'93 240sx lacks higher RPM power

[racer33]

I just bought this car, and the engine was rebuilt about two years ago. Mechanically it seems fine, but it doesn't have the oomph at upper RPM's that I expect. I have had other 12-valve 240's before that seemed stronger then this. Can anyone point me in the right direction to start? Fuel Filter? Catalytic Converter? Air filter is very clean, plugs are NGK and almost new. Thanks for the help.

Mike

[swwifty]

thats normal for a KA, mine drops off after about 5-5.5k rpms.

[InsanityInc]

Yep. Nothing wrong with your car. We're still trying to figure out an easy way to fix it.

[DjPantsSpecR]

i love seeing that dyno chart, because everytime i floor it you always feel exactly that. Power kinda falls off at about 3500 then gets goin again. However, i don't really ever feel that 4500 rpm drop off. Maybe my butt dyno sucks ***, but i think it keeps cookin untill about 6000.

hey isn't that dyno of an S14? That could explain the ultra-poopy power fall down, but if you don't like your powerband, the best thing you can do is manipulate it with different cams

[InsanityInc]

Yeah, it's an s14 dyno, but the s13 one is almost identical. Due probaly to the butterfly valves and ****tastic intake manifold.

The reason why you don't feel the dropoff until about 5500/6000 is for one, your engine is modded, and for two, peak acceleration occurs at your power peak, not your torque peak. Go drive an s2000 some time and it's VERY obvious.

[hek1620]

i am minus the butterflies in the intake mani and still have drop off at 5500-5600. hopefully the turbo will remedy this.

[swwifty]

i think its mainly camshaft design, put some decent cams in there and maybe a better intake/exhaust manifold and that would help it up top.

[InsanityInc]

problem is there really aren't any decent cams for the KA NA. I think the problem is the cam makers are used to making a cam for a shorter stroke engine and thus don't consider that the intake close needs to be later for the longer stroke. I'm going to screw with my stock cams one of these days and see what I can get.

[BadMojo]

problem is there really aren't any decent cams for the KA NA. I think the problem is the cam makers are used to making a cam for a shorter stroke engine and thus don't consider that the intake close needs to be later for the longer stroke. I'm going to screw with my stock cams one of these days and see what I can get.

Any thoughts on the Colt cams that PDM sells?

I originally thought that the subject of the thread was a mere statement of fact, rather than a question or problem.

"The KA lacks top end power"

"Yes, yes it does. It also sounds like a de-tuned chainsaw motor. Next question, please."

[InsanityInc]

Any thoughts on the Colt cams that PDM sells?

I originally thought that the subject of the thread was a mere statement of fact, rather than a question or problem.

"The KA lacks top end power"

"Yes, yes it does. It also sounds like a de-tuned chainsaw motor. Next question, please."

Their cams seem pretty meh. It's obvious from their 4AG cams that they know what they're doing, but it just seems they didn't consider the wackiness of the KA when making the cams. It's a pretty unconventional engine as far as high RPM tuning goes, so it's going to need an unconventional grind. I'm thinking it needs a much later intake closing point than would normally be required for any given RPM level due to the long stroke and small bore creating a high velocity slower fill situation, so it can pack more in if you give it time, but if you don't it's going to suffer greatly. I think there might be a place with a dyno very near to me, so I might be able to do some extensive testing pretty soon.

[BadMojo]

I think there might be a place with a dyno very near to me, so I might be able to do some extensive testing pretty soon.

Colt's website says they do custom jobs. Might be worthwhile depending on what your dyno time shows. I'd love to see more options for the NA KA. Gotta be some way to wring more power out of that boat anchor under my hood.

[InsanityInc]

Yeah, I know there is. I think what happens is that people go crazy with the duration on both cams which gives a crazy overlap that doesn't help that much on the high end, but slaughters your low end, but at the same time they end up with that ideal late intake closing point. You should be able to design a set of cams with a long duration intake cam, a shorter duration exhaust cam and just a bit more overlap than stock and see greatly improved high end performance without a horribly rocky low end like a similar performing racing camshaft would give.
Modified by InsanityInc at 3:41 PM 9/3/2005

[DjPantsSpecR]

maybe when we had 11,000 rpm rotating KADE like those BAJA trucks have, we'll be in business....

*****-*** overlap... i really wish we could get more hardcore evidence for low overlap exhaust cams

[NateDogg]

Hey InsanityInc..

Have you ridden in Don's car ? (PDM-Racing)..

I have. Maybe you shouldnt shoot your mouth off about products you have no experience with?

There is no 'lack of high rpm power' in that ride..let me tell you!

Don knows a lot more about cars than you ever will so don't doubt his or Colt Cams ability to design. Given it is a re-grind and the thing idles like stock and passes emissions perfectly fine, not to mention gives 10rwhp, I think you are being ignorant to the work that has gone into the cams and the excellent results they have obtained.

Now look at JWT..With their billets, they can't do any better! Does that tell you anything?________________________________________________________

To answer the question, there are a few things you can do.

You can replace the PCV valve which is a major PITA. I did it from the top without removing the intake manifold but I think it may be easier from the bottom if you put the car on ramps or jackstands.

Make sure your air filter is clean or put on a cone and adapter. Combine this with a heatshield around the cone filter and it is nearly as good as a $300 CAI.

You can also gap your plugs a little wider. I would go to .050" and try that.

There is also a bit of easy wiring you can do to increase the input voltage at the ignition coil. Do a search for it. Basically just run a 12 ga wire from the battery with a relay to the coil which increases the voltage.

If you are running 91+ octane, you can bump the timing to 24-25* BTDC. This is an easy 5 lb. ft tq and 5hp.

Fuel filter may need changing. I'd recommend a Z32 filter, since it is cheaper and larger capacity (longer life) than a 240sx filter.

If you really have a lot of time on your hands, you can check the valve lash on your cams. Too much clearance between the shim and lobe will reduce the duration of the cams and cause a loss of peak hp.

I would say try those things, minus the latter, and let us know if any of it helped.

[InsanityInc]

Hey InsanityInc..

Have you ridden in Don's car ? (PDM-Racing)..

I have. Maybe you shouldnt shoot your mouth off about products you have no experience with?

There is no 'lack of high rpm power' in that ride..let me tell you!

Dynos don't lie, and I'm not impressed. Note how the power is still dead long before redline. Most of the gains are between 5500 and 6200rpm. Look at the torque curve as well. It's a marginal gain. Also, as far as being regrinds and passing emissions goes: that's all well and good, but also completely irrelevant to the topic of improving the power of the engine. When a cam upgrade produces less power than a catback upgrade, it can be done better.

[240DRFT]

how do the jwt cams compare to those pdm ones? anyone got a dyno chart?

[racer33]

Somehow I was afraid this would be the answer. I'm actually planning to set this car up for circle track racing. I can completely remove the exhaust if that will help (all the way to running a bare manifold). I really don't want to spend a ton of $$$ trying to stretch out 5-6hp though. I do appreciate the ideas on gapping the plugs and setting valve lash. Any other thoughts? I used to race an '83 200sx and wanted to do another one, but I can't find any.

Mike

[InsanityInc]

Somehow I was afraid this would be the answer. I'm actually planning to set this car up for circle track racing. I can completely remove the exhaust if that will help (all the way to running a bare manifold). I really don't want to spend a ton of $$$ trying to stretch out 5-6hp though. I do appreciate the ideas on gapping the plugs and setting valve lash. Any other thoughts? I used to race an '83 200sx and wanted to do another one, but I can't find any.

Mike

Well, if you're going to use it for circle track racing, the best plan would probably be to alter the transmission gearing (or final drive I guess) to try and get your powerband in line with your maximum grip speed. That would probably be the cheapest way to get the desired results I think. At least without some kind of crazy cam.

[racer33]

I think the stock gearing will work ok for that. I need to be at about 95mph at the end of the straight. I'm guessing I don't want to run the engine beyond 6200 rpm or so, considering it's a 500 lap race.I'm pretty sure I can play with tire sizing enough to get where I need to be. My speedo doesn't work (HUD) though. Do you know where 3rd gear tops out with stock 195/60/15 tires?

Mike

[InsanityInc]

http://www.socal240sx.org/ under the FAQ->specifications section has the gear ratios for 240s. I can do the math later, but I don't have time right now.

[RipShift]

At just under 7 grand, your at about 92-93mph... just did it last night

[miked808]

High Flow Cat. and 3in. Exhaust with no resonator on N/A zooms!

[Bigvinnie]

I just bought this car, and the engine was rebuilt about two years ago. Mechanically it seems fine, but it doesn't have the oomph at upper RPM's that I expect. I have had other 12-valve 240's before that seemed stronger then this. Can anyone point me in the right direction to start? Fuel Filter? Catalytic Converter? Air filter is very clean, plugs are NGK and almost new. Thanks for the help.

Mike

Well you can do a bunch of things to increase more power in the High End.Larger TB's in 65mm or 70mm help with flow numbers in high end.Chopping the intake runners in half will improve high end for 16valve KA's.Moving the MAF and filter 6" to the TB will increase high end.Better ignition like MSD SCI, blaster coil 2.Advance your timing 3 or 4 degress at the distributor.Better aggressive cams PDM or Jim wolfe.Larger high flow cat, and exhaust.Removal of the 91-93 KA butterfly's.Coolant bypass.Performance headers recomended in 4-2-1 Hot shot/DC Sports/Thorley/OBXBelieve it or not even an aluminum fly wheel will increase aspiration in higher RPM's.I've been told that the largest improvement in high end power will mostly be through ecu reprogramming like a standalone like the AEM EMS, or a JWT ecu matched up with an APEXI SAFC. It's mostly air/fuel where the KA lacks greatly and runs more towards the richer side rather than running really lean.Swap to the NISMO 5th gear ratio of .838, or just pull the .838 ratio gear out of a wrecked 97 frontier truck, makes 5th a little more jumpy in the high end.If you want some boostable numbers camden super charging can build an eaton blower for the KAE's and KADE's


Modified by Bigvinnie at 1:29 AM 9/11/2005

[miked808]

I've only done Half of what Vinnie suggests and my Top End has increased 100 fold.

[InsanityInc]

Well you can do a bunch of things to increase more power in the High End.Larger TB's in 65mm or 70mm help with flow numbers in high end.

No, it won't. The 60mm TB already has a CFM rating FAR above the power anyone has attained on an NA KA.

Quote »Chopping the intake runners in half will improve high end for 16valve KA's.[/quote]Yes, this will help. However, logistically it's almost impossible, at least without a custom plenum.

Quote »Moving the MAF and filter 6" to the TB will increase high end.[/quote]Nope. Anything you do before the TB won't affect your power anywhere. All helmholtz reversion occurs inside the manifold. All this will do is increase throttle response.

Quote »Better ignition like MSD SCI, blaster coil 2.[/quote]I've never seen great results from this, so I'm inclined to say it's not true, since they rarely if ever have made gains on dynos I've seen in the past when compared to a new OE coil.

Quote »Advance your timing 3 or 4 degress at the distributor.[/quote]This doesn't make that much of a difference beyond the power peak.

Quote »Better aggressive cams PDM or Jim wolfe.[/quote]Their cams don't help all that much. They add some power, but it's mostly from increased lift and doesn't really move the power up very much.

Quote »Larger high flow cat, and exhaust.[/quote]That only increases power across the band, it doesn't shift it at all.Removal of the 91-93 KA butterfly's.

Quote »Coolant bypass.[/quote]That's just a small flat increase in power across the board.

Quote »Performance headers recomended in 4-2-1 Hot shot/DC Sports/Thorley/OBX[/quote]Once again this only helps in the current range of the engine. There is a manufacturer dyno of the DC sports header on their website which shows this, and other headers aren't much different.

Quote »Believe it or not even an aluminum fly wheel will increase aspiration in higher RPM's.[/quote]No. Changing your FLYWHEEL will not change anything about your aspiration at all. End of story. You can't change your aspiration by changing something that's not even connected to the system physically or conceptually.

The only KA I've ever seen that performs adequately at high RPM levels is the NISMO KA for their race frontier truck. And they're pretty tight-lipped about what they did.

[Nismo_Freak]

Nope. Anything you do before the TB won't affect your power anywhere. All helmholtz reversion occurs inside the manifold. All this will do is increase throttle response.

Once the throttle body is opened any variation in manifold pressure can be measured at the air filter. It essentially becomes part of the manifold, and the length of the intake determines particulates to pulse tuning parameters.

If you have the ability to get an SR gearbox you can get the faster 5th gear ratio from it. It is the same family (w71c) gearbox as the KA's and bolts onto the front bellhousing.

[Bigvinnie]

Once the throttle body is opened any variation in manifold pressure can be measured at the air filter. It essentially becomes part of the manifold, and the length of the intake determines particulates to pulse tuning parameters.

If you have the ability to get an SR gearbox you can get the faster 5th gear ratio from it. It is the same family (w71c) gearbox as the KA's and bolts onto the front bellhousing.

I like the way you stated that fact. Big Pimpin. I won't even begin to argue with any one in this forum, believe what you will felaz.

[InsanityInc]

Once the throttle body is opened any variation in manifold pressure can be measured at the air filter. It essentially becomes part of the manifold, and the length of the intake determines particulates to pulse tuning parameters.

Of course variation in manifold vacuum can be measured there, you're sucking air through it. However, air doesn't resonate through the intake pipe, or else vacuum measured there would have an obvious rhythmic fluctuation. Air never travels back through the intake pipe. The only effect it would have on helmholtz resonance would be the part of the equation put in for plenum size, since it basically becomes a plenum extension when you're at WOT. Therefore having a larger diameter pipe would help the same as having a bigger plenum, and hurt the same way as well.

[deviousKA]

All D21 4cyl 2wd from 86-97 have that .8xx 5th. The entire transmission is basically identical once the shifter is swapped over. Be aware that if using 240sx engine block the starter holes in the d21 bellhousing must be drilled out (they are tapped with threads).

The CORR offroad ka24de use "Web Cams" special grind, and custom buckets. You cant get much lift out of the cam before the lobes start walking off the side of the bucket/shim.

This is one of the reasons i only use de heads on 2.0-2.2l. They are a great head overall for that purpose aside from the exhaust port angle.

[Bigvinnie]

This is one of the reasons i only use de heads on 2.0-2.2l. They are a great head overall for that purpose aside from the exhaust port angle.

Yeah the only problem I find with the NAPSZ using the DE head is that you have to fabricate the napsz front covers and sump for de use. Who can make a front assembly for me Devious KA? I'm not inclined nore do I have the tools required to fab it my self, the sohc is much easier to frankenstien onto the Z blocks. Any info would be great I'm trying to do a DE swap onto the z block for a high rev boosted 510 project.