ok, first off...this is just an idea, i doubt i'll do it simply because of the cost of the custom pistons and rods but its just busy work, and food for thought.

its all in the rod ratio.


the rod ratio is the measurement of the length of the rods (srt = 5.94" or 151mm) vs. the length of the engine's stroke (srt = 3.98" or 101mm). rod ratio is found by dividing the length of the rod by the length of the stroke. so the stock 2.4L SRT block in this case has a rod ratio of about 1.5:1, which is quite bad. a lot of all out drag 4 cylinders have a rod ratio of no less than 1.8:1. the distance the piston actually moves down the bore is figured by the stroke of the crank alone. both the speed, and the acceleration of the piston are formed by the rod ratio. the reason for changing the rod ratio is this: it has to do with how the rod moves as the crankshaft turns...a longer rod will have a smaller angle of defelction than a shorter rod at the same stroke. not noticeable when half way between TDC and BDC. the smaller the angle, the less the rod has to rotate on the axis of the wristpin, and more force from the piston is applied downward on the crank, so more torque. the piston acceleration and speed have obvious effects on performance of an engine, faster piston acceleration puts more strain on the main and rod bearings and limits the bottom end's rpm limit (maybe thats why the srt-4's redline is so low)

so, on to the point of all this: can i use a longer rod to decrease piston acceleration, and by doing that, will i build a bottom end capable of handling higher rpms reliably? lets see...

the answer is somewhat discouraging.

this is what i was thinking...extend the rod in the 2.4L from 151mm to 159mm, i have some excel tables that show piston speed at any crank angle, it really only matters at 0 though. it shows slight drop in acceleration and also holds the piston at TDC for longer. the acceleration is only brought down by about 1.0% after all the work to lengthen the rod. these results arent what i expected, even with a rod ratio of 1.8 the redline wouldnt be significantly raised. however, according to this 1.0%...if the prevous redline on it was say 6500, now it can be about 6565, woopty do.

stock 151mm:



long rod 159mm:



depending on the application, its not worth all this effort. (at least on the basis of a higher redline) there are however other reasons for a longer rod.

a rod thats longer will always reduce side wall loading, which is one reason why long rods are thought of.



longer rods also cause the piston to 'dwell' longer at top dead center which can work with combustion pressure to produce more work on the crank, more torque at a given crank angle (i.e- 90) this is all relative of course to how much combustion force is on the piston, but im just keeping it constant. this is all needless on a boosted motor, just turn up the boost. but thats not the point, im bored and i need to do something lol. ok. finishing up

the only way to find the ideal rod length (or rod ratio) is if the exact combustion pressure known as to where the piston is. some people actually prefer shorter rods on v8 apps because of the fact that most torque will be made when the crank force and the combustion force curve on teh graphs have the same shape, leaning more toward the TDC side, it makes sense to want the force curve towards top dead center because on a typical high perf engine, the last 70 degrees about of the power stroke doesnt directly contribute to torque. knowing the combustion pressure is not easy to come by...and its even harder because this combustion pressure depends on where the piston is. afterall, ignition occurs before TDC and peak cylinder pressures occure slightly after TDC, but not before. and as much as i'd love to be inside my engine :P i cant be. i think it basically comes down to trial and error. which sucks, but its just something to think about.




PLEASE feel free to correct anything i might be confused on or anything, any and ALL input is awesome :thumbsup


p.s- happy 4/20 ;)










_________
96 talon esi-t
san clemente, ca


as needles of ice
are the ill winds' talons
the coldest of shadows
they seep unto the bone

silent souls leave .308 holes

Originally posted by turbo8u
ok, first off...this is just an idea, i doubt i'll do it simply because of the cost of the custom pistons and rods but its just busy work, and food for thought. its all in the rod ratio. the rod ratio is the measurement of the length of the rods (srt = 5.94" or 151mm) vs. the length of the engine's stroke (srt = 3.98" or 101mm). rod ratio is found by dividing the length of the rod by the length of the stroke. so the stock 2.4L SRT block in this case has a rod ratio of about 1.5:1, which is quite bad...

Maybe, the only thing its bad for is whether or not there is enough room in the block but good because deflection is decreased. The only problem over squre engines incure is the rods ability to stay attatched to the crank and the pistons speeds. The speeds are so great that at low rpms dwell is ridiculous which is why they create such nice TQ down low, similar effect is seen in OHV motors but mostly TQ is made from dwell, slow air velocity and accurate combustion which occurs from slow (not weak) breathing motors

Originally posted by turbo8u...a lot of all out drag 4 cylinders have a rod ratio of no less than 1.8:1. the distance the piston actually moves down the bore is figured by the stroke of the crank alone. both the speed, and the acceleration of the piston are formed by the rod ratio. the reason for changing the rod ratio is this: it has to do with how the rod moves as the crankshaft turns...a longer rod will have a smaller angle of defelction than a shorter rod at the same stroke. not noticeable when half way between TDC and BDC. the smaller the angle, the less the rod has to rotate on the axis of the wristpin, and more force from the piston is applied downward on the crank, so more torque...

with the application of rod ratio for the 2.4L the end results would be the difference of maybe a couple pounds of boost, tops. The Law of diminishing return will hit hard in this area

Originally posted by turbo8u...
longer rods also cause the piston to 'dwell' longer at top dead center which can work with combustion pressure to produce more work on the crank, more torque at a given crank angle (i.e- 90) this is all relative of course to how much combustion force is on the piston, but im just keeping it constant...

Dwell only works in favor of engine with great potential or rod deflection such as the 420a where deflection is greater than just about any motor on the market BUT this enables dwell towards TDC which will NOT make more TQ but HP since at higher pistons speeds the magical 5252 will limit TQ ability from creating HP

Dwell does only one thing, allow good combustion, so these fast pistons speeds decrease volumetric efficiency

Originally posted by turbo8u...this is all needless on a boosted motor, just turn up the boost. but thats not the point, im bored and i need to do something lol. ok...

I too am bored,

but prefer the long rod so long as the rod caps will hold which they do on our car

Originally posted by Skrilla
so fast pistons speeds decrease volumetric efficiency

ding ding ding

increasing the pistons dwell time at TDC increases the amount of time that the valves can stay open, which increases VE

edit: someone NEEDS to do an NA 2.4L...brian?



_________
96 talon esi-t
san clemente, ca


as needles of ice
are the ill winds' talons
the coldest of shadows
they seep unto the bone

silent souls leave .308 holes

Why didn't you post this in the long rod thread in the advanced forum? Seems to have some good info in there.

Originally posted by Uberingram
Why didn't you post this in the long rod thread in the advanced forum? Seems to have some good info in there.

i saw it after i posted this, i just replied to that one with a link to this one though



_________
96 talon esi-t
san clemente, ca


as needles of ice
are the ill winds' talons
the coldest of shadows
they seep unto the bone

silent souls leave .308 holes

Originally posted by turbo8u

Originally posted by Uberingram Why didn't you post this in the long rod thread in the advanced forum? Seems to have some good info in there.

i saw it after i posted this, i just replied to that one with a link to this one though

w3rd to your mother.

talkin to cheesefrog....he was givin me some dank ideas

"Hmm a 101mm stroke and 151mm rod length. 1.49 ratio... that explains the low redline. Would be cool if you could raise the head about 20mm with a deckplate and correspondingly longer rods and get that RS ratio to around 1.69. Then you could spin to 10k without having to worry about throwing a rod through the side of the cylinder wall"

}(
_________
96 talon esi-t
san clemente, ca


as needles of ice
are the ill winds' talons
the coldest of shadows
they seep unto the bone

silent souls leave .308 holes

Well, if you want a longer rod, feel free to use a deck plate and either sleeve the block or lower the top ring. I, myself, however, would probably destroke the crank a little bit. Higher RPMs allow bor better use of gearing.

That being said, I'm a hypocrite. I am using a motor with an iffy (at best) rod:stroke ratio, and a LOOOOOOOONG stroke. Hell, I like torque.

Since I like torque, I also don't mind a shorter rod. It will suck harder from 10* until 90*, and less hard from 90* to BDC. Furthermore, while you can take your dwell time at TDC, I'll take my dwell time at BDC. Why? So I can open my exhaust valve earlier. Also, the intake valves can close a bit later without pumping cylinder air back into the intake manifold. Lastly, and this is the best part, the mechanical advantage of a short rod over the crank journal is much greater then that of a long rod. At the cost of more cylinder side loading, more torque can be had. If the motor is made out of decent materials, I wouldn't worry too much about cylinder wall erosion or piston sideskirt erosion. Especially with the Moly coating on the skirt of the SRT-4 pistons.

Besides... What marque of motor is the paragon of high-revving? Yeah, Honduhs. A B16 has a rod:stroke ratio of 1.52, and some Honda motors have a 1.48 rod:stroke ratio! I think that the stroke is what does the revlimit on the SRT-4 the most damage. If you want the 2.4L motor to rev higher, I think you are just going to need to destroke the crank.

Now, is it possible that the Honduh blocks can rev so high because of their flimsy open deck/unlocated sleeves/aluminium block allowing enough flex to compensate for the problems with short rods? I'm just taking a shot in the dark, because I REFUSE to believe that they rev so high because of magic.

Now, I think we all had enough discussion and flaming on this topic from the older threads, but I eagerly await EVERYBODY to come out and tell me I'm wrong again. Including the Tool. And then I can explain my position, and get flamed some more. :thumbsup Good times ahead!

-=B-=

i actually read all that. interesdank indeed.

Originally posted by The1Bill
Well, if you want a longer rod, feel free to use a deck plate and either sleeve the block or lower the top ring. I, myself, however, would probably destroke the crank a little bit.

im talking about a *at most* 7800 redline, 2gnt ignition cut. rod ratio of 1.8+ wouldnt even be able to bring it that high so yea, i agree with you...to have any sort of reasonable redline without a deck plate isnt to practical. de-stroke is a good idea

Originally posted by The1Bill
Higher RPMs allow bor better use of gearing. That being said, I'm a hypocrite. I am using a motor with an iffy (at best) rod:stroke ratio, and a LOOOOOOOONG stroke.

tell me about it :) all the way to 7800 with a neon gearset would be pretty fun at 20psi 2.4L

Originally posted by The1Bill
Hell, I like torque. Since I like torque, I also don't mind a shorter rod. It will suck harder from 10* until 90*, and less hard from 90* to BDC. Furthermore, while you can take your dwell time at TDC, I'll take my dwell time at BDC. Why? So I can open my exhaust valve earlier. Also, the intake valves can close a bit later without pumping cylinder air back into the intake manifold.

well if you think about it...higher performance camshafts will have the exhaust valve opening well before BDC. gases will be exhausted when there is still pressure in the cylinder so that this pressure can help to get the exhaust flowing out. or for the gearheads, 'blow-down' vtec's a good example

Originally posted by The1Bill Besides... What marque of motor is the paragon of high-revving? Yeah, Honduhs. A B16 has a rod:stroke ratio of 1.52, and some Honda motors have a 1.48 rod:stroke ratio! I think that the stroke is what does the revlimit on the SRT-4 the most damage. If you want the 2.4L motor to rev higher, I think you are just going to need to destroke the crank.

1.48 rod ratio? holy shit, thats so horrible. you've got me...why the hell can honduhs redline so high?

Originally posted by The1Bill Now, is it possible that the Honduh blocks can rev so high because of their flimsy open deck/unlocated sleeves/aluminium block allowing enough flex to compensate for the problems with short rods? I'm just taking a shot in the dark, because I REFUSE to believe that they rev so high because of magic.

hmmm...i'd like to know too, especially with that shitty rod ratio



_________
96 talon esi-t
san clemente, ca


as needles of ice
are the ill winds' talons
the coldest of shadows
they seep unto the bone

silent souls leave .308 holes

Originally posted by turbo8u
hmmm...i'd like to know too, especially with that shitty rod ratio

because it's mostly about pistons speeds, valtrain weight and durability, sorry but stock for stock the honda valvtrain is stronger than ours, BUT not when we have the PT rocker/lifters installed

as far as spinning - rod ratio doesn't matter all that much until you pass the threshold which is about 1.45

the tsx has a 4 cyl 2.4L with a 87mm bore and 99mm stoke and redlines at 7100rpm, makes about 200hp NA and 166ft lb's
_________
96 talon esi-t
san clemente, ca


as needles of ice
are the ill winds' talons
the coldest of shadows
they seep unto the bone

silent souls leave .308 holes

Hondas rev so high mostly because they can. Do you think Joe Ricer cares about his rod ratio? No, but he'll take it to 9000RPM on his hacked ECU as often as he can. Do they scatter? Sometimes. More often, probably not.

You can't just look at the numbers and expect anything to match what you see in practice. Materials, balance, and construction have a lot to do woitj it, just as much as the numbers do.

The board died on my the first time I tried posting to this. Just as well, it was something lame and sarcastic. I ended up learning a lot in here. Thanks guys.


And someday there may be a 2.4L in Daisy. I just want there to be a lot of experience with installing them before I take that road. I don't need to be having shit in my daily driver breaking all the time due to a hack install.

Dank you all very much. (Since dank seems to be the word du jour) :thumbsup

Originally posted by DR1665
Dank

lol ;) dank indeed.

2.4L at like 12.5:1 comp, insane cams...omg brian, thatd be SICK :) your car would OWN



_________
96 talon esi-t
san clemente, ca


as needles of ice
are the ill winds' talons
the coldest of shadows
they seep unto the bone

silent souls leave .308 holes

2.4 2.4 2.4 2.4
Turbo I had a dream last night. There was this mountie....and he had stolen your 2.4 to give to me. Then we smoked some of your DANK you were telling me about. He stole that too. lol

Originally posted by Blizare
2.4 2.4 2.4 2.4 Turbo I had a dream last night. There was this mountie....and he had stolen your 2.4 to give to me. Then we smoked some of your DANK you were telling me about. He stole that too. lol

LOL! dude i had this one dream where all the 2 liter neons had a recal and they all got replaced with 2.4's and i went in and was like AH! WHERE MY 2.4?! and they were like 'youre not a neon' LOL! its even subonsciously haunting me :P

they jacked our dank? its cool...we'll get some more



_________
96 talon esi-t
san clemente, ca


as needles of ice
are the ill winds' talons
the coldest of shadows
they seep unto the bone

silent souls leave .308 holes

alrighty then! found out some GOOD info! the mopar stage 2 kit actually brings the redline on a srt to 6500, and MANY people have turned the stock block over 7250. i was talking to some of the guys over at srt forums and we were just discussing upgrading the valvetrain would be the only need-to when wanting to turn that high of rpm's. so 7250 it is ;)
_________
96 talon esi-t
san clemente, ca


as needles of ice
are the ill winds' talons
the coldest of shadows
they seep unto the bone

silent souls leave .308 holes

I don't think that the valvetrain is the absolute limit with the 2.4... Perhaps it is on the 2.0, but the stock bottom end on the 2.4 would take a dump before the valvetrain. That being said, it's not impossible to break valvetrain parts with a 2.4 and stock cams, but if they DO break, it's fate. Safe bet to upgrade the valvetrain at the earliest convenience, though.

-=B-=

Originally posted by turbo8u
alrighty then! found out some GOOD info! the mopar stage 2 kit actually brings the redline on a srt to 6500, and MANY people have turned the stock block over 7250. i was talking to some of the guys over at srt forums and we were just discussing upgrading the valvetrain would be the only need-to when wanting to turn that high of rpm's. so 7250 it is ;) _________ 96 talon esi-t san clemente, ca as needles of ice are the ill winds' talons the coldest of shadows they seep unto the bone silent souls leave .308 holes

I agree with Bill, the valvetrain would surive longer than the 2.4L could safely spin at 8K+, The SRT valvetrain is similar to the PT in that it can survive a solid 8500 rpms,

spinning cracked caps and maintaining crank adhesion is a different story

I think it could be done but not with the stock rods with 500 WHP and that high a redline

Just so you know, HRC spun the 2.4L in their Neon way beyond 7000RPM. I think i heard them say it bounced up to 9000 between shifts. That car had a LOT of passes too, and they never lost a bottom end from the high revs.

Crower rods, JE pistons. Saw it myself... Just food for thought.

a lot of the guys over at srt forums are HELPFUL :thumbsup. ive been talkin to a lot of them lately and they said basically, yea...it will definately redline that high but without some different cams you'll be choking it out. also, changing the valvetrain parts for our head is probly a good idea like bill said, at the most convenientt time possible. crane 18 cams would be pretty sweet too. i was just worried about having a 7250 redline in the 2gnt ECU and having a block that could only wind up to 6000, but now i know it can go higher ;) that was the whole point of this thread anyway

thanks guys :thumbsup its good to know i have some people around who actually know wtf they're talking about, try going on a honduh board and talk about somethin like this....or fuck...dsm tuners for that matter

skrilla, when are we doin your swap dude?
_________
96 talon esi-t
san clemente, ca


as needles of ice
are the ill winds' talons
the coldest of shadows
they seep unto the bone

silent souls leave .308 holes

Originally posted by turbo8u
a lot of the guys over at srt forums are HELPFUL :thumbsup.

You're kidding right? I can barely read SRTForums without wanting to strangle some of those morons.

Originally posted by DarkOne

Originally posted by turbo8u a lot of the guys over at srt forums are HELPFUL :thumbsup.

You're kidding right? I can barely read SRTForums without wanting to strangle some of those morons.

thats unfortunate, i think you just need to browse around...there are some knowledgable guys, just have to find them. there are a ton of kn0bs but thats the same everywhere.

skrilla...im gunna kill you.

dood, i have more shit you definately want to hear ;)



_________
96 talon esi-t
san clemente, ca


as needles of ice
are the ill winds' talons
the coldest of shadows
they seep unto the bone

silent souls leave .308 holes

Originally posted by DarkOne
Just so you know, HRC spun the 2.4L in their Neon way beyond 7000RPM. I think i heard them say it bounced up to 9000 between shifts. That car had a LOT of passes too, and they never lost a bottom end from the high revs. Crower rods, JE pistons. Saw it myself... Just food for thought.

No doubt,

however I was refering to the SRT internals, I have absolutely no reservations about aftermarket intenals taking any abuse you throw at it aka 8K+, I'm just not sure about SRT internals at 8K+, I'll only end up taking mine at 8K as the limit. I figure with a solid 20 lbs and 8K redline I can pull a couple ponies out of my ass on some Crower 2's

Originally posted by turbo8u
a lot of the guys over at srt forums are HELPFUL :thumbsup. ive been talkin to a lot of them lately and they said basically, yea...it will definately redline that high but without some different cams you'll be choking it out.

Nothing I haven't known since before SRTs were conceived, remeber there were no cams for me when I 1st went 2.4L so I knew regrinds were the best I could do at the time and are very aware that stock SRT/2GNT cams do not move enough air to make real gains (there are gains just not what you'd see with aftermarket cams)

Originally posted by turbo8u
also, changing the valvetrain parts for our head is probly a good idea like bill said, at the most convenientt time possible. crane 18 cams would be pretty sweet too.

FUCK THE 18's - it's all about Crower stage 2. The 18's get shit on by Crowers

Originally posted by turbo8u
i was just worried about having a 7250 redline in the 2gnt ECU and having a block that could only wind up to 6000, but now i know it can go higher ;)

dude where have you been I told you I did 7250 on STOCK STRATUS INTERNALS!!!

I did it for 2 weeks with absolutely no sign of tear before I dropped in my JE/Crower combo. certainly if those weak internals can take punishment, the SRT shit can take more.

Originally posted by turbo8u
try going on a honduh board and talk about somethin like this....or fuck...dsm tuners for that matter skrilla, when are we doin your swap dude?

You're SO gonna hate me, LOL.

We're doing it after my STANDALONE!!! MWUHAHAHAHAHA