Air density, a secret tuning factor

Air density is a computation mainly dependent on the temperature, barometric pressure, and the humidity of a volume of air.

Temperature in the USA is generally measured in degrees Fahrenheit, barometric pressure in inches of Mercury (inHg), and humidity in percent of Relative Humidity.

You can relate to how these factors effect the density of the atmosphere by using a balloon to simulate the earth’s atmosphere. When a balloon is filled with air and placed into a refrigerator it begins to shrink, this is due to the drop in temperature of the air inside the balloon. As the air cools it releases energy and slows down,because the air molecules are not bouncing off each other as much, they remain closer together and more of them will now fit in a smaller area. The opposite will occur if the balloon is heated.

The effect of humidity is a little more complicated. A change of humidity in the atmosphere is caused by a change in the amount of water vapor mixed in with the common gases already present in the air. As more water vapor is put into the air is displaces these gases. The water vapor is also less dense (weights less) than the gases in the air. When we take air that is at a set temperature and pressure and start introducing increased amounts of humidity we begin to cause the overall density of the air to decrease. Therefore, the density of the air is the greatest when there is no humidity.

Changes in temperature, pressure, and humidity can have different amounts of effect on the associated change in air density. A change in temperature or pressure causes a proportional change in density. In other words, a 1% change in temperature causes a 1% change in density. Again, the effect of humidity is more complicated, because the effect of humidity on density is also dependent on the temperature. A 50% increase of humidity when the air temperature is 70f degrees may cause a 1% decrease in total air density, but a 50% increase of humidify when the air temperature is 90f degrees may cause a 2% decrease in total air density. This effect is due to the fact that it takes lot more water to cause 50% relative humidity at a 90 degree temperature than it does at 70f degrees. The humidity must also be considered in that it makes up some of the density of the air, but it has no value being there.

The air in the earth’s atmosphere is made of various gases and water vapor. Neglecting the effect of pollution there normally is 20.9% of oxygen, 75% of Nitrogen, Carbon and very small amounts of some other gases. Oxygen is the most important gas in the atmosphere as far as an internal combustion engine is concerned. This is due to the fact that the oxygen is used to burn the fuel placed in the chambers of the engine. When more oxygen can be placed in the chamber it allows one to also place more fuel along with it and therefore create more power. The air density relates to this because when the air density increases the amount of the combined gases and water now fit into a smaller area, this includes oxygen. If the air is denser than there is more of it therefore more amount of oxygen will be taken into the engine.

The term commonly heard among racers is “density altitude”. Density altitude is the density expressed if feet instead of grams per cubic centimeter. It’s a lot easier to relate a change of density in a couple hundred feet rather than a change of 2.534 g/cm^3. The use of density altitude is taken from the U.S. standard atmosphere table. This table relates the density of an average day at sea level (59 degrees, 29.92 inHg) and how it changes at different elevations in the atmosphere. As one climbs in altitude the density falls off at a predetermined exponential rate.

In conclusion I highly recommend either an Air Density Gauge or a Altimeter as tools to be used for adjusting your Fuel Curve and Ignition Timing. I firmly believe that these items are essential for tuning at the Race Track

How to repair cracked engine covers

How to repair cracked engine covers.

First you remove the cover from the bike ofcourse, and then you degrease it very thoroughly.

As with all cracks in every material you need to drill small holes at the end of the cracks. Do not drill exactly at the point where the visible crack stops because underneath the surface the crack already had gone further. So plot an imaginative line in the extent of the crack and drill the hole along that line a few millimeters from the end of the visible crack.

I used a Dremel tool, but you can use a normal drill with a grinding stone (though due to it’s weight it’s harder to control) to dig a trench along the crack.
Dig as deep until you’re almost coming trough on the other side. This will make it very easy to fill it with epoxy.

Clean the other (in)side using emery paper or a Dremel tool to make sure the epoxy will attach itself well.

Then you clean and degrease the cover very thoroughly and warm it up by laying it on a heat source like a radiator or geyser.

While the case is heating up we prepare the metal epoxy. I use “Bison” metal epoxy but I guess any well known brand metal epoxy will do just fine. Just follow the instructions that came with it carefully and be sure to mix it very thoroughly. As with all two-component substances mixing it thoroughly is most important, so don’t rush it!

When the epoxy is ready apply it to the cover. Make sure you push the cracks full of epoxy so no air bubbles are left in them. If you dug them out deep enough epoxy will come out on the others side.
Your cover will have a very large flat spot so be sure to apply enough material, better too much than too little.
Apply some epoxy to the inside too but it hasn’t have to be much, just enough to make it smooth.

Then you leave it to dry on a heat source, at least for 12h untill the epoxy has become very hard. It hasn’t got the same mechanical properties as aluminium though, more like a hard plastic.

Now you can file/sand it into shape and spray paint the cover (you didn’t intend to polish it, now would ya? ūüėČ

Well, there you are… a good as new engine cover, ready to last untill the next crash!

1. Drill holes at the end of the cracks and dig the cracks out

2. Clean the inside of the cracks

3. Warm up the cover

4. Prepare the epoxy

5. Apply epoxy liberally

6. Epoxy on the inside

7. Let it dry for at least 12 hours.

Oldskool Oldskool, the road less travelled

614982_10151073061812733_377962059_oJohn Oliver (AKA Yoshi-Johnny, AKA YJ) is a long time OSS member and¬†Pops Yoshimura enthusiast. John is a professional bike mechanic and many will remember his iconic take on the classic Wes Cooley GS 1000. Ten years ago, when John first rolled up at an OSS gathering on his GS, for me and many others,¬† at the time, his bike fully embodied the true¬† spirit of OSS. An air-cooled 8 valve GS1000 engine and classic Wes Cooley paint job but running on modern 17″ wheels,¬† sporting a mono shock conversion¬† and a set of gold anodised upside down GSXR forks. Evolution of the species. John’s love for Suzuki’s 8 valved air-cooled GS1000 engine has never faded. We asked John to tell us a little about his dream engine build and here is what he told us.

KM

Oldskool Oldskool, the road less travelled. John Oliver

It’s always been a dream to own a full blown Yoshimura motor but I don’t earn enough to just go out and buy one so I am gonna have to do it the only way I know how, a p.p.p.piece from here and a p.p.p.p.iece from there. So, I am in the process of getting together for the race bike I am going to prep for myself to go racing instead of others!

Engine

Yoshi motorI got hold of an old NCK drag motor a few years ago and it has a pretty good crank and gearbox in it. Crank has Katana rods and along with being welded it has straight cut primary drive gear, along with a matched one for the clutch basket. Cases have been lightened and dipped at Ribble Technologies in Preston. So the bottom end is as good as my budget will allow for the moment. I do need a new clutch before it turns a wheel in anger and this will involve having the straight cut fitted.  Originally the NCK engine was a 1420 drag engine but on the road or track that sort of capacity would generate too much heat and quickly cook itself.

yoshi pistonsGraeme Crosby in conversation said he preferred the power and reliability of the 998cc motor as it gave enough power and was reliable, Pops and he discovered the bigger the capacity went up, the less reliable and problematic it all became. Craig Smith, my good mate in Australia who has been on here for years is a major inspiration for the build as his black “skunk” race bike is still one of the outstanding bikes on the site. He raced it to good effect in NZ and didn’t suffer with reliability issues. He went bigger and bust his crank!His motor punted out 135 rwhp and that is my aim with this… I won’t be gutted if it doesn’t get there, but it would be nice if it’s something like.

So the pistons are custom made 1100cc Wisecos and are one of only 3 sets made this particular profile I think. All the gaskets and seals will be replaced with standard (where necessary) or Cometic (where it’s ok to cheat!) and special ones (base and head).

Head

bladeThe cam chain was a weak spot on Yoshimuras race engines and the team did all sorts to try and reduce the extreme wear during races, extra jockey wheels, longer cam chain, shorter tensioner blade, POLISHED cam chain links and manual tensioner were all employed in the hunt for reliability. Most of this development actually went into the first GSXR engine. So all the above mods will be done to this engine.I have had a jockey wheel and plate made but Roger Upperton does a better version which is more like the GSXR version than the one I have. The extra jockey wheel at the back of tthe head is the reason the tensioner blade is shortened.

 

Yoshi headThe head has been checked over and overhauled from scratch. Bigger valves, seats cut to match and a tidy port job will make the gas go in quick and hopefully make it work right.

camsValvesCams are very lumpy custom profile ones from New Zealand and require cut aways for them to turn in the head! Shims will be under bucket care of Kibblewhite, buckets, retainers (titanium) and collars. Dialled in cams will be easier with Rogers version of the jockey wheel than the Smithy version. I may put a twin plug set up in as well when I actually get to the build

Carbs
Carbs will be Mikuni VM33s and are getting quite scarce, these are about as big as you should be going on a bored out GS1000 engine, anything bigger just makes them bog down when you crack the throttle open.

Jockey wheel

 

 

 

Ignition
Ignition will be taken care of by Boyer Brandsen mini digital set up until I get a self generating system organized…

Speed is all a question of money…I wanna go fast but my wallet says whoaaah.

YJ

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