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Discussion Starter · #2 · (Edited)
harmonic balancer is only found mostly on V8 engine, especially cross plane v8, why ? Because its low tech engine with very long crank that can’t be blue print & balance perfectly. so they added an external balancer as a band aid fix to cancel out the vibrations…

honda inline 4 engines DO NOT use harmonic balancer (I should say all inline 4 engine), that’s a fact, we use standard crank pulley for our belt driven Accessories to power the water pump, alternator, air con, power steering (9th gen use electric power steering) .

do inline 4 engine have vibrations? Yes, k-series def have internal engine vibrations, and we have 2 types of vibrations, a primary & secondary, not going into details but if your interested, you can purchase the research paper through SAE if your interested.

to cancel out primary vibration, you add counter weight on the crank, that’s it, it’s that simple & not so scary, because all honda cranks have counter weight, just make sure when you build your motor, spend the money to have the crank (stock or aftermarket ) balance it before install.

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to cancel out secondary vibrations, if the engine is 2000cc or smaller, the secondary vibrations are minimal & with honda’s supreme engineering, it’s not need it at all, if the engine is 2000cc or larger, you use balance shaft oil pump to cancel out the secondary vibrations…. Balance shaft oil pump is located directly under the crank, it’s why when you hear crank pulley argument about engine balance, people will argue back Honda engine it’s internally balanced, why ? Now you know…

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Discussion Starter · #3 ·
k20, like dc5, fd2, they do not equip with balance shaft oil pump, however on Fa5 (k20z3) it’s equip with balance shaft oil pump like all k24…. I’m not going to further discuss about balance shaft delete & type s oil pump conversion, I’ll leave it to another topic…

so, now you know, why running underdrive pulley is perfectly safe, aslong as your engine is 1) inline 4 2) flat 4 3) flat 6, you can run light weight pulley and single mass light weight flywheel with no problem

i will not recommend light weight pulley on 1) cross plane v8 2) flat plane v8 3) inline 6 4) v6
 

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Discussion Starter · #4 · (Edited)
How underdrive pulley makes power ?

Engine accessories cause parasitic drag, it robs engine output away, it’s why when the ac is on, the car feels more sluggish, the alternator is charging, its creating drags…m

when you upgrade ANY things that rotates (wheels, rotors, flywheel, cams, tires, pulley) to lighter weight, it’s reduces load, on pulley, it helps crank use less energy to spin the whole accessories, it’s the same effect on the other side of the crank, when you install light weight flywheel, it’s free up so much weight and now the crank have much less weight that drags everything down..

So, when you have light weight pulley or flywheel or both, the rpm can move much faster, you can hit peak power at a much faster rate… why do you think I can dyno 198whp @ 7000rpm with no hondata/tune or catless dp ? it’s not magic, it’s all largely because of underdrive pulley kit & ram air…
 

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Discussion Starter · #5 · (Edited)
What’s the difference between oem size vs underdrive?

So now you have read everything and fully understand it, you’re shopping for pulley kit, and you’re going to say different types of kit, stock size or underdrive, what’s the difference?

Stock size can only benefit what I wrote earlier, lighten up the load, it will free up around 7-8hp on an 2400cc engine…

Underdrive is a smaller pulley than stock, what it does is it reduce the usage of the accessories just enough to free up around additional 5hp on a k24.

“Underdrive pulleys increase engine output by reducing the draw of the engine's accessories by slowing them down and reducing the horsepower (HP) they use.”

Pulley is also one of the most discreet mod for adding power, no issues with vehicle inspections & smog check, it makes a lot of power for the price your paying… and when you purchase the fkx racing packaged pulley kit, not only your gonna gain alot of power, your also gonna reach redline much faster especially if you tune to 8000rpm redline.. and the most important thing is, the car have less vibrations & the engine will actually running more smooth than stock… we have installed pulley since 1997 and I honestly was very surprised with all the wrong information post it on the forum 10-15yrs ago… who ever started to spread the false rumors must not understand the basic engineering of an engine, and does not know the difference between a v8 versus an inline 4.
 
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