Have I cooked it?

Old 12-27-2010, 09:11 AM
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Default Have I cooked it?

Hi all,
This is first post,i'm old to r/c, but new to nitro, need engine help.
HPI Savage XL 5.9 engine. It broke in fine and has tuned up pretty well. Has had about 20 tanks go through it. Had an "incident" which left her screeming full throttle for about 3 mins brfore i could shut her down. she got really hot! 160degrees C(320F) and don't know how long for.(i run spektrum dx3s with tele so i know how hot). Now she runs hot all time ,way to lean, can't get her below 130c(265f)even at full rich. She coughs and splutters and cuts out past half throttle.I have taken back to factory settings and re tuned many times, with no joy. Have i cooked it? Is time for new engine or am I missing something?
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Old 12-27-2010, 09:22 AM
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If it was screaming for 3 minutes before you go to it, there is a good chance you cooked it up pretty well....especially if it was screaming without a load (wheels up in the air). I would tear it down and inspect it all. After you take a look....if things still look good just run it warm and see what happens. Nothing to lose at this point right?

320 is hot, but not too too hot. Things may start to heat up to the point of warping at that temp, but usually it takes more heat than that depending on materials used in the engine and such. I know a few guys ran their engines at 320 all weekend at the Colorado National race last year and had no issues afterwards....so you may luck out. I would surely inspect it though....

Good luck man!
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Old 12-27-2010, 09:50 AM
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Originally Posted by bigsimmo77 View Post
Hi all,
This is first post,i'm old to r/c, but new to nitro, need engine help.
HPI Savage XL 5.9 engine. It broke in fine and has tuned up pretty well. Has had about 20 tanks go through it. Had an "incident" which left her screeming full throttle for about 3 mins brfore i could shut her down. she got really hot! 160degrees C(320F) and don't know how long for.(i run spektrum dx3s with tele so i know how hot). Now she runs hot all time ,way to lean, can't get her below 130c(265f)even at full rich. She coughs and splutters and cuts out past half throttle.I have taken back to factory settings and re tuned many times, with no joy. Have i cooked it? Is time for new engine or am I missing something?
she's toast. 320 degrees (F) is the thermal ceiling (failure limit) for the aluminum in most of these alloys.
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Old 12-27-2010, 10:18 AM
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Yep, she was belly up screaming for at least 3 mins(don't ask what happened)

It's behaving as if has over done it. i'm new to r/c nitro,but been round engines all my life. The compleat lack of response from most of the carb settings,having to go lots of threads on the screws to see only slight, if any change, is usually a good sign the trouble, lurks deeper!

Now having said that, having only just finished reading the Paris"tuning bible",(i probably should have done that first, says "important " for a reason.) i think i am going to have another go at a tune. Some symptoms mentioned sounded to close to not give it a shot.

Even if saved, once running good, i'll pull it down any way. Can you put these engines back together again using the same bits? or do you need head seals/gaskets and the like? A simple HPI engine kit is not that easy to get your hands on over here in oz.
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Old 12-27-2010, 10:28 AM
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What happened! Tell us!
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Old 12-27-2010, 10:45 AM
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Did you inspect the carb for debris/trash?

Similar boat as you - old to R/C, new to nitro, built/played with many 1/1 hot rods with carbs.

Long story short - my new Hot Bodies D8 buggy: fuel line, where it meets the clunk in the tank split. Didn't know this for 2 races chasing a tune. Needle settings have little to no effect, with a final tune having the HSN sticking out well past factory setting. Would run "ok" for qualifiers, but about 4 minutes in the main events, it would die at WOT. Seems the problem (detailed below) was inconsistently affecting the fuel mixture - allowing it to work at times, then not.

I removed the HSN and well blessed with an obvious problem: a sliver of the shredded fuel line stuck to the tip of the HSN.

After a full teardown and cleaning of the carb, my tuning issues are gone.
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Old 12-27-2010, 10:58 AM
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What happened was my 3 year old daughter!

Again!

Many of my r/c projects have had a run in with her during their life. She digs her cars in general, but for some reason daddy's "funny cars" as she calls them, get alot of attention. She is usually with me when i'm giving them a run, and she has a little electric truggy she thrashes around.

This time she decided to stand in quite an "angry" ants nest in the middle of a run. Hideous driving performance on my behalf(i was a little distracted)resulted in my truck taking on a rather large above ground, metal sprinkler. i lost steering,body shell and most of the front bumper assembly. what i did gain was a busted throttle linkage which managed to jam at full throttle! and the truck took off at rate of knots accross the park, straight in to a park bench,only to cartwheel before landing belly up,full pedal, screaming.

I had to choose either rescue of the truck or my little one. the truck could disassemble it's self completely and give me less pain in the future than what a few ant bites would. so, she won and the truck came 2nd, about 3 minutes later. Hence the long "hot" run time. Kids!
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Old 12-27-2010, 11:02 AM
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Make sure you add a return rubber band on the throttle linkage to CARB this is a easy but forgotten itemit will save you $$$. Some don't run since it adds more stress on the servo but Ive been running for a long time no issues.
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Old 12-27-2010, 11:13 AM
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"A Rubber band on the carb" Sounds like a much better option to the "cut off switch" i paid good cash for! The reciever didn't do it's job either. Don't know what happened there? It is all working now.If only they could talk!
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Old 12-27-2010, 11:41 AM
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hello,

just my 2 cents,

i dont think you cooked it, happened to few guys around without problems, take it apart, inspect everything specially the bearings. take the piston/sleeve out and check the rod. and PLEASE forget about your Dx3s tele as i've never seen a good one, they are always off.

if its spitting rich and the temp is 260 your tele isnt functionning correctly, disconnect it and use a normal temp gun.

320F for a minute or two isnt very very bad as you think. still my opinion, if someone disagrees whith me, i tottaly respect it.

cheers

Ali
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Old 12-27-2010, 12:04 PM
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Originally Posted by KWT-NITRO View Post
hello,

just my 2 cents,

i dont think you cooked it, happened to few guys around without problems, take it apart, inspect everything specially the bearings. take the piston/sleeve out and check the rod. and PLEASE forget about your Dx3s tele as i've never seen a good one, they are always off.

if its spitting rich and the temp is 260 your tele isnt functionning correctly, disconnect it and use a normal temp gun.

320F for a minute or two isnt very very bad as you think. still my opinion, if someone disagrees whith me, i tottaly respect it.

cheers

Ali
While the high temp for extended time is debatable, the effect on the rod of 3 minutes at WOT, with no load, isn't....that sucker has been seriously stressed.

Pull your motor completely apart, then try to push the piston up to the top of the sleeve. You should see a nice brown ring around where it normally stops. If it goes well past that before getting tight, or goes all the way to the top of the sleeve period, you either need a new piston / sleeve, or to have that one pinched.

If the piston and sleeve are good, make sure everything is nice and clean, then re-assemble with a new rod.

I also agree with not using the on-board telemetry. You're reading temp at the outside of the cooling head. You need to be more concerned about the reading directly over the glow plug. Even then, always tune by performance first, and temp second.

Let us know how it works out for you....

Last edited by Stubbs; 12-27-2010 at 02:39 PM. Reason: typos....
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Old 12-27-2010, 12:16 PM
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ALWAYS replace the rod after a bad runaway (assuming the rest of the motor survived). This may not be your problem but it will save future failure.
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Old 12-27-2010, 09:52 PM
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after checking engine and compression i would look at your clutch... could of broken a spring as well or even wore the shoes
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Old 12-28-2010, 12:51 AM
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One more, seal it up real well. Air leaks will drive you nuts.
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Old 12-28-2010, 05:59 AM
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Wow, lot of info. thanks heaps guys. Being in Australia it is hard to find any aussie forums that are any good.(if you know of any please list them) To get so many responses, so quickly, is very exciting!!

The local hobbie shop when asked the same question, told me" no, it's stuffed, buy a new engine, haven't got the right one but this other thing should do the job." I asked about ordering the correct hpi part and was told "yeah we can but your guess is as good as ours as to when it shows up, could be couple of weeks, could be a couple of months."

I'm in the west of oz, which is even more remote. So before any aussies fire up, i realize the eastern board is much better but personally internet shopping isn't as exciting as dropping into the store and walking away with exactly what you want, or something just as cool. Having it turn up a week later in the post just doesn't cut it. Not to mention it's much harder to hide it from the wife when it gets delivered to her during the day when i'm at work.

As i said before: thankyou and i'm very excited to explore and involve my self in this site, cheers!
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