Rod:Stroke Ratio

[icyjaws]

i've been reading that 1.75 is like the ideal number for this why is that? Also anyone know what the rod length of the 2zz is? I know the stroke is 85mm. So what's the ratio?

[vvtlikick]

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.

[icyjaws]

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.
thanks

[icyjaws]

ok well i got this off honda-tech doesn't say alot but give a link to another sight. http://www.honda-tech.com/zerothread?id=87340
http://www.theoldone.com/ they said look there

[Chui]

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.

[Jesse IL]

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.

[CIN]

Hmm the 1ZZ rod is 146.65mm. Are you sure the 2ZZ rod is that short(139.7m)?

There is not much on this subject so since I cant find the rod length anywhere I resurrected the thread. Maybe someone can verify this?

[icyjaws]

i got that from messuring it as close as i could (center to center) I would figure the 1zz rods would have to be shorter since trial put a 1zz crank and rods in a 2zz. right?

[CIN]

Thats what I figured too but the 1ZZ rod length comes from the 1ZZ technical paper.

[icyjaws]

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.

[CIN]

And if it has a r/s ratio of 1.76 than the engine can be made to go to insane revs. :D

Also do you have any other tech papers on the 1zz/2zz than the ones posted?

Oh the 1ZZ rod length is on the 1ZZpdf that you also have. ;)

[CIN]

Oh the pdfs are the ones that are on matrixvibe. :)

[icyjaws]

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.

[CIN]

I think that I have them. They where about the high power honda engines right?

Thanks anyway :)

So nobody knows for sure the length of the stock con rods??

[Griffin]

Stroke on the 2ZZ is 85mm on the 1ZZ it's 91.5mm

Bore on the 2ZZ is 82mm on the 1ZZ it's 79mm

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.

[CIN]

I agree. But I still do not think that the 2ZZ rod could be shorter than the 1ZZ. Would be a better idea if they made a longer rod I think.

[CIN]

So anyone found some info on the 2ZZ rods??

[icyjaws]

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.

[GotNos]

so can i increase the the length of my rods on the gt?

[CIN]

Hmm so this should leave two alternatives. Either the block was shortened or the pistons on the 2ZZ have a lower attachment point to the rod.

If the case is the second one, it should not be a problem to correct it once the engine is preperd for high revs. I hope they did not shorten the block.

It is strange though. With a shorter stroke and a highercompression the rods would normally be longer.

[CIN]

BTW can you give me the emial to contact crower? ;)

[kaioshin]

www.crower.com

tech@crower.com

[CIN]

thx :)

[kaioshin]

n/p!

Any new info?

[CIN]

I sent them an email. When I get anything I will post it here :)

[westrock]

I'm bringing this back from the dead to update the information about the rod lengths. Crower has numbers for both the 1ZZ and 2ZZ published. (http://www.crower.com/pdf/157-172.pdf)


...................C-to-C..............B.E. Bore....B.E. Thick.....P.E. Bore...P.E. Thick
1ZZ......5.770" (146.558mm).....1.850"..........0.780".........0.787"......0.780"

2ZZ......5.433" (137.998mm).....1.890"..........0.780".........0.787"......0.780"


C-to-C: Center to Center distance, middle of the big bore to middle of the piston bore, basically the center of both rotating points.

B.E. Bore: How big the crankshaft end is bored ("Big End")

B.E. Thick: I'm assuming how thick the actual metal is on the sides, between the two "flat" sides.

P.E. Bore: Same as B.E Bore just up on the smaller end where the piston is

P.E. Thick: Same as B.E. Thick, meaning these connecting rods are the same thickness from top to bottom.


2ZZ Rod Ratio: 1.62 (137.998mm rod / 85mm stroke)

1ZZ Rod Ratio: 1.60 (146.558mm rod / 91.5mm stroke)

Which is a good compromise of high RPM wearability and power producing. Generally you want the lowest rod ratio that will work within your RPM range in order to make the most power. Going to a higher rod ratio will make things more kosher as far as the hardware is concerned, but can take a power loss because of the geometry of the piston movement.

Next we will need the connecting rod length of the stroker kits to see what the new ratio is on them.