** SOLVED ** Limited manifold pressure reading

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Are these "on road under load" figures as you will never get a turbo to boost anywhere near max free revving? Something to do with one of those fancy physics laws such as Boyles or similar. I know I should have paid attention at school.
 
I used to find a good long road with an incline then in third or fourth gear give it the beans so the engine was pulling from about 1.5k rpm. You should then see the turbo pressure peak at just after 2k rpm through until about 4k rpm where it will start to drop away again. Just watch yoiur speed as it is easy to get carried away. I seem to recall that if I was doing 50mph in fifth (about 2k rpm in my Defender) and floored the pedal the boost gauge would jump almost instantly up to max. I no longer have any LR TD5 vehicles to confirm this. Free revving it would never go much beyond 4 or 5 psi.
 
Free revving it i get 15psi ? Dropping to around 10psi. Whether driving or stationary the MAP reading will not go beyond 173ish but the gauges confirm 15psi (roughly 100kPa) so including ambient it should be reading around 200? Am I wrong?

I suspect that the incorrect AAP sensor is causing issues
 
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Shifty1962 said:
Are these "on road under load" figures as you will never get a turbo to boost anywhere near max free revving? Something to do with one of those fancy physics laws such as Boyles or similar. I know I should have paid attention at school.
Click to expand...

tom1979 said:
Here’s a spreadsheet showing the values being driven. Note that high is low and low is high

https://www.dropbox.com/s/zmdbhmtvwlhl4hz/tom 08102017-3#00000000000000000#636430562180119264.xlsx?dl=0
Click to expand...

These were the figures being driven.
 
tom1979 said:
Free revving it i get 15psi ? Dropping to around 10psi. Whether driving or stationary the MAP reading will not go beyond 173ish but the gauges confirm 15psi (roughly 100kPa) so including ambient it should be reading around 200? Am I wrong?

I suspect that the incorrect AAP sensor is causing issues
Click to expand...
You may be right but when I changed out my 10p engine for a 15p crate engine it came with all sensors and I never had to modify the AAP to fit the 10p loom. In fact I was not aware there were different AAPs available, It was virtually just plug and play except for a few cooling hoses.
 
Shifty1962 said:
You may be right but when I changed out my 10p engine for a 15p crate engine it came with all sensors and I never had to modify the AAP to fit the 10p loom. In fact I was not aware there were different AAPs available, It was virtually just plug and play except for a few cooling hoses.
Click to expand...

According to http://www.discotd5.com/ecu-reverse-engineering/aapaat-sensor-swapping

"EU2 and EU3 engines are fitted with significantly different airbox sensors.
The EU2 uses a three wire Ambient Air Pressure sensor, while the EU3 uses a four wire Ambient Air Pressure/Ambient Air Temp sensor.
The curve of the AAP portions of the two sensors are different and require different parameters to give the correct reading.
Without adjusting the parameters there is a misread of around 10kPa. You'll get an over-read ( -700 m altitude) with EU2 AAP + EU3 tune, and under read (+700m altitude) with EU3 AAP + EU2 tune.
The problem is not so bad with EU2 AAP + EU3 tune as the engine assumes higher air density in some correction maps and will INCREASE injected fuel and give a 0.1 bar increase in the boost limit. The boost level is MAP - AAP so reducing AAP by 0.1 results in boost levels 0.1 higher than the would be with correct setup. I suspect this is why you often hear the comment that an EU3 tune drives better that the correct EU2 tune.
If you've addressed the issue by installing a 4-wire sensor - replace airbox lid, sensor and run an extra wire back to the ECU - the problem occurs when you want to run an EU2 map on the motor. The under-read means the ECU uses corrections which reduce the fuelling plus the boost limit is reduced by 0.1 bar. It guarantees bad performance.
The fix is in
The way to fix this problem is to use the correct parameters for the AAP you have installed. Search for the values for the base map and replace with values for the sensor you are using.
EU3 - 4 wire sensor
multiplier: 13171 ( 0x3373 )
offset: 267 ( 0x010B )

EU2 - 3 wire sensor
multiplier: 10410 ( 0x28AA )
offset: 1227 ( 0x04CB ) "

So basically using an EU2 (3 wire sensor) with an EU3 engine/ecu will result in an over-read and increased fuelling, using an EU3 (4 wire sensor) in an EU2 engine/ecu will result in an under-read and reduced fuelling.

Whether this is causing a fault which is then limiting the manifold pressure reading I have no idea, but I do know I have had ambient pressure circuit faults in the past which I thought nothing of.
 
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OK. Thinking about it when I changed engines EU2 to EU3 I never touched the air box. So I've been referring to the MAP sensor on the inlet manifold with the AAP sensor in the air box - DOH!. AFAIK the MAPs are the same on all TD% variants.

However when I changed out the oily loom from a 10p to a later 15p one I never had to swap any sensors or connectors so I have no idea now.
 
One thing I would be interested to know is if the AAP generates a fault and limits the boost to 1bar - how does it physically do this on a Defender with no boost modulator.
 
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tom1979 said:
One thing I would be interested to know is if the AAP generates a fault and limits the boost to 1bar - how does it physically do this on a Defender with no boost modulator.
Click to expand...
It will cause the ECU to reduce fuelling by changing the injector timing hence affecting the energy in the exhaust gasses spinning the turbo. At least that's what I reckon. I can't see how else it could do it without a boost modulator like the Discos have.
 
The only thing that concerns me is it does it even when there isnt a fault code. I need to test it more to see. Perhaps it’s just underfueing due to the lower AAP reading, at least I’m hoping it’s that simple!
 
PROBLEM SOLVED!!!

Turns out having the wrong AAP has buggered the ECU - the wires don't go to the same places on the ECU. Wired up the old 3 pin AAP and problem remained although correct AAP being read. Tried a different ECU (that has never been in the vehicle) and it was fine! So need to find a NNN000120 ECU now....

Thanks to everyone for the help and suggestions! I'm now getting 221kPa MAP reading under load and around 210kPa at a standstill.
 
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Shifty1962 said:
At least you got to the bottom of it. Nothing worse than an intermittent or untraceable fault. Can't help with an ECU but give Gary a call at Alive Tuning as he often has some for sale or may be able to repair your existing one.

http://www.alivetuning.com/landrover/
Click to expand...

I spoke to them and they reckon they might be able to fix my existing one so popping it in there in a few weeks.
 
Last edited:
tom1979 said:
PROBLEM SOLVED!!!

Turns out having the wrong AAP has buggered the ECU - the wires don't go to the same places on the ECU. Wired up the old 3 pin AAP and problem remained although correct AAP being read. Tried a different ECU (that has never been in the vehicle) and it was fine! So need to find a NNN000120 ECU now....

Thanks to everyone for the help and suggestions! I'm now getting 221kPa MAP reading under load and around 210kPa at a standstill.
Click to expand...
Hi guys I'm having same low reading problem with my eu3 disco 2 auto 89kpa actual pressure is about 101kpa. It has been mapped with eu3 map. Could it be that sensor wires differ on different maps?
 
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