Merci, mon ami!

(5 days of French language for me Tony, as our French friends have arrived on their twinning visit)

Pas problem! Ca va

Thinking about moisture etc didn't one of the Grand Prix teams experiment with a little steam injection into the mixture, my memory suggests possibly BRM - oh my age keeps throwing up spurious info, haven't googled it but seem to recall coverage on Tomorrows World which would place it late 60's early 70's - again my age rears its ugly head to dispell the myth of my dashing good looks(Mmmmmmmm!)

8.30 en France and the tall ships are out on the Bay already, couldn't have been such a good Fete last night!

Salut

I thought it would create a bit of a discussion. I raised the question as I did restrict the intercooller inlet in my Fabia Tdi in the winter. Easily done by removing the off side black panel surrounding the fog light. Afriend of mine who lives in France was a professional diesel engineer, he has a Golf GTD and he reckons you should stop the intercooler working in the winter, and has even fabricated a moveable engine air intake so that the engine air can be taken from the rear of the engine when it gets really cold.

Diesel fuel needs the hot, compressed air to ignite, so why cool it down in winter to a point where it is too cool? The compression by the turbo warms the air up but hardly enough to need to cool it down again especially if a lot of the plumbing is exposed to the blast of cold winter air coming through the radiator and other vents in the front of the car.

But having said all of that, if I can't get to the air intake on the Yeti the problem doesn't arise.

I am also a mechanical engineer and I disagree with that particular french engineer on this topic.

The only time your engine will struggle to ignite the diesel is on startup when the engine is cold and the cranking speed is low. In fact your engine is fitted with glow-plugs to help start combustion when the engine is cold. Once the engine is started and past those first few thousand revolutions, you will have no problems at all. Ambient temperature variations of 20 degrees C mean very little to cylinder compression temperatures of around 500C.

All those non turbo diesel tractors, trucks, forklifts, pumps etc work just fine in winter (actually better due to the previously mentioned colder and denser intake charge) and they have intake temperatures lower than any intercooled turbo diesel does.

If you have no problems with a non-turbo engine sucking colder air, what is the problem with a turbocharged engine getting warmer air?

As for the air-density argument. Your car has a MAF sensor (mass airflow sensor) which measures the mass of air entering the engine. It's smart enough to know when the air is colder and denser. If the air density is soo much greater than required then your engine is also fitted with a variable vane turbocharger. The engine can reduce boost if it doesn't need such an increase in density.

On the idea that the turbo doesn't heat the air much, I call *******s and I have measurements to prove it. At 15psi boost you can easily see 105C coming out of the turbo. At 20psi you can see 135C. Actual numbers depend on the ambient temperature and the efficiency of your turbo compressor. My measurements fit well with 70% on a 20C intake.

Bottom line, there is no reason to do this. But I should point out that some engines in some cars have an intercooler bypass circuit. Not for cold weather, but to help burn the DPF clean. Bypass the intercooler and it raises intake temperatures which directly raises exhaust temperatures.

Edited 22 July, 201213 yr by Kiwibacon