Thread: First run of new evo-logged Air flow circuit HIGH

Hi Philip,

The rollover to 0 on the MAF will definitely will cause problems.



What I've done is graph the 3 accelerator ways, the wastegate, c11-c10 is manifold pressure less ambient pressure, and c9/6 is airflow divided by 6 simply so it fits into the graph

The accel way traces indicate you are on the throttle from 51 -> 56 seconds.

Boost peaks at 52 seconds with an airflow peaks at second 53. You can see the airflow hit 0 at 55 seconds, but I suspect that the ECU has started limiting performance at some point between 53 -> 54 seconds. Even though you haven't altered the throttle position boost has dropped and wastegate modulation has dropped to zero. So the ECU is clearly cutting performance in response to the MAF rolling over to 0.

So the issue is why is the MAF over reading? It can happen if the engine is over boosting but that doesn't appear to be happening here. The maximum boost I can see is just under 18psi.

I'd be suspecting the MAF is out of spec. You could try measuring the resistance between pins 1-2, 1-3, and 2-3 - but I'm not exactly sure what figures would be indicative for an overly sensitive MAF. Mturri posted some figures for new units so that might be a starting point.

I'm half inclined to think it's a cheap aftermarket MAF as they have a reputation for over reading. Check to see if it has either VDO or Siemens markings on the MAF body, if not it's likely a cheap one. I guess most people wouldn't be hitting 4200rpm so wouldn't pick up on this kind of misbehaviour.

cheers
Paul

Originally Posted by OffTrack

The over boost condition doesn't usually trigger a fault so you have to diagnose by recording the fuelling inputs.

Not sure if Defender is different, but Nanocom records Overboost on my MY05 Td5,

I could not get overboost condition on the Tombie Map but I can on the Td5inside map if I screw the wastegate rod in too far.

Overboost put the ECU into Limp , Turn key off & restart , If I overboost again the Nanocom even counts the number of overboost events

a very handy thing. Over boost fault condition clears with nanocom.

its really an excellent gadget and worth its weight in gold.

Originally Posted by goingbush

Not sure if Defender is different, but Nanocom records Overboost on my MY05 Td5,

I could not get overboost condition on the Tombie Map but I can on the Td5inside map if I screw the wastegate rod in too far.

Overboost put the ECU into Limp , Turn key off & restart , If I overboost again the Nanocom even counts the number of overboost events

a very handy thing. Over boost fault condition clears with nanocom.

its really an excellent gadget and worth its weight in gold.

I was going off my experience with an overboosting D2 Td5. I could hammer up a hill with the engine kangarooing due to overboost and still not get any over boost faults logged. My point to Philip is that just because you don't see a fault it doesn't mean the condition isn't occurring.

The ECU records and logs faults to it's internal memory. The Nanocom just reads the stored information from the ECU.

As far as I'm aware the Td5 ECU "limp mode" doesn't exist in the same sense as Auto ECUs. The ECU will limit on certain conditions but there is nothing in the design of the ECU that requires a power off, and power on to clear a fault.

cheers
Paul

no probs,

Might just be the latest remap ??? but my Td5 Defender doesnt kangaroo on over boost, it just over boosts once & then goes limp. (MIL dosent illuminate) have to switch ignition off & restart to be able to overboost again.

be interested to hear if its the same with other Def Td5's


have to agree with your point tho, when I unplug my MAF I dont see a fault condition on the Nanocom , but we know there is one !!!

Originally Posted by goingbush

no probs,

Might just be the latest remap ??? but my Td5 Defender doesnt kangaroo on over boost, it just over boosts once & then goes limp. (MIL dosent illuminate) have to switch ignition off & restart to be able to overboost again.

be interested to hear if its the same with other Def Td5's


have to agree with your point tho, when I unplug my MAF I dont see a fault condition on the Nanocom , but we know there is one !!!

I think the big difference is the D2 has the wastegate modulator, so there is a degree of electronic control over boost. I think this might effect the way the ECU handles overboost on the D2. I've had a couple of logged over boosts but far few than the number of over boost events and definitely doesn't put the ecu into limp mode.

Obviously Defender and D2 Td5's ecu's are similar rather than the same.

cheers
Paul

looks like new MAF time.
The LR original part is about $200 landed from LR direct.
I note a VDO aftermarket for about $120 landed.
I know that everyone warns about aftermarket but VDO IS Siemens.

Regards Philip A

The land rover genuine is made by VDO/Siemens. OEM like VDO/Siemens is perfectly fine.
The aftermarket kit people warn about are cheap knockoffs of unknown provenance.

I've had a VDO MAF in my D2 for the past couple of years and it seems to be fine.

I've attached a segment of a recording from mine with revs peaking at 4069rpm. Airflow peaked at 644. I'd been thinking mine was possibly under reading but on the basis of this I doubt that is actually the case.

Incisor has enabled CSV uploads with a maximum file size of 130kb.

cheers
Paul

Everyone has hit the proverbial nail on the head. The MAF is over/ falsely reading and cutting fuel.

Try another one phillip, and yes VDO etc is OEM and I have had NO issues with them.

We were chasing a similar issue for quite some time a year or so ago with a VNT installation on a D2a, funnily enough it would also happen at about 4000rpm... Pete Bell was fantatstic in his help with this problem.

New VDO MAF and readings were down to 655max, and no more overboosting symptom/ fuel cut .

JC