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Banned
Join Date: Nov 2017
Location: Australia
Posts: 2,060
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It's interesting.
For more than 30 years I've been writing about amateur car modification done through through test and development, not guesswork.
It was about that long ago that I started measuring engine intake system restriction and writing about it. This technique allowed people - at basically no cost - to measure the restriction of each section of the engine intake, from the entrance to the air box right through to the throttle body. From this, it was easy to work out whether the intake flowed well or badly, and if badly, which sections were causing the most restriction. For example, this approach quickly showed that on standard and near-standard cars, the filter caused very little restriction (typically less than 1 inch of water) at full power - and so swapping to a 'high flow' air filter was pointless. Basically, the measurement approach was (and is) like using a flowbench - but one that has as much airflow as the engine.
I won't bore people with detailed tales of measuring suspension natural frequencies with a smart phone and vibration app (so taking into account not just spring rates but also motion ratios and weight acting through that spring), or using a low cost accelerometer to plot the on-road torque curve of the engine, so allowing very accurate measurement of changes in on-road performance.
But when I came to this group, I was rather surprised that aerodynamic 'test and development' seemed to comprise only some tuft testing and a lot of mileage testing. (And both are excellent approaches, but the mileage needs to be over long distances to be accurate.)
But what really stunned me was this idea that people could just follow a so-called optimal shape (a template) for all sorts of aerodynamic modifications.
What modifications, then? Well, how about:
- guiding the shape of extensions to cars
- guiding the heights of spoilers
- assessing the 'aerodynamic purity' of car shapes
- determining where there would be attached and separated flow
It was all quite bizarre - I'd just finished writing a book on modifying car aerodynamics, written with a top UK car aerodynamicist working as a tech adviser, and I'd never even seen reference to such a template in any of the SAE papers, IME papers or published textbooks on car aero!
What on earth was going on?
I soon discovered that was all the imaginative work of one man - there was in fact nothing that supported any of the above points. He'd taken one of the aerodynamic low drag shapes of the 1930s and then extrapolated it to all these present-day (pretend) applications. And he'd persuaded all these discussion group people, who knew very little about car aero, to accept it as The Chosen Way.
Well, that's OK - you see lots of absolute rubbish on car forums, but much to my astonishment, not only did the one man refuse to countenance that he was just taking things just a m-i-l-e too far, all* the people who had been sucked-in to this fantasy fought back furiously when the template approach was condemned!
*With 2-3 notable exceptions. They read what I wrote (especially the part - well don't believe me, go and read the references, or do your own testing, and find out for yourself) and went off and did that... only to find that, yes, the template was all absolute rubbish.
So, no worries, as we say here. Some on-road tests that I could develop and post would soon show two things: (1) the template didn't match reality, and (2) aero testing of aspects such as panel pressures, lift/downforce and even drag would soon show how better results could be achieved at low cost and with relative ease.
But no, people were so lost in the weeds of misinformation that it was like starting a discussion about engine management without anyone knowing what fuel injector duty cycle was. I mean (for example), why care about aero lift? No-one seemed to be aware of the significance of induced drag, i.e. drag caused through lift. So I'd patiently explain all this, expecting the appointed expert to immediately chime in and agree - yes, we really should have been looking at lift coefficients all along if we wanted lowest drag. (About a basic point as: 'no, we don't want injector duty cycles of 100 per cent'.) But not a bit of it! Lift was irrelevant - low drag shapes automatically had low lift, apparently. So I'd go back to my textbooks, and check that I was right. And yes, there it was, high lift causes induced drag, so better to have zero lift. But how can we measure lift? So - well, here is a dead easy way of accurately measuring lift and downforce! Here's how to do it - now you can too. No guesswork needed! But no, why would we even want to do that?
And so it would go on: basic stuff, in all the textbooks, that didn't fit to misconceptions of the expert, were always argued against. Other people, completely lost in the technicalities of the discussion, wouldn't go off and read anything, or test anything for themselves, but would side with one or other of the two personalities.
I became increasingly impatient - if people were seriously that stupid, did they even deserve any help? And then some new person would pop up, obviously wanting to improve their car's aero - and looking for good help. And immediately the group would chime in, often (not always) giving really terrible advice to this poor person.
So, with less and less patience, I'd try again - hey guys, you do realise that this is all just rubbish you are posting? And back would come the replies: you just think you're soooo good, you have some sort of psychosis, etc, etc. And I'd think, well yes, I am starting to think I am so good. When I was dealing with the real car aero experts while writing my books (multiple experts gave feedback on each of my books) I'd be utterly humbled by how little I know, but in the company of this group, I am starting to think myself a bloody genius.
But guys - don't believe what I write here, go and read the references, or do your own testing, and find out for yourself.
Empower yourselves!
Ah, hell no, that's too much work and effort: instead, gotta dribble crap here.
It's really sad, because improving car aero is fascinating topic, and awesome to do on cars, and obviously many people here want to achieve great outcomes.
But all of that becomes massively harder when misinformation is rife and revered, testing methodologies are a decade or more behind the times, and - and I think this is the key point - people just don't want to think or research or test anything for themselves.
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