Al2O3 · Jul 15, 2017

Had one on my 90 for a few weeks now. I'm wondering what characteristics to expect from the turbo. My gauge is tapped in to the back of the inlet manifold.
In normal driving, pulling away in first I get a reading of about 0.3 bar just as I'm changing gear. Through first, second and a little bit higher in third. That's getting to high enough revs to make accelerating in the next gear quite easy as soon as you change up, but not driving it too hard. If I accelerate hard It'll go to 0.5 bar on point of gear change. Reasonably level on the A1 doing 60 mph it sits at about 0.5bar. On a long steepish hill, pushing the engine hard to maintain 60 mph, it'll go up to 0.7 bar. Thrashing it (more than I feel comfortable doing) on an incline in 4th and 5th it'll go up to 0.9 bar. I don't keep it there for long, just to test it.
I know these conditions are difficult to compare. Just wondering if anyone can give a rough comparison to what they get.

lynall · Jul 15, 2017

They can handle way more than 0.9 boost reliably.
I fitted a boost gauge on mine yrs ago but soon realised pointless bit of kit, does hit 1.3/4 bar quite often, I actually looked at it today to see if it was still working!
No need to be pansy the engine its a tough mofo so just drive it.

Al2O3 · Jul 15, 2017

lynall said:
They can handle way more than 0.9 boost reliably.
I fitted a boost gauge on mine yrs ago but soon realised pointless bit of kit, does hit 1.3/4 bar quite often, I actually looked at it today to see if it was still working!
No need to be pansy the engine its a tough mofo so just drive it.

Ha, ha, wasn't a case of being pansy. It was revving to a point where it was uncomfortable to be sat there.
I agree it's largely pointless, would have been interesting to see what it was reading in the weeks leading up to my runaway though.
Anyway, mine doesn't get anywhere near 1 3/4 bar. The garret turbo I've got on is only supposed to get up to 1.07 bar. Even screeming the engine I doubt I could get the turbo to boost to 1 bar. I just thought it would get to one bar before that, like working pretty hard up a hill.

ogb · Jul 15, 2017

lynall said:
They can handle way more than 0.9 boost reliably.
I fitted a boost gauge on mine yrs ago but soon realised pointless bit of kit, does hit 1.3/4 bar quite often, I actually looked at it today to see if it was still working!
No need to be pansy the engine its a tough mofo so just drive it.

Why "pointless"? I use mine to judge the right point to change gear. Reads up to 1.1 bar when accelerating hard, zero when in a comfortable cruise at about 2000rpm. Never done a "scientific" study of revs vs boost vs gears but there's probably someone on here that has and could put some physics into the discussion.

Al2O3 · Jul 15, 2017

ogb said:
Why "pointless"? I use mine to judge the right point to change gear. Reads up to 1.1 bar when accelerating hard, zero when in a comfortable cruise at about 2000rpm. Never done a "scientific" study of revs vs boost vs gears but there's probably someone on here that has and could put some physics into the discussion.

Now that's very interesting. How hard is hard? How do you know you're doing 2000rpm? Do you have a disco?

lynall · Jul 16, 2017

I would say if you need a boost gauge to know when to change gear you need an auto as you are putting way to much effort into driving your car.

To the op its not just revs its throttle v road conditions that makes the boost especially on a turbo diesel, on the 200/300 you can feel the torque drop off massively as you rev it and thats when its time to change gear.

Ps thats was meant to say 1.3 to 1.4 bar ish not 1 and 3/4 bar

though I have seen a 300 reach 1.6 bar on std turbo.

Rougharse Racing · Jul 16, 2017

The turbo on my 300tdi is near to the passenger footwell so I can hear the thing whistling away when it is working, no need for a boost gauge.

Disco1BFG · Jul 16, 2017

I have a boost gauge on my tuned 300 Tdi D1 Auto.

During heavy towing or the need for speed, I drive to the limit of boost, and hold it there - no point in chucking more fuel in than necessary. ( with the resultant black smoke

).

IMHO, essential in my application. YMMV.

Al2O3 · Jul 16, 2017

Pleaae feel free to take the pish about a boost gauge, I couldnt give a ....
I'm just getting to know my engine better and thought it a valid question. It may be ok, but I'm not 100% convinced the turbo is working ok.
I've driven all sorts of vehicles for 35 years, thankfully I can change gear at the right time now.

Tony e · Jul 16, 2017

Essential bit of kit in mi volvo FMX auto. Use it a lot when fully loaded and using manual select up and down hills. If used correctly will save a lot of fuel

Tony e · Jul 16, 2017

Low rev torque is what you aim for. Not speed

Kwakerman · Jul 16, 2017

Al2O3 said:
Pleaae feel free to take the pish about a boost gauge, I couldnt give a ....
I'm just getting to know my engine better and thought it a valid question. It may be ok, but I'm not 100% convinced the turbo is working ok.
I've driven all sorts of vehicles for 35 years, thankfully I can change gear at the right time now.

Remember in your installation you are measuring boost pressure at the back of the inlet manifold which is about as far away from the turbo you can get. The 1 Bar specified in the book will be measures at the turbo outlet (at the brass T piece that joins the waste gate actuator and the FIP pressure sense), you will be seeing lower pressures due to the pipework and intercooler. 1 Bar at the turbo outlet will not give you 1 Bar at the inlet manifold, you will also find that the gauge is more responsive when measuring pressure at the turbo as all the extra volume of the pipes and intercooler will act like a big reservoir/damper and try to even things out. If you really are concerned you could always block off the inlet manifold tapping and connect the gauge to the turbo to see what the 'real' pressure is.

Al2O3 · Jul 16, 2017

Kwakerman said:
Remember in your installation you are measuring boost pressure at the back of the inlet manifold which is about as far away from the turbo you can get. The 1 Bar specified in the book will be measures at the turbo outlet (at the brass T piece that joins the waste gate actuator and the FIP pressure sense), you will be seeing lower pressures due to the pipework and intercooler. 1 Bar at the turbo outlet will not give you 1 Bar at the inlet manifold, you will also find that the gauge is more responsive when measuring pressure at the turbo as all the extra volume of the pipes and intercooler will act like a big reservoir/damper and try to even things out. If you really are concerned you could always block off the inlet manifold tapping and connect the gauge to the turbo to see what the 'real' pressure is.

Yeah, I think you've mentioned this before. I appreciate how the intercooler, manifold and pipes will reduce the pressure. I wonder by how much? It would be interesting to tap it off at the turbo to see the difference. Assuming the turbo is ok, working hard up a hill I get 0.7 to 0.8 bar. If I got 1 bar at the turbo that's 0.2 to 0.3 bar drop (3psi to 4.3psi) Obviously!

No idea if that's an expected pressure drop.

Tony e · Jul 16, 2017

Dont feck about any more just treat it as an indication as to what is going on at what ever rpm in what ever gear. U will find the sweet spot. Just keep it around there .

neilly · Jul 16, 2017

Al2O3 said:
If I got 1 bar at the turbo that's 0.2 to 0.3 bar drop (3psi to 4.3psi)

Unless you are going to add a second boost gauge in to the turbo outlet so you can compare the two, I think you may be overanalysing this .

Cheers

Al2O3 · Jul 17, 2017

neilly said:
Unless you are going to add a second boost gauge in to the turbo outlet so you can compare the two, I think you may be overanalysing this .

Cheers

Not me, but it seems everyone else is!
You can put a boost gauge on your motor and watch it go up and down, under different conditions, which is fine. The next logical question to ask yourself is, am I seeing a normal response on the gauge. I think it's a particularly fair question especially as I've just rebuilt the engine and the turbo is new and I suspect it's passing too much oil and I'm just trying to get an idea of what might be going on. May well be the honing, there may be an issue with the turbo or both. I've read a lot of threads on here where people have been talking about their boost gauge, so I thought I'd see if I could get a feel for what was a standard response on a gauge for an engine like mine. It was worth a try

Tony e · Jul 17, 2017

Al2O3 said:
Not me, but it seems everyone else is!
You can put a boost gauge on your motor and watch it go up and down, under different conditions, which is fine. The next logical question to ask yourself is, am I seeing a normal response on the gauge. I think it's a particularly fair question especially as I've just rebuilt the engine and the turbo is new and I suspect it's passing too much oil and I'm just trying to get an idea of what might be going on. May well be the honing, there may be an issue with the turbo or both. I've read a lot of threads on here where people have been talking about their boost gauge, so I thought I'd see if I could get a feel for what was a standard response on a gauge for an engine like mine. It was worth a try

Steady on now. Like i said, dont bother with the psi just keep it appy around wat ever revs

reiny · Jul 17, 2017

It's not necessary at all but gauges are nice

ogb · Jul 17, 2017

My set-up works for me. If others have different ideas, that's OK. I posted for the benefit of the OP but also anyone else who might read this thread.
I can tell what speed my engine's revving at because I've put a tacho in. I don't drive a Disco, otherwise I wouldn't be posting on this forum.

Al2O3 · Jul 17, 2017

ogb said:
My set-up works for me. If others have different ideas, that's OK. I posted for the benefit of the OP but also anyone else who might read this thread.
I can tell what speed my engine's revving at because I've put a tacho in. I don't drive a Disco, otherwise I wouldn't be posting on this forum.

Thanks for replying. Just spotted the 110 in your avatar, sorry! You might have been having a look about other forums and decided to help out. Anyway, cheers.

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