dlegend Posted September 23, 2013 Share Posted September 23, 2013 Well I thought it would be a good idea to add a boost bottle so added one and now it's running worse than ever there's no air leaks at all plug is good too Quote Link to comment Share on other sites More sharing options...
Nitroholic Posted September 24, 2013 Share Posted September 24, 2013 By 'boost bottle' do you mean the red cooler you have on the fuel tank pressure line? If so....take it off again, and see if your running improves. That will at least confirm the part is to blame, and it's not something else doing it. I have never bothered running one of these things TBH. The theory is that is cools the hot exhaust gas that is pressurising the fuel tank and making the fuel flow. This in turn prevents the fuel getting heated up, which is suposed to help with tuning and give a bit more running out of a tank of fuel. Important if you are racing and are a bit marginal on finishing a race...but not something I worry about. I have also not had any tuning issues I could blame on overly warmed up fuel... Assuming all the pipework is sealed and the joints are in good order, it shoudn't cause any problems with running. One thing I can see is that the fuel line to teh carb is right by the 'cooler'. It could be warming that up and giving you a bit of vapour lock. Quote Link to comment Share on other sites More sharing options...
dlegend Posted September 24, 2013 Author Share Posted September 24, 2013 Nooo not the fuel cooler the boost bottle is near the wing it the pipe leading from just below the car up to the wing the fuel cooler works a treat Quote Link to comment Share on other sites More sharing options...
dlegend Posted September 24, 2013 Author Share Posted September 24, 2013 Plus it won't run when cold so that's not an issue the head has only one shim tho to increase compression and volumetric efficiency Quote Link to comment Share on other sites More sharing options...
Nitroholic Posted September 25, 2013 Share Posted September 25, 2013 Oh...yeah...I see it. Best thing to do with that is remove it and throw it away. The science behind a boost bottle is sound enough... The idea is that the increased inlet volume of hte boost bottle helps to damp out pulses in the inlet that are the end result of disc-valve type induction control. The only problem you have, though, is on an RC revving like it does there is no way you can actually flow any gas through the pipe to the bottle and back in the time the valve is cycling. What you get in practice is a drop in crankcase pressure until the system gradually starts to fill up the boost bottle, followed by no effect at all once a bit of pressure builds up in the bottle and the gas won't flow. If you look at the development of 2 stroke racing engines in bikes, they went through similar experimentation....reed valves, resonance chambers, and then settled on power operated variable exhaust valves....but not boost bottles. Quote Link to comment Share on other sites More sharing options...
mugen mark Posted September 25, 2013 Share Posted September 25, 2013 think the fuel coolers where invented for 1 hour finals in the texas/califorina sun,where having a few more seconds a lap,adds up over a hour,but for uk use,more bling,than win Quote Link to comment Share on other sites More sharing options...
dlegend Posted September 25, 2013 Author Share Posted September 25, 2013 It's basically on there for the being factor the cooler well I think I'll add 1more shim to the head and try once more then il bin it Quote Link to comment Share on other sites More sharing options...
Anthoop Posted September 25, 2013 Share Posted September 25, 2013 Oh...yeah...I see it. Best thing to do with that is remove it and throw it away. The science behind a boost bottle is sound enough... The idea is that the increased inlet volume of hte boost bottle helps to damp out pulses in the inlet that are the end result of disc-valve type induction control. The only problem you have, though, is on an RC revving like it does there is no way you can actually flow any gas through the pipe to the bottle and back in the time the valve is cycling. What you get in practice is a drop in crankcase pressure until the system gradually starts to fill up the boost bottle, followed by no effect at all once a bit of pressure builds up in the bottle and the gas won't flow. If you look at the development of 2 stroke racing engines in bikes, they went through similar experimentation....reed valves, resonance chambers, and then settled on power operated variable exhaust valves....but not boost bottles. Boost bottles were not designed specifically for rotary induction, in fact probably the most used motorcycle system was on a reed valve engine. Boost bottles were widely used in MC racing on/off road in conjunction with exhaust valves, not as a replacement. There is no effect of fill up or crankcase pressure changes because the bottle is vented behind the rotor or reed valves. The theory is that the bottle retains some of the atomised fuel when the rotor/reeds close, it improves throttle response if implemented correctly. I attest that boost bottles do work as I have done back to back tests with the system open and plugged....but I am talking about being able to feel a very minor change on throttle response on a 350cc bike! For RC engines my opinion is that they are pointless because even if you worked out the volume required you would never even notice the change. Quote Link to comment Share on other sites More sharing options...
Nitroholic Posted September 25, 2013 Share Posted September 25, 2013 One question....if there is no pressure... why does any fuel mix actually travel to the boost bottle? It's a closed system. Has to be... The piston is providing the negative crankcase pressure to draw fuel in....but unless you have positive crankcase pressure during the valve overlap, what is going to make mixture go anywhere else? Not arguing...just keen to fill a knowlege gap! Quote Link to comment Share on other sites More sharing options...
dlegend Posted September 25, 2013 Author Share Posted September 25, 2013 Well as the crank is spinning it will a positive pressure as it will create a swirly effect due to it running g clockwise(rear facing view) causing the crank to throw fuel into the oulet of the crank the the negative pressure would create a swirly effect forcing it to the bottle I could be wrong I'm pretty baked atm Quote Link to comment Share on other sites More sharing options...
Anthoop Posted September 26, 2013 Share Posted September 26, 2013 (edited) One question....if there is no pressure... why does any fuel mix actually travel to the boost bottle? It's a closed system. Has to be... The piston is providing the negative crankcase pressure to draw fuel in....but unless you have positive crankcase pressure during the valve overlap, what is going to make mixture go anywhere else? Not arguing...just keen to fill a knowlege gap! If we picture the mixture flowing through the crank window (rotor), when it closes then the flow does not stop immediately, air is still being drawn through the carb. and drawing fuel for a moment but the window is closed. When the window opens again the air has to be drawn through the carb. and fuel drawn....with the boost bottle the fuel is already mixed and waiting to go.....so the mixture is drawn (or whatever is in the bottle is drawn (maybe just air the first time)) leaving a vaccuum that will be filled when the window closes again... Yes of course there has to be negative pressure in the crankcase in the first place...but the boost bottle does not affect or alter it because the drilling is not in the crankcase but above the window and below the carb. Make sense? Edited September 26, 2013 by Anthoop Quote Link to comment Share on other sites More sharing options...
Nitroholic Posted September 26, 2013 Share Posted September 26, 2013 Makes sense...but that is only going to work if the boost chamber or bottle is really close to the intake....the residual pressure from the inlet won't be there for long or be that great. It's never going to work with a long thin pipe ( as in the OP setup) for example. Doubly so at the revs a little nitro motor is running at. Scale it up, mount the boost bottle directly to the inlet with a decent sized bore on the entry, and I can see it would smooth the inlet pulses. I can also see why road bikes never bothered with it. Unless you are running fairly radical inlet timing, the gains will be tiny compared to the potential for leaks etc. Quote Link to comment Share on other sites More sharing options...
Anthoop Posted September 27, 2013 Share Posted September 27, 2013 Makes sense...but that is only going to work if the boost chamber or bottle is really close to the intake....the residual pressure from the inlet won't be there for long or be that great. It's never going to work with a long thin pipe ( as in the OP setup) for example. Doubly so at the revs a little nitro motor is running at. Quite true. The length and bore of the pipe are very important as is the volume of the bottle and the overall volume.....and the mounting position. As I said my opinion is that for RC it is pointless but also I do not think that the set-up we see here would cause any problems...so long as there are no leaks...pointless but harmless. Quote Link to comment Share on other sites More sharing options...
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