things you should know about ride height v2

It’s a pretty common train of thought that lowering a car improves the handling, because of the lower center of gravity. From a physical standpoint, that is true. Lower, wider, and lighter are all keys to improving how a car handles and reducing lap times. But that is not the whole story. Mostly this is because the suspension is designed to operate at a specific ride height/travel range- the one the manufacturer set. So when we go outside of that, some problems can arise.

When it comes to handling performance, it’s very important to keep the tire in optimum contact with the road. What that means is we want the whole tread to stay flat on the ground, and not see any sharp spikes in load. So, for example, going around a corner, we don’t want the tire to get leaned over onto the outside edge, and if we hit a bump in that corner the suspension should be able to absorb it smoothly. To do those things, we need a suspension that is aligned and functioning correctly.

The most obvious problem that comes up with a lowered car is suspension travel. The wheel and tire can only move up so far in the body before hitting the bumpstops, or ever worse, contacting other parts of the car. Tires can rub on the fenders. wheel wells, and wiring harnesses, axles hit the chassis, ball joints and rod ends can run out of articulation.. When that happens, tires get cut up, fenders are mangled, and parts can break. Imagine a tire blowing out or a ball joint snapping off in the middle of a corner.

And then of course there’s the issue of bottoming out the suspension travel. When that happens, you suddenly get a big jolt through the tire and chassis, and a big reduction in stability and grip. There you are, cruising around an onramp, when you hit an expansion joint and are suddenly headed for the guardrail.

Just from that, you should get the picture that you need to be careful when lowering a car. There are a lot cheap, readily available parts out there on the market that can cause these issues, such as springs that are too low and too soft and cause a car to ride the bumpstops constantly, and adjustable coilover systems that can be adjusted so low that axles, fenders, and tires get destroyed. Many of these come from reputable, popular brands, too, so if you want aftermarket suspension parts it’s important to get them from a knowledgeable vendor and have them installed and set up properly.

Still, a car can be lowered without causing much harm. Stiffer springs compress less given the same load, so can make up for a lower height. This has to be moderate though- most car suspension won’t have much more than 3″ of bump travel (and often less), so lower a car 2″ and what’s left? Almost nothing. The suspension is bottomed out just driving along. However, shorter shocks, some adjustable coilovers, and even different upper mounts or control arms can overcome this my simply moving the whole travel of the shock farther up. Then fenders can be rolled and wheel wells clearanced so you get adequate travel and nothing rubbing.

There you have it, right? Get some shorter shocks, stiffer springs, make sure nothing is rubbing, and you’re good to go. Looks cooler at car shows, friends, neighbors, girls, and forum bros will all be impressed, and you’ll probably win super lap battle.

But, of course, there is more to it. This was getting a bit long though, so I’m splitting it into two parts.

things you should know about coilovers

Lately we have read quite a few incorrect comments online about suspension and coilovers, so we decided to write something about it.

Firstly, let’s go over a few suspension basics. There are a few popular suspension arraignments, mainly the Macphearson strut, double wishbone, multi link, and solid axle. Basically every modern car is going to be one of these designs, but that’s not what this post is about. Regardless of the layout, there will be a spring to support the weight of the car and resist roll and pitching movements, and then a damper, or shock absorber, to control the motion of the body and suspension. Without shocks, the body could oscillate freely on the springs and that would not be good. Continue reading

Things you should know about coolant

This will be the first winter my car will spend in a cold climate in a few years, and I realized that my cooling system is in danger of freezing if I don’t add some anti-freeze. This brought me to look up the ideal water to coolant for cold weather usage, and then lead to much more research on cooling systems and how coolant works. I thought it might be a good idea to share results on how the boiling point, freezing point, and heat transfer ability of coolant change depending on the mixture. Also, this would have been easier if my thermodynamics textbook wasn’t in a storage unit 1000 miles away.

Continue reading

Things you should know about suspension bushings

Have you noticed how quiet and smooth most modern cars feel to something a few years older? Drivers are being increasingly isolated from the road with soft rubber, liquid filled mounts, and sound deadening. This is done to reduce what’s called noise, vibration, and harshness, or NVH, and the downside is often a reduction in handling performance and response. The enthusiast driver who actually wants to feel the road is stuck with a numb, disconnected feeling, sofa on wheels.

The nice thing is that there is a fairly easy and inexpensive way to regain some control and performance, in the form of replacement suspension bushings. Bushings are all the little rubber parts in our suspension that absorb vibrations and allow motion. Changing out these tiny, often overlooked bits makes a difference in a number of ways.

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Things you should know about anti-Lag

Anti-lag is a very interesting technology that came about in the 1980s when rally cars started to use turbochargers. To fully explain it, first I have to explain what lag is, and why it occurs.

An engine is an air pump, and the more air that goes into a motor, the more power it will make. The primary factors that determine how much air is flowing through an engine are displacement and RPM (although in reality it is a little more complicated). As engine speed increases, so does the amount of air that goes through the motor. The same goes for displacement: a bigger engine moves more air and makes more power. Most of the time, we don’t have much room to increase displacement or revs. This is where forced induction, and the turbocharger comes in.

A turbocharger is a compressor spun by exhaust gasses. The purpose is to both reclaim some of the lost energy from the exhaust, increasing efficiency, and to increase the pressure of the intake air. Forcing more air (and the corresponding extra fuel) into the engine means that you can make more power with less displacement.

The downside is that it takes some time for the turbo to get going, especially when you are using a large turbo to make a lot of power out of a small displacement engine. Until the engine is moving enough air to spin the turbo, you’re stuck with a low displacement motor with low compression and no boost. This is called turbo-lag. In some cases you can compensate for the lag by increasing the revs to give you a larger in-boost powerband, but you still have that dead spot at low revs and higher engine speeds mean much higher stress on the engine components. Additionally, many racing classes require the use of an intake restriction, which limits the amount of air that can be drawn in, and therefore limits the maximum power and useful rpm range. These inlet restrictors will actually cause lag on all their own due to the fact that the turbo has to draw air through a smaller size hole.

The most simple form of anti-lag, used in the 80s, was to never lift off the throttle. This kept air going through the engine and the turbo spinning, but resulted in significant wear on the brakes and transmission, especially given that some rally cars were making over 600hp. Soon, systems were created to keep the turbo on boost even when the throttle was lifted.

To generate the low end power and response required by a rally car, it’s necessary to have the turbo spinning as soon as possible, creating boost before the driver actually presses the throttle. The simple way to do this is to keep the throttle partially open so plenty of air is going through the motor, dump a bunch of fuel, and then wait until the super-rich air fuel mixture is on the way out the cylinder before igniting it. Instead of having the combustion event force the piston down to make power, it explodes going into the turbo, creating boost.

As you might imagine, having the combustion occur in the exhaust is bad for the exhaust valves, exhaust manifold, turbocharger, and anything else in the vicinity like an EGT or O2 sensor. It sounds a little something like this:

The “add fuel, retard timing” form of anti-lag was used in the late-80s to early 90s, at which point rally teams began to come up with more sophisticated methods. Bypassing the combustion chamber entirely and injection air straight into the exhaust manifold allowed more boost at lower rpm. The Mitsubishi EVO VI, for example, came stock with an air injection anti-lag system that could be enabled simply by modifying the ecu. Then Prodrive came up with an even more complex system:

That little doohickey attached to the up-pipe is known as “the rocket.” A canister connected to the charge pipes stores pressurized air, and when the throttle is closed an air/fuel mixture is ignited in the rocket, spooling the turbo. This allows the 2.0 Subaru WRC motor to create useful boost (and 200hp) at the idle speed of 2000 rpm. By 2500 rpm the manifold pressure is 30psi, and reaches a maximum of 45psi by 3000 rpm. Peak torque is 520 lb-ft, and a little over 300hp is available from 3000 to the 7500 rpm redline. The important part about this system is how precisely it can control turbo speed and boost. By using a turbo speed sensor, this system is much more efficient, and allows more manifold pressure at lower revs with less wear to the exhaust components and turbo.

Things you should know about ride height

It’s a pretty common train of thought that lowering a car lowers the center of gravity and improves handling. Unfortunately that is not the whole story. When it comes to handling performance, keeping the tire in optimum contact with the road is the most important consideration. That means that the tread is flat on the ground, and has the most consistent contact with the ground possible. So with that said, lets go over a few things that happen with the car is too low.

The first problem that occurs with a lowered car is a reduction in bump travel. If you don’t have enough bump travel, you’ll be hitting the bump stops or even riding on them all the time. That takes away from the struts and springs being able to do their job, and creates sudden loading increases to the tire. Remember what I said about keeping consistent contact with the ground? Well hitting the bump stops is not consistent contact. This sudden bump in load drastically reduces grip. If your car is too low, you may feel this as a skipping or unsteady feeling while cornering over bumps, or perhaps just a general lack of grip. It will certainly make your laptimes significantly slower.

But wait, there’s more!

There’s something called a roll center. The roll center is a point the body of the car tries to roll about. Or, more specifically, the point the center of gravity tries to roll about. So if you increase the distance between the roll center and center of gravity, you increase the roll couple, and therefore increase body roll given the same lateral force. So that’s fun, right? Generally speaking, lowering a car lowers the roll center. All else the same, this INCREASES body roll, (although I’ll admit some of the extra roll will be offset by the lower center of gravity). With this little tidbit, we’ll move onto what’s called the camber curve.

Remember that part I said about keeping the tread flat on the ground? That’s where the alignment and camber curve come in. As the suspension moves through it’s travel, the alignment changes. Ideally, negative camber will increase with bump and toe will experience little to no change. With double wishbones and multi-link suspension, this is pretty common. Camber gain is important because in a corner the car leans over and the outer tire leans over. Using the suspension geometry to lean the tire inward with bump keeps the contact patch flat with the ground and increases grip. Most suspension geometry does not do this well enough, especially when the car has been lowered. Macpherson strut systems (used on subarus and evos for example), will lean the tire in a bit at first, and then lean the tire outward. That means the tire is riding on the outside edge and sidewall. Guess what that does for grip?

So, in conclusion, lowering your car too much will cause you to ride the bump stops, increase body roll, and reduce the amount of tread in contact with the road. Any of those three are cause for concern when lowering a car. Most of the time, when a car is lowered, all three come into play. And that’s just not functional.