Fighting the kickdown of an Auto tranny w the SGII!!

[ShadeTreeMech]

While driving my van with the scanguage it occurred to me there may be a guage on it that can help me predict how much more throttle I can give the ole girl without making the transmission downshift. I live in a rather hilly area, so this is info well worth looking for.

After cycling through the guages during a rather boring drive, I realized the LOD gauge is just the ticket. LOD is the measure of the percentage of load on the engine for the current throttle position; or at least that's what I'm pretty sure it is.

Anyway, 99 is as high as it will go. When the LOD guage reads 99, and you press the gas pedal further, it will downshift very soon. But if I keep the LOD reading less than 99, and my speed doesn't drop too much, I can keep it in top gear longer. So I aimed to keep the LOD guage less than 95, and kept the 4000 lb rig from downshifting nearly as much as it usually does.

Doing this I've been able to get my tank average to about 24, compared to my normal average of about 20 (in a vehicle rated to give 17 ) I figured those of you with a scanguage and an auto would be interested in this.

[hmiwb]

I too noticed what you are talking about with the LOD indicator. The mysterious thing in the case of my Ford Escape with 6 speed automatic is that this 99 rule applies when the "cruise control is on". When driving normally without cruise the transmission seems to downshift at just the slightest increase in throttle position. I'm going to do a bit more checking, but it would appear that my transmission computer is going to give better fuel economy while the car is in cruise mode by design.

[rmay635703]

My motor can't physically exceed 40% load, even at wot.

That thing never made much sense to me. Always figured it was almost useless when driving an auto. Also it does take much on some of my vehicles to go into open loop, maybe 70% throttle

[SentraSE-R]

I use LOD to prevent gear kickdown on my wife's 2006 AT Hyundai Elantra. If I keep LOD below 70 on hill climbs, the transmission stays in TC lockup.

[ShadeTreeMech]

Originally Posted by hmiwb

I too noticed what you are talking about with the LOD indicator. The mysterious thing in the case of my Ford Escape with 6 speed automatic is that this 99 rule applies when the "cruise control is on". When driving normally without cruise the transmission seems to downshift at just the slightest increase in throttle position. I'm going to do a bit more checking, but it would appear that my transmission computer is going to give better fuel economy while the car is in cruise mode by design.

I noticed with my Buick LeSabre and Pontiac Transport the cruise control seemed to make the car willing to lug the engine when climbing a hill, as compared to using the foot pedal. Wish there was a way to modify the tranny computer to alter the kickdown throttle position at will. I tried this by adjusting the throttle position sensor on my maxima, but it made the engine run rough, so I put it back. Only modification I can think of is to get another TPS, attach it to the throttle, then hook the harness going to the transmission to the alternate TPS.

IDK, just wish they both were manuals. I hate not being able to tell the car what gear I want it to be in.

[UFO]

LOD = 80 = where my auto downshifts.

[PaleMelanesian]

95 LOD is the mark on my Odyssey.

[abogart]

Originally Posted by rmay635703

My motor can't physically exceed 40% load, even at wot.

Mine does the same thing. With the gear selector in L, above about 20 mph I can put the pedal to the floor and the trans will hold 2nd gear. Technically this should be 100% load (or 99 LOD indicated on the SG) but mine only reads about 40 or so. I think on some older vehicles this reading is a measure of actual torque or HP compared to maximum engine torque or HP at any rpm. So even though the engine is generating as much power as it can at 3000 to 4000 rpm, it would still generate more at wot at the 5600 rpm red line.

I use the MAP reading as a more accurate gauge of engine load. With the engine off, pressure is balanced between the intake manifold and outside atmosphere, reading 14.3 psi (0 MAP is essentially a perfect vacuum). I aim to accelerate to speed at about 10 and cruise at 55 mph is usually 7.0 to 7.2. After the TC locks, about 13.5 will cause it to unlock, which is about 95% actual engine load.

[ShadeTreeMech]

On my vehicles (2 Nissans essentially) the MAP reading doesn't seem to work right. I'm sure things will vary from car to car. I do like the resolution I get with the LOD guage on mine, since it does vary from 10 to 99. I can push it right up to 98 without a downshift, but just a bit more of a squeeze I'll get a guaranteed downshift.

I assume the LOD guage is a calculation of the theroetical load by reading different sensors, but I wonder how it is calculated exactly? My guess is that it has to do with speed, rpms and throttle position, but it will also vary depending on the grade of hill I'm going up (there's a lot of hills in the Ozarks.) So is it the MAP reading that also comes into play when calculating the LOD?

[abogart]

Originally Posted by ShadeTreeMech

So is it the MAP reading that also comes into play when calculating the LOD?

I would think so. The MAP is basically a direct reading of engine load. Here at 628 feet above sea level, the atmospheric pressure is almost always 14.3 psi, which is what the MAP sensor reads with the ignition on and engine stopped. One can draw the conclusion that 14.3 MAP with the engine running would be 100% load. However, I'm not quite sure how the bottom end is calculated. It wouldn't be reasonable to assume that 0 MAP is 0 LOD, because that is a perfect vacuum (and very hard to obtain). Perhaps there is a base value that represents 0 LOD, or maybe the GPH is factored in there as well somehow.