Tom-Guy

I'd doubt anything you read on the internet about what a lesser bike's limit is. Look at who the bike's target audience is, look at their budget, look at the sort of ability that comes with that sort of budget.

What I've been doing for the last couple years when I judge rods is look at the revlimit they are rated to. The biggest force a rod undergoes is the tensile load... where the piston tries to continue through the cylinder hear at TDC and the rod has to completely change it's direction. To put this into terms you'd understand, a stock GSR undergoes as much tensile loading at revlimit as it undergoes compressive loading - when combustion pressure pushes on the rod via the piston - with 400 whp. Notice how the better tuners can get 350 whp daily driven out of a stock GSR bottom end. There is no coincidence there.

Ninja 250 has a 62mm slug going 14K rpms. I daresay I could google piston weight, calculate tensile loading at revlimit, drop the loading by 25% for safety, apply that figure to compressive loading, and the figures would be at or around around 100 whp.



Yah, being able to spin the engine to a bazillion rpms literally means there is no time for detonation to set in unless you have fuel or timing horribly, horribly off. Johnny would know this if he had read his Ricardo, read his Vizard, read his Glassman, or had any experience tuning to draw correlations. It's annoying arguing with someone who's never tuned a car and thinks it's cake when I'm six years deep and still learning. I gave up, there was no point to it.

Inquisition

This is not going to work. You will need FEA to get any sort of accurate analysis of the stresses found in the rod. I really wouldn't trust simple math with a rod. If you are really interested in doing this, I'll take some pictures of the pages of my materials text book so you can at least give it a fair shot at the simple math method, but honestly whatever numbers you get I wouldn't trust very much. Piston force will be something you will be able to get a relatively accurate number for, but the fact that the cross sectional area varies across the rod and there are a number of different points on the rod that will have variations of stress based on the design, it will be really hard to get any solid data. Again, FEA will be the way to do things. The best way to look at the whole situation is, Ninja engines are ~$300 so if you throw a rod through one, who cares?

FEA Rod Analysis: http://forums.evans-tuning.com/viewt...358&highlight=

bigdaddyvtec

CRX

Tom-Guy

What a bunch of horseshit.

In the real world, the great majority of fancy math can be bypassed with rough and sleazy seat of the pants approximations.

That's a better way of looking at it.

Inquisition

I'd agree with the sleazy BS math for the most part, but with an engine rod as small as that one is, any slight differences in area can result in large changes in numbers. Remember you will also need to calculate the stresses faced by the rod bolts as they could just as easily be the point of failure. Also knowing the materials actual tolerances as far as strength and modulus of elasticity will play a big role in getting accurate calculations. Again, it can be done by hand but FEA would be a lot more convincing assuming the numbers you punch in are correct.

J-SMITH69

500whp not out of a stock hayabusa engine.

most stock hayabusa engines make ~250whp

Random Hero

Your an idiot johnny. Its bone stock.

Tom-Guy

Rod bolts are strained by tensile loads, and there are several 500whp stock engine turbo 'busas I've seen writeups on.

J-SMITH69

really? thats pretty cool

link?

bigdaddyvtec

local guy......

seen it out at pacific raceway.