Upping the power band of a KA24E

[DBM]

I've been starting to plan my build for my 90 240SX ministock car. My home track is a 1/3 mile paved oval. When I run the gear ratio's, tire diameter, and speeds through a calculator, I find that the engine RPM's will be a bit higher than what might be optimal for a mostly stock KA24E.

I've been using this KA24E dyno graph as a reference for the powerband:



Does this look like a decent representation of a typical KA24E with basic bolt on mods (intake/exhaust)? The site that the graph is from stated that they increased the output numbers by 20% to get an assumed crank HP/TQ numbers.

I'm not allowed to perform any engine mods aside from the header, exhaust, and intake (up to, but not including the TB).

What would you reccomend to move the torque band a bit higher? Power under 4700RPM is of no concern since the car will typically only run between 105-125kph on 23" tall tires in third gear.

Here are my current plans:

-Short intake with the filter placed in the stock battery location. The pop-up headlights are removed.
-Custom 4-1 exhaust manifold with 1-5/8" primaries.
-2.5" side exhaust exhaust with straight through muffler in the stock cat location. (the rules limit us to a max exhaust diameter of 2.5")

That is about all I am allowed to do. No port matching, no adjustable cam timing gear.

Aside from getting the engine to breath better and building a custom header with large diameter primaries and proper length runners for 5000-6000rpm, is there anything else I should consider for moving the power band up?

[eazye2000]

It's very hard to move the powerband up on either the single or twin slammer in stock form.
That dyno chart looks like a stock motor's crank hp/tq. Doesn't look like whp/wtq numbers.

If you could at least use a timing gear, you would have a chance. But with your header idea, you're on the right track. The single cam motors powerband can be moved all over with just a header swap. 4-1, 4-2-1, and any other variety you can think of, will change just hp, just tq, or both; or even move either/or to the left or right.
I've not messed with too many of the single cam N/A builds, but I have read a boat load on them since I have a fetish with them in N/A form, and ITB's...
I will see what I can dig up, and PM you some stuff. I think there is a local guy to me who has some header building/swapping experience with a single cam. See what I can find.

[DBM]

Awesome, thanks for the help! I look forward to any info you can provide!
I've built a couple of headers for other cars (4-2-1 for a toyota 3TC, and a 4-1 for a toyota 20R, but have never had the ability to do any dyno testing to confirm anything. For all I know, I could have made things worse.

[Def]

I think there's a free program out there that will calculate ideal tube lengths for header design. It's pretty simple to calculate by hand if you know the relevant parameters too since it's a simple hermoltz resonance calculation.

[KA240SX808]

A good Big Tube 4-1 would be a good start to shift the power. Are you allowed a Tuneable ECU? Cause that would help a bunch too. I believe a Shorter Larger Diameter pipe is ideal for a High RPM app. Theres an equation for all of this but those are kind of te rule of thumbs IIRC.

Burns SS has a good program they can whip up a nice header for you. Also are you allowed to Update/Back date to other SOHC KA parts? Maybe switch Intake Manifolds and Cams?

[Matt93SE]

If you were allowed to swap cams, I have a MONSTER custom ground KA-E cam that's capable of over 200whp with proper compression and tuning... it's got 0.55" lift IIRC.. they changed rules for SCCA Production classes and the cam isn't legal for SCCA anymore. If anyone else is interested, make a reasonable offer (cam cost over $1000 to make).

[DBM]

I think there's a free program out there that will calculate ideal tube lengths for header design. It's pretty simple to calculate by hand if you know the relevant parameters too since it's a simple hermoltz resonance calculation.

I no longer have the free program that I used when designing my last two headers, but I'm sure that there are plenty that are just a google search away. I was hoping to find some feedback from people who have real world experience with different header designs on a KA24E, mostly in regards to primary diameter I guess. I'm not allowed to port match though, so going with a large diameter primary will result in a rather large change in cross sectional area from the port to the primary. On my 3TC header, I ended up tapering the tubes so that the chance in diameter was more gradual than a step, but there is only so much I could do with a hammer and an anvil.

[DBM]

A good Big Tube 4-1 would be a good start to shift the power. Are you allowed a Tuneable ECU? Cause that would help a bunch too. I believe a Shorter Larger Diameter pipe is ideal for a High RPM app. Theres an equation for all of this but those are kind of te rule of thumbs IIRC.

Burns SS has a good program they can whip up a nice header for you. Also are you allowed to Update/Back date to other SOHC KA parts? Maybe switch Intake Manifolds and Cams?

Burns make some seriously beatiful headers. Works of art! I learned a lot be reading the info on their site, but that was 10 years ago. I should return to their site to refresh my memory. I'm sure I have forgotten most of what I learned.

What other KA24E parts are compatible with the KA24E in my 90 240SX? The rules limit me to using the 12V engine since the max displacement allowed for 16V engines is 2.0L.

[KA240SX808]

I'm assuming this is staying in an S13 correct? Sorry for some reason I was thinking like a Dirt Sprinter or something where Manifold design wasn't an issue. I was going to suggest that you could try out the Stanza Manifold or see if it could offer any kind of gains over the 240 Manifold but a FWD Manifold in a 240 probably won't work...

[DBM]

Yup, the KA24E is being used in a 90 240SX chassis.
I just reaquainted myself with Burn's stainless pricing on their collectors. $300 for a mild steel 1-5/8" 4-1 collector. :P

[Matt93SE]

I forget what sizes Joel is running on his Burns-designed KA24E header, but they're much smaller than you would think. and that header put out 10ft lb torque higher than anything else he's run, all through the power band. I think it's running like 1.25 or 1.5" primaries with a step in them about 11" out that goes to the next size up. after the collector it's only 2 3/8" the rest of the way back.

He sent me a drawing of it once, but I can't find it.

[blackbush]

on my ka I used the jwt long rod setup, offset wrist pin pistons too. that with their c78 cam shifted the power up. Motor really turned on around 42-4500.

[e1_griego]

I have a chipped sohc ecu if you're interested.

Make your own tunes and rule the world!

[tonto]

i got a bone stock '90 w/ single cam motor and that dyno in first post looks really optimistic to me. iirc driving mine around the power starts to fall off by 4k.

[e1_griego]

Here's mine. Blue line is stock. Red was ver.1 of ecu tuning. No torque plot obv (dumb).