I recall how well you understood the torque discussion...
Start with a compression ratio of 8:1, you'll get a decent temperature _before_ the fuel burns - a quick google suggests a few hundred C. You then burn, and it goes on up.
Shut the butterfly so there's only a quarter of an atmosphere in the inlet manifold. The air in there will be damn cold, and the 8:1 compression ration will only be an effective 2:1 or so.
The temperature won't go nearly as high.
Andy
Yes. I got the right answer. You did not.
Oh dear. Adiabatic heating is not something you understand anymore than enthalpy and entropy
sigh.
Thats why you have intercoolers,. to keep the inlet charge temeperatire LOW.
I give up.
And pray tell us why do you want the temperature low?
Andy
Well it was you that said you wanted it high. I was merely pointing out that people put systems on cars to keep it low.
Perhaps you have better explain to them why they are wasting their time
The air will be more dense and thus will contain a greater mass of oxygen per unit volume. When you want more power, it's easy enough to pump in more fuel but getting enough oxygen for optimum combustion is more problematic.
I know all about intercoolers and why they are helpful in addition to a turbo for cramming as many oxygen molecules into the cylinder as possible.
But do they play another role? Given that diesels run with an excess of oxygen rather than an approximately stoichometric mixture of fuel and air (as for petrol), why is it that intercoolers and turbos are as important for diesels? Is it that with wide accelerator settings, with a large injection of fuel, even a (normally aspirated) diesel can have too little oxygen to burn all the fuel?
I know very well the effect of a failed turbo on a diesel. My car had been into the garage to have a problem fixed that caused the engine to die a few minutes after starting (it was very reproducable as to which bit of road it would happen on!) and they removed the feed from the air filter to the turbo while they were working on it, and didn't tighten the jubilee clip properly afterwards.
A few days later I was driving along and the suddenly car started to lose power - it kept going, unlike with the previous problem, but didn't have anything like the power, and crawled up slight hills. Getting it to go above about 40 on the flat or 20 on a slight hill was a challenge. I'd booked it into the garage, and then something made me look under the bonnet and I saw that a 3" hose had come adrift from the turbo. As soon as I put it back and tightened it *properly* the car sprang back into life. I presume it was the input rather than the output, but maybe there is a failsafe on the turbo which causes it to stop working if it detects a problem with the input air stream such as unfiltered air, or lack of normal suction losses in air filter (ie the air input flows *too* freely).
In message snipped-for-privacy@brightview.co.uk>, NY snipped-for-privacy@privacy.net writes Snip
Umm.. Correcting the fault could have been as simple as stopping and re-starting a modern diesel.
Our Fiesta (2009) will do this. There is no dashboard indication that an exhaust filter clean is happening. The symptoms are a lack of engine power/zero acceleration. It remains in this mode until the engine is switched off and re-started. De-clutching and turning off/on has the same effect and saves having to stop. Particularly useful as this usually happens on motorways where the revs are high enough for long enough to trigger the cleaning cycle.
In article snipped-for-privacy@marfordfarm.demon.co.uk>, Tim Lamb snipped-for-privacy@marfordfarm.demon.co.uk> scribeth thus
My 2009 vintage Audi A6 diseasel does this on odd occasions, just needs a reboot;!..
It wasn't in my case. It was the first thing I tried. This wasn't the DPF in the exhaust. It was the pipe between the air filter and the turbo in the inlet.
I've never knowingly experienced a DPF cleaning cycle with my Pug 308. I'm sure it happens from time to time, but I've never had it lose some power. I have had that symptom (together with a "depollution failure" message on the clock/radio display) as I was accelerating out of a side road into traffic (seeing an HGV bearing down you when the engine has died is a heart-stopping experience). That was due to a pouch of fuel additive (probably similar to AdBlue that buses use) which had ruptured after a long life.
I rather hoped that TNP would admit he doesn't know. You've given it away now.
(He's the guy who thinks a car will accelerate best if you keep it at peak torque. I'm half inclined to give up on him)
Andy
Oops, sorry!
No. I do not.
Peak torque 'at the wheels' Peak BHP 'at the engine'
Thats what gearboxes are for.
I argued massively for peak bhp at the flywheel = peak torque at the rear wheels *with the appropriate gear ratio* and yet you still dont understand that difference do you?
I do know what is going on. The question wa sto establish wehther ir neot he did.
He doesn't. He is now confusing maximum power with maximum efficiency.
That was more likely Plowman. I don't recall TNP making such claims. BICBW
Certainly I did not.
I did argue thet the person who did PROBABLY understood the concept of 'peak torque at the wheels' being best for acceleration but misunderstood the fact that given an infinitely variable gearbox or some approximation theerof that equates to peak BHP at the flywheel ...
My apologies.
Andy
Erm no, that sounds like cruise control ?
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