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Old 03-21-2006, 07:48 PM   #1066
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Quote:
Originally Posted by deviltires
does anyone know where i can get ceramic bearing for the os tz 3 port front and back
If youre in the US......try-
www.acerracing.com
They do ceramic bearings, but i`m not sure whether theyre for engines or not.
Cheers
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Old 03-21-2006, 09:28 PM   #1067
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Originally Posted by vti-chris
I know when a motor is loading up.
I come from a WOT run to idle and the engine sounds like it's TOO lean on the low end.It stays this way for 10sec and then loads up.Sometimes i just pass my finger from the stinger just to push some more fuel in to load it up faster.
If i richen some it's OK but it still dies after 8-10 sec of idling or when i go from idle to WOT.
I finished a 40min race with this engine and temps ended the race at around 250F.Which i don't think it's high when the engine has "problems".
I don't know what else to do.
Only the carb may be the reason which might need sealing...!!
Also the runtimes of this engine are less than 5min.I had to stop every 4.5min in the race to refill.Others on this site say that it goes up to 6min.
I had to add a large filter and 12inch of fuel line to increase the runtimes close to 5min.
I hardly finish the qualifying which are 5mins each.
Well somthing is going wrong with your tuning, air leaking or fuel. I had almost the same conditions on my RB v12 and it was a lean HSN which caused my LSN to need to be too rich. If your track is small and technical you won't overheat because you spend more time on the low end and only short bursts on the high end. I had the same attitude you did. I refused to beleive that I could have the HSN that too lean. I had gradually adjusted the needles too far. Why don't you give it a try just to rule it out completely before you start tearing down the engine looking for an air leak. I'm not a noob either. Been running nitro for almost 10 years and I still made the mistake. Cost me many races because I kept trying other things, but the engine kept doing the same thing. Now everything is back to normal and my motor runs cool, has power and gets much better mileage too.
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Old 03-21-2006, 11:38 PM   #1068
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Quote:
Originally Posted by Rapid Roy
Well somthing is going wrong with your tuning, air leaking or fuel. I had almost the same conditions on my RB v12 and it was a lean HSN which caused my LSN to need to be too rich. If your track is small and technical you won't overheat because you spend more time on the low end and only short bursts on the high end. I had the same attitude you did. I refused to beleive that I could have the HSN that too lean. I had gradually adjusted the needles too far. Why don't you give it a try just to rule it out completely before you start tearing down the engine looking for an air leak. I'm not a noob either. Been running nitro for almost 10 years and I still made the mistake. Cost me many races because I kept trying other things, but the engine kept doing the same thing. Now everything is back to normal and my motor runs cool, has power and gets much better mileage too.
OK,i'll do that.
I'll try to get my LS needle as close to flash with the carb and set the HSN richer and see how it goes.
If this is the case then .12 engines and .21 ARE NOT the same!!!!
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Old 03-22-2006, 12:42 PM   #1069
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What do the restrictors do that come with the engine?? As for as the impact on performance.
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Old 03-23-2006, 10:06 AM   #1070
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deviltires

bocabearings.com has all kinds of ceramic bearings


osiris, no restrictor gives your engine higher acceleration and consumption. it even sounds louder!
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Old 03-23-2006, 11:38 AM   #1071
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Quote:
Originally Posted by Osiris 75
What do the restrictors do that come with the engine?? As for as the impact on performance.
VENTURIS

Internal combustion engines require three things to produce power - fuel, oxygen and heat, and they need them in specific ratios. Running in situations in which the air is denser (contains more of oxygen) an engine produces power with ease. In situations in which the air is less denser (less available oxygen), an engine will not be able to burn as much fuel as it does at higher density air situations. Less fuel means less power, and that means slower speeds.

What can you do to minimize the effects of less denser air ? Compression creates power, and when the air is less dense, there is less fuel/air mixture available to compress.
To recover some of the lost compression, you can use a fuel containing a higher percentage of nitromethane, or reduce engine-head clearance to increase the compression ratio.

To compensate for less density air, you need to adjust your needle valve to a leaner setting to maintain the proper fuel/air ratio. The opposite is true for higher density situations. The idea is to maintain the optimum ratio of fuel and oxygen by adjusting the fuel volume to compensate for ambient air pressure.

Now, if you have the appropiate compression, and still need some more fine tuning for lower density situations, that is where the different sized Venturis come in handy.

A venturi such as a model engine carburetor's works on the vacuum principle. As air rushes through the venturi, it accelerates and creates a vacuum at the spraybar. This vacuum draws fuel from the spraybar and fills the crankcase with a mixture of air and atomized fuel; at very low density situations, less air accelerates through the venturi and past the spraybar. This reduces the vacuum at the spraybar, so less fuel is drawn through it, and the mixture becomes too lean.

There is a way to compensate for this: Switch to a venturi with a smaller area.

When you have a smaller venturi area, the airflow velocity through the venturi is increased. This also increases the vacuum at the spraybar, which, in turn, draws more fuel.

Obviously, you have to experiment to learn which combination size of Venturi best suits your engine and ambient situation, and you have to take into account the rules and regulatios of your association or club. IFMAR / ROAR staes 5.5mm for .12 engines, and EFRA states 5.4mm as maximum dia. of venturi at the slide side of carb.

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Old 03-23-2006, 11:42 AM   #1072
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I'm using TZ 5 port. What head clearance should I do ?

Do I add shims to increase the head clearance?

How many mm ?
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Old 03-23-2006, 11:56 AM   #1073
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Quote:
Originally Posted by Secret_weapon
I'm using TZ 5 port. What head clearance should I do ?

Do I add shims to increase the head clearance?

How many mm ?
Engine Shim Tuning By Dennis Richey

Experience dictates that just by lowering the head (more compression) you gain more power especially in lower rpm range, idle quality can suffer, but the engine also runs cooler . Also, that a higher head (less compression) will increase top rpm speed on bigger tracks.

A decrease in head shims (an increase in compression ratio) will increase torque because as the compression ratio goes higher, the actual ignition timing occurs sooner. However there is a point of diminishing returns where detonation occurs or engine temps can soar, and if this happens a colder plug can help.

A colder plug will also increase torque, except in the instance of a colder plug the ignition is slowed until a greater point of compression build occurs.
When you increase head shims (a decrease in compression), top end is enhanced as the ignition timing is retarded and occurs later. Generally a hotter plug is needed to advance the ignition cycle so that timing does not occur to late in the cycle, but at this point you end up over leaning the engine to get it to rev properly and the engine life will suffer dramatically.

On a .12 engine we would only advise going 0.10mm over or under 0.46mm, so that is 0.36mm or 0.56mm of total head clearance at sea level, depending on Nitro contents of fuel.
Generally on a .12 engine 0.10mm will change the compression ratio about 3/4 to 1 point.

We should also state that the comments with regards to plugs and head shimming are when both are used together. Used alone a hotter plug will rev harder and a colder plug will make more torque.

One last comment. never assume that the head shim that is on the engine is the actual head clearance. When in doubt measure the head button register and the piston to the top of the liner at top dead center and subtract, to determine proper shim. This is the only way to really know.

You can safely use 30% Nitro on the stock head clearance. For lower Nitro contents reduce shims. For higher Nitro contents add shims.

About plug fatigue: Plug fatigue can occur under high sustained RPM's, and this is where the plug stays shiny and the wire just fractures for no reason. When this happens it is usually not a carb. tuning or head clearance problem. If you see the wire start to pull out of the hole this means that the engine is scavenging really hard and when this occurs the engine is making serious power. Try a colder plug.

There you have it.

AFM
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Old 03-23-2006, 11:59 AM   #1074
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Thanks alot !! It really helped.
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Old 03-23-2006, 12:37 PM   #1075
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afm - that is some great info, thanks.

I have two questions though. How exactly do you check the actual head clearance? And what numbers do you subtract?

Sorry for the questions, I just want to make sure that I get it right. Thanks
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Old 03-23-2006, 02:22 PM   #1076
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Quote:
Originally Posted by RobertM
afm - that is some great info, thanks.

I have two questions though. How exactly do you check the actual head clearance? And what numbers do you subtract?

Sorry for the questions, I just want to make sure that I get it right. Thanks
No problem:

Put piston at TDC, measure the distance from top of piston to edge of sleeve, take note of measurement.

Take shims from head button and measure the distance from edge of head that goes into sleeve to the recess where shims rest, take note of measurement.

tHen subtract bothe measurements, and that is your bare head clearance. now add shims according to actual head clearance you want, taking into account sugestions of article.

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Old 03-24-2006, 10:34 AM   #1077
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Awesome, thanks AFM.
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Old 03-24-2006, 10:40 AM   #1078
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Excuse me, I'm not so good with the language.


What do you exactly mean by TDC and the engine sleave stand for (connecting rod ?)
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Old 03-24-2006, 12:10 PM   #1079
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TDC = top dead center

when the piston is at its highest point in its stoke
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Old 03-24-2006, 04:26 PM   #1080
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Quote:
Originally Posted by Secret_weapon
Excuse me, I'm not so good with the language.


What do you exactly mean by TDC and the engine sleave stand for (connecting rod ?)
TDC = Top Dead Center (piston at it's highest point)

Sleeve = liner = skirt = camiseta (material in which the piston runs up and down)

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