KA24DE Max RPM

[Specvengeance]

Ok so I recently purchased a 240sx coupe that is a auto to 5 speed swap. when the transmission was swapped in the rev limit and the Speed limiter had not been installed with the new transmission.

I was driving around last night and I was freely revving the engine to7000 rpms with no problem.

I tried searching google, this site, and wikipedia with no result. SO this leads to my question.

What is the highest I can safely rev this engine to without having to have the car towed home and have the motor replaced.

Thank you in advance for the help.

[Dittoz7]

Over 9,000!

[Dittoz7]

Opps You Have The Wrong Engine!

http://www.nicoclub.com/articles.php?id=238409

[BOOM_STICK]

if your looking to safely rev it then stay around the redline (around 6500-7000 rpm) , there's a reason for it. if you want to go higher look into some head work, cams, and maybe a tune

[simmode1]

if your looking to safely rev it then stay around the redline (around 6500-7000 rpm) , there's a reason for it. if you want to go higher look into some head work, cams, and maybe a tune

Sounds like whoever did that swap knew what they were doing. The speed/rpm limiter is the bane of most 5spd drivers. Most of us do the limit removal ASAP.

AFAIK auto's don't have the limiters anyway, so when the swap is done, you don't even have to worry about them.

But I've seen some ppl retune their ECU's the limit rev's the 7200. Seems like thats the edge of reliability. You probably want a cam swap to take advantage of those rpm's though...

[Specvengeance]

I am not really looking to rev it any higher but I also dont want to blow the engine

So thanks for the help

[DjPantsSpecR]

cams are not really the limiting factor for making power at high RPMs, its really the intake and exhaust manifold.

Okay, just some absolute info in this thread: Sometimes when people put auto ECUs in their manual cars they get a 7200 rpm limit. i dont entirely believe this to be true, but it might be. my stock manual car used to rev to 7200 stock, but only under no load. i jsut did a swap in my buddies car, manual but auto ecu, and his still only revs to 7000. i think lots of it could be resolution on the tach, or maybe something mechanical or electrical.

The point is, on stock cams and intake manifold, you're starting to lose power once you rev over 6500 rpms. Its fine for 1st gear, and maybe stretching out 2nd gear, but thats about it.

NOW, for the actual information from a Rebello engine builder who chimed in on a thread of mine from years ago:

The front snub nose of the crank snaps off because of the harmonics at 8000rpm. on stock crank, 8k will toast your motor. 7500 is safER, but still not useful without supporting modifications. However, the builder did go on to say that the crank pulley bolt hole can be drilled past the first journal (i believe), tapped, and then install a longer bolt, and these motors are safe past 8000rpm, EVEN without a fully weighted crankshaft

with supporting headwork that is

[neverlift]

where the hell have you been man????????

so was that for sohc and dohc engines? I'm sure, just getting some deffinate answers. and I believe does not cut it

my rpm gauge looks like hits 7500 all the time, but I know its set to 7000k.

ka was designed to make low end power, mani/runner length reflect this IIRC.

[murda-c]

Wow i've never heard any of that before.

Good stuff DJpants

[simmode1]

DJPANTS is like a sniper... you never know when he's around and he's hits you with super accurate info outta nowhere!

[ThuG LyFe]

on stock KA i think max torque is at 5500. so i don't even see the reason to rev past 6k.

[-RJ-]

on stock KA i think max torque is at 5500. so i don't even see the reason to rev past 6k.

agreed, but i want to know where my power actually falls. I would go get a dyno and study the sheets

[neverlift]

plenty of stock dyno sheets floating around to look at. they fall off in part due to the crank design, the manifold is another major factor in the ka not being rev happy. Compare the size of a ka and a d series ka is ****ing huge

[xckid]

i once f d up real bad when shifting and i pegged my rpms over 8k i saw the rpms fly all the way up i was for sure my motor was toast ....nope still good for now....i would not recommend doing it

[spooled240]

I've heard that our tachs are not very accurate in high rpms. I remember reading in the ka-t forum of some guy who dynoed his car and he was going off he stock tach, stopping at 6500. But the rpms on the dyno read about 500 rpms lower than the factory tach. This is just what I've heard, but it seems like this is possible reading some of these posts on this thread.

The most I rev my ka is 7K and that's rarely and for not very long lol..My ka has went way into redline before for very short periods of time and it still runs fine...

rpms will not kill your engine as much as the duration at those rpms will...like revving to 7500 for 1 sec will not be as bad as 6500 rpms's for a 10 sec.

[DjPantsSpecR]

Thank you for the kind words, i've been around, but mostly doing school stuff and working on my friend's 240s

the info i was referring to was for both SOHC and DOHC, as the cranks are the same. if you're really VERY interested i could pull it out for ya...

[n240sxfnatic]

12,000 unless you have v-tec then its 14,000

[spooled240]

i don't wanna see a thread in the next 24 hours saying "i blew my engine after revving at..idk the needle went past 9" lol

keep it under 7K and don't spend too much time there either

[destroyyourmind]

when they swapped the transmission they didnt swap with a 5sp ecu thats why theres no rev limit

[ThuG LyFe]

http://www.youtube.com/watch?v=TBtpyeLxVkI

here's a video that has all your answers

[i240sx]

so if you have a auto ecu, there is no rev limit...????

[spooled240]

that doesn't sound right, you could still put the car in nuetral or park and free rev it

[DjPantsSpecR]

it isnt right, there is a rev limit, just no speed cut, and no 5k rpm 5th gear limiter.

[neverlift]

it isnt right, there is a rev limit, just no speed cut, and no 5k rpm 5th gear limiter.

qft

[turbo2nr]

if you get the vfac u can rev to 10k! and be jdm tyte!woot!!!

[thefro526]

I rev the crap out of my Ka and there isn't sh't over 6k. The only time I ever get up there is when I really need to stretch out first or fourth but even then it's kinda pointless or when I'm drifting and even then I usually can keep it under 6k. If you needed to I guess you could run up to about 7K and that's where I get a little worried but if it's a but here and a bit there you should be fine.

[simmode1]

Thank you for the kind words, i've been around, but mostly doing school stuff and working on my friend's 240s

the info i was referring to was for both SOHC and DOHC, as the cranks are the same. if you're really VERY interested i could pull it out for ya...

Yes please. For all the ppl planning on doing supporting mods, yes. I would like to know the specifics involved with making a KA rev past 8k.

[ka-t4u]

i would also like to add to all this great information that even though our engines are very low compression and we shouldn't have to worry about these things, i would like to remind you guys that when Any engine is spinning that fast things tend to go a little farther due to the momentum they generate, mostly the valves tend to shoot down a little farther and the pistons might come up a little higher, and also KA's (on their stock form) don't really make much power all the way out there so for our safety we should just be happy with 7000

[simmode1]

i would also like to add to all this great information that even though our engines are very low compression and we shouldn't have to worry about these things, i would like to remind you guys that when Any engine is spinning that fast things tend to go a little farther due to the momentum they generate, mostly the valves tend to shoot down a little farther and the pistons might come up a little higher, and also KA's (on their stock form) don't really make much power all the way out there so for our safety we should just be happy with 7000

Very true. But the info could be really usefull for ppl planning full KA-T builds with aggressive cams, titanium valve springs, ect for a higher rev limit. Not saying I'll do this crank mod, but it's always good to at least evaluate new info.

waiting on the info...

[lrb_2000]

I've heard that our tachs are not very accurate in high rpms. I remember reading in the ka-t forum of some guy who dynoed his car and he was going off he stock tach, stopping at 6500. But the rpms on the dyno read about 500 rpms lower than the factory tach. This is just what I've heard, but it seems like this is possible reading some of these posts on this thread.

The most I rev my ka is 7K and that's rarely and for not very long lol..My ka has went way into redline before for very short periods of time and it still runs fine...

rpms will not kill your engine as much as the duration at those rpms will...like revving to 7500 for 1 sec will not be as bad as 6500 rpms's for a 10 sec.

I believe it.. when my tach says 6,500 rpms my SAFC II says about 6,000.