Difference between revisions of "Category:Performance Tuning"

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==Required Reading==
 
To familiarize yourself with two stroke engine tuning, read the Two Stroke Tuner's Handbook by Gordon Jennings as well as Two-Stroke Performance Tuning by A. Graham Bell.
 
 
*[http://edj.net/2stroke/jennings/ Two Stroke Tuner's Handbook by Gordon Jennings]
 
*[http://www.kreidler.nl/artikelen/performance-tuning-graham-bell/performance-tuning-graham-bell.pdf Two-Stroke Performance Tuning by A. Graham Bell]
 
:''Click [http://sharebee.com/b79ceb7a here] for a .rar file that includes both of these sources.''
 
 
A slightly better scanned version of the Jennings Handbook may be found [http://www.vintagesleds.com/library/manuals/misc/Two-stroke%20Tuner%27s%20Handbook.pdf here].
 
Another link to Graham Bell's book
 
 
http://3cyl.com/mraxl/manuals/bell/performance-tuning-graham-bell.pdf
 
 
==Better, Faster, Stronger==
 
You'll get noticeable power improvement on most mopeds by the following performance modifications, however, '''the system is tuned to work together overall, so changing one variable may affect other components and require further tuning.'''  The most common example is the need to [[upjet]] when changing any part to one that allows the engine to consume more oxygen, such as a bigger exhaust, carb, cylinder kit, etc.
 
 
[[Upjet|Upjetting]] is a technique used to achieve an appropriate [[fuel/air mixture|mixture of fuel and air]]. The main technique for determining whether the [[jet]] is the correct size is the [[plug chop]]. However, with more complex carburetors (such as the [[Dellorto]] PHBG), this technique on its own will not suffice since it mainly gives information relating to the mixture at [[WOT]] while the mixture at other throttle openings can still vary widely.
 
 
== Moped Performance Tuning Spreadsheet ==
 
The spreadsheet contains a variety of successful setups. All contributors post in the Moped Army forums, and their information will give you a good starting point to get maximum performance from whichever aftermarket part(s) you have purchased. Please feel free to contribute to the document.
 
 
[[Moped_tuners_spreadsheet]]
 
 
== High Flow Air Filter ==
 
A high flow [[air filter]] will increase the amount of air flow capable of flowing through your intake.  Most of these filters are made out of foam or another similar material.  You must [[upjet]] if you install a high flow filter in order to match your increased air with an increased amount of fuel.
 
Metal mesh and fabric [[K&N Filters For Dummies|K&N style]] filters are available and also covers ordered to restrict rain or water from entering the intake system. Upjetting is required with any modification.
 
 
==Performance Exhaust==
 
'''For most mopeds, this will be the best performance improvement, and the easiest for the average person to do in an afternoon.'''
 
 
Many mopeds of 1970-1985 vintage had exhausts tuned to deliver the most power at approx 25mph.  As the engine goes faster, its cycle rate moves out of the power band of the exhaust, and the exhaust begins to restrict the amount of fuel available for combustion, which self-limits the top speed.
 
 
However, if you replace the stock muffler with one with a power band that is higher, your top-end speed will increase, but at a cost of the low end power. For most moped riders under 200lbs, this really isn't an issue.
 
 
For example, on a [[Honda PA50I(PA50M) and PA50II *General Information*|Honda Hobbit]], you can get up to an ''8mph'' improvement, just by swapping out the stock muffler with a [[puch exhausts|Proma Circuit]] exhaust.
 
 
Of course, every model of bike is different, and you'll need to use the forum search function on the 'Performance Tuning' forum to find what people recommend for ''your'' model. You should [[upjet]] your moped when you install a performance exhaust and then perform [[plug chop]]s to make sure your moped is getting the right [[fuel/air mixture]].
 
 
*To learn more about how [[expansion chamber]] exhaust systems work, read this great primer: [http://www.motorcycle.com/how-to/how-twostroke-expansion-chambers-work-and-why-you-should-care-3423.htm How two-stroke expansion chambers work and why you should care]
 
*For an illustrated summary of Puch Maxi exhausts, you can look here: [[Puch Exhausts]]
 
*If you are interested in building your own exhaust, visit this link: [[DIY expansion chamber exhausts]]
 
 
==Bigger Carburetor==
 
Installing a bigger [[carburetor]] will increase the amount of fuel leading to more power.  Oversized carbs need a intake manifold with a minimum ID of at least that of the ID of the exit of the carb. The hard part is getting the air to gas ratio correct so that you don't cause a [[seizure]] or foul plugs.  Controlling the gas flow can be done by changing the size of the [[jet]].  Controlling the air flow can be through the use of special [[air filter|air filters]] or by drilling holes in your air box.
 
 
You can also try [[Over Boring Carburetors 101|over-boring]] your carburetor. The process isn't very hard and saves a lot of money.
 
 
*Having trouble tuning a [[Dellorto]] PHBG? Take a look at [[PHBG tuning made easy. (a step by step guide)]] and [[How To Tune PHBG Carburetors]]
 
 
==Gearing==
 
By changing the front and/or rear [[sprocket]] you can redistribute speed to top or low end depending on your needs. Usually increasing top end with this method decreases low end, and vice versa.
 
 
Changing the size of the rear tire will have a similar effect. On most moped sized tires width and sidewall height are the same. Increasing your tire width 1/2" results in a 1" taller tire and a 3.14" gain in circumference. Therefore each 1/2" increase in tire size results in an increase of 3" per wheel revolution.
 
 
*For more information concerning gearing and performance, please see the [[gearing]] article.
 
 
==High-Compression Head==
 
[[Cylinder head]]s can be obtained that increase the [[compression]] in the [[combustion chamber]] leading to faster strokes leading to increased speeds.
 
 
*Want to raise the compression on your stock cylinder head? Read up about the technique in the [[head milling]] article.
 
 
==Reed-valve intake==
 
A [[reed valve]] intake has a lot more tuning potential than a piston-controlled intake. Read how to make your own on a Puch engine (and any other engine if you're handy).
 
 
*Want to make your own reed-valve kit? See [[DIY reed-valve kit]].
 
 
==Cylinder Porting==
 
Cylinder porting is one of two arts - the white art of [[Port Matching]], and the black art of [[Port Reshaping]].
 
 
*See Smitty's full [[Smitty's Cylinder Porting Guide|article]], as transcribed from the forums, for a guide to cylinder porting from the guy who does it for a living.
 
*For information about calculating timings, see [[Calculating timing]]
 
*You can use [[:Image:360degtape.pdf|this degree tape]] to help you figure out your port timing if you have a Puch or Tomos-sized flywheel.
 
 
==Kits==
 
These [[Speed kit|kits]] replace your [[cylinder]] and [[piston]] with a [[Engine Displacement|larger bore]].  Generally, you will also need to [[upjet|re-jet]] your [[carburetor]] to allow a greater volume of [[fuel/air mixture]] to enter your engine. You will also need to re-jet to allow the carburetor to deliver enough mixture to sufficiently lubricate and cool the cylinder and piston. If you do not supply enough mixture, the piston and cylinder will overheat, typically resulting in [[seizure]].
 
 
Installing a kit can be done in weekend, and it gives good performance when installed and broken-in properly.
 
 
Most kits recommend a 300 to 800 mile break-in period after installation to allow the [[piston ring|rings]] on the piston to use the fine scratches (called honing) in the cylinder to gently polish into a smooth, well seated finish. Many theories and break-in techniques have surfaced over the years. You should do some research; Google it or search in the [http://www.mopedarmy.com/forums/performance/ Performance Tuning forum] and then decide for yourself which one to use. One method is listed [[Kit break in guide|here]]. Sources agree, though, that over-revving the engine and showing off your new kit to your friends by throttling all the way up is a sure way to destroy your new kit if it's not properly broken in.
 
 
Note that some kits can increase your engine displacement above 50CC, which may change your moped to a motorcycle due to your [[Moped laws|state's laws]].  Make sure to check with your DMV before you spend the money on a kit!
 
 
*If you want an indication what speed you can get with different types of Puch Maxi cylinders, you can read the [[Puch speed/setup table]] (similar to the tuning spreadsheet). Descriptions and photos of Puch kits are in the [[Puch cylinder kit summary]] article, and if you can't decide which Puch kit to get, check out [[Puch How to Choose a Kit]].
 
 
*Never installed a kit or taken off cylinder before? Read [[Install a kit]].
 
 
==Performance Crank==
 
Installing a performance [[crank]] alone does not increase your speed. A performance crank can, however, influence the carter flow and the combustion chamber size.
 
 
A performance crank with full "cheeks" can improve the carter flow. Sometimes there are holes in the cheeks, filled out with nylon or cork. This is done to reduce the weight of the crank, increasing gas reaction but reducing low end torque. This is mostly done on high-rpm machines, since they don't need a lot of low end torque.
 
 
Some performance cranks have a different stroke that allows for greater or less displacement. A common misconception is that a shorter or longer connecting rods would influence the length of the stroke. This is not true. The stroke is determined by where the shaft is connected to the crank, how far it is off center. The further off center, the longer the stroke.
 
 
Shorter or longer con-rods are used to fit cylinders that are not meant to go onto a specific engine. Although it does not fix the timing-problems, it does fix the piston coming above or too much below the cylinder.
 
 
==Stroke==
 
The stroke has a major part in how an engine performs. It's not easily changed (as it requires a different [[crankshaft]]) but some people have managed to machine cylinders to engines with a mis-matched stroke.
 
 
*Read about a lot of different strokes here: [[Moped and scooter strokes]]
 
 
==Really Fast, But Not For Long==
 
===Nitrous Injection===
 
Makes you go real fast for up to 5 seconds.
 
 
The problem? You run ''really'' lean for those five seconds, and every time you use the nitrous, you have a good chance of causing your engine seize from lack of lubrication. Nitrous is easy to get in the form of whip cream cans and best to inhale it fresh. gigggles....
 
 
side note: N2O contains 33% oxygen, only about 11% more oxygen than air which has about 22%. Running a dry shot '''after''' the carb leans the fuel mix in proportion to the amount of nitrous injected this is why manifold injection needs to always be a wet shot or very very small. Running nitrous '''before''' the carb will allow it to take some fuel along resulting in a consistent 25% leaning effect when comprising of 50% of the total incoming cfm, though the longer and more nitrous used the more the cooling effect may cause a slowing in fuel travel through the carburetor's fuel circuit. (example: If you inject nitrous at 1/10 the volume of the incoming air you will only be 5% lean.)  Leaning may be good though; 2 strokes generally make more power at HIGH rpm's when lean and also this can be used to counteract a carburetor's nature of over richening as rpm's rise/vacuum rises for a given throttle position, generally noticeable at max rpm and WOT. Though the MAJOR ADVANTAGE of nitrous isn't the added oxygen but the cooling effect of being a liquid when compressed and quickly becoming a vapor when released, in a wet shot to the intake manifold this causes a increasingly HUGE vacuum drawing in more air and fuel trough the carburetor and also cooling the air/fuel mix making the volumetric efficiency much better, sometimes too good... BLAMO!!!
 
 
===JATO Rocket===
 
A Jet Assisted Take Off unit will make you go ''really really really'' fast for up to 7 seconds... straight into a tree.  And fry everybody behind you.
 
 
===Nitromethane/ Glow fuel===
 
Nitromethane, also known as RC-car fuel is an alcohol and nitromethane based fuel that cooler than gasoline. This increases the performance greatly.
 
 
 
 
Nitromethane is a monopropellant which means it can burn in the absence of air.
 
Nitro Methane contains nitrogen and oxygen, which provides more "fuel" for the combustion process
 
The oxygen contained in nitromethane is released during the combustion process allowing richer needle settings that pack more fuel in the combustion chamber.
 
More fuel plus more air potentially equals more horsepower when engines are designed to run on fuels containing nitromethane or the amount of nitromethane that you run.
 
 
Don't use more than 15% nitromethane, as it will surely kill your engine. Mix the oil and lead-replacer with the fuel in the right proportions, shake and take for example 850ml's of that mixture and add 150ml's of nitromethane. Start the engine on normal fuel and run it till it is completely warmed up. Then switch to the nitromethane mixture.
 
 
Castor oil promotes cooling while Synthetic oil protects engine components from wear
 
 
Beware: You can't kill your engine by stopping the ignition anymore, the nitromethane mixture is self-combustible under pressure. So make sure you can cut the fuel off at any time! or completely stop your air flow!
 
 
side note: Ready to run "nitro" fuel (as intended for rc cars) is a mixture of mostly methanol (practically alcohol), oil (caster, synthetic or both), and typically has around 20% nitromethane added in though that can vary from 10-40% by brand or type. The percentage of oil might range anywhere from 8% to 25% with 15%-20% being the typical amount of oil found in nitro fuel. Up-jetting is a necessity to obtain a stoichiometric balance. A loose rule is an engine must burn twice as much alcohol as gasoline.
 
 
running nitro/ alky fuels can disolve your carb seals, and motor seals
 

Revision as of 15:51, 20 February 2012

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