choisan

iTrader: (6)

how about the .21? need to shim .1 to run 25%? the other guy was running in the team machine in my city.

am

Just a fyi.

I used to stop my offroad engies by plugging the exhaust. I used alot of glowplugs. I have now stopped doing it, stopping my engines on the flywheel insted. My glowplugs now last alot longer :-)

beebone

How about the head clearance for .21 engine?
I've found out the 2 x 0.1mm and the under sleeve shim, the total head clearance around 0.58~0.62, there is lack of low end power.

dj apolaro

I have found that if you are running a good fuel, you can run .5 total clearance. Leave the shim under the sleeve and play with the shims under the button till you get the total clearance of .5

This will help with the low end torque.

DJ Apolaro

beebone

Thanks! That's what I though about

kyosho malaysia

but will lost some top end

dj apolaro

That is correct. But I can say with these motors, they have good top end and you will not notice much of a difference when you change the shim on the top. Unless you run on a very large track.

DJ Apolaro

kyosho malaysia

beebone

Interesting thing was found. I did the soldiering test the head clearance is about 0.53, good figure . But the engine is lack of power, only the punchy feeling i can feel when exit.the corner, then no power at all. It was about 120C.

When I take away the shim under sleeve, and add 0.1 head shim to maintain the head clearance in 0.5. The overall power is back!!!! About 110C. But the punchy low end power is lower then with the under sleeve shim.

So, I know the under shim makes the port higher, but what does the higher port mean?
I wish to put the under.shim back to retrieve more low end power, but I don't know how to tune it to get back the mid and top end power. Any clue ?thx

kyosho malaysia

the under shim is to raise the port to get faster discharge,at the same time intake also react the same,it will give you higher rpm but have to compromise with some fuel consumption and torque

beebone

Well, if the under shim acts as raising the charge and discharge actions, I understand the fuel consumption will be higher. So, if the charging action faster, does it mean the needles need a bit richer to feed enough fuel?

afm

About Port Timing

Of course you know that when you place the undershim you will get a higher exhaust port, which will yield more rpm’s, so more top end, and inversely lower exhaust will yield less rpm’s, so more low end, but take into account that with the undershim you also move the transfer ports timing higher.

First of all we know that difference between transfer and exhaust duration needs to be at least 40 degrees so the tuned pipe works properly, then second thing you have to take to consideration is fuel consumption, higher transfer = more fuel will go, and some of it will not burn, then fuel consumption will go down.

In my opinion from what I’ve learned on RC cars motors is that .12 size transfer needs to be around 116-122 degrees. Everything over is going to hurt run time, everything lower will work against performance.

Just remember whatever you do, keep difference between transfer and exhaust 40 degrees at least.

Induction (crank opening) timing works like this: earlier opening = more low end . Later closing = more top end.
Also keep in mind that the greatest boost in power is gained by increasing total induction duration, and increasing inner diameter of passage in crankshaft.
With respect to head clearance:
Small chamber = Advanced ignition = Colder plug = More torque
Bigger chamber = Retarded ignition = Hotter plug = More top end
Plugs alone, with same chamber will give you: Hot plug = more top end. Cold Plug = more low end

So there is no special formula, it’s just more up to trials. You see on our RC cars application specially on .12 motors we need some torque, some RPM, and fuel mileage.

Hope this helps
AFM

kyosho malaysia

as i know for small track we use hotter plug to gain more torque,maybe i'm wrong

kyosho malaysia

usually i leaner LSN,richer the HSN compare to standard engine setting but i do mofidied the piston,crankshaft timing,crankcase,sleeve and button.

beebone

I tried OS RP6, the power is back. Timing problem.