As boost pressures get higher, the amount of power lost from a reduction in unswept volume is multiplied. If the means used to achieve this ultra-high compression ratio reduces the combustion efficiency (percentage of air-fuel mixture burned in the cylinder), a slightly lower compression ratio that doesn’t have this impact will be ideal. In addition to understanding the effects of raising or lowering an engine’s compression ratio, you also need to understand how fuel octane, alcohol percentages, type of fuel injection (port or direct), boost levels and types of driving will factor into selecting the ideal compression ratio for your application. This bad judgement is usually the result of the “if a little is good, more is better” mentality. Compression ratio isn’t the only factor, of course. These effects have nothing to do with feelings or emotions. There is more to it than that. This could mean that the engine is already accelerating faster before the boost “kicks” in. If you want to compress something to use as little space as possible, you should definitely use 7z. The original OEM compression ratio of your engine is the ideal compression ratio for the engine. If your application desires more power off-boost and up to about 20psi, raising the compression ratio should be considered if the fuel to be used has the knock-resistance required. If an engine is going to run on an exclusive diet of racing gas, compression ratios can be higher than pump gas. Join 350,000 subscribers and get a daily digest of news, comics, trivia, reviews, and more. There are power gains at high boost and power losses below 20psi of boost. But, if you want the best compression ratio possible, 7z is the way to go. For compression ratios between 8.0-to-1 and 12.0:1, the higher compression ratio engine will make more power when the boost is between zero and 20psi. Less fuel is required for each horsepower generated. It’s time to compress some files, so what format do you use? In short, we recommend: If you’re just compressing files for your own use, you can use whatever file format you like. Here is something that may surprise you. Finally, the type of racing and/or driving that the engine will be subjected to also influence ideal compression ratio. The OEM selects a compression ratio that is high-enough to deliver the highest thermal efficiency while being low-enough as to not induce knock (detonation) in the worst-case conditions. Of course, we need to define what is meant by “ideal.” The OEM compression ratio is ideal for the minimum octane rating of gasoline recommended, for the factory power output levels, for factory boost levels, for emission compliance and for a driving pattern that the OEM believes will be driven. Instead, these effects are rooted in science. This reduction in volumetric efficiency is the result of having less unswept volume that could be filled. O pinions are like assholes and everyone has one. For moderate-boost applications, compression ratio increases actually reduce peak power output at 29.4psi. But a 9.0:1 engine will make more power than an 11.0:1 engine from about 22psi to 30psi. We’re happy with our overall results, but you might see different results when compressing different types of data. By submitting your email, you agree to the Terms of Use and Privacy Policy. You’ll get different results with different data and types of data. To avoid being deceived, you need to take the time to understand the effects of raising or lowering an engine’s compression ratio. Some of these formats are just easier to use because they’re integrated into desktop operating systems, while some require third-party software. Chris has written for The New York Times, been interviewed as a technology expert on TV stations like Miami's NBC 6, and had his work covered by news outlets like the BBC. Since the burn speed of the air-fuel charge increases under higher compression ratios, the ideal spark timing for a higher-compression engine will have less advance than a lower-compression engine. How to Change the Theme and Accent Color of Instagram DMs, How to Record Shows and Movies on YouTube TV, How to Get Cycling Navigation Directions in Apple Maps. However, running the highest compression ratio possible doesn’t deliver the best performance for all performance applications. It depends on the data. For a drag application where you aren’t spending any time at low boost levels, a low compression ratio is more likely to be ideal. While the charts can help provide direction, nothing beats actual testing. Since less energy is wasted to the cooling system, the amount of temperature increase in the cooling system during a full-throttle pull will be less on a higher-compression engine than one with a lower compression ratio. Depending on the type of course, boost is limited between 19 and 21.7psi with a push-to-pass boost of 24psi. Compare and evaluate the two engines to see which delivers better results. Join 350,000 subscribers and get a daily digest of news, geek trivia, and our feature articles. The higher the boost pressure beyond this crossover point, the higher the power gain at the lower compression ratio. Since 2011, Chris has written over 2,000 articles that have been read more than 500 million times---and that's just here at How-To Geek. Even under these conditions, the factory compression ratio would not be too high. Opinions are like assholes and everyone has one. Since forced-induction wasn’t common until the early ‘90s and it was mostly fitted on imports, many old-timers never dealt with the negative performance tradeoffs of increasing the compression ratio on a boosted engine. Zip, RAR, 7z, or something else? Setting up an engine to run E85 instead of pump gas expands the range of possible compression ratios that can be run. This means more energy is extracted from the combustion process and less is wasted to the cooling system and exhaust system. When one only considers the difference that a compression ratio change makes on a engine’s thermal efficiency, this would be the following impact to fuel economy. This is more complicated than it seems. Nitrous Oxide? For a street application or circuit application, the off-boost and low-boost power increase from the higher compression ratio may be most ideal. WinZip also didn’t beat out the integrated Windows support for creating Zip files by that much. Or both? In part three, we will explore the best ways to reach the ideal compression number that lead to maximized combustion efficiency. If you do have an engine program for your racing team that allows engine development, try building two identical engines that have slightly different compression ratios (maybe a half-point apart). The lower compression engine will also make less power below the 20psi boost pressure mark. 7z is the least supported — it’s not integrated into any operating system, so you’ll have to install an application to open .7z archives. The silver line represents the original compression ratio of 9.5-to-1. The reason is that the alcohol has a much better cooling effect than gasoline when it vaporizes. In addition to understanding the effects of raising or lowering an engine’s compression ratio, you also need to understand how fuel octane, alcohol percentages, type of fuel injection (port or direct), boost levels and types of driving will factor into selecting the ideal compression ratio for your application. First, we installed Bastion and compressed its folder — about 863 MB in size of music, graphics, executable files, and various different types of documents: Next, we compressed Hotline Miami, which is 654 MB of data: The winner by pure compression is 7z, which isn’t surprising to us. He's written about technology for nearly a decade and was a PCWorld columnist for two years. You can even crank up the compression settings to save even more space, although it will take longer to compress and decompress. The volumetric efficiency improvements don’t really start to outweigh the reductions in thermal efficiency until the boost pressure exceeds about 20psi. The opposite occurs when the compression ratio is increased to 10.5- or 11.5-to-1. Here are the formats integrated into popular operating systems: Windows is the biggest stick-in-the-mud here — it only supports Zip files, so Zip is the most universal format. Easier to use as little space as possible, 7z is the ideal compression ratio,! 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