There are some reports through the years of Tundra owners with 4.7 V8 engines reporting engine slap. How come there are no reports of this with 100 series or LX470's? Only difference I can see is that the LC/LX engines are built in Japan and the Tundra/Sequoia's are built in USA??
Piston Slap
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think you answered your own question 
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I would agree with my logic but when they first started building Tundra's in the USA they didn't have the engine plant built yet so they imported the engines from Japan. Now I don't know the date that the engine plant was built in the USA and when the piston slap complaints started. But it does seem strange that there are no complaints of engine slap on this site (and if this happened I know one of you would bitch about it) and no posts on the Lexus site or the 4th generation 4runner site.
It's possible that since the Tundra is the "full-size" pickup then some folks assume it's rated like an F-450 and load it down too much whereas with any of the other vehicles its less likely to get the same abuse. (I have overloaded both and readily admit it though) It's much easier to overload a pickup and not feel bad about it than it is a SUV. More room for palettes of stuff like windsor wall stone from Lowe's. (Not that anyone would ever do that hehe) With my Tundra there was no behavior to give me a clue of it acting up; smooth as silk like the Lexus, with less sound deadening.
Just a shot in the dark though.
Just a shot in the dark though.
I would suspect the increased insulation under hood and inner/outer firewall on the LC vs. Tundra may silence the noise
Pistons rock as they cross TDC where the thrust load from the rod angularity shifts from one side to the other. This makes noise. Harmless, but it is the source of piston slap in most all situations.
To prevent this, pistons are designed with long, tapered, flexible skirts so that they can be fitted very tight in the bores when the bore and piston is cold. The taper of the skirt and flexibility of the skirt then prevents scuffing when the piston is hot. Also, the piston pin in OEM production pistons is always offset to one side....it is NOT in the middle of the piston. By offsetting the pin in the piston, artificial thrust load is created to control the piston "rocking" as it crosses over TDC.
Unfortunately, all of the above control techniques, common in past model engines to the extreme, create excess piston mass, cause friction and cost power and fuel economy. With the desire to build in as much power and free-revving capability and to improve fuel economy as much as possible thru friction reduction these design features are pushed in the other direction on modern engines.
Piston pin offset has been reduced over the years to a bare minimum today to reduce the thrust load generated and reduce friction. Pistons have been lightened up considerably by shortening the skirts. This creates less rotating/reciprocating mass which is good for power, free revving capability and fuel economy. Light weight pistons are great but the skirts, by necessity, are short making it hard to make them both strong and flexible and the shorter ckirts make them more prone to rocking.
Unfortunately, when the performance or fuel economy oriented pistons are run cold they are very prone to "slap" until they warm up to operating temperature.
The piston designers and development engineers are always treading the fine line between piston slap cold and friction and power/fuel economy loss when the engine is warm.
It is possible that you are hearing piston noise from an engine that is on the "high limit" for piston clearance so that it makes some noise cold. The good news is that the condition is harmless and that engine is probably a little more powerful (due to less friction) than a "quiet" counterpart. The bad news is that...it makes noise cold.
To prevent this, pistons are designed with long, tapered, flexible skirts so that they can be fitted very tight in the bores when the bore and piston is cold. The taper of the skirt and flexibility of the skirt then prevents scuffing when the piston is hot. Also, the piston pin in OEM production pistons is always offset to one side....it is NOT in the middle of the piston. By offsetting the pin in the piston, artificial thrust load is created to control the piston "rocking" as it crosses over TDC.
Unfortunately, all of the above control techniques, common in past model engines to the extreme, create excess piston mass, cause friction and cost power and fuel economy. With the desire to build in as much power and free-revving capability and to improve fuel economy as much as possible thru friction reduction these design features are pushed in the other direction on modern engines.
Piston pin offset has been reduced over the years to a bare minimum today to reduce the thrust load generated and reduce friction. Pistons have been lightened up considerably by shortening the skirts. This creates less rotating/reciprocating mass which is good for power, free revving capability and fuel economy. Light weight pistons are great but the skirts, by necessity, are short making it hard to make them both strong and flexible and the shorter ckirts make them more prone to rocking.
Unfortunately, when the performance or fuel economy oriented pistons are run cold they are very prone to "slap" until they warm up to operating temperature.
The piston designers and development engineers are always treading the fine line between piston slap cold and friction and power/fuel economy loss when the engine is warm.
It is possible that you are hearing piston noise from an engine that is on the "high limit" for piston clearance so that it makes some noise cold. The good news is that the condition is harmless and that engine is probably a little more powerful (due to less friction) than a "quiet" counterpart. The bad news is that...it makes noise cold.
SWUtah said:
Perhaps the "high limit" for the piston clearance specification is different for Tundra destined engines than than for those headed to the Lexus and LC lines. Or the whole range could have been moved as a power to smoothness tradeoff.
On the original 4.7s from Japan they may have actually speced pistons and then seperated them out for Lexus and Toyota products with those closer to the ideal spec going into the Lexus models. When Lexus was first introduced they used that as a selling point.
The # of complaints probably has much more to do with the volume differences. They sell 10Xs the Tundras as LCs. And once a problem is identified everyone notices it (see our Transfer case vibrations) and feels it needs fixed even if its barely noticable.
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NMuzj100 said:
Tundra engines are made now in the USA. I think it started several years ago. Who knows, if I had one that slapped I would just drive it until it died to see how long it would go. I bet its the 10x's numbers game or it could be a calibration issue with the machine that makes the pistons, getting out of spec after so many pistons and then being recalibrated. If it was a total design issue they would all have this issue versus 1 in 10K+
