** SOLVED ** Limited manifold pressure reading

This site contains affiliate links for which LandyZone may be compensated if you make a purchase.
tom1979

tom1979

Well-Known Member
Full Member
Posts
2,141
Location
East of England, UK
hi all looking for some advice. Recently had my TD5 Defender remapped by Dynachip and we noticed the MAP reading was maxing out at 172-173. He said it should be getting at least 210kpa.

Two boost gauges confirm around 15psi at wastegate and inlet. Air flow is 600+

So far I have:

Allisport intercooler
straight through side exit exhaust
New inlet manifold and gasket
New turbo (wastegate not adjusted)
New quality intercooler hoses

I am at a loss as to why the boost is being limited so low. Does anyone have any ideas?
 
Last edited:
What boost are you trying to achieve? Stock turbo is easily capable of 32psi or more. Just watch your exhaust gas temps. It sounds like your unadjusted turbo wastegate needs adjusting. I'm assuming you have had the overboost limp setting raised on the remap? You can get a modified MAP sensor from Gary at Alive Tuning which helps with higher boost pressures.
 
I’m told it should be getting 210kpa without any problems or modifications. Dynachip was surprised there was no black smoke after his remap, I don’t know what he did about a boost box thing but it’s not going into limp mode. Would the fuel pressure cause something like this? It’s pretty much the only thing I’ve not checked
 
Dynachip’s boost gauge located at the turbo side was reading 23psi (with a turbo that had the wastegate shortened). That equates to 155kpa thereabouts.

I think I’m getting confused between kPa and psi but I did think 220kpa was “normal” which I am not getting
 
tom1979 said:
It was 173kpa which he thought was low. Driving or stationary it goes up to and stops at 173
Click to expand...
So the readings given are from a separate boost gauge and not the indicated MAP readings and you had exactly the same max reading on both turbos? Have you tried adjusting the wastegate to get more or less max boost?

I find it very coincidental that both turbos would read "exactly" the same max boost (unless adjusted to do so) but could understand the readings if the MAP was faulty as that would be the common denominator. Have you cleaned the MAP or tried a new one?

Without a boost box or modified MAP sensor the stock ECU mapping will not tolerate much more than 18psi before switching to limp mode to protect the engine. If the remap has modified the limp threshold (not as simple as it sounds) then you can run extra boost but unless the fuelling has also been matched to the extra boost you risk warping the exhaust manifold pulling or snapping the exhaust studs, burning the exhaust valves and seats, and running the turbo too hot for the oil to cool properly.

The one thing guaranteed to kill a TD5 is overheating. They just don't like running hot.

I ran my TD5s at between 18psi to 21psi (no idea what that is in kPa as my gauges don't indicate them) because much more than this leads to elevated EGts. I ran boost boxes with Stg2 Alive maps with additional throttle position tweaks to take out the harshness.
 
The ambient reading is low which is 89 kPa it should be nearer 100, however even with it unplugged and defaulting to 100 the readings are the same.

MAP sensor is clean, tried different ones the reading is the same. Reluctant to start messing with the wastegate until I’m seeing proper readings etc as it may only mask another problem

The only thing I haven’t done is checked the fuel pressure but not sure how this would affect the MAP reading.

Maybe the loom is damaged somewhere

Also found today that my hi/lo switch is reading backwards however the readings are the same in high and low.
 
Last edited:
This maybe a long shot but what clamps are you using on your turbo hoses?
I ask this because my TD5 was fitted with so called "heavy duty" pipe clamps which when looking they were substantial pieces of kit.
Aprox 25mm wide stainless steel wrapped around the pipe and an 8mm screw to tighten the clamp to the pipe. LOOKING SOMETHING LIKE THIS.
upload_2017-10-8_15-30-44.jpeg

Now the issue with is clamp was when fitted to the hose at the turbo it absorbed so much heat from the turbo and the nearby exhaust that it expanded.
When it expanded it acted like a pressure relief valve allowing turbo pressure to escape. When cold all was fine and always when I checked with a diagnostic reader the turbo pressure was fine (the clamp was cooler).
I only discovered the problem because in the area around the turbo hose on the turbo its self was a clean area, a ring around the area which looked like it was constantly being blown off with an air line. replacing the HD clamp with STD SS jubilee clips low turbo pressure when hot resolved.
.
 
Tim4x4 said:
This maybe a long shot but what clamps are you using on your turbo hoses?
I ask this because my TD5 was fitted with so called "heavy duty" pipe clamps which when looking they were substantial pieces of kit.
Aprox 25mm wide stainless steel wrapped around the pipe and an 8mm screw to tighten the clamp to the pipe. LOOKING SOMETHING LIKE THIS.
View attachment 133066
Now the issue with is clamp was when fitted to the hose at the turbo it absorbed so much heat from the turbo and the nearby exhaust that it expanded.
When it expanded it acted like a pressure relief valve allowing turbo pressure to escape. When cold all was fine and always when I checked with a diagnostic reader the turbo pressure was fine (the clamp was cooler).
I only discovered the problem because in the area around the turbo hose on the turbo its self was a clean area, a ring around the area which looked like it was constantly being blown off with an air line. replacing the HD clamp with STD SS jubilee clips low turbo pressure when hot resolved.
.
Click to expand...

They’re just normal jubilee clips. The ones that came with the Samco intercooler hoses I bought are stainless steel. I don’t think it’s being lost as the gauges are both reading about the same around 15psi (103kpa). So the map sensor should be reading the 103kpa + ambient = around 203kpa

I’m suspecting either a fuelling issue or a dodgy loom. As said in a previous post I have a 15p loom on a 10p engine but general opinion is it doesn’t matter
 
Last edited:
tom1979 said:
They’re just normal jubilee clips. The ones that came with the Samco intercooler hoses I bought are stainless steel. I don’t think it’s being lost as the gauges are both reading about the same around 15psi (103kpa). So the map sensor should be reading the 103kpa + ambient = around 203kpa

I’m suspecting either a fuelling issue or a dodgy loom. As said in a previous post I have a 15p loom on a 10p engine but general opinion is it doesn’t matter
Click to expand...
I pretty sure the loom is a red herring and not the cause of your problems. When I changed my 10p for a 15p engine I retained the 10p loom with no issues. When I had oil in the red plug I then fitted a 15p loom again with no issues.
 
Then I’m at a loss with it! Turbo is producing 15 or so psi, inlet is getting 99% of it via the allisport intercooler - not sure why else the readings would be low.

Turbo boost/Inlet pressure is 15-17ish psi / 100kPa ish
AAP reading is in my opinion a bit low at 89kpa

Turbo is standard and people with standard turbos and even standard maps are getting 200+kPa so I don’t know why I’m not. I don’t want to just shorten the waste gate as it may cover the problem, plus I had a turbo with a shortened wastegate that maxed out exactly the same

Could it possibly be fuel pressure?? It’s the only thing I’ve not checked but I reallly can’t see how it could be related
 
Probably bout that according to the internet - it’s a new turbo and I’ve not touched the wastegate rod. The previous turbo was churning out 23psi (158kpa) and the map reading was still 172ish.

The gauges take no account of ambient, so there is 15-17psi in the manifold 103-117 kPa (the map sensor would read this + ambient)

Regardless of what the aap says the air pressure is not 89kpa it is just over 100. So I should be getting 205-220 kPa MAP reading. But I’m not I’m getting 172 whether the revs are are at 2500 or 4500. Is this in turn cutting fuel? Dynachip really was expecting some black smoke after his remap but he said he loom was wrong and that what’s causing problems - although everyone is telling me it makes no difference

Thought about changing the AAP sensor but the part number MHK100820 which hopefully is 4 wire to match my 15p loom is listed everywhere as a manifold sensor! Also I don’t know if this needs any sealing in the air box? The 3 pin one that was in there had it’s own little space but the 4 pin one I had to make fit. HOWEVER with the AAP unplugged I get the default reading of 100kPa with no change to the MAP reading

Hopefully someone can have a quick look at my excel spreadsheet and see if these figures stack up to what’s normal

I may be wrong about all of this as I don’t have another vehicle to compare to
 
Last edited:
Also tried a different AAP as mine reads low, this one read even lower but still getting a similar “limit” on the manifold presssure reading.

67324867-99CF-472D-A690-804C5DC7F947.jpeg

Aside from the AAP, is there anything else that may limit manifold pressure readings?
 
You must log in or register to reply here.

Similar threads

Gunter Shingleditch
Freelander 1 TD4 puff of smoke on start-up, stinky exhaust and shudders at 1000 RPM - SOLVED
Replies
16
Views
3K
Arctic2
Arctic2
MikeFl4
P38A M51 Diesel - Lumpy idle after rev - Setting the top section of the pump?
Replies
4
Views
2K
Datatek
Datatek
gstuart
Disco 3 (LR3) P0046-00 (28) Error / hopefully resolved
7 8 9
Replies
165
Views
27K
tyregeezer
tyregeezer
4
Freelander 1 MAF Readings Decreasing with Increased Throttle - Solved
Replies
4
Views
2K
4Bee4Bee
4
dinisrosa
Defender td5 10P - no air pressure
2
Replies
38
Views
4K
dinisrosa
dinisrosa
Back
Top