ka-t and sr20

[Driftin_240sx]

ok lets just start this off like..no this is not a ka-t vs. sr20 bout... i am just wondering... the sr20 is more revv happy and the ka is more torquey...so ..wat makes the sr so much more revv happy.. i meen isnt it possable to make the ka-t rev happy too.. like with some new valves and stiff valve springs? and if u did this would u lose your tourque on the ka and just might as well buy an sr20? just wondering.

david

by the way.. i still have some 18" tenzo poke 10s for sale with tires...550$..

[email protected]

[Potatoskins02]

I may be totally wrong about this but i believe that that the KA is more torquey because of its large bore and stroke. I think this was in some magazine article recently. I could see the KA being more rev happy if it had more aggressive cams i guess. I doubt you'd loose torque by doing this but I may be wrong.

[Kreator]

Why ka is torque happy:
big stroke, long intake manifold.
can you get rid of this:
most likely not. There aren't too many parts concerned with the engine exactly to make this happen. You can make a shorter intake manifold but you can't fix the stroke.
And yes, you will lose torque doing this.

The only probable thing u can do is get an fj20 crank and then rev that shit up. But ask AceInHole bout that.

Why would you want revs so badly anyway?

ps, i have a half made intake many for the ka, so if you interested pm me. I got some pics...

[AKADriver]

There was a short stroke KA20 in Japan.

But, yeah, it's not worth it.  You'll gain a few revs and lose a bunch of torque, balancing out to a net loss.

[Driftin_240sx]

i was just wondering because i want to build a ka-t and i was just wondering if it was possable to make it rev higher...SAFER... u dont think it would make a diff. to push the rev limits up? and u are talking about losing torque trying to make it rev happy..so then wouldnt it basically be a .. majorly bored out sr20 that didnt come with a turbo and i might at well get the sr20??...

ha hope u followed the last part*

david

[onefast240]

You could make the time bomb KA motor more rev happy by De-stroking the motor. You do this by crank size rod length and position of the pin on the piston. For the $$$ you would spend on having all of these things made you could by an SR20 put the toda or jun stroker kit in and have a beast of a motor for less than the KA.

[240racer]

when you say that the sr is more rev happy do you mean that it likes running at higher revs then then the ka?  in other words, you can rev it at 7000rpm longer before it breaks, or what.  Or are you just saying that the sr revs higher without breaking.  If you are worrying about the conrods breaking, then the reason it doesn't rev as high is because of the longer stoke.  If you are worried about valve float, then it is due to the valve springs.  If you are worried about breaking or wearing out a valve spring due to prolonged high rev operation, then the valve springs should be replaced with ones that are meant for that.  For me, I'm just worried about making power.  I could care less what else happens as long as I can make as much power as possible for the amount of money and I don't break anything.  If that means revving higher, then I'll do that, if it means making more torque, then I'll do that.  The torque that the KA puts out below 4000 rpms is not only useless in high performance driving, but it is also mostly due to the cams.  If you run a lower lift, shorter duration cam, then you make more torque on the low end, if you run a higher lift, longer duration cam, then you make more torque on the high end.  The intake runners and exhaust runner lengths come into play a little, but not as much as the cam.  A longer stroke does not affect where the engine makes more torque, it just makes more torque everywhere, since the con rods are attached farther from the crank center and with the same force on the top of the piston, they create more torque.  The downfall of the longer stroke is the increased recipricating inertia that is developed.  That is why it is a compromise.  Either engine, the SR or the KA can make just as much power, but since the SR has a shorter stroke, it will need to do it at a higher RPM to make up for the loss in torque.  It is convenient that the shorter stroke can reve higher, since it doesn't have as much intertia.  The KA doesn't need to rev as high to make the same power since it has a longer stroke and therefore makes more torque all along.  As long as both engines have the same manifold pressure (either they are both NA or both have similar turbo setups) then the KA will make more torque, but in general will not be able to rev as high due to the inertia.  However, both engines should make similar power, possibly the KA would make a little more due to it's larger displacement.  The honda S2000 is probably what most of you would call a rev happy motor, but it only makes 240hp, and peak torque is very near redline and peak horsepower would probably occur after redline, if you bumped it up a little.  This setup makes it hard to use the engine, since you will always go faster if you keep revving, it's nicer to have a stop, where you know that the power drops off and you know where to shift.  
Peak torque occurs at peak volumetric efficiency.  This is where the engine has the best ability to pump the air in and out (mostly in)  this is mostly determined by the cams and how much air they allow in.  If the cams are planty large, then it may be determined by the size of the intake runners or something like that.  On a 2 valve engne (like most american V8s) the valves start to limit the airflow and smaller levels.  This is why they tend to tune them toward lower rpm peak torque values.  With more valve area, the amount of air that is easily sucked into the engine gets higher (hence more power) and most engine designers use that and increase the rpm range where peak torque occurs.  The KA was intended to be used in trucks and sedan type cars, and the designers know that truck drivers often want to use higher gears at slower speeds for smoothness and other reasons.  That is why the torque peak occurs lower then you would ever get if you shifted at redline.  This is due to cam profiles, mostly.  The SR is similar to a typical japanese engine and has a step shaped torque curve that rises sharply to a peak and stays constant until about 1000 rpms short of redline (that way you know that you don't need to rev higher, because you are past the peak efficiency)  This engine is very easy to drive fast, because in the range of RPMs used, the torque is consistant. I have a '91 KA with about 8psi of boost and the torque curve feels like it has a step up at 4000rpm and stays consistant till about 6000-6500.  I can't wait to get it on the dyno and see what it really works out to.  I think that the curve is well suited to high performance driving so far.  If I see something that needs to be changed after I dyno it, then I'll make the proper adjustments.  I'm not sure if I will get much more power out of revving higher, so I probably won't.  

I think I am out of breath, hopefully I have helped more then hurt, feel free to post here or PM me if you have ?s

[Jeff240sx]

</span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote (onefast240 @ Dec. 09 2002,10:50)</td></tr><tr><td id="QUOTE">You could make the time bomb KA motor more rev happy by De-stroking the motor. You do this by crank size rod length and position of the pin on the piston. For the $$$ you would spend on having all of these things made you could by an SR20 put the toda or jun stroker kit in and have a beast of a motor for less than the KA.</td></tr></table><span id='postcolor'>
Slightly biased, are we?
You could port and polish, get cams that work with the KA, and valves and springs to slightly raise the redline. &nbsp;JWT says that stock the motor can go up to 7k, and I think boosteds14 and possibly ty have taken their car up to 7.5k. &nbsp;Why need redline when, if you have torque, you will have a motor with the same ammount of horsepower that will last longer?
It is easier on your motor to produce 500hp at 6000 rpm than to produce 280hp at 9000rpm. &nbsp;This is because of rod travel, distance, speed, and sudden acceleration and deceleration of the rods. &nbsp;This causes the metals to get out of shape and eventually they will die.
-Jeff

[Driftin_240sx]

heh thanx 240racer for the life story.. hope u got your breath back.. but thanx it helped out. what does your ka-t consist of? how many miles do u have on it? did u rebuild?

david

[240racer]

I have a CT-26 turbo on a custom manifold with a custom FMIC. &nbsp;370cc/min injectors, S-AFC and 3" exhaust with a dynomax muffler. &nbsp;The engine had 150,000miles on it. &nbsp;I haven't rebuilt it yet, but I am working on it this winter. &nbsp;Compression is a little low. I posted some pictures of it a while ago, if you want to look it up