k24 RPM limit

[tinkerbell]

is it for circuit racing or drag racing?

[Benson]

Ill stick with 7400rpm rev limit

[EG5]

No point reving higher if power drops off @ 7000rpm

Yup No point to rev it high if power drop
Mine starting to drop at 7600 rpm on stock cams
More RPM on k24 = Engine wont last

[CRXer]

The reason for the higher rev-limit is also to do with the gear ratios of the k24a3... shifting from 1-2 with a 7000rpm limit would see you drop out of the power band and in 2nd gear you'd only be at about 4200rpm.

the rev limit question your asking is really irrelevant to gaining quicker times out of ur stock k24.

im fairly sure u'll find more torque clawing at the road in any given higher gear at 4200rpm than u will any where above 7000rpm on the lower gear on a stock k24.i think your misinterpreting where your powerband actually is.

most stock honda motors ive seen have a rev limit 500rpm higher than where u should be shifting at,its just for a bit of headroom so your not bouncing the limiter all the time while trying to get the most out of what the motor will provide.
it would be terribly painful if u had 100rpm of limiter above your useful powerband,especially in first gear, u would be bumping the limiter all the time.
i dont know how fast your needle is moving at the top of first gear,but i know mine is moving too fast to differentiate 100 rpm,or maybe im just slow......

go out the quater mile & shift at 7krpm & then try shift at 7500rpm,im sure u'll get better times at 7krpm.

[integral90]

the rev limit question your asking is really irrelevant to gaining quicker times out of ur stock k24.

im fairly sure u'll find more torque clawing at the road in any given higher gear at 4200rpm than u will any where above 7000rpm on the lower gear on a stock k24.i think your misinterpreting where your powerband actually is.

most stock honda motors ive seen have a rev limit 500rpm higher than where u should be shifting at,its just for a bit of headroom so your not bouncing the limiter all the time while trying to get the most out of what the motor will provide.
it would be terribly painful if u had 100rpm of limiter above your useful powerband,especially in first gear, u would be bumping the limiter all the time.
i dont know how fast your needle is moving at the top of first gear,but i know mine is moving too fast to differentiate 100 rpm,or maybe im just slow......

go out the quater mile & shift at 7krpm & then try shift at 7500rpm,im sure u'll get better times at 7krpm.

You've really got to drive the Euro to understand how stupidly large 2nd gear is compared to 1st. He's not talking about having more torque up high, but shifting at a higher km/h as to land higher in the revs in 2nd.

[CRXer]

You've really got to drive the Euro to understand how stupidly large 2nd gear is compared to 1st. He's not talking about having more torque up high, but shifting at a higher km/h as to land higher in the revs in 2nd.

uve pro got a slightly better second gear than my DC2 second,but ur right theres a large discrepancy between 1st & 2nd on the euro box posted above.

the point is liam,what does the torque curve look like after 7krpm?
ive never seen anybody dyno a k24 past 7krpm,its prob cos the torque curve is headed off into the abyss by then.
if what described above is correct about u landing at 4200 from 7000 then ure landing right into the meat of the torque curve on the stock k24,whereas at 7500 in first gear,ur prob making like very little more,if not less, than u would be in 4200 second,which is a big statement for 1st -2nd gear comparisons. once u get up to 2nd-3rd,4th-5th,game over.

k24 has a fairly long stroke on it,id hate to think how fast those pistons are moving at 7500rpm.

[fatboyz39]

k24 has a fairly long stroke on it,id hate to think how fast those pistons are moving at 7500rpm.

I remembered @7500rpm on k24 is like 9000rpm on a F20c, piston speeds i.e.

Why not get k20a internal and fit it into the euro box? Or use a smaller tyre wheel combo.

[Chris_F]

thanks for the input everyone

is it for circuit racing or drag racing?

circuit

the rev limit question your asking is really irrelevant to gaining quicker times out of ur stock k24.

im fairly sure u'll find more torque clawing at the road in any given higher gear at 4200rpm than u will any where above 7000rpm on the lower gear on a stock k24.i think your misinterpreting where your powerband actually is.

most stock honda motors ive seen have a rev limit 500rpm higher than where u should be shifting at,its just for a bit of headroom so your not bouncing the limiter all the time while trying to get the most out of what the motor will provide.
it would be terribly painful if u had 100rpm of limiter above your useful powerband,especially in first gear, u would be bumping the limiter all the time.
i dont know how fast your needle is moving at the top of first gear,but i know mine is moving too fast to differentiate 100 rpm,or maybe im just slow......

go out the quater mile & shift at 7krpm & then try shift at 7500rpm,im sure u'll get better times at 7krpm.

There were a few reasons why I came up with the rough 7600rpm figure

• That's where hondata sets the redline for their ECU reflash.
• By looking at the gear ratios and engines power curve taking into account the torque multiplication factor of lower gears. See:http://www.datsuns.com/Tech/whentoshift.htm

This all lead me to believe three things:

• the ideal shift point isn't what will land you at the engines peak torque
• the ideal shift point isn't at the engines peak power
• the ideal shift point is achieved when "firstgeartorque is equal (or close to) secondgeartorque" (accounting for the torque multiplying factor of gear ratios)

edit:
for comparison:
dc2r 1st gear = 3.23, 2nd = 2.105
euro 1st gear = 3.533,2nd = 1.880

[CRXer]

but thats what im saying,what is the torque figures like at 7500rpm?
i could imagine theyd be pretty grim,cosidering it looks like the k24 is rolling off the top of the cams at 7000rpm.

is that so jimmy,luckilyy the F20 was built for those type of speeds

[Chris_F]

but thats what im saying,what is the torque figures like at 7500rpm?
i could imagine theyd be pretty grim,cosidering it looks like the k24 is rolling off the top of the cams at 7000rpm.

is that so jimmy,luckilyy the F20 was built for those type of speeds

I'm still waiting for the car to be tuned properly, so I won't know for certain untill that happens. Torque will definitely have dropped by 7500rpm though. But accounting for the 1st gear torque multiplyer it will still be higher than the available torque in 2nd had I shifted at 7000rpm.

The cars stock rev limit is set at 7300. see: http://www.hondata.com/reflash_tsx.html you'll notice that with the reflash/intake and header peak torque occurs at 6000rpm

[fatboyz39]

Ok for circuit. Then changing from 1st to 2nd wont be a problem. When we had the k24, it had the usual stuff, Intake, RBC, 62mm t/b 3' exhaust, headers. Power dropped off around 7100rpm.

[Chris_F]

Ok for circuit. Then changing from 1st to 2nd wont be a problem. When we had the k24, it had the usual stuff, Intake, RBC, 62mm t/b 3' exhaust, headers. Power dropped off around 7100rpm.

Good point... the 1-2 shift really only matters on the drag strip. Maybe 7400-7500 is more sensible after all.