Tony Posted June 3, 2007 Report Share Posted June 3, 2007 I understand that compression without ignition causes a hydrologic situation but i fail to understand a definitive reason why! Is this mainly due to timing?.... Often after an engine explosion the reason is directed at the "magneto (s)". How can this be? Any explanation would be very appreciated. Quote Link to comment Share on other sites More sharing options...
Sam@TDi Posted June 4, 2007 Report Share Posted June 4, 2007 Nitro engines Ok, to be competitive in Top Fuel these days you need to be running over 90% Nitro (that is 90% Nitro &10% Methanol)... One of the reasons Nitromethane is such a powerful fuel is because it's stoichiometric ratio is around 5:1, this means that the chemically perfect (or Lambda) ratio for combining Nitro and atmospheric air is 5 parts air and 1 part pure liquid Nitro, to give you some idea about how rich that is the stoichiometric ratio of normal road unleaded fuel is 14.7:1 If you run internal combustion engines at stoichiometric or lambda 1.00 the lack of any excess fuel in the upper cylinder produces a harsh and hot environment (although the lack of unburnt fuel is great for emissions). In order to keep combustion “controlled†and reduce detonation probability we deliberately over fuel any engine under high load conditions such as full throttle, often in petrol engines looking for 12:1 or 11:1 The same applies to a nitro engine so when running extreme loads, extreme rpm’s, extreme boost pressures and compression ratios the teams need to really richen these engines up in order to prevent the dreaded detonation. This results in Top Fuel engines regularly running afr’s as low as 3:1 or even 2:1… in either case that is an awful lot of liquid Nitro to ignite, especially as the stuff is pretty much inert unless pressurized. The problem comes when the 2 spark plugs and the 2 50amp magneto’s fail to start a fire, the piston has the almost impossible job of trying to expel all of that liquid nitro through one exhaust port. Top Fuel dragsters run ridiculous camshaft duration and what normally happens is that a lot of the liquid nitro stays in the exhaust header then is sucked back into the cylinder through the exhaust port during the valve overlap period for the next induction stroke. This then leaves you with a cylinder totally over full with liquid Nitro for the next compression stroke, the engine will inevitably attempt the compress the mixture and when it does………… Basically the unstoppable force meets the unmovable object! Quote Link to comment Share on other sites More sharing options...
Tony Posted June 4, 2007 Author Report Share Posted June 4, 2007 Thank you for that explanation Sam@tdi..... You know your engines don't you!! I now actually understand the reason why there is a problem and that it seems impossible this problem will ever "go away". I think you would agree that an engine numpty like me would be puzzled why such an advanced area like top-fuel there could be a window of chance for such an absolute failure..... Now i know Quote Link to comment Share on other sites More sharing options...
jon Posted June 4, 2007 Report Share Posted June 4, 2007 I can only think of one word. Sweet. Quote Link to comment Share on other sites More sharing options...
Sam@TDi Posted June 5, 2007 Report Share Posted June 5, 2007 Cool glad that made sense. For what it's worth the problem is totally fixable, the Top Fuel regulations frustrate me massively :worried_anim: It's like the rule makers at the NHRA are a bunch of redneck technophobes or something, some of the rules are as follows; Competitors must use a Hemi derivative engine or custom built racing version but it must be to the original hemi design (1950's) No electronic engine management allowed, i.e. Mechanical fuel injection and locked ignition advance at 50degree'sNo electronic clutch management or launch control, i.e. must use dozens of complicated timed hydraulic actuators and multi lever clutch assembly's Because of these arcane rules the only electronics allowed on the car are for data logging purposes which has now become the single most important area of the entire sport, with each 1/4 mile run costing well over £2000 even if nothing breaks! learning as much as possable from run to run is crucial. Personally I say take the brakes off the development, let the mechanics have their head and the sport will improve. We would see multivalve dohc engines straight away for sure, the electronic engine management would be able to control some injectors for methanol and others for nitro meaning that the nitro percentage could be altered throughout the entire time the engines running - this would seriously improve reliability. The engine management could quite literally cure the problem of hydraulic'ing the motor by monitoring individual cylinder egt's and when it senses a non-fire by the temp drop it could tell the injectors for that cylinder only to miss a beat... I'm not going to even go into the serious benefits that mapped ignition advance would bring Quote Link to comment Share on other sites More sharing options...
Tony Posted June 8, 2007 Author Report Share Posted June 8, 2007 I'm not going to even go into the serious benefits that mapped ignition advance would bring Oh please do..... Your explanation has been "saleable" don't stop now Quote Link to comment Share on other sites More sharing options...
jon Posted June 8, 2007 Report Share Posted June 8, 2007 An owner on the 350 boards just fell to hydrolocking after driving through a big puddle Poor chap. Quote Link to comment Share on other sites More sharing options...
Tony Posted June 8, 2007 Author Report Share Posted June 8, 2007 An owner on the 350 boards just fell to hydrolocking after driving through a big puddle Poor chap. Puddle?...... How come. Did this cause a misfire then hydraulic? Quote Link to comment Share on other sites More sharing options...
jon Posted June 8, 2007 Report Share Posted June 8, 2007 Sorry, should have been "puddle". About 3 foot deep, god knows why he tried to drive through it. Water in the stock induction kit. Bang. Quote Link to comment Share on other sites More sharing options...
Tony Posted June 8, 2007 Author Report Share Posted June 8, 2007 Sorry, should have been "puddle". About 3 foot deep, god knows why he tried to drive through it. Water in the stock induction kit. Bang. Ooops. My thoughts do out to the friends and family. Quote Link to comment Share on other sites More sharing options...
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