The biggest Advance in the Combustion Engine
Discussion
Electronic engine control. Accurate control of fuel, ignition, throttle plate and cam timing allow modern engines to make 100bhp/litre whilst still being everyday drivable and produce less emmisions than even the most humble cars did 20 years ago. Remember what your 170bhp crossflow was like with its webers!
My 2p
Steve
My 2p
Steve
leorest said:
Depends on your definition for "standard combustion engine". It's obviously quite open if you include rotary. So for the shear simplicity and massive power capability for it's size. I take your Wankel and raise you a gas turbine.
Personally I'd raise the Liquid Rocket Engine, allowed space access aswell as flight. Even though my personal favorite is the Hybrid.
los angeles said:
If you accept my premise the only genuinely new engine in the 20th century was the rotary engine - now perfected by Mazda - and today's hybrid concoctions do not come close to its radical innovation, what would you conclude has been the biggest advance in the standard combustion engine, and what in your view remains to be improved?
I respect Mazda for developing the Rotary, Why would you call it innovative Gareth?
Most of you will scoff but I would say it's pollution control devices. From PCV, EGR, O2 sensors, PCM's and other modules, variable valve timing, Etc, Etc. They are responsible for allowing us to do more with less. Most every thing that has to do with making modern cars fast, torque monsters, and a pleasure to drive comes down to the pollution controls.
los angeles said:
what would you conclude has been the biggest advance in the standard combustion engine
The development of lightweight, powerful diesels.
los angeles said:
and what in your view remains to be improved?
The performance of diesel injection systems, which is what limits diesels to 4500rpm. A modern version of Uncle Rudi's original air-blast injection system would allow significantly higher maximum revs.
Cranfield have developed a military diesel motorcycle which does 6000rpm, but they're cagey about the injection equipment and only told me that it's not commercially available. Bugger.
Pigeon said:
what would you conclude has been the biggest advance in the standard combustion engine
The development of lightweight, powerful diesels.los angeles said:
and what in your view remains to be improved?
The performance of diesel injection systems, which is what limits diesels to 4500rpm. A modern version of Uncle Rudi's original air-blast injection system would allow significantly higher maximum revs.
Cranfield have developed a military diesel motorcycle which does 6000rpm, but they're cagey about the injection equipment and only told me that it's not commercially available. Bugger.
Modern diesels can rev to 7000rpm, (see previous post on megane 1.5dci), those ones are limited by software (I worked on the engine management, its the rev limiter), I still have no justification why not, although above certain rpm 4500-5500(depending on the engine) I believe the torque drops off sharply and so there is little benefit.
Making a diesel rev is not an issue, making it produce torque at these rpm levels is.
F.M said:
I`m a secret fan of trying to get internal combustion engines converted to burn the hydrogen and oxygen in water...now that would be a step in the right direction..
Burning hydrogen is easy! Just give me a cheap energy efficient source of generating hydrogen and a safe inexpensive way of storing it. The usual laws of physics apply of course!
Pigeon said:
Cranfield have developed a military diesel motorcycle which does 6000rpm, but they're cagey about the injection equipment and only told me that it's not commercially available. Bugger.
Pigeon
You have to remember that this is a military vehicle and doesn't have to meet the emissions regs that civilian vehicles do. With that freedom in mind they were able to design it using Indirect Injection into pre-combustion chamber (something like a Ricardo Comet). All the swirl turbulent mixing is done in the pre-combustion chamber and means that the inlet port is free to do the job of just flowing as much as air as possible. Also because of the intense mixing in the pre-chamber you don't need the the high injection pressures that Direct Injection diesels do for the business of fuel droplet atomisation and combustion speed. Therefore the fuel injection equipment on an IDI doesn't have to be as cutting edge.
Cheers
Phil
>> Edited by wheeljack888 on Thursday 23 March 10:57
www.keelynet.com/energy/waterfuel.htm
I wonder if there ARE any working prototypes built...?
...and do they really work...?
I wonder if there ARE any working prototypes built...?
...and do they really work...?
F.M said:
www.keelynet.com/energy/waterfuel.htm
I wonder if there ARE any working prototypes built...?
...and do they really work...?
The real problem with this concept is that it requires a large battery that needs to be recharged at home and while it takes the emissions away from the vehicle it pushes them somewhere else (i.e. power station).
The best electrolisis machines (currently available) are about 35% efficient (Enegry input - Net combustable Hydrogen energy output), added to the fact that ICE's are at best 30% efficient.
30% of 35% is 10.5%.
Therefore there is a 3-3.5 multiplication increase in the amount of energy required to travel the same distance compared to the normal petrol/diesel equivalent, however this will probably be more as the new vehicle will be heavier due to all the extra equipment required.
Given that a larger battery supply is required to generate the Hydrogen, range of the vehicle will be severly limited due to the battery operating requirements and capabilities. Usually due to the fact that although water will be easily available you may be sat around for several hours while the battery is recharged.
At which point it is more realistic to either make the vehicle electric drive with batteries which would use at least 50% less energy (i.e. batteries last much longer), or just have a hydrogen storage tank.
Brilliant!
annodomini2 said:
Modern diesels can rev to 7000rpm, (see previous post on megane 1.5dci), those ones are limited by software (I worked on the engine management, its the rev limiter), I still have no justification why not, although above certain rpm 4500-5500(depending on the engine) I believe the torque drops off sharply and so there is little benefit.
Making a diesel rev is not an issue, making it produce torque at these rpm levels is.
I thought it was the slower burn rate of diesel that brought about the lower rev limit - the simple fact that the fuel can't burn sufficiently in the shorter time that higher revs gives.
In answer to the original question though, I too will say the electronics thing. Electronically controlled fuel injection has transformed internal combustion engines, IMO. I'm reminded every time I start my MGB up from cold, but I also can recall reading the road tests of the early (succesfully) injected engines like the early Golf gtis and Pug 205 gtis, and then as electronics came in more strongly the driveability of powerful cars has been transformed.
I'm impressed with my little MX5. I've bolted a supercharger on and gained a huge power hike without too much hassle. The Mazda ecus aren't great so I do have some idling issues, but like somone has already said - its great to be able to get 190bhp without lumpy cams, or spitting carbs, blueprinted engines, polished and ported heads etc. Amazing.
(The standard suspension on the MX5 has also staggered me with how it deals with the power. It seems to create grip to deal with the extra horses, but this is another subject, of course).
wheeljack888 said:
Cranfield have developed a military diesel motorcycle which does 6000rpm, but they're cagey about the injection equipment and only told me that it's not commercially available. Bugger.
Yes, I had wondered if it had been designed around the premise that laying smokescreens is acceptable
and come to think of it I've half an idea that the civilian version they made from it has a more conventional rev limit. IDI has other advantages for high revs too: the narrow exit from the pre-combustion chamber and the slower burn rate give you a lower peak cylinder pressure, and you don't need a thick heavy piston crown to house the combustion chamber in, so you save a significant amount of mass in the reciprocating parts.
My diesel project which is based around the direct-injection Lister-Petter AD1 involves replacing the head and piston with the air-cell (semi-indirect-injection) version off the AC1, both for the reasons stated above and because the pintle-style injector on the AC1 is pretty much self-cleaning and a lot lower on maintenance than the four-nozzle pencil injector on the AD1, which has a bad tendency to carbon up.
heebeegeetee said:
I thought it was the slower burn rate of diesel that brought about the lower rev limit - the simple fact that the fuel can't burn sufficiently in the shorter time that higher revs gives.
It's not so much the burn rate as what happens immediately before the combustion begins. You have to get the fuel into the cylinder, break it into tiny droplets, mix it thoroughly with the air (which is compressed enough to be unhelpfully viscous) and get it to vaporise, all within about 10 or at the most 20 degrees of crankshaft rotation. This is not easy and it is the major reason for injection systems going to ever higher pressures. You get better results if you blast the fuel into the cylinder with a blast of high pressure air, but this is more complex, so people stopped doing it as soon as it became practical to machine parts to the tolerances required for the liquid-only method.
On a petrol engine you have pretty well a whole revolution to achieve mixing and vaporisation, a bit more if you're using a carb, so it's much less of a problem and can usually be ignored.
As far as the actual burn rate goes, a diesel achieves the conditions required for ignition at pretty much the same time throughout the whole volume of the combustion chamber, so once it starts to burn the whole lot goes at once. The burn rate is very rapid and you get a huge pressure spike, hence the hefty construction of diesels. In petrol engine terms, it's running in detonation the whole time.
A petrol engine only achieves the conditions required for ignition at one point - the spark plug. Ignition then spreads from the spark plug throughout the combustion chamber at a not massively fast rate - I think it's about 20m/s. This is the process that takes an awkward amount of time in a petrol engine, and the ignition timing is advanced at high revs to give it time to take place.
Unfortunately you can't really do the same trick by advancing the injection timing of a diesel. The mixing and vaporisation processes depend heavily on the in-cylinder pressure, air flow rates and temperature, which are relatively low during most of the compression stroke and rise rapidly in the final approach to TDC, so if you advance the injection timing you end up injecting into a cylinder which doesn't have the conditions to do anything useful with it, and much of the fuel just drops out onto the walls and doesn't burn.
annodomini2 said:
Modern diesels can rev to 7000rpm, (see previous post on megane 1.5dci), those ones are limited by software (I worked on the engine management, its the rev limiter), I still have no justification why not, although above certain rpm 4500-5500(depending on the engine) I believe the torque drops off sharply and so there is little benefit.
Making a diesel rev is not an issue, making it produce torque at these rpm levels is.
I admit I've never driven a Megane 1.5dci but I'd be surprised if it was actually capable of revving to 7000rpm. The drop in output after 4500rpm is so steep that I'd imagine that the engine would no longer be able to make enough power to overcome its internal losses long before you got to 7000rpm, unless perhaps it was massively overfuelled and left a smoke trail like a burning oil well. So a software rev limit at 7000rpm seems a bit of an academic exercise. I'd stick it at 4500 to avoid the massive rise in accelerative forces to no benefit that you'd get from letting it rev higher.
A quick google failed to reveal any Megane 1.5dci power/torque curves but I did find these (ah, the joys of Opera, you can edit the page source to stop it opening pop-ups for the curves) which all drop off sharply at 4500 and stop at 5000 for obvious reasons.
I'll stick my neck out and say that electronic engine controls have helped make engines make power and do it cleanly in an urban drive cycle.
But there are many unseen technologies that are totally unglamorous that help deliver a great engine - materials technologies have kept components as strong and light as possible, CFD has helped develop combustion chambers and machining centres hold tolerances on components of mass production engines to extremely high standards.
Go to the science museum and you find that most of "today's technology" was running by the late 30s - a Merlin engine is a 4 Valve / cyl SOHC / bank design and has components made of the alloys used in F1 up until a few years back. Look back a bit further and you see that the Merlin is an evolution of design ideas from the teens.
The wankel is an interesting engine but if it was a great solution everybody would be on the band wagon adopting it. The fact that no mass manufacturers have says a great deal.
But there are many unseen technologies that are totally unglamorous that help deliver a great engine - materials technologies have kept components as strong and light as possible, CFD has helped develop combustion chambers and machining centres hold tolerances on components of mass production engines to extremely high standards.
Go to the science museum and you find that most of "today's technology" was running by the late 30s - a Merlin engine is a 4 Valve / cyl SOHC / bank design and has components made of the alloys used in F1 up until a few years back. Look back a bit further and you see that the Merlin is an evolution of design ideas from the teens.
The wankel is an interesting engine but if it was a great solution everybody would be on the band wagon adopting it. The fact that no mass manufacturers have says a great deal.
Pigeon said:
Modern diesels can rev to 7000rpm, (see previous post on megane 1.5dci), those ones are limited by software (I worked on the engine management, its the rev limiter), I still have no justification why not, although above certain rpm 4500-5500(depending on the engine) I believe the torque drops off sharply and so there is little benefit.
Making a diesel rev is not an issue, making it produce torque at these rpm levels is.
I admit I've never driven a Megane 1.5dci but I'd be surprised if it was actually capable of revving to 7000rpm. The drop in output after 4500rpm is so steep that I'd imagine that the engine would no longer be able to make enough power to overcome its internal losses long before you got to 7000rpm, unless perhaps it was massively overfuelled and left a smoke trail like a burning oil well. So a software rev limit at 7000rpm seems a bit of an academic exercise. I'd stick it at 4500 to avoid the massive rise in accelerative forces to no benefit that you'd get from letting it rev higher.
A quick google failed to reveal any Megane 1.5dci power/torque curves but I did find these (ah, the joys of Opera, you can edit the page source to stop it opening pop-ups for the curves) which all drop off sharply at 4500 and stop at 5000 for obvious reasons.
The production engines are limited to approximately 5000rpm, although this is tunable so depends on the version of the tune in the ecu.
On the dyno they have seen 7000rpm (no load), the only information I received with regards to this was there was virtually no torque, due to issues they were having reliably running the version of the pump at that time above 1600bar.
Chipping is limited to modifiying the ECU I/O and doesn't modify the ecu software, therefore you will see it limited to 5000rpm if that is what is defined in the ECU software. Unless they took it further and experienced the problems like you suggested.
The point I was trying to make and as you have already suggested, it is not impossible to make a diesel rev, just there is limited if no practical benefit at this time, mostly due to limits of technology and cost.
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