|
|
|
OFTEN OVERLOOKED ENGINE ENHANCEMENTS |
|
|
|
|
Written by Administrator
|
|
Tuesday, 15 November 2005 |
Ok, so you're looking to grab every last bit of reliability and power out of your engine. You know about the turbochargers, nitrous oxide, and head porting. But you're thinking where else can you scrounge up more. Well listed below is a few tips and tricks that can be done to your motor and what each one actually does to help you out.
CRANSKHAFT KNIFING AND TIPS
Just as is states, crankshaft knifing is a process in which the leading edges of the crankshaft counterweights are machined to cause less wind resistance. The term normally used is windage, and this is the resistance the engines' internal rotating parts face while operating. By lowering windage, you don't really create more power, but you do get quicker throttle response.
Crankshaft lightening and stress relieving are also done to high performance engines. Lightening the crankshaft in specific places lower the rotational mass of the crankshaft, resulting in much quicker throttle response and more useable power. It also can add to the overall rev limit to your engine as the rotating mass of the engine has been reduced. Stress relieving the crankshaft prevents uneven stress loads on the journals and counterweights and helps prevent crankshaft distortion and failure.
Nitride coating can also be done, at a high expense. This coating hardens the surface of the crankshaft for even more durability. There are a few different nitride coatings that are used but cobalt and titanium nitride are the most popular. Unobtitanium is an ultra hard coating and if you're adding this to your crankshaft, you better be driving a porsche. It's a ungodly expensive coating with a surface hardness close to pure carbon(ie diamond)
Another simple trick to perform on the crankshaft is to chamfer the journal oil feed holes. At high RPMS, the oil feed holes on the crankshaft can actually shave oil away from the bearings. Chamfering the oil feed holes prevents this from happening. It can be performed at home with a carbide roll and die grinder but should be done at a shop along with journal polishing. You simply chamfer, or taper, the oil feed holes parallel with the bearings oil channel. The oil feed holes in the crankshaft will now squish the oil between the journals and the bearings, rather than scrape it away.
SPARK PLUG INDEXING
A common trick in engine tuning that can help you gain horsepower is spark plug indexing. Spark plug indexing is a procedure that aligns or faces the outer electrode on all of the spark plugs in and engine, with a specific area within the combustion chamber. In a perfect internal combustion engine cylinder, there would be no obstructions. This is obviously not possible, as the spark plug must protrude into the cylinder to ignite the fuel mixture. The only part of the plug that really protrudes into the cylinder causing an obstruction, is the outer electrode. When the spark plug fires and ignites the mixture, the center(or kernel) of the reaction starts right at the spark. The reaction expands outward in all directions and thus power is created. Now, when the kernel hits the electrode, it must divert around the electrode to burn the surrounding mixture, disrupting power and reaction flow. The mixture in the area behind the electrode burns slower, causing an uneven and often incomplete fuel mixture burn. There is no way to avoid this as the electrode must face somewhere in the cylinder, but you can direct it so that the mixture is burned in the most efficient manner possible.
First, the main goal is to find out where you need to direct the electrode. Combustion chamber design will determine the overall gain or loss of certain electrode positions. Once you find the optimum position, power can be slightly increased but the most gains will come with engine response and fuel economy. If you don't know the right location, it's going to be a matter of trial and error. Pick a direction and go at it. Normally people start with all the electrode gaps facing the intake manifold, that is the actual electrode faces the exhaust manifold. Others say that the gap should face the exhaust manifold. Your engine will be the determining factor. To index the spark plugs, simply pick up a set of indexing washers. I used the copper ones from Moroso. These are very thin washers that got between the spark plug and the head. They vary in thickness and allow you to stop the plug from rotating past a certain point when installing them. The way I mark the plugs so you know where the electrode is pointing is simple. Take a sharp hard chisel and scrape a small line or mark in the top of the plugs contact that points to the gap on the spark plug. When you install the plug into the head you can shine a flashlight at the plug and the scratch will reflect the light, showing what direction it is facing. Now you just have to do some trial and error and get all the plugs lined up the way you want. Start out first by marking the plugs and installing them without washers so you know where they point to begin with. Try out various electrode positions and see what performs the best. I found that on my 420A, it was best to face the gap of the plugs at the exhaust manifold. It just seemed to me that the best throttle response occurred at this point
PISTON DOME AND COMBUSTION CHAMBER WORKING
If you're an at home mechanic and are rebuilding your engine, this is and area where you can make up some noticeable horsepower gains. Another addition to the perfect combustion chamber is one that has absolutely no flat, polished surfaces and edges. With enough time and patience, this can be accomplished.
Flat surfaces and edges in a combustion chamber are like mirrors. They reflect waves and cause many things to happen. Power loss and detonation are among the effects. Just like light or sound, the energy released inside the combustion chamber bounces around, losing power as it does. New pistons, like those of JE or SRP, come looking really nice. Yeah, nice and polished that is. One of the first and easiest piston working tricks is to lightly sand the piston dome to a super smooth, but dull finish. Use a light 2000 grit and dry sand the piston domes/valve recesses just to the outer edges of the piston dome. Get every last bit of the dome, but don't sand the piston skirt. By doing this you've just knocked down a major reflecting surface, thus creating more area for the reaction power to be absorbed and put to the crankshaft.
The next step is to remove the sharp angles and edges on the piston dome surface. You'll need a die grinder and a light carbide roll to do this work. A dremel tool and a coarse carbide cutter work just as well. Holding the piston by hand(not in a vise!) take the die and lightly round off the sharp angles on the piston dome, normally near the valve recesses and indents. Don't remove too much material or you will start affecting the compression ratio. On my pistons, I rounded back the edges about 2mm, anywhere where a flat surface was. Sand the areas you remove material from with the sandpaper again to dull them up again. After this you will need to have the piston assemblies balanced for proper harmonics. It's good practice to do so in engine rebuilding.
Combustion chamber work is more delicate and you must be careful of the valves and valve seats. Most engine manufacturers remove casting flash (excess metal) left over from the casting process, but tends to leave behind areas that have uneven spots or flat spots. You need to take the die and remove these imperfections if any at all. DO NOT GRIND THE VALVES. DO NOT GRIND THE VALVE SEATS, just the areas between and around them. Ridges and creases should be removed. Areas near the spark plug holes and outter edge of the combustion chamber should be addressed as well. You can sand the quench pads and valve faces after this, but be sure to remove ALL particles and abrasive from the head after this procedure is complete.
CERAMIC AND TEFLON COATING
Yeah that's right! Ceramic coating is not just for headers and turbine housings. It's also used on internal engine components. The main reason is to retain heat in the combustion chambers. Heat is power and the less that is lost to the engine itself means more to the ground. Heat keeps up exhaust velocities and that means a better flowing engine. It's also a way to prevent hotspots on combustion chamber parts, preventing detonation from occurring. This is normally a shop only procedure. If you plan on having it done, get the piston domes, valve faces, exhaust valve backsides, and combustion chamber roofs coated.
Teflon coating is mainly used on the piston skirts, but can be used on anything that encounters friction. Bearings, bearing surfaces, valve stems, etc, can all be Teflon coated. The Teflon coating lowers component friction freeing up more power, but also adds to engine component life. Piston clearances can be smaller, allowing a tighter clearance between the piston and the cylinder wall. This prevents power robbing and engine damaging piston ring blow-by.
|
|
