Club 80-90 Forums

Randolph, would love to plot the raw data for the 80-90 Wikipedia if you have it, for 70~75 cruising speeds, thanks

Ok, thoughts and observations..
Picked up the new stat today, and it is a 87 degree one. Removed the one fitted to the van, this looked very old and corroded. so definitely not a new one fitted when engine conversion done, this was also a 87 degree stat.
Fitted the new one and bled the system, first thing i noticed is how quick the engine got up to 90 degrees and stayed there. Took it out for a drive with slight trepidation, wondering how hot it would run under load. The coolant temp now operates so differently, it will rise to 91, then drop to 88 and stay in that small window. With the old stat, the engine would take an age to warm up to 75, then if you put it under a constant long load (like mountain pass) the temp would gradually rise to 92 then the first stage rad fan would kick in and drop it to 85.
So my thinking is the old stat was letting by and letting the engine heat the whole coolant system to 75 right up to 92 when the engine was hot. This is why the rad fan was kicking in at 92 engine temp (rad fan takes temp from rad not engine) so this proves that the rad and engine had no temp difference.
With the new stat, it's only opening when it needs to, to keep the engine at 90. And when it does open fully now, cooler water is entering the system
So i now at least have a proper functioning coolant system, and i'm quite hopeful for a increase in mpg. Even the VW garage confirmed the over fueling at cooler temps.
It's going to take a while to get used to it running hotter, but it has to better for the engine

TDIs take ages to warm up, they are a lot more thermally efficient and turn more of the heat into power rather than wasting it into the cooling system.
Early TDIs even had glow plugs in the cooling system to help them warm up quicker and also why you see TDI engined vehicles that have an auxiliary water heater to warm the cooling system up so you get some decent heaters!
I have found it surprising how many people put 80°c thermostats in TDI engined T3's, and how many people put oil coolers on especially without a thermostatic take off, just making a bad job worse.
I'm fairly sure that Mocal do a replacement oil cooler take off thermostat with a higher opening temperature for TDI vehicles that will replace the normal one in their take of plates.

Okay.
Mocal do 3 wax stats for the thermostatic take off plate.

WS82 - opens at 82°c - 85°c
WS85 - opens at 85°c - 92°c
WS95 - opens at 95°c - 110°c

They cost £4.25 ish retail, plus VAT.
I would be tempted to skip up one and go for the WS85 personally.

Simon.

I actually removed my external oil cooler when the TDI conversion was done and kept the AFN larger oil/water heat exchanger (it was a mocal thermo take off plate, with a 25 row rad) I'm going to monitor how it does heat wise, if it struggles to hold the temp around 90 degrees i may well fit a small 7 row cooler. But as you say the TDI runs so much cooler, i don't think i'll need it

right, i just filled up, got 20.44L of fuel in (always first click) and i had covered 233km since the last fill. By my calcs that's 32.24 mpg. The next fill will be with the new stat.
So, i'll update this as and when, or is there somewhere else you'd like me to log it?
speedo reading (km)------------------ litres put in-------------------------distance (km)---------------- mpg
-------------------------------------------------- 20.44----------------------------------- 233--------------------------32.24
327470

i just left my stat in from the AFN engine .. was that good or bad .. ?

not that my temp reads right anyway .. as i have a fault code on temp sensor .. have replaced with a VW new one ... but thats another story

matt

depends if it is faulty
From what i'm reading, the engine should be 90 degrees. Anything below around 80 and the ECU stays in warm up mode, meaning it injects more fuel = poor mpg

what sort of temp reading are you getting in morning when you first turn ignition on ? i guess around Air Temp for the day etc ?

Matt

i fitted a new temp sensor as well, new from VW...faulty out of the box was only changing it cuz i was doing the stat, meant i had to bleed the system twice. took it back for a refund. My sensor is blue and 3 times the price of the slightly later green one...
on first start up, as you say, around ambient temp. somewhere around 20 +/- 5

That's great Lloyd

32.196 mpg

I'll log the milos and fuel then, milo or fail to brim mistakes don't matter as long as the litres that went in are known accurately

Amazing the quality control of electrical car parts... dreadful. Imagine that in a RR Trent engine

This is really interesting, my AFN runs way cooler than 90, more like 70 round town I bet. My oil did get quite hot driving up The Grimsal Pass this summer (120*c) and I was glad of the oil cooler being there in this far from normal UK road conditions. Next job for me is the higher oil cooler stat (thanks Simon) and the water stat (thanks Lloydy) especially if it is really noticeable MPG figures. Never a dull moment with these engines is there

jed

Get a scangauge, you'll never look at the road when driving again
As for the coolant temps, the more i read, the more i find on the closer to 90 the better. The is a fair few people on the tdi forum fitting 95 degree stats, some are even making one stat out of two to make it open at over 100. it seems that most people who's temps are around 70, who then fit a new stat and are running at 90 seem to gain on average 4-5mpg. all found on here http://www.tdiclub.com/" onclick="window.open(this.href);return false; its not just economy either, meant to be kinder to the engine. I'll report back on here what i find, would be nice to gain a few mpg and the stat only costs £17 so no big loss

Hello,

I'm not sure if this is useful, but may help if still running a bit cool despite changing stats etc.

I found around town I was running under 90 degrees, and even sometimes on the motorway when it was cold out, so I rigged up a switch to make the ECU think it was running a bit warmer than it was. This didn't affect the gauge - I had many of these little tweaks, but I remapped my chips and was trying to get the running right. The below diagram and explanation shows how I included a variable resistor to change the reported temp value to the ECU (apologies as usual for my pathetic graphics skills)



Basically at 80 degrees the resistance over the temp sensor is about 300 Ohms,at 90 it's somewhere around 240 Ohms. That's read between pins 1 and 3 of the 4-pin temp sensor on the head flange - pin 1 goes to earth and pin 3 goes to pin 14 of the ECU (blue brown usually). If you get a potentiometer, somewhere around 10k e.g.:

http://www.maplin.co.uk/standard-potentiometers-2205

and use it as a variable resistor - put it in parallel with the resistance of the sensor. Connect pin 1 of the potentiometer to a wire which you splice into the blue/brown going from pin 3 of the temp connector to pin 14 of the ECU, and pin 2 of the potentiometer to earth.

Set the pot to maximum resistance first of all - that'll produce a similar resistance to standard. If you gradually decrease the resistance of the potentiometer the temp will read a bit higher. I would suggest using a scangauge and running that potentiometer to the front along with a switch. Then when on the motorway it's possible to switch it on and adjust the potentiometer to raise the reported temperature to the ECU.

Like I say - maybe this isn't of interest, but it helped me debugging my system.

Ewen

It's good to collect all this stuff in one place. Quite a few interesting threads on tdi's dotted about here and there. Would be good to wiki certain bits to stop them getting lost