Ethanols future with Direct Inction, please dont hate
06-26-2007, 01:52 PM
#33
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Join Date: Feb 2005
Posts: 0
Re: Ethanols future with Direct Inction, please dont hate
Originally Posted by eDm-cRxXx
The overlap is a few degrees BTDC until a few degrees ATDC. So the piston is not moving much, down or up. But the second both valves are open (piston on its way up!) the huge vacum in the intake manifold on a Otto engine is making exhaust gas go back in to the combustion chamber. On a diesel engine you never have any vacum that is worth talking of.
The exhaust gasses take the place of air, so you don't get as much air in to the cylinder as normaly. The exhaust gasses does not burn, so you get a weaker combustion since there is less air. That means you don't get as high pressure, and that means you don't get as high temprature. Lower combustion temprature means lower NOX. This is excatly what is done with an EGR system, only you manualy put exhaust in to the inntake.
And btw, to temprature in the sylinder when the exhaust stroke is close to done, is like 5 times cooler then the temprature during the combustion.
The exhaust gasses take the place of air, so you don't get as much air in to the cylinder as normaly. The exhaust gasses does not burn, so you get a weaker combustion since there is less air. That means you don't get as high pressure, and that means you don't get as high temprature. Lower combustion temprature means lower NOX. This is excatly what is done with an EGR system, only you manualy put exhaust in to the inntake.
And btw, to temprature in the sylinder when the exhaust stroke is close to done, is like 5 times cooler then the temprature during the combustion.
Also about the valves, when the piston is going up it's still working as an air pump which should keep the exhaust gas from flowing back into the cylinder. ATDC it's going to have a possibility, and may, but i doubt the intake is that substantial. You're never going to get complete combustion anyway, air being 78%~ nitrogen is going to put a damper on that before you even start throwing exhaust gas back into the combustion chamber.
06-26-2007, 03:12 PM
#34
0.5 BAR
Join Date: Jul 2003
Posts: 82
Re: Ethanols future with Direct Inction, please dont hate
Originally Posted by rawr
So basically, exactly what I said. adding exhaust gas doesn't cool the combustion, but limits the combustion-reaction due to the lack of oxygen. Causing the combustion to not have the possibility of releasing as much energy. It's not cooling, it's preventing energy from being released. Also, I'm fully aware of how emissions equipment works.
Also about the valves, when the piston is going up it's still working as an air pump which should keep the exhaust gas from flowing back into the cylinder. ATDC it's going to have a possibility, and may, but i doubt the intake is that substantial. You're never going to get complete combustion anyway, air being 78%~ nitrogen is going to put a damper on that before you even start throwing exhaust gas back into the combustion chamber.
Also about the valves, when the piston is going up it's still working as an air pump which should keep the exhaust gas from flowing back into the cylinder. ATDC it's going to have a possibility, and may, but i doubt the intake is that substantial. You're never going to get complete combustion anyway, air being 78%~ nitrogen is going to put a damper on that before you even start throwing exhaust gas back into the combustion chamber.
Yes, the air is containing about 78% nitrogen, but you can't do anything with that. So we will have to consentrate on alle the small things we can do something about.
06-27-2007, 02:26 AM
#35
1.5 BAR
Join Date: Aug 2003
Posts: 1,164
Re: Ethanols future with Direct Inction, please dont hate
Ethanol defiantly has some pros and cons. I was talking at length today with an engineer from Federal Mogul about some parts for a new engine that is in development and the conversation went towards the topic of ethanol.
The biggest pro is pure performance. There is no doubt that E85 is a very good choice for someone who is planning to make big numbers with high boost or compression.
There are many cons with different levels of complexity. For one, ethanol clogs injectors like a ----------er. It helps if you run like 5 tanks of E85 and then 1 tank of regular gasoline to help clean the fuel system. Another big problem is corrosion and induced wear. In some instances the corrosion of the valve seats will be so severe that the valve will not seal properly and during combustion the valve/seat interface will get toasted leading to failure. Lets say a standard valvetrain is designed to loose .5mm of lash through out its life (150,000 miles or 600-1000 hours of dyno testing.) Running on E85 it will loose approx 2mm of lash in its life. There are seats on the market today that are a better match with E85 such as copper infiltrated sintered powder metal (3010) but corrosion is still a problem. The copper infiltration helps with the general porosity of powder metal as well as heat dissipation but it doesn't completely eliminate the problem. E85 is much more harsh on the intake valves than the exhaust valves which would be a benefit for direct injection. E85 is also very corrosive to the cylinder walls and piston rings. Things get even more complicated in high boost applications where fuel dilution can cause other problems although fortunately most seals today are ethanol compliant. Then with emissions. There is more fuel being burned and although emissions are reduced in some categories they are increased in others.
Then on the discussion of just making ethanol in general gets heated pretty quickly. There is the debate about the amount of energy needed to produce ethanol vs. the amount you get out, the amount of nutrients that it takes out of the soil, and greenhouse gas emissions. Then people are forecasting that with the current level of the governments financial assistance many farmers will switch to ethanol production. This could lead to food shortages and soon we will be importing not only gasoline but also food from other countries. Ethanol production via corn is not high yield in comparison to some of the other possible ethanol sources.
I recently observed a teardown of the Audi 2.0L TFSI engine which was direct injected. The system as a whole is very complicated. The injection system itself is very advanced and expensive but there were also these sliding plates in the intake ports which helped induce tumble into the cylinder. My boss was previously a Sr. Designer at Porsche and had a lot of experience with the development of these systems. I was amazed to learn of the complexity of the engine. It is an amazing engine, although the cost is high.
Cliffnotes:
Better Performance
Worse fuel economy
Shorter Engine Life
Equal emissions
Complex issues surrounding its production.
I could go on and on about the topic but those of you who care probably already know and those that don't know probably dont care. I am by no means an expert on the topic but i have been learning quickly and been thrown into it with my current job. I have been trying to learn as much as i can from the people around me which is where most of this info comes. Dont be surprised if i have a fact or two wrong. :1
The biggest pro is pure performance. There is no doubt that E85 is a very good choice for someone who is planning to make big numbers with high boost or compression.
There are many cons with different levels of complexity. For one, ethanol clogs injectors like a ----------er. It helps if you run like 5 tanks of E85 and then 1 tank of regular gasoline to help clean the fuel system. Another big problem is corrosion and induced wear. In some instances the corrosion of the valve seats will be so severe that the valve will not seal properly and during combustion the valve/seat interface will get toasted leading to failure. Lets say a standard valvetrain is designed to loose .5mm of lash through out its life (150,000 miles or 600-1000 hours of dyno testing.) Running on E85 it will loose approx 2mm of lash in its life. There are seats on the market today that are a better match with E85 such as copper infiltrated sintered powder metal (3010) but corrosion is still a problem. The copper infiltration helps with the general porosity of powder metal as well as heat dissipation but it doesn't completely eliminate the problem. E85 is much more harsh on the intake valves than the exhaust valves which would be a benefit for direct injection. E85 is also very corrosive to the cylinder walls and piston rings. Things get even more complicated in high boost applications where fuel dilution can cause other problems although fortunately most seals today are ethanol compliant. Then with emissions. There is more fuel being burned and although emissions are reduced in some categories they are increased in others.
Then on the discussion of just making ethanol in general gets heated pretty quickly. There is the debate about the amount of energy needed to produce ethanol vs. the amount you get out, the amount of nutrients that it takes out of the soil, and greenhouse gas emissions. Then people are forecasting that with the current level of the governments financial assistance many farmers will switch to ethanol production. This could lead to food shortages and soon we will be importing not only gasoline but also food from other countries. Ethanol production via corn is not high yield in comparison to some of the other possible ethanol sources.
I recently observed a teardown of the Audi 2.0L TFSI engine which was direct injected. The system as a whole is very complicated. The injection system itself is very advanced and expensive but there were also these sliding plates in the intake ports which helped induce tumble into the cylinder. My boss was previously a Sr. Designer at Porsche and had a lot of experience with the development of these systems. I was amazed to learn of the complexity of the engine. It is an amazing engine, although the cost is high.
Cliffnotes:
Better Performance
Worse fuel economy
Shorter Engine Life
Equal emissions
Complex issues surrounding its production.
I could go on and on about the topic but those of you who care probably already know and those that don't know probably dont care. I am by no means an expert on the topic but i have been learning quickly and been thrown into it with my current job. I have been trying to learn as much as i can from the people around me which is where most of this info comes. Dont be surprised if i have a fact or two wrong. :1
06-27-2007, 03:15 AM
#37
0.5 BAR
Join Date: May 2006
Posts: 86
Re: Ethanols future with Direct Inction, please dont hate
Originally Posted by eDm-cRxXx
Becouse they pump air? what do you mean by that? Does not all engines pump air?
Diesel engines have high C/R becouse if they did not they would not work. You would not get high enough temprature for the diesel to vapor, or to ignite if it was not for the high CR, or high boost pressure.
The formula for the efficency of an engine during a ideal burning prosses (adiabatic) is E = 1(-1/CR^(kappa - 1)).
E=epsylon=efficency
Kappa in a adiabatic burning prosses is 1,4, in reality it fluctuates (polytrop), if we took that in to the summary it would also be in the diesel engines favour.
So: 1(-1/22^0,4) = 0,71 for a diesel engine with 22:1 C/R
1(-1/10^0,4) = 0,6 for a gasoline engine with 10:1 C/R
High CR gives less heat losses and a better type of energy (energy is not always just energy).
The only advantage with gasoline is that it burns faster, wich is a problem for diesel, that is why they only manage about 5000rpm. This is for the same reson as above, only in the other engines favor. Slow burning rate means more warm energy is lost out in the exhaust.
Another loss of having a throttle valve is that we have underpressure (vacum) in the intake, and when the inntake and exhaust valves overlapp, some exhaust gasses are pulled back in to the combution chamber. This gives lower combution temrature, and that gives lower efficency, and also lower NOX gasses (this is what the EGR system does normally, so offcorse in one way it is a bit positive).
But the biggest addvatage for the diesel is that when you don't need much engine power the lambda is really high, it can run up to lambda = 5 (city crusing), and the gassoline engine has to run labda = 1 all the time (can be up to 2,5 on FSI engines). So a 1,6 diesel engines uses a lott less fuel on crusing than a 1,6 gasoline engine.
I agree that E85 engines have a lot of potensial, but i still don't think a Otto engine will ever have better fuel efficency than a diesel engine. But i will continue to buy Gasoline engines, just couse they are so much more fun to drive, and if the maufacturers continue to develop the E85 engines, i really look forward to driving them, couse they have potensial of good MPG, and HIGH hp ratings. The VW 1,4 turbo and compressor engine have allready won lots of awards, but with higher CR and a bigger turbo it would be an awsome engine with really high HP and good MGP.
Diesel engines have high C/R becouse if they did not they would not work. You would not get high enough temprature for the diesel to vapor, or to ignite if it was not for the high CR, or high boost pressure.
The formula for the efficency of an engine during a ideal burning prosses (adiabatic) is E = 1(-1/CR^(kappa - 1)).
E=epsylon=efficency
Kappa in a adiabatic burning prosses is 1,4, in reality it fluctuates (polytrop), if we took that in to the summary it would also be in the diesel engines favour.
So: 1(-1/22^0,4) = 0,71 for a diesel engine with 22:1 C/R
1(-1/10^0,4) = 0,6 for a gasoline engine with 10:1 C/R
High CR gives less heat losses and a better type of energy (energy is not always just energy).
The only advantage with gasoline is that it burns faster, wich is a problem for diesel, that is why they only manage about 5000rpm. This is for the same reson as above, only in the other engines favor. Slow burning rate means more warm energy is lost out in the exhaust.
Another loss of having a throttle valve is that we have underpressure (vacum) in the intake, and when the inntake and exhaust valves overlapp, some exhaust gasses are pulled back in to the combution chamber. This gives lower combution temrature, and that gives lower efficency, and also lower NOX gasses (this is what the EGR system does normally, so offcorse in one way it is a bit positive).
But the biggest addvatage for the diesel is that when you don't need much engine power the lambda is really high, it can run up to lambda = 5 (city crusing), and the gassoline engine has to run labda = 1 all the time (can be up to 2,5 on FSI engines). So a 1,6 diesel engines uses a lott less fuel on crusing than a 1,6 gasoline engine.
I agree that E85 engines have a lot of potensial, but i still don't think a Otto engine will ever have better fuel efficency than a diesel engine. But i will continue to buy Gasoline engines, just couse they are so much more fun to drive, and if the maufacturers continue to develop the E85 engines, i really look forward to driving them, couse they have potensial of good MPG, and HIGH hp ratings. The VW 1,4 turbo and compressor engine have allready won lots of awards, but with higher CR and a bigger turbo it would be an awsome engine with really high HP and good MGP.
06-27-2007, 03:32 AM
#38
0.5 BAR
Join Date: Jul 2003
Posts: 82
Re: Ethanols future with Direct Inction, please dont hate
Most of the diesel engines that don't have high compression have high boost pressure to compensate. And you say, as high as today? 15 years ago the CR on VW diesels was like 25:1, now it's like 19:1. But they have high boost pressure to compensate for it.
But of course no all are the same, but i general diesels have way higher CR than gasoline engines.
If a gasoline engine need 14.7 kilo air to burn 1 kilo gas, and a diesel needs 60 kilo air to burn 1 kilo diesel, of course i matters. I'm not saying a Diesel has three times better efficency, but it is a bit better, that's a fact.
But of course no all are the same, but i general diesels have way higher CR than gasoline engines.
If a gasoline engine need 14.7 kilo air to burn 1 kilo gas, and a diesel needs 60 kilo air to burn 1 kilo diesel, of course i matters. I'm not saying a Diesel has three times better efficency, but it is a bit better, that's a fact.
07-02-2007, 06:56 PM
#39
0.0 BAR
Join Date: Sep 2005
Posts: 15
Re: Ethanols future with Direct Inction, please dont hate
Here's a link for you it cover both Fuel Injection and Carburertor as well.
http://journeytoforever.org/biofuel_...earth/me2.html
http://journeytoforever.org/biofuel_...earth/me2.html
12-06-2007, 01:40 AM
#40
1.0 BAR
Thread Starter
Join Date: Oct 2005
Posts: 437
Re: Ethanols future with Direct Inction, please dont hate
---- it's been a year since I started this post and the world has changed. Gas is $3+/dollar and i have 2 e85 stations within 10 mins from my house, any more thoughts about ethanol?
