Wow you know alot about the i-VTEC SOHC on the 2006 Civic... when you say VTEC can be activated at any RPM, what do you mean exactly? I think it feels like there is a surge after 2000rpm.
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Wow you know alot about the i-VTEC SOHC on the 2006 Civic... when you say VTEC can be activated at any RPM, what do you mean exactly? I think it feels like there is a surge after 2000rpm.
Yup, it can be activated at any RPM. It could be 2000rpm, it could be 3000rpm, it could be 4000rpm. It all depends on the engine load and the amount of throttle you are giving. Based on engine load and throttle position, the ECU sends a signal to the hydraulic actuator so that the oil pressure is increased and can still operate the VTEC mechanism when the solenoid is activated.Quote:
Originally Posted by JaCe
When VTEC is activated, the engine runs like a normal engine that is out of VTEC. When not in VTEC, the engine is running in high efficiency mode (Miller cycle). But... your surge that you feel is not really from VTEC, but from your special intake manifold. If you look at the intake manifold on normal Honda engines, you see 4 tubes into the block (intake manifold in front for K and R series, at the back for B and H series). Your 06 Civic 1.8L has a twin length manifold. Long for low RPM and short for high RPM. So at high RPM (I'm not sure what RPM it is set to switch at), you get better breathing.
Pics here to show you the difference. (links I found on google).
Short: http://www.jazzproparts.com/photos/K20A-2.jpg
Long: http://www.a-oktw.com.tw/CD/AOK%20NE...HONDA/K20A.JPG
Examples of Hondas with short intake manifold: Integra DC2R, DC5R, Civics with b16a and b, EuroR.
Hondas with medium intake manifold: Accord Euro
Hondas with long intake manifold: CRV, Accord VTi, Integra Luxury, Jazz
Hondas with dual length manifold: 06 Civic VTi(L), DC2 Integra.
aaronng has honda give you a job in their tech dept yet mate?
I'm suprised you mange to rem all that.
I can't even rem my number plate number!
Haha, it's easy for me to remember these technical things because I've been technically-inclined since young. My dad used to tell me that when I was young (2 years old), my favourite toy was a pad lock and a bunch of keys. My past time was finding out which key opened the lock. LOL
When you refer to the dual length manifold for the civic 06. Is it only both VTI L and VTI or just VTI L?Quote:
Originally Posted by aaronng
WHoops. Both the VTi and VTiL are mechanically the same. So yeah, they both have the dual length manifold.Quote:
Originally Posted by jkz
Ahh thanks for that info aaron. I know this is going out on a whim a bit and is probably a subjective Q, but I've seen other Honda cars with i-VTec too; but they aren't the new Civic. Since they are DOHC, does that mean they are more advanced/better than my car?- or does i-VTec mean different things under different circumstances?
And thanks again for the info. It's pretty awesome. I think my car is starting to perform considerably better now that it's run-in (past the 3.5k mark).
All VTEC does is lets you use 2 cam profiles for your engine. Which means you have 2 RPM ranges where your engine can perform optimally. Each VTEC system is set based on what are the target objectives of the engine. In a performance orientated engine like the K20A, the objective is power, power and more power. For city cars like the Jazz, VTEC is used to run the engine in 12v mode for better low end torque so that the small engine can still have enough torque when you are in a traffic jam and can only rev to 2000rpm.Quote:
Originally Posted by JaCe
The civic on the other hand is made for todays world of high petrol prices. So its focus is fuel economy. That's where its VTEC is used. But, eventhough it is an engine designed for fuel economy, Honda put in molybdenum-coated pistons (DC2R engines and Jazz VTi), dual length intake manifold (DC2 VTiR engines), piston oil jets for maximum cooling and lubrication (only in the S2000 and K series engines) to have fuel efficiency and also power (103kW).
Compare it to its rivals in the same 1.8L segment:
Nissan Tiida: 93kW
Holden Astra: 90kW
Toyota Corolla: 93kW (used to be 100kW)
Want to compare it to more upmarket cars?
BMW 118i (2.0L): 95kW
Renault Megane 2.0L: 99kW
Ford Focus 2.0L: 107kW
So the civic's 1.8L has super fuel efficiency due to i-VTEC and yet has more power than other 1.8L rivals due to the special tweaks that have been used in higher performance engines.
Is that advanced? I'd say so. Any car company can use variable valve timing and lift to make lots of power. But none of them tried to make good power and yet have good fuel economy. Remember, most car companies get fuel economy by using drive by wire, variable valve timing, exhaust gas recirculation, throttle shut off when cruising. The Civic does all this and goes further. Only 2 cars has tried to use the same miller cycle system. That was Mazda Eunos 800 and a Subaru Turbo Hybrid. You probably have not heard of these cars because they were not that successful and their miller engines did not give any fuel efficiency benefits. They had to put a supercharger on to regain useful power and in the end negated the benefits. Honda did it with their VTEC system. Every car company uses VTEC/VVTL-i/VANOS/MIVEC/VVL to make power. None of them tried to exploit valve control to make a miller cycle engine that does not produce any less power than a normal engine!
Wow. Thanks again :)
I think that the transmission/drivetrain also plays a pretty important role because even though the Astra has 90kW... when you drive it (at least in automatic rendition) it feels like a slowpoke. Comparatively the Civic, whilst only 13kW more, feels considerably more powerful under all circumstances.
That's because it doesn't have any efficiency work done on it. No variable valve anything to boost low RPM torque. So its number are only valid when at close to the peak power and torque RPMQuote:
Originally Posted by JaCe
this man deserve some rep points
JACE, do u drive an auto? wot Rpm do u feel like the torque starts coming in?
i drive manual and its usually round 4000revs u start to feel it.