Envy = 2.43 R/S. The four-cylinder I'm building would need 9" rods to do that! 
Why would you want a 2.4 R/S ratio when "everyone" knows that is too high........ 
Obviously we are constrained by other parts and you just have to use what you have to use. I will opine, that if F1 could physically make the rods shorter they would. As it is rod length is required or pistons hit the crank/counterweights or the piston itself would need to be much taller, thereby heavier etc. Although it is clear that there are aspects of engine performance (many but unspecified here) that rod ratio can affect, from a basic horsepower stand point, on a dyno, it is hard to tell any difference at least in peak numbers. A respected builder I know says a "connecting rod" is just that, connects the crank to the piston. Make the piston and ring package what you want and then connect to the crank, rod length be damned. He does not say it makes no difference, but that rod ratio is way down the list of stuff-To quote our respected Fordboy "Hey Mark, what's the ONE thing that really matters when building racing engines? "EVERYTHING." - that you need to be working on, other things are more important. Perhaps Jack Gifford was being factious, I was with my comment about his post.
Anyway, Fordboy hasn't piped up about this topic (recently) so am just poking him with a stick to wake him up. 
he may well feel differently.
OK, the sick bear has been poked awake.
As I understand it, the reason F/1 has rod/stroke ratios so high is because it is a "packaging" issue. Fully counterweighted cranks with short, very light, short pistons and the connecting link has to be 'X'. Since everything else is "tuned" for that geometry, it can be made to work, especially in the rev ranges F/1 uses.
And it is the same with every other design parameter, something else can be "done" to help make it "work". Since there is an almost infinite number of possibilities for geometries, flows, parts motions, etc, my basic design philosophy is this:
1) I want to know what the design's limitations are from the outset, whatever they are. I want to KNOW, not guess, since "packaging" and other issues are going to limit what can be done. I am always keen to know airflow limitations, since the I/C engine is just an air pump.
2) I rate combinations sort of loosely, since it turns out: Everything is a compromise. My labels are: Best, better, poor. Feel free to use my labels or create your own.
3) During the planning/evaluation stage, (the part where no metal is cut) I want to identify which of the original manufacturer's design parameters I'm (more correctly my client) is stuck with. This is the part where I want to eliminate usage of as many of the "poor" choices as I can.
4) Since I don't like to "re-invent the wheel", I identify what I am locked into, and what I can "play with". My goal is always to choose the "best" compromises for the design, something easier said than done. Don't get me wrong, I'd love to have access to Jack Gifford's shop, or Jack Fox's shop, but my machining skills are more limited. And besides, I think I'm much better at data analysis than machining.
So what? Well, some of the things we are stuck with on this "N" engine build are:
not necessarily in any specific order . . . . . .a) Since Rover did NOT build a 1.0 litre we have to reduce displacement to remain in I/GT. Whether or not H/GT is in the cards,
, not my call.
b) Since I don't think Chris wants to pop for special, shorter cam drive belts, or pay ARP for special shorter fasteners, block deck height is "fixed". Although this could change if an unlimited megabucks sponsor could be found.
And there may be other "undiscovered" reasons to retain block height, say room for the water pump . . .
c) Bore diameter reduction does not appear to be an option to reduce displacement. Since the valve spacing pattern is "fixed", there isn't much that can be gained. And since there is likely an airflow penalty to boot, this appears to be a "poor" choice.
d) Since the bore reduction won't work, we are forced to reduce stroke and increase connecting rod length, thereby raising R/S ratio. Since the engine is not going to run F/1 rpms, other compromises will need to be implemented to keep peak torque and peak bhp in the rpm ranges required.
e) Some compromise on cam profiles, cam LCA's will need to be done to balance out the R/S ratio. Can't be avoided for the rev range to be used.
f) Etc, etc . . . .
OK, now I really have a bad headache so I'm off for a nap. Once I finish what I'm working on for the "N", I'll post it up.
I don't want to be critical of anybody else's choices or build plan. This is just the way I do it now. Things tend to work out better if you consider the possibilities, and then make the best or better choices for your build. My results were good before, but have gotten better with enhanced planning. I try really hard to avoid the stupid choices or combos, it helps.
Luck is such a fickle mistress. Half the time she's not home, and you get the Joker . . . . . . . Why do that if you can avoid it?
Thinkyboy
Topic: Milwaukee Midget (Read 3269862 times)