Knock and Inlet Air Temp sensor testing

[S2central.net]

Woah - you need a bigger intercooler. Don't we all - thats the trouble with turbos - the efficiency drops off at the outer edges of operating range and air temps go up...

Then you need bigger intercoolers and/or bigger/more efficient turbos and you start on the slippery slopes... Go too large and you get lag and poor off-throttle performance.

Paul

[mcandmar]

Have you seen the IC on an AAN, its pathetic

[Rusty]

Hand waving turns into head slapping...

Just checked another ABY (Avant this time but also a brown Hitachi item) and the IAT measured 388 ohms as it was warm following a lunchtime drive. This compares favourably with my warm reading of 382 ohms.

Please could a few more ABY owners check the resistance of their IATs and give an approximate temperature. It only takes 2 seconds! Please also state teh manufacturer of the IAT in case the resistance differs.

Cheers for the tip-off on the water sensor, I'll see what I can do.

[S2central.net]

Have you seen the IC on an AAN, its pathetic

I know ! Its quite a limiting factor on the AAN engine dont you think ?

[twoqu]

Hand waving turns into head slapping...

Just checked another ABY (Avant this time but also a brown Hitachi item) and the IAT measured 388 ohms as it was warm following a lunchtime drive. This compares favourably with my warm reading of 382 ohms.

Please could a few more ABY owners check the resistance of their IATs and give an approximate temperature. It only takes 2 seconds! Please also state teh manufacturer of the IAT in case the resistance differs.

Cheers for the tip-off on the water sensor, I'll see what I can do.

Andy,

Tested two Hitachi ones off the car.
At 27C they both read 501 Ohms!
I'll let them cool down to ambiant and measure them again later on.

[Jamo]

Woah - you need a bigger intercooler. Don't we all - thats the trouble with turbos - the efficiency drops off at the outer edges of operating range and air temps go up...

Then you need bigger intercoolers and/or bigger/more efficient turbos and you start on the slippery slopes... Go too large and you get lag and poor off-throttle performance.

Paul

I'm framing this post, printing it out and waving it at all the people who tell me you can't have an IC too big

On a serious note is there an official calculation regarding IC size to bhp output?

[S2central.net]

Robin - those two of yours are deffo in-spec... And the two that Andy has seen are way off. I'll test tonight also.

As for that calculation Jamo - I only know of the maths to derive intercooler output temps from inlet temps given its efficiency - more usefully done the other way around of course. With enough air sensors in the right places it is quite easy to measure turbo and intercooler efficiency.

Paul

[S2central.net]

Oh and good old Scott has this info on the coolant sender - complete with graph.

http://www.sjmautotechnik.com/trouble_shooting/20vcoolt.html

[twoqu]

Hmmm..

I got 490 Ohms at 20C.
Andy PM me!

[kwlw]

Hmmm..

I got 490 Ohms at 20C.
Andy PM me!

I got 525 Ohms at 28C

Sau

[S2central.net]

Those last two readings look OK to me.

[jippo]

And i got 550 ohms at 50c from ABY engine.

[dkw_dude]

Measuring resistance..

I measured the inlet air temperature sensor on my 3B a while a go, and it was too low. But I didn't disconnect it while measuring (it was soldered on).

When I disconnected the measured values was correct. I think some circuitry in the Motronic is draws a tiny current when measuring, and the ohm values go low. In other words, disconnect at least one wire before measuring to get the correct result!

Nice to refresh the "electronic" part of my brain (I am a former radio/TV technichian).

[Rusty]

Cheers for all the readings. The original readings were done with the plug off and the readings on mine were done with the sender out the car on my desk at work. Hmmmmm, something is a liitle strange so I'll try a different DVM and see what readings I get...

5 minutes later...

Right, using a DVM that isn't completely wrong (god knows what the problem with the other one was), I get 537 ohms at what must be 40-50 deg as it's been sat for a while after the drive home from work. All seems in order to me! What a complete ball ache! Anyway, shows that it's in one piece and I'll take another measurement when I go for another drive in it. :mischeif:

Thanks for so many people for coming to my rescue, that's what I love about the S2Forum

[audiman]

This would all be so much easier if you just plugged vagcom in!! You can see everything you need to know. Temps and ign retard. But it sounds like your IAT sensor is duff. Would be nice to see what figure the ECU sees tho, it may just be 5 degs out, which wont cause your running problem?