There has been a rash of threads and questions related to how much boost or how much horsepower a stock motor can handle before things start to break. I'm going to do my best to explain how and why things happen the way they do.

The KA24E and KA24DE are both very fun motors when boosted. They can be used for high horsepower drag cars or low boost dependable daily drivers. The selection of parts and where money is invested will determine exactly how and why things are going to happen to your motor.

First, lets start off with making sure the current motor and car are in fairly good condition. By that I mean the motor runs perfectly fine as it sits right now and the car isn't going to fall apart. Trust me, if you have any problems, adding boost is only going to compound them greatly.

Aside from running well and being mechanically sound there are a few things that should be looked at closely. One is the compression on all 4 cylinders. If you don't have a compression tester, I suggest buying one. They are about $30 from Sears where I bought mine. But they can be found at most auto parts stores. You're going to want compression numbers over 155 on all 4 cylinders and they should be within 10 psi of each other for the best results. If they are lower, I'd suggest a full rebuild before going with a turbo kit.

The next key part is the oil system. Its hard to tell the exact pressure without a standalone aftermarket gauge. But you'll want want 15psi or more at idle and over 30psi once the rpms have gone past 3000. Those are for an engine that's already warmed up. If its cold, they will be ALOT higher. Don't use those numbers. However, if you have low oil pressure when cold, and the car has been running for more then 2 minutes, shut the car off and inspect the oil system. Hopefully its just low oil level.

The coolant system should also be working well. Adding a turbo creates more heat inside the motor and more heat under the hood. So a good cooling system is a must have. The factory system will work fine for a low boost setup. Just make sure you keep an eye on things. Overheating a turbo motor will lead to detonation and can wreak havoc on every system in the car. You'll never hear people say, "Man, what a waste of money he put into that cooling system". If you do, chances are they don't know what they're talking about.

The last main system that needs to be inspected is the ignition system. Adding a turbo will require you to use a different spark plug. One that is one or two heat ranges colder. You'll also use a shorter plug Gap then stock. Start with BKR7E from NGK and gap them to .038 and close the gap as you run into spark issues. But that's a whole story by itself. If you want to change the wires while you're swapping plugs, might as well. There is no such thing as having something work "To Well".

With all that said, lets move on to the actual point of this thread. The stock internals in a mechanically sound motor will take a good bit of power. We have members pushing close to 500WHP on a factory parts. But we've also had motors fail in the 300's and 400's. A lot of this is do to poor tuning and or not taking care of the motor.

If the engine oil is changed frequently, then there should be no issues with the bearings seizing up. Clean oil is always a good thing. I relate some of the problems people have had to lubrication issues.

As far as tuning goes, money is the only thing that will limit your options. You have to really consider your end goal. Will a simple piggy back SAFCII or Greddy Emanage be good enough? Or should I look into Rom tuning or Standalone Ecu's? Well both work well for what they are. Cheap piggy back setups are good for making a small but fun amount of power. But if your needs are over 300, then I'd start exploring other options. The whole point of tuning is that without a good safe Air/Fuel mixture and the proper timing retard on boost. You could have the motor built with titanium parts and it will still break.

Finally, once you've got everything working correctly and you've decided on what method you're going to use for tuning. You come to the most important choice of all in my mind and that's what parts to buy or what kit to use. Every part in a system will have a max output. If that max output is lower then what your goals, then don't buy it. Trust me, settling on something will always haunt you. If you have to save for a few extra months to get what you want, then so be it. There are a lot of good deals to be found and a lot of choices that will work very well. But there are just as many bad choices along the way. Beware what you buy from EBay, some things just shouldn't be bought from a generic company. There is a lot of information in the KAT forum as a whole and a lot in the FAQ at the top of the page. If you can't find it there, then ask away. But please read through things at least a little before rattling off questions that are probably posted on the very first page already. A little research in the beginning will yield fantastic results later.

All of this comes to a close with me voicing my opinion and saying a safe bet for a sound motor when tuned properly is about 350WHP. Some will go farther, some will not. If my goals were more then 350WHP, I'd seriously consider saving for forged internals.

I hope this has helped some of you out. Never be afraid to ask questions. Worst case we'll just tell you where to look.

Happy Boosting
WD

Thanks

ca18det powered 240sx
http://www.alabamagz.com

Megan Racing Parts supplier.Among many more companies Act, hks, b&m, sparco,msd,etc. hotrod6000000@yahoo.com
KA-T why settle for anything less?

Man, why you guys have to call me out like that?!

Just kidding. Glad to see someone posted something like this.

*edit* Sorry, had to fix it.. I couldn't make fun of WD like that.....'lord I apologize....' Don't wanna piss him off, he don't talk to me on AIM anymore.. LoL

Modified by eazye2000 at 8:40 PM 2/6/2007

Also, dont forget those poor SOHC engines dont have the same compression as DOHC engines. So when doing a compression test, maybe you should put a lower number for them. IMO compression should be above 165+-10psi for DOHC.

I have been on the site for a while, in the KA forum. So, I do know that searching is usually easier (and faster) than asking something and waiting for answers. However, if you search for something, you usually get a crapload of different topics about what you searched for, and after looking at the first 10 or 15 and they all say "use the search!!!!" you get tired of looking.

Maybe someone should go through and clean stuff out?

I know its probably done anyway. I know I searched for something, and couldn't find anything on it. I searched three or four times before posting something, and sure enough...."try the search key."

WD

ka-t, kat, boost, pressure, stock psi, boosted, ka24de, ka24e, compression #, compression, numbers, cylinders, coolant, WHP, HP, power, Internals, stock internals, spark plug, sparkplug, turbo, ignition.

Another question they typically ask is how much boost the KA can handle. I think this is a valid question for the following reason.

We all know that there is a difference between boost and horse power. This is normally attributed to larger turbos flowing more air. If we consider this dynamic, we will find that it is in the upper RPM range that the larger turbo's increased flow comes into play. More to the point, when the motor exceeds 5250RPMs and HP exceeds torque the bigger turbo is able to provide quality boost while the smaller one makes heat. I believe this is where the HP discrepancy comes from. In the lower RPM rages, where both turbos are efficiant, there should be no difference between the two.

Because the larger turbo will ultimatly make more HP at a lower boost, many with smaller turbos plan to run more boost to compensate. What this does, if my thinking is correct, is produce more low end strain on the engine parts and loses efficiancy (make heat rather than O2 mass) in the high RPM range. Obviously this is bad.

Suppose one's goal is 300HP. While a T04E 50 trim will make this at a cool, easy ~11lbs. A super 60 will require around 17lbs - and a good amount will be heat rather than mass.

From this, we see that running a larger turbo with less boost is prefferable to a smaller one with more boost. The mistake we often hear is that a given boost level from a larger turbo makes more power and is therefore more dangerous. For the reasons cited above, I think this is somewhat of a mistake. While the larger turbo will obviously make more HP at a given boost level, I'd have to say that the larger one with the greater HP is by it's nature, the safer of the two at any level of boost.

So, the logic would break down like this:

For a given HP, bigger @ 10lbs = smaller @ 15lbs - and safer.

For a given boost level, bigger @ 325HP = smaller @ 270HP - as safe.

So, I propose that the bigger turbo can make a given HP more safely than a smaller one, and more HP with equal safety than a smaller turbo at the same level of boost.

So, the answer to how much HP can my motor handle might sound something like " 325 - 350 with a T4 or 250 - 275 with a T3."

1992 Nissan 240sx KA24DE-Turbo: The "Showcar"
Stock internals
532whp/486ft.lbs-30psi
12.6@122.3mph-22psi
http://ka-t.org/cory_b.php

both engines are completely different. besides the fact they both handle boost well. one revs to the moon. one will torque your house off the foundation(it WOULD be cool) almost... they are just different not better than one another. they were made for different purposes from the factory by engineers.

the KA's got a hella strong bottom end(the crank journals are bigger than the RB's are). and that means only good things for us!

please don't read into things/assume things like that. it can/will make you feel silly.

--keith

Actually, his statement is pretty on par. In fact it's much more correct then your's. The SR doesn't "rev to the moon" especially in factory trim. The KA has been taken to 8500 rpm...so I fail to see the difference there. The torque curve isn't THAT big of a difference. The main thing is the KA already resides inside of the 240, so why swap in a smaller motor? Everything comes down personal preference.

The article is simply talking about the KA, so there's no real reason at all to compare it to the SR20, which in itself is a very well built motor.

WD

--keith

thanks

how many psi with a 14b isnt that comparable to the t25? anyways no more than 5psi and thats with a good *** romtune or an afc and btm cause you gonna have det on stock map....

----------------------------------
r.i.p. Lee
09/01/89~09/28/06

How Long have you been daily driving at your power level now?

WD

I only post information, nothing further. I think, based on conclusive stories, that far too many failure stories are related to operator error. Should that data be deemed inaccurate?

I've been over 400whp since April of 2006.

I of course simply stop when I've maxed out my fuel system. But in my case I tossed a rod shortly there after. I was at 165,000 though and was still using the stock oil pump. I definitly think a spun a bearing and tossed the rod.

WD

This leads me to ask: Where is the Boost PSI measured? I always thought it was measured somewhere between the turbo and throttle body... If that's true, then 15psi is 15psi - Right??

I'm saying, you have a sealed tube. You keep this tube regulated at 15psi. Now you poke a hole in this tube, you start pumping in to the tube keep 15psi in there... At this point, you are pushing X amount of air to keep 15psi in this tube... If you were to push more air, you will be increasing beyond your 15psi.

In this case, the tube is your intake, your air input is your turbo, and the hole in the tube is the action of your engine intaking air...

I'll admit that I know next to nothing about a turbo, but I'm just questioning the logic of this... Please correct me if I'm wrong, or if I have missed the point completely....

Thanks guys!!
Justin

Hope that helps.

A) Density
or
B) Mass

You cannot measure air in volume, only the container in which the air is held. Air has no volume, it has mass, which is affected by density in a given volume container.

Yeah Cory- that's exactly what I meant-but I was referencing the volume as in CFM cubic feet per minute. volume is also relevant to mass and density. see below.

"The volume of an object is equal to its mass divided by its average density. This is a rearrangement of the calculation of density as mass per unit volume.

The term specific volume is used for volume divided by mass. This is the reciprocal of the mass density, expressed in units such as cubic meters per kilogram (m³·kg-1)."

You just made the volume of air more at your intake, but the pressure is still the same; Therefor, you still only have 15psi at the intake of your head, and you can only squeeze so much through there.

In other words, you are increasing the size of your compressor; However, the space filled by the air from your compressor to your cylinder is still the exact same. So your volume is the exact same.

The reason I say this is because with the box fan theory you gave me, you are changing the size of the output holes. So now you would have to have a larger volume to be able to regulate at 15psi....

Make sense?

I think I understand what you are saying, all I know is it happens. Yes two turbos of different size blowing 15 psi may be equal, however the larger turbo is working less to match the smaller turbo which is maxing it's output, thus the larger one has plenty of forced air on tap when needed, where the smaller will leave the engine wanting more. In retrospect I see how you'd say it's the same, pretty much the only reason to buy a larger turbo is to push more boost, not to hold it back. To some the smaller may be suitable, but it's an addiction, and from many people's advice, it's better to go a little bigger in the beginning so you have some "growing" room in the future. I'm no scientist, I wish I knew how to explain it better and plainer- but it just makes sense to me.