Variation of the 1.5l engine discussion

CivicXVII

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Update – I made a mistake. The Si engine does not have VTEC. This changes much of what I had previously written.

See corrected chart attached. Numbers in red font I calculated.


I recently purchased a 2018 Honda Civic Sport Touring Hatchback. I’m really enjoying the car and reading about it on this forum. I’ve been doing some research on the excellent 1.5l turbo in the current Civics, Accords, and CRV’s and thought a discussion of the variations of this engine might be interesting. I have looked at the data provided by Honda on these engines from the Honda website and I’m going to assume that information is correct when I make my observations.

I want to state right up front that I AM NOT CLAIMING TO BE AN EXPERT! I’m just a guy who is really into the technical aspects of engines. I had some classes on this in college but honestly I really don’t know much about tuning a turbo car. My car is not tuned and I know a lot of the people around here that actually do this stuff know a hell of a lot more than I do! I’m simply writing my thoughts and observations. I’m here to discuss, exchange thoughts, and most importantly learn.

Starting at the top of the Honda 1.5l “stack” is the Civic Si variant of this engine. It is listed as having a max boost pressure of 20.3 psi and producing 205 hp at 5700 rpm and 192 lb-ft of torque from 2100 through 5000 rpm. Honda lists this engine as having a 10.3:1 compression ratio and “recommending” premium unleaded fuel.

This engine seems very similar to the CRV engine except for the fact that max boost on the CRV is 18.5 psi. This engine makes a little more power and torque at a little bit higher rpm’s. Looks to me like the CRV tuned for premium fuel. The non-Sport Civic engine seems to be the same engine with the max boost again lowered to 16.5 psi and running on regular fuel with a slightly higher compression ratio of 10.6:1. So basically a detuned CRV engine with the max boost decreased to 16.5 psi that runs on regular fuel.

The other variant is the Civic Sport which seems to be the Civic engine with the same 16.5 psi of boost but tuned for a bit more power (timing advance) using premium fuel.

It is interesting to note that in all Civics with the CVT transmission torque is limited to a maximum of 162 lb-ft. Honda has even gone so far as to have the Sport CVT make it’s 180 hp at 6000 rpm instead of 5500 like the non-Sport to keep the torque below 162 lb-ft.

Since the CRV and Accord CVT’s handle more torque I’m wondering if the CRV/Accord CVT is somehow different and more robust than the one in the Civic?

Also why does Honda go to the trouble to reduce the stroke of the Civic engine by 0.1mm compared to the Si, CRV, and Accord? They also gone to the trouble of changing the combustion chamber to increase the compression ratio to 10.6:1. Why? Slightly less lag? Making the most of the regular fuel since boost pressure was lowered? Why not simply increase the boost a bit and keep the engine the same as the CRV to save on tooling costs?

Finally we have the Accord version of this engine. This engine seems to be the Si engine with VTEC and tuned to run on regular fuel. Looks like a gem to me. 192 hp at 5500 rpm and the same torque as the Si but starting at a lower 1600 rpm instead of 2100 rpm.

It seems to me like Honda could have saved themselves a lot of hassle by making the 1.5L “stack” look like this.

Civic Si – Add VTEC, lower compression ratio to 9.8:1, increase boost to 23 psi. This would basically be a smaller version of the Type R engine and would make about 230hp and 221 lb-ft of torque.

CRV – Keep as it.

Civic – CRV engine slightly detuned to about 175hp.

Civic Sport – Use the Accord engine.

This way Honda would have simplified the engine line up, kept all of the Civics except the Si on regular fuel, and maintained a nice hp spread from Civic to Sport to Si of 175hp to 192hp to 230hp. None of the engine would have overshadowed the one above or below it and the Si owners would have gotten a hot hatch right off the showroom floor while still leaving tuning headroom on the table.
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Lunarsilver17

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Where did you get the chart from, is that for U.S. models? I have an 17 Si , and it was not advertised to have VTEC when i bought it in June.
 

jeb

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VTEC since the R18 motor has been used for fuel economy, kinda like reverse VTEC to eliminate pumping losses and return better fuel economy. I believe this is why Honda put it on the Accord... why they didn’t put it on the CRV, yeah could be cost cutting.

Also as the other poster said, no VTEC for the Si, just double checked Honda’s site.
 
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CivicXVII

CivicXVII

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Where did you get the chart from, is that for U.S. models? I have an 17 Si , and it was not advertised to have VTEC when i bought it in June.
I created the chart using data from the Honda US website.

And yes, NO VTEC on the Si. Don't know how I messed that up!

That explains why the Accord makes more torque at lower rpms.
 

dc2turbo

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The Civic CVT can handle 192tq or even 220 WTQ

As for why accord has more tq at lower rpm. It could be a few reason. They may have the ecu set up to spool up at much lower rpms than the civics, different cams or different turbo.
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