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SI vs NON-SI

Dimitron84

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So as title says what is actually difference? Speaking engine alone, I know the SI has the sport mode to adjust throttle response and stiffen steering and suspension. However what is different about the SI engine vs any other 1.5T Civic, is it simply just a tune to increase boost or did Honda actually make our engine stronger to handle the extra boost?



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odinist

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Exhaust side on the Si turbo has a different fin count. I want to say I read the connecting rods are different too?
 

inertiadrifto86

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Differences between the Si and Non-Si level trims, from the Honda Civic Si wikipedia page:

  • engine output increased to 205 HP @ 5,700 RPM (SAE net) and 192 lb-ft torque @ 2,100-5,000 RPM (SAE net)
  • higher maximum boost pressure (20.3 vs. 16.5 PSI)
  • lower compression ratio (10.3:1 vs. 10.6:1)
  • higher-capacity MHI TD025 turbocharger (9-vane vs. 11-vane)
  • helical limited-slip differential
  • larger front brake rotors (12.3" vs. 11.1" vented front and 11.1" vs. 10.2" solid rear)
  • two-mode damper system with normal and firm settings
  • SPORT mode replaces ECON mode - increases suspension damping, reduces power steering assist, increases throttle sensitivity, and raises the activation threshold of the Vehicle Stability Assist system
  • 235/40R18 91W tires vs. 215/50R17 91H
  • 7% stiffer front spring rate
  • 18% stiffer front upper damper mounts
  • 7% stiffer front stabilizer bar rate
  • 32% stiffer rear spring rate
  • Solid vs. fluid-filled front and rear compliance bushings (rear shared with the Type R)
  • High-stiffness rear upper control arms (shared with the Type R)
  • 26% stiffer rear stabilizer bar rate
  • Si-specific seats with thicker side bolsters, non-adjustable headrests, and stitched "Si" logos
  • red interior stitching, gauges, and Display Audio color scheme
  • black headliner and pillar trim vs. gray in EX-T
  • front and rear facias similar to the hatchback
  • center-mounted polygonal exhaust outlet
  • higher-flowing intake system
  • 23% higher-flowing exhaust system
  • aluminum clutch, brake, and accelerator pedals
  • carbon fiber-look interior trim
  • 10% shorter shifter throw
  • leather-wrapped, aluminum shift knob
  • revised shift linkage
  • increased rigidity of shifter bracket mount
  • 450-watt audio system (same as EX-T coupe vs. 180-watt in EX-T sedan)
  • additional items in Driver Information Display including G-force meter, turbo boost gauge with PSI indication, lap timer, throttle percentage, and brake pressure
  • leather-wrapped steering wheel, shift boot, and shift knob
  • premium fuel recommended
  • tire repair kit including sealant and a 12-volt inflator replaces the compact, temporary spare
  • vanity mirrors are non-illuminated vs. illuminated
  • EPA fuel economy ratings of 28/38/32 city/highway/combined vs. 31/42/3
I do remember there being some changes to the internal engine components as well. I'm going to do some additional quick research and see if I find anything.
 

WOPSiWOT

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So as title says what is actually difference? Speaking engine alone, I know the SI has the sport mode to adjust throttle response and stiffen steering and suspension. However what is different about the SI engine vs any other 1.5T Civic, is it simply just a tune to increase boost or did Honda actually make our engine stronger to handle the extra boost?
What is said above. The rods are also different. And same as CRV (turbo also from CRV). Rods are a bit harder. There is a thread about it if you search. It is not a dramatic difference.
 

repeet

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I was checking the online Honda parts catalog to see what Si engine parts have a different part number from the standard 1.5T.

Below are the parts that are changed for the Si 1.5T engine:
Intake Camshaft
Turbo Assembly
Fuel Injector Set
Pistons (Si has a lower compression ratio at 10.3 from 10.6 to handle more boost)
Connecting Rods
Powertrain Control Module

For the transmission:
The Differential, Mainshaft and Flywheel are different from the standard 1.5T 6M.
For anyone wondering if the different part number connecting rod the Civic Si engine got makes it any different, I ordered a "base" 1.5T rod and a Civic Si unit.

As far as my dial calipers can tell, they're dimensionally the same. The bushing for the wrist pin on the Si rod has a visibly smoother finish than the base model rod, but other than that, I don't see a difference. If I get real nitpicky, the color and sheen of the Si rod is SLIGHTLY different, but that may just be a result of the batch each rod was manufactured in.

There has been a handful of accounts of "base" 1.5T rod breakage, so I decided to have the material of each rod tested for hardness.

The results are:
Base = 22 HRC
Si = 28 HRC

The Civic Si rod is definitively harder on the Rockwell scale than the "base" 1.5T rod.

I would also like to note that the rod thickness is just 1.3mm thinner than a K20A2 "PRB" connecting rod at the thinnest parts.

I hope this comes in handy for everyone.

Thanks!

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mis3

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The LSD alone is just about worth the extra 1-2K of the price difference.
It would be great if I can drive a non-SI for a day to appreciate how good is this LSD.

I did 3 test drives of the non-SI. I was focused on the CVT, not much on the handling. My original plan was to buy a Touring.
 

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The Si is a great car, no doubt. I'm hoping my +6 tuned EX-L sedan with the Si rear sway bar, Ultra Racing front strut brace and upcoming ultra high performance tires will up the fun factor. It won't quite be an Si in the twisties but power-wise I should be as fast or faster.
 

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The Si is a great car, no doubt. I'm hoping my +6 tuned EX-L sedan with the Si rear sway bar, Ultra Racing front strut brace and upcoming ultra high performance tires will up the fun factor. It won't quite be an Si in the twisties but power-wise I should be as fast or faster.

From a stop you'll have one wheel peel and major torque steer while and Si will get much better traction having the LSD.
 

babinjm

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From a stop you'll have one wheel peel and major torque steer while and Si will get much better traction having the LSD.
Yes what he said. Without LSD a non Si will be a one wheel peel machine. In addition, the turbo differences will make a difference if you really want to tune.
 

BoostedSiCoupe

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theres controversy regarding the differences in the internals. from the long ass thread about them it was concluded that the si's rods are only slightly harder than the non si rods. it really makes u wonder how much more boost they can hangle in thee long run. im currently running the +6 FP calibration. i dont feel comfortable running the +9 ass i feel it will compromise the engines longevity.
 

Ataricade

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theres controversy regarding the differences in the internals. from the long ass thread about them it was concluded that the si's rods are only slightly harder than the non si rods. it really makes u wonder how much more boost they can hangle in thee long run. im currently running the +6 FP calibration. i dont feel comfortable running the +9 ass i feel it will compromise the engines longevity.
Actually the hardness difference it quite significant if you understand the scale. That said they are only designed for stock boost levels.

If performance is what you want and you cant swing an R. The Si is your choice. It is much more performance orientated. The LSD is worth the cost increase alone.
 

BoostedSiCoupe

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Actually the hardness difference it quite significant if you understand the scale. That said they are only designed for stock boost levels.

If performance is what you want and you cant swing an R. The Si is your choice. It is much more performance orientated. The LSD is worth the cost increase alone.
So you basically are confirming what i said, theyre not strong enough to handle the extra boost in the long term.
 

Sly_Si

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So you basically are confirming what i said, theyre not strong enough to handle the extra boost in the long term.
But, knowing Honda, they always overbuilt their cars.. they also know that people bought the Si for the performance, and most likely to modify it to increase the power level..

The +9psi doesn't give much increase from +6psi, and as long you don't do the Scramble mode and improve throttle response, the torque curve feels pretty smooth, that's good for your internals.

Not to mention this 10th gen civics have lower redline.

But that's my 2cents though, i trusted my Civic Si with +9psi more than my friends 94 built Del Sol Si with increased 10k rpm.
Aaaaaand i spent less money than him LOL
 

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