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Old 06-15-2009, 09:22 AM   #1
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Default RC8/V-spec tuning

So this is my first REAL nitro…(I had an RC8 before but it was junk, so I kept it for about a month)

Anyhow, I have a V-Spec that was broken in by someone that definitely knows what they’re doing, and the car was set up properly, etc.
So, this engine has about 1.5-2 gallons on it, and the problem I am having is finding a good tune. If I lean out the car top/bottom to get the power I need, the car is coming off the track at about 260 degrees. I ran a club race last week, and the car felt like it had a really fat bottom end, and came off the track at 230. I was really excited about that, but I just can’t get the engine where it has a good balance of temp/performance. I think part of my problem is that once I get it up to operating temp, I hop around too much between tuning my lo/hi. Also, when the car first starts, before it is to operating temp, it will not idle properly…if I don’t stay on it, it will stall. Is this a combination of a fat bottom end/cold engine?
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Old 06-15-2009, 09:26 AM   #2
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Also, I am running a JP-4..I've heard nothing but bad things about this pipe. Could that be part of my problem? I've heard I need a Losi RE-11.
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Old 06-15-2009, 10:18 AM   #3
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Try a OS 2050 or OS 2060 pipe that v spec will come alive
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Old 06-15-2009, 11:06 AM   #4
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If you can swing the $150+ get an OS pipe, if not the RE-11 with a square header worked really well for me this past weekend. Although I still like the Losi sport pipe (that comes on their rtrs) with a square header. I was getting stupid runtimes with that, and all the power I could use.

Also try leaning the MSN to the 3 o'clock position, I did this over the weekend on Mr. Twisters advice and it really helped my tune.
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Old 06-15-2009, 11:44 AM   #5
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+ 1 on the OS 2060 or a Mugen 2042 (this is an OS 2060 copy). I run this pipe with a mugen L shaped header in my 8T 2.0 and it has almost too much power. I never thought I would say that.
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Old 06-15-2009, 12:11 PM   #6
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Get rid of the JP-4 and get a losi RE11. For the money you can't beat it. The v-spec likes the RE11(2050 copy) better than the 2060/mugen 2042. The 2060 is best on the speed. I run my v-spec with the losi pipe with stock header and it has been excellent. Making tons of power and getting outstanding runtimes. If it has enough power for my truggy, it will be plenty in your buggy. The JP-4 really smoothes/limits bottom end. IMO it's only use is to calm down a super power .28. Oh and the losi pipe is efra approved, where the os 2050 isn't, so if you are at a big race where they check that, you will be fine.
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Old 06-15-2009, 12:21 PM   #7
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the o.s. 2060 is a screamer on the v-spec
my PTM v-spec o.s. 2060 combo is way fast
nice liner power does not hit to hard on the bottom
end this good for the tail happy rc8
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Old 06-15-2009, 12:22 PM   #8
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sorry duplicate post
i hate frontier comm. thay suck !
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Old 06-15-2009, 06:28 PM   #9
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What's wrong with a JP-4 on a V-Spec? I run that on 4 diffrent vehicles with great results....
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Old 06-15-2009, 08:30 PM   #10
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Quote:
Originally Posted by GoodGuy30 View Post
What's wrong with a JP-4 on a V-Spec? I run that on 4 diffrent vehicles with great results....
IMO it's too soft on the bottom. Maybe for a buggy in very slick conditions, otherwise you are just limiting the engine.
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Old 06-15-2009, 10:20 PM   #11
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I wouldn't be worried about the engine running at 230. 260 is getting up towards the ragged edge though.

My V-Specs were always grumpy when started at room temp. Took about 15 seconds of them running before they'd stop lean bogging.

As long as you're seeing smoke when you grab the throttle, and seeing a little smoke down the straightaways, don't worry about the temp. If the engine feels soft on the bottom and you're not seeing a noticeable puff of smoke when you grab the throttle, try fattening the bottom a couple of hours. I have a bad habit of running the bottom too lean, maybe you're doing the same thing?
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Old 06-16-2009, 04:44 AM   #12
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Quote:
Originally Posted by CaptainHowdyt13 View Post
So this is my first REAL nitro…(I had an RC8 before but it was junk, so I kept it for about a month)

Anyhow, I have a V-Spec that was broken in by someone that definitely knows what they’re doing, and the car was set up properly, etc.
So, this engine has about 1.5-2 gallons on it, and the problem I am having is finding a good tune. If I lean out the car top/bottom to get the power I need, the car is coming off the track at about 260 degrees. I ran a club race last week, and the car felt like it had a really fat bottom end, and came off the track at 230. I was really excited about that, but I just can’t get the engine where it has a good balance of temp/performance. I think part of my problem is that once I get it up to operating temp, I hop around too much between tuning my lo/hi. Also, when the car first starts, before it is to operating temp, it will not idle properly…if I don’t stay on it, it will stall. Is this a combination of a fat bottom end/cold engine?
To begin with, yes, engines will seem "fat" until they start to come up to temp. Don't pay any attention to how it behaves when first started, it should seem a little fat. Now, if it simply won't stay running, you may be too fat on the bottom.

Second, 260 is a bit on the warm side. You probably didn't hurt anything (maybe the glow plug) but try to keep it under 250... under 240 is better. A VSPEC is generally a screamer without leaning to the point that you're overly hot.

That being said: Once it is warmed up, how is the idle? Does it idle well for 8-10 seconds, then fall slightly and start to load up? Or does the idle fall quickly? (too fat on the bottom) Or does it keep the same idle for an extended period of time? (too lean on the bottom)

Have you sealed your motor? (In other words, remove the carb, put a VERY small amount of silicone around where the carb body seats to the motor, and reinstall... remove the backplate and give the mating surface a light coat of silicone... and put a dab of silicone over both ends of the carb pinch bolt.) Do most of them seal ok without all of that? Yup... but better safe than sorry right?

START WITH A FRESH GLOW PLUG! We almost never use anything but OS P3 plugs in the VSPEC. Only when it is VERY hot and humid do we run anything else.

Get the low end to behave right first, then tune the top to get good power... You want it to idle well for 8 seconds or so then to drop slightly as the motor loads up. If you pinch the fuel line it should speed up slightly then die. Don't chase temps... just keep it in a safe range. Anything from 200-240 is safe. Under 200 is too low- a cold motor wears faster. Much over 240 and you are probably starving the motor for fuel (and more importantly for oil.)

Start fat and work your way to lean- it is safer that way. If at all possible, get someone with some experience to help you tune. An experienced ear (and eye, for how much smoke) is a better tuning tool than a temp gun- the temp gun is more of a safety/sanity check. We DO use it to tune... (what's the temp? Can I safely lean it a bit more?) but it doesn't tell you the whole story- you can be too hot from being lean on top or on bottom... and one end too lean and the other too fat can mask each other by moderating the temps- the temp will look right but the engine will be a dog. An experienced ear will tell the difference. Unfortunately that isn't something that is easy to explain, so I'm not going to try- maybe someone can do a better job than I can on that part... but what I described above should get you fairly close. Just approach it conservatively, and remember that too fat is less harmful than too lean.

Finally, regarding the JP-4. It may not be THE best pipe for that engine, but it isn't a horrible choice... it is a decent match.
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