Swapping sausages - TDI conversion thread

[Activ8]

"The limp mode isn't limp mode

The wastegate is broke"

I have plenty of boost until I go into 5th where at 3k the boost is vastly reduced, it doesn't return properly until the ignition is turned off and back on again. I don't know if it would cut the boost at 3k in other gears as I've never needed to hold it that wide open before, but that will be something for me to try.

The pumps are designed to rev to 4500rpm, but they can go a lot further. Been to 5400 in my AJT then backed off. The maps have kill switches at 6k, but don't go there without some serious engine mods. I've had the same problem about a year ago, in 5th gear the work round is feeding the revs/gas in much much much slower, which allows the maps to balance the fuelling requirement for more air. Fit a bigger compressor wheel producing more air for the same revs and the problem will go away. The 5th gear upgrade(s) can also produce this problem but dropping a gear to accelerate usually loses the problem as the higher revs increase the air produced to match the Smoke map fuelling.

[Activ8]

The old map was reading 5% more air than was flowing, the new one reads 5% less
The limp mode isn't limp mode
The wastegate is broke

OK
OK
OK

Driver request controls fuel but that is linked to air flow, the mafs could result in a 10% fuel difference - torque and smoke maps depend on what the maf 'believes' it is seeing - not actual right?

Drivers Requests suggests fuel, which is x referenced against torque map then smoke map.
Torque map looks up atmospheric pressure for protecting the gearbox and then applies a map limiting the fueling. T4's have 3 mapped limitations.
Next comes the Smoke map, MAF air intake calcs with the desired fuel IQ so it creates the Air Fuel Ratio limitation.
Torque map and Smoke map can limit the fuel as well as the temp maps.
So if the MAF is faulty but sending a signal, the signal will be x referenced against the mapped fuel in the Smoke Map protecting the AFR.
ECU will only allow the lower IQ fuel value of these 3 maps, assuming van up to temp (both fuel and engine)

Neither ECU recorded and faults (esp overboost) so was it realy limping?

OK, but are we're assuming the wastegate is seized closed tight, wide open or partly open, each of these would produce a different boost.
The limpmode can be applied softly for fuelling, temporarily by the ECU such as in boost limitations or permanently requiring an ignition reset or a replacement faulty part.

Is the boost map redundant as it drives the N75 or does it control Injected Quantity (IQ)*

The boost and N75 maps run independantly and at all times when the engine is running.
The 3 boost maps, set a single value never beyond limit, a target limit relating to the fuel and rpm, and a boost limit relating to atmospheric pressure and rpm.
The N75 map just runs all the time adjusting the N75 valve based on the rpm and the fuel.

Something is killing the fuel - I had my wastegate unplugged and had exactly the same effect - but a few seconds backing off and all was fine again, no faults recorded.

The ECU will be controlling the fuel based on its mapped parameters.
You've got to remember that your AJT is not boosting fully, its possibly being restricted by your IC / IC pipework but its still getting the correct air volume signal from the the MAF.
VCDS showed 460-480mg/s at tickover, the maximum air the MAF is mapped to is just 850mg/s. AFR at 850 is 21:1 ish (very very economical)
So even at a low boost level you should - for most parts - be able to drive it without any indication to suggest its not "working correctly".
It'll show up when the load (eg a hill) and / or higher rpm increases but your engine is underperforming.
You can back your foot off and return to mapping tolerances and normal driving as you're within normal map windows and tolerances.
Fix you IC plumbing or bypass the IC then have a run up the road to see if you get "the nearly limp mode".
Stick your VCDS on at the same time - Engine: Channels 3, 8 and 11.

[Dave Sausages]

I changed the manifold/ecu pipe again today, and fitted the standard ecu back on. Third and fourth it'll rev as much as bravery allows and no boost is lost, even got up a hill without it going into limp, only for it to happen on the next one. It is slow progress but I will get there. Whilst Reg and A8 give each other a technical reach around I'll just carry on and get it fixed

My technical theory is that 3mm I/d silicon hoses are dogshit and will be replacing them all for stock black braided lines, its because of the orange colouring in the silicon I tell you! I will also be dumping the car airbox as I also believe its inlet is restricted by the wing...

[spedwing]

I changed the manifold/ecu pipe again today, and fitted the standard ecu back on. Third and fourth it'll rev as much as bravery allows and no boost is lost, even got up a hill without it going into limp, only for it to happen on the next one. It is slow progress but I will get there. Whilst Reg and A8 give each other a technical reach around I'll just carry on and get it fixed

My technical theory is that 3mm I/d silicon hoses are dogshit and will be replacing them all for stock black braided lines, its because of the orange colouring in the silicon I tell you! I will also be dumping the car airbox as I also believe it's inlet is restricted by the wing...

Mine did the same yesterday , switched off and was fine on re start , Been ok today but if it keeps doing it I am gonna be mighty fucked off ! Bloody gay bar van [emoji13]


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[Activ8]

I changed the manifold/ecu pipe again today, and fitted the standard ecu back on. Third and fourth it'll rev as much as bravery allows and no boost is lost, even got up a hill without it going into limp, only for it to happen on the next one. It is slow progress but I will get there. Whilst Reg and A8 give each other a technical reach around I'll just carry on and get it fixed

My technical theory is that 3mm I/d silicon hoses are dogshit and will be replacing them all for stock black braided lines, its because of the orange colouring in the silicon I tell you! I will also be dumping the car airbox as I also believe its inlet is restricted by the wing...

Have you done a 5th gear conversion ?
Just eliminating the work throughs
. ..

OK
OK
OK


Drivers Requests suggests fuel, which is x referenced against torque map then smoke map.
Torque map looks up atmospheric pressure for protecting the gearbox and then applies a map limiting the fueling. T4's have 3 mapped limitations.
Next comes the Smoke map, MAF air intake calcs with the desired fuel IQ so it creates the Air Fuel Ratio limitation.
Torque map and Smoke map can limit the fuel as well as the temp maps.
So if the MAF is faulty but sending a signal, the signal will be x referenced against the mapped fuel in the Smoke Map protecting the AFR.
ECU will only allow the lower IQ fuel value of these 3 maps, assuming van up to temp (both fuel and engine)


OK, but are we're assuming the wastegate is seized closed tight, wide open or partly open, each of these would produce a different boost.
The limpmode can be applied softly for fuelling, temporarily by the ECU such as in boost limitations or permanently requiring an ignition reset or a replacement faulty part.


The boost and N75 maps run independantly and at all times when the engine is running.
The 3 boost maps, set a single value never beyond limit, a target limit relating to the fuel and rpm, and a boost limit relating to atmospheric pressure and rpm.
The N75 map just runs all the time adjusting the N75 valve based on the rpm and the fuel.


The ECU will be controlling the fuel based on its mapped parameters.
You've got to remember that your AJT is not boosting fully, its possibly being restricted by your IC / IC pipework but its still getting the correct air volume signal from the the MAF.
VCDS showed 460-480mg/s at tickover, the maximum air the MAF is mapped to is just 850mg/s. AFR at 850 is 21:1 ish (very very economical)
So even at a low boost level you should - for most parts - be able to drive it without any indication to suggest its not "working correctly".
It'll show up when the load (eg a hill) and / or higher rpm increases but your engine is underperforming.
You can back your foot off and return to mapping tolerances and normal driving as you're within normal map windows and tolerances.
Fix you IC plumbing or bypass the IC then have a run up the road to see if you get "the nearly limp mode".
Stick your VCDS on at the same time - Engine: Channels 3, 8 and 11.

Sent from my SM-G901F using Just T4s

[Dave Sausages]

yes bud, it has the .658

[Activ8]

yes bud, it has the .658

What gradient was the hill & what gear were you in when tackled hill 1 & hill 2?

Sent from my SM-G901F using Just T4s

[Dave Sausages]

5th gear in both, not sure on gradiants, but steep enough, Reg will know the hills. First hill, link road, coming from bideford after traffic lights from the new bridge, ragged it through 3 and 4, got it up to nearly 3k in 5th so didn't reach the limp threshold. 2nd hill was the next overtaking hill after the first, the one with all the awful potholes in the left lane. Not quite as steep as the first hill so got up to 5th 3k no probs and that is where it went limp again.

[arfur fox-acre]

yes bud, it has the .658

Spedwing , gay bar van????

The part where you loose boost and have a notable drop in power while going uphill. ..., mine does that. At the exact same point in the same two hills, regardless of gear used or how much throttle given.
Switch it off and on again and it's fine but may do the same on the next hill. Standard acv. Don't know if this helps, bet it doesn't.

And technical reach around. I refuse to play pool ever again after the last time I heard these words.

[Dave Sausages]

Trouble is roads are too busy to get a flat out in 5th on level ground to see if it goes limp there

[spedwing]

Spedwing , gay bar van????

The part where you loose boost and have a notable drop in power while going uphill. ..., mine does that. At the exact same point in the same two hills, regardless of gear used or how much throttle given.
Switch it off and on again and it's fine but may do the same on the next hill. Standard acv. Don't know if this helps, bet it doesn't.

And technical reach around. I refuse to play pool ever again after the last time I heard these words.

Yeah I get the power drop dude however as soon as on the flat it's like it's sort of half boost .. maybe not even that much , I thought it might be due to asking to much of an abl turbo , but soon as I turn off start again and it's all good ,


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[spedwing]

Trouble is roads are too busy to get a flat out in 5th on level ground to see if it goes limp there

How fast you going in 5th at 3 k ?


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[Dave Sausages]

It all helps, even if it's just like counselling, if we all talk through it together we'll find a solution, group hug everyone, but don't hold on for too long, it can get weird.

[Dave Sausages]

How fast you going in 5th at 3 k ?


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About 70mph

[spedwing]

About 70mph

I think I am nearer 80 or very close , do you know of anyone else by you who's had a Tdi done ?


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