Talk:Forced induction
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Merge alternative capitalisation
[edit]This article 'Forced_induction' needs to be merged with 'Forced_Induction' 65.13.158.13 20:07, 11 January 2007 (UTC)
- Note: This merge was done following the above message. Yaris678 (talk) 12:32, 5 December 2014 (UTC)
Needs references
[edit]This article needs any references to "cylinders" changed to "combustion chambers," as rotary engines do not have cylinders or pistons. [[User:jmkogut] 19:38, 14 November, 2008
Additional forced induction method
[edit]I believe there is an additional forced induction method not commonly known (whose name I forget). This involves an engine driven cylinder which in turn contains secondary cylinders or 'pulse tubes' about a common preimiter. The exhaust charge compresses an inlet charge down each pulse tube as the unit rotates. I understand this was adapted from use in Lamborghini tractors by the Ferrari F1 team for testing in the F1 turbo era but proved problematic. Does anyone have a reference to this? TurboMech (talk) 22:43, 18 January 2009 (UTC)
Second paragraph needs help
[edit]The second paragraph of the Introduction section needs help. It currently reads:
"High compression on a naturally aspirated engine can reach the detonation threshold fairly easily. However, a forced induction engine can have a higher total compression without detonation because the air charge can be cooled after the first stage of compression, using an intercooler."
This is at least misleading, if not completely incorrect. Naturally aspirated engines are designed with piston strokes which necessarily (to be competitive) result in higher compression ratios. It's not abnormal these days to find a Naturally aspirated engine with a compression ration over 11:1. Conversely, forced induction engines tend to have much lower compression ratios, in the neighborhood of 8.5:1. The reason naturally aspirated engines can reach the detonation threshold fairly easily is because they are already operating with higher in-cylinder temperatures at higher absolute compression ratios. Forced induction cars will typically over modulate fuel delivery to enrich the mixture beyond the normal stoichiometric ratio (14.7:1) to reduce the tendency to pre-combust and reduce cylinder temperatures, especially on highly tuned engines. While the same technique can be used in normally aspirated cars, a properly working normally aspirated car typically has very little need for this mechanism as a primary control of combustion.
Additionally, the statement that forced induction motors can have a higher _because_ the air charge is cooled by an intercooler is misleading as to the purpose of an intercooler. During forced induction compression (via a turbo- or super-charger) the air is compressed, and thus heated above ambient. The purpose (and in most implementations, the capability) of an intercooler is to lower the air temperature back to closer to ambient temperature. Reducing the air temperature below ambient is not possible in nearly all intercooler configurations, except some water-to-air intercoolers and possibly some prototype intercoolers using phase change cooling. You will not find the latter in any commercial application, and the former is implemented in only a very few today. Normally aspirated engines already ingest air at ambient temperature, so an intercooler would be completely ineffective in reducing the tendency for knock in such engines.
In summary, these two sentances should read something more like:
"The high compression ratio used in normally aspirated engines can more easily result in detonation if air, fuel, and temperature parameters are not well managed. However, most forced induction engines have lower compression ratios and use a number of advanced fuel management techniques to help control the combustion temperature and pressure." (With the possible addition of) "While forced induction applications do result in higher air temperatures after the compressor stage, which would normally increase the tendency to detonate the fuel charge, an intercooler is often employed to bring the temperature of the air mass back to near ambient temperature."