Two Guys Rally

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“.

Rally Racing Online: Season 1 Is Over [ July 10th, 2008 ] By:Charles Smith

My time spent practicing for Rally Japan of the RSL was well spent. With 2 stage wins and consistent top stage finishes I placed 1st in Japan. Which bumped me up to 3rd overall in the championship 1 point ahead of VMethos. This was the final event of the season, and I sneaked by into 3rd.

It was a close race, and VMethos lead the rally up until Stage 5 (Noiker) where I overtook him by .08 seconds overall. I proceeded to beat him on Stage 6 by 12.17 seconds bringing me ahead of him overall by 12.25 seconds. Apparently VMethos and I had prepared well for Japan as we came in 2nd and 1st respectively. We had finally beat Turbo and Wild Swede consistently through a rally.

Wild Swede jokingly claimed that this driver was seen exiting the Citroen Xsara I was driving:

I am happy with a 3rd place overall for my first RBR Season. Hopefully I can be more competitive in the future and pose a threat for 1st place overall.

Two Guys Rally V2 [ July 9th, 2008 ] By:Charles Smith

I hope you have noticed that TwoGuysRally has been undergoing some changes. Combined with the changes we had a peak traffic day to this website from all sorts of other websites (including google). We’re hoping that was a result of caused by you, who so eagerly tell all your racing buddies about us :).

Anyway, expect to see a reorganization of the Articles page, as well as the introduction of a complete sitemap page (link to every possible published page on two guys rally). The ‘?random‘ feature still works and will take you to a random page.

If you notice anything broken, please leave a comment or shoot us a dirty look (aka email). Or if you have any general criticisms of the new layout of the site, leave those in comment form too. We actually do appreciate any constructive criticism.

On a more rally note: Be sure to set your alarm clocks for July 31st (Because I assume you will sleep through to September). The X-Games is airing and their Rally coverage is looking to be good this year. For all of you across the pond, the X-Games is the only easily viewed Rally in the US.

Performance Loss Hunt: Part 3 [ July 8th, 2008 ] By:Mark Ozimek

A while back, I made two posts about my car, and how there is a lack of power in the top end compared to what it used to feel like. I verified that the exhaust isn’t causing significant restriction and that the turbo is making about as much boost as it should be.

Since this is turning into a guess and check thing, mostly because my car is 10 years old and has almost 150,000 miles on it, and I don’t know how it was treated for the first 130,000 miles of its life, I said “To hell with it”, and ordered two things that I highly suspect to be contributing to the problem: Vacuum hoses and a CBV diaphragm.

Unfortunately, the vendor I’m getting the CBV diaphragm from does not have any in stock, nor does anyone else that I could find, replacing that part will sit on the back burner for now.

The silicon vacuum hoses from StylinMotors came in the other day, and sat in a corner of my apartment until I had the time to start ripping junk out of my engine compartment to get access to some of the hoses. Thanks to Independence Day being on Friday, I got a three day weekend to have fun. First order of business was figuring out what each hose does, and where it needs to attach to. Ideally, I would be able to just take one hose out, cut a new one to match and install. Knowing what everything does is something important to me, so I couldn’t make it that easy for myself.

After a couple minutes of fun wrestling with worm gear clamps and torx screws, the engine compartment of my S70 looked like this:

(click for larger image)

Although it looks like a disaster, all I really did there was take out the intake filter box and two intercooler pipes that were in the way of some hoses I needed to get to. Judging from the hose clamp style, the hoses are the original parts that were on the car when it rolled off the factory floor.

After prying the clamp off, I found something quite comical and frustrating at the same time. The hoses had rotted into place! I had to cut off every single hose I changed, since they would not come off any other way. Unfortunately, this meant that some of the hoses that are in tight spots did not get changed, since I couldn’t fit my knife into the area. I still plan on changing them though, I just need to remove more parts that get in the way.

Afterwards, the hoses in that picture had been replaced with silicone parts:

While changing out hoses, I found something very interesting. In the first engine picture, there is a small white thing on the very left edge in the center of the picture. This is a check valve that only allows air to flow in one direction. That hose comes from the intake manifold and leads downward to a T junction. The hose going to the right has another check valve, and connects to the intake hose just before the compressor inlet. The other hose goes to a solenoid that is part of the onboard fuel vapor recovery system.

Since the check valves are aligned in such a way to only allow air to be pulled out of the solenoid that is attached to a carbon filter, a broken valve from the intake manifold means that boost pressure can leak out of the intake manifold to before the compressor inlet or into the carbon filter. Both of these are things that should be avoided due to loss of efficiency and contamination of the fuel vapor recovery system.

Either way, I replaced the hoses I had relatively easy access to. Some will require the removal of the intake manifold, another is attached to the compressor housing, which the bottom part of the intake hose blocks, there is even a hose that runs over the top and back down to the back of the engine to the fuel pressure regulator. I’ll try to address the rest of these when the CBV diaphragm comes in.

So with all that said and done, did it fix the problem I’ve been seeing? Well, no. It actually did some things I didn’t really expect. Acceleration from a stop is now much smoother and more consistent as the engine speed increases. Fuel economy on the highway seems to have gone up by one or two MPG, but it is still too early to tell for sure. The most interesting is that the brakes feel much more responsive now. My suspicion is that there was a/some vacuum leak(s) that allowed air into the system causing minor problems, but not enough to make the ECU freak out. Knowing that is more motivation to go back and replace the rest of the hoses, since they surely have leaks too.

However, the top end power is still lacking, so the hunt to restore my engine to normal continues! I was joking with Charles earlier that I’m probably gonna replace everything under the hood short of the engine itself before I fix the problem.. I suppose time will tell. Until then, remember that preventative maintenance is the best thing to do to keep your car performing as it should.

Rally Racing Online: Japan [ July 7th, 2008 ] By:Charles Smith

The past few weeks were riddled with practice sessions in a rally racing video game called Richard Burns Rally. Why was I practicing? Because I’ve positioned myself to possibly take 3rd place overall in the Rally Sim League’s RBR Rally.

This week I am racing Rally Japan, which is the sixth and final rally of this season. It is the most technical rally in the lineup. It has the slickest off-road surface so having an off or going wide through a turn has a huge effect on the overall stage time when compared to all the other rallies we have seen this season. It also has the longest and highest speed stage in the series: Nokier. And that 7:30-8minute+ stage is driven twice, once forward and once backward.

So with 1 point separating me and ‘VMethos’ I have to place the best I’ve ever placed on the hardest rally. It is also impossible for me or VMethos to get 2nd place as 1st and 2nd placers have gained more than 17 points on 3rd and 4th. However the race for 1st overall is still raging strong between Wild Swede and Turbo. This season of rally has come down to a nail biting finish.

Hopefully I can sneak past VMethos and place on the podium my first ever season with this game. More updates as they come, check back later.

Happy 4th of July! [ July 4th, 2008 ] By:Charles Smith

TwoGuysRally is an American run blog/site, so today being the 4th of July we’re out celebrating our Independence from the rally hungry Brits.

So if you’re in the states, you ought to go out and play with things that go BOOM!

Turbochargers! Part 4 [ July 3rd, 2008 ] By:Mark Ozimek

Last time, I left off talking about how intake and exhaust restrictions should be minimized with a turbocharged setup to increase efficiency and overall power at the same boost level. I meant to cover how the engine must be changed to accommodate a turbocharger, but discussing efficiency ended up to be more involved than I thought it would be.

At any rate, there are quite a few things that must be considered, mostly to prevent the engine from going KABOOM! The things I will cover this time around are:

1. Ignition timing
2. Air/Fuel Ratio
3. Compression ratio
4. Boost control

Now, when I said KABOOM, I meant it quite literally. The primary concern with increasing the boost is knocking or detonation, which is when the air/fuel mixture explodes, instead of burning outward from the spark plug like the engine is designed for. The explosion flame front travels a lot faster than combustion, over 300 m/s compared to around 30 m/s for combustion. This causes a rapid spike in pressure before top dead center (TDC), which can be pretty damaging to the engine. Here is a handy diagram from Volvo that shows what happens when knocking occurs:

As you can see, the expanding circles represent areas that are burning. When knocking occurs, there is detonation instead of, or in addition to the normal combustion.

First, we must understand why knocking occurs. It really boils down to one thing: Excessive temperature. This high temperature can be caused by a few things, like intake temperature being too high, compression ratio too high, excessively hot cylinders and pistons. Something as unavoidable as the increase in temperature and pressure from the normal combustion can cause detonation in another part of the cylinder. Lower octane fuel also burns more readily, contributing to knocking. As quick side note, this is why most turbocharged cars recommend premium fuel.

Increasing the boost pressure increases the final pressure and temperature within the cylinder significantly, which as we now know, greatly increases the chances of knocking. In order to increase the boost a lot to make more power, we must try to prevent knock.

The first way to prevent knocking is to retard the ignition timing. The ECU usually does this on the fly based on signals from the knock sensors mounted to the cylinder block. Retarding the timing may seem counterintuitive, since waiting longer to ignite the mixture means the temperature and pressure is higher, because the mixture is still being compressed. Ignition is almost always before TDC, and ignition timing is measured in degrees before TDC, a negative value indicating that the timing has been retarded to after TDC. Once again, a nice little diagram from Volvo for visual reference:

The curve indicates pressure within the cylinder, a spike occuring after ignition, and a sudden drop-off when the exhaust valve opens at the very end of the cycle.

However, later ignition means that the hot gas from combustion stays in the cylinder for less time, reducing temperature, preventing knock. It also means that if knocking persists, the pressure build-up occurs later, while the piston is traveling downward, decreasing the intensity of the pressure spike. However, the negative side to retarding timing is reduced power output, so we want to run it as close to the optimal timing for the RPM as possible without causing knock. This will typically range from 40º to 30º before TDC, depending on the geometry of the cylinder head and piston.

Another easy way to prevent knocking is to richen the Air/Fuel Ratio (AFR). When there is more fuel present, the final exhaust temperature is ultimately higher, but the extra fuel acts as a thermal damper of sorts, since it takes more energy to heat up more fuel during compression. The temperature during compression is what is ultimately what determines if there will be knock. Making the AFR too rich will also reduce power, and cause the engine to consume a lot more fuel, a doubly bad thing to do. Despite this, many ‘high performance’ tunes will richen the mixture significantly to allow much higher boost levels to be run without knocking.

Getting into the engine itself, there is a very straightforward way to allow for a lot more boost without causing knock. Just reduce the compression ratio, it reduces the final pressure within the cylinder, preventing knock. This is why most turbocharged engines have pretty low compression ratios compared to their normally aspirated (NA) counterparts. For example, my S70 has a compression ratio of 8.5:1, while the NA version of my engine has a compression ratio of 10.3:1. Charles’ WRX has a compression ratio similar to mine, at 8.2:1, and the NA Impreza of the same vintage has a compression ratio of 10:1.

The reduced compression ratio compensates for how there is almost twice as much air in the cylinder as there would be at WOT without the turbocharger. The nice thing is that the final pressure within the cylinder is higher with a turbocharger than is possible with an NA engine, because of how the air is cooled down in the intercooler between the two compression stages. Without getting into the specifics of the math, a higher pressure usually yields a higher efficiency, meaning the engine extracts more power out of a certain amount of fuel. In theory, a turbocharger can be used to increase the fuel economy when trying to reach a specific horsepower target. In reality, turbocharged cars often get worse gas mileage due to the lower compression ratio, and tuning of the ECU for extra power over efficiency.

The other important factor that has not been discussed in detail yet is controlling the amount of pressure that the compressor makes. As I explained in part 1, the compressor and turbine wheel are attached by a shaft. To control the amount of boost the compressor makes, the speed at which it is spinning must be controlled somehow. This is usually done by letting exhaust around the turbine wheel, through something called the wastegate, instead of forcing it through the wheel. The external view of a wastegate that is integrated into the turbine housing looks like this:

(click for larger picture)

The wastegate itself is a vent hole right before the turbine wheel that allows exhaust flow into the exhaust pipe with a valve that is pulled closed by an actuator. In the above picture, you can see a rod come out of the right side of the picture, and end at a small arm. That rod and arm are connected to the wastegate and the actuator. The actuator is vacuum driven in this case, boost pressure is supplied to a solenoid that is controlled by the ECU, with two output ports, one to the unpressurized portion of the intake, and the other to the actuator. The solenoid bleeds off pressure as needed so that the actuator can be controlled by the ECU as the boost level changes.

How the wastegate is controlled changes some important factors, such as how quickly the boost pressure ramps up, if there is “overshoot”, where the turbo temporarily exceeds the target boost level, and so forth. In most stock turbo setups, the wastegate starts opening at a pressure significantly below the target boost level, causing a slower increase up to the maximum boost. This gives the least amount of overshoot, which is good for safety reasons, but bad for performance. One option is to increase the pressure required to start opening the wastegate, which will decrease spool time, but potentially creating overboost situations that may damage the engine if you’re running close to the limit of it’s capabilities.

Another choice that must be made is the wastegate type. There are some turbos that do not have an internal wastegate, and require an external one, either from something like the 5 bolt Garrett flange that has a port for an external wastegate, or by using an exhaust manifold with a tube coming off to go to a wastegate. Typically, the more air the wastegate can flow, the better control over boost pressure there is, to a point. Once there is too much flow, it is hard to have fine control over the boost levels. If there is not enough flow, boost will creep above the target level, which is not good.

So not much math this time around, although if anyone wants me to, I’d be happy to review my thermodynamics notes and explain the Otto cycle and why higher combustion temperature and pressure is better. There is always more stuff to cover on turbochargers, so stay tuned for part 5, coming soon!