HDi Running Temperature

[Ruan]

Whoa whoa, so much confusion in here.

Running lean (i.e. greater than around 16:1 - the point most Diesels run around) does NOT mean more heat - that's petrol land. If that were the case then as soon as you lift off the throttle then the temperature would go mental since you're running at more than 100:1.

Running a Diesel rich (i.e. blowing coal) gets things VERY hot. The more fuel you inject - the hotter your EGTs get. You eventually get to a point where MORE fuel will actually cool things down, but literally, the cloud out the back would be so bad and think the engine will probably be so badly bogged it would barely run - that's when you get a CHRONIC fuel bog on an 11mm pumped car at low RPMs, you inject so much fuel it cools it down, ends up boiling instead of burning and instead going out the back as white/grey smoke rather than black soot.

HDis don't put much heat into their coolant in comparison to XUDs, however, they should still all run at the same temperature - they always put a bit of heat in, enough to bring it up to temperature - they should sit at the 80*C mark if the cooling system is functioning properly.

Peugeots don't have the dash damping that VW do - the VWs have a range at which they'll display only 90*C - so from around 87*C to 95*C they'll just display bang upright - past there they'll go up or down... Other thing with Peugeot dashes - they tend to talk total bollocks - I've seen dashes that read 90*C regularly or 75*C regularly, the engines actually at the same temperature, it's just the dash talking bollocks.

[Mattcheese31]

Assuming the same amount of fuel is being pumped in, yes, that's exactly what i'm saying. But why take my word for it, there's this awesome place where you can find information about anything from why the sun comes up to why steve's missus is so fit, you might even have heard of it: google..? :p

i have my opinions i'm just interested to hear yours, seems easier to ask you directly than google your views . .

[Poodle]

No confusion, Ruan, if you burn x amount of fuel with y amount of air, the resulting combustion temperature will be cooler than if you burn x amount of fuel with 2y amount of air, assuming that y air isn't already able to burn 100% x fuel. You're getting confused and talking about injecting more fuel, rather than less air.

Fair enough Matt, sorry, thought you were disputing the physics behind it lol. To resume; if you're talking about the same amount of fuel with less air, then you get still-burning fuel going down the exhaust. The fuel itself takes some heat with it, and the heat the fuel would have produced inside the chamber gets produced in the exhaust instead, so never makes it into the coolant.

[Ruan]

That's precisely how it makes it into the coolant, rather that being in the cylinder and the excess air in the cylinder absorbing the heat, the slow burning diesel which is then making carbon and carbon monoxide as it's not got enough oxygen goes out the exhaust ports, which means going through the cylinder head, which is aluminium and will absorb the heat straight into the cooling system... That's where the problem lies...

A diesel billowing coal will increase egts and coolant temps like nothing else..

[Mattcheese31]

No confusion, Ruan, if you burn x amount of fuel with y amount of air, the resulting combustion temperature will be cooler than if you burn x amount of fuel with 2y amount of air, assuming that y air isn't already able to burn 100% x fuel. You're getting confused and talking about injecting more fuel, rather than less air.

Fair enough Matt, sorry, thought you were disputing the physics behind it lol. To resume; if you're talking about the same amount of fuel with less air, then you get still-burning fuel going down the exhaust. The fuel itself takes some heat with it, and the heat the fuel would have produced inside the chamber gets produced in the exhaust instead, so never makes it into the coolant.

let me think how i can be more condescending than yourself then i'll get back to you lol . . .

[Poodle]

So just to clarify what you're telling us here: gas is better at absorbing heat than liquid, and that X amount of fuel that's 75% burnt produces less heat than when X amount of fuel is 100% burnt..?

Because elementary physics says otherwise, just sayin'.

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@ Matt - best of luck with that, it's pure natural talent.

[Mattcheese31]

So just to clarify what you're telling us here: gas is better at absorbing heat than liquid, and that X amount of fuel that's 75% burnt produces less heat than when X amount of fuel is 100% burnt..?

Because elementary physics says otherwise, just sayin'.

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@ Matt - best of luck with that, it's pure natural talent.

i'm gonna put this out there, you claim physics . . .i claim you're wrong, stick that in your less powerful car than mine and smoke (or run lean) it . . .

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just to clarify, i'm not disputing the single equation you keep relating to, it's just the fact that you're looking at it in a very non-lateral sense . . .

[Poodle]

You've got me, i'm arguing the toss now lol.

Going back to the original point though, before we got sidetracked by coaling dts and semantics, i'm almost certain your hdi shouldn't be running that cool. And I stick by my point that running an fmic under normal conditions shouldn't make a difference to your coolant temps.

[Mattcheese31]

You've got me, i'm arguing the toss now lol.

Going back to the original point though, before we got sidetracked by coaling dts and semantics, i'm almost certain your hdi shouldn't be running that cool. And I stick by my point that running an fmic under normal conditions shouldn't make a difference to your coolant temps.

yeah and i disagree . . . . . but having an 8 month baby in one hand and a keyboard for the other i can't be bothered to argue . . .















but you're wrong . . .

[Poodle]

but you're wrong . . .

Funny, I was thinking exactly the same thing, great minds eh!

[Mattcheese31]

but you're wrong . . .

Funny, I was thinking exactly the same thing, great minds eh!

yeah what you wouldn't give to have one eh . . . . .

[Poodle]

[JJtheHITMAN]

I think people often get the running temps of diesels mixes up with petrols. Petrols generate alot more heat for a number of different reasons compared to diesel engines.

[Mattcheese31]

I think people often get the running temps of diesels mixes up with petrols. Petrols generate alot more heat for a number of different reasons compared to diesel engines.

so where do you stand? lol

[Toms306]

This thread still going!? Just drive the bloody thing, as long as the needle is somewhere between the white and the red it's fine!

[JJtheHITMAN]

The combustion process of petrol engines burn alot faster and initially hotter than what a hdi engine would, diesel engines create alot less excess energy, using half the amount of fuel at a lower engine speed than an equivalent cc petrol engine. After reading through the above im sitting on the fence, i would say a fmic would effect running temps but only on warm up, once at optimum operating temp and load i wouldn't think you would notice. So (imo) you are both correct. Thats me playing it safe LOL

[Poodle]

That's pretty on the money tbh, all trolling aside. Mine takes 15 minutes of a and b-roads to warm up, but mostly sits at 78* once it's there. That's bearing in mind both my glowplugs and coolant pre-heater are probably long dead tbf, but still. If i thrash all hell out of it for fifteen minutes straight it'll maybe see 85* lol, so to some extent the fmic will help it stay cooler.

[Mattcheese31]

after being in the van all weekend it runs at 75-76 under normal driving

[darrenjlobb]

Petrol / Diesel are the opposite, lean a perv and ull melt it, lean a derv and ull cool it, if your blowing coal, your making heat.

[JJtheHITMAN]

Petrol / Diesel are the opposite, lean a perv and ull melt it, lean a derv and ull cool it, if your blowing coal, your making heat.

Simple and spot on.