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Discussion Starter · #1 · (Edited)
Looking at building a k24 for an endurance series. I have to use a block/head for a k24a1 (for rules on one series) but in another series i want to run, i'm limited to horsepower to weight ratio. So the top teams are building their engines to have a very flat HP curve. So, as soon as the car hits a target HP on the dyno, the dial down the electronic TPS to maintain a flat HP curve.

So with that in mind, i'm looking for the path of least resistance to build something that will last endurance racing. My thought process is to start with the A1, toss in high comp pistons and add some drop-in cams. I'm not sure what this would net in terms of power (DJ). In a perfect world, i'd like to hit 200 hp by 6k RPM or sooner and hold it to 8k. I'm hoping that with proper oiling mods the engine can survive 24 hours revving to 8k. Otherwise i'd have to bump redline down to 7 or 7.5.

Mod list?

k24a1
  1. 12:1 pistons
    1. Required to use 91, so not sure its safe to go any higher than 12:1 for enduro racing.
    2. Also if pistons only buys me like 3 hp midrange then maybe its not worth it. I'd settle for TSX or CRV.
  2. Wide duration drop in cams on stock valvetrain
    1. Could use suggestions on brands
  3. OEM k24a1 intake manifold
    1. To inflate midrange powerband.
    2. Must use an oem plastic manifold. Heard a rumor that a r40 2009 TSX manifold MIGHT fit. If it does, it should be good for a much stronger midrange VS the CRV mani. Would also make the electronic TPS mod more plug and play. Wish i could find someone whose used the r40 before on older k24 heads.
  4. 4-2-1 header. Probably end up with a long tube design like hybrid racing. Also open to suggestions.
  5. Maybe port work? With a mindset on path of least resistance, porting is definitely high resistance.
  6. A friend suggested stroking&boring the block for 2.8L. This is definitely a high resistance path. If the engine can survive 24hrs at 8k rpms i'd really rather not do this.


Side note: The power curve has to AVERAGE at 200 hp for the last 2k of the RPM band. BUT, area under the curve is everything, and the winningest cars in this series are tuned for a FLAT HP curve as it has the most area under the curve.
 

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Discussion Starter · #6 ·
This is a good data point, but it looks like you don't hit 200 hp until 6100 rpm. Additionally, i'll be on 91 octane. My thoughts were to use the lower flowing intake manifolds (CRV/Accord) to help keep peak TQ lower in the RPM band. In order to hit 200 hp by 5k rpm (assuming a 7.2k redline), i'd need 200 ft-lbs by 5000 RPM. Which is 30 more torques than what you're making. That's actually a pretty big margin that i'm not sure can be covered by drop in cams. Unless of course there's something in your setup/tune that is running below your TQ potential between 5k-6k rpm. I have a feeling, and i could be wrong, that even with good drop ins, high compression, and other little tricks i'd struggle to hit 200 hp before 5.5k rpm. Anything i make beyond 200 hp doesn't help the goal at all, and i think that's what some might be fixated on.

The roller types that i'll be dynoing on are properly calibrated dynojets, which as i understand read a few % higher than a properly calibrated mustang. Not sure where dynapacks fit in the mix. I've been able to find dynographs of builds on the internet that do seem to meet my goals but the numbers are so hyper inflated over all of the other builds i come across. I feel like dynos are hard to trust on the internet.... I guess worst case i'll do what i can and try and drop weight to compensate, which would put me at a strong disadvantage at high speed tracks
 

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Discussion Starter · #8 ·
Good points. I'll be following along to see what you try.

The Dynapack that was used for the graph above is affectionately called "the heartbreaker", for some reason it measures 8-10% lower than the roller dynos in our area. A Dynojet graph would show 200hp around 5500rpm, which is closer to your requirements but still not there. My tuner maximizes everything for safe (endurance) power so I don't think that there's a lot more torque to be had with OE internals. Just for data points: I had my car on a Mustang dyno which showed a peak hp of 203 when this Dynapack measured 181 with the same tune.
Oh wow that is a big difference. Hmmmmmmmm perhaps a set of TSX cams can get me there provided my intake/exhaust mani are setup to emphasize that 5k torque bump. Just for clarification, you currently have the 50 deg VTC installed in your tsx motor? I found this article really helpful Technical Information Tuning the TSX
 
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