First Look into a Nitro RC engine..questions

[Jeep]

This past weekend I took my Hobao(Hyper) Mach .28 engine apart mainly to seal any air leaks I may have. I had a tuning issue last time I ran it, as it only ran well with mixture settings that gave me 290 deg temps, so I shut it down and decided I probably have air leak(s).
This was my first look inside one of these engines, and I marveled at every part I took off.
I've run about 3 quarts of fuel through it, and I was amazed at how clean it still was on the piston crown, and in the case. I use aro religiously and set to BDC, but I didn't expect it to still look new in there, especially after the breakin time running so rich,,I guess my 4 stroke gasoline engine experience is trying to tell me it should look much different,,lol.

Anyway, it is a P/Start engine, and after I pulled teh backplate off, there was a "turbo fan"(for lack of a better name for it) that incased the one-way bearing and had the pin that went inside the center of the crankpin(rod-journal).

Is that fan standard on these engines?

I was very surprised to see a high polished aluminum connecting rod.

Also, I pulled the head (heat sink I think most here call it,,with good reason as I didn't know there was a "head-plate" underneath the heat sink.
Is there a specific torque value for the heat-sink/head screws? They were tight as hell breaking loose, so I torqued them as tight as I felt comfortable with going back together, a lil on each at a time in a pattern so as to make it even.

Also, I did the "quench" check for the piston-head clearance using a small piece of solder,,it came out .045" both times that I checked.
I thought it should be closer to .020" for these engines?

Anyway, sorry it's such a long post. I'm an engine "nut"!

Jeep

P.S.
The exhaust port in the sleeve matched 100% with the case exhaust port as if it was "port matched" ,,is that normal for these engines?
I expected a bit of a "lip" on one or the other or both.

 

[robriguez]

I'm loving the signature btw!!!

-Our nitro fuels are almost alcohol based and burn much much cleaner than any gasoline based fuel will ever burn.

-Umm, Turbo Fan?? can't say I've ever seen any type of fan inside my engine. Is this your engine? Which part # is it your talking about?
http://www.dynamiterc.com/ProdInfo/Files/DYN_mach28_manua.pdf
Usually the one way bearing has a notch in it that an off center post from the crankshaft connects to and thats it. Well, on the 2-3 engines I've taken apart anyway. Hmmm A Turbo fan would be kewl tho. Maybe to just keep the gasses flowing int he crank case?

-Yes, always a very highly polished and very lightweight con rod. With RPMs sometimes in the 40k range they need to be works of art almost.

-Under the head (Heat sink) is usuall is usually a "button" or "Head button" (head-plate). This seals the combustion chanber and allows for the glowplug to be screwed in. I have never heard of a specific torque value but 1/4 past hand tight is usually good. The smallest dab of blue locktight would not be a bad idea. Once all screws are seated I use 2-3 passes of an overlapping star pattern to fully tighten all head screws to make sure there is no warping and even tightening all around. (bad bad memories of leaking valve covers and tranny pans from days of old will never ever let me randomly tighten bolts/screws again... lol)

-"Quench Check" You mean like a squish test to test head clearance? LOL Sorry bud not ragging ya, just had me going nuts for a sec asking myself, "what the hell is he talking about a quench check?" Umm to be honest I'm not really sure what the clearance should be. I've done some digging and can't find any numbers for you. Other then tearing apart one of my own engines I'm not sure what its "Supposed" to be. But I can tell you, if you ever plan on moving to a higher % fuel you will have to add a shim between the plug and the button. If that doesn't work, you may have to add a shim betweenm the button and the case.

-On the better engines the ports will be matched. the better the match the better the Porting job to begin with the better the overall perfrmance will be.
And no, just whipping out the dremel is not going to mean you can start modding your owrn engines. It takes, time, skill, dedication, and ability.

Hope that helps some.
The exhaust port in the sleeve matched 100% with the case exhaust port as if it was "port matched" ,,is that normal for these engines?
I expected a bit of a "lip" on one or the other or both.[/quote]

 

[Jeep]

Thanks for the info Rob,
I took several pics with my buddies dig cam, but he hasn't had a chance to get them on to his PC yet,,when he does, I'll post the pics of the "turbo-fan"

And by the way, I'm a 4 stroke gas engine specialist,,I have NO intention of trying to mod my 2 stroke nitro engine,,I'm well aware that they are of 2 different worlds,,and I never change what works well unless I'm sure of what I'm doing.

Jeep

That isn't my engine,,that's a dynamite mach,,mine is a Hobao(Hyper) Mach 28,,here is a pic:

http://www.cmldistribution.co.uk/product.php?productId=0000001234&menu=CAR&subMenu=CR-NIT

,,it's new on the market.

Never seen a "turbo looking" fan in the crankcase?
I don't have a parts break down of the engine, it came with my Hyper 7 PBS Mach 28 edition RTR,,and the paper work for it showed the Hyper .21 8 port parts "break down" that I was expecting, but that isn't the engine I received.

Jeep

 

[Monkey Wrench]

Hey Jeep, my Hyper 7 pull-start had the same fan you're referring to. I wish I could dazzle you with the multitude of reasons it's there, but I can't! As far as I can tell, it's the only engine to have that set-up, for whatever reason.

 

[Jeep]

I'm loving the signature btw!!!

-Our nitro fuels are almost alcohol based and burn much much cleaner than any gasoline based fuel will ever burn.

-Umm, Turbo Fan?? can't say I've ever seen any type of fan inside my engine. Is this your engine? Which part # is it your talking about?
http://www.dynamiterc.com/ProdInfo/Files/DYN_mach28_manua.pdf
Usually the one way bearing has a notch in it that an off center post from the crankshaft connects to and thats it. Well, on the 2-3 engines I've taken apart anyway. Hmmm A Turbo fan would be kewl tho. Maybe to just keep the gasses flowing int he crank case?

-Yes, always a very highly polished and very lightweight con rod. With RPMs sometimes in the 40k range they need to be works of art almost.

-Under the head (Heat sink) is usuall is usually a "button" or "Head button" (head-plate). This seals the combustion chanber and allows for the glowplug to be screwed in. I have never heard of a specific torque value but 1/4 past hand tight is usually good. The smallest dab of blue locktight would not be a bad idea. Once all screws are seated I use 2-3 passes of an overlapping star pattern to fully tighten all head screws to make sure there is no warping and even tightening all around. (bad bad memories of leaking valve covers and tranny pans from days of old will never ever let me randomly tighten bolts/screws again... lol)

-"Quench Check" You mean like a squish test to test head clearance? LOL Sorry bud not ragging ya, just had me going nuts for a sec asking myself, "what the hell is he talking about a quench check?" Umm to be honest I'm not really sure what the clearance should be. I've done some digging and can't find any numbers for you. Other then tearing apart one of my own engines I'm not sure what its "Supposed" to be. But I can tell you, if you ever plan on moving to a higher % fuel you will have to add a shim between the plug and the button. If that doesn't work, you may have to add a shim betweenm the button and the case.

-On the better engines the ports will be matched. the better the match the better the Porting job to begin with the better the overall perfrmance will be.
And no, just whipping out the dremel is not going to mean you can start modding your owrn engines. It takes, time, skill, dedication, and ability.

Hope that helps some.
The exhaust port in the sleeve matched 100% with the case exhaust port as if it was "port matched" ,,is that normal for these engines?
I expected a bit of a "lip" on one or the other or both.

[/QUOTE]

I finally got the pics out of my buddies cam.
Here is the "turbo fan" looking thing:

 

[robriguez]

After seeing the pic, I definitely cannot dissagree with your description. lol

Well man the only plausible idea I can come up with for its purpose is to keep the gasses in the crankcase movin around and not letting them build up and get stale. Other than the, "Hey man, I got a Turbo in my Engine!!!" kewl factor.

Maybe some of the more knowledgeable engine heads around here might be able to give a better answer.

 

[Jeep]

All I can figure is that maybe it would help draw the air/fuel mix out from the center of the crank and perhaps create a bit of a vortex where the air/fuel enters the case and a bit more vacuum in the carb throat. Just grabbing at straws.

Jeep

 

[Monkey Wrench]

Yep! Same thing my Hyper .21 had. I think it helps in moving the air/muel mixture around and aids in moving fuel around in the crankcase for lubrication, but I can't be 100% sure on all of that.

 

[Plaidfish]

someone else has a thread on teh Hyper .21 turbo fan...it was explained there, but I can't remember what it was for......I think NCNitro knew what it was