why is bad to rev an engine higher than the redline
gamefisher,
Dec 31, 11:19pm
Cost money& lot of it
gsimpson,
Jan 1, 5:45am
Parts of the engine might start exiting through the side of the block or down through the sump.
intrade,
Jan 1, 6:49am
because after red line comes the rev limitter. and if that dont exists valve bounce would be next to come. Valve bounce is when the piston is faster then the valve it bounces it closed because its all about physic why do you think 2 strokers can rev 12 to 18,000rpm because they have no phisical springs boincing abouts a spring is closing the valve on a 4 stroke , this spring can only phisically do it this and that fast. Now a desmo system was supposed to overcome that spring -valve bounce only problem is physic also broke the arm whom was suposed to close the valve , if a mass is to heavy and is catapulted fast in one direction it becomes a imense force think bullets out of guns.
lookoutas,
Jan 1, 7:18am
Far-out!
skull,
Jan 1, 7:25am
I don't think valve bounce normally involves the pistons, it is when the spring has not returned the valve to the valve seat before the cam is trying to open it again. The noise is the valve opening mechanism hitting the end of the valve stem to open it up again while it is still returning to the seated position.
intrade,
Jan 1, 7:35am
there is good discription in wikipedia i just found https://en.wikipedia.org/wiki/Valve_float if the valve reopens and the engine is enterfearance then what do you think the piston is doing? it smacks the valve shut . its why engeneers put rev limmiter in engines not so some woppyweed dophead can go and remove it to make his car go faster. yea it will go faster question is for how much longer.
kevymtnz,
Jan 1, 7:44am
red line is a guide engine peak power pending engine eg red line might be 6,500rpm but PP might be 6,250rpm so after that power is decreasing so ultimately once PP is reached next higher gear is needed once valve bounce a cures valve seals begin to be damaged just follow a boy racer you can smell that its been over revved
intrade,
Jan 1, 7:51am
i can take this further for you "chip tuning". manufacturer make a engine with 115hp with 130 hp and 150hp difference is the tuneing of the engine. You can tune the 115hp one to 160 hp , there is however 1 danger was the engine internally built to the same specs as the 150hp one? maybe maybe not. Unless you know what the differences are you risk the premature death of your engine by tuning it past what it was built for. this above is actuarly the engine type i have in my vw it comes as 115hp-130-150hp i own the 130 version so what is different internally its the same as the 150 engine - externally it has a smaller intercooler, so i had to look at what can i do and i found a fix , the intercooler has poor airflow in the wheel arch so i added a better airflow like audi Q7 have , this mod brings it close enough to what the larger cooler is doing on the 150 engine . the 115bhp engine it has not the same conrods so you dont want to go and tune that past the 150 mark Or you do and it blows up and then you say ah that vw crap they dont build good cars, No your brain is crap you dont think and research and understand things . That is the problem not vw is crap the crap resides in the brain.
intrade,
Jan 1, 8:08am
yes thats the top of the valve when the spring is forced to compress so far by the gravitational force from what the valve waighs , it bottoms out on to the valve stem seal smashing against top of the seal correct.
mark.52,
Jan 1, 8:29am
There are usually two reasons for a maximum rpm in an engine. 1) Ability of the parts to disperse the heat produced into the coolant, and the ability of the cooling system to dissipate that heat.
In effect, the bits of the engine that get very hot in normal operation might become very hot indeed in extreme operation - to the point where they might deform.
2) Mechanical limitation. (Includes the info on valve bounce in several above posts.)
Engines are designed to hold together at normal speeds and up to a good margin above what the engineers have determined is an appropriate maximum rpm. Stresses on the rotating bits (especially bits that are fair thrashing around and have a lot of stress on them, such as con-rods) might increase to beyond their ability to hold together if the redline is seriously exceeded.
Modern cooling systems are fairly good. Max rpm is usually determined by the second factor. In aircraft piston engines it's often the cooling factor. My old lawnmower died following a governor disconnect which allowed it to overspeed - the con rod broke. Noisily.
intrade,
Jan 1, 8:29am
https://www.youtube.com/watch?v=ocfIYUc5bpU this is the desmo system in theory the ultimate designe in practice gravitational phisics is braking apart the arm at higher rpm. i did read a article of the desomo system and why its flawed phisics are the problem no one can change the law of physical actions causing a reaction. I think today with ultra light super strong materials the desmo system could be used to overcome valve bounce without braking the arm, because you need less waight the faster a waight goes the more forces you need to stop it. the thing is true the faster you go the bigger the mess , yes if you impact at full speed it will be true but only then it becomes true.
intrade,
Jan 1, 8:36am
lets go and analyse the faster you go the bigger the mess? its not the faster you go, its the lack of time you have to slow down again that kills you not the speed your going at. if you impact at full speed how much time do you have to slow down? 0 zero time right. so what killed you the speed you where doing, no the moron who did not apply the brake soon enough is what killed you. the garitational force of slowing a object need to be absorbed the brakes will do that and disepate the energy in to heat . if you did not use the brake then the car will have to absorb it in the crumble zone and the 100 tousend airbags try to absorb all that energy and if it exeeds tha capabilty to absorb it then you absorb the full rest of the energy. and you absorb some of it anyhow . because your brain was to slow to get the brake system to absorb the energy for you. but hey! speed kills . i say go to friggen phisyc class in scool speed dont kills!
intrade,
Jan 1, 9:31am
now we diviated or i did off the subject slightly but that is the big picture of why there is a red line. Now if your a boy racer you just reomove the rpm meter whom redlined at 6500rpm and fit one that redlines at 8500 rpm right that will fix it wont it?
mals69,
Jan 1, 9:39am
Its how you lessen the noise of the lifters on an 80's leone
yz490,
Jan 1, 9:51am
paint the red line 'green', everything's going green these days.!
lusty9,
Jan 1, 9:59am
hahaha that's a good one. Red stop, green go.
mojo49,
Jan 1, 10:50am
The valve bounce problem started when engines began to rev to a level where the frequency of the valves opening and closing matched the harmonic frequency of the valve spring. At that revs the spring becomes ineffective as it is spontaneously compressing and expanding. The problem was overcome by adding a second smaller internal spring with a different harmonic frequency. Eventually engine technology overtook that cure and ideas like the desmo system were developed. They ran into the issue of the material having too much mass and not enough strength to withstand the forces of being moved up and down at high frequency by the camshaft and therefore breaking. Not up to date with the technology of how they get F1 engines to rev at such extreme levels.
mrcat1,
Jan 1, 10:55am
Trust me, you can get a lot more out of a 2 stroke than 12-18000 rpm, you can get 24000rpm out of a chainsaw quite easily as long as it doesn't have a limiter.
neell,
Jan 1, 11:30am
You can also get 4 stroke engines that can do 20,000+rpm but they are expensive.
ozz1,
Jan 1, 1:17pm
or you could also replace the oil pump seal. on ea82 leone motors.
mals69,
Jan 1, 3:17pm
True - its what a turners auction guy told me they did back in the day
gs1220,
Jan 1, 6:01pm
The problem with over-reving is that the acceleration forces as the piston direction changes increase with increasing revs and, at high enough revs, will exceed the connecting rod strength. The rod will pull apart, thrash around and, as gsimpson said, poke a hole in the block. Valve bounce will limit the maximum revs possible because, at high enough revs, the valve springs don't fully close the valves, the valves "float", so compression is lost, so the engine efficiency is less than ideal and it doesn't go any faster. If you want high revs (getting high power) you need strong valve springs and strong reciprocating parts: con-rods, pistons, valves.
ianab,
Jan 1, 8:16pm
Like the folks are saying, if you run an engine at higher revs than it's designed to, you exceed the design specs of the individual components. Valve springs, con rods, bearings, and the speed at which the pistons are moving in the bore. Which one fails first is like waiting for the Lotto balls to come up.
The red line is the number the manufacturer has figured the engine can run at, without damage. Go past that at your own risk. Most modern cars have an electronic rev limiter anyway, try and push past the red line, and it just starts cuts the fuel and spark.
Now you can rebuild an engine with all sorts of fancy internals that will allow it to rev higher. but it will probably wear out faster. Like Formula One engines rev like crazy, but they don't make 200,000ks. Try and take a regular engine to those revs, and you will get all sorts of exciting noises and smoke.
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