It is really un-nerving for me to think about all the conversations I have with people that think that simply installing a bigger camshaft, a smaller supercharger pulley, a high flow exhaust or a better intake will be “THE” answer to more performance. The over-used statement that the internal combustion engine is a simple ‘air pump’ never seems to get the point across. The Engine is really a complex number of components that MUST work together to produce the power to turn the crankshaft, that turns the transmission that turns the wheels that move the car. It is simplistic to think that simply changing one component without considering the rest will result in the optimum performance increase.



A factory engine design team makes a major effort to make all things work together well, while working within cost, performance, drivability, reliability and emissions design constraints. They establish a target for performance and each component is chosen to optimize towards that point. If they target to have “X” horsepower, they can then adjust each and every component to that point. Everything from boost pressure, throttle body port size, exhaust system, valve sizes, etc. all are established to meet the target. Changing any one of the many options may indeed gain some performance but by no means is optimized.



Going back to the popular ‘air pump’ analogy, let’s consider the single most popular ‘upgrade’ done to the Mini Cooper “S”; increasing the boost pressure. There is no question that there is HP to be gained by simply increasing the amount of air being forced into the combustion chamber. While the factory by design must be conservative in their choice of components and thus will always build-in a margin for error in favor of reliability, there are real engineering limits to what we can expect from a single simple component change. Increasing boost pressure consumes horsepower and generates heat which must be dissipated by the intercooler. The intercooler on the MINI is marginal at best, and its capacity is easily exceeded, negating the potential gains of increased boost pressure. The real question regarding performance enhancements, is how to know when we exceed the point of diminishing returns, where we no longer achieve optimum performance from an upgrade.



The MINI supercharger might be thought of a multiplier. It takes horsepower to make it rotate and in return it forces more air/fuel mixture into the combustion chamber, which in turn results in more HP. The intent is to get more than you give.



But increasing the air out of the pump is only the first step, you then have to get it into the combustion chamber and to do so you have to pass it thought the ports of the cylinder head and then past the valves. As we increase the blower’s output, we can quickly approach or exceed the head porting design limit established by the factory. Getting back to a more optimum balance of components will have many beneficial results. If we make it easier for the supercharger to deliver the desired amount of air it will work less and since the basics tell us the work equals horsepower, we will consume less hp for the better results. And if the pump is not working as hard it also can deliver a cooler air mixture which results in a more dense mixture, which again equals more horsepower.



So what can we do to the cylinder head to regain some of the balance of components? Air flows into the valves by ways of ‘ports’. The shape and size of these ‘ports’ control ‘flow’ and ‘velocity’. These are the 2 critical components of port design. The optimum design will yield the highest flow (volume) of air while maintaining the highest flow (volume). If you think of the port as a straw it is easy to understand that as the diameter is increased the flow will increase but with the same input pressure, the velocity will have to decrease. The result of flow and velocity might also be thought of as low RPM verses high RPM performance. You need the velocity at low engine speeds to produce the HP but if the volume is not there at the high RPM, the engine will not achieve maximum horsepower and torque. This is why we leave porting to the professional with access to the proper flow testing equipment. An amateur with a die grinder will tend to make the ports way too big, drastically dropping the intake charge velocity and ruining power (not to mention ruining the head).



When building a full race motor. it is not uncommon to give up low end performance in favor of total HP at high RPMs that can be maintained on a race track. Since most of us also want to be able to use our cars on the street or least need a wider RPM range- then we MUST balance Flow and Velocity.



This is the real ‘art’ required to get the optimum performance from a ‘port job’. As we have probably already increased the pressure from the blower (15% reduced pulley) we now must modify the cylinder head to again re-establish that optimum balance of flow and velocity. The ‘art’ typically requires not just an understanding of how to do it but also often requires a number of hours of very intensive hand operation with high powered die grinders followed by hand sanding to finish the job.



Why isn’t this level of attention given at the design and manufacturing process? While the factory engineers well understand the benefits of porting cylinder heads, it is one of the engineering/cost compromises that must be made in modern production engines.



The general practice In cylinder head porting is to carefully hand reshape both the intake and exhaust ports to enlarge them slightly while straightening out the airflow path and reducing obstructions that result in any sort of pumping loss. As you reduce the turbulence you increase air flow. This is also a balance as a perfectly smooth mirror finish port wall can result in a negative if the fuel atomization is compromised. Most cylinder head tuners will leave the intake port ‘looking’ rougher than the exhaust for just this reason. It is very common for a good porting facility to test both their progress and their finished product on a flow bench. This device is the best way to quantify the gains, short of putting the head on an engine and engine dyno to prove the results. A good port technician can establish a baseline on a flow bench and then be able to do many ports and heads to the exactly results that can be verified on the flow test bench.



The next step in the process is to get the air past the valves. There are two levels of performance that can be considered. The first hurdle is how to get the best flow from stock valves. The more important hurdle is how to balance increased pressure from the supercharger by increasing the size of the valves. It has been proven that 50% of the gain typically found in cylinder head tuning is achieved by the simple process of doing a high performance ‘valve job’. The factory again accepts compromise for cost and manufacturability and thus you will find single angle valve seat in a production head. These are typically a wide area 45-degree cut on the edge of the valve and corresponding seat area in the head. These are easy to do and as the valve size, etc. has been designed for x-horsepower there is no need for the factory to spend more money.



Just as we reshaped the ports of the cylinder head to improve flow, we can do the same with the seat area of the standard size valves. A ‘multi-angled valve job’, typically 3 or 4 angles will result in smoother transition for the air and greatly enhance flow, while maintaining adequate valve seating area for the necessary dissipation of combustion heat. This precision process is considered standard practice in performance tuning shops.



Multi-angled valve seats are one improvement that does not require the trial and error ‘art’ that is found in cylinder head porting. Requesting a 3-angle valve job should be considered the minimum that you would ask from your machine shop. Typical 3-angle valve jobs include an angle cut on either side of the actual sealing area of the valve seat. The high accuracy required of this technique means that the seat area is kept to a minimum (often less than half of the original seat area). The net result is that the gasses are encouraged, or funneled” through the valve-to-seat opening. The flow increase is dramatic. The intake seat width is typically about .040″ while the exhaust is kept a little wider (.050″0 to allow for better heat dissipation. It is critical that the corresponding cuts in the valve seats be matched and thus it is important to not switch valves between cylinders.



15% pulley reduction increases boost by 10%, from a max pressure of 10lbs to 15lbs. As a positive displacement pump this means you get a higher velocity of air sooner although not much increase in flow or volume. Porting and a good valve job will still leave you short of the needed improvements to reach optimum potential provided by the pulley size reduction. The next logical step is to increase the size and lift of the valves. Again, this must be done with the understanding the need to balance flow and velocity. Remember that we have said the flow is more important at high RPMs while velocity is critical at the lower RPM. Since the blower upgrade mostly produces more velocity, then in order to keep this balance the focus needs to be on flow. This is best accomplished with increased valve sizes. Another compromise that we must keep in mind is the need to keep the correct ratio between intake and exhaust flow. In the ideal cylinder head the exhaust should flow at about 70% of the intake. This balance is maintained both in port design and in valve sizes. For the MINI we have discovered that by increasing the intake valve size by 2% and the exhaust by 6% we not only can regain the ideal balance of intake verses exhaust but the increased flow (combined with a top quality porting job and valve job) allow you to get much closer to reaching the potential benefits of reducing the pulley size.



While all this head work provides great benefit in and of itself, a performance camshaft, with properly engineered duration, overlap and lift, will put the finishing touches on your re-engineered, high performance MINI cylinder head. With other engines, the available space above the head allows for many variations in camshaft design. Discussing these choices and the resulting performance and drivability impacts is a subject for another paper at another time. Suffice it to say that for the MINI, the physical limitations of the camshaft area on top of the head limits the performance gains and potential impact to drivability. These limitations include taller lobes interfering with the metal spark plug tubes, and requirement of maintaining the stock base circle diameter of the lobes because of the integral rocker-arm/hydraulic lifter design. The net result of these physical limitations is that all performance camshafts for the MINI (that we know of) all perform similarly.

Our intent with this paper is to provide you with some guidance as to understanding the considerations pertaining to cylinder head work. We hope we have helped you to decide whether to undertake such a project yourself with the skills of a local “head guru”, to trade in your stock head for ported head in the interest of expediency, or to table the whole matter and leave the pursuit of serious power to more hard core enthusiasts. Whatever your choice, we say to you “Happy Motoring”.

Visit www.Minimania.com for further technical information.



About the author:

Don Racine has been building and racing cars for the last 30+ years. As the owner of Mini Mania Inc. I have had extensive experience in building performance engines for both the original Classic Mini Cooper and recently the BMW MINI Cooper

Technorati Tags: automotive, autocare, auto care, car care, auto repair

Many a night during my years of driving a tow truck I pulled up to a vehicle sitting in the lane on a highway with a flat tire while cars braked and skidded behind it to avoid hitting this obstacle, and what do you think I heard as the excuse for sitting there in the lane risking life and limb? “I did not want to ruin my tire, or wheel.” Let me be the first to tell you, if you don’t think your life, or the life of other motorists on the road is worth more than the tire or wheel on your car, you should be on a psychiatrists couch not behind the wheel. I do not care if you have stock wheels or a phat set of spinners, your life is worth enough to damage those wheels or tires to get yourself to a point of safety and out of the way of traffic. At which point you can wait for assistance or take the time to make repairs on your own.

The only time I was ever more angry than the above situation is when I pulled up at a similar scene only to find a police car sitting behind that same car with the flat tire, blocking traffic and causing a potential safety hazard. As far as I’m concerned that is two people who do not know the value of safety. The most important thing to remember in a time like that you want yourself and the motorists around you to make it home at the end of the day. The wheels and tires can always be replaced.

When you get a flat tire, no matter what type of vehicle you are driving the most important thing to remember is to turn on your hazard lights, gradually take your foot off the gas allowing the vehicle to gradually decelerate, and get off the roadway, out of the lanes of travel as quickly and safely as possible. When you do this you not only get yourself to a point of safety where you can calmly survey the situation and choose the best course of action, you also make the roadway safer for everyone else.

No matter what your financial situation may be, getting killed because you did not want to ruin a wheel or tire is not going to pay any of your bills or save you any money. Everything material in life can be replaced, your life, or the life of the person who slammed into your car because they were going too fast and did not have time to stop, can not.

Take the time to get to safety and you have done something good for yourself and for all the other motorists on the road.

About the Author

Fred Ost is a writer, web designer and spiring indie movie maker. He is a founder of, and staff writer at the free independent artits community at http://www.scptv.net.
He also offers personal safety products through http://www.pepperspraybargains.com.

Technorati Tags: automotive, autocare, auto care, car care, auto repair

Guidelines in buying cars online

The Web is a hassle free place to shop for cars. There are many advantages to shopping cars online. First, it greatly reduces the hassle of dealing with car dealers and salesmen. When buying a car online, you don’t have to listen to a dealer talk about the specs of a car. You just have to read all about it in a website. You don’t have to go to a showroom, you just to have to point and click your mouse and you could browse through different make and models of cars. And if you want to take a second look at a car it’s very easy.

The advantage of shopping for a car online is that all transactions can be done without you having to go out of your room. After ordering the car you want and paying the price, all you have to do is to wit for your brand new vehicle to be delivered to the nearest dealer. Some dealers would even deliver the car right at your doorstep (or garage for that matter).

There are basically two types of online car shopping website. One will only get you in touch with a real car seller. This means you have to transact the traditional way. Then there are websites that would take car of everything. Some websites would even deliver the car at your doorstep. Of course this would entail a bigger amount of service fee. And deliveries are made only to nearby areas.

But before you click and buy, you must first know exactly what kind of car you want. Determine the types of car you’re looking for and the price you are willing to pay for that car.

Below are some other tips on how to buy a car online.

1. The most important thing to do is to research. Don’t get too excited. Check on the different packages available.

2. Make sure that the Website you go to is secure and reliable. Most sites would let you browse by car type, by price range or both.

3. If you don’t want to make all transactions online then you could ask the dealer to meet you in person once you found him on the Internet. Upon meeting the dealer, negotiate with him as you would a normal car dealer and then sign the papers.

4. It’s not necessary to pin the model, year and male of the car you want to buy. Just a general picture would do. Determine how you will be using your new car and the reason why you are buying a car in the first place. Ask yourself what features are important to you. Do you give much ore importance to fuel efficiency than speed or vice versa? Are you more concerned about safety features than a good sound system? After you’ve done all these, it’s time to determine your budget. Just how much are you willing to spend for a vehicle?

5. Once you have decided on a brand and model car it would be prudent t6o check on the history of the particular car line. You can easily do this by consulting consumer magazines and websites. You could also check out the website of the cart’s manufacturer (e.g. Ford, Toyota, BMW, etc.)

6. If you cannot afford new models, there are websites hat sells used cars. Popular search engines usually have an automotive section so this is a good place to shop. If you don’t find one here you can try searching using the search string “used car.”

7. Check the background of the website of the online car dealer by clicking on the “about us” section of the site. It is advisable to buy only from websites which has detailed information about the vehicles they are selling. Ask if they have conducted inspections of each car in their lot through independent mechanics. If they have, then you’ll know that that website is a good place to shop for cars. Most manufacturers’ Web sites have detailed information on models, including available options, photos and MSRP (Manufacturer’s Suggested Retail Price).

8. Read reviews about the different make, model and year of cars. A good website must also have reviews and ratings for the cars they are selling. But you should also cross check by visiting independent car sites or sites that do not sell cars or are connected to car companies to get a more objective review.



About the author:



Jay is the web owner of http://www.new-cars-in.com New Car Quotes, a website that provides information and resources on searching for new cars, new car pricing, loans, and dealers. You can visit his website at: http://www.used-cars-in.net Used Car Prices

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