LostKiwi
Senior Member
- Joined
- Aug 25, 2006
- Messages
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- Midlands / Charente-Maritime
- Your Mercedes
- '93 500SL-32, '01 W210 Estate E240 (RIP), 02 R230 SL500, 04 Smart Roadster Coupe, 11 R350CDi
And thats the 10% thing. In order to feel a difference there would need to be close to a 10% improvement in power so if you claim to feel the difference you are either suffering from Placebo effect (i.e. deluding yourself) or you are significantly better at detecting small changes than the vast majority of people (including professional drivers).
You are almost correct in the rest of your post...
1. More air does not (as you correctly said) equal more power. Neither does more fuel (as you incorrectly said). The amount of additional fuel MUST be in proportion to the amount of air and will usually be close to the stoiciometric ratio (12.5:1 in a petrol engine is the stoichiometric ratio and maximum power is usually a 12:1 ratio or close to it). A modern injection engine will maintain the appropriate mixture for the air automatically as governed by Lambda control except at wide open throttle when the engine will run off the map with no override from the O2 sensors.
2. More air available does NOT increase fuel economy. For maximum economy the fuel mixture needs to be leaner than the stoichiometric ratio (typically it needs to be around 15:1 or for hyper efficient lean burn engines even 20:1 or more!) Less restriction to flow will improve economy AND power but that's not the same thing as more air. At low throttle openings there is a vast over capacity of flow for the small amount needed for a petrol engine at light throttle, which is when it will be returning economy. As the mixture in a modern injected engine is under lambda control at light throttle even a clogged filter will have a very limited effect on economy (unlike carburettor engines where it will make the mixture over rich and harm economy severely).
At this point we aren't dealing with air - we're dealing with exhaust and that has totally different characteristics due to heat and residual combustion turbulence.
Incorrect. Manufacturers spend a significant amount of money designing and reviewing exhaust design. My other half worked for a manufacturer on purchasing exhaust systems (hot and cold ends) and was regularly involved in meetings where the design had changed to implement improved efficiencies. Some of the design criteria may be different (refinement and packaging for example) but given the way manufacturers are chasing emissions and economy (the two are linked) the design in a modern engine is often difficult to significantly improve on as what is good for economy is often good for power. Many aftermarket systems do not deliver as in many cases they are done to a 'visual' if it looks right it is right methodology or are made to operate better over a very narrow power band (useful for headline marketing statements) whilst being inferior over the rest of the rev range.
Your car (SL350) is a normally aspirated petrol engine. A remap for an NA car will often map the pedal response differently to standard and advance the ignition as far as allowable. The former makes the car 'feel' more responsive as smaller pedal inputs mat to larger throttle movement over the initial part of the pedal travel. Just that alone can give the impression of more power.
Advancing the ignition timing can give a useful increase in power 10% (if you're lucky), even with a K&N, unless the original map was very poor or unless the new map changes the fuel usage from 95RON to 98RON.
You may have felt an improvement with the remap (and I'd be surprised if you hadn't given the pedal will have been 'adjusted') but I would really not expect you to see any noticeable difference with the K&N.
Even on the video links you posted (which is just some bloke with a Nissan so pretty 'random' in its own right) he only saw 5% difference which would no way be noticeable.
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