Two Guys Rally

Sequential Transmission and Rally America: An Update [ March 31st, 2009 ] By:Charles Smith

In June of 2008 I wrote an article lamenting about Rally America’s rules on sequential transmissions. Turns out they’ve caved…a bit. I was reading the rules and I stumbled over this on page 89 section 6c:

Gear Change: The use of an unassisted manual sequential gear change mechanism is allowed.

Neat! You can use a sequential given that you have direct access to the mechanical selector. That is only one step away from an electro-whathaveyou sequential with paddle controls. Although you cannot control many parts electronically (yet), as seen on page 89 section 6b:

Electronic Controls: No type or form of electronic control is permitted for the following components:
i. Suspension, steering, braking, gear change/clutch, front and rear differentials.
ii. Simple engine cut operating during a mechanically activated gear change is permitted.

So you cannot control the clutch/transmission electronically yet. But you can flat shift, which means you keep your foot planted on the gas pedal during shifts and electronically cut the engine’s power. Either way, there is hope for Rally America to become the premiere rally league in the future. Not for a while though.

Combustion Engine Theory: Intro [ March 29th, 2009 ] By:Mark Ozimek

I was thinking the other day (rare, I know) it’s about time that I started up another interesting series. How about something that is at the heart and soul of almost every motorsport: The engine!

This is just the introduction to engines, I’ll cover the common terminology and give everyone a good starting point for understanding the finer design choices that I will cover later on.

Most automotive racing is powered by internal combustion engines. There are some variations within there to make things interesting. There are usually either two stroke or four stroke engines. I’m gonna focus on the latter, because two stroke engines are basically non-existent in rally. In four stroke engines, there are… wait for it… four strokes!

• Intake: The piston is moving downward, away from Top Dead Center (TDC) with the intake valve(s) open and the exhaust valve(s) closed. This draws in fresh air/fuel mixture to burn later.
• Compression: Intake valve closes, usually just after Bottom Dead Center (BDC), and the piston moves up to compress the air/fuel mix. Just before TDC (usually 10º-40º of crankshaft rotation), the combustion begins, either by igniting the fuel with a spark (gasoline) or injecting the fuel into the compressed air (diesel)
• Expansion: This is the stroke where the power comes from, the burning air/fuel mix generates a lot of heat and pressure that pushes the piston down, generating torque.
• Exhaust: Just before BDC, the exhaust valve opens up, and the piston moves back up to push all of the burnt gasses out of the engine. Once it reaches TDC, things start over again with the intake stroke.

The next choice is the type of fuel. Diesel engines run by compressing air a lot to generate very high temperatures, then inject the fuel, which combusts to generate pressure and heat that drives the engine. Spark ignition engines run a bunch of different fuels, usually gasoline, but can also include mixes of gasoline, ethanol, methanol, propane, compressed natural gas, and a few others. The air fuel mixture is ignited with a spark instead of relying on the sheer amount of heat in the diesel cycle.

There are also variations of the typical reciprocating piston engine, the most common being a rotary, or Wankel engine. The piston is replaced by a rotor with three faces housed inside of an oval-like housing that is technically known as an epitrochoid. Rotary engines have a very high power/displacement ratio because there are three power strokes for every revolution of the rotor, compared to the one power stroke every two revolutions of the crankshaft of a normal four stroke piston engine. However, sealing and lubricating the piston is a significant issue that hampers the reliability of this design

So now that this is out of the way, it’s time to get into the common terms used when describing or talking about engines. Let’s start at the macro level, things that everyone should be familiar with and move our way in.

Displacement: The amount of volume that all of the pistons displace in one stoke. This is dependent upon the number of cylinders, the bore and stroke.

Bore: The diameter of the cylinder when viewed from the top. The piston diameter is a small amount less than this, with rings to provide a good seal

Stroke: The distance the piston moves from TDC to BDC. This is dependent upon the crankshaft dimensions.

Compression Ratio: The ratio between the displaced volume (Vd) and the volume in the top of the cylinder (Vc) when the piston is at TDC. To calculate, CR = (Vd + Vc) / Vc.

Air/Fuel Ratio: Also known as AFR, or it’s reciprocal, FAR. Gasoline likes to burn within a specific range of ratios between the mass of air present and the mass of fuel present, typically between 8:1 to 20:1. the combustion can be considered the most “complete” when the AFR is stoichiometric (the wiki article does a better job explaining the chemistry than I ever could), 14.7:1 for pure gasoline, or ~14.2:1 for the 10% ethanol blend that almost all pump gas is now. This means that for every 14.7 kilograms of air that flows through the engine, the engine will try to supply 1 kg of gasoline. Ratios that are lower than stoich are called “rich”, and higher is “lean”. Given a constant set of parameters and optimized ignition advance, AFRs around 12.5-13 for gasoline give the most torque, because the fuel burns the fastest then.

Ignition Advance: Measured in the number of crankshaft degrees before the piston reaches TDC. Typically spark will be tuned to create maximum cylinder pressure around 14º after TDC. More advance is needed when the engine spins faster, because the burn speed of gasoline does not increase with the engine speed. However, the burn speed does increase with air density, and with AFR, with a maximum burn speed for gasoline being around 12.5-13. As such, timing is typically less advanced with more open throttle or higher boost pressure, but more advanced at higher engine speeds. Many design factors play a role in optimal ignition timing.

Volumetric Efficiency: This is essentially a measure of the amount of air that goes into a cylinder compared to how much a piston displaces. Since air is compressible, meaning the density changes with pressure, it makes more sense to think of it in terms of mass. A volumetric efficiency of 100% would imply that the mass of air that is in a piston is the same as the mass of whatever the displacement would weigh in the surrounding air. So taking the 100% efficiency example further, if it was a 4 cylinder 2.0L engine running at 100% efficiency at STP, the mass of air inside one cylinder would be equal to the density of air (1.184 kg/m³) multiplied by the volume (0.5L), the result is 0.592 grams of air. Doesn’t sound like a lot, but air is pretty light, and when you’re turning the engine at 6000 rpm, the engine is moving about 7 kg/min of air.

Mean Piston Speed: The average speed of the piston as it moves through a cycle. This is dependent upon the RPM (referred to as N in calculations) that the engine is running at and the stroke. To calculate, Sp = 2 * N * Stroke. Due to material strength and fatigue limitations, it is uncommon to see the mean piston speed exceed 25m/s or so, except in extremely high performance racing engines, like F1.

Brake Mean Effective Pressure: Commonly BMEP (or MEP when not measured at peak torque or power), this a way to measure how effective an engine is at making power in relation to it’s displacement and rpm. As a general rule of thumb, the more power you make per amount of displacement and the less rotational speed at that power level, the higher the BMEP is. Alternately, for those of you who know how torque, power and rpm relate to each other, the peak BMEP of the engine is at the peak torque of the engine. To calculate MEP, you need to know either the power and RPM, or torque, displacement, and number of strokes (2 or 4)

Calculating with power and rpm:

MEP = (P * Nr * C) / (Vd * N)

P is power, in HP or kW
Nr is the number of revolutions per power stroke, 1 for 2-stroke, or 2 for 4-stroke
C is a constant, use 396,000 for imperial (hp & ft-lbs) or 10³ for SI (kW & N-m)
Vd is displacement, cubic inches for imperial or liters for SI (61.02 CI per L if you need to convert)
N is the engine speed in RPM

Or with torque:

MEP = (T * C) / (Vd)

T is torque, ft-lbs or N-M
C is a constant, 75.4 for imperial, 6.28 for SI

Well, that’s it for the intro. I’m sure some of you have specific things that you would like me to go into detail on in this series, feel free to ask, and I’ll try my best to cover it!

Brake Dust vs Elbow Grease [ March 18th, 2009 ] By:Mark Ozimek

I was about to put my summer tires back on the Volvo today, but when I pulled the wheels out of the closet, I realized how dirty they are. I used the rain as an excuse to spend some time getting off some of the grime that had built up over the last 11 years and 150,000 miles!

Last fall, when I put the snow tires on, I tried to scrub down the inside of the wheel, and got a bunch of stuff off, but it still looked horrible:

So I made a quick run to a Pepboys down the road and picked up some Meguiar’s Hot Rim cleaning spray. It says to just spray on and rinse off. That’s a blatant lie. I effectively destroyed a sponge scrubbing all the crap off the surface. The spray really did help break down the baked on brake dust, and after rinsing everything off, that wheel now looks like this:

Much better! Not bad for about 10 minutes worth of scrubbing… hahaha. However, not perfect because quite a few of those black spots aren’t dirt, but damage to the surface of the wheel.

So why do this? Well, obviously it look nicer now. More practically, cleaning stuff off the surface prevents oxidation from occuring, and if there is too much dirt and grime, the balance of the wheel can be thrown off, requiring the wheel to be rebalanced to reduce vibration at high speeds.

Rally Cyprus 2009 - YAY! [ March 16th, 2009 ] By:Charles Smith

It is the first time in a long time that a private (not really factory supported) team has podiumed in the WRC’s top class. While we’re stuck with two manufacturers, there are still plenty of teams. One of my favorite teams is Petter Solberg’s self run rally team and he happened to finish 3rd in Rally Cyprus. That really is indicative of the talent Petter Solberg has and it really makes me wonder about Subaru. Maybe there really was something wrong with how Prodrive was making the Subaru WRC car. 

In usual fashion Sebastien Loeb finished first. I don’t know how he keeps that up. Many people would lose focus after winning as much as he has. He keeps getting faster too. It really is quite amazing.

Mikko Hirvonen, Ford’s favorite for the WRC pulled out a 2nd place finish. He’s now only 8 points behind Loeb in the championship standings and with 75% of the season’s points still up for grabs he has plenty of hope to be the World Rally Champion. 

The next WRC race is April 2nd, 2009 and it is Rally Portugal. 

How To Film Your Driving: Interior Shots [ February 25th, 2009 ] By:Charles Smith

Last time I went through a basic run-through of setting up the camera and what not. Now let’s figure out some angles to film with. If you pick the wrong angle your viewers stop watching for a number of reasons: the driving seems too slow, there is nothing interesting in the shot, it makes the viewer sick, they’re tired of the same view everyone else is showing. 

Picking the right angle(s) makes any footage that much better. The viewer will start to pick up on the feel of speed (matters in racing videos) and they will keep their attention focused on your video (rather than your YouTube comments).  

If you are filming racing events you are going to be limited to angles by how versatile they are. You can only put so many cameras on a car (or on a track) and editing in footage from non-race events would confuse people. If you are filming to cut pieces together for a highlight-esque reel you can get a lot more creative with your angles. First lets cover some basic effects of angles:

Basic Effects
The inside and outside of the car require different placements for the same effect, they’re essentially opposites. The higher inside the car you are, the faster it will seem, while being on top of the car will make it seem painstakingly slow. This is because you need a reference to feel speed. Inside the car, if the camera is in your lap you might have clouds or reflections off of the windows as a reference. Clouds are far from the car, making it seem slower. While if the camera (or even your eyes) were higher up and looking down onto the ground close to the car, the perceived speed increases because the speed reference is moving that much more.

Getting the camera too high outside the car results in cutting off the close speed references and again makes the viewer focus on the ones that are far away (horizon). Unless you angle the camera down and can include closer ground. 

I think of it this way: including mostly ground is like an extreme close-up, it increases the energy of the frame. Including mostly sky/non-moving parts is like a wide shot, it reduces the energy of the frame. 

Now lets cover your bread and butter angles:

Behind the Driver(s)
This is one of the more common, especially in Rally, shots to see. It includes both drivers from behind. But height placement and angle from vertical are the most important aspects of this shot. You will hardly ever see a non flat setup of this shot as it will confuse the viewer and make them feel like the car is rolling (even when it is not).

Most of the action comes from the windscreen and whatever is on the other side of it. However, the drivers do provide an acceleration reference with their heads, but that is besides the point. So getting the camera up high enough in the rear of the car is the best idea as you want to see some of the road and at least the horizon. A low shot with no horizon/ground is one of the more boring shots available. Not only can we barely see the human aspect of the racing, but there is hardly any perceivable speed.

Good example of this shot.
A great example incliding Colin McRae’s wild driving.

Cop Car Shot
The POV view, the driver/passenger view, whatever you call it, includes almost none of the interior and at least some of the car for reference. This angle is great because it lets the viewer think they are driving or a passenger. It includes a good amount of ground for speed and some of the car to remind the viewer that this was filmed in a car and not on Superman flying super-low.

This angle is subject to some problems. In bad weather much of the view can be obstructed by rain/mud/snow on the windscreen. The more centered this is in the windshield the less likely that problem is.

Example of this shot. I included too much of the interior and not enough of the outside in this shot, but it’s acceptable. The setup was largely due to the limitations of camera and camera mount. Now that I use a lipstick style camera much better shots can be setup.
Better framing of the same shot in the same car.

Facing the Driver(s)
One shot many people like to see is of the driver’s face. This even applies to full face helmets. Seeing the helmet, or the face connects the viewer with the driver. This shot is even more effective for open face helmets. It really highlights the driver’s concentration and sometimes hilarious facial responses. It can even show off the wheel work (which is plenty in most racing).

When framing people, the two thirds rule really helps. Keep their eyes about 2/3rd up in the frame. If the shot is from the side, give them what’s called lookspace. Lookspace means there is space in the frame in front of their face (to where they’re looking). It may seem obvious to put the back of their head at one end, but I’ve seen some awkward framings. A tip: don’t zoom in too much, get the bottom of the frame to include at least their shoulders or chest.

Looking up from below the people also makes people look better, to an extent. An extreme up shot would be awkward but a camera placement at around neck level or a little below aimed upwards could add some depth and perceived good feelings about the driver(s) to the shot. 

Example with lots of lookspace. It gave me enough room to fit in the pedal shot, but this is more of a “I need to talk to the viewer” shot.
Great example with some tilt. Notice the walls for a speed reference. Because of how close they get to those walls, they can use them as a speed reference. 

Creative Inside Shots
There are so many interesting shots available to you, but most of them will involve either the moving components of the car (wheels, suspension, guages, etc…) or the people and the outside world. This is where your imagination as a producer comes into play. Some ideas for some more shots inside the car are:

• Pedal Shots - get that footwork on camera.
• Out Rear Window - if you’re kicking up a lot of dust, or leading the pack this shot can be really nice.
• Guages-to-Driver - look through the steering wheel at the driver’s face. 
• Helmet Camera - Strap the camera to the driver’s helmet. It shows you exactly where the driver is looking and how their head moves. You start to notice how far through the corners the driver is looking (quite far if they’re good).

So get at it and be creative. Just go out and play! Next time we’ll cover putting the camera outside of the car, but still attached to it.

Rally Norway 2009: Results [ February 18th, 2009 ] By:Charles Smith

Rally Norway took place this past weekend and the results were not far from expected. Loeb (Citroen) took the top of the podium with Mikko Hirvonen (Ford) close behind with Jari-Matti Latvala (Ford) rounding out the podium. 

Petter Solberg had an outstanding performance for his first competition in a Citroen. He placed 6th grabbing 3 points for himself. He was squeaked out of fifth by Daniel Sordo (Citroen). Ford had a strong presence in the top eight(5 out of 8), but then again there are only two manufacturers in the competition so they should be split pretty evenly. 

 

Link for you RSS peeps.

199 Lives on MTV [ February 7th, 2009 ] By:Charles Smith

So I was flipping through the TV to look for something fun to watch for an hour. I ran across 199 Lives: The Travis Pastrana story being aired on MTV. My buddy texted me a few hours later asking if I was watching it on MTV2. So I guess MTV is airing it somewhat regularly. 

If you haven’t seen it yet, check it out. Check out MTV or MTV2 one of these days. It is a documentary worth watching, granted most of it doesn’t have to do with his Rally career.

If you want the DVD buy it on amazon (affiliate link).

Sno*Drift 2009: A Strong Looking Field [ February 5th, 2009 ] By:Charles Smith

So unlike the WRC, most of the teams in Rally America are back for the 2009 season. However there was a significant change of vehicle for one of the top contenders. Tanner Foust drove to second place at this years Sno*Drift in his Hyundai Tiburon. It’s good to see that a non-Subaru/Mitsubishi can be competitive.

Travis Pastrana took first place in his 2009 Subaru, but worried about deer strikes through out the competition (it ended his 2008 Sno*Drift lead). ACP rallied his Mitsubishi Evo into 3rd place, although I think he should’ve done better…he’s Canadian. They get a lot of snow up there, eh (har har har I can make canned jokes about Canada. WOAH! Puns too ).

These results make me happy. They give me hope for Rally’s future. Some diversity is present in the field, unlike the Citroen v Ford WRC. I’m eager to see how this season shapes up. Next up for RA is 100 Acre Wood in Missouri. Woo!

Rally Ireland 2009 [ February 3rd, 2009 ] By:Charles Smith

The WRC’s Rally Ireland opener for the 2009 season took place this weekend. No surprise that the dominating force Citroen took 1st and 2nd place (Loeb and Sordo respectively). But that’s not the interesting part of Rally Ireland. What is more interesting is that there are only 2 manufacturers placing. While it is technically considered 4 manufacturers (for points) it is only Citroen and Ford.

What the hell? I know the global economy is in shambles but only two manufacturers in the premiere Rally racing league? It is good to see that Chris Atkinson tranistioned into a Citroen succesfully (and Solberg will be showing up in a Xsara in Norway), but it is sad to see such homogeneity in what used to be one of the most diverse racing leagues ever.

Maybe the P-WRC will be the league to watch for diversity’s sake. Subaru hinted that it might stick around for some P-WRC action. Redbull just confirmed a Skoda for their 2009 P-WRC team. I imagine you’ll see some Puegeot S2000s kicking around too. 

Or better yet, 2009 could be the year the US Rally viewership approaches that of Europe (we can hope).

Petter Solberg Fans Have Something To Look Forward To [ January 28th, 2009 ] By:Charles Smith

It turns out that Petter will be racing in a Citroen Xsara in the upcoming Rally Norway. That’s some pretty exciting news, since it will be the first non Subaru he has competed in since the year 2000. Almost a decade ago. 

Citroen Xsaras were fast a few years ago, and I wonder if Petter will be able to claw out a decent position in a non-factory supported car. However, for all we know he could be factory supported by Citroen, but I doubt it if he is running a Xsara. 

I’m real excited to see Petter back for another year.