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Old 07-16-2006, 03:53 PM   #1
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Default WHY? (OS vs NR question)

Why is it that I have absolutely no problem whatsoever keeping an OS tuned and happy and I can't help but kill any NR-based motor that has the misfortune to be attached to my buggy?

I have three different OS motors (.12TZ 5port, .18FSR in my TNX and .21 RG) and they all start and idle great, keep a tune all night, run at a reasonable temp and seem to have decent longevity and don't kill glowplugs. I've had two NR-based motors in my 1/8th scale buggy and I never seem to be able to make them or keep them "happy". I'm not aggressive, tuning-wise. I don't try to wring every drop of performance out of them...I just want them to run and keep running.

Yeah, I know about how long NR motors last and how great they are. I believe it, but you can never prove it by me. I seem to be on the outside of an inside joke or something. How come I seem to be able to tune an OS in a couple minutes...get good mileage (8+), keep plugs alive forever, not have flame-outs...on and on...and not with a NR-based motor?

Is there a fundamental difference in the carbs on each? I'm an electric guy, so I don't do the "on-off" deal much at all, so there's not much time at WOT for me...here and there on straights, coming out of corners.

My P5X was set where it would come off at 220-230 after 5 minutes with plenty of smoke...then my friend drove it for his race (His servo took a dump, so I handed him my radio) and my motor was history in 8 minutes. Flamed out, pinch all gone, wouldn't run. He's a better driver than I am, he runs expert, I'm an intermediate. Man it was flying...

Last night, I let him drive with the OS. Same track, higher ambient and the motor temp was the same as when I was running it, plenty of smoke, all was good.

WHY?
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Old 07-16-2006, 04:43 PM   #2
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I can honestly say that my experiences have mimicked yours. Don't have any explanations though. Its OS for my money.
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Old 07-16-2006, 06:00 PM   #3
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I run a RG and a Hot Mod 21-5, the OS is great for keeping a steady groove, which sometimes produces better laptimes. The OS runs like a clock, and will run even if out of tune. The Nova requires a little more attention tuning wise, and reacts differently to starting/tuning. I learned to race with the RG, but now I favor the Nova because of it punchiness, but I have to really take care of the engine.

To answer your question, they are just put together differently, and they contrast each other while they are still great mills.
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Old 07-16-2006, 07:17 PM   #4
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I get that they're both good motors...LOL...but why would I have such a hard time with one and not the other? I'm not a hack, I seem to be able to tune big motors and OS motors just fine. I don't make big changes, I'm careful and pretty conservative in my approach.

I'm just wondering if it's the part-throttle thing...every time I'm at half throttle with a NR and I can hear mine alone, it sounds like it's lean as hell. I'm starting to think that they don't deal well with part-throttle. Maybe that's the reason why I and others have such a hard time with them. Maybe it's just a question of driving style?
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Old 07-16-2006, 08:34 PM   #5
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How much time on that P5 your buddy killed? I've got a brand new P5 I haven't even started yet. Been running a duratrax engine and cheap SH for awhile now with no issues other than lack of bottom end. I drive like you say you drive, not on off. So I'll let ya know if I ever get time to break the thing in..

The novarossi in my GT now, that thing is just a reliable dream and I love that thing. It's the reason I went with the P5. My little one I swear did not even break in until halfway thru a race season. I was actually disappointed in it as I thought it didn't live up to it's reputation,,, then one day it just came alive and has been screaming ever since. Without a glow plug in the thing I would swear it has no pinch. But the thing idles all day long, will tune however I want it hot/medium/cold and will run great any of those ways and this is my second season on it and it's had alot of practice time as well as racing.

220-230 after 5 minutes, what's it come off after say 15-20 mins? That's the real tune tester to run em extended period of time and see where it sits at. Tells alot about your low speed needle also.. Maybe your needle balance is way outta whack if it sounds lean at half throttle. Set the idle, set the needles till it's pig rich and barely crawls, tune it in where you like it all the while leaving the temp gun in your pocket. Run 3 or 4 tanks thru it then temp it just to get a base setting for later. I rarely use my temp gun anymore.
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Old 07-16-2006, 08:49 PM   #6
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At the time, maybe a gallon tops...the mains at our track are 10 minutes, maybe 15 for the experts.

You may be right about the high vs. low needles...but why is it that I seem to be able to get an OS right 3 out of 3 times and have no issues? I'm 0 for 2 with NR motors...I had a ws7II for a while, too. Same thing, went away really quick, flamed out all the time, didn't idle well. It wasn't new by any means, but it had supposedly run really well prior to me getting my hands on it.

My RG came off at 230 after 10 minutes last night in 85-90* weather, so it's not like I can't figure out how to get the job done...LOL...I just wonder why/how they're so different.

I'm not a temp gun freak...I think they're as much overused as wide-band O2 in 1:1 cars. I'm just using it for reference purposes to try and get a baseline. I try to tune by smoke and how it runs and on the rich side. I changed to 20% Maxy's (from 20% Platinum) last night and had to lean it a little (2-3 hours on the top needle) to get it to pull nice and left it there...all good.
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Old 07-16-2006, 09:00 PM   #7
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Dunno man. Hope I don't have the problem with mine. My buddy just got a new P5 awhile back and hasn't had the problem you describe. Although he did have a similar problem with his .12 and it ended up being idle/needles out of whack.

P5 gone after a gallon!! I've never heard of that before, I'd think the thing should just be setting in. Still got it? Maybe seal it up, try a new glow plug and lean the sucker out!!

Since you're in Cali I would thin you could find a high profile guy at a track and ask them about it?
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Old 07-16-2006, 09:18 PM   #8
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See...that's the thing...there are lots of people to ask about them...but I don't have to ask about any of my OS motors.
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Old 07-16-2006, 09:37 PM   #9
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Well you got a point there, I didn't think of that.
Maybe ya need to try a vzb or whatever they are if you're looking for some extra oomph. Or see if ya can get the os carb to fit in the nova somehow. I put an rg carb on my sh engine just by cutting down the bottom of the round housing.
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Old 07-16-2006, 09:46 PM   #10
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What kind of break-in did you do on the Nova?

Heat cycling seems to be the best for Nova motors, they don't seem to really open up until the 2nd gallon. Most people expect the engine to be broken by then, push it too hard, and kill it.

I would continue driving it, from my experience with Novas (Modded Race 528X, Modded Plus 21-5, P5x, Modded N21BF) they only get better with time.

Happy tuning...
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Old 07-16-2006, 09:58 PM   #11
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I bought it used with 10 tanks or so, from one of the guys at the track. He's pretty fast and he always has nice stuff. He only had it for a couple weeks and it still had that new motor smell to it.

Man oh man, you should have seen his truggy going last night...holy crap.

I'm thrilled with the RG so far...I could smoke people on the straight with the P5X, but one flameout and you're done. Now I'm right with everyone else power-wise...and it runs and runs and runs. I'd just like to get to the bottom of my difficulties with NR motors.
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