i-VTEC in the 8th Gen Honda Civic

[fanamingo]

What is i-VTEC?

i-VTEC is an operating mode in 2006+ Civic engines that reduces pumping losses during some low engine load conditions (like steady cruising). Reduced pumping losses improves fuel efficiency. There are other variations on i-VTEC, but this post only covers my experience with the R18 engine in the 2006+ Civic.

Technical Overview of Honda's new R18 i-VTEC Implementation

Honda Worldwide | New 1.8l i-VTEC Engine

Why should I care?

It can improve your fuel economy! Gas engines are notoriously inefficient. Ideally, you want the engine running at peak efficiency or not at all. One of the more advanced hypermiling techniques is to alternate between these two states. Also known as pulse and glide, this maximizes your fuel economy. i-VTEC essentially adds a second efficiency peak that you can use. If driving conditions limit use of traditional P&G, try Pp&G (Pulse, pulse, and Glide). The second pulse is a weaker pulse with i-VTEC engaged. It's probably not as efficient as P&G in most situations, but it can help minimize your impact on surrounding traffic since your speed won't vary as quickly with the weaker pulse.

When is it active?

• The engine must be warm: 60C (140F) or higher
• Engine speed must be 1,000-3,500 rpm
• Low engine load such as is used in cruising conditions

How can I monitor it?

uabcar has figured out a way to splice an LED into the car's wiring so that it lights up when i-VTEC is active.

uabcar's DIY on 8thcivic.com

Alternatively, you can monitor i-VTEC with a ScanGaugeII. Unfortunately, you have to compare two different gauges to figure out i-VTEC: LOD and any of TPS, MAP, or IGN. Each of TPS, MAP, and IGN makes a noticeable jump when i-VTEC engages and disengages. Watch the following video to see what I mean. Sorry for the poor quality.

[KJSatz]

Hey thanks for the post. I have a SG-I in my 08 LX MT, and I'd like more information about how to tell if I'm in i-VTEC or not. I usually monitor LOD and IGN as well as MPG and something random like VLT or GPH. Could you describe in greater detail how you made the distinctions in the video and what rules to go by to use the SG to determine if I'm in i-VTEC? Thanks!

[fanamingo]

Sure. Sorry I didn't include enough detail. At the beginning of the video, LOD = 41 and MAP = 8.3. I know that i-VTEC is active at this point through past experience. As I increase pressure on the gas pedal, LOD increases up to 73 as MAP increases to 13.3. At this point LOD stays virtually the same at 72, but MAP suddenly drops down to 10.4. This is where i-VTEC deactivated.

i-VTEC reduces pumping losses. Higher MAP corresponds to reduced pumping losses. You can thus use MAP to monitor i-VTEC.

In the video, LOD continues to increase to 89, at which point MAP = 12.3. I then start backing off the accelerator and LOD and MAP both drop. They both decrease consistently to LOD = 59 MAP = 9.1. Between this point and the next SG update, i-VTEC reactivates. LOD continues to drop just a bit to 55, but MAP reverses its downward trend and jumps back up to 11.0. i-VTEC is active and again reducing pumping losses.

With practice, you get a feel for what the gauges should display if i-VTEC is active. If LOD = 60 and MAP = 12.0, I know i-VTEC is active. If LOD = 60 and MAP = 9.5, I know I need to let off the gas a bit to reactivate i-VTEC.

Similar trends can be seen with TPS and IGN since both these parameters are affected by i-VTEC activation.

Hopefully this makes more sense?

[psyshack]

As a past R-18 owner I spent 1.5 years trying to figure the low load 1.5L i-Vtec out.

Over all,, low load is what it's all about at steady state. Speed has no bearing on it at all, or gear for that matter. It's all in the rpm range and load. I could feel when my car went into it. There was a very very slight bump. The end result was mpg would shoot way up on the SG. The load range seemed to be a very narrow window indeed. Sort of like SAHM in a HCHII.

It also seemed easier to deal with with it in the MT cars like mine was versues the AT cars. The R-18 is one hell of a motor and I hope Honda use's it in the up coming CR-Z!

[uabcar]

Hey all.

I agree, i-vtec is very cool, If you pay attn to it, you can really impact your FE around town. It will engage below 25mpg if you're easy. Unless you're driving like a madman on the highway, it's on most all the time- especially if you are going fast enough that the LOD does not spike on moderate and progressive inclines. I find that at slower speeds (45-50mpg) the motor is not generating enough power for i-vtec to stay engaged if the road ramps up much at all. carrying a bit more speed into these inclines keeps the rpms up a bit while also keeping i-vtec engaged.

Psyshack is right, a very slight bump can be felt when it engages- but you'll only notice it if you're light and steady on the gas. I think what's happening is that when it engages and you're holding the pedal steady, your effectively pushing the accelerator- but in this case it's the same fuel flow to a smaller motor vs more fuel to the same size motor.

I really find the signal LED to be very useful- I've got a relay in the circuit so there is a light click when it goes on/off. I subconsciously listen for that click every time I'm behind the wheel.

[phlack]

Thanks for the post on this, Fanamingo. I was hoping someone would eventually describe this a little better.

I definitely have to figure this out.
Unfortunately, the video (which I guess is hosted on youtube) is blocked at work, so I have to remember to watch it at home.

So I have to have MAP and LOD up? And watch for when MAP jumps up when LOD remains constant (or going down)? That's when i-VTEC is engaged, and thus, MPG should spike up as well?

I'm running out of gauges! I need the loop gauge up, since that's required for the SGII to detect DFCO . I of course want the MPG up. Which means I'll have to lose TPS. And I don't wanna spend another $160 on a second SGII!

Still trying to figure out what LOD actually means.

-Mike

[uabcar]

[quote=phlack;220139]

I'm running out of gauges! I need the loop gauge up, since that's required for the SGII to detect DFCO /QUOTE]

Hey- I just ready this- I'm hoping it will help my prob. Several months ago there was a thread about SGII not reflecting DFCO on civic's. I read through that but there never seemed to be a conclusive follow up. I posed a couple follow-up Q's but got no response.

I thought someone suggested that you needed TPS or IGN up- but that does not seem to work for me. I have not tried Loop (assume this is the open/closed loop option). It's very odd, everything worked fine for some time- then is would intermittently- now IMPG never reflects DFCO.

I've got a 2nd SG now so it won't be a huge issue for me to display this.

[fanamingo]

I've had the same problem in the past with DFCO. Keeping the LP gauge up seemed to fix the problem. I could also temporarily fix the problem by unplugging the SG, plugging it back in, and then resetting it. A pain, but I only had to do it about once every other tank of gas. I recently got a new SG, which is version 3.16. I haven't had this problem again, but since the problem is intermittent, it's still too early to tell for sure.

Over the winter I also had trouble with the car itself deciding not to use DFCO. I think this is because of my habit of switching to neutral. The car's ECU decided I didn't like DFCO, so it disabled it. I think this is also temperature related because DFCO has returned as the weather has warmed up. Or perhaps my transitions from D to N and back are smoother?

LOD = engine load. It's a value from 0 to 99 that represents how much power the engine is putting out as a percentage of the total possible for a given rpm. A value of 0 means the engine is off. A value of 99 means the engine can't give you any more power without increasing rpm. All other values fall some where in between those two extremes. Make more sense? I use the LOD gauge the same way others use TPS. LOD gives better resolution (20-99 typical) instead of 13-25 for my typical TPS values.

Also, you can see i-VTEC by comparing LOD to TPS (instead of LOD to MAP). I find it easier to see the transition with MAP, but if you're used to TPS, that may work better for you. Have a look at the video when you get a chance, and let me know if I need to explain better.

[phlack]

Originally Posted by fanamingo

I use the LOD gauge the same way others use TPS. LOD gives better resolution (20-99 typical) instead of 13-25 for my typical TPS values.

I'm beginning to see why LOD is more helpful than TPS. Although I'm not using it the same way you are, it's helping me out more. I could probably get rid of TPS at this point (though I don't know what I'd replace it with).

Lately, I've been noticing that if I'm in 5th gear, my FE is best at speeds around 40mph, +/- a couple mph. Definitely if I stay below 50mph. I've noticed that I can sustain, say 43mph with a LOD setting between 42 and 52, or thereabouts. Assuming a warm engine, of course.

If I have LOD at 50 or so, my FE is in the mid 40's. If I can slightly raise my foot to lower that LOD down to 42 or so, my FE jumps into the very low 60mpg range, and I'm not slowing down. I'm assuming here that I'm in i-VTEC at this point. As long as I can keep that VERY steady foot (with it cramping up and all that), I'll stay around 60mpg.

So when I accelerate, I now aim for that low-mid 40's mph range (which is most of my commuting speed) and then try to jockey the accelerator to that level. I just wish there was some trick to keep it there. There's something with the accelerator in that I can raise my foot, and it will jump back up (LOD and TPS) temporarily until I keep raising it. Almost like there's something wrong with sensing where the throttle is. It isn't too bad, but gets annoying when I'm trying to really get it where I want it.

Doing this has raised my average FE a notch. Still hard to tell how much because my trips are still short trips, and the longer runs cramp my foot up, but I'm still trying!

-Mike

[KJSatz]

Thanks in no small part to the SG-I I recently got, I beat 50 mpg (in fact 52 mpg) in my LX MT! I'll just be upfront about the "repost" and quote myself from my post on another forum. w00t!

Originally Posted by KJSatz

I remember like ten months ago posting a thread about how pumped I was for getting over 40 mpg. Well I have beaten that down hard with a record that will probably stand for a while, as I don't think I can handle the prerequisites too often .

I drove 518.0 miles and used 9.888 gallons of E10, coming out to 52.4 mpg!

My car just crossed over 10000 miles during this trip. The only mods are the old clunker SG-I and tire pressure up to sidewall.

I did it by having a target speed of 50 mph (I often used cruise control on flat and semiflat terrain at the number) with no AC or fan except when I got struck by a red light and was engine braking to an inevitable stop .

There was a 200 mile round trip on highway that was pretty flat, so minimal EOC was employed, and some N coasting, mostly when I new a stop sign was coming up later. The other 300 miles was a one way journey I did today which had a lot of EOC, about 25 miles. My SG-I doesn't have hybrid mode, so when I shut the engine off, it reads some crazy mpg like 2000, but it doesn't log the miles in the Current or Today trips. Thus I could subtract the (otherwise accurate) Today miles from my odometer reading to see how many miles were missing. My engine does about .2 gph when idling, and if we assume 50 mph, 25 miles is 30 minutes (woah!), meaning it saved about .1 gal. So I would likely have exceeded 50 mpg even without EOC, according to this calculation.

This was honestly pretty rough, and I think for the 300 mile return trip I need to take Monday, I will use AC and have a target speed of 55 or 60 mph...maybe....

But I am very proud of this accomplishment and wanted to share it with you!