73 replies to this topic

[J. Edlund]

I know that.

Im saying that there is or has been research in trying to harness the extra potential found in making the fuel explode in a controlled manner.

Dunno much more than that really, i did a quick Google search and only found some suspect propaganda from the quasi turbine/rotor motor.

No, the whole 'detonation' thing are usually scams.

that's what i wanna know.

I see clearly potensial in ship motors were you just filter the water, inject and wòila! extra power and cooling.

Its quite common in big street race motors here in norway.

Got a granada with 1700hp and a audi with 1200hp. both on water injection.

must be a issue due to the salt?

Water injection is here for cooling and knock supression. That way we can crank up the boost and burn more fuel which in turn increase power. Injecting water alone in an engine will do very little, decrease the efficiency a bit probably, but nothing significant. With a diesel it would be pointless to inject water for knock suppression.

well yea on the first posts i was talking about stuff like the crower six stroke.

The street cars were for showing a practical area were water already has proved it cooling capasity, and performance gain.

the cooler needed for the granada needed to be somewere about 2x1Meter so it was a bit unpractical.

Perhaps its a better idea for warships and such? the crower way i mean.

They need all the power they can get.

With waterinjection you don't need a cooler unless you're trying to extract water for your injection system from the exhaust.

Modern warships tend to use gasturbines, or combined diesel and gas, with a diesel for low speed operation and a gas turbine for high speed operation. The Norwegian Skjold class patrol boats for instance have two diesels and two gas turbines, and using the turbines the boat the do more than 60 knots (110 km/h).

I don't think that electric water pumps are necessarily more efficient, but the others, yes, because you don't need them on all the time.

The problem with the conventional water pump is that is has a constant gear ratio between the pump and the crankshaft. So, for most of the time, the conventional water pump is oversized for the job, particulary at high engine speed. With an electric water pump, usually the whole cooling system is designed around the electric pump. The cooling circuit is designed for a low flow restriction and this is combined with a mapped electronic thermostat. Usually the maximum output of the pump is small, BMW uses a pump rated at 200W for instance. Advantages of a lower power consumption is also combined with shorter heat up periods.

Edited by J. Edlund, 11 March 2010 - 00:37.

[MatsNorway]

Water injection is here for cooling and knock supression. That way we can crank up the boost and burn more fuel which in turn increase power. Injecting water alone in an engine will do very little, decrease the efficiency a bit probably, but nothing significant. With a diesel it would be pointless to inject water for knock suppression.

They inject plenty of water in tracktor pulling (diesels)


why not at a ship engine? Does the saltwater something naughty?

Edited by MatsNorway, 11 March 2010 - 10:21.

[McGuire]

To a degree you will make more power by increasing temeratures, manufacturers have done it for 20 + years. The old 180F is now 195F. A performance engine should make more power at similar or slightly higher temps, but it gets near detonation and unwanted friction over about 205F. 195 is far safer. We lose too much useable heat through cooling systems but it really is a catch 22. Though most are far more efficient these days. And ofcourse oil temp is really more critical than coolant.

On current high-performance cars, a lower temp thermostat will invariably make more power. Especially true with supercharged and turbocharged cars. The reason is simple: reduced intake manifold temperature, increased charge density. A 160 F thermostat is a common component in tuner packages, along with the undersized blower pulley and fresh air intake.

The OEs have raising their thermostat calibrations for a different set of reasons: fuel economy, driveability, emissions. If they didn't have CAFE and other requirements to deal with, the engine calibrators would love to slip a lower temp thermostat in there.

[VAR1016]

On current high-performance cars, a lower temp thermostat will invariably make more power. Especially true with supercharged and turbocharged cars. The reason is simple: reduced intake manifold temperature, increased charge density. A 160 F thermostat is a common component in tuner packages, along with the undersized blower pulley and fresh air intake.

The OEs have raising their thermostat calibrations for a different set of reasons: fuel economy, driveability, emissions. If they didn't have CAFE and other requirements to deal with, the engine calibrators would love to slip a lower temp thermostat in there.

Interesting that.

No science in this post, but me, I'm a Lancia Fulvia enthusiast; Fulvias always had 160°F/70°C thermostats.

[Lee Nicolle]

On current high-performance cars, a lower temp thermostat will invariably make more power. Especially true with supercharged and turbocharged cars. The reason is simple: reduced intake manifold temperature, increased charge density. A 160 F thermostat is a common component in tuner packages, along with the undersized blower pulley and fresh air intake.

The OEs have raising their thermostat calibrations for a different set of reasons: fuel economy, driveability, emissions. If they didn't have CAFE and other requirements to deal with, the engine calibrators would love to slip a lower temp thermostat in there.

To me that does not make sense. At 30F higher the pistons are not rattling in the bores and the ring gaps are a fraction tighter too. An engine is a heat pump so getting rid of efficient heat seems very wrong.
The only thing that makes sense is that the combustion temp with a turbo is higher but then you have more heat related gasket failures. And when the engine is not making power but just being driven everything is rattling around and wearing out.
An overcooled engine always shows ring marks top and bottom of the stroke where the piston rocks, and if the piston is rocking it is losing ring seal.

[VAR1016]

To me that does not make sense. At 30F higher the pistons are not rattling in the bores and the ring gaps are a fraction tighter too. An engine is a heat pump so getting rid of efficient heat seems very wrong.
The only thing that makes sense is that the combustion temp with a turbo is higher but then you have more heat related gasket failures. And when the engine is not making power but just being driven everything is rattling around and wearing out.
An overcooled engine always shows ring marks top and bottom of the stroke where the piston rocks, and if the piston is rocking it is losing ring seal.

I was intending to add that I have on occasion found that the car does seem to go better when temperature is a bit higher; however I do have a cold air intake!

[MatsNorway]

Edlund i believe brilliantly posted that in teori efficiency goes up the bigger the temperature difference is.

Or something like that.

Now, can someone please explain why modern diesel cars need extra heaters installed, if they would work better at high temperatures.

Is it those damn emissions?

Edlund could you post the max burn temperature for diesel?

[Lee Nicolle]

I was intending to add that I have on occasion found that the car does seem to go better when temperature is a bit higher; however I do have a cold air intake!

Cool dense air on the intake makes power and efficiency. Great for turbos.
Interestingly both LPG and diesel fueled engines love cold air, more so than any petrol fueled engine.

[gruntguru]

There are two simple principles to apply in this thread.

1. For maximum V.E. and therefore power, the intake charge needs to be kept as cool as possible right up to the moment the intake valve closes. Any hot surfaces, from air cleaner to piston crown will work against this.

2. For best efficiency (and therefore also best power) the charge should lose as little heat as possible after TDC so the chamber surfaces should be as hot as possible.

These two requirement are obviously in conflict when considering the chamber, cylider abd piston crown. The paper below is an interesting study of an engine that need to maximise both power and fuel economy.

Honda F1 turbo paper.

Courtesy of Vivian.

Edited by gruntguru, 12 March 2010 - 07:44.

[McGuire]

To me that does not make sense. At 30F higher the pistons are not rattling in the bores and the ring gaps are a fraction tighter too. An engine is a heat pump so getting rid of efficient heat seems very wrong.
The only thing that makes sense is that the combustion temp with a turbo is higher but then you have more heat related gasket failures. And when the engine is not making power but just being driven everything is rattling around and wearing out.
An overcooled engine always shows ring marks top and bottom of the stroke where the piston rocks, and if the piston is rocking it is losing ring seal.

This may seem counterintuitive, but with modern low/multi-vis oils and proper assembly, there is no hp benefit in building heat in the oil and cooling systems, while keeping temps as low as possible increases charge density. In NHRA Pro Stock they run 0-5W oil and keep the engine as cold as they can, coming to the line at under 100 F water and oil temps, 120 max. Needless to say, flogging an ice-cold engine this way requires precision fits and assembly -- if the engine is not right they will find out very quickly -- but it absolutely will make more power. This is some pretty fine whittling: In P/S, the difference between the pole and DNQ in a 16-car field can be as little as .02 seconds. This was also the route in NASCAR qualifying engines until NASCAR essentially eliminated qualifying engines.

[SteveCanyon]

2. For best efficiency (and therefore also best power) the charge should lose as little heat as possible after TDC so the chamber surfaces should be as hot as possible.

I've heard differing stories, but one reputable person has told me that when ceramic coating the pistons and combustion chamber you should only do one, not both of them or it can trap too much heat in the chamber and promote detonation.
But I'm not convinced. For the next engine I build I'd like to get both surfaces coated and also the exhaust ports.

Opinions .... ?

Also have a read of the Toyota engineering paper on their 2ZZ engine. If you read between the mines it infers the same thing about head temps that has been said here.
http://www.mmsport.c...ine-Development

[Lee Nicolle]

I've heard differing stories, but one reputable person has told me that when ceramic coating the pistons and combustion chamber you should only do one, not both of them or it can trap too much heat in the chamber and promote detonation.
But I'm not convinced. For the next engine I build I'd like to get both surfaces coated and also the exhaust ports.

Opinions .... ?

Also have a read of the Toyota engineering paper on their 2ZZ engine. If you read between the mines it infers the same thing about head temps that has been said here.
http://www.mmsport.c...ine-Development

Biggest problem with ceramic coating is that it tends to chip and when it does you have a white hot spot causing a huge detonation.
From what I am told it is far better these days but it still happens.All those edges on pistons, chambers,around valves is where it chips/peels.
Doing the exhaust port should be safe though you may make it too efficient

[Lee Nicolle]

This may seem counterintuitive, but with modern low/multi-vis oils and proper assembly, there is no hp benefit in building heat in the oil and cooling systems, while keeping temps as low as possible increases charge density. In NHRA Pro Stock they run 0-5W oil and keep the engine as cold as they can, coming to the line at under 100 F water and oil temps, 120 max. Needless to say, flogging an ice-cold engine this way requires precision fits and assembly -- if the engine is not right they will find out very quickly -- but it absolutely will make more power. This is some pretty fine whittling: In P/S, the difference between the pole and DNQ in a 16-car field can be as little as .02 seconds. This was also the route in NASCAR qualifying engines until NASCAR essentially eliminated qualifying engines.

While I sort of understand the theory by the time they have done a burnout, reversed, played staging games the engine should be pretty warm for the race.
The pistons must be very stable to say the least as the full throttle heat will be making them expand 3-4 thou normally.
What fuel are they using? Petrol, Avgas or methanol?

[J. Edlund]

They inject plenty of water in tracktor pulling (diesels)

why not at a ship engine? Does the saltwater something naughty?

Tractor pullers use water for charge cooling. Some of these engines run quite extreme boost pressures. Say they run two stage charging at 3:1 pressure ratio for a total boost pressure of 9 bar absolute (this is by no means extreme in tractor pulling). Assuming an air inlet temperature of 20 degC and an adiabatic efficiency of 70%, the first turbocharger increase the temperature to 175 degC and the second, if the air is uncooled, to 410 degC. Obviously they don't want a charge air temperature of 410 degC, and the aluminum impeller of the second turbocharger would have trouble dealing with that temperature aswell.

Secondly, these engines run very rich, way beyond the smoke limit as we can see from your picture. Running this rich on a diesel means that the exhaust temperature will be high, partly because of the rich mixture and partly because of the long injection duration. The efficiency will of course be low, but these guys only care about maximum power, and water injection will help cool the engine.

With a ship engine this is all pointless. The engine doesn't run rich, they run lean for maximum efficiency. They can also use seawater and a heat exchanger for charge cooling.

Saltwater are never used directly in larger engines as saltwater damage engines.

Edlund i believe brilliantly posted that in teori efficiency goes up the bigger the temperature difference is.

Or something like that.

Now, can someone please explain why modern diesel cars need extra heaters installed, if they would work better at high temperatures.

Is it those damn emissions?

Edlund could you post the max burn temperature for diesel?

Diesel cars need extra heaters because when it's cold, they have trouble reaching operating temperature. And if the engine doesn't get warm, then neither is the cabin which is heated by engine coolant.

The maximum burn temperature of diesel isn't really interresting. A diesel engine can reach over 2700 K in the outer zone of the fuel spray plume, which is more than is wanted since it leads to NOx formation. That's why modern diesels use EGR, it reduces the maximum temperature reached during combustion. Inside the plume however, the temperature is lower, around 1600 K, and closer to the nozzle just 800 K; this results in soot formation as the temperature isn't high enough to burn the hydrocarbons fully.

I've heard differing stories, but one reputable person has told me that when ceramic coating the pistons and combustion chamber you should only do one, not both of them or it can trap too much heat in the chamber and promote detonation.
But I'm not convinced. For the next engine I build I'd like to get both surfaces coated and also the exhaust ports.

Opinions .... ?

Also have a read of the Toyota engineering paper on their 2ZZ engine. If you read between the mines it infers the same thing about head temps that has been said here.
http://www.mmsport.c...ine-Development

Cosworth tested 'insulated' pistons and they reported it caused a reduced engine output and trouble with knocking. This is hardly surprising. During combustion, the pressure rise in the cylinder compresses the end gases, which in turn increase their temperature. Normally these end gases are cooled by the much cooler piston and cylinder head, but if these parts are insulated this quenching effect will be reduced and the end gas temperature will increase and in turm increase the possebility for knock.

I also seem to recall it resulted in a loss of volumetric efficiency due to the increased surface temperature of the piston.

With a diesel it's a different matter though, but having a ceramic layer up to a few mm thick on the piston crown is hardly ideal for the reliability of the engine. You need to find a ceramic with good thermal shock properties and a heat expansion coefficient similar to that of the piston material. A steel piston would certainly help with the latter.

[gruntguru]

Also have a read of the Toyota engineering paper on their 2ZZ engine. If you read between the mines it infers the same thing about head temps that has been said here.
http://www.mmsport.c...ine-Development

From the document page 2, intake opening - up to 58* BTDC - must get pretty close to the piston?

Interesting, different block materials were rated for bore temp (A; excellent B; very good C; good D; poor) but they don't say whether "excellent" means hotter or colder.

[MatsNorway]

Saltwater are never used directly in larger engines as saltwater damage engines.

thanks. but you know i tried to say/ask things between the lines, several times.

[Greg Locock]

thanks. but you know i tried to say/ask things between the lines, several times.

Trouble is your commendable grasp of ESL is confusing enough that many subtleties in intent are lost. I suggest that for the time being if you are trying to hint at something, say it directly.

[MatsNorway]

Trouble is your commendable grasp of ESL is confusing enough that many subtleties in intent are lost. I suggest that for the time being if you are trying to hint at something, say it directly.

ESL?

[Canuck]

English as a Second Language. Of course your English is better than my Norwegian...

Edited by Canuck, 14 March 2010 - 14:25.

[McGuire]

While I sort of understand the theory by the time they have done a burnout, reversed, played staging games the engine should be pretty warm for the race.
The pistons must be very stable to say the least as the full throttle heat will be making them expand 3-4 thou normally.
What fuel are they using? Petrol, Avgas or methanol?

Generally, VP C16 racing gasoline or its equivalent -- 116 motor octane, 120+ (i.e. off the scale) research octane. They run generous skirt-to-wall clearance and very low ring tension, with a whisker-thin top ring, vertical gas ports, and loads of crankcase vacuum, 20 in Hg or more. Since piston coatings were mentioned, yes they use them.

[Canuck]

Crown, skirt, both?

[J. Edlund]

Crown, skirt, both?

Usually it's skirt and ring area that are coated for low friction and wear resistance. There are a few coatings intended for reducing carbon built up on the crown and reflect heat, while at the same time offer a high heat conductivitivy, but as stated by Mahle Motorsport, they haven't been able to find such a coating where the advantages are worth the trouble.

[Canuck]

I also seem to recall it resulted in a loss of volumetric efficiency due to the increased surface temperature of the piston.

Why is the piston hotter? I thought the whole point of a heat rejection coating was to reflect the heat?

[gruntguru]

Why is the piston hotter? I thought the whole point of a heat rejection coating was to reflect the heat?

It acually just insulates, so the surface is hotter.