Piston throw weight - to me implies the weight of the piston above the pin which can be "thrown" around as such. At x amount of engine speed, the rotating components way more, alot more infact and at mean piston speed of say 25m/s, the g's on the interals are huge, this would mean that the throw weight of the piston would be alot heavier resulting in a greater force to move this weight, hence the greater force on the upwards motion of the piston. I don't know how the figures, 3x and 2x come about, but that's how I interpret it. Also may have something to do with intertia and resistance to change in direction.
There was a guy on here who pulled out a huge amount of physics related stuff once about rod bolts, what was his username? I think it was string actually.
Thanks for that. I will be using the stock IM / TB initially although I may get the TB bored (or buy a different one depending on price) -- I hear anywhere from 65mm - 70mm being used, with 68mm being most common. The Victor X is meant to produce good results, although the same can be said for a ported ITR IM (with a lot of meat taken out of it).
Are you hinting that even though the head may flow big numbers, I wouldn't have the IM / TB combo to support and that may mean restriction in IM then reduced velocity due to bigger ports etc? (i.e. I understand that
Adrian -- My Stage 1 was to re-use my current bolt-ons as fitted to the DC2R including clutch / flywheel / s300, exhaust / intake etc .. But if there is a 'Necessary' then I have to consider it in stage 1...
Stage 2 would be address bolt ons based on dyno result, restrictions etc ..
Priority is to build the engine -- I can upgrade other parts as I need to.. Just want to get the long block 'right' .. easier to change bolt ons than pistons/rods.. waiting on detailed info about the head as well..
Adrian -- Might give you a call later today if you have 5 mins for me to bounce some thoughts off ..
Priority is to build the engine -- I can upgrade other parts as I need to.. Just want to get the long block 'right' .. easier to change bolt ons than pistons/rods.. waiting on detailed info about the head as well..
this mentality is counter-productive.
the longblock will be 'right' ONLY if it is matched to other components.
Ok so lets talk about the difference between using ported IM/68mmTB/BigTubeHeaders-70mm exhaust on the setup vs stock ITR IM/63?mmTB/
a little off topic ... But a restrictive header or intake would act as a restrictor i.e. limit hp but not torque?? so, theoretically (and maybe this is where i am going all wrong) by using my current bolt ons I would limit peak output to max flow capability of current boltons. so Torque may taper off instead of building at high rpm?
i.e. Can we discuss, what effect on torque curve will restrictive bolt ons create?
Piston throw weight is important at very high rpm
With a high comp b20 vtec piston to head clearence is very small
This is all explained in one of the articles at theoldone.com
Basically they made a fully build b20 rev to 10000 rpm with all the best components rods etc
They found that due to the small clearence that at that speed the rods where actually stretching due to the piston throw weight and the piston smashed into head and rooted the engine on there engine dyno
So if you think about it a small relatively small mass of a piston to have so much force to stretch a high tensile rod
Thats more of a clearance issue though isn't it? I mean, they decked the block in that build with a very fine p2h clearance (or was it p2v?) -- A few more thou and he thinks he would've been ok ... i.e. lesson was to build that stretch into the tolerance..
B20VTEC - since 2002 
Reply With Quote
Originally Posted by ewendc2r
Bookmarks