I'm interested in knowing the rod length and rod ratio for the 2ZZ, too.
I don't know why someone would think 1.75:1 would be the ideal ratio, my understanding is that longer rods, compared to the stroke, are always beneficial for smoothness/friction reduction/etc. This is especially true for high revving engines.
ok well i got the length of our Rods 5.5 inchs i think measured it from center to center makes sense right. Ok well that give us a 139.7 mm rod (1in=25.4mm). For a ratio of 1.6435. So i still don't know what that means. Reason i ask this question to bring with is to get some insight to how far i can stroke this motor. I was thinking 6mm which would give a ratio of ~1.469 is that too much. Come on guys i know there are guys here who noe this stuff.
The longer the conrod to stroke ratio the longer the piston dwells at TDC [top dead center]. This allows for better combustion and slightly more work to be done on the piston face due to the slightly longer stay at or near TDC. There is also a decrease in the amount of side loading on the piston which, in fact, does decrease friction to some extent. How much I do not know.
Rod/Stroke Ratio, often called just rod ratio, is mostly important for the reasons Chui said. Another big factor is how the ratio affects piston speed and more importantly piston acceleration. A longer rod will sweep out a smaller angle as it rocks back and forth, so the rods make less extreme angles (this is why there is less side loading on the cylinder walls). The pistons in an engine with a bigger rod ratio will have lower maximum accelerations. When you accelerate things too quickly, you can actually shatter the pistons. F1 cars and motorcycles actually run rod/stroke ratios up to around 2.4:1. This is one of the reasons they can run such extremely high rpm.
well like said thats just what i could meassure w/ just a SAE ruller and the rods that i have laying around. If you got 146.65mm for the 1zz out of a tech paper i would figure the 2zz should be 3.25mm longer. But none of the papers i have are specific. They just say "the the stroke was shortened by 6.5mm" If we understand that to mean the rods were lengthend 3.25 then that would give 149.9 mm rod length and r/s of 1.76 and the 1zz would be 1.60.
1.76 would make for a very "revable" engine i have a couple papers the chui gave several of us like 2 yrs ago. None scanded or anything. I think only one is on the celica but i would be happy to forward the info on any of it if someone hasn't allready post or sent it to you.
That still leaves rod length as an unknown, and I feel it is NOT safe to assume that the change in stroke was brought on by a change in rod length. The crankshaft was changed and compression increased so the one does not necessarily follow the other. Aside from measuring, I'd not venture to guess.
well i measured it again as close as i can and got 140 mm. If you want i can send it to you and you could messure it yourself or you can try calling crower since they make them for the 2zz they should deff know the dimsions.