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The LS400 uses a taut throttle cable between throttle body and gas pedal thereby transmitting vibrations to the lightweight plastic gas pedal...much like tin can string phones.
To attenuate this (very slight) vibration, I removed the gas pedal and filled the backside lattice pockets with 1 pound of molten lead, barstock, Eastwood P.N. 20483.
Noticeable difference.
I cut the lead bar into short segment and used a large soup spoon with a vice grips to molten consistecy over the stove. Using heavy long sleeve shirt and cooking gloves to protect and manage the molten lead. Safety goggles are also necessary..
Following are pictures of before and after. I acquired a spare gas pedal in case issues developed, but the pedal did not distort or melt from the molten lead....
It did however lose the age-related bow and now is pefectly flat.
face down on a flat surface.
Image of original gas pedal backside...depicting lattice pockets
It further dampens vibration coming up through the floor pan via the gas pedal ball & socket hinge which is affixed directly to the body.
More than a few individuals have slathered their floorpans with 100 pounds + of so-called sound deadener, yet ignored contact points...such as feet or hands
It further dampens vibration coming up through the floor pan via the gas pedal ball & socket hinge which is affixed directly to the body.
More than a few individuals have slathered their floorpans with 100 pounds + of so-called sound deadener, yet ignored contact points...such as feet or hands
Lol, that would be most likely due to the fact that sound deadener is for acoustic enhancements and not OCD NVH elimination... That and it's probably a problem with stress on your throttle cable causing your issue, not an inherent LS400 issue... I have never seen nor heard anyone complain about the gas pedal vibrations before.
Also, by adding weight to your pedal you could be ever so slightly opening the throttle and adding additional stress to the pivot assembly.
Lol, that would be most likely due to the fact that sound deadener is for acoustic enhancements and not OCD NVH elimination... That and it's probably a problem with stress on your throttle cable causing your issue, not an inherent LS400 issue... I have never seen nor heard anyone complain about the gas pedal vibrations before.
Also, by adding weight to your pedal you could be ever so slightly opening the throttle and adding additional stress to the pivot assembly.
So perhaps we can agree that sound attenuation, vibration dampening is design dependent. Later LS models use considerably more and selectively applied.
Not sure how a pound of Lead is going to add stress to the pivot assembly...feet weigh consderably more..and vary by footwear. Moreover, drivers apply different actuation force to the gas pedal which, plausibly, Toyota engineers have taken into account.
Cable adhustment is not an issue here. When the throttle cable is actuated, it becomes taut, becoming a conduit for engine vibration...(hence the string phone analogy- sound vibrations only transmit through the string when taut...).even when in perfect tune....not to mention road and exhaust vibration transmitted up from the floorpan through a lightweight gas pedal. Mercedes at one point used a series of rods, bushings, weights and brackets at right angles to each other from the accelerator to engine to dissipate this vibration. Much more expensive than a simple throttle cable...why? Lexus did many things well, but using a throttle cable was not the optimum solution. You may recall that one of the methods Lexus used to gain market share was price. Of course with contemporary drive by wire the issue has become moot. I suppose guessing is OK, but have not heard that anyone commenting has performed this modification, but I report a more solid feel at the gas pedal and engine and road isolation.
Adding mass to anything acts as a dampener. Nothing amazing about that.
That's 1st year engineering.
The load the pedal is designed to experience would be in a single plane through the path of pedal travel. The pedal experiences general forces in the X,Y and Z directions in proportion to the mass of the pedal and it's distance from the pivot. The mass of the pedal is probably around, what, maybe 50-100g (guess, unless you weighed the pedal before and after) and adding 455g of lead has substantially increased that mass.
Now this increase in mass could have zero impact, a long term degradation or cause a failure. It is impossible to know which as these cars are 16-26 years old now. Plastic and rubber deteriorate and weaken over time.
Have you sat down and run through the force calculations, added an age/fatigue/wear factor and compared to original? While the weight in question seems relatively insignificant, you maybe have increased the mass of the pedal by a factor of 5 or more, and that will have a noted impact on the number of cycles that part can now handle before failure.
I'm guessing not.
Which is simply why I suggested you note that you could be placing extra stress on the pivot.
You have also added localized heat to a plastic piece inducing heat fatigue into a part not designed for it. Plastic gets exceptionally brittle when heat, more so for old plastic. You could also be looking at a scenario where you pedal breaks off at the upper edge of your lead addition... What that could lead to is for anyone to guess at.
To be clear, I'm not suggesting what you have done won't work or doesn't work or isn't a great idea.
Simply there are things you have obviously not accounted for and thus should be aware of so you can be on the look out for.
As I can see melted plastic around the larger puddle of lead, the breaking off of the pedal seems like the most glaring and immediate concern for me.
But I'm only an engineer and master tech..... What could I possible know, right?
Somehow I don't see this being overly kind to the throttle return spring. Be aware that if that fails your motor will peg at max RPM.
You've basically put a small brick on the pedal. Luckily it's evenly spaced throughout the pedal so it hopefully shouldn't increase the actual load on the cable anywhere near enough to start moving it.
Somehow I don't see this being overly kind to the throttle return spring. Be aware that if that fails your motor will peg at max RPM.
You've basically put a small brick on the pedal. Luckily it's evenly spaced throughout the pedal so it hopefully shouldn't increase the actual load on the cable anywhere near enough to start moving it.
Off idle the spring mechanism easily pivots the pedal on the floor mounted ball and socket hinge capably returning it to full upright position. While added wieight is primarily at lower and middle sections, the throttle position return spring is more than up to the task due the leverage it exerts at the top of the pedal. Indeed this would be an improper application of weight were the pedal base not directly hinged to the floor...as is the case with suspended pedal (such as the brake pedal!) where additional weight ( although a brick is heavier than one pound) could cause stress on the return mechanism so understand your concerns here. I recall Mercedes expended considerable efforts with expensive accelerator linkage engine vibration isolation mechanisms, incuding a rubber pedal cover. I see that effort and am dismayed when a luxury brand is using such a lightweight pedal coupled to an accelerator cable. Perhaps a pound of Lead, where half a pound or say a third of a pound would suffice, is overkill, but it sure feels rock solid.
An update on the gas pedal vibration fix...despite adding a pound of Lead to the pedal...after 3 years the throttle assembly in the 1999 LS400 works flawlessly...
I drove a friends 2000 LS400 and could feel the slight vibration (normal) in the pedal (mounted rigidly to body floor panel it transmits vibration from floor), where mine exhibits none.
i always disliked the throttle response on the LS, very slow, just as it was intended however.
this must have changed the way the car accelerates and how the pedal is depressed, just like a counterweight shift **** helps with shifting gears!
i always disliked the throttle response on the LS, very slow, just as it was intended however.
this must have changed the way the car accelerates and how the pedal is depressed, just like a counterweight shift **** helps with shifting gears!
....it does not improve vehicle acceleration...
The purpose of adding mass (Lead) to the accelerator pedal and mounting base is to isolate vibration coming up through the pedal from the floor pan and the accelerator cable...
If I jack up the car in the back, then as the car is always going downhill will improve mpg? LOL
12-31-15, 12:12 PM
Lead foot
