None of these options are budget....he wanted reliable. My thoughts are the less changed, the less for something to go wrong. Wadziis kit makes 270 NP and as long as the revs are kept down..should be reliable in a 4 hour race. My car peaked at 7500 rpm for reference

 

Actually, the opposite. Stock components are engineered for racing. They have different processing, different materials, different cost constraints.

Upgrading to racing level components bridges that gap by insuring parts fit with closer tolerances, use materials that have higher yield and tensile strength, treatments to reduce the chance of crack formation, etc. Running stock components that hard is just rolling the dice. The S2000 is better than most, but not perfect.

Note: your 2.4L at 7500 has only 2% more swept area than a 2.2L at 8200 and less than that engine at 8500. The FARA rules are for a 2.5, and at 10k it would have 37% more swept area than stock. At 8500rpm it would still be 16%.

That doesn't count any gains from less reciprocating weight, improved combustion, better sealing, better oil shedding, better flow, etc.

NASA rules really favor a broad power curve. That doesn't mean low revs, it would mean a power peak a little lower but that falls off more gradually after the power peak.

 

While I know nothing about swept areas and FARS rules, I'm just pointing the guy in the direction he asked. People with experience in a 2.4.
In my experience, some of these after market parts wear faster. From experience aftermarket cams wear a lot faster than stock. Oil analysis confirmed that for a fellow S2k bud. My stock 2.2 has been beat to hell for years (hours) and has been reliable. Im sure you're right if you can get custom oneoffs but off the shelf stuff is all we have for this car.

Dood (OP)really needs to chime in because we're going in circles not knowing what his budget is like. For all we know he's limited to 10k lol and all this talk would be pointless ahah

Most build a 2.4 for the torque and not really the peak whp..peak torque is at 5 to 5.5k iirc.

 

For NASA I think the 2.7L would be legal This is a rear wheel HP plot for a 2.7L, it actually looks like a good power curve for NASA:

 

This is a 14:1 compression Inline Pro 2.5L:

 

Those are drag motors that run 9sec passes and are then torn down....... this is the guys 2.5 you just posted. He runs 2.7 now.
https://www.s2ki.com/s2000/topic/112...pro-434hp-27l/

that motor will not be reliable for 4 hours.

 

You're pointing him in the wrong direction by posting those plots. The 2.5 is a drag motor and so is his new 2.7 making 400+

 

Those weren't the graphs...look again. the 2.7L I posted was a street car. The 2.5L was a race car, but easily could do an endurance race. It might need new valve springs at the end. It was doing 9500rpm. I thought it was a bit peaky.

The key is both revs and displacement are important. NASA is a bit unusual because of using peak HP from a dyno; that heavily favors a broad, flat power curve. Otherwise you want maximum area under the curve with the gearing you have for the track you are running on. My guess is the cam in the 2.5L had too little low end and a different profile might have traded some peak power for a better result.

How much compression you can use is a function of the gas you can use. If you can run 14:1 that is the way to go.

And don't forget the lightweight clutch/flywheel. The driveshaft could help but the OD is so small the impact won't be that great. It might help with lower vehicle weight if the car hasn't met its weight minimum or doesn't have a minimum. I think a CF driveshaft is around $900. The lightweight clutches from ATS and Tilton are in the $1500-2000 range. Tilton's is for a K24, but not an issue with a custom crank (or probably a K24 crank). Tilton's also uses a hydraulic throwout bearing; from experience, much easier to setup on an engine stand.

 

I guarantee neither of those cars see race like conditions for 20 min + at 9k-10k rpm.

Inline Pro says them self...these motors wear fast due to high revs and parts are changed often (their drag motor). Not one of these builds revs 9-10k for hours on end. Show us one person who "races" "tracks" their 2.4,2.5,2.7 at 9-10k for 20+min.....4hours..... I've given more than a few who make 270 and Rev anywhere from 7800 to 8200 that are not street cars. I don't understand why this is getting complicated lol I'm done haha

 

I believe the first 2.4 blew on him very quick and didn't last him at all last season and went on a spare (stock f22) so this might be his second one, just saying...from what I have seen its really hard to have a reliable 2.4 engine that can take the abuse a stock motor can. Unless its a toda built motor. Even then that might cost your sack Lol.