TD5 Turbo - wastegate control

septimus · 25th August 2005, 06:10 PM

Still on the TD5 Turbo trail! Today had it checked out and the turbo is generating 15psi nice and consistently (which is less than the pressure elsewhere stated to be correct). However there seems to be a conflict between the rave documentation and the TD5 turbo as it is installed in my 99MY Defender.

According to RAVE there is a wastegate modulator which is controlled by the ECU and when turbo pressure is at the limit it applies a vacuum to the wastegate controller and opens the wastegate valve. This would imply that the air line to the wastegate controller comes from the modulator and that the modulator is connected to a source of vacuum (?).

In my case the wastegate controller mounted on the Turbo is connected directly to the hose running to the intercooler. It is therefore controlled by its internal settings and opens when the pressure from the turbo via the hose to the intercoooler reaches 15psi.

So far as I can see, this is totally at odds with the RAVE description. Can anyone tell me how their wastegate controller on their TD5 Defender is connected? Is it connected directly to the hose to the intercooler or via a wastegate modulator to that hose or what?

The Turbo guys quickly identified that someone had been playing with the wastegate controller on mine - the locknut was loose and adjustments were out. I am wondering if at some stage the wastegate modulator was removed and bypassed which could be causing my performance problem. Or is my installation typical and the RAVE description for some reason not applying to the local versions?

Any comments, photos, whatever appreciated.

**DEFENDERZOOK** · 25th August 2005, 09:08 PM

<span style="color:blue">cant help out with any of your questions....however....

some did say somewhere on this forum that their car was over boosting
which would send it into a limp mode....

once the ignition was switched off it would reset the fault and all would run
just fine ....until it overboosted again......</span>

**defute** · 26th August 2005, 06:59 AM

Hi septimus,

The turbo wastegate on a Defender Td5 is operated by pressure (not vacuum) via a hose that feeds boost pressure from the intercooler hose. This boost pressure is used to 'push' the wastegate valve off its seat at a predetermined point.

The Defender Td5 (unlike to Disco 2 Td5) does not use a modulator valve controlled by the Engine Management ECU to operate the wastegate valve.

So, I would suggest that your vehicle is configured correctly.

Cheers,

MARCEL

septimus · 26th August 2005, 07:49 AM

Originally posted by defute
So, I would suggest that your vehicle is configured correctly.

Thanks Marcel. As Peter (the LR guy in Frankston) said when I told him I had been reading the workshop manual, "that's dangerous" :roll:

Looks like the RAVE info I have for the Defender TD5 is for a configuration not used here.

**disconut** · 26th August 2005, 11:48 AM

Hi Guys,
I have just checked mine, and it is as defute says. I suggest the section in the RAVE disc is a cut and paste job from the Disco disc.

Reading up on the turbo refit for Defender it says
"24. Position and secure vacuum hose to turbocharger wastegate." No mention of a modulator.

This would tend to confirm that there is no ECU wastegate modulator on the Defender.

Trev.

**disconut** · 26th August 2005, 11:57 AM

After further reading I also found this little gem.

"In the event of a MAP/IAT sensor failure any of the following symptoms may be observed:
• If the MAP sensor fails manifold pressure is set to a pre-determined default value and the engine performance will be reduced.
• If the IAT sensor fails the ECM will set air temperature to a fixed value. The ECM will use a fixed default value from its memory."

This agree's with Tony's thoughts. You may have a stuffed MAP sensor causing your poor performance.

The MAP/IAT sensor can fail, or supply an incorrect signal if one or more of the following occur:
• Sensor open circuit.
• Short circuit to vehicle supply.
• Short circuit to vehicle earth.
• Contaminated sensor element.
• Damaged sensor element.
• Resistance in wiring harness.

Trev.

septimus · 26th August 2005, 03:53 PM

Thanks for the suggestion disconut. I will have a look and I have booked it in for a test book report next Wednesday so that might throw up a clue.

Thing that puzzles me is how the manifold pressure can be contained at some value in case of MAP failure as the wastegate valve, and hence the pressure, is controlled by the mechanical device which does not have any connection with the ECU. I wonder if this is another cut and paste from the Disco section?

**disconut** · 26th August 2005, 04:39 PM

The waste gate control is a "safety valve" arrangement to prevent blowing up the engine. The MAP sensor is about controlling the fuel flow to the engine and performance related.
I looked at mine then tried to understand how the waste gate could be connected to performance via the ECU. Easy, its not. It is a straight mechanical overpressure device.
The MAP sensor is the link. The default value may be set at atmospheric, or 6 to 7 psi to get you home again.
You may, as I have said before, be actually getting a low pressure in the intake manifold due to leaks etc, or a part blocked/split intercooler. I don't know if you can measure the boost pressure at a manifold point to ensure you are getting the full 15/17 psi there. I wonder why LR do not use a take off point from the manifold to control the waste gate? That way any small pressure drops would be compensated for.
Worth a look though.
Trev.

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