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Old 29th May 2011, 00:23   #61
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Default Re: What limits rpm for an internal combustion engine?

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OT. - My rule regarding antennas:- Every signal carrying conductor will radiate, and receive, in copious quantities. Except the antenna, which will fall way short of its expected values. Regards
Sutripta

Or, as we like to say - in the real world, amplifiers oscillate and oscillators amplify

I'll dig up my old physics books (I hope I have some here) and do calculations for periodic interruptions in a moving column of air - let us see what that gives us.
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Old 29th May 2011, 00:31   #62
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Default Re: What limits rpm for an internal combustion engine?

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Or, as we like to say - in the real world, amplifiers oscillate and oscillators amplify
Hi,
Real world observation will be
Amplifiers and oscillators obey Murphy's law.
Amplifiers will oscillate.
Oscillators will just sit dead in the water.

Regards
Sutripta
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Old 12th June 2011, 16:18   #63
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Default Re: What limits rpm for an internal combustion engine?

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Regards
Sutripta

@Sutripta sir

I was reading out yesterday and found an article on tuned inlets on HowStuffWorks

It mentions similar calculations of length of the inlet, but then makes a point that the standing wave need not be at the fundamental - it can be a harmonic.

So for example 400Hz will require almost 1m long inlet, 1200Hx will require only 1/3rd as much - much more mangeable; and still provide most of the benefits
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Old 27th June 2011, 21:11   #64
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Default Re: What limits rpm for an internal combustion engine?

Hi,
Back after a hiatus. 'You've been qouted' is a great feature.

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Originally Posted by vina View Post
It mentions similar calculations of length of the inlet, but then makes a point that the standing wave need not be at the fundamental - it can be a harmonic.
That's why
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Originally Posted by Sutripta View Post
^^^
Still, why don't you think in the time domain. I do. The pressure pulse travels along the guide, and at any discontinuity, reverses with a phase inversion.
and (well, I agree this was cryptic), but you should have caught on.
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BTW, what sort of spectral purity can one expect from a half lambda dipole?
Regards
Sutripta
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Old 28th June 2011, 00:10   #65
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Default Re: What limits rpm for an internal combustion engine?

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Hi,
Back after a hiatus. 'You've been qouted' is a great feature.


That's why

and (well, I agree this was cryptic), but you should have caught on.


Regards
Sutripta

Welcome back sirji, can't tell you how happy I am to see you back.

Coming back to the topic - you give me too much credit - I'm not smart enough to decode your cryptic clues.


I have another question today - I have seen torque curves for some diesels and several get perfectly flat lines in the middle rpm ranges (e.g. MJD in Manza gets flat torque between 1700 and 3000rpm). How is that accomplished?

I mean there is no direct way of measuring torque in the car AFAIK, so even an electronic feedback is hard to make use of, and mechanical systems seldom have this kind of "perfection"
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Old 29th June 2011, 21:54   #66
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Default Re: What limits rpm for an internal combustion engine?

^^^
Hi,
You'll have to excuse my tardiness, at least till end of this week!

I really don't get your question. Why does the ECU have to measure torque. (Though an ECU, or governor, can calculate to a fair degree the torque/ power being produced.)

As to how/ why do some cars have a flat torque curve: limited rev range (diesel) = mild cam + turbo + plus optimisation of the advantage of diesels (low end torque) leads to a flat torque curve. The fact that diesels work with excess air also means (if we disregard emissions) torque is more a function of fuel injected (and properly burnt) than of air injested.

Regards
Sutripta
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Old 30th June 2011, 00:43   #67
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Default Re: What limits rpm for an internal combustion engine?

Quote:
Originally Posted by Sutripta View Post
^^^
Hi,
You'll have to excuse my tardiness, at least till end of this week!

I really don't get your question. Why does the ECU have to measure torque. (Though an ECU, or governor, can calculate to a fair degree the torque/ power being produced.)

As to how/ why do some cars have a flat torque curve: limited rev range (diesel) = mild cam + turbo + plus optimisation of the advantage of diesels (low end torque) leads to a flat torque curve. The fact that diesels work with excess air also means (if we disregard emissions) torque is more a function of fuel injected (and properly burnt) than of air injested.

Regards
Sutripta

If the ECU is doing it via negative feedback, then it has to somehow measure the quantity being kept constant - in this case torque.

If the engine losses are more or less linear with rpm (I believe they are, but not so much that you can get a perfectly flat torque curve. e.g. thermal losses will not be linear, on a per cycle basis they may be more or less at higher rpms) then yes, merely by measuring the fuel injected you can actually get a pretty good idea of torque.

Nearly flat is possible without feedback, but TATA MJD for example specifies perfectly flat torque
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Old 30th June 2011, 22:20   #68
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Default Re: What limits rpm for an internal combustion engine?

^^^
You get what you get. In this case aided by basic engineering and VGT. How perfect is perfect? Most certainly torque is not measured in situ.

Regards
Sutripta
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