direct injection
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direct injection What has been keeping direct injecting gas engines from being widespread. What obstacles have to be overcome?
My understanding says that one would be able to run much higher compression ratios in a gas engine if the fuel was not in the cylinder with it. After all, at the same compression ratio, a gas engine is actually more efficient than a diesel.
My understanding says that one would be able to run much higher compression ratios in a gas engine if the fuel was not in the cylinder with it. After all, at the same compression ratio, a gas engine is actually more efficient than a diesel.
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I don't believe there is any substantial advantage re max compression ratio. Once the fuel is mixed and ignited, it burns about the same regardless of where it was introduced. DI will support very lean, stratified charge combustion, which gives a big fuel economy advantage, but the resulting high NOx emissions flunk Canada/US standards, so DIs here manage only modest gains.
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Gas direct injection runs into the same problem of getting a good fuel mixture throughout the cylinder that diesel engines do. Combustion likes to take place around the injector. This generates heat in a localized area which tends to generate a lot of NOx . You also have some of the same problems that turn off people to diesels , engine noise and vibration.
I think DI is an added expense.
Honda likes to use it in the Asian market. Maybe because of emmision laws.
I just saw an article on a Lex engine that uses DI and port injectors. WHY go through all the expense? I have no idea. They claimed to pick up 7% power. They claimed the that the increased speed of the fuel flow (DI injector) helped solve a 'doldrum' area of the RPM range at which the car would cruise at.
Honda likes to use it in the Asian market. Maybe because of emmision laws.
I just saw an article on a Lex engine that uses DI and port injectors. WHY go through all the expense? I have no idea. They claimed to pick up 7% power. They claimed the that the increased speed of the fuel flow (DI injector) helped solve a 'doldrum' area of the RPM range at which the car would cruise at.
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Originally Posted by ConnClark
Gas direct injection runs into the same problem of getting a good fuel mixture throughout the cylinder that diesel engines do. Combustion likes to take place around the injector. This generates heat in a localized area which tends to generate a lot of NOx . You also have some of the same problems that turn off people to diesels , engine noise and vibration.
This I think would improve NVH. Maybe the high pressure delivery system is noisy, but that will be worked out in time.
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If the whole point is to prevent knock from occuring at higher compression ratios the fuel most be injected toward the top of the stroke. The air temp also peaks at the top of the stroke. I think they are using a spark to ignite the air fuel mixture just as injection starts to take place to establish combustion before the bulk of the fuel enters the cylinder to avoid detonation. What you end up with is almost a diesel cycle.
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Precisely why I think the fuel would best be injected right when the piston stops at TDC or very shortly before, time permitting. I don't see how the spark could be ignited during injection as that would ensure that the air/fuel mixture wouldn't be an air/fuel mixture. I could see an alternative fuel very high compression engine using ethanol to lower compression temps with a percentage of fuel injected well into the intake runner and the bulk direct injected. A 14-15 to 1 engine would be damn responsive and could possibly recover the mileage lost from the lower energy fuel.
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Then you're back to diesel fuel which runs at a slightly higher stoich point, thus containing more energy than gas. That and the lack of a throttle, why mess with gasoline at all then? 2 stroke diesels for everybody! Just doesn't sound sexy at all to me.
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Yeah but you can run them off of just about anything. Corn oil, Lin seed oil, soy bean oil, peanut oil, rendered animal fat, and rendered fat from eco-weenies that grip about diesel soot and NOx.
In finland there are guys getting 400+ HP out of 3 liter diesels http://www.teamrwd.com/dieselboost/v...dslboost05.wmv
Edit: Dyno chart http://www.teamrwd.com/dieselboost/merssu1.jpg
In finland there are guys getting 400+ HP out of 3 liter diesels http://www.teamrwd.com/dieselboost/v...dslboost05.wmv
Edit: Dyno chart http://www.teamrwd.com/dieselboost/merssu1.jpg
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Originally Posted by joecar
Will they run on used engine oil, used atf and used gear oil...?
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From: Raleigh, NC
Originally Posted by bigredexpress99
the pontiac soltice gtp and saturn sky redline with their turbo engines use direct injection.
Can someone here explain exatly what direct injection is?
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Audi uses DI on a few current production engines. They did well with their R8 LeMans DI gasoline engines for the last few years. The got about one more lap per fill up than the competition.
For high performance engines DI allows more mass of air to get into the engine because fuel isn't taking up some of the space. Another advantage is that you are not blowing fuel out the exhaust during valve overlap in the (lower) rpm ranges where that occurs.
DI requires high fuel pressures. F1 is being limited to 100 Bar (1470 psi). Some F1 engine builders tried fuel pressures up to 500 Bar, but didn't go to DI even before the 100 Bar limit. Getting a fuel pump to do very high pressure efficiently with gasoline is a challenge. Diesel fuel lubricates the fuel pump, but gas just cleans it out and lets it heat up.
For high performance engines DI allows more mass of air to get into the engine because fuel isn't taking up some of the space. Another advantage is that you are not blowing fuel out the exhaust during valve overlap in the (lower) rpm ranges where that occurs.
DI requires high fuel pressures. F1 is being limited to 100 Bar (1470 psi). Some F1 engine builders tried fuel pressures up to 500 Bar, but didn't go to DI even before the 100 Bar limit. Getting a fuel pump to do very high pressure efficiently with gasoline is a challenge. Diesel fuel lubricates the fuel pump, but gas just cleans it out and lets it heat up.
Correct me if I'm wrong, but I believe another of the benefits of DI is that the atomization, and evaporation of the liquid gasoline helps to cool the combustion chamber during the process, poviding additional detonation resistance over a conventional injection setup.
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yeah you have to run really high injector presure. this really helps with atomization and thus more power and better fuel econamy!
Audi are using DI in their new V10 (nicked form the lambo) and its pretty good!
Chris.
Audi are using DI in their new V10 (nicked form the lambo) and its pretty good!
Chris.
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From: Raleigh, NC
Originally Posted by niphilli
The new BMW turbo inline six is also using it.
Can someone here explain exatly what direct injection is?
Can someone here explain exatly what direct injection is?