Originally Posted by stefan (Post 4043436)

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.

Originally Posted by Roelof (Post 5214561)

Up to the EVO 2 is listed:
http://www.first-racing.eu/html/steuerzeiten.html

Originally Posted by Pattojnr (Post 5214177)

so your saying the picco crank, has 200 deg of duration ? i actually measured 205 deg on all 3 picco engines i have. one an IDM evo 3, a JL std, and a JL tuned. so if one was to open up the duration further to say 215 like nova based motors, would one see a big difference ? i agree the opening would have to opened up,a s there is about 10 deg difference here from the nova engines. just thinking out aloud at the moment, i am in the process of degreeing all my engines. so there is about 4 more to go . so far the plus 12-3sct has the most duration of all the engines i have checked so far.

Originally Posted by stefan (Post 5216468)

Hmm, I have data of about 15 Picco based .12 engines in my little book, all engines I timed myself and the only Picco based crank that had a different timing was an old Collari engine. All the other have 200 degrees crank timing (40 -60).
Are you sure you are measuring correctly? How do you set the degree wheel to zero?
I measured these engines: IDM EVO3 (4 engines), LRP Spec4(3 engines), LRP Spec3, Picco EVO3 Edo, Mega ZX12 DSII (2 engines), Collari Inotech and an old Picco EVO.

I also have a few Plus 12-3 ST and SCT on record and the crank duration of the stock engines is usually 210 degrees. Is that also what you measured?

Originally Posted by Roelof (Post 4038525)

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,

Originally Posted by mobydickk (Post 5438583)

I believe you have this statement backwards, [B]((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

Less percentage nitro is easier to burn than more nitro.
In your statement above concering more or less RPM, nitro content has nothing to do with top RPM,
the pipe design and pipe length controls top RPM

Hope this helps
moby

Originally Posted by Roelof (Post 4041006)

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 ;)

Originally Posted by 20 SMOKE (Post 5659673)

does any remember seeing a post that had a link to one of the r/c magazines that showed how to mod a engine