i have built balsa guillows fw 190 42 CM wing span. i read many treads on motor selection but still confused. i saw some motor but not sure about there KV and X gram trust. i saw motor with high KV are cheap. also battery what is mah. is more mah means more flight time. one thing i know high Watts mean it will consume more power.

Well the easiest way is.... go to Hobby king page and enter a webchat with a "product Specialist" of HK.  He will need the span and the weight of your model to tell you the kind of motor, ESC (BEC), Battery and Prop arrangement for your model.  He is bang on and most cases gives a slightly over powered solution. 
Second is Ask an expert here by name... you may request anyone out here..
Third... if you take my advice (this is what I do)... GO to HK site... look for a motor which gives s thrust which will suite your model.. If your completed model is likely to weigh about one Kg.... you can safely bet on a motor which has a thrust of anywhere from 700 gms to 1 Kg..... In the specifications of motors they have given the Thrust, ESC required (go for a 10-20% higher rating of the ESC), Battery required and in many cases prop required... in my opinion you can safely go for an NTM 32-38 motor with a 50 Amp ECS and a 3 cell 2200 mAh Lipo for this model.

Search for a 24 gram motor like the HXT Blue Wonder. Most people use these motors while converting Guillows to electrics.

Shobhit, the NTM 3228 with 50 A ESC does not seem to be a valid number. In any case with a 50 A ESC you are talking about more than 400W! This is a Guillows model. It will need a tiny little motor, ESC and battery

What VC says is more like the suitable motor.

Looking at the model, the weight (without motor/Battery/ESC) would be around 200 Gms or less.

i saw some motors on RCB, what is KV rating. is higher is good or lower.

Read up about Electric Power on this forum

Dear Sanjay.... well... VC is a very experienced aeromodeller and I am sure I too can learn a lot from him.... I am also sure he would be absolutely right... I only gave the details for a model weighing about 1 Kg.  I am using the NTM 35-30A for the model with a recommended EBS...... https://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=16234.  The model flies and zooms like a beauty

A 3530 for a 1 Kg model is fine. No motor series of 3228 by NTM. A Guillows model of 42 cm span will weigh < 200 grams. Better to check before giving advice to a newbie IMHO

Shobhit Sir, I mean this with all humility - I don't posses a small percentage of your aeromodelling knowledge. Let's not argue about this fact at least. My close friends on this forum are fully aware of that. My strengths lie in building, designing (water craft) and detailing. As far as flying is concerned, I still have a lot to learn.

Today i kept quiet on this topic the whole day.

Just now i wrote a detailed post, but deleted it due to potential for being misunderstood.

@abhishekfast
Please post a few pictures, and also the weight without any electronics.
BTW there are lots of posts on the net about Guillows FW-190 conversion to electric.

@shobhit17
While you suggestions may be for a 1 kg model, this airframe w/o electronics may be only 100 gms or less. The wing area is probably less than half a sqft.

Dear Sanjay,
You too may better check my post on the issue of motor before you point out anything... we are all here to help propogate this hobby and not discourage anyone... the third point in my post chearly states the following "Third... if you take my advice (this is what I do)... GO to HK site... look for a motor which gives s thrust which will suite your model.. If your completed model is likely to weigh about one Kg.... you can safely bet on a motor which has a thrust of anywhere from 700 gms to 1 Kg..... In the specifications of motors they have given the Thrust, ESC required (go for a 10-20% higher rating of the ESC), Battery required and in many cases prop required... in my opinion you can safely go for an NTM 32-38 motor with a 50 Amp ECS and a 3 cell 2200 mAh Lipo for this model."  yes the NTM motor number was written incorrect and I have corrected it in my post....  
Lets put everything to rest and not keep bickering about our self and our issues.... There are just a few who are masters of this hobby here and the rest are still learning....
VC... yes I do admire him for whatever he is... he been a great support to me in helping me decide whatever I wished to know or understand... he always had time to listen to my questions and answer them.... put together with my experience I could understand him and put them to good use...
Regards VC
Thanks everyone

Iyer Sir,

If you ain't misunderstood (sometimes), you ain't LIVING (most of the time).

How's that for an original?

Shobhit Boss, just chill. Rai Saheb can never mean any harm to anyone (other than the wild boars that he used to hunt), let's not get into these stupid tangles. Friends don't admire each other in public, they just quietly respect each other - without realising it themselves.

Damn! I am brilliantly articulate tonight!

Cheers Guys! Where's Ol' man Johnnie when I need him. Prolly Walked off somewhere...........

Keep walking, I'll catch up...............

Thanks VC.... Well... need a drink with you now I guess.... Ha ha ha ..... Happy Flying

i will post pics. will weight it and let you know.