Chip control of auto transmission shift points?

I highly doubt any dealer would install an engine blowing chip. Most engines and trannies for that matter too do not like to be lugged. Things break when that happens. Gas mileage goes to crap when you lug it too.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 'New' frame in the works for '08. Some Canadian Bush Trip and Build Photos:

Simple solution - get a car with a manual transmission and shift exactly when you want, and get better mileage too if you're good at it.

Unfortunately, the choices are limited these days. Two years ago we bought a minivan. None were available with manual. So, we have our first automatic minivan- and the gas milage IS attrocious :-(

I'm not talking about installing anything additional. I'm basically asking *how the shift points are controlled*, and if they can then be adjusted, particularly in delaying downshifts.

It also depends on what "lug" means. I'm not talking about lugging the engine until it sputters and smokes. And, since everything is slower and lower doing this, I think mechanical wear would not be an issue.

Lastly, mpgs drop drastically when the engine downshifts. I know this from a scangauge installed on my pickup. The engine certainly "feels better", say, when going up a hill, and the tranny naturally drops down a gear, but the mpg's drop 30% as well.

This is one reason mpg's in city driving are so bad.

Indeed, AND manual's are generally cheaper, as well!!

But, NYC is one of the last places you want to drive a stick, and the wife won't learn it either.

Even if I can't do anything about this, I'm generally curious as to how shift points are controlled in a modern automatic. Or an old automatic, for that matter!

I looked around a bit about this, but don't have your answer. Looks like they dropped "manual mode" for the '08 Accord. Seems like a "manual mode" is the best way to play with best mpg if you have an auto trans.. Otherwise a manual trans. An auto trans is a complicated beast and it's not very likely to find aftermarket mods that are worth while, but I sure could be wrong. Low rpm torque is part of the picture, and might give the pushrod an advantage here. Seems my Lumina 3.1 locks up the torque converter at @30. My Corsica 2.2 locked it at a bit slower mph - before the converter failed and I unplugged it. That Corsica got me 34mpg highway the only time I did a few hundred mile trip with it. I thing the low rpm torque is why the common pushrod GM mid-size cars get such good highway mileage. Recent Vettes put in a switch to bypass lower gears at a certain mph/rpm to increase CAFE ratings, but there was a lot of torque to play with on the 350. The total engine/trans control packages seem pretty darn complicated nowadays, and as you said "feel" is part of the engineering that goes into the design. With the "new" emphasis on mileage, I expect some of the design will go away from "feel" and toward fuel efficiency. I'd be interested you know what you find.

--Vic

Plugging honda transmission shift control into google gets some interesting stuff. Anytime I start reading about auto trans internals now I tend to get real sleepy. But I used to find it pretty entertaining.

--Vic

My move to larger and larger trucks was driven in part by the requirement to have a real (manual) transmission. Fortunately my peak cargo needs also increased so the trend was not unreasonable.

The Honda Fit gets 46+ mpg highway, 25 in "city" driving -- not anything like NYC midtown stop and go, either. Quite a disparity.

My pyooter skills rival my auto transmisssion skills, but wiki had an interesting article

-------------------- As engine computers (ECM) became more capable, much of the logic built into the transmission's valve body was offloaded to the ECM. (Some manufacturers use a separate computer dedicated to the transmission but sharing information with the engine management computer.) In this case, solenoids turned on and off by the computer control shift patterns and gear ratios, rather than the spring-loaded valves in the valve body. This allows for more precise control of shift points, shift quality, lower shift times, and (on some newer cars) semi-automatic control, where the driver tells the computer when to shift. The result is an impressive combination of efficiency and smoothness. Some computers even identify the driver's style and adapt to best suit it.

------------------------

This is sorta what I thought.

So, if I knew what wires went to what solenoids (and the logic therein), I could conceivably lock them in/out manually.

And presumably these chips are programmable ito of shift points/patterns.

Also inneresting:

-----------

ZF Friedrichshafen AG and BMW were responsible for introducing the first six-speed (the ZF 6HP26 in the 2002 BMW E65 7-Series). Mercedes-Benz's

7G-Tronic was the first seven-speed in 2003, with Toyota Motor Company introducing an 8-speed in 2007 on the Lexus LS 460. Mercedes-Benz unveiled a conventional automatic transmission with the torque converter replaced with a lock-up clutch called the AMG SPEEDSHIFT MCT.[2]

-----------------

Go Toyota!!

My friend dragged two small automatic transmissions (junked) over to my place, and we took one apart. *Unbelievably complicated*.

You become grateful that the price tag shown on the car isn't for the transmission alone!!

I've driven a manual in NYC a number of times without ill effects. On the second part you may have more of a problem.

Modern is pretty much solenoid valves to control the selection.

Old was insanely complicated and problem prone all hydraulic controls.

I suspect with a modern computer controlled automatic, you could convert it into a clutchless manual without too much effort by taking control of the solenoid valves and the TCC lockup solenoid.

From your lips to god's ears!

I googled Vic's search terms, and came up with some honda tuner groups. These guys would probably know specific details, assuming they're not laughing too hard at my Honda Fit.

If I knew what electrical block went to the AT, I could proly sleuth out the solenoid logic by just checking voltages whilst driving -- or comparing to D1, D2, D3, etc.

What is a TCC lockup solenoid, what does it do? If I were to try and sleuth this solenoid stuff out on my own, what basic booboos and no-nos should I watch out for, in terms of switching logic, etc?

Indeed, pyooters apparently greatly simplified the control workings of ATs.

It is torque load that explodes stuff. That is why most owners manuals say to lock out (do not use) top gear or Overdrive when climbing hills or towing. Check yours. Folks can and do blow the tranny gears to pieces, literally.

Scanners are only sold to make mechanics money by giving lots of 'misleading' and averaging info.

You are going up a hill. That burns more gas. Simple eh.

I can tell you for sure that lugging an engine in too high a gear drinks way more gas than running with no load on it. In my Jeep and my friends Jeeps with oversized tires and 'mileage' gears, so we are comparing a carb and FI engines (actually several Jeepers I know have tried this with the same results), we get about 5 mpg 'better' running in 4th gear at 65 mph at 2300 rpm that we get running the same route to our camping area in 5th or OD running 65 mph at 1750 rpm.

The 1750 rpm is lugging our engines. No smoke or anything. Sure we still have 'pull', but it takes too much on the gas pedal to adjust for little slopes or wind where the lower gear only takes a twitch on the gas pedal.

Not really. You have to be always on the gas pedal accelerating and on the brake decelerating in the city. This burns gas and wears out brakes.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 'New' frame in the works for '08. Some Canadian Bush Trip and Build Photos:

This is the main area where hybrids or electrics have an advantage - In city driving they recover some of the breaking energy, and they also minimize the use of conventional friction brakes.

During the "first" fuel crisis in the late 70s, one of the European mfgs did a study. They drove one of their cars around the test track for many thousands of miles, lugging it drastically. Then, they tore it apart and looked for undo wear, and found none.

Their conclusions, which agreed with many others at that time, was that modern metallurgy, mfging technology, design techniques, and in particular, better lubricants, had greatly reduced problem of lugging.

The recommendation was that as long as the car would accelerate without pinging and without vibration, you were not hurting anything, but were increasing fuel economy.

Drive train vibrations due to shuddering were very harmful, but FI in particular lately, has largely eliminated shuddering with low rpm acceleration. As long as it will accelerate SMOOTHLY, that shift point rpm is okay.

I wonder why all the owners manuals say to not lug the car in overdrive by using it on hills or when towing?

I also must then wonder why so many folks physically blow the overdrive gear to pieces while doing this because they think they get better mileage with low rpm's...

Maybe they made 'better' transmissions in 1970? Or they just plain didn't have these overdrive gears maybe? Or could all these owners manuals just be wrong?

Oh well, to each their own. I personally have done my mileage testing many times over the same 200 km route over a 20 year period and I know 'I' get better gas mileage when I don't lug my engine so I will continue to follow my owners manual and drive where my engine seems to like it.

The OP should try it. He should keep a record of a route he uses and the mileage used when he lugs along or up the hills like he wants to do and when he drives with a little gas pedal response in the lower gear.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 'New' frame in the works for '08. Some Canadian Bush Trip and Build Photos:

I agree with everything you say. But, I wouldn't conclude that modern technology made it all possible. Between WWII and the mid seventies nobody cared much about fuel economy. High speed performance was the main design consideration. In the 30's there were car engines made that could lug down to

200-300 rpm. And they got good fuel economy (it was the depression people cared about economy more than performance). Some of the farm tractors from 60 years ago also get pretty good economy. I have a neighbor with an old fergusson tractor that he says can drive to town and back (about 30 miles) on less than a gallon of gas. He's probably doing 25 mph at around 1000 RPM. Any engine that is properly tuned is going to get better mileage at the lowest speed it can run smoothly. Lugging can cause damage if it causes the engine to knock or if the oil pump is worn out, but otherwise it won't do any harm.

-jim

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HEAT is the problem. The way most OD systems operate running them under high loads causes heat build-up.

I didn't know there even was such a thing as overdrive these days. On front wheel drive vehicles there is no meaning- there is ALWAYS a gear between the through-shaft and the axle. So what does the term "overdrive" mean on a front wheel drive vehicle. With five speed manuals so prevailant, there doesn't seem to be a need, either.