TR Forums

End User wrote:

Upon further investigation I see that my normal 1st gear pulls result in 4.7 mpg. Spirited driving for the win!

The instantaneous measure on my car will read around 1.8 MPG if I remain at full throttle. Mixed driving on the track yields 5-6 MPG if I'm really hammering it.

I was down to 10.5 mpg but a 2 hour drive to MD upped it immensely to 14.0. 95% of my driving is in the city, so having a heavy 3 row SUV and a thirst 5.7 Hemi is a bad equation for getting good fuel economy. Luckily, I only have a 7 mile round trip daily drive to work every day, so even at those very low numbers, I only need to fill it up 2x a month.

Walkintarget wrote:

I was down to 10.5 mpg but a 2 hour drive to MD upped it immensely to 14.0. 95% of my driving is in the city, so having a heavy 3 row SUV and a thirst 5.7 Hemi is a bad equation for getting good fuel economy. Luckily, I only have a 7 mile round trip daily drive to work every day, so even at those very low numbers, I only need to fill it up 2x a month.

Hey, fellow Durango owner? Or Jeep Commander. Either way, the best I've done in my Hemi Durango is like 13.5L/100KM which is short of 18mpg. I doubt I get more than half of that during short commutes in the winter.

End User wrote:

Shobai wrote:

Yikes!

What are you paying for fuel? Our 98 octane is $1.61 per litre.

91 is $1.41 CDN

Ouch 91 octane can be had here for just over $1, I'm guessing 91 would be $1.10-1.15. I think we have some of the cheapest gas prices in Canada though.

$3.199/gallon, or $0.85/litre, for premium (93 AKI) this AM. The one downside of Subie turbos is the need for premium. In Canadian pesos that's $3.97/gallon or $1.05/litre.

captaintrav wrote:

Hey, fellow Durango owner? Or Jeep Commander. Either way, the best I've done in my Hemi Durango is like 13.5L/100KM which is short of 18mpg. I doubt I get more than half of that during short commutes in the winter.

'Rango it is ! 2012 Citadel. I got 18 on a trip to Philly this fall, and that was the best she has ever done in 1 year of ownership. But I did not buy it for MPG, I bought it to tow my trailer and ATVs once a month. It drives so nicely compared to a typical pickup, and offers so many niceties (Bluetooth, blindspot warning, crosstraffic warning, etc) that I can somewhat ignore an important aspect that many buyers value highly. And at least this time of the year, the heated seats and steering wheel are so welcome.

I get around 14L/100Km in my 2014 Fiat 500 Turbo because I rarely get a chance to open up the throttle on my commute unfortunately. Gas is around 1.14 Canadian per Liter here (for premium at least).

bthylafh wrote:

Chrispy_ wrote:

If you want to go faster, you want to go faster as quickly as possible.

Are you that guy who has to jackrabbit between stop signs?

He's obviously never driven in the snow.

Also, if I jam on the gas even on dry pavement, I could spin the wheels in my old Ford Ranger, because it was RWD and the back end was so light.

So gas pedals clearly are not binary.

derFunkenstein wrote:

So gas pedals clearly are not binary.

Yet they are often subject to id10t errors.

derFunkenstein wrote:

So gas pedals clearly are not binary.

Clearly engine mounts are supposed to be consumables.

In -35C weather terrible. Getting about 300km in town on 46L of regular. (probably contains a heavy dose of ethanol....sigh)

edit - with a 2006 Pontiac torrent, 3.4L V-6 FWD and winter tires.

In defense of semi-binary throttle use (not power use), my car's BSFC map looks like this, and it isn't too far out of the ordinary. This means that as long as I'm shifting soon enough (2500-3000) and not putting energy into the car that'll just have to be bled off in the brakes again momentarily, WOT acceleration has efficiency advantages. That doesn't mean jackrabbiting everywhere (at least with this engine) - nothing about that precludes taking the time to be smooth about shifting, 1st gear gets easier treatment, and with early shifts what remains is a pretty average amount of acceleration. Road conditions also take priority over any part of this, but between AWD and living in a relatively low-traffic area, WOT acceleration applies more often than not.

Cars of the age mine is often used mechanical throttle linkages where accelerator position corresponds 1:1 with throttle plate angle, which leaves in a lot of non-linearity on the average engine. At low RPM, the throttle plate barely needs to be open at all to allow near-atmospheric pressure into the intake manifold. On my car at <2500 RPM, this means it's making nearly full torque by 50% accelerator position. Auto-transmission cars with electronic throttles tend to do a lot of the same, going near WOT at low accelerator positions and mainly using shifting to control higher power levels (with some caveats around turbos). Both of these make the average driver feel like they're using a lot less load/torque than they really are.

synthtel2 wrote:

semi-binary

but isn't binary, itself, binary? Either it is or it isn't and there' can't be a semi-binary or else there are >2 states.

derFunkenstein wrote:

synthtel2 wrote:

semi-binary

but isn't binary, itself, binary? Either it is or it isn't and there' can't be a semi-binary or else there are >2 states.

He's upgraded his gas pedal to TLC; a little more ECC is required but it's much smoother now.

derFunkenstein wrote:

bthylafh wrote:

Chrispy_ wrote:

If you want to go faster, you want to go faster as quickly as possible.

Are you that guy who has to jackrabbit between stop signs?

He's obviously never driven in the snow.

Hah, snow is easy. It's not too different to loose gravel, since there is still some grip.
It's sheet ice that worries me. Changing the direction of two tons of moving steel with zero tyre friction is an artform.

I assumed we're talking about tarmac here, though.

Interesting comments from Synthetel2 about gas pedals being closer to binary than linear; I don't think I've ever owned a car with an electronic throttle, so that kind of figures - where just 10% throttle = 90% peak torque at that engine speed.

Chrispy_ wrote:

Interesting comments from Synthetel2 about gas pedals being closer to binary than linear; I don't think I've ever owned a car with an electronic throttle, so that kind of figures - where just 10% throttle = 90% peak torque at that engine speed.

Interesting comment but complete crap. The throttle exists to make fuel-to-air ratio combustible in petrol engines, which is in a fairly narrow range compared to diesels. My car has an electronic throttle and I know it quite well as I pull it apart and service it with love and care and sweet tenderness... Anyway, throttles are most definitely not "binary" in how they work. The clever little computer in my car modulates the throttle (in conjunction with mass air flow sensor) to give the perfect blend of air and fuel to keep each cylinder (multipoint EFI) burning happily at the required torque output at current RPM as demanded by my right foot. It's a beautiful thing.
Anyway, Ford Barracuda 4 litre six, making 182kW gets 10.5l/100km in city sludgefest, not much less on the open road cos... aerodynamics of flat bed truck. At a constant 80km/h I might get mid 7's. But I'm happy with that because combination of sports tuned suspension (for a 1 tonne load truck) and 0-60mph (for you yanks) in under 7 seconds.

Pancake wrote:

Chrispy_ wrote:

Interesting comments from Synthetel2 about gas pedals being closer to binary than linear; I don't think I've ever owned a car with an electronic throttle, so that kind of figures - where just 10% throttle = 90% peak torque at that engine speed.

Interesting comment but complete crap. The throttle exists to make fuel-to-air ratio combustible in petrol engines, which is in a fairly narrow range compared to diesels. My car has an electronic throttle and I know it quite well as I pull it apart and service it with love and care and sweet tenderness... Anyway, throttles are most definitely not "binary" in how they work. The clever little computer in my car modulates the throttle (in conjunction with mass air flow sensor) to give the perfect blend of air and fuel to keep each cylinder (multipoint EFI) burning happily at the required torque output at current RPM as demanded by my right foot. It's a beautiful thing.

Partially correct (the complete crap comment is incorrect). Modern TBW systems not only manage fuel-air ratios but also manage torque output by proportioning physical throttle-plate movement to actual gas pedal movement, and this management occurs to ensure that the engine never sends torque to the transmission that would exceed the transmission's torque rating.

Some clever boffin has pulled apart and published the throttle maps for the EJ25xT series of Subaru turbo motors. These tables clearly show that actual throttle percentage lags far behind gas pedal percentage through the engine's torque plateau in order to ensure that torque output never exceeds 258 lb/ft or 350 Nm. This torque output appears to be a common target figure for manufacturers of transmissions designed to be bolted to turbo fours, as a review of engine stats in any Car and Driver comparison test of such vehicles will attest.

This TBW system is the entire reason why tuning devices work. The engine computer is intentionally limiting engine output to save the transmission from warranty claims. Tuning devices allow the engine to run at its full achievable output. It's why kids who slap Cobb Accessports on their WRXs tend to grenade their transmissions.

Captain Ned wrote:

This TBW system is the entire reason why tuning devices work. The engine computer is intentionally limiting engine output to save the transmission from warranty claims. Tuning devices allow the engine to run at its full achievable output. It's why kids who slap Cobb Accessports on their WRXs tend to grenade their transmissions.

Well, WRXs also tend to see some pretty good abuse by their young owners who drive...with gusto.

The wife's Golf went from 292 HP stock to just under 400 HP at the wheels with a simple tune and exhaust swap. I'm sure it's eating the transmission life more than it would normally, but goddamn is it fun to drive. If it eats the transmission at 100k instead of 200k miles, so be it.


I still prefer throttle cables to electronic throttles. One more thing to break, one more thing to introduce lag, etc. I don't mind the system on my C5, but I really wish it were simpler.

Waco wrote:

Well, WRXs also tend to see some pretty good abuse by their young owners who drive...with gusto.

And think the F&F flicks are drivers-ed movies.

Waco wrote:

I still prefer throttle cables to electronic throttles. One more thing to break, one more thing to introduce lag, etc. I don't mind the system on my C5, but I really wish it were simpler.

Eh. Can make that argument against any electronic upgrade that automotive engines have seen over the past 60-odd years, but efficiency and reliability keep improving. The next step is a GDI engine with no throttle plate at all.

ludi wrote:

Waco wrote:

I still prefer throttle cables to electronic throttles. One more thing to break, one more thing to introduce lag, etc. I don't mind the system on my C5, but I really wish it were simpler.

Eh. Can make that argument against any electronic upgrade that automotive engines have seen over the past 60-odd years, but efficiency and reliability keep improving. The next step is a GDI engine with no throttle plate at all.

A lot of the electronic upgrades improve performance, efficiency, etc. I have no problem with complicated EFI, direct injection, etc - it's the other electronics that fail and add complexity for no efficiency or performance gain that bother me.

Captain Ned wrote:

Partially correct (the complete crap comment is incorrect). Modern TBW systems not only manage fuel-air ratios but also manage torque output by proportioning physical throttle-plate movement to actual gas pedal movement, and this management occurs to ensure that the engine never sends torque to the transmission that would exceed the transmission's torque rating.

Can't help but feel that modern pedal feel could be improved immensely if they just used an eccentric cam on the throttle cable to make engine torque slightly closer to linear in relation to the pedal travel.

Chrispy_ wrote:

Can't help but feel that modern pedal feel could be improved immensely if they just used an eccentric cam on the throttle cable to make engine torque slightly closer to linear in relation to the pedal travel.

Modern feel?

I want to shout "YAW YAW" and squeeze my knees and feel the thing go.

I never thought of but the TBW system probably is why my Durango seems pretty nonchalant when you mash the gas from a dead stop, cause the power once you hit about 30mph seems a lot more so. I always chalked it up to the revs needing to get up, but I bet it has more to do with the programming TBW than the engine's torque curve. Probably saves the AWD system from being too abused.

My 03 Subaru had a TBW and on that the throttle opening wasn't noticeably different but the throttle closing was very slow - that helps with emissions but sucks when you are going for a quick gear change.

Chrispy_ wrote:

Interesting comments from Synthetel2 about gas pedals being closer to binary than linear; I don't think I've ever owned a car with an electronic throttle, so that kind of figures - where just 10% throttle = 90% peak torque at that engine speed.

Pancake wrote:

Interesting comment but complete crap. The throttle exists to make fuel-to-air ratio combustible in petrol engines, which is in a fairly narrow range compared to diesels. My car has an electronic throttle and I know it quite well as I pull it apart and service it with love and care and sweet tenderness... Anyway, throttles are most definitely not "binary" in how they work. The clever little computer in my car modulates the throttle (in conjunction with mass air flow sensor) to give the perfect blend of air and fuel to keep each cylinder (multipoint EFI) burning happily at the required torque output at current RPM as demanded by my right foot. It's a beautiful thing.

You're both thinking I said things I didn't actually say.

10% accelerator doesn't map to 90% anything unless you're at extremely low RPM (probably below idle), have an extremely large throttle body per the engine's displacement, or are abusing a TBW amp that makes it look to the ECU like you're pressing the accelerator further than you are (yeah, those exist). If an engine somehow did naturally end up with characteristics like that in conditions closer to cruise, it would be very obnoxious to drive, and the manufacturer would have put some kind of non-linearity the other direction into the system to compensate.

I never said TBWs were binary. It's a curve, it's just that most of the curve tends to be compressed into an early part of the accelerator's travel. Airflow and fuelling have to be matched, and neither is perfectly responsive, but fuelling can be changed much much quicker and more precisely than airflow, so in practice ECUs tend to control airflow on the basis of accelerator position (or any other source for an abstract power demand, maybe to smooth out shifting or something) and then adjust fuelling to match however much air is actually flowing. (GDIs have potential to throw a lot of wrenches in this model. AFRs may tweak based on accelerator position rather than something further down the chain if the goal is responsiveness. DFCO exists and is another big exception.)

Waco wrote:

I still prefer throttle cables to electronic throttles. One more thing to break, one more thing to introduce lag, etc. I don't mind the system on my C5, but I really wish it were simpler.

captaintrav wrote:

I never thought of but the TBW system probably is why my Durango seems pretty nonchalant when you mash the gas from a dead stop, cause the power once you hit about 30mph seems a lot more so. I always chalked it up to the revs needing to get up, but I bet it has more to do with the programming TBW than the engine's torque curve. Probably saves the AWD system from being too abused.

notfred wrote:

My 03 Subaru had a TBW and on that the throttle opening wasn't noticeably different but the throttle closing was very slow - that helps with emissions but sucks when you are going for a quick gear change.

TBWs should have no inherent reason to be that laggy, but somehow not one of them I've ever driven feels as crisp as a decent mechanical system. Chrysler(/Dodge/Jeep) in particular seems to have major issues with this.

Slow-acting DFCO (deceleration fuel cutoff) isn't inherently tied to TBWs, but they seem to have arisen about the same time. Dammit ECUs, when I let off the gas I don't want you continuing to burn fuel for an extra second! As if they think I'm unsure I actually want the engine braking I asked for.

Chrispy_ wrote:

Can't help but feel that modern pedal feel could be improved immensely if they just used an eccentric cam on the throttle cable to make engine torque slightly closer to linear in relation to the pedal travel.

Auto-transmission '97 Legacy Outbacks (EJ25D) use a dual-cam system that achieves this effect (probably many others do too, but that's the one I've seen it on).

Chrispy_ wrote:

Can't help but feel that modern pedal feel could be improved immensely if they just used an eccentric cam on the throttle cable to make engine torque slightly closer to linear in relation to the pedal travel.

Almost all throttle bodies and carburetors in recent (a few decades) memory have an eccentric cam to actuate the throttle. Electronic ones map to something similar.

synthtel2 wrote:

TBWs should have no inherent reason to be that laggy, but somehow not one of them I've ever driven feels as crisp as a decent mechanical system. Chrysler(/Dodge/Jeep) in particular seems to have major issues with this.

There's no real lag on sports cars with them - but on regular cars I imagine they do it to make "smooth driving" easier.

Waco wrote:

synthtel2 wrote:

TBWs should have no inherent reason to be that laggy, but somehow not one of them I've ever driven feels as crisp as a decent mechanical system. Chrysler(/Dodge/Jeep) in particular seems to have major issues with this.

There's no real lag on sports cars with them - but on regular cars I imagine they do it to make "smooth driving" easier.

The POS Jeep Renegade rental I had last week took forever for the gas pedal to do anything, but I sorta expect that on a Jeep "Trail Rated" product for ease of off-road driving.

I know on some Dodge products, so I imagine Chrysler/Jeep as well, tunes from Superchips did vastly alter the throttle response. At least for my friend that had one on his Durango, unfortunately it gets locked to the VIN so I can't reprogram mine as well.

Some TBWs get it down to where it doesn't feel obviously wrong, but IME it's still around the bad end of mechanical throttles (with oversized intake manifolds, that kind of thing). At the good end of TBWs, I can see it being personal preference though; between a non-eccentric mechanical throttle, small intake manifold, and substantial air reservoir just upstream of the throttle body, my car's accelerator probably has a lot more bite than the average driver would consider comfortable.

Chrysler/Dodge/Jeep just doesn't know how to build electronics that don't suck, AFAICT. Their performance vehicles (not a Demon or anything, but definitely 300C and I think some SRT stuff) are still blatantly laggy, and I'd agree with Ned on Jeep's goals if not for how even on a Wrangler it's [push accelerator 10% -> nothing happens -> wait a few hundred millis -> BOOM hope you weren't trying to do a smooth takeoff on ice sucka!]. If it's borderline impossible to finely modulate power delivery on a freaking Jeep Wrangler, someone has dun goofed.