3sgte 4th Options

[timdog1720]

is the 4th gen 3sgte a strong engine...better power over the others?

[Cuts_the_Pilot]

Crank and pistons are the same, rods are made of cheese, so no they are weaker.

[timdog1720]

ok so why does it have more power????

Crank and pistons are the same, rods are made of cheese, so no they are weaker.

[cax_11]

ok so why does it have more power????

Crank and pistons are the same, rods are made of cheese, so no they are weaker.

Higher compression pistons

[delusionz]

ok so why does it have more power????

Crank and pistons are the same, rods are made of cheese, so no they are weaker.

Higher compression pistons

head.

alll 3s are 1998cc

no engine comes with pistons higher than the deck unless its a custom stroker build and someone f*cked up the measurements and didnt check before ordering custom pistons.

[cax_11]

Check this site out if you don't agree http://en.wikipedia.org/wiki/Toyota_3S-GTE_engine
it possible that the head also helps with this power increase, but the 4th gen compression ratio is 9.0:1 where the 3rd gen is 8.5:1

[delusionz]

What I mean is that it's the head that makes it high compression, not the pistons.

All 3s-gte are 1998cc (499.5cc per cylender)

499.5cc / 8.5 = 58.76cc (per head chamber)

499.5cc / 9.0 = 55.5cc (per head chamber)

You see? Since the bore and stroke are always the same (86mm x 86mm), if the compression was raised using taller pistons it would take a different bore and stroke to achieve 1998cc

This is just to give you an idea, Pi * R2 * H obviously doesnt factor in piston crown and head shape, and piston ring recess, but you get the gist of it.

[azian_advanced]

actually, taller pistons cangive you the higher compression ratio while still maintaining the same bore and stroke and therefore displacement assuming both pent-roof head designs are the same.
i just did the math and it worked out for me. the end result turned out to be that the 4th gen pistons are 0.717 mm taller than the 3rd gen pistons.

This post has been edited by azian_advanced: Apr 22, 2011 - 3:03 PM

[Cuts_the_Pilot]

Pistons are the same between 3rd and 4th, check toyodiy if you dont believe me.

There is debate if the rods are different, some places state the same part numbers, but i know people who have snapped rods on 4th gen 3s-gte, taken appart and confirmed smaller rods.

This post has been edited by Cuts_the_Pilot: Apr 22, 2011 - 8:16 PM

[azian_advanced]

if the pistons are the same, then the 4th gen rods must be longer. it doesn't make sense for them to be shorter while having higher compression ratios.

unless the pent-roof shape of the head is shallower in the 4th gen.

[timdog1720]

wow I started a good convo....

[Cuts_the_Pilot]

Just heared from a reliable source that they are the same as beams 3s-ge rods.

change is in the head.

[delusionz]

If pistons were taller using the same bore and stroke you would have higher compression but less cc's.

1998cc and 86mm*86mm seems to be consistent throughout all 3s-* motors.

[easternpiro1]

WOW... im late...

Pistons are the same between 3rd and 4th, check toyodiy if you dont believe me.

There is debate if the rods are different, some places state the same part numbers, but i know people who have snapped rods on 4th gen 3s-gte, taken appart and confirmed smaller rods.

i heard this also... (probably from you cuts?) i can personally say that the rods are the weak point in the 4th gen. Ive had 2 of them blow, both cases a rod was thrown. i got pics of it somewhere in here (the rod was twisted like a tornado) and the piston was pulverized to look like little bits of gravel.

the 2nd blown one cracked a piston, couldnt see far down enough to assess rod damage.

[azian_advanced]

If pistons were taller using the same bore and stroke you would have higher compression but less cc's.

1998cc and 86mm*86mm seems to be consistent throughout all 3s-* motors.

the bore and stroke is what determines the cc's. the volume between the top of the piston at TDC and head have nothing to do with it. you can verify it by doing this:

π * [(8.6cm/2)^2] * 8.6cm * 4 cylinders = 1998 cc's

taller pistons (or longer rods) will just shift the stroke closer to the head resulting in higher compression but won't affect its cc's.

[PhoenixTech]

WOW... im late...

Pistons are the same between 3rd and 4th, check toyodiy if you dont believe me.

There is debate if the rods are different, some places state the same part numbers, but i know people who have snapped rods on 4th gen 3s-gte, taken appart and confirmed smaller rods.

i heard this also... (probably from you cuts?) i can personally say that the rods are the weak point in the 4th gen. Ive had 2 of them blow, both cases a rod was thrown. i got pics of it somewhere in here (the rod was twisted like a tornado) and the piston was pulverized to look like little bits of gravel.

the 2nd blown one cracked a piston, couldnt see far down enough to assess rod damage.

lol, there wasn't any rod left

[easternpiro1]

WOW... im late...

Pistons are the same between 3rd and 4th, check toyodiy if you dont believe me.

There is debate if the rods are different, some places state the same part numbers, but i know people who have snapped rods on 4th gen 3s-gte, taken appart and confirmed smaller rods.

i heard this also... (probably from you cuts?) i can personally say that the rods are the weak point in the 4th gen. Ive had 2 of them blow, both cases a rod was thrown. i got pics of it somewhere in here (the rod was twisted like a tornado) and the piston was pulverized to look like little bits of gravel.

the 2nd blown one cracked a piston, couldnt see far down enough to assess rod damage.

lol, there wasn't any rod left

there you have it folks! i didnt think there was lmao!

moral of the story: 4th gen rods are indeed cheese! (as cuts would say)

This post has been edited by easternpiro1: May 6, 2011 - 4:16 PM

[brenton1919]

WOW... im late...

Pistons are the same between 3rd and 4th, check toyodiy if you dont believe me.

There is debate if the rods are different, some places state the same part numbers, but i know people who have snapped rods on 4th gen 3s-gte, taken appart and confirmed smaller rods.

i heard this also... (probably from you cuts?) i can personally say that the rods are the weak point in the 4th gen. Ive had 2 of them blow, both cases a rod was thrown. i got pics of it somewhere in here (the rod was twisted like a tornado) and the piston was pulverized to look like little bits of gravel.

the 2nd blown one cracked a piston, couldnt see far down enough to assess rod damage.

lol, there wasn't any rod left

there you have it folks! i didnt think there was lmao!

moral of the story: 4th gen rods are indeed cheese! (as cuts would say)

i bet they were trying to make them lighter and for got to make them stronger haha

[Smaay]

actually, taller pistons cangive you the higher compression ratio while still maintaining the same bore and stroke and therefore displacement assuming both pent-roof head designs are the same.
i just did the math and it worked out for me. the end result turned out to be that the 4th gen pistons are 0.717 mm taller than the 3rd gen pistons.

you are correct. look at the Supra 2JZ-GTE and 2JZ-GE, they are both 3 liters, have the same bore and stroke, even have the same crank and rods. the GE has a higher comp piston than the GTE. the heads have NOTHING to do with compression ratio

If pistons were taller using the same bore and stroke you would have higher compression but less cc's.

1998cc and 86mm*86mm seems to be consistent throughout all 3s-* motors.

the bore and stroke is what determines the cc's. the volume between the top of the piston at TDC and head have nothing to do with it. you can verify it by doing this:

π * [(8.6cm/2)^2] * 8.6cm * 4 cylinders = 1998 cc's

taller pistons (or longer rods) will just shift the stroke closer to the head resulting in higher compression but won't affect its cc's.

you are right and wrong. shifting the stroke so the piston gets closer to the head means that it will travel farther away which increases displacement. thats exactly how you stroke the 2ZZ to 1.94L, you use the 1ZZ crank.

[azian_advanced]

well what i meant was the locations of the pistons at TDC and BDC will shift closer to the head, so the length of the stroke remains the same. but yeah, the crank is what determines the length of the stroke.

[Neon90424]

Theres a guy that has a sick ST215 down here...As the mod list started to grow and the PSI started to climb..first thing to go were the rods...pretty much blew a hole through the block...

[delusionz]

But didn't we already confirm Gen 3 and 4 use same pistons?

I read in the MR2 power primer also that depending on which head you get, you'll have less cc's in a gen 2 and 4 head than a gen 3 head. due to the 8.8 and 9.0 CR vs 8.5 and that compression was totally based upon the starting average head chamber capacities whether or not you've had the head skimmed, they say you may lose up to 5cc in each head chambers with a head skim/resurface

then they have big graphs showing what kind of CR to expect.

Why you guys still arguing this?

[azian_advanced]

initially i was just stating that taller pistons will affect the compression ratio w/o affecting the total volumetric displacement of the engine (1998cc) assuming both heads are the same. now that we know the rods and pistons are the same, then the difference is definitely in the head design. i believe Smaay's post about how head design having no effect on the CR is incorrect. by altering the head chamber, it will also alter the volume of the head chamber at TDC which also alters the CR. just to clarify, factors that affect the CR are the pistons, rods, crank (which alters the stroke), and even head gasket thickness. however, the total volumetric displacement of the engine (1998cc) remains unchanged as long as the bore and stroke remain unchanged.

delusionz, you're absolutely right in that you can have different cc's when using different generation heads. but just to be clear, the primer is referring to cc's as the volume in the head chamber, not the total volumetric displacement (1998 cc).

[delusionz]

Yeah you're actually right about that,

moving the so called top of the deck into the head area vs the new (slightly higher) piston BDC level will keep 1998cc if you look at it that way.

but yeah pistons are one way to raise compression as is a head skim, either way the pistons shouldn't be sticking out (not talking about the crown) above the top of the deck in factory form regardless of the generation

This post has been edited by delusionz: May 8, 2011 - 5:16 AM

[paul52]

you are right.

the volume of the air/fuel when the piston is on TDC is called "death volume" and its remains compressed on the head.

CV:cilinder volume 499.5562141cc
DV:death volume

CR= 1 + CV/DV

-for 3rd gen CR=8.5

8.5=1+ 499.55/DV ---> DV=66.6076cc

-for 4th gen CR= 9.0

9.0=1+499.55/DV' ----> DV'=62.4446cc

so death volume on heads are different.

[3WayStunna]

While browsing the MR2 forums, there was also interesting discussion about how the GEN 4/5 oil pumps are higher flowing. Even more so than the 5sfe pumps.
Just my .02 cents. lol

This post has been edited by 3WayStunna: Jun 9, 2011 - 11:57 PM