Exhaust gas temp question

Basic tuning, as I understand it, is you put in more fuel, but, if you get to the point where it smokes, that means unburnt fuel, so you need more air.

More air, and then you can do more fuel. Till it smokes again, then more air...


Right up until the point where something melts.

Boost on the turbo (now I only know about mechanical engines, but it must be the same on the td5) automatically increases fueling, by a feedback path to the pump. Ie more air commands more fuel.

(I know you know all this!)

In light of the above, if you've reduced the boost, its getting less air. If its pumping the same fuel, that would cause smoke (but the temp should still be less, as the fuel just wouldn't be burning in full)

So...

Its hard to understand why the temp is so high!

Slightly more complex being under ecu control but yeah that's pretty much it. With air con/climate control completely off I've now got it to idle at about 250c but as soon as you turn it on and deman a little bit of load it jumps to 350c. But yeah I share your bewilderment. I have a Delphi diagnostic laptop, I think I can read some sensor values from that so I'll chuck that on it and see if I can find out some map sensor readings if anyone can translate them into "good" "not so good"

Think I may have just found the issue. I let manifold pressure as read by the ecu (presumably from the map sensor) is 100.5kpa.....which if I'm not mistaken is around 1bar (14.7psi) this is at idle. So am I right in assuming that it would be trying to fuel to compensate and possibly causing the high temps? Either way an idle map reading of a bar can't be right surely?

Oh, no, maybe that's me being thick. That's just atmospheric pressure.....d'oh. So the map sensor may very well be reading correctly and it does increase to about 190kpa when you rev it up to around 3.5-4k rpm

190Kpa is low under heavy load adjust the wastegate back a bit to get up to 240max cos at 242 is the overboost limit also the MAP sensor is 2 in 1 it's the IAT sensor in there too and that can cause issues as well... at idle the MAP should be = with the AAP sensor reading if that works OK.... only a complete live data log from a trip would be really relevant

Thinking about that aircon thing, you should remove the drive belt and do a short test by running the engine without it cos what if there's some load created by a faulty aircon clutch or other sticking pulley which is not enough to rip the belt but forces the engine?

what a great idea
remove the drive belt how far are you expecting to travel with out the water pump running ?

why not just install a boost gauge to see if the engine is boosting at idle

ozzyboydeano said:

what a great idea
remove the drive belt how far are you expecting to travel with out the water pump running ?

why not just install a boost gauge to see if the engine is boosting at idle

Click to expand...

Depends what else you have and whether you have a shorter belt to try with...

be real mate not many people have different size drive belts on tap

and if one did have a shorter belt to bypass the air con the air compressor would need to be removed

so why not add a boost gauge to see if the engine is boosting @ idle

ozzyboydeano said:

be real mate not many people have different size drive belts on tap

so why not add a boost gauge to see if the engine is boosting @ idle

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You'd be surprised what a Landy owner keeps in his/her toolbox spares bin ...

Are you 100% certain that the probe is not touching the manifold?

Also its not as though belts are expensive, £12 last time I bought one. A cheap gauge will be £30+ and won't read true, mine is a cheap-ish boost gauge but runs 2 - 3psi out

ozzyboydeano said:

what a great idea
remove the drive belt how far are you expecting to travel with out the water pump running ?

why not just install a boost gauge to see if the engine is boosting at idle

Click to expand...

re-read my post m8 and the others too...i said FOR A SHORT TEST... to see any change at idle cos if it gets 200 then the problem is solved

boost at idle? ... now that's interesting.... though if you'll read this thread with attention you'll see that the OP made manifold pressure measurements with tester

sierrafery said:

re-read my post m8 and the others too...i said FOR A SHORT TEST... to see any change at idle cos if it gets 200 then the problem is solved

boost at idle? ... now that's interesting.... though if you'll read this thread with attention you'll see that the OP made manifold pressure measurements with tester

Click to expand...

sorry m8 I jumped in with both feet as I had scanned through the thread I do apologise

it be a mixture of things IE alternator also pushing to hard as well as climate control

it could be normal for a different turbo fitted though compared to stock readings

specially if the ECU has not been mapped for the different size inducer and exducer turbines

I'm not sure how long it's been running these temps as I've only put the sensor on it in the past day or two and it's done about 80 miles so far. It was sat for 3 months prior to that and had the turbo fitted about a month before that. Between fitting the turbo and it standing it towed a loaded car trailer up from Cornwall for well over 7 hours non-stop and didn't suffer.
And yes the exhaust is completely clean apart from the odd little hazy puff setting off up a steep hill[/QUOTE]

I would say your gauge might not like that instant heat or its not designed to see such a flow .... you being towing and other driving styles with no over heating issues.. you are reading inferior readings from your new EGT set up

I've towed several times with no issues, once towing a car from Cornwall back up to Yorkshire. I have a boost gauge and it doesn't boost at all at idle and reaches a max of 15 psi.
Even if I run around with the aircon completely off it still runs the same temps.
I have ordered a cheap £25 egt gauge and probe off eBay to see if i reads anything different to the £250 AEM one that's in it at present.
And yes I'm 110% sure the probe isn't touching the manifold, I can adjust the length of it using a lock nut crushing an olive and made sure it's as close to the middle of flow as I can.
I just can't see why a gauge from a reputable manufacturer wouldn't deal with the exhaust flow of a circa 130bhp diesel tractor but is expected to be fine for a 300bhp+ car.
I had a blitz egt gauge in an Impreza not so long ago and that would take a reading from just after the turbo in the downpipe and read absolutely fine, most I ever saw from that was around 600 degrees after being on track for 20 minutes.
So, recap...
Back on standard boost
No boost box
Unmapped
Bigger intercooler
Egr delete
Decat and full stainless exhaust
Clean air filter and box
No smoke
Drives fine
Tows fine
Boosts fine
Had two (soon to be 3) gauges and probes reading the same
Fresh fuel and filter
Turning off everything that could load the engine makes no difference
Coasting downhill in gear drops the temps to around 200-250, soon as fuel is introduced either at idle or under load the temp climbs to 400+c maxing the gauge if it's under slight load (constant 40-50mph on flat ground)
Short of taking it somewhere to get mapped and see if the readings change or they find something on the fuelling side I'm a bit stumped.
But thanks for all the wisdom and suggestions thus far guys, big help