Toymods Car Club Inc: Tech & Conversions => Increasing Conrod Length

Toymods Car Club
www.toymods.org.au

F.A.Q.

Home

Members

Toymods » Tech & Conversions » Increasing Conrod Length Show: Today's Posts :: Show Polls Email to friend

Author

Topic

humble
Regular

I supported Toymods

Location:
Brisbane, QLD
Registered:
May 2002

Re: Increasing Conrod Length	Mon, 09 February 2004 09:20

Hi guys, Firstly thank you very much for the quick response(s) ShinyBlueSteel: Well, the question was an exercise in extracting information from a larger knowledgebase (which is you guys) for the purpose of my personal education to a greater or lesser extent. Oh yeah and then there is my addiction to "Solutions looking for Problems" Good to see that the engineering community hasn't completely lost their sense of humour! (Turns out real estate agents and accountants already have! Sad sad world we live in) Like Dave explained, the really really good reason(s) for increasing the length of the conrods are; Due to the reduction in the angle the conrod moves through the cylinder: - you can increase the RPM at which the "critical piston speed" is reached (thus we achieve a higher reving motor). - due to resulting reduction in the intertial loading and the pressure on the cylider walls, the motor will tend to increase revs faster (needless to say, frictional losses are reduced). Due to the change in the velocity curve of the moving piston, the piston "spends more time" closer to TDC, i.e. increases the dwell time around TDC thus giving the burning charge more time to act on the piston during the powerstroke. However, the negative effect of this is the consequent reduction in dwell time around the BDC reducing the low RPM breathing ability of the motor. I believe you are wrong when it comes to saying the height of the crank has no effect on the conrod length. With everything else being the same, if you reduce the crank height by a x mm, then the stroke is reduced by a factor of x mm, true. However, the length of the conrod will have to be increased by a factor of x/2 mm to ensure that the compression volume to remain the same (because their is a x/2 mm reduction in radius around the axis of the crackshaft). As for the headgasket are there any disadvantages in this scanario to using the thickest, "robust enough" headgasket (say which has been used in high power super/turbocharged applications to reduce the compression ratio)? Every fraction of a millimeter counts. Once again, thanks for the adive mate. It's highly appreciated. Dave: As always thank you so very much for the quite insightful advice. I would definitely go TRD gudgeon pins and custom pistons with reduced compression height. I'm not thinking JUN stroker kit at all. I'm definitely not looking forward to increasing the stroke I was thinking for the worst case scenario, in case I had to reduce the stroke a little in favour of increasing the rod length, I would need a new crank. I guess increasing the height of the block is unfortunately out of the question As for conrods/pistons do you know anyone who does good custom conrods/pistons? I need the engine to be able to deal with upto 600HP of power (not that I want it for any conceivable reason, just want to build a nicely over-engineered motor that revs to around 9K+ RPM). Cheers Nishad [Report message to a moderator]

[Message index]

-=] Back to Top [=-

Current Time: Sat Aug 2 17:21:36 UTC 2025

Total time taken to generate the page: 0.0054030418395996 seconds

.:: Contact :: Home ::.