• 1999-2002 Si Dyno Results


    1. 2000 Civic Si

    Comptech Ice Box vs. Stock
    Dyno Result
    http://www.comptechusa.com/images/dy...ic_si_plot.pdf

    2. 2000 Si

    Comptech I/H/E vs Stock

    Dyno Results
    http://www.comptechusa.com/images/dy...icsi-build.pdf

    3. 2002 Si

    AEM CAI vs Stock
    Dyno Result
    http://www.aempower.com/pdf/results/21-5082002CivicSI_CAS.pdf

    AEM Short Ram vs Stock
    Dyno Result
    http://www.aempower.com/pdf/results/22-508_2002CivicSISRS.pdf

    4. 2003 Si

    Comptech H/E vs Stock
    Dyno Results
    http://www.comptechusa.com/images/dyno/03si-h-e.pdf


    5. 2002 Si

    Injen CAI vs. Stock

    -----------
    Dc-Sports 4-2-1 vs 4-1 vs Stock

    Mods: Stock
    Peak HP: 139.2
    Peak TQ: 100.0


    Mods: DC Sports 4-2-1 header
    Peak HP: 142.9
    Peak TQ: 103.5


    Mods: DC Sports 4-1 header
    Peak HP: 140.9
    Peak TQ: 104.0


    1. What's the difference between an Si and a SiR?
    The SiR is the Canadian version of the US Si.

    Canadian SiR=Us Si

    Canadian Si=Us Ex


    The only differences that there are between the US Si and the Canadian SiR are:

    1. The SiR is also available in VSM (Silver)
    2. The SiR has heated mirrors.
    3. The SiR has anti lock breaks (ABS)
    4. The SiR has a slightly larger washer fluid Reservoir.

    What is VTEC and how does it work?
    *Lets see how DOHC VTEC works. The figure to the right shows a simplified representation of a intake-valve VTEC mechanism (the exhaust mechanisms work similarly). So for each pair of valves, there are three cam lobes. The two on the outside are low RPM lobes and the one in the middle is the high RPM lobe. The two low RPM lobes actuate the two valve rockers, which in turn pushes the valves open. The high RPM lobe actuates a follower, which is shaped like a valve rocker, but doesn't actuate any valves. The figures show the circular section of the cam lobes touching the valve rockers, and the elliptical section pointing away. Thus the valves are closed in this stage.



    During low RPM operations, the two outer cam lobes directly actuates the two valve rockers. These low PRM lobes are optimized for smooth operation and low fuel consumption. The high RPM lobe actuates the follower. But since the follower isn't connected to anything, it doesn't cause anything to happen. This process is illustrated by the figure to the right.


    At high RPMs, oil pressure pushes a metal pin through the valve rockers and the follower, effectively binding the three pieces into one. And since the high RPM lobe pushes out further than the low RPM lobes, the two valve rockers now follow the the profile of the high RPM lobe. The high RPM lobe's profile is designed to open the valves open wider, and for a longer duration of time, thus allowing more fuel/air mixture to enter the cylinder. The improved breathing allows the engine to sustain its torque output as RPM rises, thus resulting in higher power output



    That is basically how VTEC works. The picture to the right is a picture of an actual DOHC VTEC engine. Note that there are two cam shafts, one for the intake valves and one for the exhaust valves. For each pair of valves, notice that there are three cam lobes: two cam lobes on the outside, and one cam lobe in the middle.


    *The information provided came from http://www.leecao.com/honda/vtec/dohcvtec.html

    To sum it all up...

    VTEC: Variable Valve Timing and Lift Electronic Control.

    “VTEC is an electronic and mechanical system in some Honda engines that allows the engine to effectively have multiple camshafts. As the engine moves into different RPM ranges, the engine's computer can activate alternate lobes on the camshaft and change the cam's timing. In this way the engine gets the best features of low-speed and high-speed camshafts in the same engine.”

    Basically VTEC is a system that allows the engine to act as two totally different engines all in one. When in the lower RPM range the engine operates smoothly, quietly, and fuel efficiently. However, once you reach the higher RPM range (*5500+) the engine turns into a completely different machine. It turns into a power hungry, gas guzzling race engine.

    *VTEC will engage in the 99-00 Si/SiR at ~5500 RPM

    -you know about the valves that let air into the engine and let exhaust out of the engine. You also know about the cam shaft that controls the valves. The camshaft uses rotating lobes that push against the valves to open and close them. This is an animation from How Car Engines Work to help understand how the cam shaft opens and closes the valves:

    It turns out that there is big relationship between the way the lobes are ground on the camshaft and the way the engine performs in different RPM ranges. To understand why this is the case, imagine that we were running an engine extremely slowly - at just 10 or 20 RPMs, so it took the piston seconds to complete a cycle. It would be impossible to actually run a normal engine this slowly, but imagine that we could. We would want to grind the cam shaft so that, just as the piston starts moving downward in the intake stroke, the intake valve would open. The intake valve would close right as the piston bottoms out. Then the exhaust valve would open right as the piston bottoms out at the end of the combustion stroke and would close as the piston completes the exhaust stroke. That would work great for the engine as long as it ran at this very slow speed.
     
    When you increase the RPMs, however, this configuration for the camshaft does not work well. If the engine is running at 4,000 RPM, the valves are opening and closing 2,000 times every minute, or 3 to 4 times every second. When the intake valve opens right at the top of the intake stroke, it turns out that the piston has a lot of trouble getting the air moving into the cylinder in the short time available (a fraction of a second). Therefore, at higher RPMs you want the intake valve to open prior to the intake stroke - actually back in the exhaust stroke - so that by the time the piston starts moving downward in the intake stroke the valve is open and air moves freely into the cylinder during the entire intake stroke. This is something of a simplification, but you get the idea. For maximum engine performance at low engine speeds the valves need to open and close differently than they do at higher engine speeds. If you put in a good low-speed camshaft it hurts the engine's performance at high speeds, and if you put in a good high-speed camshaft it hurts the engine's performance at low speeds (and in extreme cases can make it very hard to start the engine!).

    It turns out that there is big relationship between the way the lobes are ground on the camshaft and the way the engine performs in different RPM ranges. To understand why this is the case, imagine that we were running an engine extremely slowly - at just 10 or 20 RPMs, so it took the piston seconds to complete a cycle. It would be impossible to actually run a normal engine this slowly, but imagine that we could. We would want to grind the cam shaft so that, just as the piston starts moving downward in the intake stroke, the intake valve would open. The intake valve would close right as the piston bottoms out. Then the exhaust valve would open right as the piston bottoms out at the end of the combustion stroke and would close as the piston completes the exhaust stroke. That would work great for the engine as long as it ran at this very slow speed.

    When you increase the RPMs, however, this configuration for the camshaft does not work well. If the engine is running at 4,000 RPM, the valves are opening and closing 2,000 times every minute, or 3 to 4 times every second. When the intake valve opens right at the top of the intake stroke, it turns out that the piston has a lot of trouble getting the air moving into the cylinder in the short time available (a fraction of a second). Therefore, at higher RPMs you want the intake valve to open prior to the intake stroke - actually back in the exhaust stroke - so that by the time the piston starts moving downward in the intake stroke the valve is open and air moves freely into the cylinder during the entire intake stroke. This is something of a simplification, but you get the idea. For maximum engine performance at low engine speeds the valves need to open and close differently than they do at higher engine speeds. If you put in a good low-speed camshaft it hurts the engine's performance at high speeds, and if you put in a good high-speed camshaft it hurts the engine's performance at low speeds (and in extreme cases can make it very hard to start the engine!).
    VTEC (which stands for Variable Valve Timing and Lift Electronic Control) is an electronic and mechanical system in some Honda engines that allows the engine to effectively have multiple camshafts. As the engine moves into different RPM ranges, the engine's computer can activate alternate lobes on the camshaft and change the cam's timing. In this way the engine gets the best features of low-speed and high-speed camshafts in the same engine.

    Variable Valve Timing and Electronic Control. It works by adding an additional cam lobe that alters valve timing duration and lift to improve engine breathing and boost output for a smoother more powerful response. Both Honda and Acura use the VTEC system in various performance-oriented vehicles, such as the Honda Civic Si, the Honda Civic EX, the Honda Civic delSol Si and delSol VTEC, and the Honda Prelude Si and Prelude VTEC. There are variations on this sytem that include different lobe profiles on the exhaust valves as well.



    Just an example of SOHC VTEC vs. SOHC Non-VTEC

    Civic: DX
    Type: Aluminum-Alloy In-Line 4
    Displacement (cc0 1590
    Horsepower @ rpm 106 @ 6200
    Torque (lb.-ft. @ rpm 103 @ 4600
    Compression Ratio 9.4:1
    Valve Train: SOHC 16-V
    Fuel System: Multi-Point Fuel Injection
    Ignition System: Electronic
    Final Drive Ratio (MT/AT) 4.06/4.36



    Civic: EX
    Type: Aluminum-Alloy In-Line 4
    Displacement (cc) 1590
    Horsepower @ rpm 127 @ 6600
    Torque (lb.-ft. @ rpm)107 @ 5500
    Compression Ratio 9.6:1
    Valve Train: VTEC
    Fuel System: Multi-Point Fuel Injection
    Ignition System: Electronic
    Final Drive Ratio (MT/AT) 4.25/4.36