NA Motor Discussions regarding N/A KA24E, KA24DE, and SR20DE

KA24E improvements (pistons, etc)

Old 06-05-2008, 03:19 AM
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KA24E improvements (pistons, etc)

I'm fairly new to this but I've been doing some reading.

I'm building a 240sx for competition, it'll be fully gutted and stitch welded with a roll cage, I'm guessing somewhere around the 2400lb mark. I've got S13 Ohlins jdm suspension for it.

Now due to the rules I'm bound to the KA24E SOHC engine. I'm looking for more high end power and would like to move the usable power above 5500 rpm. I can't do anything too crazy due to strict rules. For example no SAFC or any other computers to control anything, no modifying/chipping the ECU, no ignition system modifications, etc

I've read that the Pre-Febuary built 1989 KA24E's have 9.1:1 compression vs the later 8.6:1. I also read somewhere about swapping pistons to get even higher compression? If I put the pistons from the 9.1:1 compression E motor into the 8.6:1 compression E motor what compression will I end up with. What about the opposite? Will this be a good idea given my restrictions?

Second is the MAF problem, I see upgrading to the N60 MAF will give me the higher powerband I want but I can't tune for it. I also read the thread about running the E60 MAF without tuning. I also noticed the S13 has the 60mm MAF, could I put a 70mm S14 KA24DE MAF onto this setup and have it work fine and give me what I want, possibly a compromise?

I'm going to be running a Cold Air Intake, 4-1 Headers for better top end power (Pacesetter maybe?) with 2.5" exhaust.

Is there any cheap nissan cam swap I can do that will help?

Other little things like the coolant bypass, vacuum lines and emission crap removal, A/C removal, SCV mod, grounding upgrade and I may do the modified catch can.

Any other little things I can do to improve that I'm missing? How does the EGR setup work, can I just yank that too?

Last edited by tehf00; 06-05-2008 at 05:46 AM.
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Old 06-05-2008, 08:40 AM
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Can you modify valves or do porting, honing, extruding?
Can you add bolt on's like aluminum drive shafts, aluminum flywheel, welded diffs?
Aluminum drive train parts can help pick up that re range a bit.
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Old 06-05-2008, 10:20 AM
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i have heard that 4-2-1 headers are better for the KA
and yes you can take the EGR stuff off
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Old 06-05-2008, 10:52 AM
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What kinda of valve modification? I can't do any porting, honing, extruding etc. The only thing I can do to the car is swap parts from the same manufacturer that I am able to use without modification.

There is no rule against bolt ons

From what I read the 4-1 give more higher end power while sacrificing lower end power compared to the 4-2-1
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Old 06-05-2008, 01:26 PM
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Originally Posted by tehf00 View Post
What kinda of valve modification? I can't do any porting, honing, extruding etc. The only thing I can do to the car is swap parts from the same manufacturer that I am able to use without modification.

There is no rule against bolt ons

From what I read the 4-1 give more higher end power while sacrificing lower end power compared to the 4-2-1
When you look at scavaging characteristics a 4-2-1 header it works better on a KA engine. 4-1 headers work good on engines that exceed an RPM range past 7000+RPM. A 4-1 header would be no good on a KA and from dyno's that I have studied 4-1 headers only make marginal gains in HP from 1-3 WHP gains. The 4-2-1 headers on the KA have shown wheel HP gains as much as 9whp. This is because the KA wont make significant peak power past 6500RPM, where as 4-1 headers don't start to make gains until after 7000RPM+.

If there is no rule against bolt ons you will want to look into an aluminum flywheel, and aluminum 1 piece drive shaft. Your going to need all the power you can get to the rear wheels. Possibly even look into aluminum rims as well.

Now in your case if you are allowed to bore the cylinder chamber I wouldn't even waste my time with sohc to sohc pistons. If you are allowed to bore you can look into the maximum bore of the KA block which is 91.5mm and go with a set of VG33E pistons which are 91.5mm. That will significantly raise your compression.
I would also look into thinner head gaskets.

If bolt ons aren't an issue you should look into an electric water pump as well as electric radiator fans.

Other than that I don't see very much more modifying for your situation, except for probably laser platinum spark plugs.
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Old 06-05-2008, 04:16 PM
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4-2-1 it is

and I'm rebuilding the motor and doing the deck, I'll go with VG33E pistons if thats the best. Any idea what kind of compression that would yield?

Thanks for the info, I haven't heard of that yet.

So would the SOHC block I get matter vs 8.6:1 vs 9.1:1 or are they exactly the same other than the pistons and if I overbore it won't matter anyways?

Last edited by tehf00; 06-05-2008 at 04:25 PM.
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Old 06-05-2008, 10:22 PM
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Originally Posted by tehf00 View Post
4-2-1 it is

and I'm rebuilding the motor and doing the deck, I'll go with VG33E pistons if thats the best. Any idea what kind of compression that would yield?

Thanks for the info, I haven't heard of that yet.

So would the SOHC block I get matter vs 8.6:1 vs 9.1:1 or are they exactly the same other than the pistons and if I overbore it won't matter anyways?
Well from what I understand the SOHC heads are the same so using the 89 pistons in your 90 will only yield a 9.1:1.

Now using the VG33 pistons a very enlarged piston with a crater style dish similar to the old NAPS-z style pistons. The advantage to using the VG33e piston is it's large piston size at 91.5mm. So you get much more compression and use alot more displacement to your advantage, not to mention the crater style dish can allow for much higher lift/duration cams.

PIC of VG33e piston

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Old 06-05-2008, 11:29 PM
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I'll give it a shot, which cam should I use?
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Old 06-05-2008, 11:51 PM
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Originally Posted by tehf00 View Post
I'll give it a shot, which cam should I use?
The PDM cams- colt cams C404.H
http://www.pdm-racing.com/products/cam_corner.html
http://www.coltcams.com/html/tri_flo...logy/index.cfm
You have to mill the cam towers, or get solid lifters with adjustable valve lash.

Last edited by BigVinnie; 06-05-2008 at 11:55 PM.
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Old 06-06-2008, 08:03 AM
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Ok, that sounds good. Any other OEM cam options from different motors? I'll prolly got the PDM way anyways just curious.

So the last thing is using a S14 70mm MAF (or other options)?
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Old 06-06-2008, 08:27 AM
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are you an scca member.. if so there are a ton of classes... I run in the EM class for my mods.. there is a class for whatever you wanna do...
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