Welcome to the North American Subaru Impreza Owners Club Thursday February 27, 2020
Home Forums Images WikiNASIOC Products Store Modifications Upgrade Garage
NASIOC
Go Back   NASIOC > NASIOC General > Newbies & FAQs

Welcome to NASIOC - The world's largest online community for Subaru enthusiasts!
Welcome to the NASIOC.com Subaru forum.

You are currently viewing our forum as a guest, which gives you limited access to view most discussions and access our other features. By joining our community, free of charge, you will have access to post topics, communicate privately with other members (PM), respond to polls, upload content and access many other special features. Registration is free, fast and simple, so please join our community today!

If you have any problems with the registration process or your account login, please contact us.







* As an Amazon Associate I earn from qualifying purchases. 
* Registered users of the site do not see these ads. 
Reply
 
Thread Tools Display Modes
Old 02-13-2020, 03:57 PM   #1
defury
Scooby Newbie
 
Member#: 428480
Join Date: Aug 2015
Chapter/Region: W. Canada
Vehicle:
2003 Jdm Forester
Silver

Default EJ205, cruise at 2000rpm or 3000rpm

My jdm Forester has really weird gearing, it's much more aggressive than the wrx meaning cruising at the speed limit in 3rd puts me at around 2700-3000rpm, if i upshift to 4th I'm right at 2000rpm and i feel like this is hard on the rod bearings and other parts of the engine.

Thoughts?
* Registered users of the site do not see these ads.
defury is offline   Reply With Quote
Sponsored Links
* Registered users of the site do not see these ads.
Old 02-13-2020, 04:22 PM   #2
willthetech
Scooby Newbie
 
Member#: 498029
Join Date: Feb 2019
Location: Cleveland Ohio
Vehicle:
2019 WRX Premium
Pearl Blue

Default

This is the same for the FA20 in my wrx 2019, 3rd @40 MPH will put me between 2800RPM to 3000RPM, up shifting will drop me to about 2200 rpm or so. because LSPI in FA20s i make sure i stay in the 2800 to 3000 rpm range all the time, so i like it this way. My MPG suffers a bit...but less chances of knock.
willthetech is offline   Reply With Quote
Old 02-13-2020, 05:09 PM   #3
GlarryHoodDIT
Scooby Specialist
 
Member#: 460907
Join Date: Jan 2017
Chapter/Region: RMIC
Location: Colorado
Vehicle:
2016 WRX

Default

People should really consider actually understanding LSPI instead of driving everywhere at 3000rpms like a dope.

Cruising at 2000 rpms, just like in every other car created for consumers, is completely fine.

Low Speed, HIGH LOAD is the problem. Cruising isnt putting substantial load on your car at all.

Smh
GlarryHoodDIT is online now   Reply With Quote
Old 02-13-2020, 05:30 PM   #4
rtv900
Scooby Guru
 
Member#: 428511
Join Date: Aug 2015
Location: philadelphia
Vehicle:
2016 STI

Default

Quote:
Originally Posted by defury View Post
My jdm Forester has really weird gearing, it's much more aggressive than the wrx meaning cruising at the speed limit in 3rd puts me at around 2700-3000rpm, if i upshift to 4th I'm right at 2000rpm and i feel like this is hard on the rod bearings and other parts of the engine.

Thoughts?
if I'm putting along behind some geeser on a flat road, super casual I'll cruise at 1800
I wish I had a dollar for every time I said this, but the 'lugging' topic is taken completely out of context and misinterpreted

2000 is not 'hard on your rod bearings' unless you stand on the gas pedal
rtv900 is offline   Reply With Quote
Old 02-13-2020, 05:31 PM   #5
car_freak85
Scooby Specialist
 
Member#: 13530
Join Date: Dec 2001
Chapter/Region: NWIC
Location: Cascadia
Vehicle:
EA63 , EA81T, EJ20G,
EJ205

Default

Your engine is *generally* most fuel efficient at or around the torque peak. If you drive around at whatever speed that puts you at in top gear, you will have the best mileage.

For example my old automotive design professor used to work at Chrysler. The Mk 2 Viper gets better mileage at 120 mph than it does at freeway speeds because the engine is operating closer to the BSFC peak at those higher speeds.
car_freak85 is offline   Reply With Quote
Old 02-14-2020, 07:50 AM   #6
rtv900
Scooby Guru
 
Member#: 428511
Join Date: Aug 2015
Location: philadelphia
Vehicle:
2016 STI

Default

Quote:
Originally Posted by car_freak85 View Post
Your engine is *generally* most fuel efficient at or around the torque peak.
I don't think this is really true at all, why would it be most efficient at the peak torque rpm?

In the STI that's probably 3500 or 4000 rpm's. That's ridiculous to say your getting best mileage at that level.
I've gotten 28 mpg in my STI sitting on the highway going 60 in 6th at probably 2000 rpm's
But I'd be better off downshifting into 5th to jump the engine up to 3000 or even 4th and rev 3600???
no way

And isn't a forester and NA motor? So peak torque is going to be in the 4-5000 rpm level.
rtv900 is offline   Reply With Quote
Old 02-14-2020, 10:00 AM   #7
SoapBox
Scooby Guru
 
Member#: 204578
Join Date: Mar 2009
Chapter/Region: MAIC
Location: Boston
Vehicle:
My wife said she'd
buy me a Lotus, AKA REX8

Default

Quote:
Originally Posted by car_freak85 View Post
The Mk 2 Viper gets better mileage at 120 mph than it does at freeway speeds because the engine is operating closer to the BSFC peak at those higher speeds.
I can't say I believe that. It takes so much more power to push a car to 120 vs. 65. Like double triple the power. It's not 2-300% more efficient.
SoapBox is offline   Reply With Quote
Old 02-14-2020, 10:05 AM   #8
rtv900
Scooby Guru
 
Member#: 428511
Join Date: Aug 2015
Location: philadelphia
Vehicle:
2016 STI

Default

Quote:
Originally Posted by SoapBox View Post
I can't say I believe that. It takes so much more power to push a car to 120 vs. 65. Like double triple the power. It's not 2-300% more efficient.
^correct

That claim is total insanity, basically defies all laws of physics.
The aerodynamic drag alone at 120 vs 60 is quadruple.
Hell, stick your arm out the window at 120 and it's going to feel like it will be ripped off.
If there was an instantaneous fuel economy read out on that it would show probably single digit mileage at 120 mph.
rtv900 is offline   Reply With Quote
Old 02-14-2020, 10:08 AM   #9
SoapBox
Scooby Guru
 
Member#: 204578
Join Date: Mar 2009
Chapter/Region: MAIC
Location: Boston
Vehicle:
My wife said she'd
buy me a Lotus, AKA REX8

Default

Yeah, if he actually told his students that, I know why he "used" to work at Chrysler.
SoapBox is offline   Reply With Quote
Old 02-14-2020, 03:10 PM   #10
car_freak85
Scooby Specialist
 
Member#: 13530
Join Date: Dec 2001
Chapter/Region: NWIC
Location: Cascadia
Vehicle:
EA63 , EA81T, EJ20G,
EJ205

Default

You can poo-poo all you want, doesn't matter a lick to me. If you understand BSFC then you'll know that there are specific RPMs where an ICE engine is more efficient. Mix throttle opening and forced induction into the equation and you have a VERY complex set of variables.

Found this on 2.5RS.com, please read:

Quote:
There seems to be a lot of foggy discussions about how to drive for optimum fuel consumption. Everyone seems to agree (and rightly so) that the most efficient (power delivered per fuel consumed) point for engines is at the peak torque. It is - but it's also important to keep in mind that manufacturers give only the torque / hp vs rpm at WOT. The problem is that for driving at 70mph you CANNOT operate at WOT because you will accelerate. For a constant speed, partial throttle opening is required...and this is where things get messy, as it's more difficult to find any info about engine efficiency @ partial throttle. Say hi to Brake Specific Fuel Consumption (BSFC) - which measures fuel consumption as a function of RPM and engine load. The first plot shows BSFC as a function f RPM for different throttle openings.



Three curves here, for WOT, 50%, 25%. There is a stunning difference on how larger the BSFC is for partial throttle - at some points, 2x as big as for WOT. Translation: you engine's overall efficiency, namely brake horsepower per fuel used, dropped by half. One intuitive cause for that is simply manifold vacuum. At WOT, you're getting all the air into the engine you can. At partial throttle under high vacuum, your cylinders have to fight that vacuum - a significant portion of the fuel is thus used just to overcome this resistance, leaving only a fraction to generate useful (brake)torque.

Now the next step: a full BSFC curve, this time for the EJ22 N/A Subaru engine. A different layout, as the vertical axis is now engine torque.




The numbers here depict values of BSFC contour plots, plotted as a function of engine torque (vertical) and RPM (horizontal). The top curve depicts peak engine torque - or the same torque plot generated from a dyno/spec sheet, corresponding to a WOT operation. Anything below that curve represents a partial torque output...or partial throttle operation (as opposed to the first graph, there is no indication on the actual % throttle opening).
Now, the observations: the bottom region of the graph represents low torque (or partial throttle) operation. Again, the BSFC values are horrendous meaning that if you run under high vacuum and partial throttle, you're getting an awfully bad fuel economy. Conversely, at WOT (high torque output), you're operating near the best efficiency point. Interestingly the best region for the EJ22 seems to be in between 1800-3500 rpm, almost at WOT. This allows to conclude that for acceleration purposes, the best fuel efficiency will occur - for this engine - shifting at 3500 and nearly WOT-ing at all times...

(continued…)
Turns out the 2.5RS.com link has broken images, so here's a link to the same content posted on thesamba.com.
car_freak85 is offline   Reply With Quote
Old 02-14-2020, 04:53 PM   #11
willthetech
Scooby Newbie
 
Member#: 498029
Join Date: Feb 2019
Location: Cleveland Ohio
Vehicle:
2019 WRX Premium
Pearl Blue

Default

Quote:
Originally Posted by GlarryHoodDIT View Post
People should really consider actually understanding LSPI instead of driving everywhere at 3000rpms like a dope.

Cruising at 2000 rpms, just like in every other car created for consumers, is completely fine.

Low Speed, HIGH LOAD is the problem. Cruising isnt putting substantial load on your car at all.

Smh
LOL!

OP… sorry this became more of a scientific lesson than an answer, it seems some become experts after googling for 10 minutes.

I can only give you my experience in a FA20. driving at anything lower than 2800rpm and then trying to accelerate to shift, it feels like the car is bugging down and somewhat damaging the car. Can I prove is happening of course not, but you can tell…it just doesn’t feel good…natural. In the other side of the coin, when I am going 2600 to 2800, shifting feels natural…correct…normal. Also asking around to people that own WRX, GTIs, etc…they all cruse higher than the so called “2000 rpm rule”.

I never red line my car, I never WOT in the highway at low rpm, always downshift…then go.

My 2 cents…hopefully this helps somehow.
willthetech is offline   Reply With Quote
Old 02-14-2020, 05:10 PM   #12
rtv900
Scooby Guru
 
Member#: 428511
Join Date: Aug 2015
Location: philadelphia
Vehicle:
2016 STI

Default

Quote:
Originally Posted by car_freak85 View Post
You can poo-poo all you want, doesn't matter a lick to me. If you understand BSFC then you'll know that there are specific RPMs where an ICE engine is more efficient.
^right dude, so now that you've researched it a bit you understand it a little better, and you've abandoned the blatantly false statements made initially.
For starters, you said ICE are most fuel efficient at peak torque, which is classic misunderstanding. Peak torque is where the ICE is at peak VOLUMETRIC efficiency, which has less than nothing to do with fuel efficiency. Volumetric efficiency makes the most power, and sure, the most per unit mass fuel. . .still nothing to do with getting good fuel economy.

And fine, efficiency dependent on rpm and throttle opening does make a difference, but TOTALLY impractical for a consumer vehicle. I mean seriously dude, you think a driver is going to read throttle opening data and compare that to where it would fall on a chart vs rpm and choose a gear based on that. For god's sake talk about totally out of context.

You also made a downright ludicrous comment about something getting better mileage at 120 vs 60??? Talk about insanity. Drag increases exponentially, after 45 mph drag is basically all you are using fuel to overcome if there is no incline. At 120 you are fighting so much drag your getting 5 mpg, so I don't think it's us whom are not understanding BSFC when you make a comment that far off the map.
Why do you think $400k supercars can barely top 200 mph? And 215mph is basically unheard of?
Because the designers couldn't make a gear ratio to get there?
No, because you need about 700 hp to get to 200mph and another 300 additional hp to go from 200 to 215.


Quote:
Originally Posted by willthetech View Post

I never red line my car, I never WOT in the highway at low rpm, always downshift…then go.

My 2 cents…hopefully this helps somehow.
I swear there is a thread somewhere that I said, "maybe when my car hits 100k somebody will finally believe me on this lugging nonsense being out of context"
Well I'm at 101K now and I go WOT in 6th every day uphill on a highway, and I cruise at 1500 rpm's in some cases, and my engine runs like new and now consumes maybe a half quart per 5000 miles.
Cruising at light throttle at 3000 rpm's for some fear of lugging is nonsense.
rtv900 is offline   Reply With Quote
Old 02-14-2020, 05:18 PM   #13
GlarryHoodDIT
Scooby Specialist
 
Member#: 460907
Join Date: Jan 2017
Chapter/Region: RMIC
Location: Colorado
Vehicle:
2016 WRX

Default

Quote:
Originally Posted by willthetech View Post
LOL!

OP… sorry this became more of a scientific lesson than an answer, it seems some become experts after googling for 10 minutes.

I can only give you my experience in a FA20. driving at anything lower than 2800rpm and then trying to accelerate to shift, it feels like the car is bugging down and somewhat damaging the car. Can I prove is happening of course not, but you can tell…it just doesn’t feel good…natural. In the other side of the coin, when I am going 2600 to 2800, shifting feels natural…correct…normal. Also asking around to people that own WRX, GTIs, etc…they all cruse higher than the so called “2000 rpm rule”.

I never red line my car, I never WOT in the highway at low rpm, always downshift…then go.

My 2 cents…hopefully this helps somehow.
This is a microcosm of your entire argument. "I cant prove it but I'm totally right." You dont even understand what LSPI is, and that was the entire basis for your original post. I've put almost 100k on my FA20 and have zero problems driving the car at low load. Zero mechanical issues. Your inability to smoothly drive a manual transmission is an indictment of YOU not the engine.
GlarryHoodDIT is online now   Reply With Quote
Old 02-14-2020, 05:45 PM   #14
Stanley
Scooby Guru
 
Member#: 7374
Join Date: Jun 2001
Location: North Bay, SFCA
Vehicle:
2007 Grandpamobile
BlingBlingBlue

Default

This is an interesting video related to this topic:

Stanley is offline   Reply With Quote
Old 02-14-2020, 05:45 PM   #15
samb
Scooby Specialist
 
Member#: 177235
Join Date: Apr 2008
Chapter/Region: NWIC
Vehicle:
2016 Focus RS
2002 WRX Wagon

Default

Is your foot halfway to the floor to maintain speed and the engine is growling at you? Downshift. Is your foot halfway to the floor and the engine is singing away? Upshift. Is your foot right where it should be and the engine is humming along? Leave it where it is.

I wouldn't worry too much about what specific RPM you're at. Level road or downhill you're going to be more efficient at a lower RPM and going uphill you're going to be more efficient at a higher RPM. Headwind, tailwind, water on the road, road surface, etc. All of it will affect your mileage and what RPM is most appropriate. Your engine will do fine with any combination you cruise at, but your wallet won't!
samb is offline   Reply With Quote
Old 02-14-2020, 06:29 PM   #16
car_freak85
Scooby Specialist
 
Member#: 13530
Join Date: Dec 2001
Chapter/Region: NWIC
Location: Cascadia
Vehicle:
EA63 , EA81T, EJ20G,
EJ205

Default

Quote:
Originally Posted by rtv900 View Post
^right dude.
Look, I respect you as a member of this forum. You've given out good advice to me over the years, but you are wrong in this case, plain and simple.

I work as a senior design engineer for an OEM. My old professor worked with Lamborghini (owned by Chrysler at the time) to redesign the V10 that eventually landed in the Viper. If you want to cut to the chase, I'll get someone from our engine design team to write you a white paper on this. Hell, I should have gone straight to our SAE database and looked for an already published study in the first place...

I DO understand air and road drag. I KNOW that volumetric efficiency and fuel efficiency are correlated, whether you subscribe to that or not. I lug the ever-loving crap out of my EJ205, but I also make 90psi of oil pressure at low RPMs.

I did NOT say this (better economy at 120 mph) applies to every vehicle on the road. I specifically mentioned a VERY slippery car (there's your drag) with a MASSIVE, inefficient engine and the ability to reach silly speeds. I didn't say this about a Forester XT.

Here's a fun brain buster: Our '99 Forester. Drove myself, the wife and another couple, their dog and all our gear down to central Oregon a mostly flat drive with one small mountain range to climb up and over. Drive in was at ~65 mph. We averaged ~27 mpg, mostly highway. On the return trip I purposely averaged ~80 mph and our mileage was above 30 mpg. Was it a scientific test? Absolutely not. But it proved my professor correct.

Keep it out of boost, drive as close to the torque peak as you can and hope Smokey doesn't notice you blasting by well above the limit. Or try the "Burn and kill" method, but that's a lot more involved to get better mileage and your passengers will probably get car sick or annoyed.
car_freak85 is offline   Reply With Quote
Old 02-14-2020, 08:21 PM   #17
defury
Scooby Newbie
 
Member#: 428480
Join Date: Aug 2015
Chapter/Region: W. Canada
Vehicle:
2003 Jdm Forester
Silver

Default

Unfortunately i have zero clue what peak torque is in a stock JDM EJ205T with AVCS. The engine sounds like it enjoys 2k rpm more but 3k rpm definately has more get up and go when i blip the accelerator
defury is offline   Reply With Quote
Old 02-15-2020, 10:36 AM   #18
Norm Peterson
Scooby Newbie
 
Member#: 498642
Join Date: Mar 2019
Chapter/Region: Tri-State
Location: our wrx IS the family sedan
Vehicle:
'19 WRX Limited 6M
'08 Mustang GT (the toy)

Default

Quote:
Originally Posted by car_freak85 View Post
Your engine is *generally* most fuel efficient at or around the torque peak.
On a BSFC basis, sure. But that's separate from the load on the engine during steady cruise conditions.


Quote:
If you drive around at whatever speed that puts you at in top gear, you will have the best mileage.
Better mileage than at the same mph in a lower gear, sure. Not the same thing, though.


Quote:
For example my old automotive design professor used to work at Chrysler. The Mk 2 Viper gets better mileage at 120 mph than it does at freeway speeds because the engine is operating closer to the BSFC peak at those higher speeds.
The power required at 120 mph is something like 6 times what you need at 65, provided that it's the same car and the aerodynamics haven't shifted due to aero lift or downforce. No way has the BSFC at peak torque rpm dropped off to less than 16% of what it is at half of peak torque rpm.

Your own chart shows 0.42 for 100% at something like 3400 rpm. The 25% curve at 1700 rpm reads about 1.05. That's 40%, not 16%.


Norm

Last edited by Norm Peterson; 02-15-2020 at 11:20 AM.
Norm Peterson is offline   Reply With Quote
Old 02-15-2020, 11:08 AM   #19
Norm Peterson
Scooby Newbie
 
Member#: 498642
Join Date: Mar 2019
Chapter/Region: Tri-State
Location: our wrx IS the family sedan
Vehicle:
'19 WRX Limited 6M
'08 Mustang GT (the toy)

Default

Quote:
Originally Posted by rtv900 View Post
I don't think this is really true at all, why would it be most efficient at the peak torque rpm?
It is most efficient there on the basis of HP developed per unit weight of fuel consumed (the units of BSFC are lbs of fuel used per HP per hour). That's strictly an engine output metric, not a MPG metric although there is a loose relationship between the two.

Basically, mpg is a balancing act between the BSFC curve, the amount of power required, and the amount of throttle required (think pumping losses).


Quote:
In the STI that's probably 3500 or 4000 rpm's. That's ridiculous to say your getting best mileage at that level.

If your car was geared such that it could only pull to peak torque rpm in top gear, your mpg at that particular speed probably would be optimized (I'm going to stipulate that the transmission gearing is most efficient in top gear for simplicity, even though that probably isn't the case).

That would not be the car's top speed, though, because you wouldn't have enough power in top gear to get past the peak torque rpm speed (the drag forces would be increasing faster than the HP curve was rising, she's all done there ain't no more). Think of this as an extreme example of what we're seeing when a car reaches its top speed in 5th rather than 6th . . . which is also being done for the slight mpg benefit (the gains from the reductions in both rpms and pumping losses helping more than the higher BSFC hurts).


Norm
Norm Peterson is offline   Reply With Quote
Old 02-15-2020, 11:34 AM   #20
Norm Peterson
Scooby Newbie
 
Member#: 498642
Join Date: Mar 2019
Chapter/Region: Tri-State
Location: our wrx IS the family sedan
Vehicle:
'19 WRX Limited 6M
'08 Mustang GT (the toy)

Default

Quote:
Originally Posted by defury View Post
My jdm Forester has really weird gearing, it's much more aggressive than the wrx meaning cruising at the speed limit in 3rd puts me at around 2700-3000rpm, if i upshift to 4th I'm right at 2000rpm and i feel like this is hard on the rod bearings and other parts of the engine.

Thoughts?
I've always driven in whatever gear would provide satisfactory response to tipping into the throttle just a little. What that is, is somewhat car-specific. For the WRX (and the LGT before it), that has been at just over 2000 rpm, I think primarily because of the turbochargers.

In an NA car like the Mustang, I tend to keep the rpms above maybe 1750 rpm. A little higher for the Maxima and the other V6-powered family cars we've owned (you do need to realize that all of these cars have been MT). In the car with a smallbore 4 with a fairly healthy cam that I had a long time ago, 2500 rpm or a bit more.


Norm
Norm Peterson is offline   Reply With Quote
Old 02-15-2020, 08:39 PM   #21
oichan
Scooby Specialist
 
Member#: 492327
Join Date: Oct 2018
Location: A garage in the Midwest
Vehicle:
19 WRX / 16 STI
17 Golf-R / 16 FiST

Default

In doubt, I'd just use the lower gear. 2700rpm cruising is fine.

If given a choice between cruising at 1800rpm vs 2700, I would take the 2700 on the WRX and STI.
oichan is offline   Reply With Quote
Old 02-16-2020, 03:05 AM   #22
defury
Scooby Newbie
 
Member#: 428480
Join Date: Aug 2015
Chapter/Region: W. Canada
Vehicle:
2003 Jdm Forester
Silver

Default

Quote:
Originally Posted by oichan View Post
In doubt, I'd just use the lower gear. 2700rpm cruising is fine.

If given a choice between cruising at 1800rpm vs 2700, I would take the 2700 on the WRX and STI.

Is there a particular reason you'd do 2700 over 1800
defury is offline   Reply With Quote
Old 02-16-2020, 09:21 AM   #23
Norm Peterson
Scooby Newbie
 
Member#: 498642
Join Date: Mar 2019
Chapter/Region: Tri-State
Location: our wrx IS the family sedan
Vehicle:
'19 WRX Limited 6M
'08 Mustang GT (the toy)

Default

Quote:
Originally Posted by oichan View Post
In doubt, I'd just use the lower gear. 2700rpm cruising is fine.

If given a choice between cruising at 1800rpm vs 2700, I would take the 2700 on the WRX and STI.
I think the only times you'd be looking at that choice would be when you're driving on a 25 mph neighborhood street or possibly in a school zone and trying to stay just under 25. Between any other consecutive gears, the spacing is tighter than 1.5 to 1 and your rpm choice would be between 2700 and 2000 or a bit more.

Only a couple of mph above 25 puts you at 2000 rpm in 3rd, which will hardly ever get you in trouble. On a cold morning, 2nd gear at closer to 2200 rpm (about 20 mph) would probably be the better overall choice for the first quarter mile or so.


Norm
Norm Peterson is offline   Reply With Quote
Old 02-16-2020, 02:35 PM   #24
samb
Scooby Specialist
 
Member#: 177235
Join Date: Apr 2008
Chapter/Region: NWIC
Vehicle:
2016 Focus RS
2002 WRX Wagon

Default

Quote:
Originally Posted by car_freak85 View Post
Here's a fun brain buster: Our '99 Forester. Drove myself, the wife and another couple, their dog and all our gear down to central Oregon a mostly flat drive with one small mountain range to climb up and over. Drive in was at ~65 mph. We averaged ~27 mpg, mostly highway. On the return trip I purposely averaged ~80 mph and our mileage was above 30 mpg. Was it a scientific test? Absolutely not. But it proved my professor correct.

Keep it out of boost, drive as close to the torque peak as you can and hope Smokey doesn't notice you blasting by well above the limit. Or try the "Burn and kill" method, but that's a lot more involved to get better mileage and your passengers will probably get car sick or annoyed.
Even a slight headwind vs tailwind explains your results. I see it every week during my commute. If the prevailing winds were from the south I would expect you to get much better mileage heading north, even at faster speeds. A meager 10mph wind would result in a relative velocity of 75mph for your trip down and 70mph for your return.

Last edited by samb; 02-16-2020 at 02:41 PM.
samb is offline   Reply With Quote
Old 02-16-2020, 07:26 PM   #25
blurred
Scooby Newbie
 
Member#: 47143
Join Date: Nov 2003
Location: Toronto
Default

Quote:
Originally Posted by car_freak85 View Post
You can poo-poo all you want, doesn't matter a lick to me. If you understand BSFC then you'll know that there are specific RPMs where an ICE engine is more efficient. Mix throttle opening and forced induction into the equation and you have a VERY complex set of variables.



Found this on 2.5RS.com, please read:







Turns out the 2.5RS.com link has broken images, so here's a link to the same content posted on thesamba.com.
You've completely mistaken engine efficiency and fuel efficiency and your responses are all pretty sad as a result.
blurred is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump

All times are GMT -4. The time now is 03:57 PM.


Powered by vBulletin® Version 3.7.0
Copyright ©2000 - 2020, Jelsoft Enterprises Ltd.
Powered by Searchlight © 2020 Axivo Inc.
Copyright ©1999 - 2019, North American Subaru Impreza Owners Club, Inc.

As an Amazon Associate I earn from qualifying purchases.