Two Guys Rally

Gas Saving Tip #4 [ July 24th, 2008 ] By:Charles Smith

While this is not so much a gas saving tip as it is a money saving tip, I think it addresses a common misconception about gasoline.

Stick to Low Octane Gas. If you don’t have a requirement for above 89, buy the lowest octane gas that will keep your car working. Octane has nothing to do with engine performance by itself. That is 93 octane will not make a car that only needs 87 octane run better.

Higher octane gas can put up with higher temperatures before it ignites, so high performance engines take advantage of this fact. They compress and heat up the gas and air more than a normal engine would in various ways. They could turbo/supercharge, increase compression in the cylinders, etc… All of those would require higher octane gas. If they used lower octane gas, the engine may start to knock. That means the gas is igniting before the spark and you can damage many parts of your engine when this happens.

So unless your engine requires it to prevent knocking (detonation), stick to the lower octanes.

Rollcage As Performance Mod [ July 23rd, 2008 ] By:Charles Smith

Many people tend to think that roll cages only provide safety and some extra weight, but they’re forgetting something: what they can add is stiffness.

Because roll cages were mandated as required safety devices in oh so many racing leagues, clever engineers figured out that they could use them to make their cars better. I don’t know who did it first, but they decided to connect all the suspension points together with a tubular space frame and call it a roll cage. Suddenly the mass of tubes becomes a way to stiffen up the car’s chassis.

You might not realize just how much a normal street car’s chassis flexes under any sort of acceleration (0-60, cornering, braking, etc…). This flexing acts much like the suspension, in fact most go-karts depend on frame flexing as the suspension (also the tires). However this flexing in a normal car changes the geometry of the suspension which can make a car less predictable and much harder to tweak (suspension wise).

Connecting the points where the suspension meets the frame with tubing (aka roll cage) can significantly increase the stiffness of a stamped sheet metal frame. This will keep the suspension geometry closer to normal under hard accelerations and allow you to more consistently judge how your suspension is affecting your car. However in most cars, connecting the suspension points (strut towers) will require to send tubes through the firewall of the car. Do you notice the tubes going through the firewall on the Subaru US Rally Team car? You should not be intimidated by the firewall, cut through it and reseal it around the tubes!

So, if you’re going to add a roll cage, don’t just add it to be within your competition rules. Take advantage of the rules and stiffen up your car so you can better adjust your suspension. Also, it results in less deflection in the chassis, which Mark tells me means you’ll end up with “smaller cyclic loading” on it. That means you’ll have more use of the chassis before it fails from normal race stresses. HOORAY ROLLCAGE!!!

Keeping Racecars Cool [ July 22nd, 2008 ] By:Charles Smith

While racecars are usually most definitely awesome, today’s weather reminded me they are pretty effing hot inside them. In the quest to save weight (translation: saving time on your laps/stages) common things are kept off the car. Air conditioning is gone, underbody/frame insulation is gone and the lexan windows usually dont roll down. Combine that with the fact that a racecar’s engine runs quite a bit hotter and cars with antilag systems (ALS) have exhaust temperatures above 1000 ºC the car’s interior will be hotter when running. However there are a few tricks to keeping the cabin temperatures survivable:

Air Vents

Racecars have a love hate relationship with air. At really high speeds it slows them down and sometimes even makes them crash, but it also cools their engines. In a similar fashion, it can help cool the cabin and driver(s). Keeping your drivers alive means getting them nice cool air to breath. Good helmets allow the driver to breath and it lets sweat do its work at cooling the driver(s) down. NASCAR likes to use forced air helmets that push air through the helmet, while Rally tends to use open face helmets (very breathable and you can yell at your driver in them).

In order to let a helmet do its job air needs to be getting to the driver(s) from outside. Vents to the cabin are nice for this. Rally cars often have a vent on the top center of the car to let air in through a diffuser so the drivers can breath and cool off. Air also has to exit the cabin, but if your windows are closed how can it do that? Closable vents in the back windows help with getting air out of the car, however in a Rally application I would suggest a filter on them (dust likes to come into the car otherwise). Andrew Comrie-Picard’s Mitsubishi is a shining example of common air ducting.

Window Tint

Sunlight heats up the cabin majorly. Ever been burned by a seatbelt buckle that was left in sunlight on a hot day? I know I have. Tinting a racecar’s windows with reflective tint can reduce any sunlight that is causing the cabin to get real hot. While black tint works to combat cabin temperatures, mirror tint works better (more reflection, less absorption) as it will not radiate as much heat through the glass into the cabin.

Roof Paint

Another way to keep the cabin temperatures from skyrocketing due to sunlight is to paint the roof of the car. The roof of the car is often not seen by spectators, so diverting from your colorscheme is not as big a deal. Painting the roof white will keep it from absorbing as much heat from the sun and further lowering the temperatures in the cabin.

Interior Paint

The interior is exposed to light too! Roll cages and the inside of the car frame make up a large surface that can absorb even more heat. Painting them white keeps them from absorbing as much heat. Plus a consistent interior color makes the car look neater and better organized. Also white shows everything wrong(great trait in a racecar) like: all sorts of leaks including exhaust, cracks and where you dropped your notes pen.

Insulate Exhaust Pipes

Exhaust pipes in racecars get extremely hot. They get way hotter than the exhaust on a street car so there is a lot more heat that comes off of them and into the cabin. Wrapping the exhaust in heat insulation might add a couple pounds, but it might give you a better performing engine. Higher exhaust gas temperatures means higher exhaust gas velocity, and if you’re running a turbo this means a faster spooling turbo. Not only will you get a possible gain in your engine, the cabin temps will drop. A normal exhaust will radiate heat into the metal on the underside of the cabin (a good amount of it too) which will transfer into the cabin. 1000ºC exhaust gas will conduct massive amounts of heat through a thin piece of metal(exhaust piping).

Regardless of what you’re racing doing everything you can to combat high cabin temperature will make your racedays more enjoyable and more consistent. Heat fatigues people, and tired drivers are dangerous drivers. That one, came straight out of a DMV Manual.

Rear Wheel Steering: Why Not? [ July 21st, 2008 ] By:Mark Ozimek

I was pushing a cart around at work today at a rather rapid rate, and no, I was not racing a co-worker, I swear! It was one of those carts that had fixed front wheels and rear wheels that were free to pivot. Being the forever analytical engineer I am, I noticed how much the cart liked to turn, and how much the front wheels slid. I didn’t give it much thought until I hopped into my car to go home. Then: “Why don’t we see many, if any cars with rear wheel steering?”.

Obviously, it must have some sort of major handing characteristic that is undesirable, or we would have seen it in racing a long time ago. It is kind of hard to predict what such a car would handle like without testing it out. I would say drive a normal car in reverse, but that’s a little different because the suspension is designed in such a way to make the wheels center when going forward. In reverse, the car wants to turn more into the direction it’s turning.

From an overall physics standpoint, it’s rather curious to think about. Normal cars turn by pulling the front end in towards the center of the turn, the rear wheels just follow along. With a car that has rear wheel steering, the back end is let loose, and follows the front tires that stay on the same line. This should sound vaguely familiar, as that is what happens when the car oversteers. To be precise, it’s very very similar to what is happening when the car oversteers just enough that the turn can be held by keeping the front wheel’s axis in line with the center of the turn.

Knowing that, it’s pretty easy to understand why we don’t see it in cars; The setup is highly unstable. However, this could be a very good thing for certain types of racing, if the driver is up to dealing with the demands. Rally is one where it’s benefits could be seen greatly. Going around hairpin turns would be a breeze, just keep the front wheels on the line you want to take, and pivot the rear out, just like what happens through careful use of throttle, steering and handbrake use on normal cars. If the front tires start sliding, simply turn a little harder to pivot the car in some more. If the back slides out, turn less. Very intuitive, as opposed to countersteering and managing throttle input to keep the back from spinning around, or juggling weight transfer through braking to manage understeer.

Someday I’ll have to try racing a rear wheel steering car to confirm my suspicions. Until then, just a thought to keep in the back of your mind, instead of taking for granted that cars should always use the front wheels for steering. Also, think about how easy parallel parking would be!

I Want More From US Rally Coverage [ July 18th, 2008 ] By:Charles Smith

I was perusing Rally America’s site and one thing caught my eye: air dates for rally coverage on ESPN2. Im excited to see that American rally is making it on to TB, but I’m dissapointed at the same time. STPR, which took place in early June, will not air until July 27th along with Oregon Trail(April 20th) and the Olympus Rally(May 19th). Three rallies, which happened months ago, only get one hour of coverage from 5pm - 6pm (so 42 minutes) total. I think it is a shame we only get 10-15 minutes of coverage per event on TV months after they happened.

Thank god for the X-Games Rally, which will air on ABC for much more than 15 minutes of Rally highlights. How do you guys think the coverage should be handled? During the event have daily highlights and recaps? A whole rally channel to cover every aspect of Rally 24/7? Highlights only? I’m eager to hear what you think.

Back To Normal at NEFR [ July 17th, 2008 ] By:Charles Smith

The New England Forest Rally was this past weekend, and unlike STPR’s results, NEFR was back to what you might expect: Coming in first was Niall McShea and co-driver Marshall Clarke, followed by Andrew Pinker/Robbie Durant. Rounding off the podium was Travis Pastrana/Derek Ringer.

This is good news for American Rally racers. Niall McShea has had 32 WRC starts, placed 9th in Rally Australia in 2004 and was crowned 2004’s PWRC winner. While you may not think that it is good news that a PWRC winner is stomping Americans and Canadians in Maine, you have to look at the pace that was kept. Travis Pastrana was only 2:43 behind McShea and only 1:18.9 separated Pinker from McShea.

As this beautiful sport grows in America, the gap between Europe and America shrinks in terms of Rally talent (see also Colin McRae not finishing 1st in the X-Games to Pastrana).

Did I Ever Mention I Love YouTube [ July 15th, 2008 ] By:Charles Smith

I really do love YouTube. Why? Because of things like this:

I’ve probably watched this a few times while trying to keep up with Phil Mill’s notes. It is amazing how much road info Petter Solberg is getting from his co-driver. That is only part 1. Part 2 can be found here.

If you also really like YouTube, TwoGuysRally has a channel. Subscribe to it.

The Volvo Chronicles: Worn Suspension Parts [ July 14th, 2008 ] By:Mark Ozimek

Since there are more things going on with my S70 T5 than just some missing power, I decided it would be wise to just label everything that relates to my car the same way. After all, it’s a ten year old car with 150,000 miles on it. Things are gonna break, and I’m gonna have to replace stuff and write about it.

So what happened this time? Well, I had to get my car inspected, in order to remain road-legal. So I drop my car off at a local mechanic in the morning. After a few hours, I get a call from the mechanic, informing me that my inner tie-rods had too much play in them, and he couldn’t pass the car as it was. In case you are unsure, the tie-rods are the beams that connect the steering rack to the wheels so that you can turn the car. They have to allow movement in a few axes to account for turning and suspension travel. The parts the rub together are usually the parts that break after a while. If you break the rod itself, I’ll be very impressed.

Suspicious, because I never noticed excessive slop in the front end, I went down to check it out, and sure enough, there was a lot of play. I don’t know exactly how much is passable, but the wheels were pivoting about the vertical axis enough to move the front and rear parts of the tire tread around 3/8″ to 1/2″ on the driver’s side, a little less on passenger.

I give him the go ahead to replace the inner tie rods, and asked him to change out the outer tie-rods too, since it’s only 5 minutes of extra work once you’re in there. If the inners are worn out, the outers are likely to be pretty bad too. Unfortunately, since the car was already in the shop, and I was on a tight time schedule, I didn’t do the work myself. It’s not a very hard job, just somewhat time consuming, and you should get an alignment afterwards.

Curious to see how much of an effect the worn parts had, I took the car out for a spirited drive afterwards. The difference was almost surprising, especially over rough surfaces. I had never thought about it before, but when turning on a road that has bumps, or is generally rough, my S70 made some clunking noises, and tended to skip sideways every now and then.

Now with the new tie-rods, the car was much more settled and predictable, and a few of the clunking noises I had grown accustomed to and thought nothing of had disappeared. Of course, it wasn’t all better, since all the other bushings and ball joints are probably pretty old too. Someday I’ll have to take the time to rip apart my suspension and replace all the other worn parts.

Moral of the story? Check the amount of play in the suspension part joints, even something that was relatively unnoticeable could actually be a pretty serious issue!

Calm The Eff Down [ July 11th, 2008 ] By:Charles Smith

Slowing yourself down and not ‘pushing too hard’ will, oddly enough, make you faster. The principle behind it works in many other sports, especially those considered “Finesse Sports”. If you calm down and let your tools do the work for you (car vs golf clubs vs tennis racquets) you’ll find yourself performing consistently better.

There was a saying I heard at Team O’Neil Rally School, and it was: “Slow in, Out fast”. Regardless of the obvious: if you cannot make the corner, you cannot win the race. I think they were trying to tell us to calm down and not be so concerned with if it felt fast. If something feels fast, it doesn’t make it so, you need a clock to tell you how fast it really is. I think this is why simulators are so useful, while it may not be the real thing, you can work on your mental game in them.

So I would just like to instill these words on to you: “Calm The Eff Down“.