Tips to find sweet spot

[xavi]

Hi there!
I have a 2007 1.8 i-vtec Civic that comes with some eco features such as eco cam phase, pumping losses reduction with drive by wire system, etc...
You can see the full explanation here:

https://www.youtube.com/watch?v=Px0_6-Btx3Y

This means that with this engine the "low rpm high gear" rule can be worst then "medium rpm low gear" in terms of delivering better mpg...

So, I'm decided to do a test to figure out the best rpm/speed/gear that delivers the best mpg. (aka sweet spot) and in the process I can find out the sweet spot for low speeds (secondary roads), and for highway speeds.
My car is a 6 speed manual, it has cruise control, and I have a scangauge II.

My idea is to get a straight flat or slightly uphill road big enough to gain some speed and slow down safely (still thinking of one...) I supposed when uphill the sweetspot will still apply but with more LOD?
Then I would set the cruise control in the desirable speed and let it stable and register (film or photo) the scangauge values to check out later.
Examples:
4 gear - 40 km/h - xxxx rpms - xx mpg
4 gear - 50 km/h - xxxx rpms - xx mpg
4 gear - 60 km/h - xxxx rpms - xx mpg
5 gear - 50 km/h - xxxx rpms - xx mpg
5 gear - 60 km/h - xxxx rpms - xx mpg
5 gear - 70 km/h - xxxx rpms - xx mpg
5 gear - 80 km/h - xxxx rpms - xx mpg
6 gear - 60 km/h - xxxx rpms - xx mpg
6 gear - 70 km/h - xxxx rpms - xx mpg
6 gear - 80 km/h - xxxx rpms - xx mpg
6 gear - 90 km/h - xxxx rpms - xx mpg
6 gear - 100 km/h - xxxx rpms - xx mpg

After that I take the best 2 of each gear and do the middle speed between them and try to get the best of each gear...
Don't know if this is the best way?!
Also don't know what to register in the Scangauge: MPG, HP, RPM, LOD or TPS?
Any advice please tell me! Thank you!

[86azms3]

Low rpm which would be the highest gear is best when it comes to light load driving.

Now I say light load...how is load calculated. Most modern cars with a MAF sensor calculate load based off of a couple variables like RPM and mass flow. More air in a cylinder, the higher the load. At higher loads and RPM's as well, since it's a 2D table, the ECU will enrich the fuel ratio to protect the engine from detonation.

So really it's about staying light load that keeps the ECU burning at stoich or lean burn if possible.


When accelerating you have to manage keeping light enough load to prevent enrichment, and also not making too many revolutions of the engine (friction). Also you have to take into account the VE (volumetric efficiency) which is not a constant across the entire rpm band.

A lot of variables...just try to drive in the lowest gear without your car getting pissed off at you...ie lugging.

[86azms3]

And if you really want to be good you could probably somehow look at injector duty cycle multiplied by RPM and maybe integrate over time if you had the ability to log and that would give a sense of how much fuel is being used.

[Daox]

You could just look at all the info Darin has been collecting with his 2007 Civic. His is a 5 speed, but I'm sure you can glean a lot off of the stuff hes done.

http://ecomodder.com/forum/showthrea...7-a-30111.html

http://ecomodder.com/forum/showthrea...1-a-29429.html

[xavi]

I have watch Darin's info, I also post there...
But Darin's Civic is a sedan (heavier makes more coast, drag coef is diferent), mine is the european hatch model, Darin has 5 speed, mine has 6 MT (diferente rpm/speed relation).
Engine wise is the same I guess.
For me, my dificulty in getting the best numbers is that it has 2 behaviours: on eco-cam, out of eco-cam, and the values change too... With eco-cam engaged it opens the throttle butterfly and it lets the intake valves open longer so it can reduce pumping losses...
I have realised, that in "eco-cam mode" is not always the best at low revs, but much better in midd revs...
I enter the "eco-cam mode" with less then 20-25 LOD in low rpms (<1800rpms), but in high rpms (>2500rpms) I can enter "eco-cam with less then 35 LOD... So it doesn't enter eco cam at a steady LOD. It changes with rpm change...
In conclusion, for me that in rare ocasions use highways, and my average speed is only 20 mph, I can enter eco-cam very easily if I pull 3 or 4th gear to 2500 rpms and stay about there... If I try to keep the rpms lower than that it's very dificult to enter eco-cam mode...
Mainly my dificult in finding the sweet spot is about it: high rpm with eco-cam vs low rpm without eco-cam (both with low load conditions).
Also discovered watching the open/closed loop behaviour that it only enters enrichment when full throttle pedal is apllied. If I have the throttle pedal 80-90% down, it doesn't go rich, but the SG is already showing 99 TPS, and it keeps 99 all the way down! I have calibrated the TPS with the open/closed loop, guess that this is normal to show 99 TPS without go rich?
This means that when acellarating even with 99 TPS but not all the way down it doesn't go rich, so maby in this engine i should pull off fast to cruise speed, instead of be very gentle with LOD when pulling?

Thnak you guys for your tips.

[xavi]

Originally Posted by 86azms3

And if you really want to be good you could probably somehow look at injector duty cycle multiplied by RPM and maybe integrate over time if you had the ability to log and that would give a sense of how much fuel is being used.

Unfortunately my SG doesn't have the log feature...
I think there is some xgauge to injectors? I think I tried that but didn't work if I'm remember it right...

My idea was to register the mpg at a fix point of the road, and then make it again with different rpm/gears and register it again and again, till I find the best speed/gear that returns the best mpg under 45-50 mph.

[rmay635703]

Originally Posted by xavi

Unfortunately my SG doesn't have the log feature...
I think there is some xgauge to injectors? I think I tried that but didn't work if I'm remember it right...

My idea was to register the mpg at a fix point of the road, and then make it again with different rpm/gears and register it again and again, till I find the best speed/gear that returns the best mpg under 45-50 mph.

Off topic but I did attempt driving the same 1 mile stretch of the same road from a fresh start in different ways to optimize my trip into work.
AKA the fuel econonomy average for the stretch was zero'd and thus was accurate.
(seemed as if I got a "good" start to the trip the rest was golden)

Ah well.

[xavi]

it happens to me too, I get off my garage and enter the main road, that has a red light that only changes red when a car comes at ilegal speed.
But it has to happen both ways so I may enter my lane...
So sometimes I don't even stop, (when by miracle doesn't come any car), sometimes I have to wait for a racer to change to red light and I can enter my lane... Can't turn off the engine, because I have to be fast when a chance appears...

When I lose some time getting in the road I usually end up with 6,x lt/100 km when arriving at work.
If I loose only some seconds, I end up with 5,x lt/100 km.
It´s a 5 mile comute, then very hard to make better...