I bought a used bottom end supposedly from a scrapped out '01 SRX. Once I got it I looked at the serial number and doubted it was a true SRX bottom end. It had an 8DW prefix but the guy assured me it was from an SRX. So yesterday I pulled the cases apart and there was a Viper crank as I suspected. I'm wondering just how much difference in engine performance there would be with the lighter crank? I'm having an SRX crank repaired now with a new rod but am unsure if I should sell the Viper one or just use it. I've read there would be a difference in the torque of the engine but would it be enough to notice?
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8DW is a correct prefix for SRX, specifically for the SRX700 w/ Ohlins model. Not able to comment much on any power or torque difference as I've never directly compared the two in a controlled environment, I wouldn't expect there to be much difference though. Seems like there has been some conversation about it on here over the years, maybe a search would provide some info.
Mac
Member
Sorry no difference with respect to Torque or HP with a lighter or heavier crank. Torque & hp relate to the efficiency of a combustion event. The crank changes neither of those two numbers. Run the Viper crank and it will rev quicker.
---mac---
---mac---
Yamitriple
Member
You would think more rotating mass would produce more torque but I'm no engineer. I know longer stroke makes more torque
Mac
Member
Some engineering principals just seem to make sense but do not from engineering point of view. This question is just not one of those. Torque is the measure of an engines ability to perform work. The heavier crank does not increase or decrease anything related to combustion. Rotating mass has nothing to do with HP or Torque. The extra crank weight is considered stored energy. In a drag race situation where you will want the crank to rev to its limit the fastest you should always choose the lightest crank.
Now if we were discussing a dirt bike where we may want to lug the engine..... or slow down and tame wheel spin..... we could take advantage of the stored energy we may want a heavier crank or flywheel.
---mac--
Now if we were discussing a dirt bike where we may want to lug the engine..... or slow down and tame wheel spin..... we could take advantage of the stored energy we may want a heavier crank or flywheel.
---mac--
Thanks for all the input guys.I searched an online parts place but couldn't get any hits on the 8DW prefix for whatever reason,but the cases definitely had a Viper crank in it.I'll be using one of my soon to be repaired SRX cranks when I reassemble the base as I found a little too much slop in one of the bearings beside the labyrinth seal.I'd say the engine I got the base from had a piston go out as there was some metal flakes coming out from around the bearing and seal.Not sure if I'll just pop the rods off for spares or sell the crank as is but that\s a decision for later.