Really hot engine parts is associated more with pre-ignition. The pre-ignition LEADS TO detonation, but hot valves don't directly cause detonation.... not from what Trevor Thom has taught me anyway.

Fo those of you who don't know, pre-ignition is where the charge in the cylinder ignite before the spark plug fires. Obviously this is exactally the same effect as advancing the ignition, so it causes detonation.

I have to agree with Spork. Leaner certainly does not mean better.

Actually, a leaner maxture 'chokes' the cumbustion process. Not the other way round... not untill you get really rich and start blowing copious amounts of black smoke out the exhaust.

And spark advance directly affects AFR. A more retarded spark, a richer exhaust. ARF directly affects spark advance aswell.

The thing about engines is, everything in an engine relys on at least one other thing to work properly. Basically, you cannot change one thing in an engine without affecting something else. If you could, tuning would be easy!

at what fuel pressure when idleing would give 14.4 - 14.7 afr?

Uncle,

Thats why I said partly. I needed to dumb it down for the non pilots and the lower IQ'd people among us.

im sorry, i couldnt tell you. I found these A/F's to work well from playing with a aftermarket ecu and fuel maps.

Any fuel pressure @ idle will give 14.7:1 AFR. If the fuel pressure goes up, the pulse width and duty cycle (the amount of time the injector is open) decreases and vice versa.

EFI engines typically run about 15-20psi @ idle and 36-45 psi @ WOT.

Don't be too fooled by people telling you about 'rising rate' fuel pressure regulators. ALL fuel pressure regulators are rising rate. The more manifold pressure, the more fuel pressure.

The after market 'rising rate' fuel pressure regulators rise at a faster rate than standard. i.e a standard regulator might run 20psi @ idle and 40psi @ WOT. A 'rising rate' regulator might run 20psi @ idel, but 60psi @ WOT.

lol, poor guy asks what rich/lean means, and he gets a whole science on fuel and air...lol... good read but.


Cheers

So, your saying that an engine won't run as hot if you run it rich, than if you run it at stoichiometric mixture... and if its too lean it will run hotter with more likelyhood of pre-detonation.

When I did science at school (basic), fuel needs oxygen to burn, and every fuel only has a certain ammount of energy / heat which can be released with a certain volume of air.

Hence why jet engines compress large quantities of air use a mixture of kerosene and alcohol as those fuels have the highest energy rating and have the power to produce an excess of 35,000 kW of thrust... yeah, and I thought the 290kW GT was impressive!!!.

The way I see it, its pointless adding more fuel to volume of air as there is not enough oxygen, so your wasting fuel... There is an increase in power, as this is one process on how jet engines spool up their turbine/compressors.

And if you run it lean, then your not getting the full energy release potential from the fuel. So I dont know how a lean engine can produce more energy?

Also, can see by SVO XR6 figures, a high reving engine decellerating on no fuel injection will run a lean mixture... obviously... how safe is it though? Compression braking would increase heat into the engine...



Im not sure how the fuel regulator works, does that mean when there is a high vacume in the manifold (idle)... that vacume opens the valve in the regulator to let bypass pressure through? And when there is no vacume (WOT), the valve is closed for highest fuel pressure???

An over lean engine does not produce more power, infact it produces less.

Jet engines are way different than piston engines. They don't have a carby or EFI. Their fuel is dumped directly into the combustion chamber. They always run a little lean so there is excess oxygen not burned. This way when you add fuel the extra air burns, producing more thrust which spools up the turbine/compressor providing more air. This is how afterburners can work. All they do is dump more fuel after the turbine. The excess oxygen is burnt increasing thrust, but not spooling up the turbine.

In piston planes we add a little more fuel than required. Not to get more power, but to preserve the engine. A stalled engine in a plane is a little more nasty than a car with a d**k engine. I'd prefer to use a little more fuel than to to risk burning out valves.

Also running an engine rich doesn't really effect the heat of the engine as a whole. It does cool down the exhaust valves.

As for the high reving engine with no throttle, the fuel is actually switched off above 1500rpm. No fuel = no fire = no heat.

PS thrust is measured in pounds, kilograms, newtons. It cannot be measured in kW. The turbine does produce a huge number of kilowatts to turn the compressor which supplies the air. This burns to prodce thrust and spin the turbine.

The engine as a whole doesn't run hotter or colder in response to AFR.... but things like valves which temps aren't measured, do get hotter or cooler in response to AFR



Not really as simple as that, and there are differences b/n turbo fan engines and turbo jet engines. Then you got your turbo props which are a hybrid b/n a jet engine and a piston engine. Also, put a jet engine in a car and just watch the 290kW GT leave you for dead. Ya see, a jet engine takes about 8 seconds to spool up from idle to full thrust.



Don't forget that fuel also lubricates the inside of the cylinder. If you reduce the friction, you increase the available power @ the flywheel. The engine doesn't produce any MORE power, it's just that lees of the power it's producing goes into overcoming the frictional losses.



Yes you are actually. All the fuel in the cylinder is being burnt. It's just that you're not getting all the potential from the oxygen in the cylinder.



Running lean only buggers stuff up when the engine is under load.



In a nut shell that's exactally how a fuel pressure regulator works. You have a rubber diaphram in the housing. One side is connected to an engine vacuum line, the other side is connected to a valve and fuel passes through that to either the fuel rail, or back to the tank.

If there is high manifold vacuum, it sucks up the diaphram and lets more fuel go back to the fuel tank. If there is low manifold vacuum, the opposite happens. Also there is obviously a spring in there to make everything work too.