TJKASS

Alright, ive done my research on the forum and havent found much factual response to this, so im asking the knowledgeable engine builders and those whove had experience with this engine, with all supporting headwork done to prevent valve float and increase VE (cams, springs, retainers, upgraded buckets/shims, light P&P), what is the safe RPM limit of the bottom end? Id assume the rod bearings end up being the weak link, but after looking at similar motors from other manufactures (honda K24A, Nissan QR25DE (2007 to present)) that have strokes that are even longer than ours 99mm, and 100mm respectively, yet higher redlines, im wondering what a relatively safe limit is on the stock bottom end. I would guess something like 7200rpm hard cut so that it wont bounce over 7500 ever, but thats just me basing it on the other comperable engines average RPM limit, and toyotas higher revving engines (3s series, 2zz series) and strokes.

So please chime in, id like this to be a relatively intelligent discussion, and if youve spun a bearing in the bottom end, or threw a rod, id like to hear from you too on what caused it to happen or when it happened.

Based on flow calculations my head should keep making power till around 7800 rpm but thats assuming only a 15% torque drop from peak VE of 100% (guestimated but argueably accurate) to peak HP(which I would like to be at redline). In the real world im expecting an NA application like this with some good cam overlap to see more like 22% drop which would put my peak HP at 7200 rpm.

So enough of my nerdspeak, and dont worry if you didnt understand all that, if youve got good information id love to hear.

Thanks.

And I plan on using a Unichip to control the RPM limiter, A/F, timing advance, and cam timing, and it will be getting dyno tuned. But that wont be happening till this summer.

So the question again is, what range of RPM is relatively safe on the stock 2AZ bottom end?

ESEMRFOZZ13

no you can not make power until 7800 rpm, with bolt on's. look at countless dyno charts.why would toyota put the rev limit where it's at? hp is max at certain rpm range, so why rev higher when thiers no more power in stock form. they would have to beef up the head and cause more wear on a motor not making more power. honda is geared on hp not torque, so it uses rpm to make up for torque.

gingles

iTrader: (1)

highest ive seen was around 8k with head work. no need in going higher then that. this is of course if your turbo/supercharged. if you just have bolts on i dont see a need in you going higher.

TheQuietThings

the motor just does not make enough torque at RPMs higher than 6700 for it to be worth having the car rev any higher.

the tC torque curve really dies out after 6200RPM, and for those who know the equation for horsepower (torque X RPM / 5250), it doesnt make sense to let the motor run from 6k - 8k.

TJKASS

Well let me just put it this way, like I said earlier in my first post, I will not have just bolt ons, i will have a fully built 3 angle P&P head with 264/256 cams and 1mm OS valves as well as new buckets, springs, etc, that should help with that torque drop off, and as this is generally untouched territory (looking for good N/A power) I just want to know what the bearings and rods are generally considered good for so when I am getting tuned, if I am still making power by say 6700 RPM, will it be reasonably safe to run the engine out higher to see just where the HP drops off?...

btw, the reason that torque drops off so fast is because of the cams and valve angle, the same reason the torque comes online so fast. The valve angle I cant fix but I should be widening the effective flow angle which should push the torque curve to the right, and the cams, adding +16 duration, and higher lift on the exhaust should also help keep the torque up again.

And what all was dan gardner running on his RR tC cuz I know he was running all the way to 7500rpm, and why would he be revving that high if no power was being made out there? I realize he had higher comp pistons but those dont really effect your VE, which effects where the torque curve begins dropping off.

So the question again is not will I make power up there, but is the bottom end capable of handling higher RPMS than stock?

TJKASS

And how is the honda "geared" more for HP? the valve angle is only 1* greater, the lift is only .4mm more, and the valves are the same size. The only difference is the cams, which are much longer duration, much closer to what Id be running now, so why would I not be making power still in the same range that engine is?

ESEMRFOZZ13

i said in stock form. honda has differant bore X stroke, engine design. for your question, i guess it depends on your year of motor. do you have 07 and up? miles? if you do go with a full n/a build keep us posted.

draxcaliber

i'm not an engine builder, but i was reading in a thread long ago about how if the 2az fe was revving at over (some rpm over redline) rpms etc, the bottom end would be spinning faster than formula 1 engines based on his calculations of the engine speed vs crank speed. so that with such a long stroke to ask the engine to rev that much is a pretty crazy thing to do this engine.

TJKASS

Yes the honda has a 87mm bore instead of our 88.5 and it has a 99mm stroke instead of our 96. heres some info from wiki...


K24A2

• Found in:
  • 2004-2008 Acura TSX, JDM CL9 Accord Type-S, RB1 Odyssey Absolute
    • Displacement: 2,354 cc (143.6 cu in)
    • Power: 200 PS (150 kW; 200 hp) @ 6800 rpm
    • Torque: 232 N·m (171 lb·ft) @ 4500 rpm
    • Bore: 87 mm
    • Stroke: 99 mm
    • Redline:
      • Automatic 7100 rpm
      • Sequential Sportshift 7300 rpm (7100 rpm U.S.)
      • Manual 7600 rpm (7100 rpm U.S.)

and yes I do remember that post on here too drax, most F1 engines are a 40mm stroke compared to our 96 so the mean piston speed of an F1 engine at 19k RPM (redline) is ~ 25m/s=40mm*19000*2/60.

the engine in an s2000 has the same mean piston speed, as well as the engine in the TSX, and for ours to reach 25m/s we would need to rev at ~7800 rpm. (96mm*2*7812.5/60=25) I dont plan on running it that fast. was more thinking conservatively that the power would end at around 7200 with my mods, but seeing as modern day manufacturers can fairly easily acheive the same mean piston speed as an F1 car makes me feel even more comfortable about it. at 7200rpm the MPS would be 23m/s (still slower than a K20A), and up from stock 20.16 (pretty slow looking at most modern day engines actually). I understand this is not a factory high performance engine but being below what many other engines come with from the factory still, Id think its still pretty safe. Still open to suggestions tho. And right now im just trying to go for 200whp N/A on a dynojet 248C or equivalent without opening the bottom end. I have a feeling i can get pretty close. So you can call this a moderate N/A build. Just testing this engine right now, but if this headwork and tuning shows promising results, I may continue with some 12:1 pistons and some nice bottom end work as well. But those are all dreams and right now this is the first stepping stone to getting there. Plus this car with 200hp would just be a blast. Shoulda come that way from the factory. (hell toyota did completely underrate our engine, its actually got more like 175 sae from the factory 145whp*1.2(Drivetrain losses of 20%)=174 hp crank. So getting it close to 220 or 230 should be capable. Laugh if you will, but not in this thread.

Thanks for the opinions and info, please keep it coming.

mileoutrage

my opinion! this looks like awesome territory to venture into, 190-200 whp shouldnt be a problem at all, one thing i should mention is when you get the 1mm os valves is to get your shop to mico polish the ridges on the valves, in my past cars i have had gains as little as 4hp and much as 7. and as im looking at your sig i see that you had unichip as something you are going to tune with, i would deff ditch that in for apexi safc neo or aem fic.
but other then that gl with the build, im headed down the same path its good to seem something different.

skakemokid

iTrader: (1)

can you take off the rev limit on the unichip?
I thought the only one capable was the ultimate.

mileoutrage

nope you cant, ultimate is the only one that can do that, unless you go standalone of course

TJKASS

ill have to see on the revlimit stuff as unichip assured my it could alter it on our cars, Ill be meeting the guy who will be tuning it for me in a few weeks, so ill make sure it raises the rev limit. But for some reason it seems like it can cuz it can lower it for a valet parking map and stuff. and no to the FIC for one simple reason. I cant advance timing with it so its useless for NA tuning. more timing advance = moh POWA!

TJKASS

and ill keep that info about the micropolishing in mind mileoutrage. and looking at your siggy, is someone else shooting for 200 whp NA as well? if so, I think we need an NA power section on this forum as well so that we have E&D for the repair and newb info stuff, FI for the crazy drug addict ppl (I kid), and NA for those who wifeswap on the weekends. jk.

KillaKeola

Hey TJKASS are you still running the factory exhaust manifold? and with the custom s-pipe and mid-pipe does it make the TRD exhaust raspy and loud? Reason for asking is I have the trd axle back and dont want to lose that sound and I definately dont want any rasp. Im also hunting down 200+ whp! The route your taking you will definately get 200+whp. If your looking for 12:1compression look into the 2az-fxe its the hybrid engine but it has a 12.5:1 compression. Also look into Gude's head package I believe fastcions.com has it, they claim 45+hp N/A .Good luck on your build!

TJKASS

Right now yeah im still chillin with the factory header, not to say I wont go w/ a header if its necessary but I figured I want to see what I can do with the stock cat in place plus I dont really like making everyone behind me cry from my exhaust fumes lol. And its a matter of personal preference about the exhaust. You can hear just a hint, and I mean just a hint of resonation around 2800rpm at >40% throttle. Other than that its just a deep and very full/rich sound from there on up. and very deep below there. full throttle just sounds MEAN. and on the rev down theres just a hint of rasp, but it actually sounds good. Heres a link to a vid of someone with a setup like mine
http://www.youtube.com/watch?v=wBDmoDt0DZY
listen between 0:12 and 0:30 almost a slightly boxer-esque sound
another vid (again not me)
http://www.youtube.com/watch?v=fXr5oEMdsTQ

mileoutrage

yeah a NA section would be awesome on here! we wont have alot of people but hey it can be exclusive.

let me know what news you hear on the unichip im intrested to hear about that

TJKASS

Will def do. Just a warning tho, like I said it probably will be a while before I can get intouch with him, just dont lose faith lol. If you look on their website as well tho it confirms under the features that thats one of them. as well as control of valve timing (VVTi). Gah, tyler want! this engine would just sound awesome at 7200rpm. oh and ive also been told the unichip can indeed remove the speed limiter! woot.

mileoutrage

well if it can do those im jumping on it asap, i had someone offer me the ultimate here recently, glad i declined.

i plan on going with a ferrera 1mm os valves and valve train set( springs, retainers, seat locks, seat locators) with 3 angle valve job and cosmetic head gasket.

06sciontcnda704

iTrader: (1)

would it be safe to set rev limit at 6.4k to 6.5k with completely stock motor??