Discovery 2 boost drop

sierrafery said:

Is your's Eu2 or Eu3 engine ?

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Eu3 it is mate

It is strange though because with the aap sensor unplugged I can still reach 1.4 bar then it drops to 1.2 how would this be happening if it is meant to be limited to 1 bar unplugged would the remap place have deleted it or is that not possible thanks

Being Eu3 nothing is logical anymore cos it has a very strange fuel map if the MAF was deleted as the original Eu3 engine management is calculating the fuelling based on MAF/rpm input so now it's some kind of Eu2 map addapted for Eu3 injectors based on MAP/rpm. Also the AAP/T sensor has different approach in both fuel maps, the inputs are different too between Eu2 and Eu3 AAP sensors ... only those who are doing these remaps know how they ''optimised'' everything (if they did) cos a Td5 can run apparently well with all kind of setups but that doesnt mean it's perfect and can appear various misbehaviours in time as the ECM has an addaptive strategy. IMO for Eu3 the best is to have a dedicated Eu3 fuel map and a genuine MAF sensor not some kind of "botched" fuel map with MAF deleted.

As you dont have access to a tester to diagnose it properly you can check something with multimeter cos you said the fuel pump is aftermarket... make the following test at idle https://www.landyzone.co.uk/land-rover/check-td5-fuel-pump-hp.358086/ then ask somebody to rev it up to 4000rpm for few seconds and watch if the voltage is dropping or not...even if the load can't be simulated stationary the fuel demand is still higher at high revs and maybe the pump can't cope with it.

sierrafery said:

As you dont have access to a tester to diagnose it properly you can check something with multimeter cos you said the fuel pump is aftermarket... make the following test at idle https://www.landyzone.co.uk/land-rover/check-td5-fuel-pump-hp.358086/ then ask somebody to rev it up to 4000rpm for few seconds and watch if the voltage is dropping or not...even if the load can't be simulated stationary the fuel demand is still higher at high revs and maybe the pump can't cope with it.

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Thank you I will give that test ago I spoke to the remap man who said he never touched the aap sensor so very strange why it dosnt limit itself to 1bar with it unplugged

It's no need to "touch" the sensor as long as the fuel map is completely mixed up within the limiter maps cos the AAP is used one way in a Eu3 map and different in Eu2 and it's deffinitely some kind of Eu2 setup without MAF so as the AAP input for Eu3 is different it may be already on a default. Like when you unplug the MAF on a Eu3 it goes to default to MAP/rpm and runs OK but the AAP is neglected as well cos the ECM goes to stored values in that status. The td5 fuel map is very complex and all kind of things are doable for the engine to run but once the tables are altered nothing behaves the same anymore... remappers who are making profit on this will not expose the "tricks" they made i'm sure, all they want is to make the engine run better than it ran on stock map so the customer to be happy, and that can be done in many ways... as long as the throttle response, consumption and the EGT are satisfactory i can't blame them just that such thing is very hard to diagnose if some problem occurs

the AAP/T sensor on EU3 is used for specific limiters which are different on Eu2 explained here https://discotd5.com/td5-tuning/eu3-specific-limiters

but the IQ is calculated based on MAF for Eu3 and MAP on Eu2 so as long as your's doesnt use the MAF the Eu3 limiters can't work like they were conceived so the AAP/T it's IMO neglected https://discotd5.com/td5-tuning/airmass

if you can understand those theories you can read all that web-page to see how a Td5 management works then you'll see that the fuel map for Eu3 without MAF is a ''bodge", i didnt even try to understand what the remappers are doing in such cases. The whole thing's gist is to get rid of the MAF which is expensive but IMO a Eu3 will run perfect only with that