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Car Forum / Driving, Maintenance, Tuning / Maintenance and Repair / June 2007Forcing an *up*shift in an automatic--mpgs
Awl-- Most auto trannies readily allow you to downshift--ie, the gear will go no higher than indicated. No problem. First Q: How is a forced downshift accomplished, from both mechanical and 'pyooter povs? Q 2.: Wouldn't forcing a upshift--ie, the gear will go *no lower* than indicated--be accomplished in approx. the same way? Q3. How would one go about kluging this up? Jumper wires somewhere? A switch? Rod?? How might I pursue actually accomlishing this feat? I had asked this some time ago, and the overall consensus in that thread was that I was asking for trouble, perhaps big trouble, and it sounded pretty convincing. :) But I still don't see why, if we can readily downshift w/ no ill-effect to the car, why we can't just as readily and safely upshift. The reason for these Qs is the following observation: I have noticed that lugging an engine in high gear is *far more efficient* mpg-wise than operating in the normal rpm/power range. Haven't tested the limits, because an auto tranny won't let you, but here is what I observed and how. Bought a mpg meter, a Scangauge, and noticed that in going up a hill, when the tranny shifts down a gear to keep up power in the engine, the mpg's fall immediately and *precipitously*--25-50%! So it appears that rpm drastically affects mpg, so if I'm not in a hurry to get someplace, I'd rather just lug my way there in as high a gear as possible, saving mebbe quite a few scheckels in gas. But, an auto tranny won't let you do this. When I say "lug", I'm not talking about making the engine sputter, but you are clearly below the "sweet spot" in terms of rpm/power. But with surprising increases in fuel economy. I don't think this is bad for the engine, and given the increase in efficiency might even be good for the engine, but I'd like to hear other opinions/reasonings.  Signature------ Mr. P.V.'d (formerly Droll Troll), Yonkers, NY Stop Corruption in Congress & Send the Ultimate Message: Absolutely Vote, but NOT for a Democrat or a Republican. Ending Corruption in Congress is the *Single Best Way* to Materially Improve Your Family's Life. The Solution is so simple--and inexpensive! entropic3.14decay at optonline2.718 dot net; remove pi and e to reply--ie, all d'numbuhs What you want to do will damage the engine and tranny 'and' drink gas. Your idiot light gas meter lies. Your tranny shift is correct. Real life says if the engine is kept in the sweet spot, the mileage is the best. In our Jeep 5 speeds with larger than stock tires, and this works for all that I know have tried it, if we keep our engines in the 2300 rpm sweet spot that they seem to like, I for one get 23 mpg highway pretty consistently. If however we run one gear up all the time which drops the revs to say 1700 at 65 mph, our, mine in particular, gas mileage drops to about 18 mpg. This works the same off road running trails. We 'do' however need what you want, a downshift limiter on the automatics. This can be done electronically on the newer Chrysler Jeep autos, don't know about others. We need it for hill climbing. The autos do fine about 2/3 the way up steep stuff in 2nd, but then they want to jump to 1st. This just spins tires and they are stopped, digging holes. Mike 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's Canadian Off Road Trips Photos: Non members can still view! Jan/06 http://www.imagestation.com/album/pictures.html?id=2115147590 (More Off Road album links at bottom of the view page) > Awl-- > [quoted text clipped - 39 lines] > efficiency might even be good for the engine, but I'd like to hear other > opinions/reasonings. > What you want to do will damage the engine and tranny 'and' drink gas. > > Your idiot light gas meter lies. Your tranny shift is correct. > > Real life says if the engine is kept in the sweet spot, the mileage is > the best. Don't know about now, but years ago (when gas was more expensive than now in real terms), fuel economy "races" were common. It was discovered during these runs that lugging the engine (as in shifting way early and then flooring the gas pedal) did in fact return the best gas mileage. But that was with carbureted cars. I don't know if FI engines would respond the same way. SignatureTegger > It was discovered during these runs that lugging the engine (as in shifting > way early and then flooring the gas pedal) did in fact return the best gas > mileage. > > But that was with carbureted cars. I don't know if FI engines would respond > the same way. Still works the same. The reason behind it is that when the throttle is wide open there's no losses due to the throttle valve. When it's nearly closed, the engine has considerable pumping losses. cu .\\arc >> What you want to do will damage the engine and tranny 'and' drink gas. >> [quoted text clipped - 12 lines] > But that was with carbureted cars. I don't know if FI engines would respond > the same way. Damn, man, I sure wished my carbureted Jeep new about those tests..... I have tall gears and when I use overdrive or 5th gear, I still have power to pull so it isn't 'totally' lugging the engine, but my gas mileage drops at least 5 mpg when I use it.... The places we go camping are 200 miles away so I have lots of chance to try different things out for mileage on the same 200 mile track. Mike 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's Canadian Off Road Trips Photos: Non members can still view! Jan/06 http://www.imagestation.com/album/pictures.html?id=2115147590 (More Off Road album links at bottom of the view page) >>> What you want to do will damage the engine and tranny 'and' drink gas. >>> [quoted text clipped - 28 lines] > Jan/06 http://www.imagestation.com/album/pictures.html?id=2115147590 > (More Off Road album links at bottom of the view page) I'm too lazy to look it up, but I think it was an old PopSci or C&D something where they were talking about this or doing a fuel economy test or something, but an IC engine is most efficient around 80% throttle and as low revs as possible. It is one of those "all other factors being equal" things... FWIW, on my old Jimmy with taller than stock tires, I got better mileage in 4th and mid-throttle than 5th and 90%/full throttle... theory <> reality. I keep track of the mileage in my Trans Am (5.7 V8), Beretta (3.1 V6) and Subaru (2.5L F4) and they all average within 19-22 mpg combined driving. At 100km/h, the Subaru is turning around 2600 rpm, and the TA is turning about 1100 in 6th and probably getting better fuel economy... Ray > >>> What you want to do will damage the engine and tranny 'and' drink gas. > [quoted text clipped - 47 lines] > > Ray It wasn't 80% throttle, but the engine at 80% of output. This means to use this method, the engine has to be undersized so it can run at 80% of full load during cruising. Then, of course, there is little reserve power, which is why this isn't done, except in hybrids. I remember the Popsci article pretty well- it was a full-size, lightened, chain-drive pickup truck with no glass. A smaller engine had been put in, I think. It was green, or was it blue? He also would accellerate at 80% power, then kill the engine and coast. Dave >>>>> What you want to do will damage the engine and tranny 'and' drink gas. >>>>> Your idiot light gas meter lies. Your tranny shift is correct. [quoted text clipped - 49 lines] > > Dave That's a different article than the one I had. The two articles I'm thinking of, one was in C&D where they ran a MPG "race" and used a Suburban as a wind-break, and the other was just a discussion of HP/Torque curves and how it related to fuel economy - basically engine dyno fuel consumption stuff. If I didn't have about 5,000 car magazines I'd know where it was... > > What you want to do will damage the engine and tranny 'and' drink gas. > [quoted text clipped - 15 lines] > -- > Tegger The same thing is true. Further, the danger with lugging is that the carbureted engine would buck, which was hard on the driveline. Further, modern bearing materials and lubricants further reduce damage from high bearing pressures. Today, as long as the engine will still accelerate smoothly, things are okay. One of the European mfgs did a test on this after the first oil embargo, and verified no excessive engine wear from lugging. My new Chrysler mini-van has the shift points too high for good fuel economy. The sweet spot for throttle opening is about half to three quarters open for most engines, BUT, the rpm should be as low as possible. So in my stick shift car I can short shift and get great economy, but the van is auto and is obviously set at a peformance shift point setting. I'd LOVE to find a way to lower shift points. I have tried backing off slightly at an rpm I'd like to shift at, but can't force the upshift. I can force the upshift a bit by backing off, but at an rpm much higher than I would shift a stick at. >> > What you want to do will damage the engine and tranny 'and' drink gas. >> [quoted text clipped - 33 lines] >can't force the upshift. I can force the upshift a bit by backing >off, but at an rpm much higher than I would shift a stick at. These late shift points have always bothered me. I recall when most automatics shifted early and used the engine torque to keep things moving. But even with big engines it seems like the manufacturers started moving their shift points to higher and higher rpm's in the 70's. It would probably mess up the emissions certification but I sure wish the manufacturers let you plug in a "code reader" and set your shift points however you wanted them within some reasonable limits to avoid damage. > These late shift points have always bothered me. I recall when most > automatics shifted early and used the engine torque to keep things [quoted text clipped - 4 lines] > your shift points however you wanted them within some reasonable > limits to avoid damage. This solution has been around for a while. We call it a MANUAL transmission. Ray > This solution has been around for a while. We call it a MANUAL > transmission. > > Ray It WAS around for awhile. Try getting a mini-van with stick shift today. Unavailable! Thankfully they are still available on subcompacts, but the stick shift is, unfortunately, on its way out :-( >> This solution has been around for a while. We call it a MANUAL >> transmission. [quoted text clipped - 6 lines] > Thankfully they are still available on subcompacts, but the stick > shift is, unfortunately, on its way out :-( I know. One of the reasons we bought the Subie was because of that. You can't even barely buy a pickup truck with a stick anymore. Ray 01 Trans Am (6 speed manual) 02 Subaru Legacy (5 speed manual) 90 Chev 1/2 Ton (5 speed manual) :) >>> This solution has been around for a while. We call it a MANUAL >>> transmission. [quoted text clipped - 10 lines] > One of the reasons we bought the Subie was because of that. > You can't even barely buy a pickup truck with a stick anymore. Sticks are fun to drive, but there's something absolutely stone-age about grinding an unlubricated piece of friction material into a metal flywheel to make the car move and then change gears.... especially when replacing that friction material means you have to drop the transmission and (usually) have to re-machine the flywheel. >>>> This solution has been around for a while. We call it a MANUAL >>>> transmission. [quoted text clipped - 16 lines] > replacing that friction material means you have to drop the transmission > and (usually) have to re-machine the flywheel. It's no more stone age than stepping on the brake pedal. It's not like there's any significant slippage or wear in normal operation of the clutch, anyway. nate Signaturereplace "roosters" with "cox" to reply. http://members.cox.net/njnagel >> Sticks are fun to drive, but there's something absolutely stone-age >> about grinding an unlubricated piece of friction material into a metal [quoted text clipped - 5 lines] > there's any significant slippage or wear in normal operation of the > clutch, anyway. Stepping on the brake /is/ stone-age. The very idea that all that energy is dissipated into heat is an affront to any person with sci-tech thinking. A system with 4 electric motors and electro-dynamic braking would be so much better. But they killed the electric car, right? > >> Sticks are fun to drive, but there's something absolutely stone-age > >> about grinding an unlubricated piece of friction material into a metal [quoted text clipped - 10 lines] > thinking. A system with 4 electric motors and electro-dynamic braking > would be so much better. But they killed the electric car, right? "They" haven't killed it, the technology is on the shelf waiting for a nice dense energy storage medium. nate >> Stepping on the brake /is/ stone-age. The very idea that all that >> energy is dissipated into heat is an affront to any person with sci-tech [quoted text clipped - 3 lines] > "They" haven't killed it, the technology is on the shelf waiting for a > nice dense energy storage medium. That too, you have a point. I've always wondered why it's not feasible (if they have actually attempted it) to make a car that works the way diesel locomotives work - a constant-speed engine charges a battery and feeds the motors. The battery can be smaller than for a pure electric car; the engine can be smaller than for a pure mechanical drive car, and more efficient (because of the constant speed); the energy from braking will be regenerated. I'm curious what factors (or combination thereof) make this unfeasible. (Didn't the Honda Prius do something similar, but not quite?) >>> Stepping on the brake /is/ stone-age. The very idea that all that >>> energy is dissipated into heat is an affront to any person with sci-tech [quoted text clipped - 12 lines] > regenerated. I'm curious what factors (or combination thereof) make this > unfeasible. (Didn't the Honda Prius do something similar, but not quite?) Actually, the diesel drives a generator which powers traction motors directly--at least on smaller work-type locomotives, and I'm pretty sure on the big boys as well. The rpm does seem to vary from idel to load, like gas-powered welders. In NYC subways (all electric), regenerative braking far exceeds the friction brakes, ito power. Unfortunately, this regenerative power is bled off through huge resistor banks, and not fed back into batteries (there are none), and not back into the third rail/running rails, because being unregulated it interferes with the trackside signal systems. The Prius has battery-charging regenerative brakes, fwiu. But, pure battery operated vehicles w/ an ancillary generator would seem simple and workable, mebbe w/ some solar roof chargers. Something perhaps a diy-er could do. Yeah, detroit would love dat. Signature------ Mr. P.V.'d (formerly Droll Troll), Yonkers, NY Stop Corruption in Congress & Send the Ultimate Message: Absolutely Vote, but NOT for a Democrat or a Republican. Ending Corruption in Congress is the *Single Best Way* to Materially Improve Your Family's Life. The Solution is so simple--and inexpensive! entropic3.14decay at optonline2.718 dot net; remove pi and e to reply--ie, all d'numbuhs On Jun 5, 9:25 pm, "Proctologically Violated??" <entropic3.14de...@optonline2.718.net> wrote: > >>> Stepping on the brake /is/ stone-age. The very idea that all that > >>> energy is dissipated into heat is an affront to any person with sci-tech [quoted text clipped - 42 lines] > entropic3.14decay at optonline2.718 dot net; remove pi and e to reply--ie, > all d'numbuhs Indeed, MOST Diesels drive the motors directly. However, there are now some hybrid locomotives, designed for yard work where the power cycle is very peaky. These do have batteries, and a smaller engine (or two). > Actually, the diesel drives a generator which powers traction motors > directly--at least on smaller work-type locomotives, and I'm pretty sure on > the big boys as well. Yes, even the 6000-horsepower GEs work that way (the biggest locomotive currently built). > The rpm does seem to vary from idel to load, like gas-powered welders. Not much. Idle on a locomotive diesel is around 400-500 RPM. WFO pumping out all 6000 horses is 900 RPM. >>> Stepping on the brake /is/ stone-age. The very idea that all that >>> energy is dissipated into heat is an affront to any person with sci-tech [quoted text clipped - 8 lines] > the way diesel locomotives work - a constant-speed engine charges a > battery and feeds the motors. That's not how common diesel-electric locomotives work. They don't have any battery in the system, and don't store energy. They do use the electric motors for "dynamic braking," but the current ones just dump the electricity into a big resistor bank and fan- a brake that doesn't wear out, but doesn't recover any energy either. >> Sticks are fun to drive, but there's something absolutely stone-age >> about grinding an unlubricated piece of friction material into a metal [quoted text clipped - 3 lines] > > It's no more stone age than stepping on the brake pedal. True- but hybrids now have regenerative braking. Plus you don't have to drop the transmission to put on new brake pads.... It's not like > there's any significant slippage or wear in normal operation of the > clutch, anyway. Only on break-away from a stop, assuming the driver is competent at operating the clutch... :-/ >>>> This solution has been around for a while. We call it a MANUAL >>>> transmission. [quoted text clipped - 16 lines] > replacing that friction material means you have to drop the transmission > and (usually) have to re-machine the flywheel. Stone age? I prefer to think "race car driver" seeing as how most race cars (except drag racers) use sticks. Hey, when the dinosaurs were around, they ruled. :) > Stone age? > I prefer to think "race car driver" seeing as how most race cars (except > drag racers) use sticks. > > Hey, when the dinosaurs were around, they ruled. :) Heck, my race car doesn't have ANY transmission- a non-shiftable quick change box (no clutch either). Car must be put in gear before pushoff. One can move it OUT of gear with engine running, but not into gear. This is standard with short track oval racing (midgets, sprints, etc). >> Stone age? >> I prefer to think "race car driver" seeing as how most race cars (except [quoted text clipped - 7 lines] > gear. This is standard with short track oval racing (midgets, > sprints, etc). and the irony is that MY race car has an automatic - the rules require it (stock car)... yet the car originally was a stick. If you own a sprint car, how much to let me try it? :) Ray > Stone age? > I prefer to think "race car driver" seeing as how most race cars (except > drag racers) use sticks. Sticks in racing: Formula 1- no IRL- no CART - no NASCAR - yes Rally/hillclimb/etc. - yes Conventional manual transmissions are in the minority even in racing these days. >> Stone age? >> I prefer to think "race car driver" seeing as how most race cars [quoted text clipped - 9 lines] > Conventional manual transmissions are in the minority even in racing > these days. IMO: Clutch = manual transmission, Torque Converter=Automatic. from wikipedia: "Formula One cars use semi-automatic sequential gearboxes with six or seven forward gears and one reverse gear. The driver initiates gear changes using paddles mounted on the back of the steering wheel and electro-hydraulics perform the actual change as well as throttle control. Clutch control is also performed electro-hydraulically except from and to a standstill when the driver must operate the clutch using a lever mounted on the back of the steering wheel. By regulation the cars use rear wheel drive. A modern F1 clutch is a multi-plate carbon design with a diameter of less than four inches (100 mm), weighing less than 2.20 lbs (1 kg) and handling 900 hp (670 kW) or so." from my reading, an IRL or CART car uses a similar type of sequential style gearbox, but it's still got a clutch. How many automatics will you find in Stock Car road racing - SCCA type of stuff? 24 Hours of LeMans? 24 Hours of Daytona? I think that conventional automatics are the minority. Entry level dirt track and bracket drag racing are about the only places you'll see a torque converter. Ray >>> Stone age? >>> I prefer to think "race car driver" seeing as how most race cars [quoted text clipped - 12 lines] > IMO: > Clutch = manual transmission, Torque Converter=Automatic. That's one way to look at it... but on the other hand an electric paddle switch that tells a gearbox to shift up or down a gear without use of the clutch is hardly a "manual" transmission in the conventional sense, and that's exactly what F1, IRL, and CART cars use. At best, its a "manumatic." > from wikipedia: > "Formula One cars use semi-automatic sequential gearboxes What I said. ;-) >>>> Stone age? >>>> I prefer to think "race car driver" seeing as how most race cars [quoted text clipped - 23 lines] > > What I said. ;-) The paddle shifter also controls the clutch in an F1 car. What do you consider a motorbike gearbox then? It's a sequential shift. Ray > >>> This solution has been around for a while. We call it a MANUAL > >>> transmission. [quoted text clipped - 16 lines] > replacing that friction material means you have to drop the transmission > and (usually) have to re-machine the flywheel. But modern clutches are so good now! I used to figure 50K miles on a clutch was good. It has been a long time since I replaced a clutch in a car, and I usually keep them for at least 120-140K miles. Many other things are falling apart on the car before then. Also used to replace throwout bearings- haven't done that in decades! And even when I did have to replace clutch linings, I NEVER had to have the flywheel machined. >> These late shift points have always bothered me. I recall when most >> automatics shifted early and used the engine torque to keep things [quoted text clipped - 9 lines] > >Ray That has nothing to do with the shift settings possible for an automatic. If there was a thread about trying to make the clutch work smoother on a manual transmission would you say "the solution has been around for a while. We call it an AUTOMATIC transmission." >>> These late shift points have always bothered me. I recall when most >>> automatics shifted early and used the engine torque to keep things [quoted text clipped - 13 lines] > smoother on a manual transmission would you say "the solution has been > around for a while. We call it an AUTOMATIC transmission." fine. The solution to your problem has been around for a while. It's called a replacement valve body for your transmission. Frankly, on the cars I've owned, the automatic transmissions do a pretty darn good job of knowing when to shift up and down in regular street driving. Ray >>>> These late shift points have always bothered me. I recall when most >>>> automatics shifted early and used the engine torque to keep things [quoted text clipped - 16 lines] >fine. The solution to your problem has been around for a while. It's >called a replacement valve body for your transmission. Not on a vehicle with electronic computer control of the transmission. The valve body modifications will only change firmness of the shifts. Don www.donsautomotive.com >Frankly, on the cars I've owned, the automatic transmissions do a pretty >darn good job of knowing when to shift up and down in regular street >driving. > >Ray >Awl-- > [quoted text clipped - 10 lines] >Jumper wires somewhere? A switch? Rod?? How might I pursue actually >accomlishing this feat? This is so totally dependent on the type of vehicle that without that information there is no meaningful repsonse. In older automatic transmissions shift points are controlled 100% by mechanical, vacuum and hydraulic methods. The only "computer" is the hydraulic valve body plus a mechanical governor and a vacuum modulator and/or throttle valve. A limited amount could be done to such a transmission by tampering with the governor springs, valve body, throttle valve cable -- or rod -- is so equiped, or installing an adjustable vacuum modulator. On the other hand, my 96 Ford 3/4 ton Powerstroke diesel has a hydraulic valve body that controls shift FIRMNESS only. Shift points are determined 100% by the power control module. Ford has used several different shift strategies for 94-97 Ford Powerstrokes and a change of computer or computer re-flash will change shift points. I went one step further and got a chip with custom programming. I realized an enormous power increase from the chip and my oversize injectors. I sent the chip back for further programming to prevent constant donwshifts from overdrive on the slightest hill -- downshifts that were totally superfluous with the increased torque from the engine. I also told the programmer that I wanted it to hit OD at light throttle at 50 MPH instead of waiting till 60. I wanted the torque convertor to lock up at about 38 mph instead of 45 mph,. I wanted no downshifts until the engine was seriously lugging or I pushed the (fly-by-wire) accelerator to the floor. He told me "no problem" and to just send the chip back if I wanted further tweaking. I heard on the Ford diesel forum that I frequent that, against his better judgment, he programmed a chip for one guy that locked up the torque convertor at 20 mph! Wasn't a good idea and the owner of the truck thought better of it and sent it back to be re-flashed. I have no idea what you are driving so no idea what might be possible. Don www.donsautomotive.com >I had asked this some time ago, and the overall consensus in that thread was >that I was asking for trouble, perhaps big trouble, and it sounded pretty [quoted text clipped - 24 lines] >efficiency might even be good for the engine, but I'd like to hear other >opinions/reasonings. Very interesting. My vehicles are a 04 Nissan Frontier, and an 07 Honda Fit--neither performance vehicles. The idea of getting custom programmed chips is neat. How do you go about doing this? Can you do this yourself, with software, etc.? It might solve the problem, even if the new set point is a little high, as it's always easy to downshift. Even if the setpoints are chip-controlled, tho, ultimately the chip is just sending out a voltage to trigger some event. Is it possible to intercept/supply those voltages to control the shifting? Are multiple events being addressed simultaneously? Signature------ Mr. P.V.'d (formerly Droll Troll), Yonkers, NY Stop Corruption in Congress & Send the Ultimate Message: Absolutely Vote, but NOT for a Democrat or a Republican. Ending Corruption in Congress is the *Single Best Way* to Materially Improve Your Family's Life. The Solution is so simple--and inexpensive! entropic3.14decay at optonline2.718 dot net; remove pi and e to reply--ie, all d'numbuhs >>Awl-- >> [quoted text clipped - 79 lines] >>efficiency might even be good for the engine, but I'd like to hear other >>opinions/reasonings. Sounds like what you want is something like the Porsche Tiptronic transmission. Other manufacturers have their own versions of this. With electronically controlled transmissions, its just a matter of the processor commanding the shifts based on user inputs rather than preprogrammed shift points. If you could figure out which solenoids are opened and closed for each shift, you could probably put together some simple logic to step through the shifts based on driver inputs. You could easily screw something up by mis-shifting. But stick and clutch drivers have had that ability for years. The factory units (Tiptronic and others) incorporate the best of both worlds. You can shift pretty much as you want, but there is still some logic in the loop to prevent really stupid (and expensive) mistakes. Automatic tranny repairs tend to be much more expensive than stick and clutch repairs. I've seen after market engine controllers. I've also seen home-brewed ECMs build by people with extensive automotive and electronics experience. I would think that there would be after market transmission controllers available, particularly for 'sportier' cars (forget about the minivan) which would include manual override functions. There are other reasons to tinker with stock shift points. My Landcruiser has a feature for skipping first gear when starting off on slippery surfaces. SignaturePaul Hovnanian mailto:Paul@Hovnanian.com ------------------------------------------------------------------ This isn't right. This isn't even wrong. -- Wolfgang Pauli |
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