pressue.

The line used was what came with the VDO kit, inside diameter about 2mm. The hose is hard plasit so reducing the diameter by kinking could be a bit tricky. The dealer in Sydney, Olympic Insruments, are no longer around so I will have to find another dealer that stocks or knows about the insert that you are talking about.

Xenith, the diesel is injected and does not have a butterfly. I think is more relevant to the carby engines but thanks for the info anyway.

Folks, thanks for the feedback, will see if I can get my hands on a restrictor.

Cheers

Rainsey

Just FYI, the restrictor in industry is called a snubber. They use it on rapidly changing pressures, like the discharge on a pump.
Hope this helps.

A Snubber, cool. So if we are talking turbo pressures of between 0 to 10 PSI, how smaller diameter can a snubber be to be effective and not totally block the pressure to the guage.

Sootygu's comment of .3mm sounds bloody tiny. I am blown away that occluding the pipe by that much would still let the guage work!

Cheers

Rainsey

rainsey wrote:A Snubber, cool. So if we are talking turbo pressures of between 0 to 10 PSI, how smaller diameter can a snubber be to be effective and not totally block the pressure to the guage.

Sootygu's comment of .3mm sounds bloody tiny. I am blown away that occluding the pipe by that much would still let the guage work!

Cheers

Rainsey

You won't totally block the pressure until you totally block the line. But a smaller hole will make the gauge respond slower. The trick is finding the point where the guage will respond fast enough but not chatter.
Instead of using say 1 x 0.3mm restrictor, you can use several bigger restrictors to get the same result. More tunable that way.

I'm using a VDO 30psi boost gauge (no vacuum scale) on an Isuzu 3.9L and having no chattering issues, standard VDO line (2mm plastic thing) but I've got it plumbed about a foot upstream of the intake manifold.

For a while I was using a cheap pressure gauge with 5mm PVC tube as pressure line. That was the one I had to use shots of grease up the tube to damp out the pulses. Pulsed a ridiculous amount.

i have a td42, custom intake manifold. vdo 0-15psi guage, i used an arb 5mm quick relase air line fitting into the intake, 5mm nylon blue arb line to the guage and no drama's running 13psi.

KiwiBacon wrote: I'm using a VDO 30psi boost gauge (no vacuum scale) on an Isuzu 3.9L and having no chattering issues, standard VDO line (2mm plastic thing) but I've got it plumbed about a foot upstream of the intake manifold.
.

Yep, I am running a 15PSI boost guage also with no vacuume scale with the standard genuine VDO fittings. My original guage was the VDO Turbo guage that was -30 to 25 PSI. Did exactly the same thing.

So, my challenge is to find a 'snubber'.

Cheers

Rainsey

rover1 wrote:i have a td42, custom intake manifold. vdo 0-15psi guage, i used an arb 5mm quick relase air line fitting into the intake, 5mm nylon blue arb line to the guage and no drama's running 13psi.

Hey this it's a nice nice ide .. use the ARB blue nilon line ... good shot, I'm using ( to replace the hite hard plastic line that come with my VDO kit ) a vacc line .. that it's more flexible and not broke at tight corners ..

VDO part number:

230.015 Air restrictor to fit 3/16â€

I under stood it was a diesel .Check again because some of those did have butterflys on those engines

[quote="baddboy"]VDO part number:

230.015 Air restrictor to fit 3/16â€

[quote="rainsey"][quote="baddboy"]VDO part number:

230.015 Air restrictor to fit 3/16â€