Two Guys Rally

Anti-Roll Bars [ August 5th, 2008 ] By:Charles Smith

Without an anti-roll bar, when a car turns left the inertia of the car would cause the right side suspension to compress and the left side suspension to extend. This is primarily due to the center of gravity (CG) being above the axis about which the suspension rotates. A higher CG means a larger tendency to roll, as many of you have probably experienced with driving different sized cars. A roll bar keeps the suspensions at similar compressions/extensions and that makes the car body roll less in corners. It is a pretty simple concept.

However with any simple concept there are many implementations of it in the real world. Sway bars, another name for the anti-roll bar, connect the left wheel to the right wheel (front with front and rear with rear). Most of them tend to be torsional springs (springs that are designed to resist twisting rather than compression) but there is at least one electronic method.

The trick to the adjusting the bar is to allow for the “correct” amount of roll to keep the tires on ground. If you go too stiff and corner real hard, you will end up lifting a wheel off of the ground (inside front or rear, depending on if you’re accelerating or braking). If you go too soft (ie none) the car will have grip, but the car’s response will feel sluggish. In Rally it comes down to a combination of overall suspension stiffness, driver preference and style with a mixture of stage terrain requirements. While there is some science behind suspensions, a lot of it is just finding a setup that inspires confidence in it’s handling.

A final note: I have noticed many individuals refer to a strut tower brace as a sway bar. That is just plain wrong, hopefully this video can show you how a strut tower brace would not be a sway bar.

I Hope You Watched The X-Games [ August 4th, 2008 ] By:Charles Smith

The X-Games this year was AMAZING. This is the third year where Rally Racing was present as an event in the X-Games. In pure X-Games fashion the crossover jump was the biggest it has ever been. It was pretty spectacular to watch. Lots of drama and lots of up and comers including a father son team that did better than expected.

Unfortunately the only non-Subaru (Mitsubishi) racing DNFd over the jump. It was driven by Andrew Comrie-Picard, who is trailing Travis Pastrana by 1 point in the Rally America series. ACP ended up coming short on the jump (just a few mph) and the impact on the rear wheels caused him to flip end over end. What makes this more heartbreaking is it was his first race (semi-finals) of the week and he had it won if he made the jump. Why would he have it won? Dave Mirra hit the wall pretty hard and knocked his steering out of alignment right before that (and he thought he DNFd). Luckily for Dave, he was able to finish albeit painfully slow involving many excursions into reverse. There are videos of it popping up all over YouTube: here and here for example. Better luck next year ACP!

It all ended with a battle between last year’s gold medalist and the original X-Games gold medalist: Tanner Foust and Travis Pastrana. Travis was racing with a new co-driver (not too big of a deal on a Super Special) as his current co-driver fractured a vertebrae in the Freestyle Motocross the previous night. These guys are super competitive in everything they do. Anyway, Travis was able to steal the gold from Tanner in their heads up. What an exciting X-Games.

The podium was filled with 4 drivers. Travis Pastrana, Tanner Foust and a tie for bronze between Dave Mirra and Ken Block. I sure hope you caught it on ABC.

The Volvo Chronicles: CBV Diaphragm [ August 2nd, 2008 ] By:Mark Ozimek

Last time I posted about my S70’s engine, I had just replaced some vacuum lines. Although it helped, there’s still something strange going on. I had ordered a new Compressor Bypass Valve (CBV) diaphragm to replace the worn out one that is allowing air to escape from the compressor outlet back to the inlet. Unfortunately it was out of stock everywhere I looked, so I had placed an order and waited for the part to arrive.

Now, a few weeks later, I get home from work to find a small package at the door. “What could it be!?”, I wonder. Opening up the bag reveals the impossibly rare diaphragm:

(Click for larger view)

What this diaphragm does is open and close to allow air out of the compressor outlet back into the inlet to prevent compressor surge when there is a sudden decrease in airflow through the engine at higher loads. The actuation method is pretty simple. There is a spring that pushes the valve assembly closed under most conditions. The pressure from the compressor pushes against this spring. There is a air hose that runs to the intake manifold that allows for a change in pressure behind the diaphragm. When near or at WOT, the pressure in the intake manifold is close to that of the compressor outlet, meaning the spring holds the valve shut. When the throttle is suddenly closed so that there is a lot more pressure in the compressor outlet than in the intake manifold, the spring can no longer hold the seal closed, allowing air to flow past it.

Over time, the heat, oil, cyclic action, vibration, dirt, etc., break down the diaphragm, it stiffens up, develops holes and tears, which generally decreases its performance. When there are holes in it, air can always escape through the CBV, significantly decreasing turbo performance and efficiency.

So I plan to change the diaphragm in my car soon. It isn’t a terribly complex job, there is just very little room to work, as it is wedged between the turbo housing and engine block, with a bunch of stuff in the way from both the top and bottom.

It’ll be a fun project to work on, and I’ll be sure to make a post when the old one gets replaced!

A Look Inside A Subaru Parts Truck [ July 31st, 2008 ] By:Charles Smith

Travis Pastrana’s car is supported by oh so many spares of almost everything on the car. Rarely would you get to see inside the support vehicles unless you were at a rally. I happened to stumble across a video of just that on YouTube. You may want to fast forward a bit past the intro.

Here is a link to the video for you RSS folks.

Keeping Drivers Cool [ July 30th, 2008 ] By:Charles Smith

The whole point of keeping a racecar cool is so you can keep the driver(s) cool. There are lots of neat ways that race teams around the globe do it. Here are a few of them:

Cut Back On Layers

This may sound obvious but most racing suits have three or more layers of material to them. Keeping the layers down to a minimum (safety still matters) will allow the air you bring into the car to do its job and cool the driver down. The Subaru World Rally Team cuts that down to 2 layers of outerwear for the really hot rallies. The neoprene underwear still restricts breathability but keeps the drivers safe from fire.

One of the neat things about Rally Racing is that short sleeved suits are allowed in the extremely hot rallies. Many famous world champs have rocked the short sleeves or rolled up sleeves during desert rallies. See Colin McRae and Richard Burns for prime examples.

Drink Lots of Water

Being properly hydrated keeps drivers cool for a few reasons. First of all they can sweat, and if the car is breathing right that sweat can evaporate and will take a large amount of heat away from the driver(s). You will also lose a large amount of water through sweating, especially in the heat of a cockpit.

Your body is mostly water, so any heat your body generates related to general metabolism gets dumped into that mostly water body of yours. Less water means higher temps for the same metabolism (when controlling for the effect of sweat).

Your blood volume is also 80-90% water and so losing water means your blood volume will go down. This makes your heart work harder (oh look more energy release) and you feel hotter for the same temperature. Petter Solberg has said that he and Phil Mills will drink 10 liters of hydration fluid (mostly water and some electrolytes) in a day. That works out to over 1 gallon per person on that day not including the water that is in the food they eat. So drink up before and on race days.

Put Things In Freezers

Put everything you wear in a freezer (except maybe the neoprene) as it will make it a little nicer for that much longer. Your clothes will absorb that much more heat before letting you heat up.

Throw in some towels sprayed with water. Freeze those puppies so when at service, or pre and post race, you can wrap one around your neck and keep cool.

Mix Alcohol and Water

I am not saying drink alcohol, but add water and rubbing alcohol together and keep that chilled in a spray bottle. When you can, spray some on your skin and lots of heat will be pulled away with the alcohol and water (so will the oils in your skin). This works so well that some racecars will put this mix in intercooler spray reservoirs. It really will make that much of a difference.

Drinking alcohol will actually hurt your ability to cool off as it is a diuretic. So that is just one more reason not to drink when racing (besides the many obvious ones).

Neat Technologies Help

A loyal reader Dustin Tarditi reminded me about things like UnderArmor (loved it for lacrosse) and their high tech cousins deemed Cool Suits. Under armor is great for wicking away sweat (and with that heat) from the body and allowing air to do its job.

Cool Suits are even cooler as they will run coolant (water or what have you) from a cooler that is in the racecar (or in the pits) through tubes and across your body. The tubes are zig zagged across your chest and they pull heat away from your body into the coolant (which goes into the cooler).

Newer styles of Cool Suits are focusing on the wrists and palms. Why? Because “in order to cool the body you must cool the blood”, and the blood is a lot closer to the skin around the hands. This is the same reason you treat heat stroke/exhaustion by cooling the hands and feet rather than the whole body (the latter is dangerous as it may make it harder for the body to cool itself as it will bring the blood into the core due to shock). The trick to the new technologies is making them lightweight and not interfere with the driver(s) control of the car.

Gas Saving Tip #5 [ July 30th, 2008 ] By:Charles Smith

Gas stations need to be refilled just like your car. The trucks that fill the gas stations have pretty busy schedules, so they pump in the gasoline as fast as they can. That is all fine and dandy until you are refilling your car soon after they refill the gas station. The refilling process stirs up all the particulate matter that settles out of the gasoline in the storage tanks. The particulate matter then gets pulled up into the gas pumps and into your car.

So don’t fill up at a gas station that has been refilled recently. While a small amount, you’ll be spending parts of a penny on things that are not gasoline and paying for it as gasoline. Plus you will be making your fuel filter work just that much harder and possibly restrict its flow over time. So if you see the gas truck in the gas station, keep away from there for a few hours. It might save you that much more (if your time is worth it). 

Rally in X-Games! [ July 28th, 2008 ] By:Mark Ozimek

As pointed out here in passing before, we’re excited for the 2008 X-Games and the rally event that it is going to have. Just a reminder to everyone, the X-games is coming up very soon, starting on July 31st, this Thursday, running to Sunday, August 3rd.

A large part of the philosophy behind TwoGuysRally is to attempt to create a larger Rally awareness and fanbase in the USA. Media coverage is sorely lacking, and the general popularity of the sport is just pathetic compared to many other countries in the world, especially when you look at European countries. How can we fix this? Well, now that the opportunity is presented to us, go watch the rally coverage along with all of your friends who have even the slightest interest in motorsport! The more people you recruit into the crazy sport where we toss cars through trees at high velocity in the snow, the better! I mean seriously, who doesn’t enjoy the insanity of the co-driver’s pace notes, and his reaction to unforeseen events, forbid they actually happen.

Unfortunately, I’m having difficulty finding exactly when the Rally is going to be shown. Anything that covers X-Games should show it, or some of it. I know that it will be airing on ABC on Sunday sometime, in the middle of Skateboarding. So make plans to sit near a TV this Sunday to watch it, I know Charles and I will be!

Calm The Eff Down: An Addition [ July 26th, 2008 ] By:Mark Ozimek

Charles made a mention about keeping calm to improve your driving a few days back. There are two things that brought this article to my attention recently.

First would be the F1 race in Germany last weekend. For those who follow the F1 races, notice how much Filipe Massa’s driving improved when he stopped pushing the car too hard. It is possible, and perhaps too easy to create strange and unsettling handling issues that unnerve you when pushing too hard. This will just make you nervous and lose confidence in the car. Stay calm, don’t let the pressure affect your driving negatively. I realize this is easier said than done, and requires some practice, which brings me to my second point.

The other relates to driving on normal roads with everyone else. A major problem with cars is that we treat them as our own personal space, when we have to share that space with others on a public road. Invariably, we get frustrated and annoyed with other drivers who don’t do what we want them to. I saw a few good examples of this on the drive home from work today. There was a large backup caused by an accident, two lanes closed on a three lane highway. When it came time to merge to the one lane, everyone went from just driving normally to honking, swearing, cutting each other off, and generally carrying on. Just calm down, use a blinker, and try to set a good example for other drivers on how to behave. This prevents a lot of stress, as well as potential accidents. Both are good things to avoid! By mastering your patience with the insanity of the general population, you will take a large step forward to mastering your calmness on the race course.

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!!!