ESE's works engine tuner

[MotleyCrue]

Lectron makes a true 90 degree downdraft carb and has for at least a handful of years. I can't recall ever seeing them on their website but they are used on micro/mini sprint applications where people remove their EFI and install downdraft Lectrons. 600cc 4 stroke superbike engines.

[Frits Overmars]

Study's of heat dissipation from the piston crown conclude that 60% to 80 % of the heat from combustion in the piston crown is transferred out through the piston rings.

That may certainly be true for four-stroke engines (unless the piston is cooled from the underside via oil squirting or internally via an oil gallery) and it may also have been true in 1973 when the above-mentioned paper was released, but Jan Thiel found that in the Aprilia engines the transfer streams were the main source of piston cooling.

i didnt know you wrote any books, especially about 4t. now if you could talk jan into writing a book . anyways what do you think about this photo ? probly wouldnt be to difficult to make something similar and plastic welding guns are dirt cheap

That book of mine was not especially about foul-strokes; it was about motorcycle maintenance in general; the cover picture was chosen by the publisher.
Jan and I had plans to write a book a long time ago but a friend in the know calculated that we would have to write it in both english and italian in order to cover the costs, and I did not fancy that; it would have cost me a lot of time that I prefered to use for ongoing projects.
The cooling air duct in your photo seems rather abrupt to me but in any case I too would choose plastic over aluminium.

[AndreasL]

Thanks wobbly,

That was my concern and I'm starting to think that my never ending chase for smaller and smaller idle jets my be caused by a to steep carb angle.
Planing on reducing the inlet length so will have a look to see if it's possible to decrease the tilt some.
Opposite to what I really want...

[G Jones]

Assuming this ducting idea is even worth bothering with. what im talking about is like the photo. right now my rad is like the top example but i want to make it like the bottom one but i was thinking using four walls instead of two like the photo

I'd say effective ducting is one of the best things you can do - if you have a surplus of cooling - you can always "lose" some of it when necessary - can't easily do much to increase cooling without larger rad...
I spent a lot of time on the rad intake when I built our new chassis - also incorporates fresh air intake for the airbox



The fairing forms the top of the duct & ensures no air escapes - if air goes in - it has to go through the rad to get out.
On our first outing the temperature was 90 degrees on the day - I ran 2 x temp gauges - to and from the rad - highest we saw on those was 57 degrees - in the past - we'd more likely be seeing 70 - 75 degrees - way hotter than we wanted.



Definitely recommend the Bradley books too - if you can get hold of them - the 2nd one has the theory put into practice - still not short of technical knowledge though.

[peewee]

nice work jones. i figured having no ducting on the rad was the worst thing i could do. soon as i can ill get some photo of the chassis and the rad location and maybe you smarter guys can give me some ideas what direction to go. my experience of air ducting is alsmot zero

i just noticed you mentioned airbox also. alot of people dont bother and just use open filters attached to the back of the carb but i was thinking of experimenting with a airbox of some kind. ill get photos so you can see what my options are

[teriks]

Inspired of the discussion on ducting of radiators, here something for those still interested in air-cooling, TZ perhaps?
Skip to section two, but spend some time to find the referenced NACA reports later, they are good reading too.

EDIT: Keep in mind that the paper refers to engines with a huge fan in-front, also called a propeller..

[1948rod]

thanks to all for such great info. from my small experience [super charged vw hillclimber] the weir in the float bowl has to be much bigger than the inlet. the inlet flow should be gradual into the bowl [possibly over a chinamans hat] so as to not influence flow to the outlet or fuel pickup to jets. mota. [available from IWT in aust.] has a new program which will give pipe dimensions for your engine in the chosen rev range. i have been building some pipes for speedway karts which seem to be working ok. my dyno is out of action so cant verify the results. have a great new year in 2t land.

[G Jones]

i just noticed you mentioned airbox also. alot of people dont bother and just use open filters attached to the back of the carb but i was thinking of experimenting with a airbox of some kind. ill get photos so you can see what my options are

A few more photos of the airbox

http://maplesigns.co.uk/photogallery...s.php?album=34

not quite complete there - and i still need to make a better seal behind the cylinder - I have run an airbox for a long time - but with this latest one - I spent a lot more time trying to get it to seal - almost impossible to get a complete seal but getting close - apart from the "forced air" from the intake - I'm hoping the isolation of the carbs from hot air from the cylinders will help.
Only had a quick peek at that "Design for optimum cooling efficiency" download - will give it a good read when i have a bit more time...
With the restrictions of the bodywork on the sidecar - I had to get the "feed" duct in where there is space - not ideal - but it does push a lot of air through to the airbox (I'll explain how I found out if i can get past the embarrassment)

[Haufen]

hey guys i been slowly working on a new project and as it is right now the radiator is mounted slightly in front of the center of the chassis and in front of the engine (open chassis with no fairings) but there is no shielding on the radiator to catch any air. i was thinking to use some shielding on all four sides of the rad. maybe i can just use some stiff sheets of plastic or even weld some thin alluminum together to form a box shape that attaches to the rad sides/top/bottom. would it be affective if the walls were only say 6" long forward , and how much inward angle would each wall need to be ? i didnt really want to spend alot of time making something super elaborate but if i could keep it simple and affective it would be nice. i may even use a fan on the back side of the rad but i first want to sort out some kind of rad ducting, assuming this ducting idea is even worth bothering with. what im talking about is like the photo. right now my rad is like the top example but i want to make it like the bottom one but i was thinking using four walls instead of two like the photo

thanks for the picture, peewee.

Can anyone recommend a ratio between the entry area of the duct and the area at the average motorcycle radiator (or airbox)? Or some literature on this subject?

[Lightbulb]

Inspired of the discussion on ducting of radiators, here something for those still interested in air-cooling, TZ perhaps?
Skip to section two, but spend some time to find the referenced NACA reports later, they are good reading too.

EDIT: Keep in mind that the paper refers to engines with a huge fan in-front, also called a propeller..

Thanks, that is an interesting article . Interesting about the paint thickness and the heat dissipating ability. I saw some tests done with anodising aluminium heat sinks and painted. The anodised was worse than the plain ali. It acts like an insulator.
Air ducting is interesting for sure and not always what I thought it would be. I saw a model with an airgap of 0.75mm around the tuned pipe at it's biggest diameter. I thought it was no where near enough, but the designer said the calculated area was still 60% larger than the air inlet area.
Neil

[teriks]

Only had a quick peek at that "Design for optimum cooling efficiency" download - will give it a good read when i have a bit more time...

Wont be of much use for your water cooled stuff anyway, so don't waste too much time there.

Thanks, that is an interesting article . Interesting about the paint thickness and the heat dissipating ability. I saw some tests done with anodising aluminium heat sinks and painted. The anodised was worse than the plain ali. It acts like an insulator.
Air ducting is interesting for sure and not always what I thought it would be. I saw a model with an airgap of 0.75mm around the tuned pipe at it's biggest diameter. I thought it was no where near enough, but the designer said the calculated area was still 60% larger than the air inlet area.
Neil

Even though the area was larger such a section is probably a restriction anyway, due to the huge amount of wall in that narrow flow area.
Perhaps Frits could write a word or two on that? I suspect he don't have to find the proper literature to learn how to perform a calculation like I would have to

[husaberg]

The issue you are up against is that the traditional layout dictates that the idle jet ( and its supply well ) are in front of the slide ( engine side ).
The Lectron has no idle circuit at all, with all the fuel entering the venturi up the main ( emulsion tube - but not ) needle well.
With this old school setup the fuel level for this circuit becomes progressively closer to the exit hole in the floor of the venturi, as the carb is tipped upward.
If you go too high, fuel will simply run straight up the well and dribble into the venturi in front of the slide, with no air flow needed.
To make matters worse this fuel level rises in the front side of the bowl under brakes, again fuel spews out the idle circuit without any vacuum.
Best example of this is a TZ350, where plenty of power gain is to be had by shaving off the rubber manifold face to straighten out the intake by
re angling up the old VM38mm carbs.
Go greater than about 5* and its impossible to stop the flooding under brakes, no matter how low you drop the fuel level by shutting off the float valves early.
The only way I know to get around this is to use the OEM carbs made by Keihin on things like NSR400 etc where the bowl is kept horizontal,and the venturi is angled.
People on here can tell you several other models that had the downdraft carbs from the factory - for exactly the reasons above.
The other example is an FCR as was designed for the heavily downdrafted ports on big 4T engines.
There are quite a few sizes availble in the OEM carbs used by Honda with a D shaped venturi, and the FCR is made in plenty of sizes as well, but jets for this
are a nightmare to size for a 2T.
Dellorto have made some carbs with the idle jet ( and its fuel well ) on the intake trumpet side , with drillings down the side of the emulsion tube and around in front
of the slide.They usually have a fuel adjuster screw on the side, not an idle air screw.
These could easily be modified to run seriously downdraft, as the greater the angle the lower the fuel gets in relation to the actual idle jet height.

I thought you might like this Wayne,
A pumper carb radio control mixture set up a perfect xmas present for the tuner that has everything...........
Note the highspeed lean out limiting.
http://eknclassic.com/viewtopic.php?...9957e226d8aeda

[peewee]

A few more photos of the airbox

http://maplesigns.co.uk/photogallery...s.php?album=34

not quite complete there - and i still need to make a better seal behind the cylinder - I have run an airbox for a long time - but with this latest one - I spent a lot more time trying to get it to seal - almost impossible to get a complete seal but getting close - apart from the "forced air" from the intake - I'm hoping the isolation of the carbs from hot air from the cylinders will help.
Only had a quick peek at that "Design for optimum cooling efficiency" download - will give it a good read when i have a bit more time...
With the restrictions of the bodywork on the sidecar - I had to get the "feed" duct in where there is space - not ideal - but it does push a lot of air through to the airbox (I'll explain how I found out if i can get past the embarrassment)

did you do prior calculations for the airbox size, like 10x engine capacity etc, or did you just make it as big as the available chassis space would allow ? i heard theres some theory on how big the box should be but i cant remember the details

[Frits Overmars]

That paper on air cooling is great, as usual with NACA publications. But I stumbled upon one paragraph that cries for some comment:

You only need to get rid of heat that stays behind. Insulating coatings in the combustion chamber will stop heat transfer to
the engine...I remember reading somewhere else that a ceramic coating of the combustion chamber would have a dramatic effect on
lowering heat transfer to the cylinder head, and greatly improve efficiency of the engine cooling system.

"You only need to get rid of the heat that stays behind". Yeah, and then you only need to get rid of the massive detonation caused by the high surface temperatures inside the combustion chamber.
Next point: a ceramic coating would in no way improve the efficiency of the cooling system; it would merely reduce the amount of heat that has to be moved away.

Air ducting is interesting for sure and not always what I thought it would be. I saw a model with an airgap of 0.75mm around the tuned pipe at it's biggest diameter. I thought it was no where near enough, but the designer said the calculated area was still 60% larger than the air inlet area.

Even though the area was larger such a section is probably a restriction anyway, due to the huge amount of wall in that narrow flow area. Perhaps Frits could write a word or two on that? I suspect he don't have to find the proper literature to learn how to perform a calculation like I would have to

You are dead right about the unfavorable ratio between the cross flow area and the wall surface, Teriks. But finding the literature is not the problem.
The problem is knowing how well the air flow can attach to this surface. And that depends on factors like surface roughness, flow velocity, static pressure in the system and the amount of turbulence with which the air enters the system. In short: the problem is insufficient information (as usual).

did you do prior calculations for the airbox size, like 10x engine capacity etc, or did you just make it as big as the available chassis space would allow ? i heard theres some theory on how big the box should be but i cant remember the details

The details are not too difficult Peewee. Some dedicated computer programs can calculate the ideal set of circumstances for a nice Helmholtz resonance,
but in general it comes down to this: if you make it as big as the available space allows, it's almost big enough.

[G Jones]

I did spend (way too much) time reading on the subject - but as it turns out - you can only fit what there is available space for...
I picked up a barely used rad from a guy that had some bad overheating with it - whoever built it had the inlet in the top left & outlet in the bottom left side - so i figured it was short circuiting without actually cooling - I blanked off the outlet & made a new header for it making it double pass (I hope) so forcing all coolant to go down the one half & back up the other to get maximum cooling.
I then tried to concentrate on getting the best seal on the entry - whatever I'd read on entry size didn't much matter - just used what I'd got - and basing my thinking on what we had on the old bike (which worked well enough)
I think you can maybe over think a lot of this (and lots of other stuff too) a lot of the time you can look at something for a while & it's obvious whether it will work or not - main thing I think is to have a duct that has the entry well sealed - if you are scooping air - you don't want it escaping before it's gone through the rad.
All of this took a lot longer than I'd have liked - the original fairing design didn't have the space or the entry where i needed it - so had to make a new fairing - involved a lot of Glass fibre work - making new molds etc but worth the effort - I now have the rad entry I want - and also gives me a lot more space to fit different pipes - there was zero space for any different pipes with the old fairing design.

Just going back to that rad - the guy that had it made - put the inlet / outlet where it was most convenient for the rest of the bike - wrong move I'm afraid - what he should have done is think a bit harder - first - how does this system work - and next - how to adjust the rest of the bike to fall in with that - you can't let not important stuff dictate important stuff !

did you do prior calculations for the airbox size, like 10x engine capacity etc, or did you just make it as big as the available chassis space would allow ? i heard theres some theory on how big the box should be but i cant remember the details

Frits has posted while I was thinking - just shows how much quicker the great mind works ! - I did read up on the subject - whatever I could find - but still comes down to available space - so - the outside of the airbox was made off the inside of the engine cover / seat - couldn't get much more space than that !