[w00t692]

Ok, guys, I've seen plenty of threads asking about the differences between the Si and the EX. I figured it was time to put a technical thread together to answer these question in one place. To keep this even, I will try to just compare the manual tranny versions.

Honda Civic Si Vs. Honda Civic EX

Si-K20Z3(6sp)
* Displacement : 1,998 cc (121.9 cu in)
* Compression : 11:1
* Power: 197 bhp (147 kW) @ 7800 rpm (sae NET Rev 8/04)
* Torque: 139 ft·lbf (189 N·m) @ 6200 rpm (sae NET Rev 8/04)
* Bore and Stroke: 86.0 x 86.0 mm (3.385 x 3.385 inches)
* Redline: 8000 rpm
* Fuel Cutoff: 8200 rpm
* i-VTEC Engagement Window:5800 rpm

The Si's "i-VTEC" system includes variable cam timing, which modifies the intake cam timing to produce superior torque throughout the power band. The cam angle variation is from 0-50 degrees.

EX-R18(5sp)
* Displacement: 1,799 cc (109.8 cu in)
* Compression: 10.5:1
* Bore & stroke: 81.0 × 87.3 mm (3.19 × 3.44 in)
* Power: 140 PS (103 kW; 138 bhp) @ 6300 rpm (Japanese Spec)
* Torque: 17.7 kgf·m (174 N·m (128 ft·lbf)) @ 4300 rpm
* VTEC window: 4800 rpm
* Redline: 6800 rpm

Si-21/29MPG(I've gotten 34MPG on the highway going 75)
EX-26/34 MPG(any real life mileage?)

Weight/distribution(front/rear)
-Si 2895(coupe) 61/39, 2954(sedan) 60/40
-EX 2703(coupe) 60/40 , 2747(sedan) 60/40

Gear Ratios
Si- Gear Ratios: 1st: 3.267, 2nd: 2.130, 3rd: 1.517, 4th: 1.147, 5th: 0.921, 6th: 0.659, Reverse: 3.583, Final Drive: 4.76

Ex- 1st: 3.143, 2nd: 1.870, 3rd: 1.235, 4th: 0.949, 5th: 0.727, Reverse: 3.308, Final Drive: 4.29

Other performance differences
-Si has LSD
-Si has 40% stiffer springs
-Si has stiffer sways/different lower control arms
-Si brake rotors 11.8 / 10.2 (front/rear)
-EX brakes rotors 10.3 / 10.2 (front/rear)

Exterior differences
-Two Si badges
-Si has a full spoiler
-Ex has lip spoiler
-Si has 17x7 rims/215-45R17 tires
-Ex has 16x6 rims/205-55R16 tires
-Si has a chrome exhaust finisher

Interior differences
-Si has red accent lights
-Si has more supportive seats
-Si has suede accents
-Different shift knobs
-Si has drilled aluminum pedals

Other/Misc
-Si uses premium(91+), while Ex uses regular(87+)

If you have more to add, post it, and I will add it to this post. I'll add more as I find it. I hope this helps people decide, and prevents all the reposts.

These are just the minor changes i could make from looking at it, also added some info.

 

[w00t692]

No. It changes intake cam TIMING on the Si.

The R18 has NO cam timing changes whatsoever.

the r18 only has a modified version of vtec based on rocker lobes made for fuel economy.

The exhaust cam timing doesn't change for the si, it's a "true" version of vtec. It activates a higher lift cam.

 

[w00t692]

Notice something here?

left side: exhaust.... no VTC gear (although it does have some aftermarket adjustable cam gear)
right side: intake.... oh look a VTC gear.

OP: don't listen to people that have no clue what they are talking about, update your post with the information i provided.

 

[w00t692]

He is confusing VTC with VTEC.

VTEC is on both the intake and exhaust cams. It varies the amount of cam lift and duration by using the high lift higher duration cam lobe to increase power output.

VTC on the intake cam allows you to perfect your torque curve for maximum power output and smoothness of power delivery. It basically rotates the cam from 0-50 degrees.

i-VTEC is the combination of both of these technologies.

It is used this way on multiple Honda K-series engines in the US:

K20A2
K20Z1
K20Z3
K24A2 (VTC on this engine is only 0-25 degrees)

These are the engine codes that use i-vtec in the manner i described save the difference i mentioned for the K24A2.

 

[w00t692]

Yes, that is correct.

 

[w00t692]

All you silly bastards. Why the heck would i ever think the k20z3 doesn't have vtec on both camshafts!!

 

[w00t692]

Just out of curiosity,

Does not having a VTC on our exhaust camshaft add or gain any power to our
engine?

Not much. Exhaust VTC is much less important than intake VTC. I guarantee Honda tested dual VTC on both camshafts and wasn't impressed with exhaust VTC.