So while driving I noticed that when I drive with ECT power on my mileage is lower than if I drive with it off according to the "Current MPG" display in the dash.

I have the ISF steering ecu so I have a little bit more features when I turn on the ECT power compared to a stock IS350. But I know that if I turn on ECT power then my shift points are a little bit more aggressive. The car will downshift while braking semi hard and the car will hold the lower gears a little bit longer for the best acceleration. Also the throttle response is a little bit better than with it off, although it is still not immediate. As far as I am aware this is all ECT power does on a stock IS350.

So we all know driving with or without ECT power we still have the same hp. There's no increase hp if you turn it on. But why does the MPG go down? In the video you could see me turning on and off the ECT while trying my best to stay at a constant speed and RPM and also, while I dont show it in the video, the highway was flat.


I am thinking maybe the better throttle response since I am putting the same pressure on the gas pedal the whole time while turning on and off ECT power. I dont really know how to explain it but it makes sense in my head on how that could be a possibility. To try to explain it as best as I can... the amount of pressure on the gas pedal with ECT power on needed to keep the car moving is less than the amount of pressure on the gas pedal needed if you have ECT power off. So if you keep the same pressure constant on the gas pedal while switching between both modes than you are technically putting more throttle when you turn on ECT power. However that doesn't explain the fact that the RPMs doesn't go up or the vehicle’s speed doesn’t increase.

My only assumption could be that the car does more than make the shifts more aggressive and increase throttle response. Possibly pulls more air from the intake which then consumes more gas which then worsens the MPG. But if it does that, shouldn’t it be making more power?


PS: While driving on my street after work in the middle of the night I notice that if I turn off ECT power my exhaust gets slightly quieter than if I drive down the street at the same speed and same RPMs but with ECT power on. It kind of reminds me like an exhaust valve control whenever I flip the switch while cruising although I know there’s no valve control in this car, its just to give an idea of what I am talking about.

 

https://www.clublexus.com/forums/is-...wr-button.html

 

As you mentioned, throttle response is more aggressive, but most likely holding the revs longer is the major cause for MPG's to go down. When I was driving a manual last year, MPG's were better if I shifted at 2500 as compared to 3500 RPM. The longer I held my rev's with the accelerator pushed down, the lower my MPG's. The more aggressive throttle response may also be contributing as well, as more fuel is being sent at take off than when in normal mode

 

Oh so I am not the only one who has noticed the decrease in MPG. But they were talking more as in daily driving theres a decrease in MPG due to the aggressive downshifts and it holding gears longer than normal. What I am trying to refer to is that the MPG magically goes lower with ECT power even if i stay in the same gear, same speed, and same rpm.

 

That may be to it being switched into a more aggressive tune. It's probably sending more fuel to the injectors, same speed/gear. When I had a 2018 Si, I had a tune called Two Step Performance Stage 1 tune which had 3 different maps. Maps 2 and 3 MPG's went slightly down even driving same speeds and gears. On commutes and long trips I stuck to map 1, and when I wanted to do some more aggressive driving I put it in Map 2, and mostly tried to avoid Map 3 because the stock clutch would start slipping if you got to aggressive, especially in 5th and 6th gears due to high boost

 

But if its sending more fuel then shouldn’t it be making more power? But I doubt it since the 2IS has been out for over 14 years at this point it would be known if ECT power actually makes more hp. If its not then whats the point of wasting more fuel? Thats what I am trying to understand if theres more things to it than what is known.

Speaking of a modded civic, last night I went against a 10th gen civic si coupe. He said he was almost fbo just needs an intercooler. It was actually a pretty close race in rolls. From the dig it was not close. I didn’t ask how much hp he was making however. But I was surprised how much he keep up doing like 30 and 40 rolls

 

That's actually a good point. I doubt its making significantly more power, although it may be pushing more "available" power to the low end. My thoughts: when in normal mode, it's in a more conserving mode, pushing out slightly less power to the wheels (unless you floor it) and shifting sooner. That's the only way I can explain it.

As far as the 10th gen Si, they are definitely not slow. Stock they make about 205 HP to the crank (187 WHP) and tuned they can make from 237 WHP with a minor tune (no FBO) all the way to 400 whp if safely tuned (a Company called MAPerformance pushed it 500 WHP). I knew guys that were pushing between 270 to 300 WHP with fbo, bigger turbo and Flex fuel (e40). Off the line they are not that fast because with FWD you have to push the power back into the RPM range due to torque steer and or tire life. Also fuel cutoff comes fast in 1st and 2nd gears, but once you hit about 3rd they are fast, 30 to 80 rolls they can keep up with a lot higher end cars. They are also very light, which gives them an advantage. But it does come at a price, I know a few people who threw rods trying to push to much power too soon without building out their engine. See this thread: https://www.civicx.com/forum/threads...jection.36470/

It's a long thread, but actually quite a journey he made!

 

Log some data and it should show the results.
capture:
Calculated load.
STFT and LTFT
Ignition advance.
And to compare apples to apples, you grab the Transmission Turbin Input Speed and Transmission Output speed, then you know what gear it's in.

Here is some of it as an example...

 

There is no difference in power between the modes. The differences are just in throttle control and transmission behavior.

 

Going back to the video you posted, I noticed a slight sound difference when going into ECT pwr mode. I re-listened to the video a few times, and even closed my eyes and listened. There is a barely perceptible yet distinct sound change. Probably the exhaust opening up a bit, that might also account for mpg's going down

 

At the end of the original post i made i did note that. It does get noticeably louder in ECT pwr compared to normal even though I am going the same rpm and same speed

 

To obtain throttle response I think you will find they did two things; altered the TB response, and mildly changed the timing which is what you hear in the exhaust.

I'll see if data shows that on the way home tonight.

 

holding the lower gears for longer and changing the throttle response is what decreases fuel economy, same reason the corvettes had a lockout to force you to shift from 1 to 4th at low RPM to get better fuel economy. That's really all there is to it, and watching the fuel economy gauge on a flat stretch isn't accurate enough to see a difference.

similarly if you floored it at each stoplight and let off as soon as you got to the speed limit, your fuel economy would also go to crap.

 

Freeway testing indicates the throttle MAP in ECT mode has a quicker opening rate AND is opening the TB further at some of the same physical pedal positions, hence the change in tone for OP.

I

 

It definitely opens the throttle more. This morning I drove it to work in ECT mode (all road, no highway) and there is no hesitation, and you can feel that even lightly touching the accelerator opens the throttle much more. I put the switch back on normal, and you feel the slight hesitation taking off when going light. Of course in normal the gears upshift quickly to keep you as fuel efficient as possible. This is all from a butt dyno perspective, but I have been driving long enough (since 15, I'm now 52 years old) to know that there is more throttle being applied at lower pressure when ECT is engaged. Thus more fuel being consumed. Case closed