Reason to low mileage

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bellwilliam
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Joined: Thu Jan 23, 2003 4:15 am

Reason to low mileage

Post by bellwilliam »

It always drove me nuts when I get low mileage (20-24) since day one. I know there have been a lots of explanations: like cold weather (defrost, fuel) and hot weather (A/C on), etc. but it doesn't explain why I always get city EPA mileage with all my other cars (I have 7 cars), but on Vibe, it is much worse.anyway, yesterday I met a Toyota engineer who worked on Matrix. w/o telling him my story, he explained to me why Matrix guy are getting mileage number all over the map. sorry if I don't explain it well:cat temperature is one of the most important issue a manufacturer has to deal with. because of 8 yr warranty on emission item. so to keep cat temperature down, solution is to add fuel to cool off exhaust gas. He said the ECU map that tells it when to add more fuel when it senses loads. Speed is a main criteria for adding fuel. Because Matrix is a heavier car (than Corolla), ECU kicks in extra fuel at lower speed. for example, 70MPH instead of 80MPH (he doesn't remember the exact number). He claims with Matrix you would see a MUCH better mileage (compare to other cars) if you drop your cruising speed just below where it starts to run rich to cool off cat. He claims in a lighter Corolla, this number (speed/MPH) is much higher. so you can cruise at much higher speed, without big mpg penalty.This explains why some of you are getting 35MPG (cruising at 60mph), and some of us getting 22MPG (cruising at 80mph).again I don't know what this magic number MPH is. and I am not sure if what he says is true (I do know he is a Toyota design engineer).
Bellwilliam2003 S/C VibeTrim : Base, Abyss , AutoOptions: Moon & Tunes, Power Upgrades: Supercharger, Split Second A/F controller, 225/45-17, My other cars are PTE Miata, 13 Tesla S, 13 Volt, 06 997
DavidPIL
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Re: Reason to low mileage (bellwilliam)

Post by DavidPIL »

Hey bellwilliam.If your statement is correct, as per the GT, I would guess the magic number is around 3400 rpm. I assumed it was the VVT but I notice a mini-kick around that RPM, no matter what the speed. The engine does sound different cruising at that rpm range as well. If I remember correctly, that's around 76mph?My mother's Aveo cruises at maybe 2800 rpm around that same speed. From what she's told me, her MPG is fairly consistent in the mid 30's for highway driving and Low 30's upper 20's for city.Would love to be cruisin at 75 mph with only 2800 rpms in the GT though I'm sure I wouldn't even be able to go up the slightest of hills without slowing down. Damn that low torque!!!!Dave
coldmm803
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Post by coldmm803 »

thats good to know bellwilliam, during my 2 yrs of owning my vibe i've noticed that if you set the cruise at 70 AND dont accel much/hard for passes (use the cruise stick and bump up a few times 1mph per bump) you can easily get 35+mpg. the big hit in gas mileage is when the rpms are consistently over 3k. i dont remember so i'm guessing that crusing at 80 puts the rpms around 3500.i see in your sig that you have the supercharger, i'm not sure if the terms are the same as with a turbo but depending on where you hit "boost" is going to affect your mpg too, if boost is at 4k and your crusing at 3500 i would expect the ecu to kinda prep for hitting that boost stage and add more gas earlyi also see that some of your other cars are more sports cars and their ecu/engine maybe set/tuned to be more efficient at 75-80. the vibe is no sports car. as much as i hate sayin this but its more of an older persons car, the people that arent going to accel much over 3k if any
VIBEwithanO
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Re: (coldmm803)

Post by VIBEwithanO »

I've also noticed this. I used to take my Vibe on business over the road, and would cruise between 75-80 MPH. By decreasing this to 67-70 MPH, I was able to get MUCH better mileage (12-15 MPG). Didn't know this was the reason. Thanks for the info.
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bellwilliam
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Post by bellwilliam »

I also want to add: this engineer did say auto's magic mph number is lower than 5 speed.I do have a supercharger (one of the very early adapter). but at cruising speed, almost never in boost. GM supercharger is controlled by a piggyback ECU, so factory ECU probably doesn't know the piggyback is adding fuel in boost.If this is true. are the guys getting great mileage cruising at 65MPH ? on many of my long trips. I tried setting my cruise on 80MPH (I am still one of the slowest around), I get about 25mpg. may be if I set it to 65MPH, I will get 35mpg
Bellwilliam2003 S/C VibeTrim : Base, Abyss , AutoOptions: Moon & Tunes, Power Upgrades: Supercharger, Split Second A/F controller, 225/45-17, My other cars are PTE Miata, 13 Tesla S, 13 Volt, 06 997
coldmm803
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Post by coldmm803 »

on 2-3 of my trips between school and home (120 miles) i have set my cruise to to 70 (which by gps is 68) and the slow lane often going 65 aka the speed limit and passed very little due to not many cars around and have gotten 40mpg. acceleration is a big part to gas mileage. acceling at my normal rate will get me around 32-35mpgwhen your goin 80 its more likely 77-78 thus why you are one of the slower ones, not suggesting you speed up but just fyi.while owning my vibe i've kept an excel sheet of my mileage and i've avged 28 overall
harryyiii
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Re: Reason to low mileage (bellwilliam)

Post by harryyiii »

Now that Toyota is the new king of the block, their arrogance is showing. Instead of putting a properly sized cat in, they waste fuel to save them a few pennies so they can use the money to build full size trucks in Texas. And they do it in a manner that does not show up on the EPA test. If you have a bigger catalyst, each part generates less heat, and there is more surface area to dissipate the heat. No need to dump fuel. I like my Vibe and have no problems with it other than disappointing gas mileage, but with the premature transmission, clutch and engine failures documented on this site, and the frumpy styling and lousy handling of most Toyota products, Toyota is trying to take over from GM in the hubris department also. As an aside, does anyone make a chip to bypass this stupid problem.
Petrucci914
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Re: Reason to low mileage (harryyiii)

Post by Petrucci914 »

I always thought this was common knowledge. Going faster makes your RPMs higher. The longer you run at higher RPMs the more gas you'll suck. I'd love to stay at 65-68 most of the time but so many *******s ride your bumper. I can't even speed anymore without bumper-sniffers. I also heard that when you feel that your transmission is going to shift, you let off the gas..........this is supposed to save fuel as well.
2003 Pontiac Vibe Base - AutomaticTRD Supercharger w/ Smoothflow PulleyaFe Drop-in Filter - DC Sports HeaderFull 2.25" Exhaust -Magnaflow Catback + CatsOptima RedTop - Tru-Cool Tranny Cooler
bellwilliam
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Post by bellwilliam »

yes going faster yields lower mileage. but in the case of Vibe. it is a lot more dramatic. this is the only forum I see posting of 15mpg to 40mpg. usually variation is much less than that. what the engineer was saying is that ecu is dumping fuel in order to lower cat temperature. this happens in all cars, but much earlier (in MPH) in a Matrix.this is the forum that many complains about the mileage, yet many reporting excellent mileage. see Coldmm803's post. he can get up to 40mpg, yet he only averages 28mpg since day 1, doesn't means mean 1/2 of the time, he is getting low 20s mpg !! with Vibewithan0, he claims a variation of 12mpg by dropping 10MPH. this just doesn't happen with any other cars I know of.one thing I want to add about my supercharger. it is well known that GM supercharger runs extra rich (10:1 and lower) at boost, this is to save the cat.
Bellwilliam2003 S/C VibeTrim : Base, Abyss , AutoOptions: Moon & Tunes, Power Upgrades: Supercharger, Split Second A/F controller, 225/45-17, My other cars are PTE Miata, 13 Tesla S, 13 Volt, 06 997
ProtonXX
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Re: (bellwilliam)

Post by ProtonXX »

find a way to hack the cat lol. I see the same thing too and its kind of annoying my cruising speed is 80mph but that means 22mpg. 55 cruise gets about 40 mpg
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joatmon
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Post by joatmon »

So adding more fuel makes the mix richer, whcih cools the catalytic converter?what happens if we could override this inefficiency, we'd melt our cats?a quick look and I couldn't find a way to get my scangauge to display air/fuel ratio.anybody got an air/fuel gauge hooked up, would be interesting to see a curve of mix ratio to speed and/or rpms
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bellwilliam
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Re: (joatmon)

Post by bellwilliam »

yes, running richer will make cat run cooler. most factory supercharer/turbocharger tends to run rich for this reason. running leaner, will definetely shorten cat's life. don't know by how much. but remember manufacturer has to warranty it for 8 yrs, so they are definetely on the safe side.I have a Scangauge II, it won't read A/F ratio. even if it is capable of doing that. it won't work, because Vibe (most of stock cars) only has narrow band. you need a wideband oxygen sensor.when I had my supercharger installed. it was running 9.8:1, real rich. that's the reason I added a SS A/F box to make it run leaner to 11.5:1. Even SS told me not to run 12.5:1 for max power.
Bellwilliam2003 S/C VibeTrim : Base, Abyss , AutoOptions: Moon & Tunes, Power Upgrades: Supercharger, Split Second A/F controller, 225/45-17, My other cars are PTE Miata, 13 Tesla S, 13 Volt, 06 997
pacerman
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Post by pacerman »

Heres some interesting stuff on A/F rations and CATS.......from Toyota........http://www.autoshop101.com/forms/h64.pdf
2005 Vibe...Abyss ...AWD53 Stude HT, 76 AMC Pacer, 91 Camry 4WD,318 John Deere, Strong GS-210 Electric Bike
pacerman
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Re: Reason to low mileage (bellwilliam)

Post by pacerman »

Found this during a search on this topic......Criticisms of catalytic convertersCatalytic converters have proven to be reliable devices and have been successful in reducing noxious tailpipe emissions. However, they may have some adverse environmental impacts in use: * The requirement for a rich burn engine to run at the stoichiometric point means it uses more fuel than a "lean burn" engine running at a mixture of 20:1 or less. This increases the amount of fossil fuel consumed and the carbon dioxide emissions of the vehicle. However NOx control on lean burn engines is problematic at best, and many Lean Burn engine manufacturers are considering rich burn variations. Another solution is to increase the amount of biofuels used - if 100% biofuel was used the engines would be CO2 neutral. * Catalytic converters are "estimated" to account for 50% of total nitrous oxide (dinitrogen oxide, 'laughing gas') emissions to atmosphere. While N2O emissions in these concentrations are not harmful to human health, it is a potent greenhouse gas, accounting for around 7% of the overall greenhouse effect despite its small concentration in the atmosphere. The California Air Resources Board is investigating this issue, and will introduce legislation to address it if necessary.
2005 Vibe...Abyss ...AWD53 Stude HT, 76 AMC Pacer, 91 Camry 4WD,318 John Deere, Strong GS-210 Electric Bike
manicdan
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Post by manicdan »

ok 2 things:1 i have a scangauge II and with it on a family trip i watched a few details while driving, while in 6th gear going 70ish mph my car is quite quiet, sounds like any normal sedan. once u go up past 75mph the fact that i have intake and exaust redon clearly shows. as the noise lvl goes high enough to make a trip quite annoying. also u can see very clearly the mpg jump between 45 and 25 between those 5mph changes. to try and get the most accurate mpg i used cruise control and it still bounces around by atleast 5mpg, but its very easy to see how quickly the engine load and air resistance reduce our ecconomy.second, if i wanted to replace my cat with a larger one would i see much of a change with my mpg or horsepower. right now i sit at 23-25mpg each tank and its cause i do deliveries in my car so its alot of driving in devlopments. i would go for a better cat if it ment 2-3 mpg increase while loosing almost no HP. but is that possible?
viberider
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Good thread thanks guys and gals?

Post by viberider »

Helps me a newby to the forum to understand why such poor mileage in my new 07 Vibe. I love it otherwise. It sure does not feel like a small car in it's ride and it's awful easy to get to 80 MPH on the freeway.
Petrucci914
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Re: Good thread thanks guys and gals? (viberider)

Post by Petrucci914 »

Welcome to the forum. Give us some details on your driving. Mostly highway or city? Average speed? If you're cruising at 80 on the highway at all times that will suck A LOT of gas. It is best to keep the Vibe under 70 on the highway to get the best mileage. This has to do with the catalytic convertor temperatures and emissions control and the RPM by which you're at over a period of time.
2003 Pontiac Vibe Base - AutomaticTRD Supercharger w/ Smoothflow PulleyaFe Drop-in Filter - DC Sports HeaderFull 2.25" Exhaust -Magnaflow Catback + CatsOptima RedTop - Tru-Cool Tranny Cooler
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joatmon
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Re: Good thread thanks guys and gals? (Petrucci914)

Post by joatmon »

Quote, originally posted by Petrucci914 » Give us some details on your driving. http://forums.genvibe.com/zerothread?id=28445
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