MG-Cars.info

Welcome to our Site for MG, Triumph and Austin-Healey Car Information.

Recommendations

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGF Technical - MPI/VVC engine bay fan!.

Out of interest!.....

Is the trigger the same for the engine bay fan on the VVC as the MPI ?.

Spent the recent VERY hot weekend out and about with a fellow Fer, similar year/mileage cars except his VVC mine MPI!!.

The fan on my MPI was nearly allways on in slow traffic, and would nearly allways run-on after engine turn of, yet his VVC hardly came on, despite the heat!!.

No overheat probs with either car, just one of them "out of interest" type questions
Mark.L

Mark
They both use the same sensor to detect heat.
The 1.8 triggers at 75c, and the VVC at 85c.


Tony
Tony Harrison

Thanks Tony!. ;o)

That explains it then!.....well sort of!!, why the extra 10c for the VVC?.
Mark.L

Good question. I do not know, but some kind soul with more knowledge than us will be along soon.

Enjoy the summer sun.

Tony
Tony Harrison

>>but some kind soul with more knowledge than us will be along soon

I doubt it - we've been puzzling over this one for years! But, if anyone knows ...
Dave Livingstone

Yup - it's an on-going mystery for which there appears to be no obvious answer...

If anyone knows anyone at Powertrain who would be amenable to answering questions of this nature, then this is the time to start asking!
Rob Bell

Well Gents
As the fan is primarily there to cool the ancilliary components, Could it be to do with the distributor on the Mpi which the VVC doesn't have?

Tony
Tony Harrison

That's a thought Tony - clearly there is something unique about the MPi that necessitates a lower engine bay temperature. I don't think that distributors are necessarily that sensitive to temperature - especially given that the distributor on a K is bolted onto the end of the inlet camshaft on the side of the cylinder head. But I am sure that the answer may lie down that avenue of thinking...
Rob Bell

maybe the plastic inlet bits rather than the nice alloy stuff on a VVC?
Tony

Possible the VVC cam mechanism needs a greater supply of oil and the fact that the VVC can rev higher - therefore the temp effect on the viscosity is important.
Steve Ratledge

That seems very unlikely Steve - afterall, if that were the case, wouldn't one expect to find an engine bay heater for very cold days?

Doubt that it is a plastic plenum issue either - very low thermal conductance....
Rob Bell

Perhaps they were a bit bored one day and thought "this will get them"!!
Tony

Perhaps they specified the MPI first and then found that when they made the VVC version the fan kept tripping in all the time so they increased the switch temp spec for the VVC to stop customers moaning?
:-)

Bruce
Bruce Caldwell

I like Bruce's explanation :-)
Dave Livingstone

LOL - I can't decide whether Tony or Bruce are right!
Rob Bell

Are you sure you have not got VVC wrong all these years..........

Maybe it means Very Varied Cooling!!.

Now wheres my coat? :o(
Mark.L

LOL :)

Ok, another serious theory?
GUESS !!
I think the different switching relates to the materials used with the inlet manifold.
The only reason for the engine bay cooling fan is to cool down fuel-lines and injectors and prevent the fuel system from air bubbles.
(Don't beat me, I know, most of you believe it cools the whole engine ;) ..)

Anyway, alloy casting from the VVC has a much better temperature gradient than the plastic at the MPI.
Means, it heats up quicker and cools down quicker.
So the cut in temperature for the engine bay fan could be higher.

Regards
Dieter
Dieter

Well, one good thing about this thread is putting my mind at ease about my new VVC. Spent recent hot days wondering why the fan was only rarely on in the sort of circumstances that would have my old MPi whirring away nineteen to the dozen. Worried that something was wrong or, even worse, that I am getting old.

Chris
Chris Reeves

The engine bay fan after a fair run always comes on when I stop,VVC. Doing the same trip in my MPi nothing.
Interesting is the oil temp this gets to 110 in the MPi in a quarter of the distance compared to the VVC
Andrew Regens

>> The engine bay fan after a fair run always comes on when I stop,VVC. Doing the same trip in my MPi nothing.
Interesting is the oil temp this gets to 110 in the MPi in a quarter of the distance compared to the VVC <<

Odd that - doesn't make any sense does it? :o¤
Rob Bell

This thread was discussed between 28/06/2005 and 05/07/2005

MG MGF Technical index

This thread is from the archives. Join the live MG MGF Technical BBS now