I understand that, but I'm referring to tiny changes that you can't exactly see in front of you. I had specified very slight declines as an example, typically just imperfections in the road -- not blemishes but just portions where it's not perfectly level. Even a regular driver will likely just keep their foot in the same position going over that since you don't really notice it. You are correct, the cruise control is reactive, but once it detects that slight decline it immediately lets off the throttle.

I'm not sure if I'm describing it correctly (or even if I'm totally correct since I'm not an engineer or anything), but I'm just basing it on my experience and observations when driving a car with a display showing the mpg of that exact moment. My girlfriend's car has it, and I've driven her car on the same trips (down a certain freeway), and I can see the differences and the changes in the mpg, even on what is more or less a level highway. On cruise control, it has more moments where it spikes to higher levels, while when controlling it manually and letting off when appropriate also allows the mpg to spike but it happens less frequently.

Obviously in the long run, those slightly more frequent spikes don't really amount to much of an increase in overall mpg, but it's just an observation.

 

No it's cool... I get what you're saying. But typically every time there's a slight decline, there's a slight incline shortly after. So when it lets off the gas to slow down while going over that decline, it will have to step on it slightly to go up the incline.

I mean... I suppose cruise control would be better in a theoretical environment... like North Dakota or something? And for 95% of the people, you'll get better fuel economy using it simply because humans can make errors, but if hypermiling is your game, then cruise control is your enemy.

 

how about looking at alignment too? 0 toe, little camber, etc. tires also play a role

 

shafting at 2000rpm is the best option, no air-con, all windows up

 

I prefer shifting at 2k rpm, but whatever floats your boat I suppose.

 

Not necessarily if im in 5th gear, and im trying to pass someone on freeway around 3k, with not even 20% throttle applied barely hitting 5 psi, my car is still close to stoich reading on my WB. technically at 5 psi theres really not much extra fuel used. Yes vacuum does work, but me personally I think part of the reason why my red has lasted so long, is driving like that on the highway, if i take it to 5 psi, ill take it to 10psi to blow off the air in the piping so that way the charged air doesnt try to revert back to the turbo when the throttle plate is almost closed.

 

Technically your DV is in need of adjustment if it doens't open at 5psi.

 

Even when my gauge reads right around zero or barely over it will blow off some just cause the gauge reading is coming from the intake and there is still a minimal amount of pressure in the piping before the boost pressure surpasses the engine vacuum and u open the throttle body enough and pressurize the intake manifold.

 

well see raptord it opens up slightly its not stiff to the point of not opening, i do slightly hear it at 5 psi. i like to run my bov spring a bit stiffer, so that way it holds 26psi without an issue, and actually even with my greddy rs a bit stiff, I very seldom get the rpms trying to cut out when coming up to a stop and idle.

 

more throttle + staying at stoich means more fuel is used

 

I was able to get around 20mpg with my setup. But that was keeping it at 60-70 and shifting at around 3500. At around 75 and up afr is around 11-12:1. Think it's time for a retune.

 

There is so much "WRONG" in this thread its gonig to confuse ppl.

DO NOT confuse manifold pressure to airflow, they are completely different. Only because you get -10~0psi gauge pressure on your turbocharged car DOES NOT mean on a N/A 2.0l @WOT is the same airflow/fuel economy. That is COMPLETELY FALSE.

Generically X air + Y fuel = Z hp... reducing the airflow yields good mpg results.. of course some engines are more efficient at making power with the same airflow....but this is a general explanation for simplicity

As Kyoo has stated... only because you have the same A/F ratio DOES NOT mean you have better or same fuel economy... its an overall RATIO, X/Y.... I could have 5X/5Y and it gives you the same ratio but uses 5x more fuel.

Fuel economy is mainly made up from these items
-overall frontal area
-vehicle height off the ground
-overall drag coeff. from areo (previous two has some relation)
-drivetrain losses
-bearing losses
-tire road load
-brake drag
-vehicle weight
-engine performance

Your 'engine' alone does not have a sweet spot... it makes the best fuel economy at idle, zero load.. pretty simple. The entire car it self usually has two sweet spots.
Has anyone ever seen fuel economy testing????
Normally its tested from 10mph - 80mph... and you'll see a fuel economy bump some where like 25-30mph and you'll see another somewhere around 50-60mph on just about every car

Keep your car in as high vac. as you possibly can, for as long as you can, with as minimal throttle changes with the minimal amount of throttle rate will yield you your best fuel economy.... so in other words, be very slow, very steady, very constant... good fuel economy .... and then read all the hypermiling tricks causes there are like 100....

 

actually how do u base that I have a wideband on the car. And if the reading is still at stoich with maybe 20-30% throttle, Going rich around 11-12 afr would mean its using more fuel. Stoich is 14.7, So please enlighten me on how your retarded post makes sense.

 

Opening the throttle more means more air gets in the engine. How do you think the mixture stays stoich if there`s more air going in? That's right ,the ECU adds fuel.

There's a retarded post here, but it's not Kyoo's...

 

Did you seriously not read that?