Club 80-90 Forums

Anyone taken logs of air intake temp on a tdi?

Anychance you can post them up and say whether you are running no cooler/intercooler or charge cooler?

Mine with an obscenely badly mounted intercooler behind rear light reached the dizzy heights of 85 occassionally peaking at 87

Anyone?

All these ETdi's going on, someone must have an OBD port and vagcom, or at least the installer gave you a full run down of 'whats what' ?

I'll try and do this soon - trouble is I don't have any plans to go very far imminently, so I'll have to put my foot down a bit in town to get the high temperatures! I have an intercooler fan which is actuated by the ECU at WOT and also when the intake temperature gets over 50 degrees Celcius. I can see when boost is constantly high for 15 seconds or more, this kicks in and then switches off again below 35. At normal motorway driving at the moment it's off, but when driving round France in the summer it was on most of the time during the day when it was hot.

Will have a go at logging soon and post the results up

Ewen

Ewan, where have you sited your charge cooler?

Hi Tom,

I have an air-air intercooler which is sited in where the original airbox would have been on the left side behind the left rear light cluster. Airflow is down the vent and there's a baffle at the bottom to direct air to the low pressure area around the exhaust right angle bend - seems to work pretty well to me, but I'll try and make a log file and stick the graph up here soon.

Ewen

Hello,

I managed to take some logs this morning on the way to work - I boosted at about 23psi sustained for a while to get the fan to come on - highest temperature around 54 Celcius I think - once the fan kicks it it's pretty good at keeping the temperature about that. There are four logs - 2 homing in on the bit where I was boosting hard on the bypass up a hill in 5th - there's one for boost and one for temperatures:

temperatures:



boost:



temperature full:



boost full

Nice data !

Cheers Andy,

I saw the loom you'd made the other day - quality work indeed!

Ewen

How do you get data like that.....what software / kit do you need.....

Hello,

you just need a diagnostics plug and vag-com, then some sort of plotting software - I use one that I downloaded from the tdiclub forums, but oridinarily I just use excel - I've posted up using excel charts before - that's the simplest I reckon.

if you have a JX then you can't get these figures I don't think - the OBD2 port comes from the tdi ECU K line which monitors all this stuff for you.

Ewen

i have a tdi ahu now...with the dignostic port.

i dont have a lead or vagcom though.....

what do I need to buy...

thanks for the reply by the way!

Hello,

ah right - that's good then. You can get vag-com from here (now called VCDS Lite)

http://www.ross-tech.com/vag-com/" onclick="window.open(this.href);return false;

and you need a cable like this:

http://www.ebay.co.uk/itm/USB-VAG-COM-4 ... 3357e97877" onclick="window.open(this.href);return false;

for example - there are lots out there. Can be a bit of a faff setting up (depending on your system) - let me know if you have problems and should be able to help you out.

Ewen

Brilliant thanks Ewan

ewenmaclean wrote:Hi Tom,

I have an air-air intercooler which is sited in where the original airbox would have been on the left side behind the left rear light cluster. Airflow is down the vent and there's a baffle at the bottom to direct air to the low pressure area around the exhaust right angle bend - seems to work pretty well to me, but I'll try and make a log file and stick the graph up here soon.

Ewen

Genius! Got any pics Ewen?
Not that I'm a diesel fan, but I'd kind of thought that this is a critical detail to make oil coolers, located in the same position, get any useful airflow through the matrix. As I understand it, the T3 has (by design or bad luck) a positive pressure engine bay, maybe a relic from the Aircooled engine?
If you drive a bus with the hatch locks undone, the air pressure differential will force the engine cover to pop up! Making use of the low-pressure zone behind the vehicle would seem to be a useful trick for any oil or charge-coolers and so avoiding those heavy and pressure/flow killing long runs to the front of the bus.

Hello,

I can't claim anything clever myself really - Russel fitted the intercooler - I've just messed about with the baffle design and stuck a fan on it. The modified baffle actually currently points sideways into the engine bay - the high velocity air passing over the baffle at that point creates a pressure differential from the air going though the vent. It may well be even better if it pointed out behind the van - not sure -I'd have to check.

I measured the air pressure using a pressure sensor below and above the intercooler going at about 50 and there is definitely a not insignificant pressure difference. Intercoolers won't do much good in my opinion unless there is this pressure difference either over the air-air intercooler itself, or the radiator of a water-air chargecooler. I think doing this pressure test is pretty vital if you want to find out how the air is flowing over the cooling element.

My thinking is based on the RAM effect and Bernouilli principle. At the top of the air intake at the back the RAM effect comes into effect as the air is significantly slowed at that point causing an area of relative high pressure, and at the bottom the fast moving air passing under the van and across the baffle causes a low pressure. The fan helps reduce the pressure lower down, and is particularly useful when stationary after a period of heavy boost - then the pressure differentials are pretty much the same and none of this matters.

The fan light (spare led slot) tells me when the intake temperatures are over 50C and it only comes on really under serious sustained boost - very rarely on the motorway, except for a bit during a particularly hot day last year in the South of France - not a great deal you can do about that unless you start introducing liquid nitrogen which I know is possible but a step too far for me!

I'm sure you're right about the engine bay positive pressure - but I think this is due to the RAM effect higher up - underneath the engine where the air flows I don't think this is the case, however I stand ready to be corrected! I am no expert at all, so look forward to more learned opinions!

Ewen

(P.S. will try and take pics soon - no camera at the moment due to techno-idiocy and beer)