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Air Leaks...do you really need to seal your engine ?
I read on these forums how many people are having tuning issues, and often the first thing people recommend is sealing the engine........many times offering up crazy ideas how to test for a leak...some sensible, some not soo sensible...the craziest one is plugging up the engine and then submerging it under water and blowing into the fuel inlet to see if and where any bubbles escape........This of course is a silly thing to do, as these engines do not use the front bearing to seal the engine... These engines use the hydraulic seal created by the fuel between the crankcase and the crank, and only will seal when the engine is running......it is normal for a front bearing to leak when the engine is not running............
The best way to test for a leak is to fire the engine up, and while it is idling and give a shot of nitro spray where you suspect a leak may be...if there is a leak the engine will stall the instant you hit it with nitro spray..........Give a spritz behind the flywheel, see if the engine is drawing vacuum thru the bearing, spray below the barb and by the back plate...be mindful not to hit the airfilter...... So before you start gooping up your engine with silicone, double check to see if the engine actually has a legitimate leak or not.. |
RE: Air Leaks...do you really need to seal your engine ?
That's the age-old wisdom for finding vacuum leaks on full size cars around the intake manifold and carb. Rubber o-rings seal a lot better than other means, but what I've found with many engines is the o-rings shrink with time and don't seal well. I've never seen a manufacture date on any engine I've ever bought so one never knows how long the engine has sat in its box on the shelf. Personally, I prefer to head things off at the pass and lightly seal the backplate and the bottom o-ring on the carb before I even run the engine. Is it really needed? Maybe, maybe not. It hasn't caused me any problems yet. It's not a bad idea when buying a new engine to pull the head and backplate to check for swarf from machining. I've found crud in a few engines, and not just the cheap RTR engines.
Good tip on checking for leaks, Neal. |
RE: Air Leaks...do you really need to seal your engine ?
I have many nitro engines and have worked on many nitro engines. I have never ever had to seal up a nitro engine other than the way it was intended to seal. No goop, no adhesive, no BS. Of coarse most of the engines I purchase are new and higher end engines. I recently purchased a :eek: Dynamite .26 mach 2 for my son. There are a couple guys running these at the track we race at and are getting good results with this engine. I do not consider this a high end engine, in fact, about as cheep as a guy can get. So far it broke in just fine, no extra sealing required.
I did help a friend with an XTM engine once. It ran like crap, tuned like crap, overheated, was inconsistant best case. It did not have much pinch left so I pretty much came to the assumtion it was used up and need pinched or replaced. Maybe it was leaking? I dont know.... How many nitro engines have you come across Neil that do not seal properly? We read, we think, we learn! |
RE: Air Leaks...do you really need to seal your engine ?
Hi All
need some help,what is Nitro spray?Will this work on engines that dont use nitro?My Profi F2a has the burps coming onto the pipe,it may have leak some where,but it only runs on straight fuel,will this nitro spray find the problem area,many thanks in advance. H.W.M |
RE: Air Leaks...do you really need to seal your engine ?
ORIGINAL: HWM77 Hi All need some help,what is Nitro spray?Will this work on engines that dont use nitro?My Profi F2a has the burps coming onto the pipe,it may have leak some where,but it only runs on straight fuel,will this nitro spray find the problem area,many thanks in advance. H.W.M Nitro spray is a cleaner for RC cars that cleans the oily dirty crud off easily. |
RE: Air Leaks...do you really need to seal your engine ?
Here's a thread I made on this a while back with a video on the test in action on an MGT 8.0...
http://www.rcuniverse.com/forum/m_11064920/tm.htm I'm pretty certain on the TT .50 heli engine, it actually is sucking air from the front bearing. The rest of the engine is sealed up, and as soon as I shoot behind the flywheel it dies. People were arguing that the fumes were getting sucked in by the air cleaner and that's why it was dying, so I'm going to get a piece of rubber hose so the air intake is at least a foot away from where I'm spraying. I've already used a piece of cardboard to block any fumes from getting to the air cleaner, but I want to use a sealed rubber hose on the carb for the vid so nobody can say crap about how I tested it. It's now race season so that POS MGT testing is on the back burner. |
RE: Air Leaks...do you really need to seal your engine ?
ORIGINAL: supertib I read on these forums how many people are having tuning issues, and often the first thing people recommend is sealing the engine........many times offering up crazy ideas how to test for a leak...some sensible, some not soo sensible...the craziest one is plugging up the engine and then submerging it under water and blowing into the fuel inlet to see if and where any bubbles escape........This of course is a silly thing to do, as these engines do not use the front bearing to seal the engine... These engines use the hydraulic seal created by the fuel between the crankcase and the crank, and only will seal when the engine is running......it is normal for a front bearing to leak when the engine is not running............ The best way to test for a leak is to fire the engine up, and while it is idling and give a shot of nitro spray where you suspect a leak may be...if there is a leak the engine will stall the instant you hit it with nitro spray..........Give a spritz behind the flywheel, see if the engine is drawing vacuum thru the bearing, spray below the barb and by the back plate...be mindful not to hit the airfilter...... So before you start gooping up your engine with silicone, double check to see if the engine actually has a legitimate leak or not.. |
RE: Air Leaks...do you really need to seal your engine ?
ORIGINAL: HWM77 My Profi F2a has the burps coming onto the pipe,it may have leak some where,but it only runs on straight fuel,will this nitro spray find the problem area,many thanks in advance. Kidding aside, there's very few areas an engine can leak from. With no carb that's eliminated but it could leak from around the plug seat ot plug post although you're probably using a Nelson plug so it's unlikely. Head button seal to the liner is another area and the backplate (I think yours has an O ring seal). What I use to check for any tiny leak is Gas and Air Leak Detector that you can get at any plumbing supply shop. A drop or two on a suspect area will quickly show any leak by foaming when you turn the engine over and hold against compression. It might pay to check all the pipe connections too. That said, I'd guess your "burps" are just from the mixture when it transitions from normal running to the pipe because this type of engine is extremely critical. However I've never flown speed so you'd probably know more about this than I do. |
RE: Air Leaks...do you really need to seal your engine ?
ORIGINAL: nitroexpress ORIGINAL: supertib I read on these forums how many people are having tuning issues, and often the first thing people recommend is sealing the engine........many times offering up crazy ideas how to test for a leak...some sensible, some not soo sensible...the craziest one is plugging up the engine and then submerging it under water and blowing into the fuel inlet to see if and where any bubbles escape........This of course is a silly thing to do, as these engines do not use the front bearing to seal the engine... These engines use the hydraulic seal created by the fuel between the crankcase and the crank, and only will seal when the engine is running......it is normal for a front bearing to leak when the engine is not running............ The best way to test for a leak is to fire the engine up, and while it is idling and give a shot of nitro spray where you suspect a leak may be...if there is a leak the engine will stall the instant you hit it with nitro spray..........Give a spritz behind the flywheel, see if the engine is drawing vacuum thru the bearing, spray below the barb and by the back plate...be mindful not to hit the airfilter...... So before you start gooping up your engine with silicone, double check to see if the engine actually has a legitimate leak or not.. what fuel do you run ? |
RE: Air Leaks...do you really need to seal your engine ?
I've been running car engines since the early 1970's and I have never had to "seal" an engine other than using the gasket and carb "O" ring. I've used engines like the Veco .19 with a clamp on heat sink and the 3.5 cc. These engines had metal shielded front bearings and I have never had bad runs from "air leaks". To this day I can't figure out why the guys out there have to seal their engines. What are you guys doing wrong? even my modern ABC engines don't requiring sealing.
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RE: Air Leaks...do you really need to seal your engine ?
ORIGINAL: controlliner I've been running car engines since the early 1970's and I have never had to ''seal'' an engine other than using the gasket and carb ''O'' ring. I've used engines like the Veco .19 with a clamp on heat sink and the 3.5 cc. These engines had metal shielded front bearings and I have never had bad runs from ''air leaks''. To this day I can't figure out why the guys out there have to seal their engines. What are you guys doing wrong? even my modern ABC engines don't requiring sealing. Spraying something on these little engines to 'test for a leak' is downright stupid, as the majority of the vapor will get sucked into the carburetor and kill the engine anyways. You only use this method to test for leaks on larger (50cc+) two stroke engines, where the carburetor is quite a bit further from the place you're spraying. A quick shot of cleaner will completely engulf the engine in a vapor cloud, you're not being precise enough to test for a leak on an engine that is literally smaller than a baseball. |
RE: Air Leaks...do you really need to seal your engine ?
Hey PROANTI1, Did you ever use the Dick McCoy piston and liner set for the Veco .19? The piston had a Dykes Ring, over sized wrist pin and over bore piston. It made the engine into a .21. Mine used to howl on the Team Associated R/C 500.
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RE: Air Leaks...do you really need to seal your engine ?
ORIGINAL: proanti1 ORIGINAL: controlliner I've been running car engines since the early 1970's and I have never had to ''seal'' an engine other than using the gasket and carb ''O'' ring. I've used engines like the Veco .19 with a clamp on heat sink and the 3.5 cc. These engines had metal shielded front bearings and I have never had bad runs from ''air leaks''. To this day I can't figure out why the guys out there have to seal their engines. What are you guys doing wrong? even my modern ABC engines don't requiring sealing. Spraying something on these little engines to 'test for a leak' is downright stupid, as the majority of the vapor will get sucked into the carburetor and kill the engine anyways. You only use this method to test for leaks on larger (50cc+) two stroke engines, where the carburetor is quite a bit further from the place you're spraying. A quick shot of cleaner will completely engulf the engine in a vapor cloud, you're not being precise enough to test for a leak on an engine that is literally smaller than a baseball. We are able to successfully use the brake cleaner test to diagnose vacuum leaks thru the front bearing......with zero issues of it getting pulled into the airfilter............ it takes quite a big shot for a extended period to do as you are describing.... On all of my engines I can douse the front bearing with brake clean and have no issues with the engine stalling out.........After a decent sized shot I can start make the engine stumble.....But a short burst has zero effect on any of my engines....... But I use a high grade fuel as well as I have taken measures internally to reduce the vacuum present at the front bearing..... |
RE: Air Leaks...do you really need to seal your engine ?
Ive always sealed my motors with rtv - Ive also never had an airleak issue.
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RE: Air Leaks...do you really need to seal your engine ?
I used to get ridiculed for questioning the necessity of sealing engines.. Then all the know-it-alls would gang up and point fingers.. :eek: But partially because so many people have always just repeated the mantra that you need to do it, and partially because well, why not?.., I did it for years, never really had air leaks.. I'm several liters into two new engines now - a Losi 454 and LRP 30, that I didn't bother sealing though, and they're fine.. I also don't seal my buggy engines - and again, fine..
There are a lot of variables with engines and RC generally, so be careful what people tell you on the internet.. You can get good info and sometimes advice, but you need to take all of it with a grain of salt, read between the lines, and ultimately, gather experience yourself. |
RE: Air Leaks...do you really need to seal your engine ?
Electric > stamp collecting, watching grass grow, cleaning room, checking for air leaks, sealing crankcases, breaking in nitro engines, charging receiver batteries, cleaning oily crap off your chassis, going slowly, replacing clutches, never going backwards, pissing everyone off within a kilometer, buying fuel, returning home to your wife stinking of exhaust fumes, ETC
Sorry, couldn't resist. |
RE: Air Leaks...do you really need to seal your engine ?
Like the guys with years of experance said, they never have had any problems with air leaks... so no one els should.....
I can't even say that with out laughing... Personally I would trust the engine builders that have found problems like this. If u have a consistant air leak in the front baring, it still might hold tune and have great preformance. And some guys might never know... The preformance loss could not even be noticed to the naked eye. It would just mean the fuel would not be completly atomised with all the oxygen. |
RE: Air Leaks...do you really need to seal your engine ?
For experienced sprayheads -
<font size="2"> If the spray test depends on spray burst length, what length of bursts are used to determine a problem? Is a slight engine stumble considered OK or does an engine have to die in order to be considered bad. Also, can it be assumed that a tested engine is idling or is it at some elevated RPM? Can it be assumed that the engine has to be up to temperature?</p> </p> Is the type of spray important? Cleaner spray drawn into an engine by normal negative pressure would thin the oil film of a good bearing. Wouldn’t this produce a false reading? Would cleaner spray produce different results than say WD40? Why not spray with a solution which will not combine and thin the lubricating oil? Why not spray with water? Any water drawn inside the engine would quickly evaporate and not cause any problems.</p> If my engine holds tune and has great performance, why should I care if there is a performance loss that can’t be noticed by the naked eye?</p> </p></font> |
RE: Air Leaks...do you really need to seal your engine ?
ORIGINAL: supertib ORIGINAL: proanti1 ORIGINAL: controlliner I've been running car engines since the early 1970's and I have never had to ''seal'' an engine other than using the gasket and carb ''O'' ring. I've used engines like the Veco .19 with a clamp on heat sink and the 3.5 cc. These engines had metal shielded front bearings and I have never had bad runs from ''air leaks''. To this day I can't figure out why the guys out there have to seal their engines. What are you guys doing wrong? even my modern ABC engines don't requiring sealing. Spraying something on these little engines to 'test for a leak' is downright stupid, as the majority of the vapor will get sucked into the carburetor and kill the engine anyways. You only use this method to test for leaks on larger (50cc+) two stroke engines, where the carburetor is quite a bit further from the place you're spraying. A quick shot of cleaner will completely engulf the engine in a vapor cloud, you're not being precise enough to test for a leak on an engine that is literally smaller than a baseball. We are able to successfully use the brake cleaner test to diagnose vacuum leaks thru the front bearing......with zero issues of it getting pulled into the airfilter............ it takes quite a big shot for a extended period to do as you are describing.... On all of my engines I can douse the front bearing with brake clean and have no issues with the engine stalling out.........After a decent sized shot I can start make the engine stumble.....But a short burst has zero effect on any of my engines....... But I use a high grade fuel as well as I have taken measures internally to reduce the vacuum present at the front bearing..... |
RE: Air Leaks...do you really need to seal your engine ?
*gets popcorn*
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RE: Air Leaks...do you really need to seal your engine ?
Popcorn has been in my lap for years.:D
Funny this turned into the same crap that was in my thread... I need to bring home a length of hose so I can locate the opening in the intake of the carb well away from the engine, then apply the spray. It's the same thing us 1:1 tec's do on 1:1 cars, but on a different level, I can spray carb cleaner or any flammable aerosol at a 1:1 engine and watch the o2 sensor readings to determine if the intake system is actually sucking in any "fuel" from that process. Normally they show the results without having to look at readings, the engine bogs out. In our case, the engine is so small that it will die out. One day I'll have the time to prove all of you wrong, until then, watch me suck at racing with a tune that never fails. [youtube]http://www.youtube.com/watch?v=MCzMjUmIZcg[/youtube] |
RE: Air Leaks...do you really need to seal your engine ?
"until then, watch me suck at racing with a tune that never fails. ":D I'm there man, I'm so there. I like that, it reminds me of.......me.:D
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RE: Air Leaks...do you really need to seal your engine ?
i used to use WD-40. a had an old nova .28 that some motor spray sofened the backplate on. it was weird, turned it white- so i just get the red hose on the end and just drip it on..... but to be honest i havent dont that since........ 03'?
nitro racing needs to get back mainstream. theres nothing like a 30 minute main to get you sunburned. |
RE: Air Leaks...do you really need to seal your engine ?
ORIGINAL: proanti1 ORIGINAL: supertib ORIGINAL: proanti1 ORIGINAL: controlliner I've been running car engines since the early 1970's and I have never had to ''seal'' an engine other than using the gasket and carb ''O'' ring. I've used engines like the Veco .19 with a clamp on heat sink and the 3.5 cc. These engines had metal shielded front bearings and I have never had bad runs from ''air leaks''. To this day I can't figure out why the guys out there have to seal their engines. What are you guys doing wrong? even my modern ABC engines don't requiring sealing. Spraying something on these little engines to 'test for a leak' is downright stupid, as the majority of the vapor will get sucked into the carburetor and kill the engine anyways. You only use this method to test for leaks on larger (50cc+) two stroke engines, where the carburetor is quite a bit further from the place you're spraying. A quick shot of cleaner will completely engulf the engine in a vapor cloud, you're not being precise enough to test for a leak on an engine that is literally smaller than a baseball. We are able to successfully use the brake cleaner test to diagnose vacuum leaks thru the front bearing......with zero issues of it getting pulled into the airfilter............ it takes quite a big shot for a extended period to do as you are describing.... On all of my engines I can douse the front bearing with brake clean and have no issues with the engine stalling out.........After a decent sized shot I can start make the engine stumble.....But a short burst has zero effect on any of my engines....... But I use a high grade fuel as well as I have taken measures internally to reduce the vacuum present at the front bearing..... Absolutely incorrect :eek: the bearing can leak like crazy and you will not see a drop of fuel out the front............... Air going in is the worry, fuel dripping out is perfectly normal.......... The vacuum leak is usually from todays thin fuels being unable to make a hydraulic seal between the crankcase and crank, therfore vacuum is present at the front bearing....... and here is what happens when you run on a dirty track with vacuum present at the bearing http://i107.photobucket.com/albums/m...nsbearing2.jpg http://i107.photobucket.com/albums/m...ndbearing1.jpg Brake cleaner is an awesome test , very easy to do, no tube is needed.........it will tell you instantly if your crankcase is sealing properly or not...if its leaking the engine dies instantly...if its sealed the brake cleaner will have no effect..................... Myself, none of my engines stall on the brake cleaner test........Its definitely not rocket science...... give a short little spritz, if engine dies instantly then its breathing thru the front bearing.....Is this OK ? well I guess it depends how clean the air is your running in,...If your running in a dust bowl it will lead to engine wear and damage as the fine dust will be ingested into the engine just as the brake cleaner was..........except fine dust is abrasive, which leads to rapid engine wear................. |
RE: Air Leaks...do you really need to seal your engine ?
ORIGINAL: supertib ORIGINAL: proanti1 ORIGINAL: supertib ORIGINAL: proanti1 ORIGINAL: controlliner I've been running car engines since the early 1970's and I have never had to ''seal'' an engine other than using the gasket and carb ''O'' ring. I've used engines like the Veco .19 with a clamp on heat sink and the 3.5 cc. These engines had metal shielded front bearings and I have never had bad runs from ''air leaks''. To this day I can't figure out why the guys out there have to seal their engines. What are you guys doing wrong? even my modern ABC engines don't requiring sealing. Spraying something on these little engines to 'test for a leak' is downright stupid, as the majority of the vapor will get sucked into the carburetor and kill the engine anyways. You only use this method to test for leaks on larger (50cc+) two stroke engines, where the carburetor is quite a bit further from the place you're spraying. A quick shot of cleaner will completely engulf the engine in a vapor cloud, you're not being precise enough to test for a leak on an engine that is literally smaller than a baseball. We are able to successfully use the brake cleaner test to diagnose vacuum leaks thru the front bearing......with zero issues of it getting pulled into the airfilter............ it takes quite a big shot for a extended period to do as you are describing.... On all of my engines I can douse the front bearing with brake clean and have no issues with the engine stalling out.........After a decent sized shot I can start make the engine stumble.....But a short burst has zero effect on any of my engines....... But I use a high grade fuel as well as I have taken measures internally to reduce the vacuum present at the front bearing..... Absolutely incorrect :eek: the bearing can leak like crazy and you will not see a drop of fuel out the front............... Air going in is the worry, fuel dripping out is perfectly normal.......... The vacuum leak is usually from todays thin fuels being unable to make a hydraulic seal between the crankcase and crank, therfore vacuum is present at the front bearing....... and here is what happens when you run on a dirty track with vacuum present at the bearing http://i107.photobucket.com/albums/m...nsbearing2.jpg http://i107.photobucket.com/albums/m...ndbearing1.jpg Brake cleaner is an awesome test , very easy to do, no tube is needed.........it will tell you instantly if your crankcase is sealing properly or not...if its leaking the engine dies instantly...if its sealed the brake cleaner will have no effect..................... Myself, none of my engines stall on the brake cleaner test........Its definitely not rocket science...... give a short little spritz, if engine dies instantly then its breathing thru the front bearing.....Is this OK ? well I guess it depends how clean the air is your running in,...If your running in a dust bowl it will lead to engine wear and damage as the fine dust will be ingested into the engine just as the brake cleaner was..........except fine dust is abrasive, which leads to rapid engine wear................. |
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