[NSRCA-discussion] YS 120 NC/SC prop recommendation

[Troy A. Newman]

15-10 is an excellent prop on the 120SC, if its a strong one you can with the 15-11

Of special note the 120SC likes Nitro. It is a fairly high compression engine and can be a little finicky. It was the strongest of the 120's In fact I had one that gave the 140FZ a run for the money.

Being this soupped up highly tuned 120...the extra nitro broadens the mixture settings. The other thing it does is higher nitro require richer settings to get the mixture correct and as a result they will run a bit cooler and better. More fuel flow means more oil flow and better cooling also.

I strongly recommend the Cool Power 30% heli fuel.

By the way, on the 120SC because its more a higher compression soupped up version, don't run it out of fuel. If you are flying and too long and the engine runs dry it can backfire and can cause damage. Its never a good idea to run any of the pattern engines 2 or 4 stroke out of fuel, however the 120SC, 120AC, and the 140DZ tend to be a little brutal when this happens. Try to run the 120SC at the higher end of rpms. I would say the goal rpm for that engine would try to be up at 8600-8800 maybe as high as 9000. On the 15" props it will make noise with ease in most cases(read exhaust systems)

The 120SC is an awesome engine. Like I said it was the king the of the 120's. There were some folks that had issues with them, but my experience was always good with the SC. There were some piston of the month changes to the 120SC. Namely they had a dished piston, and some magnesium pistons. The goals behind these were to get more power out of the 120 case. Back then the FAI rules had not changed to allow larger than 120 displacement. So YS was trying to lighten the piston, and get the engine making max power from the little box. At the time there were a few models that were getting bigger than the 2 meter box as the 2m box didn't exist. No size limit just the engine limit and the weight limit existed at the time. On the piston front just stick any ole 120 piston in it....the 120SC piston could be a little fragile if run lean (meaning running it out of fuel). The original 120SF piston was bullet proof and works in the 120SC. The dished and designer pistons are really able to change the behavior of the engine. I have played with this "super" or the "hyper" pistons on the current 160DZ and 170DZ engines. Its cool how changing the piston by putting a dished top and closing off the bottom of the piston can change the way the engine reacts to certain prop loads, or it will change the noise. Some of the things they can do make more power and some of the pistons make it run super smooth and quiet. Yamada doesn't do the testing in production like they once did with the pistons. I have been fortunate to try some of the super cool, "hyper" pistons they have played with on the DZ's. I wish I had the knowledge back then that I have now. Some of the smallest changes in a piston can really totally change the way an engine performs. Its kinda neat. I remember the need was for more power more power back then and now I know which piston designs would have done it better. 

Any of the current exhaust systems will work very well on the engine. Even the short hatori 821 pipes and the NMP header will work excellent on that engine.

I have a couple of 120AC's that we carved up the heads to get more power...I wish I still had the 120SC as it would be a really good engine for my war bird project I'm planning. I actually need a pair of the 120SC's for it. Right now the 120AC's are a little heavier than I would like and have been considering putting a pair of 140 Sports in the model.

I know this was likely way way more information than you needed to know. But its a good engine and you'll love it.


Troy Newman
  ----- Original Message ----- 
  From: flyintexan 
  To: NSRCA Mailing List 
  Sent: Saturday, December 29, 2007 8:53 PM
  Subject: Re: [NSRCA-discussion] YS 120 NC/SC prop recommendation


  Should be able to run a 16x8 on 30%...
    ----- Original Message ----- 
    From: Paul Horan 
    To: NSRCA Mailing List 
    Sent: Saturday, December 29, 2007 6:09 PM
    Subject: [NSRCA-discussion] YS 120 NC/SC prop recommendation


      Any suggestions for a YS 120 prop ?  It will be on a Aires ?
    Thanks,
    Paul



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