How do you adjust engine timing on nitro engines?
 

I've been told that you can adjust engine timing on nitro engines.

Can anyone explaine how its done and what the gains are?:cool:

Ignition timing is done by headshims and glowplug.
Lower compression will give a later ignition
colder plug will give a later ignition.
(by the way: less nitro will give a later ignition as well)
later = more rpm but less power
sooner = more power but les rpm and a hotter engine....
Colder plug with higher compression will keep the timing the same but the higher compression will give more power, the colder plug can give an unstable engine....

Porttiming can be changed mechanical.
Higher ports by grinding the ports out
Higher ports can also be made by adding a modified headshim under the edge of the sleeve
lower ports can only be made by taking off some material from under the edge of the sleeve.
Higher exhaust will give more rpm but lower power, lower exhaust will give more power but les rpm. Widening the exhaust will give more rpm without affecting the power.

Take care with positioning of the sleeve that you change the headshims as well.

Changing crankshaft timing can do a lot to get more power or more rpm, it can only be done by grinding,

great post, but way too advanced for me to even try these things:lol:

I can tell you that only 1 tiny change to the crankshaft timing has more result than all those fancy porting and polishing.

I did a little experimenting with this and what I found on my os tz .12 was that when I cut the small grooves in the head button, that gave me a decent increase in bottom end and didn't affect mileage. I tore the motor apart again and did some grinding on the crank opening and lowered the ports on the sleeve. I didn't feel any difference in power and it litterally killed my mileage. I went from about 5.5 min. to about 4.75 min. to a tank. I wasn't too happy about that. So, I put a stock sleeve in it and now it's my back-up motor.

Very interesting stuff.

I asked because we're racing the Kyosho Inferno GT cars in a Spec class and wanted to gain some knowledge about the subject.

Some people have been talking about timing mods to the stock .28 IGT engine. I feel they cars rules shouldn't allow these types of mods because it is intended to be an entry level and level playing field for all.

Thanks for the educational info:cool:

Grooves in the head, must help with a scavenging effect.

I've been racing my IGT car running 16% Werks Racing fuel. I did take out 1 of the 2 factory shims and the car seems to be faster on the lower percentage with a McCoy 9 plug.

I think the Spec class rules for the IGT class should be cool with that since the lower nitro would be easier on the engine.

Sing-grooves, I have tested is and I am amazed...
http://www.somender-singh.com/

My JP Eagle.
http://truggy.nl/e107_plugins/conten...fuelklein7.jpg
http://truggy.nl/e107_plugins/conten...fuelklein6.jpg

It is shown that the combustion is more spread on the piston and did give a better performance. The question is what is legal to modify....

As I told here before the cranktiming can do a lot, but if it is not alowed to modifi the crankshaft and they do inspections you can always alter the cranktiming by modifying the crankcase in the hole under the carburator, they will never inspect that ;)

this is good stuffs thanks for the info...
changing crankshaft timing... what is the effect when grinding the opening and closing and how much to grind??

This is what I normally do with some engines I like to run a bit faster:

http://www.debaanbrekers.com/ftp/cranktuning.JPG

On the closing side just removing some tenths of a mm to close it later and sharpening from the inside so it cuts the flow nicely. This will make the engine better in accelerating and will run a few more rpm's. If you go to far the engine will be very tricky to adjust om the low speed needle and can not have a rich setting. Going to far means you have to take away more than 1 or 2mm on a already fast motor

Also very nice information about 2-stroke, some people say this is the 2-stroke bible.
http://edj.net/2stroke/jennings/

I'll have to give it a go on one of my old motors.

thanks for the info, great stuff:tire::tire:
i'll try it out on my old ZX21... will see how it goes:sneaky:

http://truggy.nl/e107_plugins/conten...fuelklein7.jpg

Roelof, how, and in what directions do you do these grooves? are the 3 small groves towards the exhaust port? and are the other two just placed arbitrarily on the other sides in a uniform manner, or should they be placed at a certain angle/degree after the 3 exhaust port cuts on the button?

cheers

Hi Roelof,

I think the info you are giving here is a bit too general and could lead people to mess up their engines.

First of all, you have to find out the timing of a crank, before you can decide how to modify it.

For example: a Picco .12 based crank opens very late at 40° ABDC and closes at 60° ATDC. On this kind of engine, you'll see much better results to make it open 5-10 degrees earlier, i.e. take material off the other side than in your graph.

Oh, and stay within 220° of total induction, other wise it will be hard to tune and fuel consumption will go throught the roof.

The advise of Mr. Singh was 3 grooves with one above the exhaust port.
This was my first attempt and was to quick with the dremel so I started with a small groove out of line. To make it good I made the right groove and another small one, This part is indeed above the exhaust port.

This is how it is supposed to be:
http://www.euronet.nl/users/tooms/ftp/evo5/evo6.jpg

Using 2 smaller grooves is done more:
http://somender-singh.com/component/...d,384/catid,2/

Just make a few, to many will effect the working of the squishband and does need to compromise the compression.

Oh yes, you are right, thats why only some tenths of a mm, that room is always there in a non-modified engine and does make noticeable changes in the performance.

By the way this is another interesting site:
http://www.first-racing.eu/html/steuerzeiten.html

There was an issue of Extreme Rc where they did dyno tests of the different groove cuts. I don't remember what engine they used to test it and it may differ between engines. Anyway, the highest results they got were when they cut three grooves that were very close together and would line up directly above the center/large intake port on the sleeve. That's what I did with my TZ and like I said, felt a lot more bottom end grunt.

you are refering to the port behind the exhaust port right JetMD?

Wow JSPEED, You got ALOt To LQQK for now.Better get to writen them new rules.:lol:

play nice. what if we find a car you tune i'll drive it but then there will be a rule that you cant tune for this class

Until IFMAR recognizes it, and his sponsor distributes it I don't think he cares...of course this is an assumption and you know what they say about assuming.:) Then there will be a revision to the rule because I assumed something and he pitted under my tent and we were running 17.08546789524% nitroethane instead of methane and.......................

When you are all edjucated on this, just put a few drops of Peroxide in the fuel to start changing things up too:sneaky:
Or if you realy want to get past all the timing and play with a stock engine, you can pinch it around the ports, shave the bottom edge of the piston, rework the case along the intake ports, open up the exhaust hole in the case......swap out the piston with one thats the same size, but is light-weight....Hmmmm the list goes on and on!:tire::ha:

But you know, I run only stock motors any more......I hadn't done work to anything in over a year!........Break them in right and with a good tune, you have what you need to win.

Foolz, what does a larger exhaust port hole do exactly? (hole on the case, not the sleeve) i was thinking of enlarging the hole on my kyosho crf. Would i get more torque or more top end?

cheers

I tuned Someones car , But he thinks I tuned him out of the park. I can't tune for anyone anymore.
Now if you show your butt up to the track, we could work something out.


Yes FOOLZ, What does a larger Case bore do. Inquiring minds wanna know.:D

interesting thread this! i might get my old kyosho gx12 going and try some stuff out. will it run if it has very little compression? i just need to find some way of loading it, as it won't fit in my firestorm.

larger exhaust case bore, brings on more mid and top end. When you have to run a "pot belly" tank in oval, you had to get creative.

Found my gallon of Benzene, and its still fresh. Strips paint on contact. I was given two of these at the track on Sunday, you know to inspect them and make sure there Legal. Found out who the O.E.M. is and they are e-mailing me the "blue prints. Should have them today! I'll tear the new un-run one down tonight and the other one I'll strap to the test bench and we'll see what we are dealing with here. One is from an older car the other is from the Ferrari which I think is supposed to be the latest. :)

i had a go at porting my old kyosho GX-12 engine today. it might not ever run, so i thought i could use a little practice. i noticed the sleeve exhaust port was smaller than the one on the case, so i did my best to even them out (got bored and just did the edges a little bit) and i filed down the connecting rod. i might try some of this on my G3.0 in my firestorm, but we'll see if i can get it out first! (stripped screw GRRRR)

so, how much should i largen the exhaust port by? a little bit? or alot?

Roelf, last head button pic. Did ya get a little tight on the clearance Clarence or did she lean out on you?

I agree, leave this class alone. If they want to go faster move to a different class.

if doing the sleeve port, just a little bit will help....take the upper corners and go straight out, not up in an angle, just out......
If your doing the case, I tried to enlarge it by 2mm....ie: ID 12mm...go to 14mm

No, that was an old NovaMega EVO5 engine with a broken conrod, I have to polish it a bit for new use. The new USE is a cheap p/s set from the Basic collection:
http://www.bb-hardware.com/modules/n...12562&forum=22
I modified the sleeve to the old EVO5 specs to see if it will become a good spare/trainings engine but because the flat piston I think I have to modify the buttonhead as well.

what would happen if i increased the height of one of the ports above the exhaust port so i could make use of a supercharger/turbocharger? i can't see anything against it, but it might just make the engine explode in a ball of fire....

ahem?

Ports above the exhaust ports ????
You have to explain that to me....

I think superchargers have no use on 2 stroke. More pressure will only flow away because when the intake is open also the exhaus is open...

i think he means he wants to make a port above the exhaust so that the exhaust port can be closed and and a intake port still open so more air/fuel can be rammed in by a supercharger or turbo. there may be a possibility of this working if you had a low enough exhaust port and a high enough intake port so part of the time when the exhaust is closed an intake port is still open but the intake port cant be too high. because all the ports need to be sealed before tdc

just my 2.5 cents:nod:

If you have an inlet port higher than the exhaust, think about what happens when the mixture is ignited and the piston starts moving down... what's the first port that opens? Where do the exhaust gases flow? It might not be the brightest idea to have exhaust gasses going back to the inlet port :eek:
There's a good reason why the exhaust port is the highest one of them.

If it will contain high pressure from a turbo/supercharger then it could be an idea but I do not think it will be fuel economic....

All pressure will flow away through the exhaust....

sorry, what i mean is to extend one of the intake ports slightly above the exhaust (maybe a millimeter), so you could have one port open when the exhaust is covered. as 2 stroke engines are from the factory, the exhaust is open when the intake ports are closed.

Try it and you know it.....

I do not think it will work, as example you can rotate the sleeve 180 degrees so the exhaust will become the inlet but from experience I can tell you the engine will not run perfect.

ok, the engines useless anyway, so i might as well try. i wish i hadn't sold that glowplug in it now...