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| Engine Technology From the novices to the pros, talk about engine technology. Moderated by David Vizard, professional engine developer and well-known technical writer. |
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06-14-2008, 03:19 AM
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Please elaborate, i.e what are the "right parts" Coils : As far as I can tell a coil with a low turn ratio will reduce heat issues and put more amps in the spark which makes for a hotter spark. Tractor coils have a low turn ratio (60:1) and seem to be whats needed. Some coils are not suited and overheat but this is not an issue that cant be addressed. Spark plugs: The common copper plug will wear quicker with a larger spark but now with so many different types of plugs around (i.e iridium, platinum, brisk halo) that are meant to last 100k km, even if they last 30k km with the stronger spark thats fine with me Spark plug wires: I am just running a common spiral core and no problems. Dont know if they will break down quicker but there a plenty of options. Distributor cap : I can see these wearing out quicker, especially the centre carbon post but it just means more frequent replacement or maybe using a brass post inplace of the carbon one. What are the other considerations? The coil type is clearly the most important 
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06-14-2008, 03:44 AM
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In the past I have been led to believe that the MSD 6A is about a good ignition you can get for a performance engine and that it will light mixtures at high boost/high revs, high load. This is true. CD ignitions are good at lighting these mixtures but as I have found out they are not very good at lighting lean mixtures, especially when you compared it to just putting extra volts thru the coil. Now I think I know why MSD sell a fuel pump booster(increases volts to fuel pump) but they dont market the exact same product as a "spark booster". I think it may have something to with taking away sales from a particular market of theirs? Nevertheless the tuning window with this mod has greatly increased. In the past I tuned one A/f ratio at idle, another between 500 to 1500rpm, another at cruise, another at load. With the high voltage coil setup it just burns any a/f ratio you throw at it and the car does not seem to misfire, it just loses power. In this car the fueling map was not the best with the stock ignition (some parts of the map were too lean, so the car misfired a bit and you easily feel the misfire. Now there are no misfires in those parts of the map and if I lean it out further it just loses power). Its sooo much nicer to drive.
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06-15-2008, 02:45 AM
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One great explanation why we dont have lean burn in our cars
One fuel-saving technology that undoubtedly has been supressed - but for very good reasons - is lean-burn. The ratio of air to fuel is a critical factor in petrol combustion. The theoretically ideal mixture is around 14.5 parts of air to 1 of fuel. This is known as the stoichiometric ratio. Variations from this are characterised by the term lambda, where lambda less than 1 means a rich mixture (excess fuel), and lambda greater than 1 means a lean mixture (excess air). All modern petrol engines run at lambda = 1 under most conditions, but it is well known that significant economy benefits can be gained by running the engine much leaner - ie, with excess air. To obtain the maximum benefit the engine must be optimised in terms of combustion chamber design, ignition timing, etc, so as to allow operation at lambda = 1.7 (24:1 AFR) or even leaner. Various engines to do this were developed in the 1980s (for example Honda's VTEC-e), and could be up to 10% more economical than more conventional engines. However, in 1992 all these engines disappeared from the European market (and from the US market a few years earlier) with the adoption of the "Euro 1" vehicle emissions standards. Many people see this as "proof" that a conspiracy between oil companies, governments and car makers acted to supress the technology and so force people to use more petrol. In fact the truth is much simpler, and can be summed up in one word: NOx. NOx (oxides of nitrogen) is one of the three main toxic pollutants from car exhausts, and by some measures is the most dangerous of the three. Estimates of the number of deaths per year in Europe through NOx pollution range from a few hundred to a few thousand. For obvious public health reasons, European legislators wanted to reduce emissions of NOx and so imposed strict limits to apply from 1992 onwards. (NOx is formed when oxygen and nitrogen in the air combine at the high temperatures that inevitably occur during combustion, and is entirely unrelated to the presence of any nitrogen contaminants in the original petrol.) Unfortunately it was completely impossible to meet these limits through lean-burn technology. Lean-running engines produce less NOx at source than engines running at lambda = 1, but cannot use a three-way catalytic converter to remove the NOx. (What the catalyst does is to remove the oxygen from the NOx and give it to the HC and CO. The result is plain nitrogen, carbon dioxide and water, all of which are essentially harmless. But to work, the lambda value must be just right. If the mixture is too lean then the "spare" oxygen is given to the HC and CO, and the NOx passes through unconverted.) By contrast, the catalytic converter on a "stoichiometric" engine can convert 95-plus percent of the NOx in the exhaust to harmless nitrogen and oxygen, and so achieve much lower tailpipe emissions levels. I personally worked on lean-burn engines for many years, and a lot of companies spent hundreds of millions of pounds on developing the technology, but in the end the NOx emissions were always at least ten times higher than for a catalysed engine. The danger to public health from these emissions was, rightly in my view, seen as a price that was not worth paying for better economy. Aftermarket modifications to cars that may give fractionally better economy at the expense of vastly increased NOx (eg air bleed devices) are specifically banned in the US, with large fines imposed on anybody who "tampers" with their car in this way - hopefully it is now clear that this is for sound public health reasons, not because of an oil company conspiracy. By the way, claims that the catalyst does not start working until the car has been driven five miles or more are entirely wrong. The standard European emissions test is less than seven miles, and the catalyst is working for the vast majority of this. On the most recent cars, the catalyst is active within a minute of starting the engine. A minute after that, it is converting 99% or more of the toxic pollutants to harmless gasses - the emissions with the "cat" are only a hundredth of emissions without it. It is also not true that catalysts "die" after just a few tens of thousands of miles. Car makers must certify that their vehicles still meet the strict emissions standards (meaning that the cat must still be working efficiently) after 100 000 miles of normal driving. In a few rare cases catalysts do fail before this, but on any vehicles sold in Europe after 2000 (or in the USA after about 1997) this is automatically detected by the engine management system and a warning light on the dash illuminated. The catalytic converter (which is poisoned by lead) is also the primary reason why unleaded petrol was introduced, although there undoubtedly are health issues with lead as well. Many people observe that unleaded petrol, with its high benzene content, is pretty nasty stuff as well - it is, but because the cat does such a good job of cleaning up the unburnt hydrocarbons in the exhaust we are still better off than with leaded petrol and no cat. The cat (and associated lambda sensor) are of course frequently cursed by owners of older cars faced with large repair bills. This is quite understandable, but it is well known that a very small proportion of highly-emitting cars generate most of the toxic pollution in our environment. To achieve the same clean-up, you could either spend £500 on repairing one old car, or add £50 of extra technology to 100 new cars. The former is clearly more cost-effective. However, despite all the above, lean-burn is not totally dead. Stratified-charge direct-injection engines (such as Audi's FSI and Ford's SCi) use an extremely lean mixture with fuel concentrated near the spark plug to help it burn. This reduces NOx to very low levels, and the engines also employ an additional "NOx trap" to store and destroy the NOx. In this way the required emissions levels can be met, while still giving very good fuel economy. Unfortunately these engines are very expensive to make, because of the complex technology involved, and also require ultra-low sulphur fuel to give their best. As a result they have had limited sucess in the marketplace, but seem to indicate the likely future for the petrol engine.
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06-15-2008, 02:48 AM
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The above article is from the above excellent website Fuel saving - a professional engineer's view
He knows a thing or two
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06-15-2008, 03:48 PM
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One thing that most everyone seems to overlook, is the effect hydrogen and additional oxygen has on the production of NOx. You take a modern-day engine that runs at 14.7:1 and add a bit of hydrogen and oxygen. You are then able to lean the gasoline out to, say 18:1 or leaner (depending on the amount of hydrogen) with greatly reduced tailpipe emissions, NOx included.
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06-15-2008, 04:57 PM
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Read through his stuff and see if YOU want to accept everything he says as 100% accurate. 
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06-15-2008, 06:08 PM
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I would like to answer your various excellent comments, but will to do it after Wednesday, the 18th. However, I will tackle one issue. You are right, of course, that the culprit for lean burn is NOx. But in Poulton's book, Chapter Lean-burn, 1994, Page 43, we achieved 0.15 gm/mile using FTP-75 at an EPA recognized facility, weighting the air-fuel mixture more with EGR than lean burn, i.e. lean-burn at only light loads where fuel economy is worse. We achieved 11% better fuel economy. By the way, the NOx 2004 standard was 0.2 gm/mile. While a powerful lean lean burn system cannot compete with a stoich car for NOx, at above, say 0.4 MAP, it can go to stoich with very high EGR, e.g. 40%, and can beat the pants off a standard stoich car for NOx. Remember, NOx greatly increases with load. Also, we have shown this with a homogeneous mixture, i.e. a much simpler engine system.  All the best, Maddog. Michael
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06-20-2008, 09:36 PM
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Greetings,
This is the most fascinating thread I've read in a long, long time. On the fuel-supply side of things, however, there's been relatively little commentary in this thread. Surely there is at least one aftermarket EFI engineer lurking in the background here for whom this thread has provided much food for thought? If David believes a carburetter (just trying the English spelling for variety,) looks promising, then how much more TBI or direct-port EFI running in feedback with a wideband O2 sensor? The possibilities would see almost endless... Thank you, Mark
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06-21-2008, 12:17 AM
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There's a guy that developed a spark plug that can fire a 30 to 1 AFR and with more power.
I have put together a fuel system that can run an engine very cleanly on a 30 to 1. There are other poeple that have done it too.
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