-
Why an Aveo automatic gets poor city MPG
Our 2009 Aveo5 is only a few months old with less than 2000 miles on it. We like the car very much except that the city MPG has been disappointing. The city EPA estimate is 25. The best we have been able to get is 22 MPG. After installing a scan gauge and driving very conservatively I was determined to find out specifically why the fuel economy is so inadequate.
After considerable research I found the transmission is made by Aisin, a Japanese manufacturer with a good reputation for quality transmissions. It is an ordinary 4 speed, with no overdrive. The same transmission is found on all Aveos made from 2004 to 2010. I recently found the service manual for this transaxle, Aisin 81-40LE. It can be found on-line at: http://www.anagabriela.ro/.../2.%20AISI ... NSAXLE.pdf
The graph on page 5A2-12 shows the manufacturer’s specification for shift points. (The graph is stated in KMH, so I’ve converted the figures to MPH for this discussion.) The graph shows the shift points will vary somewhat according to the TPS (throttle position) reading. On my car a scan gauge registers the TPS reading at idle at about 16; very conservative (slow) acceleration would be about 25; brisk or above average acceleration would be about 35 TPS.
According to the graph, at 25 TPS the shift points should be at about 11, 20 and 27 MPH. At 35 TPS it should shift at about 12, 22, and 32 MPH. I compared what I am actually getting on my car, at about 35 TPS, which would be considered average or brisk acceleration. I found it actually shifts at about 15, 25, and 45 MPH. In other words, the upshift into the highest gear (fourth) is much too late. Most 4 speed transmissions typically shift at approximately 10, 20 and 30 MPH. The delayed shift into high gear at around 45 is a major reason for delivering poor city FE. I live in suburbia. On major roads, typically the speed limit is 40. Unfortunately, when there is traffic it is impossible to break 45 – thus the car is spending most of its time in first, second and third gears at best, and it virtually never goes into high gear, which would yield the best fuel efficiency.
The transmission shift points are entirely determined by an electronic module called the transmission control module (TCM) which was designed and pre-programmed by Chevrolet. The shift points for which it is programmed are widely different than the documented specifications of the manufacturer, Aisin. I visited a Chevrolet dealer and spoke with the service manager to see if the TCM could be reprogrammed. He told me that they could do nothing to change it, unless Chevrolet had issued a service bulletin update for the program (which is has not done in the past five years that Chevy has been using this transmission on the Aveo). In other words, unless and until Chevy engineering rewrites the programming of the shift points and offers it as an update for dealers to install, nothing can be done to rectify the existing discrepancy. I then visited my local transmission shop (AAMCO) and asked the same questions. They confirmed that there is no way to reprogram the TCM unless Chevrolet rewrites the programming for it.
From what I have read on the web this is a very common complaint for Aveos. Most owners are unaware that their cars are late in shifting into fourth gear and frustrated with their poor city mileage. Seeing that there is documentation supporting the fact that the TCM programming of Chevrolet is greatly divergent from the specifications of Aisin, the manufacturer of the transmission, I believe Aveo owners have a valid grievance against GM and should press to have the situation rectified.
Who can we complain to? How can we unite to complain effectively and have Chevrolet correct this situation?
-
Re: Why an Aveo automatic gets poor city MPG
Quote:
Originally Posted by Thymeclock
Unfortunately, when there is traffic it is impossible to break 45 – thus the car is spending most of its time in first, second and third gears at best, and it virtually never goes into high gear, which would yield the best fuel efficiency.
Presumably when you finish accelerating, to let's say 40 mph, you back off the throttle from 35 TPS to cruise at a constant speed, and your TPS value would drop.
Are you saying the transmission still won't upshift at ~40 even with the lower TPS value at cruise?
-
Re: Why an Aveo automatic gets poor city MPG
Quote:
Originally Posted by Thymeclock
Unfortunately, when there is traffic it is impossible to break 45 – thus the car is spending most of its time in first, second and third gears at best, and it virtually never goes into high gear, which would yield the best fuel efficiency.
Quote:
Presumably when you finish accelerating, to let's say 40 mph, you back off the throttle from 35 TPS to cruise at a constant speed, and your TPS value would drop.
Of course, the TPS reading does drop as you press on the accelerator less.
Quote:
Are you saying the transmission still won't upshift at ~40 even with the lower TPS value at cruise?
No, it won't - but it makes no difference. It won't go into 4th gear at all until 45 mph is reached, no matter what the acceleration rate (which is gauged by the TPS) is.
-
Re: Why an Aveo automatic gets poor city MPG
That sucks - pardon my French.
On the off chance you don't get any satisfaction from GM, I wonder if you'd consider going so far as to look at spoofing the TCM. Modifyng the TPS and/or speedometer signal comes to mind as a way to force an earlier upshift.
(Side note: some Honda V6 owners - Ridgeline & Odyssey - report being able to trick the TCM into locking the torque converter earlier (a few MPH) than normal by briefly shifting into neutral, then back to drive.)
But let's not get ahead of ourselves. You've obviously done your homework and identified a significant gap between the programming and the hardware that the manufacturer should be made aware of.
-
Re: Why an Aveo automatic gets poor city MPG
Quote:
Originally Posted by MetroMPG
That sucks - pardon my French.
No kidding! (I could think of more vulgar ways of phrasing it, but I won't elaborate...)
My next step will be to contact and complain to GM - not just their customer service, but also the honchos in charge of engineering. I'm currently collecting corporate names and contacts. If ever there was a business model with too many top-heavy official positions, GM is it.
Quote:
On the off chance you don't get any satisfaction from GM, I wonder if you'd consider going so far as to look at spoofing the TCM. Modifyng the TPS and/or speedometer signal comes to mind as a way to force an earlier upshift.
I doubt that fudging the TPS would work. Don't forget the shift point is just marginally dependent upon that factor. I don't see how you could change the speedometer signal without screwing up other parameters.
What I thought might work (but it's really a long shot) is that maybe there might be a different (non-Aveo) TCM made for another model car that could be transplanted, i.e. from a different make that has the same transaxle. The 81-40LE was also used on the Daewoo Kalos & Lacetti, possibly the Ford Fiesta <?>, the Suzuki Forenza ,<?>, and a slightly different but essentially the same Aisin transaxle is used on the Toyota Yaris and Echo.
Quote:
But let's not get ahead of ourselves. You've obviously done your homework and identified a significant gap between the programming and the hardware that the manufacturer should be made aware of.
I presume you mean Chevy. Aisin made the tranny but they're just the supplier to GM-Daewoo. They have no control over the erroneous crap programming of the TCM running it, which is Chevy's involvement.
-
Re: Why an Aveo automatic gets poor city MPG
Ok, let's calm down here. The pistons rings are not even set yet and true fuel economy won't be seen till at least 10,000miles which is when the engine is broken in.
-
Re: Why an Aveo automatic gets poor city MPG
Quote:
Originally Posted by NorthernAveo
Ok, let's calm down here. The pistons rings are not even set yet and true fuel economy won't be seen till at least 10,000miles which is when the engine is broken in.
I am calm, but I don't find that credible. Do you think the EPA runs all vehicles tested for 10,000 miles before establishing a fuel estimate?
Besides, piston rings have nothing to do with the shift points of an automatic transmission.
-
Re: Why an Aveo automatic gets poor city MPG
Can you show me any resource that says 10,000 miles is a valid break in point for a motor vehicle engine?
I don't believe in all the time I've been working on cars, I've ever heard that number. I've heard closer to 5,000 and I think that's about as high as I'd really be willing to believe.
-
Re: Why an Aveo automatic gets poor city MPG
i thought with the newer materials and supposed "dyno" testing most engines were considered broken in leaving the factory? i am not saying this for the aveo, but the term "broken in" means different things though. its not like there is a break in layer on the rings, or that if you tore down the engine at 10001 miles it would not be as close to factory specs as one would think. I have seen cars with 30-40k with still signs of crosshatching on the cylinder walls..
If you go to a nissan or toyota dealer with 200k miles they like to tell you the car is barely broken in (until you go to trade it in). But if the engine is built wrong it wont last nearly 10000 miles either.
If we are talking "seasoned" i know a lot of people tell you to drive easier and not at a consistent high rpm for the first 500 miles of ownership to seat the rings. And also change your oil at the 500 miles mark ( i have always done the oil change). I don't know that i believe this with factory built car either though, i "break them in" the way i am going to drive it the rest of its life.
-
Re: Why an Aveo automatic gets poor city MPG
Quote:
Originally Posted by Unidentifiable
Can you show me any resource that says 10,000 miles is a valid break in point for a motor vehicle engine?
I don't believe in all the time I've been working on cars, I've ever heard that number. I've heard closer to 5,000 and I think that's about as high as I'd really be willing to believe.
I use 10,000 as a nice round number to make sure it is completely broken in. Different people have different driving styles and thus, break in will be different. I have tested many engine and compression is never complete at 5000-6000miles. At 10,000, everythign is usually broken in.
This engine is not dyno broken in at all. Any stating that thinks their mass produced 4 banger engine in korea is given the same treatment as a viper engine needs to get their info straight? They go on the dyno for one pass on the assembly line as they leave jsut as a quick check.
Even at 5000miles you stated, you are calculating the economy at 2000miles which means, the engine is not broken in yet and anyone stating that an engine doesn't need to be broken today needs to learn a lot more about engines.
People need to relax and stop getting all worried that their car isn't getting the exact fuel economy off of the dealer lot. Let the engine break in and the compression build and you will see it will climb over the next months.
-
Re: Why an Aveo automatic gets poor city MPG
Do you understand that the transmission is not shifting at the points specified by the manufacturer?
It doesn't go into high gear until 45 MPH and there is no way I can make it up-shift any sooner. That affects my fuel economy when I'm mostly driving 35-40.
Even if I wait until 10,000 miles, the correct shift points won't miraculously appear then, will they?
-
Re: Why an Aveo automatic gets poor city MPG
Quote:
Originally Posted by Thymeclock
Do you understand that the transmission is not shifting at the points specified by the manufacturer?
It doesn't go into high gear until 45 MPH and there is no way I can make it up-shift any sooner. That affects my fuel economy when I'm mostly driving 35-40.
Even if I wait until 10,000 miles, the correct shift points won't miraculously appear then, will they?
I would then remove the negative connection from the battery and reset the ECM which will reset the tranny control as well. If that doesn't solve it I would take it to the dealer to have them check on it.
Also, is the Aveo auto a three speed with a lockup torque convertor? If so, they are programmed to go into torque convertor lockup at a certain speed and not before seeing in most cases the manufacturer thinks the engine doesn't have enough horsepower and/or torque to hold the lockup at a lower speed without lugging the engine.
I have a feeling that the 4th gear is the torque convertor lockup and not an actual gear.
Also it won't lockup till the engine is warm.
-
Re: Why an Aveo automatic gets poor city MPG
Quote:
Also, is the Aveo auto a three speed with a lockup torque convertor? If so, they are programmed to go into torque convertor lockup at a certain speed and not before seeing in most cases the manufacturer thinks the engine doesn't have enough horsepower and/or torque to hold the lockup at a lower speed without lugging the engine.
I have a feeling that the 4th gear is the torque convertor lockup and not an actual gear.
I suggest you re-read my original post and try to comprehend it before responding.
The transaxle is the Aisin 81-40LE. It is the only automatic transmission ever used in all Aveos made since 2004. It IS a four speed transmission. Everything about that specific transaxle is documented, including the specifications for shift points in the Aisin service manual, which is available on-line.
Your conjecture has no basis in fact; as such it amounts to misinformation.
-
Re: Why an Aveo automatic gets poor city MPG
Quote:
Originally Posted by Thymeclock
Quote:
Also, is the Aveo auto a three speed with a lockup torque convertor? If so, they are programmed to go into torque convertor lockup at a certain speed and not before seeing in most cases the manufacturer thinks the engine doesn't have enough horsepower and/or torque to hold the lockup at a lower speed without lugging the engine.
I have a feeling that the 4th gear is the torque convertor lockup and not an actual gear.
I suggest you re-read my original post and try to comprehend it before responding.
The transaxle is the Aisin 81-40LE. It is the only automatic transmission ever used in all Aveos made since 2004. It IS a four speed transmission. Everything about that specific transaxle is documented, including the specifications for shift points in the Aisin service manual, which is available on-line.
Your conjecture has no basis in fact; as such it amounts to misinformation.
It is strange why you are being so rude when all I was doing was stating the case if it has a lockup torque convertor.
You can see that the first thing I replied with had a question mark right? [-X
Here is what I asked.
Also, is the Aveo auto a three speed with a lockup torque convertor?
Maybe you should read before you act like that when I was trying to help. I was not spreading misinformation at all. The information given was if in deed the tranny was a 3 speed with torque convertor lockup and I never stated that it was for sure it was.
-
Re: Why an Aveo automatic gets poor city MPG
Quote:
Originally Posted by NorthernAveo
Quote:
Originally Posted by Thymeclock
Quote:
Also, is the Aveo auto a three speed with a lockup torque convertor? If so, they are programmed to go into torque convertor lockup at a certain speed and not before seeing in most cases the manufacturer thinks the engine doesn't have enough horsepower and/or torque to hold the lockup at a lower speed without lugging the engine.
I have a feeling that the 4th gear is the torque convertor lockup and not an actual gear.
I suggest you re-read my original post and try to comprehend it before responding.
The transaxle is the Aisin 81-40LE. It is the only automatic transmission ever used in all Aveos made since 2004. It IS a four speed transmission. Everything about that specific transaxle is documented, including the specifications for shift points in the Aisin service manual, which is available on-line.
Your conjecture has no basis in fact; as such it amounts to misinformation.
It is strange why you are being so rude when all I was doing was stating the case if it has a lockup torque convertor.
You can see that the first thing I replied with had a question mark right? [-X
Here is what I asked.
Also, is the Aveo auto a three speed with a lockup torque convertor?
Maybe you should read before you act like that when I was trying to help. I was not spreading misinformation at all. The information given was if in deed the tranny was a 3 speed with torque convertor lockup and I never stated that it was for sure it was.
If you had understood what I wrote and researched the manual (as I did) you wouldn't have needed to ask or speculate about it. [-X There was no benefit in your offering an hypothetical opinion without first understanding what it actually is, despite your prefacing it as a question.
Fourth gear is fourth gear, and it also has converter lockup.
-
Re: Why an Aveo automatic gets poor city MPG
Thymeclock, can you post up a picture of the shift point graph you are looking at? I think I have the same manual as you but the link you posted isn't working. The manual I have only shows a 1.2, 1.4 and 1.5l engine.
-
Re: Why an Aveo automatic gets poor city MPG
assumed it was typical that a 4speed slushbox would have a tall 3rd gear relative to 2nd...
lol, and w/ the e-tec i don't think its the tranny thats killing the economy...
-
Re: Why an Aveo automatic gets poor city MPG
Quote:
Originally Posted by Daox
Thymeclock, can you post up a picture of the shift point graph you are looking at? I think I have the same manual as you but the link you posted isn't working. The manual I have only shows a 1.2, 1.4 and 1.5l engine.
The link I provided is inaccessible at times, unfortunately (like today, when I checked it).
Here are the links as I copied them:
http://www.anagabriela.ro/.../2.%20AISI ... NSAXLE.pdf
http://www.anagabriela.ro/Manuale%20...0TRANSAXLE.pdf
The same link I provided to EcoModder worked when I uploaded it. The link can also be found by Googling: [Aisin 81-40LE "shift points"]. (Google what is between the [] marks verbatim, and you will recognize it, with it being only one of very few choices.)
Alternatively, I previously printed out the shift points graph that is relevant, scanned it as a JPEG file and tried to post it right now as an attachment, but this site isn't accepting it.
I could use some help on this as I think I'm doing it correctly but I can't successfully upload my attachments.
-
Re: Why an Aveo automatic gets poor city MPG
-
Re: Why an Aveo automatic gets poor city MPG
Thanks ontarian_frog. That link worked. That is a different manual than I had too... Gonna have to look it over.
I'll look into your attachment problem too Thymeclock.
-
Re: Why an Aveo automatic gets poor city MPG
Alright, it looks like Darin got the attachments working again.
Which map is your vehicle following?
Here is the map for the economic mode.
[attachment=1:hkhjhdg9]autoeco.JPG[/attachment:hkhjhdg9]
And here is the map for the power mode.
[attachment=0:hkhjhdg9]autopower.JPG[/attachment:hkhjhdg9]
-
Re: Why an Aveo automatic gets poor city MPG
Quote:
Originally Posted by Daox
Alright, it looks like Darin got the attachments working again.
Which map is your vehicle following?
Yes, those are the correct ones. The link provided is working, too.
I'm going by "economy" mode. The Aveo doesn't have any selector switch to control two different modes as some other Daewoo cars might.
The map for "power" mode can't possibly apply here.
As you can see from the map the TC lockup should occur at 45 MPH. But I'm not feeling any real drop in RPM's (nothing below 2000) that would indicate that it has entered fourth gear, until I hit 45. At 45 MPH, presumably at TC lockup, a noticeable drop in RPM occurs, and the MPG goes up.
-
Re: Why an Aveo automatic gets poor city MPG
I know its not exactly what you are looking for, but have you tried using the hold control?
Quote:
The automatic features a “hold control” button. Selecting “hold control” turns the four-speed automatic into a three-speed manual, with the driver changing gears by moving through the gated shifter. The “hold control” mode also enables the driver to better control wheel spin at low speeds on slippery surfaces by manually selecting a higher gear.
-
Re: Why an Aveo automatic gets poor city MPG
Quote:
Originally Posted by Daox
I know its not exactly what you are looking for, but have you tried using the hold control?
Quote:
The automatic features a “hold control” button. Selecting “hold control” turns the four-speed automatic into a three-speed manual, with the driver changing gears by moving through the gated shifter. The “hold control” mode also enables the driver to better control wheel spin at low speeds on slippery surfaces by manually selecting a higher gear.
Yes, and I think we had this same discussion on Ecomodder. If you think about it, hold control will do nothing useful for this problem. If you are in first gear selector position and apply hold, it will remain in first. Same thing applies for second position. But if you select drive position, and apply hold while in third or fourth gear, the hold function is not going to keep it in a higher gear: for the simple reason that if it really did 'hold' it in gear and it were not allowed to downshift, the engine would lug. Also the car can't start out from a standstill in any of the higher gears. (I tried it and applying hold seems to have no effect in "drive" position.)
If it does what you say it probably does (meaning limit it to acting like a three speed manual), all that would do is reinforce my existing problem: remember, my whole complaint is that it is apparently not entering fourth gear substantially until the TC lockup presumably kicks in much later, at 45.
I maintain that when it shifts you should see a substantial drop in RPM. I see the RPM drop for the first two up-shifts into second and third, but not the shift into fourth. Upon deceleration to below 40 MPH, whereupon the TC lockup comes off, it's either back in third gear or maybe a slushy fourth gear that I am unconvinced is working properly. The irregularity is noticeable in that the RPM builds to and stays at over 2000 RPM while gradually accelerating from 25 to 45 MPH. I should be seeing a pronounced drop in RPM somewhere in the 30's if or when it shifts into fourth. But I am seeing no real drop in RPM until 45 MPH.
-
Re: Why an Aveo automatic gets poor city MPG
Sounds like the transmission is operating just fine. The operation described sound perfectly normal. The TCM keeps the engine at somewhat a constant rpm before locking up. I do agree that lockup is occurring pretty late at 45mph. A lower lockup speed would be more desirable, such as 40mph (like more powerful GM transmissions).
For one, I really doubt locking up the torque converter earlier would result in significant fuel economy gains. In the city, where the speed limit is closer to 35mph, the torque converter would still hardly ever be locked up. The power delivery of the car would be less predictable and "drivability" would suffer.
Second, the engine's FE is probably best when the rpm is between a certain range of approximately 1000rpm. My guess is between 2500 and 3600 rpm (Peak torque is at 3600rpm 1st Gen Aveo). Then it would make sense to try to keep the engines rpms within that range by controlling gear change and the torque converter lockup to get the best FE.
A good way to understand and get a grip on what I'm saying is to study CVTs (continuously variable transmissions). The reason why they are getting a lot more popular is because it's easier to control engine's rpms with them. I work with them everyday, not in automobiles unfortunately but in snowmobiles and quads. But the same theory applies.
-
Re: Why an Aveo automatic gets poor city MPG
Quote:
Originally Posted by ontarian_frog
Second, the engine's FE is probably best when the rpm is between a certain range of approximately 1000rpm. My guess is between 2500 and 3600 rpm (Peak torque is at 3600rpm 1st Gen Aveo). Then it would make sense to try to keep the engines rpms within that range by controlling gear change and the torque converter lockup to get the best FE.
I've done RPM vs fuel consumption tests in numerous cars, and have found that without exception in every vehicle I've driven (from a ~50 hp, 3-cylinder Geo Metro up to a 500 hp Corvette), maximum cruising fuel economy happens in top gear at the lowest possible engine RPM.
It's a bit of a myth that best RPM for cruising fuel economy is close to peak torque RPM. I think the confusion may come from people's partial knowledge of brake specific fuel consumption (BSFC) (lowest does happen near the torque peak) ... but which isn't same thing as best fuel economy.
-
Re: Why an Aveo automatic gets poor city MPG
Quote:
I've done RPM vs fuel consumption tests in numerous cars, and have found that without exception in every vehicle I've driven (from a ~50 hp, 3-cylinder Geo Metro up to a 500 hp Corvette), maximum cruising fuel economy happens in top gear at the lowest possible engine RPM.
It's a bit of a myth that best RPM for cruising fuel economy is close to peak torque RPM. I think the confusion may come from people's partial knowledge of brake specific fuel consumption (BSFC) (lowest does happen near the torque peak) ... but which isn't same thing as best fuel economy.
I couldn't agree more; every car I've owned over the past 35 years bears that out.
Here's a current example. I also have an '89 Mitsu Galant - nothing fancy, just a very plain, ordinary, automatic 4-speed with a Jap transaxle. It typically up-shifts at about 10, 20 and 30 MPH (approximately) under moderate acceleration. It goes into fourth gear by 35 MPH at the latest. It's a 2 liter engine, a much bigger car, and it weighs at least as much as the Aveo. My FE in all city driving, even in winter is a consistent, dependable 20 MPG and has been for 20 years ever since I bought it new. But I can feel and hear each shift and also see it shift by watching the tach (although it's not harsh shifting by any means). And it was the same with my '89 Celica which would go into fifth gear by 40 MPH at the latest. :!:
On the Aveo, the best we have been able to manage is 22 MPG - and it seems that no matter how conservatively we drive it, it makes no difference. In fact, the sooner we get it into the higher gears, the better the MPG.
The Aveo is like driving a pail of slush - not because it lacks power, but because it doesn't up-shift appropriately. From what I see of it, Chevy engineering tried to compromise and rig the TCM for power, more than for economy, by having it rev high before TC lockup - but it achieved neither power nor economy. Maybe they thought it would be an acceptable shift strategy for someone who drives long highway distances in a sparsely populated state with little or no traffic. But I live in suburban metropolis. The way this tranny is programmed it will never lug the engine, but it sure does consume more fuel than need be at speeds of under 45 MPH.- and there is no way I can change it. :(
-
Re: Why an Aveo automatic gets poor city MPG
Thyme: have you gone ahead and made contact with GM yet?
-
Re: Why an Aveo automatic gets poor city MPG
Quote:
Originally Posted by MetroMPG
Thyme: have you gone ahead and made contact with GM yet?
Funny you should ask. :roll: I decided it would be best to take it first to my local, friendly, GM dealer if for no other reason than as a formality, to give them a chance to diagnose it. I would expect that if I hadn't, my writing to those higher up in the chain of command would be seen as premature, and automatically kick my complaint back down to a lower level. General Motors has as much top brass at their highest levels than the U.S. Army does. (Maybe that's the "General" part of General Motors?) Accordingly, dealing with a leviathan, top-down, big business structure is very similar to, and can be just as frustrating as dealing with government bureaucracy.
They had the car for most of a day, and they called me back and told me there was a "memory code" set for the accelerator pedal itself, which apparently is an hybrid mechanical + electronic assembly. They want to replace it, so we're waiting for the part to arrive. I have no objection, but I hope they don't turn it into a FUBAR. (My Scantool showed no active codes set, however.)
I spoke with the repair tech and asked him about his road test of the car and inquired about what he found with the shift points. He said everything seemed normal for a three speed transmission. I told him it's a four speed with TC lockup. He disagreed. I smiled diplomatically and left it at that. No point in arguing; but such blatant ignorance destroyed any confidence I might have had in them. Seeing that they lack essential knowledge of what the transmission design is, I get the impression that their replacing the accelerator assembly might only amount to 'grasping at straws' to show they are making some attempt at remediation. Read the code, replace the part, CYA, business as usual. I'm not surprised.
Stay tuned... :roll:
-
Re: Why an Aveo automatic gets poor city MPG
They thought it was a 3-speed? That's disappointing.
I think the last time GM had a 3-speed automatic was in the Metro days.
-
Re: Why an Aveo automatic gets poor city MPG
Unfortunately the good old Metro days are over. I could go on all day about how much better the Metro design is compared to the Aveo. 50 MPG, no shift problems, lightweight, reliable, no timing belt problems...
After their contract with Suzuki expired in 2001, GM basically stepped backward with this car, to the days of the Pontiac LeMans, which was also built by Daewoo. It's De-Evolution... !
-
Re: Why an Aveo automatic gets poor city MPG
Quote:
Originally Posted by MetroAveo
Unfortunately the good old Metro days are over. I could go on all day about how much better the Metro design is compared to the Aveo. 50 MPG, no shift problems, lightweight, reliable, no timing belt problems...
After their contract with Suzuki expired in 2001, GM basically stepped backward with this car, to the days of the Pontiac LeMans, which was also built by Daewoo. It's De-Evolution... !
The last LeMans produced was designed by Opel, built by Daewoo, sold as a Pontiac and loved by no one. That's globalization, GM style.
Just out of curiosity, how much did/does your Metro weigh?
-
Re: Why an Aveo automatic gets poor city MPG
I believe somewhere in the range of 1700-1800 lbs., if I remember correctly.
The Aveo does feel light, though. Especially when I spin the tires on wet pavement at a stoplight! :lol:
-
Re: Why an Aveo automatic gets poor city MPG
Quote:
Originally Posted by MetroAveo
Unfortunately the good old Metro days are over.
But keeping somewhat on topic: the Metro/Firefly/Swift automatic transmissions were a joke. Relative to the manual, they got horrible fuel economy, because they were 3-speeds with no lockup torque converter. Ridiculous agricultural technology, sold right up to 2001.
-
Re: Why an Aveo automatic gets poor city MPG
Quote:
Originally Posted by MetroAveo
I believe somewhere in the range of 1700-1800 lbs., if I remember correctly.
The Aveo does feel light, though. Especially when I spin the tires on wet pavement at a stoplight! :lol:
My 2009 Aveo5 weighs 2557 lbs. My '89 Galant, which is a much larger 4-door sedan with a 2 liter engine, weighs slightly less.
-
Re: Why an Aveo automatic gets poor city MPG
With the crash and safety standards and equipment mandatory of cars today they are heavier unless newer more expensive materials are used. Think about it though passenger compartment "cage" dual air bags side air bags (if equipped) the swept front end crush standards side impact protection. Etc.
-
Re: Why an Aveo automatic gets poor city MPG
The crashworthiness argument is only partially applicable (as an argument for ever increasing weight). EG: the new North American spec Mazda2 / Fiesta weighs in at ~2200 lbs and meets/exceeds all current crash standards.
New cars today are also fitted with a LOT more standard equipment than they used to be. The 1700-1800 lb Metro was a stripped out car with power brakes being the only "powered" option, for example.
Expect automakers to start trimming out the flab (ie. not needed for crash protection) in the coming years for better fuel economy and performance. Several have already announced weight reduction plans across their lineups.
-
Re: Why an Aveo automatic gets poor city MPG
Very true, the Metro automatics were quite pointless for the car's selling point. They didn't get much more mileage than what our Aveos are getting, and they would SCREAM at highway speeds. If you got a Metro, you HAD to have a manual to make it count. [-X
I don't like automatics, anyway. Manuals just make more sense, unless you insist on keeping a hand free to eat a sandwich while driving. Also get this: You can actually choose when to shift into the highest gear! No frustration about the torque lock-up kicking in too late! lol #-o
-
Re: Why an Aveo automatic gets poor city MPG
Quote:
Originally Posted by MetroAveo
Very true, the Metro automatics were quite pointless for the car's selling point. They didn't get much more mileage than what our Aveos are getting, and they would SCREAM at highway speeds. If you got a Metro, you HAD to have a manual to make it count. [-X
I don't like automatics, anyway. Manuals just make more sense, unless you insist on keeping a hand free to eat a sandwich while driving. Also get this: You can actually choose when to shift into the highest gear! No frustration about the torque lock-up kicking in too late! lol #-o
It depends on where you live and the type of driving you do that determines whether a manual or an automatic is best for you. I once had a manual transmission car, and think my clutch wore out by 40K - not from improper shift technique, but because in city traffic constant shifting is an unavoidable necessity. As I mentioned, 95% of my car's usage is in city conditions, not highway driving. So it has nothing to do with eating, not knowing how to clutch or not enjoying shifting; BTW, I never eat or drink anything while driving. When I drive, I focus on driving. :wink:
-
Re: Why an Aveo automatic gets poor city MPG
Here’s an update on my A/T & city fuel economy situation. The Chevy dealer replaced my accelerator pedal assembly. If you recall, they said there was a code set in the memory of the computer indicating it was not within correct spec range. Since I got it back I test drove it and here’s what I found: It now up-shifts a bit sooner into fourth gear – before it wouldn’t up-shift until about 38 MPH, and now it shifts at about 32. The shift into fourth gear feels a bit firmer (less murky) with a more noticeable drop in RPM’s when it shifts. The TPS reading I’m now seeing on my ScanGauge is slightly lower at idle, at about 15-16 TPS instead of 16-17 seen previously. So there is a perceptible difference, and marginally a slight but noticeable improvement in the way it shifts.
A few days before they changed the pedal assembly I took it for a drive on a stretch of highway with no traffic of about 10 miles. I maintained a steady 65 MPH with the A/C on the whole time (it was unseasonably warm here), and the Scan Gauge said I got 37 MPG for that highway portion! Apparently an A/T Aveo gets excellent highway mileage once the TC is in lockup mode – but short of speeds below 45, great fuel economy can’t happen.
I strongly urge anyone with the same murky shifting symptom to take your car to a dealer if it is still under warranty. Your car may have the same problem as mine and the accelerator deficiency may be more widespread than just an isolated case.
It’s too soon to tell with certainty whether our overall MPG improves any. I don’t expect to see much improvement as I’m still feeling a pronounced shift with an RPM drop into TC lockup at about 45. In other words, this probably rectified a relatively minor problem, but not the more prevalent one of the way the shifts are programmed. Unfortunately GM programmed this transaxle to delay TC lockup and treat it like a shift into overdrive. The sad and annoying thing is that there is no overdrive gear on this transmission beyond the actual fourth gear. The programming that delays the converter lockup amounts to fudging an up-shift into lockup mode, treating it as a sort of quasi-overdrive: as such, it is too little, too late. :(