1. Variable Cam Timing
2. No VTEC on exhaust cams except for the RSX-S and Type-R models
3. Intake manifold is in the front
4. Exhaust manifold is in the rear
5. Engine spins clockwise instead of counter-clockwise
6. I believe but I may be wrong, that the new engines have direct port ignition
I think thats it.
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~00 Civic Si Reloaded~
I-VTEC stands for intelligent-VTEC. It works the same as any other VTEC engine, except the ECU now has timing control of the intake and/or exhaust cam. The ECU can advance or retard cam timing continuously through a range of 50 degrees.
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Originally posted by 2000 EBP Si I-VTEC stands for intelligent-VTEC. It works the same as any other VTEC engine, except the ECU now has timing control of the intake and/or exhaust cam. The ECU can advance or retard cam timing continuously through a range of 50 degrees.
This guy is right.....
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92 Honda Prelude Si (The rombus)
Originally posted by 2000 EBP Si I-VTEC stands for intelligent-VTEC. It works the same as any other VTEC engine, except the ECU now has timing control of the intake and/or exhaust cam. The ECU can advance or retard cam timing continuously through a range of 50 degrees.
Sorry no it doesn't work the same as any other VTEC. The i-VTEC in the new Si/SiR uses VTC and VTEC-E. Futhermore, the VTC control is only on the Intake Cam, it does not have variable control of both.
On the new Si: VTC + VTEC-E = i-VTEC
On the RSX-S: VTC + DOHC VTEC = i-VTEC
It's sort of mis-leading the way they label them the same when they really aren't at all.
For those that are curious, VTEC-E is a setup where you have two intake valves. One runs continous and the other opens just slightly to keep fuel from puddling on the valve. When it goes into VTEC then the second intake valve runs together with the first. All in all, it's not nearly as nice of DOHC VTEC as we are used to on the 6th Gen. In a VTEC-E setup you have 12-valves running in normal operation and 16 while in VTEC.
DOHC VTEC is where all 16 valves run all the time. The intake and exhaust both have their own cam and each cam has a two standard and one VTEC lobe. When in normal operation all four valves run on a regular set of cam lobes with slightly different profiles to improve swirl and combustion. When VTEC engages all four valves get to run on the VTEC Lobe which have a completely different profile and it's very aggressive. The VTEC lobe kicks in where the standard lobes leave off, so in effect you get two completely different power bands. That's how it makes power up to 8000 RPM so easily.
My conclusion:
The only i-VTEC engine worth a damn is the one in the RSX-S, because it uses the DOHC VTEC that we have in the 99-2000 Si/SiR's. Granted the new engines do produce more low end torque than the B16A did, however, they also have a Dual Plane intake and .4L displacement to help it out.
Added displacement and dual plane intake = good. VTEC-E = sucky. Put these two together and you now know why the new Civic is no faster than the old one.
Sorry no it doesn't work the same as any other VTEC. The i-VTEC in the new Si/SiR uses VTTC and VTEC-E. Futhermore, the VTC control is only on the Intake Cam, it does not have variable control of both.
On the new Si: VTC + VTEC-E = i-VTEC
On the RSX-S: VTC + DOHC VTEC = i-VTEC
It's sort of mis-leading the way they label them the same when they really aren't at all.
My conclusion:
The only i-VTEC engine worth a damn is the one in the RSX-S, because it uses the DOHC VTEC that we have in the 99-2000 Si/SiR's. Granted the new engines do produce more low end torque than the B16A did, however, they also have a Dual Plane intake and .4L displacement to help it out.
Added displacement and dual plane intake = good. VTEC-E = sucky. Put these two together and you now know why the new Civic is no faster than the old one.
God, that took me a long time to type.
You're right. I should have been more specific. I was comparing the B series DOHC VTEC engines to the K20A2 engine from the RSX-S.
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dont the dual plane intake manifolds actually suck compared to the single large port ones. like the gsr vs the typer, i think the dual planes ones have a longer power curve, correct me if im wrong.
Originally posted by blueSI dont the dual plane intake manifolds actually suck compared to the single large port ones. like the gsr vs the typer, i think the dual planes ones have a longer power curve, correct me if im wrong.
No to my knowledge. The idea of the dual plane setup is to increase low end torque and at the high end open up to let the engine breathe for increased high end.
A single large port intake can actually decrease performance in the low end. Just look at an AEM for example. Most dyno results I have seen show only a gain in power at the high end of the power band and sometimes even a loss at the low end. A dual plane setup gives you the best of both worlds.
Honda does a dual plane setup for a reason, because they know it works.
No to my knowledge. The idea of the dual plane setup is to increase low end torque and at the high end open up to let the engine breathe for increased high end.
A single large port intake can actually decrease performance in the low end. Just look at an AEM for example. Most dyno results I have seen show only a gain in power at the high end of the power band and sometimes even a loss at the low end. A dual plane setup gives you the best of both worlds.
Honda does a dual plane setup for a reason, because they know it works.
no no i said dual plane intake manifold. like a gsr has as opposed to the type-r and si.
How important is runner length to the power output of a motor? Why do you think manufacturers are constantly trying to conjure up dual-runner intakes. The idea behind these multi-runner manifolds is to take advantage of the low-speed cylinder filling offered by the long runners and the impressive top-end power offered by the shorter versions. The Integra GS-R and older SHO Taurus are perfect examples of dual-runner intakes. The problem inherent in the dual-runner design is that the motor must switch breathing from one to the other or be forced to breathe from both. Switching from one to the other is difficult, so most manufacturers prefer simply opening up shorter runners to improve high-rpm breathing. The problem with sharing a pair of runners of different lengths is that there invariably will be turbulence caused by the differential in air speed through the two ports. This is especially important on 4-valve motors where each of the pair of intake valves breathe through an individual runner of different length. The Siamese runners do allow cross over breathing from one port to the other, but turbulence is still a problem.
How exactly does runner length effect power production? The suction from the downward-moving piston draws air in through the cylinder head and intake manifold. The column of air is sped through the port from the suction. The column of air travels the length of the intake runner and finally reaches the intake valve in the cylinder head. At some point, the intake valve closes, but the column of air is still moving forward toward the valve for a short period of time. This elastic nature of the column causes pressure to build up behind the intake valve. This pressure persists until the valve reopens, causing a type of forced induction into the combustion chamber. The engine speed of this supercharging effect is determined by the length of the intake runner. Longer runners require more time (relative to engine speed) for the air to travel from the opening (throttle body) to the intake valve. At some engine speeds, the intake valve will simply not be open long enough for the air to travel the length of the long runner. The supercharging effect will be eliminated, and so will power.
Shorter intake runners provide a similar supercharging effect, just at a higher engine speed. A shorter runner requires more suction (or negative depression) in the form of engine speed or increased displacement to produce the same air speed as a longer runner. The downside of the shorter runner is that the air speed is down at lower engine speeds and, as such, so is the power production. Short of resorting to some trick, dual-runner intake, the best bet is to optimize the runner length for a given engine speed. Actually, engine speed is a bit misleading, as intake runner length will produce efficient power over a given range rather than at a single engine speed. The manifold must be designed to run effectively in the desired operating rpm (say from 2,500 to 5,500 rpm). A towing application, for instance, would benefit most from the torque produced by a long-runner intake, while a race car might benefit most from the high-rpm power of a short-runner intake. Manufacturers typically error on the side of long runners, as these produce what most drivers in America want–namely, good throttle response and low-speed torque.
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dual plane intake runners have a longer powerband for instanse a gsr vtec kicks in at 4700 and last to the moon an sivtec starts at 54 and last the same but y did honda put a large single plain to the type-r easy shorter runners = faster throttle response and shorter powerband. imo i think the dual runners suck for racing it limits the breathing of the engine. look at a gsr dyno chart with a single plane intake, makes the same power down low as the double plane, double plane really doesnt work as good as honda enginers figured it would.
What's the difference?
Linear Mode
