目前看來,應該是燃油直噴引擎可能都會如此,因為以前的噴射引擎,汽油噴到進氣閥也有清潔的效果,附檔是 Golf GTI 的進氣歧管與進氣閥高里程的照片:
http://www.golfmkv.com/forums/showthread.php?t=169255
http://www.more-bhp.com/20tfsi_42fsi..._cleaning.html
節錄幾段比較關鍵的文字:
This carbon build up is up to 2mm thick in places and is a common problem for modern direct injection engines and stems from the crank case ventilation system redirecting oil vapours through the inlet manifold to be burnt up. Previous engines with port or inlet injection (such as the 1.8T 20V) did not suffer with this problem as fuel was mixed with the air prior to flowing over the intake valves and therefore the fuel washed any carbon deposits away. As ever, vehicle manufacturers are trying to increase efficeincy and are choosing direct injection (where fuel is injected directly into the combustion chamber) over port injection for their engines. All of the Volkswagen / Audi / Seat / Skoda FSI or TSI engines are direct injection and suffer from carbon build up.
Carbon build up is a natural occurance on direct injection engines and there is pretty much no way of stopping it. Sophisticated catch cans and alternative oils are said to help prevent the build up but will not stop it completely. Generally speaking an engine with only 20,000 miles on the clock will have a sufficient build up of carbon, so we recommend having your intake valves checked at these intervals. Constant misfires, lack of responsiveness and poor fuel economy can also be related and cured by having this service carried out. If you leave the carbon to build up then these problems can only worsen and possibly cause major damage if a sizable carbon pellet falls into the cylinder.
Even though, peak power is exactly the same, there are surprisingly large increases in torque between 1,500 and 5,000 RPM.
大意是說,進氣端的積碳是源自於燃油直噴+廢氣回收所造成,約莫 20000 英里建議要清潔,並換掉對應的襯墊,清潔後最大馬力幾乎不變,但扭力會明顯提升, 如果任由它髒而不清,有可能積碳脫落跑道氣缸內就不好了...
我的車是汽油 2.0 直噴渦輪引擎,也跑 12.5 萬沒清過了,最近也在找資料看 DIY 後如何依照原廠建議的扭力值把螺絲鎖回去... 但這扭力資料我還找不到...
最後, 清潔時, 活塞需在上死點, 避免髒汙跑進氣缸, 如果噴油嘴在附近也要做適當的防護,且換後最好換機油.已液免有少部分的髒污跑到機油中.