What is limp mode max boost w/ a Td5 Defender?

[jhealey]

Just been trying to find this for the past hour, and as much as I enjoying reading all the posts I can't seem to find it... Certainly found max boost for normal mode (1 bar or a little bit above... thanks Shifty!) plenty of times.

What is the max boost when the ecu is in limp mode in bar or kpa?

Just trying to work out some baselines to use to understand my turbo, and am wondering what the max boost I would see on my nanocom if the ECU has gone into limp mode...

Thanks!

 

[agew]

Limp mode doesn't affect the boost at all, just cuts injector flow/supply. It will kick in once the boost exceeds about 2.3 atm, and limit performance til you switch off and back on again (and until you then kick it over the limit again.......). Mines been doing this for months - haven't got round to proper job on waste gate as the heat shield is stuck (bolt on back of manifold is buggered) and drilling it off will take oooh minutes longer.....

I drive round it mostly, then forget and kick myself for a while, and swear I'll do the job 'next' weekend..... A

 

[jhealey]

Ahh, okay. I guess that should be obvious given that it's a mechanical waste gate not controlled by the ECU.

Yes, getting that bolt off the heat shield sounds like a job requiring a few pints for sure. You aren't able to adjust the wastegate rod without removing it though? On mine I can just get at it, which I'm going to do to try to up the boost since it appears I'm no where close to what it should be doing (max I've ever seen is about 140kpa on nanocom)....

 

[johnlad]

you can adjust the wastegate with the heat shield still fitted, 2 pair of grips sorts it

 

[agew]

Ahh, okay. I guess that should be obvious given that it's a mechanical waste gate not controlled by the ECU.

Yes, getting that bolt off the heat shield sounds like a job requiring a few pints for sure. You aren't able to adjust the wastegate rod without removing it though? On mine I can just get at it, which I'm going to do to try to up the boost since it appears I'm no where close to what it should be doing (max I've ever seen is about 140kpa on nanocom)....

Is your nanocom reading total boost or minus 100kpa we all live with.......?!?!? The 2.3 is 'gross' 1.3 'net' so to speak....

Cheers Johnlad - I'd read that turning the rod rather than the adjuster could damage the diaphragm in the controller, and I need to get as much access as I can the the wastegate as it clearly is pretty crudded up.. Having said that, a quicker job is more likely to get done some time soon of course...... A

 

[johnlad]

Is your nanocom reading total boost or minus 100kpa we all live with.......?!?!? The 2.3 is 'gross' 1.3 'net' so to speak....

Cheers Johnlad - I'd read that turning the rod rather than the adjuster could damage the diaphragm in the controller, and I need to get as much access as I can the the wastegate as it clearly is pretty crudded up.. Having said that, a quicker job is more likely to get done some time soon of course...... A

dont turn the rod,loosen nut, then hold rod with 1 set of grips and turn knurled section with other set of grips, giving it a spray of wd40 prior to adjusting makes it easier, once done re tighten lock nut, but without a boost box on the ecu, 230kpa is max at inlet manifold without triggering limp mode

 

[agew]

dont turn the rod,loosen nut, then hold rod with 1 set of grips and turn knurled section with other set of grips, giving it a spray of wd40 prior to adjusting makes it easier, once done re tighten lock nut, but without a boost box on the ecu, 230kpa is max at inlet manifold without triggering limp mode

Cheers JL - idiot-proof description, ideal for me to try...... but I fear I'll need to work on the wastegate itself to free it up.

Max inlet pressure 230kpa was what I was inadequately trying to summarise - i.e. 1 atmosphere plus the 1.4 from the turbo..... A

 

[Shifty1962]

Limp mode doesn't affect the boost at all, just cuts injector flow/supply. It will kick in once the boost exceeds about 2.3 atm, and limit performance til you switch off and back on again (and until you then kick it over the limit again.......). Mines been doing this for months - haven't got round to proper job on waste gate as the heat shield is stuck (bolt on back of manifold is buggered) and drilling it off will take oooh minutes longer.....

I drive round it mostly, then forget and kick myself for a while, and swear I'll do the job 'next' weekend..... A

Take the heads off the rivets that hold the heat shield mounting bracket to the heat shield leaving the bracket still attached to the manifold. I used an air powered die grinder on mine.

Then you have the space to work on the seized bolt. Be careful not to break it off in the manifold so give it a good soaking and if its still stuck heat it up with an acetylene torch until cherry/orange red at which point it will screw out with mole grips or similar.

Once you get it out replace the bolt with a longer stud and use a brass nut and large washer which wont rust or seize. Just use pop rivets to reattach the bracket to the shield. You need the bracket as a spacer to stop the shield collapsing when you tighten the nut. Alternatively leave the darn thing off which is what I did the last time I adjusted my turbo after engine break-in.

 

[agew]

Take the heads off the rivets that hold the heat shield mounting bracket to the heat shield leaving the bracket still attached to the manifold. I used an air powered die grinder on mine.

Then you have the space to work on the seized bolt. Be careful not to break it off in the manifold so give it a good soaking and if its still stuck heat it up with an acetylene torch until cherry/orange red at which point it will screw out with mole grips or similar.

Once you get it out replace the bolt with a longer stud and use a brass nut and large washer which wont rust or seize. Just use pop rivets to reattach the bracket to the shield. You need the bracket as a spacer to stop the shield collapsing when you tighten the nut. Alternatively leave the darn thing off which is what I did the last time I adjusted my turbo after engine break-in.

Nice one! Inspired to give it a good seeing to this weekend now. Cheers, A

 

[jhealey]

Agew -- to answer your question above regarding boost w/ nanocom, the pressure is measured at the intake manifold from the MAP sensor, so yes, it is gross pressure (ambient + boost), as opposed to gauge pressure, which is only boost pressure. So while the Nanocom would read about 200kpa at full boost, a gauge would read 100kpa, or 1 bar.

And so I have to think out loud...

From what I've read I should be seeing ambient pressure (here at 4200ft it's about 87kpa) + turbo pressure (in theory 100kpa), for a total of 187kpa. Whereas someone at sea level would have 100kpa ambient + 100kpa boost, for a total of 200kpa. And the ECU is programmed to go to limp mode around 220-230kpa so you don't blow things up.

On my nanocom the highest I've ever seen it to be is about 130-140kpa gross, which means I'm only getting about 48kpa boost. I've realized through my googling that turbos at altitude are not a simple matter, but I'm going off of one basic assumption now: unless you're at some pretty extreme altitudes, boost/gauge pressure should be roughly the same at sea level and altitude, whereas gross pressure will be reduced, since there's less ambient pressure to start with. I would assume the ECU would go into limp mode at 4,000 feet if it detects more 120-130kpa boost pressure, same as at altitude?

So planning on shortening the wastegate rod and some 3,000rpm tests on the ring road here in KTM at night, the only time when you can actually get above 40mph since there are fewer cows, carts, horses and homebrew tractors to share the road with...

 

[agew]

...............
So planning on shortening the wastegate rod and some 3,000rpm tests on the ring road here in KTM at night, the only time when you can actually get above 40mph since there are fewer cows, carts, horses and homebrew tractors to share the road with...

Not only had I not cottoned on to where you are, but you've totally ruined it now mentioning a ringroad !!??

No idea on altitude and turbo - your logic sounds good but I have no clue whether it stands up. Good luck! A