kyle_yokomo

Hi i just picked up a new OS 18 CVR engine that i am going to put in my proboat hydro. The directions say on break-in to start with the high speed needle 2 turns out from fully closed, does this sound right? Does anyone have any experience with OS motors that can help me, 2 turns out seems pretty lean to me, but maybe its right.

Dan S

I started at 3 1/2 turns out.

Dan.

kyle_yokomo

OK thanks Dan

Jerry Dunlap

Running an engine too rich won't hurt it. Running an engine too lean can cause damage.

JD

Sean Bowf

The problem you are going to run into with comparing needle settings, is that different pipes, will cause different amounts of pressure in your fuel tank. So you would use different needle settings for different pipes.

With my MAC 3.5 pipe, I started around 3 turns out, ran two tanks, then started leaning it in an eigth turn per tank. After some more experience with the engine and pipe combo, I can see that starting a little richer than 3 turns out might be bettter. I say this because with the setups I have been using, I wind up at about 2.5 to 2.75 turns out after break-in.

Again, this would totally depend on your setup. If you had a smaller pipe, this might be too rich for you.

Sean

NWDave-RCU

Running an engine too rich will wash out the taper/pinch between the sleeve and piston. It won't be quick and painful like running it too lean/hot, but it will wear out, and be disturbingly slow while it wears out. I have a lot of R/C truck experience with the various O.S. .18's, and on land, they run best around 2 1/2 turns out, in a temp range around 230-260 degrees on 30% O'Donnell's. Any colder, and they just don't rev or make power like they should.

Dan S

I'm not going to start the temperature debate again, I run boats and buggies and yes with my buggy my Novarossi is at 230 to 260, but my Marine (water cooled) Novarossi is at 140 to 160.

Don't try to run a water cooled marine engine at the same temp as our trucks, buggies, Truggies, MT, or Baja. it will not last.

Dan.

kyle_yokomo

I contacted a O.S. rep. who said that 2 turns out is the right starting point for break-in? I still dont think thats right. Anyway Im going to start break-in at 3 1/4 turns out[X(] I also need some other advice, a couple of the guys I race with run the OS 18 with its regular cooling head, not the water-cooled head. There boats are super-fast and they claim they have had better success and higher top speeds with using the regular cooling head. They say to keep the engine temps between 210 and 220. I not sure on whether to run my engine like they do or put on a water-cooled head.

Jerry Dunlap

By "regular cooling head," do you mean the finned car head? I ran an O.S. 18 TZ Turbo in a Miss Vegas and w/o wrapping cooling coils around the fins could not run the engine w/o overheating issues.

JD

NWDave-RCU

I've seen people run a non-water cooled car engine in an outrigger hydro, but with no cowling, sticking out in the breeze so to say. I gotta admit, some of my RC truck bodies don't offer the best in airflow, and my trucks aren't always ripping around at top speed. So average speed is more like just 20 MPH, and the O.S. .18 engines stay under 270 deg., and still make really good power.

I know there's more of a fine line on operating temp range, when you go up in percentage of nitro. I used to race with 60%, and practice during the off season with 40%. Some people would freak at the thought of changing fuels, but we just kept note of the needle settings, and the pipe length, everything else, prop size, strut angle, was kept the same. I think a temp reading from the glow plug area, on a water cooled head equipped engine would be a false reading. A side shot, from the cylinder case would give a more realistic, and higher true operating temp.

glennb2006

It seems to me that the manufacturer (post 1) and the rep you spoke with are singing off the same song sheet, two turns out.

I would suggest that OS have gone to the effort of recommending 2 turns out for a reason. Therefore, seems to me to be sensible to follow the manufacturers recommendations.

As you probably know, temperature is criticle, and no more so than when running in. Too much fuel may cause the engine to run too cool, with too much lubrication or maybe not to run at all!!

I would follow the instructions from the manufacturer.

Glenn

f16man

I never seen a nitro engine hurt in any way running rich except a glow plug failure, the pinch at top of cylinder gets worn with combustion temps too high. The piston will always grow more than the sleeve so the trick is to get the piston broke into the cylinder without scuffing it up, too much heat or too lean will kill the piston early. NITRO ENGINES ARE THIRSTY DEVILS AND IF YOU RUN THEM HOT OR LEAN YOU WILL BE REPLACING THAT ENGINE SOON. Fuel oil mix does not wear out metal parts.

piper_chuck

My Feedback: (12)

Have you ever compared the compression of an ABC engine when it is cold to when it is hot? I've done this on many engines and the compression of the hot engine was ALWAYS lower than the cold engine. Also, why does the pinch become significantly less when the engine is hot? How is this possible if the piston expands more than the liner?

The debate over whether it is bad to run an ABC engine sloppy rich has been hotly debated in the engine forum. There are many reports to indicate doing so can ruin an engine. There are also statements from many prominent engine manufacturers and experts saying it can ruin an engine. These reports and engine manufacturer recommendations are enough to convince me that it's a bad idea to run an ABC engine sloppy rich during break in or any other time. I break mine in somewhat, but not sloppy, rich for several runs and then start leaning it out.

Sean Bowf

Most of the engine instructions I have read, say to run it so rich that it barely runs for the first couple tanks...this is true for the CVRM engine...

Sean

kyle_yokomo

Sorry let me clarify, when I said regular cooling head, I meant the finned car head. The guys that are running there boats this way leave the cowling off.

NWDave-RCU

If you're going to be using the car/truck .18 CV-R engine, with the finned heat sink head, you may end up with more water inside the bilge than you like running without the cowl on. I would score a water cooled head, $26 or so at Tower.

f16man

The aluminum piston sheads more heat than the sleeve does #1 also a sloppy rich setting would be putting the glow plug out or hammering the coil so at that point you would be leaning it out anyway. The piston will grow larger than the sleeve if the lean/hot condition continues, and that is why we have bottoms of rods torn out, scored pistons and wrist pin failures. The point is that I have never seen any damage to an engine from running rich [except an automotve engine washing the rings out] they just wont rev up and that would promt you to lean her down somewhat. There is a bit of a fine line on our nitro engines between getting the heat up to break it in and frying a new engine.

piper_chuck

My Feedback: (12)

While running, or do you mean when the engine shuts off? If it's while the engine is running then the piston would stay cooler, and therefore, NOT EXPAND as much. If what you said is after then engine shuts off then I'd be curious how a piston could cool faster than the liner that nearly completely surrounds it. If anything, they will reach a nearly equal temp pretty quickly.
A setting that is "putting the glow plug out" is meaningless, the engine won't stay running. I was talking about excessively rich settings where the engine does stay running, but way lower than it's typical operating RPM. For example, a setting where a boat that might normally go 35 mph is only going 15 mph. Clearly that is overly rich.

Could the problems you cite, from excessive lean runs, possibly stem from the fact that at excessive temps the viscosity of the oil goes so low that it no longer protects the metal? Yup, sure could. Could these excessive temps also cause the metal to get softer and be more likely to fail? Yup, sure could. If the piston outgrows the sleeve, at NORMAL running temps, then why does nearly every manufacturer of ABC engines have a diagram showing exactly the opposite? Are you suggesting they don't know what they are talking about?
Any my point was that MANY PEOPLE HAVE SEEN ENGINE DAMAGE FROM OVERLY RICH BREAK IN OF AN ABC engine. Tell me, just because YOU haven't seen something, does that make it impossible?

piper_chuck

My Feedback: (12)

The OS engine manuals are notoriously inconsistent in their text about ABC/N engine break in. For example, the bigger VR-M manuals say the following: "For the initial stage, set the needle-valve as much on the rich side as possible without badly affecting the running of the boat"

JWMods

I have converted many car/buggy engines to the Thunder Tiger O/B geared lower unit. They're are two different
factors concerning "heat" in these motors and that is "low nitro" vs "high nitro". Simply, low nitro, heat builds quickly,
High nitro, hard to get them hot enough,, (keep in mind "volume" has a cooling effect ).

Generally car/buggy engines have larger headbutton volumes made for low nitro. Trying to use high nitro (60%)
in one of these and you will find the needle getting way too lean to generate heat for ignition.
I almost always have to make a hand made button (or use another engines button) to get the volume down for high nitro.
I only mention this as a warning while getting the heat right for running-in a new engine.

Slobbering rich is not always the best method unless your getting atleast over 100* (shot with a heat gun at the plug
immediately after pulling the boat off the water). It's mostly about getting enough heat to expand the parts for propper
run-in. Breaking-in really cold and your taking the potential life out of the piston/sleeve fit with every lap,, so temp is
important factor.

Lengthy break-in is also a good way to go,, working the needle "in", raising the temp up, 120,130,150 and usually around
190* they really start to run and the final temps will be similar to what the car/buggy guys run,, and why not, they're the
same motor.

Fire away, JW

NWDave-RCU

Got any links on where you score the Thunder Tiger outboard engine lower units?

JWMods

Haven't really learned how to link but I get motors and parts from <thundertiger4u> website.
The original TT o/b powerhead can be modded to run with the best of them too,, they need
another button, sleeve shims, O.S. 20J carb among other little cuts and they'll rock. You
have to do similar mods to most of the car/buggy engines and the TT pto has to be made to fit
the rear backplate area of the engine your chosing. You can buy the whole TT o/b for just
a little more than the cost of all the parts you need,, around $205 fer the complete motor.

I've done a bunch of them which includes O.S.30VG-P-X, RB728, O.S.VZ-M21, Ofna Force 4 port,
Ofna Hyper21, TT 21 BX-R with Mac 21 buggy and NR21PLUS 5-T waiting.
Some of these required crankpin to be counterbored for installing a pin to drive the TT PTO,,
not the easiest of tasks for the novice machinist.
JW

NWDave-RCU

So which powerhead seemed to work out the best on the TTR lower unit?

Also, is there a more powerful engine thyan the stock TTR .21 that will just bolt on with no mods?

f16man

Jeze Piper did'nt mean to ruffle your feathers! bottom line is too lean on breakin will grow the piston more than the sleeve will grow, the choke at the top is to hold the compression because we have no ring and up at the top in the combustion area is the hot spot where the choke will open up a bit and thats why the warm engine feels like it has less compression. And finaly yes a piston will grow to the point of seizing while running if the fuel mix is too lean. different metals expand and contract at different rates and temps, an ABC engine uses those properties very well, so if OS says 2 turns out I'll bet that 2 1/2 would be a safe start would't you?

piper_chuck

My Feedback: (12)

You didn't ruffle my feathers, so save the attitude for someone else. One does have to wonder why you've decided to get huffy in response to me, and others, pointing out things that are contrary, or in addition, to what you said.
I wasn't talking about too lean a breakin. I don't think anybody disputes that running too lean, during break in or after, will cause damage. I was talking about the damage to the piston/liner fit that many people have encountered because of too rich a break in of an ABC engine, and that you earlier implied can't happen.
Finally you are agreeing the liner will expand more than the piston, at least to a point.
I never said seizing wasn't possible. In the interest of completeness, since we have lots of beginners reading these pages, I pointed out other causes of damage from lean runs, and that start happening way before seizing occurs.
You tell me. What has worked with YOUR .18 CV-R? From what I've seen, even 2.5 may not be enough, even for post-break in running. It all depends on pipe, prop, fuel system, etc.