comparing engine run and afterrun operations...

[emirc 0]

OK so i have to write this because i can't set my mind to rest, i always suspect something is going wrong with my C and how it behaves :mad:

 

So, this is how my VR6 works:

When you start cold engine, its RPMs immediately jumps to around 1500 RPMs, then fall down at 1000 RPMs and stays there, and then steadily falling down to 650-750 RPMs range as engine gets warmer?

During idling and warming, engine temperature should be about 10°C higher than oil temperature? When fully warm and idle, engine is 90-95°C and oil is 96-100°C ?

 

This is how my C VR6 rests:

When you shut down the engine which was at its operating temperature (90°-95°), after-run fan and auxilliary water pump kicks in preventing hot spots. I timed how long they run, around 6 minutes and 30 seconds. Then they both shut down at the same time. Then i turn ignition on and see how much temp. has dropped. It was 74°C for oil according to MFA, and little over 80°C for engine. Is this OK?

 

This is what troubles me:

1.When fans and aux. water pump begins its work, after approximately 1 minute, the air blowing through radiator gets cold, while fans and aux. pump still work for 5.5 minutes as i described above. If the aux. water pump circulates water around engine head, shouldn't it be logical that water should go through the radiator too? It seems my fans doing their work for nothing :?: Shoudn't there be a hose that connects aux. pump and radiator so that hot water from engine head can cool down? Or maybe it's flow rate is just not enough for me to notice when i put my hand to feel blowing air temperature?

 

2. Now, this one happens anywhere between 80°C and 90°C engine temperature and oil 90-100°. When I shut down fully warmed engine, fans and aux. kicks in as it should. THEN, while after-run doing its job; I give ignition on, fans SHUT DOWN but aux. water pump still works!!! I turn key back all the way to off, fans again START and aux. keeps working. Is this NORMAL VR6 procedure? Why does my fans behave like this when i give ignition?

 

3. When engine is over 90°C and oil is like 120°C, lets say after some racing time, this doesn't happen, i.e. fans don't shut down when ignition on, they keep working together with aux. water pump. I suppose this is OK because it's logical.

 

Thank you for reading, i couldn't explain it any shorter. :oops:

[Kevin Bacon 5]

When you start cold engine, its RPMs immediately jumps to around 1500 RPMs, then fall down at 1000 RPMs and stays there, and then steadily falling down to 650-750 RPMs range as engine gets warmer?

 

Normal. You're getting 100% fuel thrown in for about 20 crank turns (depending on ambient and cold water temps) and a wide open idle valve duty cycle. That's the 1500rpm thing, it's to get the motor started. The gradual falling from 1000 to 680 is the cold running map, which switches off at 70 degrees water temp.

 

During idling and warming, engine temperature should be about 10°C higher than oil temperature? When fully warm and idle, engine is 90-95°C and oil is 96-100°C ?

 

Why do so many VR owners worry themselves stupid about the temperatures? They're normal. Both gauges are absolutely miles off, especially the water temp guage. 90 on the guage is 100 deg actual.

 

When you shut down the engine which was at its operating temperature (90°-95°), after-run fan and auxilliary water pump kicks in preventing hot spots. I timed how long they run, around 6 minutes and 30 seconds. Then they both shut down at the same time. Then i turn ignition on and see how much temp. has dropped. It was 74°C for oil according to MFA, and little over 80°C for engine. Is this OK?

 

Yes.

 

1.When fans and aux. water pump begins its work, after approximately 1 minute, the air blowing through radiator gets cold, while fans and aux. pump still work for 5.5 minutes as i described above. If the aux. water pump circulates water around engine head, shouldn't it be logical that water should go through the radiator too? It seems my fans doing their work for nothing :?: Shoudn't there be a hose that connects aux. pump and radiator so that hot water from engine head can cool down? Or maybe it's flow rate is just not enough for me to notice when i put my hand to feel blowing air temperature?

 

The flow of the aux pump is piss poor, it's literally just to give a little movement in the block's water galleries to prevent localised over heating round the back, nothing more. It won't flow through radiator, especially if water temp has dropped to 80 deg and the thermostat closes.

If the air is cold after a minute, the fans have done their job.

 

2. Now, this one happens anywhere between 80°C and 90°C engine temperature and oil 90-100°. When I shut down fully warmed engine, fans and aux. kicks in as it should. THEN, while after-run doing its job; I give ignition on, fans SHUT DOWN but aux. water pump still works!!! I turn key back all the way to off, fans again START and aux. keeps working. Is this NORMAL VR6 procedure? Why does my fans behave like this when i give ignition?

 

Ignore the aux pump behaviour, that always comes on with the ignition and stays on for 10 mins after you switch it off, regardless of temperature.

Only fan speed 1 is direct to battery, speeds 2 and 3 are ignition fed only.

 

3. When engine is over 90°C and oil is like 120°C, lets say after some racing time, this doesn't happen, i.e. fans don't shut down when ignition on, they keep working together with aux. water pump. I suppose this is OK because it's logical.

 

Thank you for reading, i couldn't explain it any shorter. :oops:

 

I don't there's anything unusual going on there, just drive it and enjoy it or you'll end up being signed off work for stress :lol:

[dr_mat 0]

Re: run-on fans vs ignition on fans ..

 

Two *completely* different circuits. The run-on circuit obviously thinks the fans should be "on" during this time, but the ignition-on fan control thinks it should be "off".

 

In fact, the run-on circuit can't control the fans separately from the aux water pump, so if it's keeping the water pump on it has no choice but to keep the fans on too.

 

Like mr StrawFlex said, forget it, just drive the bloody thing.

[emirc 0]

Much more clearer now, thanks mates!

 

But i still can't figure out why would they (VW engineers) keep run-on fans working for more than 1 minute if there is no water circulating through radiator? Why didn't they make separated circuits? When engine is off, fans are cooling only water stored in radiator, right?

Remaining water in engine block can't be cooled if there's no main water pump running, and aux. pump obviously recirculating HOT water through the engine head and there's no heat exchangers in aux. pump hose system..?!

 

Ignore the aux pump behaviour, that always comes on with the ignition and stays on for 10 mins after you switch it off, regardless of temperature. 

 

I'm afraid this is not the case in my... case. It comes always with the ignition, yes, but if engine is cool (below 80°C) it won't stay on after switching ignition off.

I also don't find that possible if its true what dr_mat is saying, i.e aux. pump can't work in ignition-off mode without the fans also working.

 

Like mr StrawFlex said, forget it, just drive the bloody thing. 

Strawflex :) .. Yeah, forget it and just buy yourself a new battery every month, 'cause run-on fans are sucking all the power for no good reason! :?

[Kevin Bacon 5]

The run-on fan is governed by the thermostatic switch in the radiator and is independant of the after run pump. If the radiator thinks it's hot enough to need fan assistance, then it will switch them on, simple as.

 

New battery every month? Ah, you're not the same guy with the current draw problems are you?

 

If your so unsatisfied with the way VW designed the coolant system, redesign it and show them how it should be done ;-)