ben805

Bought some new fuel (O'donnell racing) so I went out tuning my GT2 and ran a few laps, hps was set at 2 1/4 turn, approximately 1/8mi stretch, at wide open throttle(WOT) I can clearly see bunch of smoke coming out of exhaust so it appear to be running a bit rich, after 4 to 5 laps I noticed acceleration wasn't as punchy, didn't thought much about it since I figured it's probably caused by slightly rich mixture bogging it down a little, on my 6th run at WOT my car died half way, the engine wouldn't turn over afterward, the pullstart was stuck so I took the engine apart and found the connecting rod snapped off, and few pieces of metal was stuck at the crank shaft as well.

My first question is....HOW, and why did it happened? at idle my exhaust was spitting out a bit unburn fuel so if it was running rich how did the engine got blown? looking at the glow plug, I saw the element got fried as well. [:'(]


2nd question, does this has anything to do with the o'donnel fuel i was using? I'd always run trinity monster power, and this engine only saw 1 gallon trinnity and about 2 tanks of o'donnel [:-]


3rd question, is it worth it to rebuild this AE .15 motor? I have a new OS .18 CV-RX(S) sitting in the box waiting to be swap in, what can I do in the future to prevent blowing up this brand spanking new OS motor? I don't race, only bash in the backyard.

twomanytoys

First off what %nitro and oil were you using and was it the same when you switched? How old is the motor and how much fuel have you ran through. Running too rich is just as bad as running too lean. If you run too rich the motor wont get hot enough to expand the pinch in the cylinder. Now by running too cool at wide open throttle there is too much resistance between the piston and cylinder pinch and that can break a con rod easy.

Also I can tell you that you had some major leaks by looking at your motor. That thing is a mess. If you had any air leaks expecially at WOT can kill te motor. Do you have a temperature guage?
The os18 is going to be a way better motor.

rclynx

I can't make out the picture well enough but it looks like you have a broken connecting rod at the top, and from what I can see it looks like there has been one to many WOT's for prolonged periods of time. If what I see is true and engine at WOT for 20 or 30 seconds can cause that and the more times that WOT happens the more likely a rod will break........its just part of the game or Hobby if you will.........fuel usually never has anything to do with it unless you went to a high % and didn't re tune[&o]If you run to rich you get what is called predetination after it gets hot from WOT and that slams the piston against the sleeve and rod or to lean you get heat and burn a hole in a piston..........there are a few more explinations but I think this is sufice[&o]

ben805

the trinity monster fuel has 18% oil contain I believe, the o'donnell has only 8%. Both brands are 20%N, this motor only went through 1 gallon of monster and about 2 tanks of o'donnell. My motor has no leak whatsoever, all those carbon built-up on the header, engine block, and heatsink is caused by all the unburn fuel along with afterrun oil spitting out from exhaust, my car had always been running on the slightly rich side. No temperature gauge but I just bought a new one.




yup, connecting rod got chewed up pretty bad. and true, this motor been through many WOT runs at the same 1/8mi stretch, though most of the time it was about 7~10 seconds at WOT back and forth for 2 to 3 tanks of fuel non-stop. So I guess it's very unhealthy for the engine to make high speed run like that....but is there any way to beef up the piston/rod to take this kind of load?

ben805

here is the full size picture of my blown motor:

http://i.pbase.com/o6/21/662221/1/84...0.DSCF0846.jpg

http://i.pbase.com/o6/21/662221/1/84...h.DSCF0845.jpg

ben805

Another thought, instead of putting after-run oil into the glow plug hole, I think next time I'll just mix a few drops into the fuel tank and let the car idle till it empty the tank?

rclynx

Pinch that fuel line every time and clear the crankcase........................and there will be the Oh you don't have to do thats around but their FOS / got to pull that plug and drop run after oil into the hole and bottom out the piston.............sounds like your doing things right but just got a little bad luck more than anything. There is one more thing I would like to express WOT for distance is why they have temp meters and there used most of the time for on road cars because there the ones who hold those high R's more than the ST's. If you have a spot where there is a long straight away you need to check that temp right after the straight because it just might have been running a lot hotter than you think.............no way to tell now and your plans are for a good all round engine. OS will probably never give you any problem and you will forget all about this miss hap[]good luck and if your doing a track all the time you might want to look into some of the 12's, there are a few of them around that will smoke that 15 and take the R's better to[X(]

MiamizFinest

that motor looks like is was running at 400 degrees to me......that thing is toast ive bein use OD for over a year and not one of my motors looks like that.........OD is made with sythetic oil so it doesnt leave any kinda of carbon diposit's most of my motors look brand new inside with out a signle dark mark.........


didnt you notice there was something wrong when the fins started turning black?????? that kinda damage CANT BE DONE in only 2 tanks......that thing was porbably messed up a lnog time ago till it jsut crapped out

ben805

I'll be using a couple inches of fuel hose from automobile to extend the exhaust tip, that way I won't get any exhaust overspray all over my new engine again. I'd soaked that header overnight with simple green, able to rid most of the carbon build-up and I'm just done putting in the new motor, haven't got a chance to run it yet but this new motor is a biatch to fire up and and when it did, the sucker won't hold the idle, will have to try it again some other time.


as for my blown motor, maybe I still can sell it on ebay the way it is now.

rclynx

That OS engine starts out like a bear and gets sweeter as it goes........about 10 or 12 tanks it will be sweet