Is anyone else on the fence due to the engine choice?

[serchmarc]

wtf?

[NESW20]

Originally Posted by serchmarc

wtf?

longer rods = better rod:stroke ratio = easier to tune

[Midship Runabout]

Originally Posted by NESW20

longer rods = better rod:stroke ratio = easier to tune

That dude has the belief that posts like that actually contribute to the forum.

[NESW20]

my bad, haha.

[Dimman]

Originally Posted by NESW20

my bad, haha.

Not you I think. Rod:Stroke ratio stuff is informative. Spitting out nothing but smilies, not so much.

[Abflug]

Originally Posted by smokeynyc

I own a JDM swapped 3SGTE MR2 and an Impreza, I drive both very frequently and to be honest theres not much of a difference in terms of the butt dyno. Both are very torquey motors and the powerband hits nice and early. Compared to my old RSX-S, I really like the low to mid range power band that the turbo motors get instead of a higher revving NA motor. Thank god they didn't castrate this car like they did with the MR2 Gen 3. Either way the EJ20 is a VERY easy motor to get power out of and the only thing its really lacking right now is direct injection, which Toyota is going fix. Lets hope for version 7 EJ207 forged internals!!!! For you guys that don't know the EJ207 spec C(STI version 7 and 8) had a 8300RPM redline.

[Midship Runabout]

Originally Posted by Dimman

Not you I think. Rod:Stroke ratio stuff is informative. Spitting out nothing but smilies, not so much.

Ya I wasnt talking about you NESW20, Talking about dude that posted above you.

[NESW20]

I know. I was saying "my bad" to actually taking him seriously and giving a real reply, but I'm glad you guys got benefit out of it!

i guess the best way i can explain it is that with a better rod:stroke ratio, the pistons have more "dwell" at the top of their travel which allows the charge to cool slightly before ignition, so you can run more timing and make more power. something like that, haha.

[bigbcraig]

I can't imagine the geometry of a couple millimeters really having much of an effect...
When you increase rod length, you're decreasing cylinder volume (even though stroke, thus "displacement" is the same). So while you can play more with the gas and air you can get in, does it really still end up more effective than before with more combustible volume, but perhaps harder tuning?

I'm curious, don't know the answer so if anyone is well-qualified, please clarify for me.

[Dimman]

Originally Posted by bigbcraig

I can't imagine the geometry of a couple millimeters really having much of an effect...
When you increase rod length, you're decreasing cylinder volume (even though stroke, thus "displacement" is the same). So while you can play more with the gas and air you can get in, does it really still end up more effective than before with more combustible volume, but perhaps harder tuning?

I'm curious, don't know the answer so if anyone is well-qualified, please clarify for me.

All I know about this is that V8 engine builders can debate pros and cons of rod:stroke ratios until the cows come home. That's all I can do really, just point you to the direction of the pros.

[Midship Runabout]

Originally Posted by bigbcraig

I can't imagine the geometry of a couple millimeters really having much of an effect...

Oh but it does, on pretty much everything.

[NESW20]

Originally Posted by bigbcraig

I can't imagine the geometry of a couple millimeters really having much of an effect...
When you increase rod length, you're decreasing cylinder volume (even though stroke, thus "displacement" is the same). So while you can play more with the gas and air you can get in, does it really still end up more effective than before with more combustible volume, but perhaps harder tuning?

I'm curious, don't know the answer so if anyone is well-qualified, please clarify for me.

you can't actually (in most cases) just put longer rods in. the pistons would hit the cylinder head. i'm mostly talking about when the block was engineered. they make the block a little bit taller, put longer rods in, and leave the stroke/bore/CR/etc all the same. apparently the "ideal" ratio is 2:1 or thereabouts.

there would be no change in the amount of intake charge let into the cylinder on the intake stroke. it would not be compressed any more or less, only at a slightly different rate at a slightly different time. it could be the difference between running 17 degrees of timing safely and running 20 degrees of timing safely (just throwing out numbers).

[bigbcraig]

Originally Posted by NESW20

you can't actually (in most cases) just put longer rods in. the pistons would hit the cylinder head. i'm mostly talking about when the block was engineered. they make the block a little bit taller, put longer rods in, and leave the stroke/bore/CR/etc all the same. apparently the "ideal" ratio is 2:1 or thereabouts.

there would be no change in the amount of intake charge let into the cylinder on the intake stroke. it would not be compressed any more or less, only at a slightly different rate at a slightly different time. it could be the difference between running 17 degrees of timing safely and running 20 degrees of timing safely (just throwing out numbers).

OK... I absolutely see this, but the original comment was about fitting few-millimeter longer rods into an engine, not a from-scratch engine design.

I still don't see how longer than stock rods could help - maybe rods and a spacer? But still, seems like a low-impact, high-effort mod.

[Dimman]

Originally Posted by bigbcraig

OK... I absolutely see this, but the original comment was about fitting few-millimeter longer rods into an engine, not a from-scratch engine design.

I still don't see how longer than stock rods could help - maybe rods and a spacer? But still, seems like a low-impact, high-effort mod.

I don't quite follow what you mean by a spacer.

Like I said it's pretty common with the V8 guys. But we're talking about 'get-everything-you-can-out-of-the-motor' builds. But for them it's just a matter of picking a length when changing out stock rods, maybe matching it to the piston and whatever deck height the block is getting milled to when they do their bottom end. No more effort than a standard rebuild.

Also if you look at everything available for small block Chevys they have a bunch of different rod types, materials, lengths and weights available all for a single stroke length. Often from a single manufacturer. It's pretty crazy.

As an import guy, I get rather envious of the VAST selection of parts these guys have available (and usually cheaper for a domestic set of 8 than for an import set of 6!).