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mahon257

Fitting a Turbo Gauge...

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This is probably one of those subjects where the more experienced among us will say "what? you didn't know that?". But I thought I'd share it anyway, because it's caused me grief for over a year!

So, about a year ago I fitted a Turbo / Boost gauge and an EGT (Exhaust Gas Temp) gauge, with a view to "tweaking" the fuel pump and Turbo Pressure, to give the old girl some more beans - mainly because she now weights 2.9 tonnes! (lots of gear added). See attached "Dash_a.jpg" and "Dash_b.jpg".

The basic story is... initially I read various forum articles (not just on this site), that suggested cutting the "Boost Control" Pipe (Part: ERR4699) - between the turbo and Bosch Injection Pump - then fitting a T-connector, and plumbing in your Turbo Gauge at the "T". After breaking about 5 plastic T connectors, because the Boost control pipe is made of the hardest plastic known to man, I eventually stumbled upon a metal T piece - which did the job.

After the plumbing was completed, I shortened the turbo's waistgate control rod by a few mm, and was happy with a boost pressure of 19psi (which seems to be the max. recommended).

So, now on to the Bosch injection pump! After, what seemed like days and days of "tweeking" I managed to get some extra power, but fuel economy dropped to 19 mpg (was previously 27 mpg). Altogether, pretty unsatisfying.

So, you know how it goes. You move on to other jobs! Anyway, a few months go by, and I'm again surfing the web looking for a better answer. I think I found it!

The problem, all along, is that the diaphragm in the injection pump, was no longer travelling the full 10mm. I had managed to tune the pump fairly well, all things considered, but essentially the fuel was either Full-on, or full-off (if you catch my drift). The problem, I now realise, was restricted airflow at the T piece I fitted for the Boost Gauge.

:blink:

So, what other options are there for fitting a Turbo Gauge? Well, funnily enough, LR have though of this! They have already provided a threaded hole in the air intake system for this very job! Who knew? :huh: It's in the Plenum Chamber! It's a bit tricky to find the hole, with the Plenum chamber on the car, so see Attached images "Plenum_a/b/c/d.jpg" - which show the "drain hole" on a Plenum that's been removed from the car.

This kinda makes sense. After all, the point of the air intake "system" (turbo/pipes/intercooler) is to deliver pressurised / cooled air to the plenum chamber. So why measure the air pressure from the Boost Control Pipe? That completely circumvents the Intercooler, and associated pipes!

I've also seen some folks connect the waisgate actuator to this hole in The plenum - but that scares me, as any sort of obstruction in the intake system could lead to the turbo spinng out of control to certain death!

If anyone wants to follow my example, you will need:

  • A turbo Gauge - fleebay £25
  • Banjo Connector Pipe Err4700 (fits the plenum chamber drain plug hole perfectly) - £13 on Britcar
  • 2 x copper washers (M12)
  • 1 x M12, (1.5mm thread) Banjo Bolt

The image attached "Drain_plug.jpg" is there to show thread size (M12 x 1.5mm), obviously you replace this bolt with a banjo bolt.

(A big thanks goes to Steve @ JSF for having the patience to find these parts)

So, I've now got proper power delivery across the boost range, more power (pulls like a train), and MPG back up to around 26mpg. Not bad for a 3 ton car!

Welcome any comments / laughter!

Cheers

Nick

:rolleyes:

PS: I also restored the Boost Control Pipe (ERR4699) to it's original state - i.e. fitted a new one - to replace the one I had previously hacked about fitting the T piece.

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Nice little write up there. ON my defender I put in a boost gauge where you originally put it but haven't had any problems up until now, but have only adjusted the off boost fuelling on it.

Haven't played with my disco yet but if I do fit one then I like the idea of the banjo bolt in the inlet manifold. I think it should woek with the 200tdi as this has an easier to access bolt half way along the inlet.

Jon

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I agree with you about not relocating the turbo boost sensing pipe to the plenum, though I'm surprised that the T peice made that much diffrerence.

Rather than tweaking the turbo actuator I fitted a boost control valve which along with being a 3 minute job to adjust also prevents waste gate "creep" at part boost, making the car more driveable at part throttle.

What I would really be interested to see is the difference in response between a pressure gauge Ted into the turbo actuator and another connected to the plenum, I suspect the later would lag the former momentarily which would suggest the engine runs very rich for that moment.

I tried getting hold of a truck air brake guage to do this, but they aren't cheap (some have 2 gauges in one for the 2 air systems).

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nice little write up - tech archive maybe mods?

it's a bit weird how that bolt is called "cushion-child restraint booster" on the microcat though :blink:

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....I'm surprised that the T peice made that much diffrerence.

Should explain how I figured out it was the T piece.

As I said in my main post, the injection pump has been "tuned" after the original install of the Turbo gauge (using a T piece). It was "ok" on power, but economy was dire. I had tuned the pump to the point where the car did not smoke - other than at cold start, which I believe is normal.

So now, 1 year later, I have re-positioned the Turbo Gauge plumbing to the Plenum chamber and re-fitted a brand new Turbo Boost Control Pipe - (ERR4699). Once this was done, I went for a test drive!!!

At this point, no changes were made to the boost pressure, or fuel pump. As soon as I got up to speed, I put my put down, and immediately got a massive cloud of black smoke out the exhaust. This told me the engine was over-fuelling under boost.

The only explanation I could come up with was a lack of pressure on the Diaphragm - meaning, with the T piece in place, the diaphragm wasn't travelling it's designed distance (approx 10mm).

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you will also find that the pressure you see on your gauge is lower than it was before, this is due to the pressure drop through the boost pipes and intercooler so what you are seeing is the "true" boost pressure that your engine is seeing.

in addition, the gauge should hold noticably steadier in its reading and there shouldnt be a "pressure spike" when you max the boost :)

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is the banjo bolt . err886 ?

I wasn't able to get a part no. for the banjo bolt - the picture attached shows thread gauge - M12 /1.5mm thread. I went to a local LR parts specialist (JSF in Norwich), taking the original bolt from the plenum chamber with me... they were able to dig out a banjo with same thread type.

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I think you will find that its ( the banjo fitting) exactly the same as the front and rear diff axle vent, thats what I used on ine and aquired from my local wreaker, it fitted the standard VDO guage plastic line which was a bonus.

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I'm in the middle of doing thus just now & ordered a part to use the plenum chamber. Could someone tell me if this is proper part?

Thanks in advance from a trainee!

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On my Disco, I removed boost control pipe from turbo. I have turbo actuator and boost control pipe and boost gauge all T'ed and coming from the banjo bolt on the back of the inlet manifold. As this should be getting true pressure of what the engine is receiving.

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On my Disco, I removed boost control pipe from turbo. I have turbo actuator and boost control pipe and boost gauge all T'ed and coming from the banjo bolt on the back of the inlet manifold. As this should be getting true pressure of what the engine is receiving.

Mines is an automatic with EDC. I'm looking for the easiest/simplest way of doing it as I'm not that mechanically minded. Anywhere on the EDC Boost pressure system I could use instead? Picture courtesy of Haynes!

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On my Disco, I removed boost control pipe from turbo. I have turbo actuator and boost control pipe and boost gauge all T'ed and coming from the banjo bolt on the back of the inlet manifold. As this should be getting true pressure of what the engine is receiving.

Mines is an automatic with EDC. I'm looking for the easiest/simplest way of doing it as I'm not that mechanically minded. Anywhere on the EDC Boost pressure system I could use instead? Picture courtesy of Haynes!

Sorry for double post.

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Nice write up and great to know that there is a plenum bung we can use. I have to see if the 300tdi plenum in my 97 defender has the bung where you attached your boost gauge tube.

To the guy who is seeing -0 you have to drive the Landy and accelerate to see boost or + ;o)

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