Higher revving = better gas mileage?

[smo0f]

all i know is that if you have cruise control, use it as much as possible, that's if you are concerned about gas mileage. i have a 6 cylinder and avg hwy mileage is 32 if i use cruise control.

 

[winty87]

I'm going to have HOOOOORIBLE gas mileage this tank, this girl I like just made out with one of my friends. Takin the anger out in my car.

 

[carter1551]

thats contrary to anything ive known but hey ill give it a shot. must be all that carbon buildup

 

[Kooldino]

redline it every shift... it's the only way.

I forsee this line in 4fast4urious.

 

[hex2bit]

Driving style doesn't seem to affect the car much. Babying it vs. reving it doesn't change mileage much for me. I typically rev between 4 to 5K before shifting. Sometimes near redline. The biggest thing I have found for mileage is the fuel. Where I live, we have ethonel and it really sucks. When I drive to other places, I always get better mileage on their fuel rather than the fuel from where I live.

I used to get about 30 mph mixed driving, but now it's around 25 mpg. When I go to another state, or some remote place, I will typically get mileage back towards 30 again using their fuel.

 

[Prodigy]

The clutch install is finished and I have to be gentle until its broke in. I hate shifting at 3000 - 3500 rpms. Its so boring.

Haha. tell me about it!
I have 200 miles to go on my exedy stage-1

 

[aMaff]

Haha. tell me about it!
I have 200 miles to go on my exedy stage-1

want to add a few more? Come pick up the struts / springs tomorrow...

 

[Prodigy]

want to add a few more? Come pick up the struts / springs tomorrow...

I completely forgot about those... though my friend has been bugging me about em.
What time works best?

I'll be putting new pads in, passenger motor mount insert, stereo and interior back in sooner or later in the day.

 

[aMaff]

I completely forgot about those... though my friend has been bugging me about em.
What time works best?

I'll be putting new pads in, passenger motor mount insert, stereo and interior back in sooner or later in the day.

Mid to late morning. I'm going to Luke / JAs place later on to work out some kinks in the Miata's suspension.


EDIT: PM sent. I'm goin to bed...

 

[NVP5White]

I run the snot out of my motor all.the.time. Maybe not redline s**** (4500-5500 is ave) but always *ALWAYS* WOT. My MPG has been consistantly 26. I've tracked my MPG for ~18 months (yeah, every mile, every fill-up) and my average is 26.72. I have seen a high of 34.58 and a low of 22.46. My average drops about 2-3mpg when the winter gas in the area hits.

The only other item that has a significant change in MPG is the length of time spent running on a cold motor. I think the VICS combined with other cold-engine ECU parameters makes fuel consumption skyrocket.

So, get the engine warm befor giving it WOT and don't make a lot of short trips. Otherwise, feel free to run the thing into the ground. It hasn't seemed to effect my MPG in a negative way...

 

[Matthew1785]

fourms are acting up and not letting me post a thread so im gonna try here

Soot in the Tail pipe?

Is it normal? its been bothering me a little. im assuming because we run so rich im going to see black soot inside the tail pipe just thought i would get another opinion

 

[clicknext]

I run the snot out of my motor all.the.time. Maybe not redline s**** (4500-5500 is ave) but always *ALWAYS* WOT. My MPG has been consistantly 26. I've tracked my MPG for ~18 months (yeah, every mile, every fill-up) and my average is 26.72. I have seen a high of 34.58 and a low of 22.46. My average drops about 2-3mpg when the winter gas in the area hits.

The only other item that has a significant change in MPG is the length of time spent running on a cold motor. I think the VICS combined with other cold-engine ECU parameters makes fuel consumption skyrocket.

So, get the engine warm befor giving it WOT and don't make a lot of short trips. Otherwise, feel free to run the thing into the ground. It hasn't seemed to effect my MPG in a negative way...

Wow, what kind of trips do you make and what is your route like? Highway or city? Whenever I see your name I think of another P5 owner I know who's called something like NVP5, but theirs stands for North Vancouver. =)

 

[njaremka]

fourms are acting up and not letting me post a thread so im gonna try here

Soot in the Tail pipe?

Is it normal? its been bothering me a little. im assuming because we run so rich im going to see black soot inside the tail pipe just thought i would get another opinion

normal, yes.

 

[newprot5fan]

well, that higher revving thing in my opinion, is not that accurate..my gas mileage PLUMMETTED when doing that.....and it was awful gas mileage to begin with...

 

[RatLabGuy]

Funny you guys bring this up....
When I first got my P5 in Oct, MPGs were about 29. since then declined, last few tanks averaged 26.5-27. Like others here, I track every fillup, every mile, verymaticulously.
Been bugging me, so been thinking about it a bit, and wondering about this average RPM issue. Last weekend I made a trip to Raleigh, 26.5 MPGs. Note, I typicaly rev fast, and shift around 4k, on highway cruise pushing 80, putting the RPMs at almost 4k.
This tank, specifically changed driving habits - rule: RPMs never above 3500. Drove more conservatively, shifted around 3k, 3.5 or so. Made the *same trip* to Raleigh again. Kept speed @ or < 75 to maintain RPMs < 3500.
Low and behold - 29.0 mpgs.

Now I know that 1 case does not prove the rule, multiple samples needed. But it matches the physics and logic. You are most efficient w/ gas when producing just over the energy needed. AKA, if need 100 hp, then anything over that is wasted energy (= gas). If the energy demand < energy available, efficentcy is bad, hard on motor. This is what happens at 1500 RPM.
(assuming no load), at 3000 RPM, you are using 2x as much gas as at 1500 rpm. But also going 2x the distance (assumiing same gear) so it balances. But you're also making more power (2x? don't know) at 3k. So when a laod is added, you are more efficient b/c the motor can match the "pull" needed to overcome the force to get that same speed. Once you exceed this balance point, say 4.5k, you are just wasting gas... although it is definitely more fun!

 

[NVP5White]

Now I know that 1 case does not prove the rule, multiple samples needed. But it matches the physics and logic. You are most efficient w/ gas when producing just over the energy needed...Once you exceed this balance point, say 4.5k, you are just wasting gas... although it is definitely more fun!

I heavily edited your post for space reasons...

You are hitting all around the right answer. Over 75mph (over 55mph, really) aerodynamic drag begins to remove the "gains" of going faster. In a vacuum, twice the RPMs + twice the MPH would equal the same efficiency, but since drag increases at the square of the speed, your gains decrease...at an increasing rate. For the Protege5 gearing, my mph drops significantly over 70-75mph.

As for efficiency, don't even try and work through it...internal cumbistion engines are most efficient at wide open throttle. Pumping losses at partial throttle openings remove any gains fromuseing less fuel. This is why gasoline engines run rich, with the Proteges running more rich then some.

As for what RPM to shift, typically, running WOT (most efficient) at lower RPM (below 4,000RPM) will get you up to cruising speed using the least amount of gas. BMW did extensive studies back in the 1970's which resulted in the X25e (for the greek letter 'eta' [REF - regression coefficinet]) models. They had 4,250 redlines, IIRC. They were tuned to peak power at or below that low redline. The idea being: drive at WOT to cruising speed while mechanically limiting the rpm to ensure good gas milage.

 

[P-Funk!]

EPA testing is done by 'quickly walking through the gears so you get to 5th sooner'. Study shows that just low revving it and dwelling in the lower gears isn't as efficient. Skip fourth gear when you can. Your best gas mileage occurs in 5th at ~50 MPH (less gas pedal). Driving faster (more revs) keeps your engine closer to peak efficiancy - but uses more gas (the whole reason for the discussion).

 

[clicknext]

EPA testing is done by 'quickly walking through the gears so you get to 5th sooner'. Study shows that just low revving it and dwelling in the lower gears isn't as efficient. Skip fourth gear when you can. Your best gas mileage occurs in 5th at ~50 MPH (less gas pedal). Driving faster (more revs) keeps your engine closer to peak efficiancy - but uses more gas (the whole reason for the discussion).

Peak efficiency? Do you mean peak power?

 

[NVP5White]

Peak efficiency? Do you mean peak power?

No, nearer to peak efficiency. IC engines are most efficient at wide open throttle (this is independant of RPM). It helps to think of an IC engine as an air pump. The more efficiently it can pump air in and pump exhaust out the more efficiently it will run. The throttle plate when only partially open blocks air and makes it more difficult to pump air.

Remember that efficiency is in terms of unit of output per unit of input. If wide open throttle results in going too fast, then you HAVE TO operate at a less efficient engine setting.

Diesel engines do not have this same issue. In fact, since diesel's can run all the way lean (no fuel when coasting) then their part throttle fuel delivery can more closely match the power that is required vs the amount of fuel required to keep compusiton temps down like in gasoline engines.

 

[P-Funk!]

^correct. But not to be confused with fuel flow rates - the ultimate 'get to the next gas station ' metric. There is no better way to save gas than to go easier on the gas pedal/min fuel flow for the speed you are traveling.

Summary:
Get to 5th quickly and then do the speed limit = best avg fuel economy.