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Savage half tank EXTREME lean problem.

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Savage half tank EXTREME lean problem.

Old 08-06-2011, 03:30 PM
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Sigma.40
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Default Savage half tank EXTREME lean problem.

People are probably getting tired of my Savage tuning questions but I don't trust my LHS guy and I have no one else to ask so I am sorry . Here we go:

I thought that I had my Savage 4.6 dialed in but I am questioning that now. I ran it today in a dirt field with 5-8ft tall dirt piles. As alwaysthe first half tank was perfect. Power was great and my temps were 237F. At 1/2 tank the truck wants to shut off. After I restarted it, I continued running it. It still had the same amount of power but when I went through the 2nd 1/2 tank my temps were 317F. I know about the half tank lean problem, but that seems extreme. I never hit WOT (mostly 1/2 to 3/4 throttle) and there was always some amount of blue smoke. My questions are:

-What should I do if the 1st half tank is perfect but the 2nd half tank is very lean?

-Why does the truck almost alwaysshut off at exactly 1/2 tank?

-Is it likely that I damaged the engine by hitting 317F?

As always, thanks in advance!
Old 08-06-2011, 03:54 PM
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Default RE: Savage half tank EXTREME lean problem.

http://www.rcuniverse.com/forum/forumid_250/tt.htm
Lots of people have had that issue
There are a few creative ways to get rid of it in the HPI forum.
Some people say tune it at half a tank. Personally I've not noticed the half tank lean on mine.
best fix I seen which also moves the tank is the mid tank mod. I forgot the exacts (the instructions are somewhere in the HPI forums) but it involves modifying the radio box, and mounting an ofna tank there.
Old 08-06-2011, 06:15 PM
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Default RE: Savage half tank EXTREME lean problem.

I just read that shortening my fuel lines will help. Maybe I'll try that first.
Old 08-06-2011, 06:30 PM
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Default RE: Savage half tank EXTREME lean problem.

I like this one:

http://www.rcuniverse.com/forum/m_7430203/tm.htm
Old 08-08-2011, 05:38 PM
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Default RE: Savage half tank EXTREME lean problem.

i put a 2oz header tank on my truck. the small tank feeds from the main tank, but it keeps consistent pressure, and as a bonus, you get more run time
its zip tied in behind the main tank
Old 08-08-2011, 11:57 PM
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Default RE: Savage half tank EXTREME lean problem.

The temperature itself is NOT what damages an engine. It's all steel, brass, chrome, and aluminum. There's nothing in there that would simply be damaged by temperature. The only reason your engine will be damaged is if the head button or the piston are pitted from detonation. If it was detonating, then fear engine damage. If it wasn't detonating, then don't sweat it.
Old 08-09-2011, 06:00 PM
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Default RE: Savage half tank EXTREME lean problem.

Ive been told for thirty years that heat changes tolerance meaures and causes weakening of metals and uneven wear. if thats off then why does my car need fluid to heck with coolant its too expensive. are you saying an rc engine will run at 600 degrees with no failure?

The double tank method is unbeatable. Its the best way for sure.
Old 08-09-2011, 06:37 PM
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Default RE: Savage half tank EXTREME lean problem.


ORIGINAL: brandon429

Ive been told for thirty years that heat changes tolerance meaures and causes weakening of metals and uneven wear. if thats off then why does my car need fluid to heck with coolant its too expensive. are you saying an rc engine will run at 600 degrees with no failure?

The double tank method is unbeatable. Its the best way for sure.
The difference between running 320 degrees and 290 degrees is going to be negligible. Do you want him to rush out and buy a new engine just because he had a little high temperature spike? Jeez

320 degrees is not enough to hurt anything inside the engine. Period. Prove ThunderbirdJunkie wrong. With science, not a bunch of horsecrap spouted by "experts".
Old 08-09-2011, 08:08 PM
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Default RE: Savage half tank EXTREME lean problem.


ORIGINAL: nitro stan

i put a 2oz header tank on my truck. the small tank feeds from the main tank, but it keeps consistent pressure, and as a bonus, you get more run time
its zip tied in behind the main tank
I have heard that this works, but why (probably a stupid question) is the fuel line to the carb on the top of the header tank? As the fuel gets low wouldn't it cause issues trying to push the fuel up through the fuel cap?

Old 08-10-2011, 02:10 AM
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Default RE: Savage half tank EXTREME lean problem.


ORIGINAL: Sigma.40


ORIGINAL: nitro stan

i put a 2oz header tank on my truck. the small tank feeds from the main tank, but it keeps consistent pressure, and as a bonus, you get more run time
its zip tied in behind the main tank
I have heard that this works, but why (probably a stupid question) is the fuel line to the carb on the top of the header tank? As the fuel gets low wouldn't it cause issues trying to push the fuel up through the fuel cap?

There's a clunk inside the header tank that picks fuel up from the bottom. If you mounted the header tank horizontally it would still pull fuel when the truck is on it's lid too!
ORIGINAL: brandon429

Ive been told for thirty years that heat changes tolerance meaures and causes weakening of metals and uneven wear. if thats off then why does my car need fluid to heck with coolant its too expensive. are you saying an rc engine will run at 600 degrees with no failure?
.
The difference is in the engine construction. Your car's engine relies on ring tension to get compression. Get the rings hot enough and they lose this tension. When they do that, they can no longer seal. On top of that, your car's engine has one head on multiple cylinders, get that hot enough and it will warp.

Your RC engine does not have these issues. You can get that thing as hot as you want to. The worst thing that will happen is that it just shuts off. When it cools off it will start right back up and run just fine provided you didn't melt the seals in the carb. The reason we have a temp limit for our RC engines is because that's the temp where the cylinder gets approximately perfectly cylindrical and so that it doesn't boil the fuel when it hits the crankshaft.
Old 08-10-2011, 03:04 AM
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nitro stan
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Default RE: Savage half tank EXTREME lean problem.

it works because the pressure in the smaller tank stays consistent, the tank in a constant shape.
there is a clunk in the tank, but it don't have enough room to move around much with it standing up. its about a inch and a half wide, the inlet fuel line with clunk is 2 inches long and it is regular fuel line, so its kinda stiff. laying on its side it would probably run upside down, thats how people mount them in planes.

both lines come in side by side, one has the clunk and goes to the bottom, this one goes to your carb. one is cut off and the inside of the cap, its the inlet, hook it to the outlet of the main tank
Old 08-12-2011, 04:11 PM
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Default RE: Savage half tank EXTREME lean problem.

I got a small fuel tank but I am wondering where is best to put it as I don't have the space that nitrostan does. There are 4 spots that I can fit it so I took a picture of each so you all can help me figure out where to put it.

- Onespot ison the radio box. Pros: Flat and secure Cons: A hell of alot of fuel line

- One spot is laying horizontal behind the rear shock tower. Pros: the tank is flat (which is how it is designed to be). Cons: shocks may get in the way of lines.

- One spot is laying vertical behind the rear shock tower. Pros: very secure and plenty of room for the fuel lines. Cons: fuel has to go up the tank (not sure if this will cause issues)

-The last spot is behind the rear bumper. Pros: It fits perfectly and is VERY secure. Cons: Tank would be lower than the carb so the fuel lines would go up.

If it doesn't matter if the tank is vertical, I think standing up behind the shock tower would be best other wise I am leaning towards putting it on the radio boxbut I am not sure. Would love opinions. Thanks guys.
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Old 08-13-2011, 05:35 AM
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Default RE: Savage half tank EXTREME lean problem.

I absolutely love fitting it into the back bumper. Since we run a pressurized fuel system I don't think it will matter much that the tank is below the carb...matter of fact, most on-roads are set up that way. My entire tank is below my carb, my pickup just more or less the thickness of the tank wall above the chassis itself, and I don't have any fuel feed issues.


If you can sort the lines, use position two though. You'll get a good five or ten minutes to get to it if it goes onto it's lid that way.
Old 08-13-2011, 06:07 AM
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Default RE: Savage half tank EXTREME lean problem.


ORIGINAL: 378


If you can sort the lines, use position two though. You'll get a good five or ten minutes to get to it if it goes onto it's lid that way.
Why would it run longer if its horizontal behind the rear shock tower?
Old 08-13-2011, 06:09 AM
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Default RE: Savage half tank EXTREME lean problem.

There's a clunk on the end of some fuel line inside that airplane tank. Mounted horizontally, as it would be in an aircraft of some sort, this clunk will stay in the fuel when the truck flips over, allowing the engine to draw from the header tank while you walk over to it and flip it back over. Aircraft need this because they fly inverted and require fuel flow while doing so.
Old 08-13-2011, 06:19 AM
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Default RE: Savage half tank EXTREME lean problem.


ORIGINAL: 378

There's a clunk on the end of some fuel line inside that airplane tank. Mounted horizontally, as it would be in an aircraft of some sort, this clunk will stay in the fuel when the truck flips over, allowing the engine to draw from the header tank while you walk over to it and flip it back over. Aircraft need this because they fly inverted and require fuel flow while doing so.
I did not put the clunk in the tank since the guy at the LHS said it wouldn't be needed. Its just2 brass tubesgoing into the tank (1 shorter to let fuel in and 1 that goes to the bottom to let fuel to the carb)and those are connected to the rubber fuel lines. Do you think that I need the clunk?
Old 08-13-2011, 06:27 AM
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Default RE: Savage half tank EXTREME lean problem.

You don't need the clunk, but if you can mount the tank horizontally and want to be able to mosey over to it at your own pace after it rolls over, then install the clunk. IF you're gonna mount it vertically don't bother, as the clunk will do no good in that situation.
Old 08-13-2011, 06:39 AM
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Default RE: Savage half tank EXTREME lean problem.



I just figured out how to mount it horizontally, it just needs longer fuel lines. Thanks 378, you are helpful as always.

-I'm probably up to owing you, what, 2 or 3 gallons of glow by now ? The 8ight 2.0 runs awesome btw.

Old 08-13-2011, 06:54 AM
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Default RE: Savage half tank EXTREME lean problem.

ORIGINAL: ThunderbirdJunkie


ORIGINAL: brandon429

Ive been told for thirty years that heat changes tolerance meaures and causes weakening of metals and uneven wear. if thats off then why does my car need fluid to heck with coolant its too expensive. are you saying an rc engine will run at 600 degrees with no failure?

The double tank method is unbeatable. Its the best way for sure.
The difference between running 320 degrees and 290 degrees is going to be negligible. Do you want him to rush out and buy a new engine just because he had a little high temperature spike? Jeez

320 degrees is not enough to hurt anything inside the engine. Period. Prove ThunderbirdJunkie wrong. With science, not a bunch of horsecrap spouted by ''experts''.
320 for a few minutes may not be enough to really hurt an engine, but saying temperature doesn't damage an engine at all? That's just stupid. "Dispersion" is when aluminum expands when its annealed, and is then rubbed off onto other surfaces. This can happen at 300 degrees. The pistons in RC engines are generally a really hard aluminum-silicon alloy, which resists this wear, but it can still happen. Brass takes on a full anneal at about 450 degrees, but still softens enough to lose its shape long before then... which results in a lost pinch.

320 is too hot for one of these engines. Metal doesn't have to get to its melting point before it deforms.
Old 08-13-2011, 07:36 AM
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Default RE: Savage half tank EXTREME lean problem.


ORIGINAL: proanti1

320 for a few minutes may not be enough to really hurt an engine, but saying temperature doesn't damage an engine at all? That's just stupid. ''Dispersion'' is when aluminum expands when its annealed, and is then rubbed off onto other surfaces. This can happen at 300 degrees. The pistons in RC engines are generally a really hard aluminum-silicon alloy, which resists this wear, but it can still happen. Brass takes on a full anneal at about 450 degrees, but still softens enough to lose its shape long before then... which results in a lost pinch.

320 is too hot for one of these engines. Metal doesn't have to get to its melting point before it deforms.
I wouldn't argue with those scientific facts, but I did accidently run a buggy engine up to 400degF once and no ill effects (that I could tell). I did notice one of my engines detonating once, and the temp was about 320. I like keeping the engine under 300 just because of that. I don't want detonation.

I don't normally liek to quote things that I havn't personally experienced, but I understand that they do run airplane engines around 400degF. I suspect the different fuel lets them get away with that as far as detonation is concerned, but if that is true, I havn't heard about any metal parts becoming deformed.

Any comments from someone who knows more than me about this?
Old 08-13-2011, 09:02 AM
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Default RE: Savage half tank EXTREME lean problem.

Airplane fuel has bucketloads of oil in it, sometimes up to 20%. On top of that, a good half that is usually castor. Then, they tend to run lower nitro %, my OS 46AX is rated 10-20% nitro whereas my 18 CV-RX is rated 20-30%. Lastly, a lot of plane guys run 0% or 5% nitro to save money. When you run FAI fuel you require a hotter plug to keep it lit, so an engine that detonated on 10% nitro purrs like a kitten on FAI or 5%.


So yeah, they're much less prone to detonating, and the extra oil pulls the heat away from the engine internals. The glow plug may read a higher temp, but they don't mind it at all.


It's also worth noting the constant flow of fan-fed air that helps keep them cool. Cowled engines will run hot if not baffled properly, but in one that's exposed, like in my NexSTAR, it's nigh impossible to overheat it provided it's tuned properly and not leaking air. If it gets hot just crack the throttle open


As for running aircraft fuel in our cars, while they will run, they'll be down on power and they will make a royal mess. I'd only advise it if you absolutely need to flood that much oil through, as for example someone living in the desert or someone who needs to get every last revolution of useful life out of their engine due to financial restraints. I would also advise it to anyone running a four stroke, as these are always a converted aircraft engine and require the extra lube.
ORIGINAL: Sigma.40



I just figured out how to mount it horizontally, it just needs longer fuel lines. Thanks 378, you are helpful as always.

-I'm probably up to owing you, what, 2 or 3 gallons of glow by now ?
Hahahaha, perhaps. I lost count myself.
The 8ight 2.0 runs awesome btw.

Excellent. It will continue to do so for a while yet, as well.
Old 08-13-2011, 09:16 AM
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Default RE: Savage half tank EXTREME lean problem.


ORIGINAL: Argess


ORIGINAL: proanti1

320 for a few minutes may not be enough to really hurt an engine, but saying temperature doesn't damage an engine at all? That's just stupid. ''Dispersion'' is when aluminum expands when its annealed, and is then rubbed off onto other surfaces. This can happen at 300 degrees. The pistons in RC engines are generally a really hard aluminum-silicon alloy, which resists this wear, but it can still happen. Brass takes on a full anneal at about 450 degrees, but still softens enough to lose its shape long before then... which results in a lost pinch.

320 is too hot for one of these engines. Metal doesn't have to get to its melting point before it deforms.
I wouldn't argue with those scientific facts, but I did accidently run a buggy engine up to 400degF once and no ill effects (that I could tell). I did notice one of my engines detonating once, and the temp was about 320. I like keeping the engine under 300 just because of that. I don't want detonation.

I don't normally liek to quote things that I havn't personally experienced, but I understand that they do run airplane engines around 400degF. I suspect the different fuel lets them get away with that as far as detonation is concerned, but if that is true, I havn't heard about any metal parts becoming deformed.

Any comments from someone who knows more than me about this?
400?... Every one I have ever run has stayed around 200, including the 4 strokes which are notorious for running hot.
Old 08-13-2011, 10:18 AM
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Default RE: Savage half tank EXTREME lean problem.


ORIGINAL: proanti1

ORIGINAL: ThunderbirdJunkie


ORIGINAL: brandon429

Ive been told for thirty years that heat changes tolerance meaures and causes weakening of metals and uneven wear. if thats off then why does my car need fluid to heck with coolant its too expensive. are you saying an rc engine will run at 600 degrees with no failure?

The double tank method is unbeatable. Its the best way for sure.
The difference between running 320 degrees and 290 degrees is going to be negligible. Do you want him to rush out and buy a new engine just because he had a little high temperature spike? Jeez

320 degrees is not enough to hurt anything inside the engine. Period. Prove ThunderbirdJunkie wrong. With science, not a bunch of horsecrap spouted by ''experts''.
320 for a few minutes may not be enough to really hurt an engine, but saying temperature doesn't damage an engine at all? That's just stupid. ''Dispersion'' is when aluminum expands when its annealed, and is then rubbed off onto other surfaces. This can happen at 300 degrees. The pistons in RC engines are generally a really hard aluminum-silicon alloy, which resists this wear, but it can still happen. Brass takes on a full anneal at about 450 degrees, but still softens enough to lose its shape long before then... which results in a lost pinch.

320 is too hot for one of these engines. Metal doesn't have to get to its melting point before it deforms.
Thank you for an actual concise and well-reasoned explanation to high temperatures damaging engines. This makes a lot more sense than "OMG UR GONA BLOW UR ENJUN!!!!1"
Old 08-13-2011, 12:14 PM
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Default RE: Savage half tank EXTREME lean problem.


ORIGINAL: Argess


ORIGINAL: proanti1

320 for a few minutes may not be enough to really hurt an engine, but saying temperature doesn't damage an engine at all? That's just stupid. ''Dispersion'' is when aluminum expands when its annealed, and is then rubbed off onto other surfaces. This can happen at 300 degrees. The pistons in RC engines are generally a really hard aluminum-silicon alloy, which resists this wear, but it can still happen. Brass takes on a full anneal at about 450 degrees, but still softens enough to lose its shape long before then... which results in a lost pinch.

320 is too hot for one of these engines. Metal doesn't have to get to its melting point before it deforms.
I wouldn't argue with those scientific facts, but I did accidently run a buggy engine up to 400degF once and no ill effects (that I could tell). I did notice one of my engines detonating once, and the temp was about 320. I like keeping the engine under 300 just because of that. I don't want detonation.

I don't normally liek to quote things that I havn't personally experienced, but I understand that they do run airplane engines around 400degF. I suspect the different fuel lets them get away with that as far as detonation is concerned, but if that is true, I havn't heard about any metal parts becoming deformed.

Any comments from someone who knows more than me about this?
How do I tell if the engine is detonating?
Old 08-13-2011, 12:15 PM
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Default RE: Savage half tank EXTREME lean problem.

It will be down on power, it will be making strange popping noises, and when you pull the head you'll see all sorts of tiny little dents/pits in both it and the top of the piston. The glow plug will also show evidence, pitting on the bit that sticks into the chamber and the element will be deformed.

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