09 August 2008

Tyre Pressures for High Grip Levels

Having had discussions regarding severer edge wear on the Auris 2.0D4-D (and T180's) many including myself have increase tyre pressure on the fronts to as high as 38 and 44psi levels. I looked into the theory and carried out weak non scientific practical “test” to see how safe this is. We all know low pressure is dangerous, but what seems to less understood is the higher pressures we run to avoid edge wear. Firstly we do not have to worry about the tyre exploding as long as the pressure is less than 51psi as quoted on the manufactures website (check yours).

At fronts of 40psi cornering speeds much slower and ABS came on more often. This is not due to the less contact patch the tyre has because contact patch is not equal to grip (Scientific fact! – like a tone of bricks weighs the same as a tone of feathers). The theoretical reason for this from what I could find out is that the tyre is so stiff at high pressures it is unable to grip the textures in the road and only ever felt comfortable on newly laid tarmac. Stiff, echo or cheap tyres are plain dangerous compared to softer performance tyres on these high pressures.
Not to mention the uncomfortable ride. Edge wear was reduced as the tyre wear began about an inch more in and very efficient on fuel though.

At fronts of 38psi grip levels have improved and you can still feel all the textures on the road but without it hurting you. The side walls are still nice and stiff for spirited cornering. Tyre wear began half an inch in from the edge and it seems you do not have to run a super soft compound tyre made of cheese either as I recommend Falken FK452, but I do not recommend anything harder, budget or echo. You may get edge wear with super soft tyre's but the Falkens FK452 seem best set up after allot of research. It also worth noting that my rear tyres had been set to 34psi that although gave great feedback, but by lowering to 32psi. ABS was reduced and comfit improved.

At front of 32-35psi grip levels are fantastic and even with harder cheap tyres it is not too dangerous. Unfortunately edge wear is there and the side walls are too soft and lumpy for spirited cornering as you get no feedback from the road. You will be faster but it is less fun. You can visibly see the side walls sag too much on the front.

Summary:

What I did learn is that grip is not equal to contact patch. Then why are Formulary 1 tyres wide? Because they last much longer and do not over heat, in the same way as they are high profile to absorbed the bumps in the road because the suspension set up takes on the responsibility of being ultra stiff for better faster lap times.

Grip is equal to the "hugability" of the tyre to the roads textures and bumps. This why high performance soft tyres remained reasonably grippy at very higher pressures when the cheap tyres fell away dangerously. For the Auris 2.0 D4-D I recommend a pressure of 38psi on the front and 32psi on the back but with decent semi soft tyres like Falken FK452 to reduce wear but if money is not an issue tyres made of cheese (super, super soft) like Goodyear Eagle F1 GSD3 and Dunlop Sport Max are are exceptional.

Further Reading:
Auto Speed - Tyres, Grip and All That...
gamedev.net - The Physics of Racing, Part 10: Grip Angle

25 April 2008

The Italian Burger - A Homemade Recipe

I have been making my home made burgers for some time with some various results some of the nicest being a chicken and pork mince burger but it proved quite a hassle to make. The nicest and actually the most simple burger is the Italian burger.

All you will need is:

1. Lamb mince and Rosemary OR Good quality beef mince with parsley
2. Mozzarella
3. Red or green pesto
4. Chopped Onion
5. Pepper and salt
6. Optional quality buns (not the cheap fluffy chavy ones)

Mix the mince meet up with finely chopped onion (and parsley if using beef) and salt.

Make the burgers shaping them with your hands. You do not need to bind with egg etc...

Put them in the oven at 200c or shallow fry in a pan and add Rosemary on top if using lamb (You do not eat the Rosemary)

Turn the burgers over after about 8 minutes of frying and then gently add pesto to the top of the burgers with a spoon.

Slice the Mozzarella to get as much surface area as possible and add it to the top of burger while frying for 10 minutes or in the oven for 5 mins and then serve the burgers immediately as you see the cheese melt slightly. You may also add Tomatos etc...

03 March 2008

Diesel Torque vs. Petrol Horsepower... what car is faster?

If your thinking of buying a Diesel you will want to know how it performance compares to petrol car with typically less torque but more or the same bhp. I am not an expert on this topic but will try and keep this short and explain what is best without having the complex equation.

The most simple minded way of thinking about torque and horse power are to consider them as two completely different and unrelated values (Forget the equation!). If you have a high torque (Diesel/Drag racers) car then you use the torque to accelerate at low revs and foot to the floor if you want to drive it fast. If you have a high bhp (Petrol/Formula 1) car then typically you must use its horsepower found at higher revs at the red line.

Case for horsepower!

Because torque levels are so low in a petrol car (unless you have silly 3.o+ liter engine) the driver has to increase the amount they rev (rpm) to accelerate fast. When you increase the amount of revs closer to the red line you go faster and the car feels more sporty than a Diesel but you can't help but think your thrashing the engine! Formula One cars have less torque than a high performance Diesel but they achieve 800bhp because the engine revs as high as 16,000 rpm.

Case for high torque!

Turbo diesels often have 3 times the equivalent torque if a petrol car in the same class. For example we shall use the Civic Trpe-R with 202Nm of torque compared to a Toyota Auris T180 with a massive 400Nm of torque. If both cars are casually driving and both put the foot down the Auris would be considerably quicker however if the Civic driver dropped down a gear the Civic would be just as quick (maybe quicker because the car is lighter).

Having a high torque will make your car feel more powerful than a petrol because it is pulling away at only 2,200-3,500 revs and as a result uses less fuel (all good for the wallet). Often the problem with Diesel cars is that the torque runs out too quickly and you have to learn to keep the torque inside the power band and this means lots of quick gear changes. Diesel cars especially can be chipped to increase both turbo and fuel to a much greater degree than petrol cars.

Diesel is my choice of car and it is not just a fuel saving (Expect around 45mpg) but insurance groups are 3 or 4 times lower even for sporty models and the tax band rarely exceeds band D.


Ok the Maths Equation

This look complicated where P is power, τ is torque, and ω is rotations per minute. But it does not need to be and the equation can be simplified to:

Horsepower = (Torque x rpm) / 5252

You can more information here:
http://community.channel4.com/eve/forums/a/tpc/f/1766037851/m/5920090204
http://www.pumaracing.co.uk/POWER1.htm

30 May 2007

Creative ZEN Vision:M vs Apple Ipod Video

Apple Ipod Video Vs Creative Zen Vision
I can not believe the unprecedented success of the Apple Video player when Creative have a far superior product for slightly less. The advantage of the Creative ZEN Vision are:

1) The Zen has a proper battery while the the Apple Ipod Video is slimmer to accommodate only a small battery with a couple of hours playback. [2007 UPDATE: Battery life seems to have improved with the newer apples]
2) All my WMA files work on the Zen!
3) Zen plays most video formats including the excellent Xvid (but sadly no H.264 the Sony PSP can). The Apple only uses MP4!
4) The colour screen of the Zen is capable of displaying far more colours and is much more vibrant and blacks more black.
5) I don't care for the FM radio but there is one.
6) I can plug it into any of my Windows XP PC and transfer files even without software or drivers.
7) Better Sound Quality from a Zen
8) You have to use Itunes to upload to your Apple

Due to a larger stronger amp the sound quality is better in the Zen Vision, however the supplied earphones require the bass boost to be on to prevent it sounding harsh. I recommend replacing them with wide bass heavy Koss Porta Pro (£30) or Koss KSC75 (£12) otherwise you may prefer more balanced Sennheiser PX100 (£30) or my favorite Audio Technica ATH-EM7 (£60). If you must have small earbuds the only ones I would use are Super.fi, Sure e3g or the non budget Audio Technica ATH range, but you are paying a premium for size.

When you have replaced the earphones in the Zen you will find the sound settings are wrong for them even with "EQ off" because the EQ is not level. All amps have some sort of equalization and they are never flat and when you switch off the equalization on the Zen it is way too enhanced with far too much bass and treble extension making the sound congested and distorted at higher volumes. Changing the EQ levels to flat make the sound far too dull and I find the best equalization preset similar to that of audiophile amps such as NAD or Merantz to be the "Acoustic" or "Classical" setting and with no bass enhancement.

If you do choose a Zen consider downloading MediaCoder that converts video in a fraction of the time it takes to convert using the awful video software than comes with the Zen. To take advantage of this read my video compression article to get the best video for as little space as possible.

26 May 2007

How to compress a video for portable movie players including Zen Vision:M (Xvid encoding bit rates explained)

Creative Labs Zen Vision MI got my self the excellent Creative Labs Zen Vision M and I was enjoying uploading my music using the intuitive interface very much. Well... up until I wanted to upload video that is. The supplied software is totally unacceptable. I have jagged corrupt video depending on what PC I used and it was incredibly slow. Also the compression options and codec's limited.

After testing lots of free software MediaCoder was by far the most comprehensive and fastest out there, and I was able to compress TV shows right down to a fine art so I want to share my settings with you...

Xvid is the best codec format to chose. Choose a bitrate of no more than 400kbs for you best visually impressive movies however 350kbs is perfect for less visually demanding shows. This is the maximum bit rate settings and not the average. Keep to the .AVI Container.

If you have a good processor and much more geek time you can use Two-Pass encoding over single bitrate based, however you may need to run Two-Pass encoding overnight because it is slow and your PC may become inoperable with large files until the process is over. Two-Pass will squeeze more video quality for less file size by making bitrates variable across each frame but the compression is very slow. To my eyes 350kbs 2-pass movie looks more like a 400kbs or more (depending on the visual nature of the movie and original quality).

Audio settings made a huge difference to the file size. Choose LAME MP3 VBR and to be honest do you really need stereo sound that will split the bit rate into 2? If not simple choose Mono and a sound bitrate around 80kbs and it still sounds very good to me who enjoys an audiophile sound system at home. For the more demanding stereo you really need 92kbs to 128kbs.

The Vision:M screen is 320x240 so set the output to that. Lastly do not forget to match the original frame rate to the output and Crop to fit wide screen movies to 4:3 aspect ratio of your Vision:M (This is not suitable for Vision:W becuase it is widescreen and so may need to do the opposite).

The file size from any of the above settings ends up being being under 180MB per hour.

My MediaCoder settings for Creative Zen Vision: M
MediaCoder (settings above) is an excellent piece of free software (interface could be better). Do consider sending them a small donation.

Compressing Cartoons into Xvid
For Cartoons I strongly recommend 2-Pass as artifacts are blatantly visible at a bitrate of 350 without it. Artifacts like dots are visible becuase cartoons like Simpson's and Futurama have lots of flat block colors and not like real life video, ideally requiring a totally different mode of compression. Even consider raising the bit rate to 400kbs for cartoons however I am happy with 350kbs as long as it is 2-Pass.

There is also a Cartoon Mode for Xvid! To do this goto Options > Drop down "Xvid" > Select "True" on "Optimize for cartoons". In practice however I can not spot the difference apart from possibly smoother motion? The file size increases by about 15MB per 20 minute episode..

What about Music and Audio?
With 30GB hard drive I do not bother being strict. The nature of music demands a bit rate between 160kbs to 192kbps MP3 using the latest LAME VBR codec. This is CD quality to the human ear. MP3 will also use much less battery than WMA (strange but true!). Comedy and audio casts can go as low as 80kbps mono.