GeeReg

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My Duratrax Axis may need a new engine, and it may seem strange but I'm debating between a O.S. RG and a OFNA .27 Picco. I'm drawn to the RG because everyone says it's just about the easiest engine in the world to tune and it holds it well. I'm drawn to the .27 because of the power obviously but I'm worried about how easy it is to tune. This is for bashing and no racing. My possibly stupid question is, will the .27 necessarily be a lot faster? If geared the same, wouldn't the two engines produce similar top speeds, but the .27 will have much more torque? It's my understanding that the power of the .27 allows you to gear up to achieve a higher top speed than the RG while still making enough down low. Is this how it works?

GeeReg

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I know there are people here who run larger engines, help me out here.

1CE

i ran a picco .27 in my mayhem...it was great tons of torque and good top speed just stay away from the pullstart version and get the non-pullstart...

GeeReg

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Thanks, did you use a larger clutch bell?

JEXTEL

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your axis..I think you might ave to beef up your drivetrain before you put a .27 on it..I say get something like a Mach .26/ sportswerks .26 they have tons of power but not to much and its a big block..I have learn over this season that you dont need a Huge engine..Well only in NT's..haha lol

1CE

what do you mean by that? more teath or just bigger diameter (there is no such thing as a bigger diameter clutch bell as far a i know)
if you where talking about teeth then it depends on what kind of power you want. if you want torque and fast asseleration then u use a bell that has a smaller amount of teeth. if you want a slower accelerating buggy with a higher top speed then u get a bell that has more teeth.

GeeReg

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That's one thing that I'm afraid of Jextel, breaking something in the drivetrain. I don't need to worry about racing and being fast, I just need the power to have fun with it. 1CE, yes I meant a higher tooth bell. Like I was wondering in my first post, if you usually gear higher with a really large engine because it has relatively more torque than a .21? I'm thinking that for example, if a .21 has say 1.5hp and runs to 30,000, and a .27 has 3hp and runs to 30,000, will the .27 be any faster in terms of top speed or just acceleration? I thought that the hp would let you use higher gearing for a faster top speed without sacrificing much torque.

kx250ryder

In your example, this means that at the given RPMs at which the engine reached PEAK Horsepower (the numbers you quoted) yes, the one with the higher horsepower will accelerate better. However, you must understand that horsepower is only your engine's ability to accelerate at a given RPM. That engine that makes only 1.5hp may have a low peak, but its power curve may be broad, meaning that it makes say at least 80% of that figure through most of its RPM range. Whereas on the other hand, the 3hp engine makes that amount at 30,000 RPMs and only produces 40% of that across the rest usable RPM range. In other words, you only get the HP numbers that manufacturers claim at one specific RPM range. What they usually don't tell you is the percentage of peak HP that an engine makes for the rest of the RPM range (power curve). Horsepower is actually a function of torque:

hp = (torque * engine RPM) / 5252

What this means is that your engine's torque is actually behind the number you see expressed as horsepower. Torque numbers are more significant because they will give you a broader, higher horsepower curve throughout the RPM range. As you can see by this formula, the higher the engine revs, the higher your horsepower value. That isn't very useful unless you have one hell of a long straightaway. What is useful is to have a high torque rating, however I do not know if manufacturers list these.

I think this concept is why an engine like an RG can have such low HP numbers, yet still be able to hold its own.

Read this, it will explain torque and horsepower:
http://64.233.167.104/search?q=cache...function&hl=en

GeeReg

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Kx, thanks for the response. I have a good understanding of engines, hp, torque, rpm, and all of that. I also understand that the hp #'s from manufacturers don't mean anything. My theory was that with such a large displacement, a .27 may not make 3hp for very long, but it will make say 1.5 for a larger range than a .21 will. The rpm values I was using were more of the usable range than the rpm at which peak hp occurs. I was saying if a .21 and a .27 both will only rev to 30,000, and the same gearing is used, they will have the same top speed. Is that not correct? The fact that the .27 makes so much more power, throughout the rpm range though, would mean that you can use a higher gearing to achieve a higher top speed, without sacrificing too much torque. That's all I'm really wondering.

J_Bone

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Yup. Torque moves mass!!

plaidfish

HP is how fast you hit the wall
Torque is how far you take it w/ you.....

GeeReg

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As much as a pullstart sucks, I'm inclined to get it because I don't have a box. Then if (when) it breaks I can buy a starter. But also, wouldn't I need different mounts to lower the flywheel? I don't know if Duratrax makes any.

GeeReg

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Ok, people are saying you don't need any modification for a starter box, but I have another question. Isn't the TORQ .21 an SG and not a pilot shaft? http://www2.towerhobbies.com/cgi-bin...?&I=LXPG71&P=0 And if so, why is this person talking about modifying the mounts for an SG to fit?


I have a Novarossi CL in mine with the Duratrax 4 shoe racing clutch option. I just noticed someone asking about the clutch. It grabs really nice! Coupled with the center Torsen diff it really cooks! To put in the Novarossi, I had to massage the Duratrax mounts a bit. The Novarossi engine block cooling fins made it too wide to fit into the mounts. A bit of filing will make the mounts wide enought to take it. Only a mm or 2.
Its a SG shaft too. SG shaft engines fit but the mounts need more work again. Theres a re-enforcement bridge of aluminum that has to be removed so the engine could be pushed far enough forward on the mounts. Its the rear engine mount bolts that hit it when you push the engine forward on the mounts. This bridge gets in the way. I just drilled out the bridge. You also need an Ofna clutch shim kit 10099 and the Ofna clutch nut 17015 (sells on Tower) for the SG shaft install. In the clutch shim kit theres a few shaft extensions. I used the short one, shimmed it with the included washers and bingo, SG engine installed in an Axis. It takes an hour, some filing, a drill, patience and $15.00 in parts to get an SG in there.

GeeReg

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Alright disregard that last post, so SG and pilot shaft are the same thing. Then what is the type of crank on the TORQ .21 called? Standard?

Super_Dave

First these engines have no rev limiters depending on how you gear them and how there tuned you can hit 50,000+ rpms if you want... not that I'd sujest it because the con rod wouldn't last long . But the only way to put it is that HP ratings and RPM ratings really aren't accurate with these engines but it does give you an idea. Keep in mind it depends on what dyno the manufactures used too because if they use two different dynos chances are the results will be a little different.

The picco .27 will give you more top end speed without changing gear ratios because of the torque. The added torque and HP will let the buggy push through the wind resistance and the friction through the drive tran easier giving you higher speeds (wind resistance starts to come in slighty at around 25mph and of coarse the faster you go the more resistance you get). I've broke in both engines and have ran both engines but not on my own equipment. Either way the picco .27 had more overall power and top speed then the O.S. RG... you could also hear the RPMs were getting higher at the end of the straight away. But thats only stock. Recently a friend of mine and myself started polishing the ports on the sleeve and the crank shaft... along with anything else that could cause resistance in the motor with fuel in the crank case like the con rod. A polished RG vs a stock picco .27... I actually think the RG edged it out a little bit. We didn't drag race but just the feel of the RG had more throttle responce and the RPMs came up a little bit quicker. Also the engine temps on the RG were cooler for making that kind of power (about 230 degrees while the picco was at 250). Now we haven't gone through a polished engine yet so I don't know how long the motors going to last especially the con rod... but it was making some serious power for a $110 engine.

Both engines for overall tuning are both pretty easy and hold a tune well. The O.S. RG is easier to tune and holds it better... but the picco is fairly easy as well.

I made a thread on here when I polished my Mach .26 you can probly find it somewhere fairly recent.

kx250ryder

Yes, you are correct. 30,000 RPMs will yield the same top speed regardless of engine brand. You are also correct with your assumption that the more powerful engine may allow you to run taller gearing for higher top speed, without sacrificing too much acceleration.

GeeReg

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Thanks guys, I'm glad to hear the Picco is easy to tune. I think I'm probably going to go with the RG instead of messing with the mounts to try and get an SG to fit in there. We'll see.

Engrose

You can get the RG with or without a pilotshaft and with or without a pullstart.

But I don't see why there should be a difference in length between a pilotshaft and a non-pilotshaft when the clutch is assembled?

The pullstart on the RG is rather big and clumsy whereas the pullstart on the Picco is small. But you really should consider to get a non-p/s and a starterbox. It makes life so much easier.

GeeReg

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I know, I bought a replacement pullstart for my TORQ after the original one broke. I started the buggy, drove around for 5 minutes, went over to it, and the handle was gone. Now the one I have, I think the one way bearing is gone, not to mention I can't get the damn thing to run right in the first place, so I've had enough of it. Oh and I have no idea why the lengths would be different either.

octospider0

Geereg,

I have run 3 motors in my Kyosho, first being an RG and the last being a Picco .27 and if you want power and damm the rest get the picco.
It is a monster right out of the box, so much so I am considering putting a 15t bell on it to tone it down some (currently 14t). Middle mill was a hyper 8port race and on a good day (never buy one again) it had a 13t bell and wasnt too much torque.
The Picco spools up faster then any mill I have ever seen. I got mine with the pull start (although I use a bump box) and planned on putting a reg back plate in to lower rotating mass, but there really isnt much point. Its almost too much motor. After the initial breakin I have adjusted the low end maybe 2 points and the high end 3 (clock scale of 1-12 o'clock each point) and it runs a continual 220-230 degrees. As was mentioned, I dont know how the other parts of your drive train are going to do under the pressure but if you want a strong mill and much lower the modded prices Picco is the way to go.

my .02

GeeReg

My Feedback: (1)

I appreciate the input. I'm not sure if Duratrax makes anything to beef up other than a metal spur. What else do people usually change? After reading that post from another board that I posted, it has me worried about fiddling with the mounts to make an SG work in there. Also cheaper is better for me, so I will probably get the RG and if for some reason I feel it's not enough, I'll sell it and upgrade later. I have just read too many good things about that engine to not give it a try.

Volfy

My Feedback: (23)

If you are going to use a startbox, then the OS .21 RG is substantially cheaper at $110 and a much better buy. If you need or want the pullstart, then the $35 difference between the $140 RG and the $175 Picco .27 is not enough to favor the RG. AFAIK, Picco .27 does not come in a non-pullstart version. Correct me if I am wrong.

I'm somewhat in the same boat with you. I was going to put a Collari .32 on my 9.5 Pro buggy, but have since found a more appropriate home for that monster. I am back to hunting for an engine for the 9.5 Pro. The few I've been considering are OS .21 RG, Ofna Picco .27, Werks Racing Picco .27 (identical AFAIK, just different head color and cheaper than Ofna at some places), Orion Wasp .28, THunder Tiger .28, and Peak Performance Diablo .28. Not sure if the 3 .28s are close cousins and all OEMed at the same factory.

Engrose

You can get the Picco .27 with or without a pullstart. Just as you could with the .26.

GeeReg

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Volfy, that was kindof my thinking and why I was comparing the 2 in the first place, because the price was similiar with the pullstart. I would be getting a box though so it's going to be the RG and probably the $50 OFNA compact 1/8th box.

kx250ryder

If you are considering engines that are of outlaw displacement, the Sportwerks .26 is your best bet. If you want a .21 for under $150.00 the RG will likely provide the best results.

Get an OFNA "Chrome Top" starter box. Part no. 10250 or 10253 (includes power panel). This unit is a 12 Volt heavy duty starter box, that should be able to start even the toughest to start engines. You can find one for under $80.00 on e-bay. Splurge with this item, it will save you many headaches later. Don't forget to pick up a 12 volt battery to power it. Here is an example:
http://www2.towerhobbies.com/cgi-bin...&I=LXL370&P=ML