Thread: TD5 overboosting with boost box, need to alter my ECU tune?

Ideally I'd like to run maybe 23PSI boost, but I can't do that at the moment, even with a boost box (but I could until recently). I've run through a ton of troubleshooting myself and I'm left thinking my TD5 no longer acknowledges boost boxes for some reason, or my S1 ECU tune that's like 12yrs old needs an update with boost limits raised. Dunno!? I'd appreciate any thoughts. Kinda a long post but just wanted to confirm my troubleshooting. In reality it's like a diary entry of my 10hrs of troubleshooting.


My 2000 disco 2 still going strong at almost 300K. Got a S1 ECU tune about a decade ago, have EGT monitoring and 18 months ago I got a boost box and enjoyed up to 25PSI (measured by boost guage from an input coming into the inlet manifold). An example of a previous nanocom recording with boostbox fitted (so doctored MAP figure) working well was....
Idle: AAP=97; MAP=98; MAF=55
0-90KM/H with max accel: AAP=86; MAP=202; MAF=631
50-70KM/H with max accel: AAP=86; MAP=204; MAF=631
Refer to Baseline attachment for full CSV. Note I live 400m above sea level, and at this time I did have a restriction in the air intake which I have since sorted and now only see an AAP reduction of about ~6 upon full demand.


Everything seemed to go well until 12 months ago when I started to get overboosting issues. This appeared to possibly happen (I'm not 100% certain) the same time I replaced the regular IC for an Allisport full-sized IC (for a manual), and I gave the standard tranny cooler the flick and relocated a P38 cooler. I was also having an exh manifold leak at ports 1 & 5, which was worsening (noisy but not screeching). I thought maybe this was maybe contributing to it?


I attended to the exh manifold (installing a de-webbed one moving forward), and as the turbo was original, I'm sure the seals were stuffed, so opted fto lash out ~$1k and install a Allisport hybrid turbo. Still have overboost issues.


I've also run through the following troubleshooting:

• Tightened and checked hoses = doesn't appear to be any leaks
• WG modulator only 18 months old but tried bypassing all the same = no improvement
• WG actuator wasn't stuck on my old turbo, certainly isn't on my new hybrid turbo
• Another boost box came with the hybrid turbo and swapping one boost box for the other = made no difference
• Tried another earth for the boost box = no improvement
• Checked all under-bonnet fuses are ok (especially F2) = they were ok
• Disconnected MAF - overall poorer performance but gee 0-50km/h was a hoot from ? overfuelling. Less fuel-cut off overboosting as it couldn't even get there performance wise
• Disconnected MAP - very poor performance (did have boostbox installed when I did that)
• Checked the ECU pins = all ok
• Changed fuel filter = had only done 30k and no improvement + my issue doesn't appear to me to be related to starvation
• Confirmed MAP reading vs my analogue boost guage from seperate input on inlet manfold same. Removed boost box and tried several situations: It appears boost guage is indeed accurate
  
  • MAP~230 AAP~94 GUAGE~18.5PSI (calculated figure = 19.7PSI)
  • MAP~160 AAP~97 GUAGE~10 (calculated figure = 9.13PSI)
  • MAP~124 AAP~99 GUAGE~4 (calculated figure = 3.6PSI)
  • MAP~233 MAP~95 GUAGE~19 (calculated figure = 20PSI)
  
  
• Clean MAP, MAF & AAP with MAF cleaner = nil change

Only Nanocom faults are EGR & overboost related (+ inlet air when I disconnected it).


Here are some nanocom recordings of the issue I am experiencing (boost box fitted with these examples and my accurate reading boost guage only goes up to 20PSI):
OB Issue Example 1
Idle: AAP=98; MAP=99; MAF=59
Accel from 50-80KM/H: AAP=94; MAP 241; MAF 663


OB Issue Example 2
Accel from 50-80KM/H: AAP=94; MAP=232; MAF=609


OB Issue Example 3
Idle: AAP=99; MAP=99; MAF=59
0-80KM/H: AAP=95; MAP=239; MAF=627




The reason I think my TD5 no longer acknowledges a boost box is I did two same manoeuvres (0-60KM/H), one with a boost box connected, and other without and there wasn't any different with the MAP readings (or at least the MAP wasn't reduced with the boostbox):
0-60KMH No Boostbox
AAP=94; MAP=232; MAF=554


0-60KMH with Boostbox
AAP=94; MAP=240; MAF=611




Anyway, not sure what to do. Left thinking the uprated IC was the last straw and I have an "old" tune from 2012 and the final combination of mods has asked too much?? My sensors are proper Siemans/VDO, Bosch. I haven't swapped them, but plan to in a weeks time as one of the final troubleshooting options left with someone else's TD5. I've heard of a duel channel boost box but my MAF doesn't seem to be the issue, it's the MAP reading. Could I simply need a revised ECU tune that raises the boost limits? Or am I missing a mechanical issue?

Originally Posted by Kaaaiju

I got a 4 bar map sensor installed and my tune updated for that and MAF limit changed and run 30-40psi with no boost cut cheaper and more accurate way instead of a boost box

Can you post a nanocom log up of this vehicle hitting 40 psi?

I'd be interested to see that, after all we are all here to learn.

That is an impressive figure, 40 psi is 2.75bar.

I've run 2.2 bar boost which I believe is roughly the limit on a TD5 ECU once you take ambient pressure into account, as the ECU uses signed 16 bit software it can only read a maximum map figure of 3.27 bar, if you subtract your ambient reading from that, you will get the maximum boost that the ECU can ever run.

Several years ago when I was learning about tuning and ECU's, I didn't realise the ECU had this limitation, but Offtrack explained it.

Having said that, if you have enough restriction at the airbox, under full boot at those figures, you could get 0.85 bar ambient pressure which would give you a theoretical boost reading of 2.42 bar (3.27-0.85), but of course you aren't really producing 2.42 bar boost over genuine ambient pressure, just over the restricted airbox pressure.


Anyways, a log file will clear all that up!

Cheers
James