Quote:
Originally Posted by brelandt
Not always so.....Honda engines are internally balanced. Infact the weight difference between all 4 cylinders are less than 1 gram for Hondas.
Unorthodox racing offers a crank only underdrive kit for Honda engines for this very reason. No need for harmonic balancing.
I susbect this to be true with the Saturn that was tested as well?
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Not so. Hondas are internally balanced, but the harmonic balancing is in the crank pulley. W/out it, at a certain high RPM there is a damaging vibration to the engine. This is why underdrive crank pulleys are only recommend on race engines and show cars. If you run an aftermarket crank pulley your first indication comes when you blow out your crank seal. People that understand engines very well know that the crank seal goes bad because the crank is out of balance and the engine is nearing it's end. In fact, if you're ever shopping for a used Honda and you see oil leaking from the crank seal, pass on it!
Only the Civic CX and VX lack a weighted crank pulley. This is due to the fact that the redline is quite low so you never reach the RPM where the damaging harmonic resonance occurs.
An alternative to underdrive pulleys is an electric water pump. You install it inline with your coolant system, drill some small holes in your thermostat housing, and cut the fins off your mechanical water pump. You wire it to a relay that is controlled by ignition power and ideally an aftermarket coolant switch that supplies ground somewhere around 120 degrees F. The EWP removes the mechanical drag on the engine and puts a smaller electrical drag in it's place.
The reason this works is because the EWP is optimized to flow at one particular speed vs the mechanical pump's speed which is governed by RPM. The problem with mechanical pumps is that they don't make enough pressure at low RPMs and at high RPM's, they produce too much pressure and your coolant cavitates. The low end of this problem causes your engine to run hot at idle increasing engine wear and requiring the radiator fan. The high end of this scale produces increased drag on the timing belt costing you power as well as not providing optimal cooling when you need it most.
Like most any engine modification, cost/benefit doesn't make sense from a purely economical standpoint. EWP's will set you back a few hundred dollars assuming you can install it yourself, and the mpg increase is small so it will take many years for it to pay for itself. I recommend this mod only to people like myself who are striving for the combined goal of increasing economy, performance, and engine life.
) on the underdrive question...
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