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Discussion Starter · #1 ·
Ive read a lot about people saying that with stroking a motor you lose a lot of revability because of the stresses at a high rpm.

This is for built motors and racing applications.

I found that with a 99mm stroke @ 10,000 rpms, the piston speed is at 6496 ft per minute. I know there are people out there that rev their built k24's w/a 99mm stroke that high or alteast close to it when racing.

Now with a 102 mm stroke @ 9700 rpms, the piston speed is 6492 ft per minute, almost the exact same.

That doesnt seem like your losing much rpms or reliability at all.
To me the power gained with a 102mm stroke is well worth giving up 300 rpms.

If im leaving out other ways that stroking a motor would put more stress on a motor at high rpm let me know.

Also what would be a safe maximum piston speed for a racing application??
 

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In order to increase engine life and hence reduce costs for 2009 the max rpm of a Formula 1 engine will be 18000rpm. Maximum bore is 98mm therefore stroke = 39.7mm.
Piston speed at 18000rpm = 4689 fps

If an F1 piston was turning almost 6500fps, the crank would be spinning just under 25000 rpm.

At red-line an F20C piston is moving 4960 fps

6500fps is alot, how long could a motor really last for if its running at these speeds?
 

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Discussion Starter · #3 ·
I can see why formula 1 engines have a lower piston speed because they are closer to their max piston speed for a lot longer than a drag car. Im not sure how long a formula 1 race lasts but im sure the engines spend most of the time over 15000 rpm which is a piston speed of about 4k fpm, where as a drag car spends most of its time racing close to their max piston speed, but its only for 10-12 seconds.

If an oem f20c has a piston speed of about 5k fpm at 9k rpm, then i would assume that with a properly build motor/valvetrain that it could handle 10k rpms. Also i think most oem set redlines are made pretty safe and most people rev their cars past the oem redline w/out problems anyways. If a properly built f20c can handle 10k rpms with a piston speed of 5511 fpm, then i would think that a safe max piston speed would be around 5500 fpm for a drag car.

With that said, a k24 w/a 99mm stroke reved to 8500 rpms would have a piston speed of a little over 5500 fpm. Now i know that drag racers rev their built k24's over 8500 rpms w/out problems, to what idk.

Now a k24 w/a 102mm stroke reved to 8200 rpms would have a piston speed just under 5500 fpm. So i would still think that with a stroked motor, the gain in power would be well worth the loss of 300 rpms, and if you were to keep the 300 rpms, you would only be gaining an extra 150 fpm with your piston speed, so you wouldnt be losing much reliability at all with the stroked motor.

Is there any other variable besides piston speed that contributes to stress on the motor?? Maybe we can get some drag racers to chime in.
 

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I can see why formula 1 engines have a lower piston speed because they are closer to their max piston speed for a lot longer than a drag car. Im not sure how long a formula 1 race lasts but im sure the engines spend most of the time over 15000 rpm which is a piston speed of about 4k fpm, where as a drag car spends most of its time racing close to their max piston speed, but its only for 10-12 seconds.

If an oem f20c has a piston speed of about 5k fpm at 9k rpm, then i would assume that with a properly build motor/valvetrain that it could handle 10k rpms. Also i think most oem set redlines are made pretty safe and most people rev their cars past the oem redline w/out problems anyways. If a properly built f20c can handle 10k rpms with a piston speed of 5511 fpm, then i would think that a safe max piston speed would be around 5500 fpm for a drag car.

With that said, a k24 w/a 99mm stroke reved to 8500 rpms would have a piston speed of a little over 5500 fpm. Now i know that drag racers rev their built k24's over 8500 rpms w/out problems, to what idk.

Now a k24 w/a 102mm stroke reved to 8200 rpms would have a piston speed just under 5500 fpm. So i would still think that with a stroked motor, the gain in power would be well worth the loss of 300 rpms, and if you were to keep the 300 rpms, you would only be gaining an extra 150 fpm with your piston speed, so you wouldnt be losing much reliability at all with the stroked motor.

Is there any other variable besides piston speed that contributes to stress on the motor?? Maybe we can get some drag racers to chime in.
For a given piston velocity, stroke and revs are inversely proportional.
You are gaining 3% displacement but dropping max rpm by 3%. By that theory why wouldnt we just increase stroke by 10% and drop revs by 10%? There are alot more variables going on. In general you want the biggest bore you can use for any given displacement hence the shortest stroke.

I think in theory the 102mm crank is going to have a slightly fatter curve, shifted slightly to the left, all things being equal. So its going to depend on the shape of the curve, where the peak torque is and what kind of gearing used before we can determine what motor will be "better". Its not a guarantee the 102mm is going to be "better". Then there is tons of other variables, R/S ratio, piston side loading, piston dwell time and how it and the head effect each other etc
 

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I just started looking into this since I'm being forced to shift into 5th in the 1/4 mile. I found this deal someone put together when I did a google search.

"Found this list on another site - thought I'd pass it along

Honda has 6 of the top 10

1. Honda S2000:
Engine Code: F20C1
Bore/Stroke: 3.43" X 3.31" (Edit: 87.122mm x 84.074mm)
Redline: 9000rpm
Piston Speed: 4965 Ft/min

2. Lamborghini Gallardo
Engine Code: N/A
Bore/Stroke: 3.25" X 3.65" (Edit: 82.55mm x 92.71mm)
Redline: 8000rpm
Piston Speed: 4866.67 Ft/min

3. Acura Integra Type R
Engine Code: B18C5
Bore/Stroke: 3.19" X 3.43" (Edit: 81.026mm x 87.122mm)
Redline: 8400rpm
Piston Speed: 4802 Ft/min

4. BMW M3 (Germany)
Engine Code: S54
Bore/Stroke: 3.43" X 3.58" (Edit: 87.122mm x 90.932mm)
Redline: 8000rpm
Piston Speed: 4773.33 Ft/min

5. Honda S2000 2004
Engine Code: F22C
Bore/Stroke: 3.43" X 3.57" (Edit: 87.122mm x 90.678mm)
Redline: 8000rpm
Piston Speed: 4760 Ft/min

6. Honda Integra Type R (JDM)
Engine Code: K20A
Bore/Stroke: 3.39" X 3.39" (Edit: 86.106mm x 86.106mm)
Redline: 8400rpm
Piston Speed: 4746 Ft/min

7. Acura Integra GSR 2001
Engine Code: B18C
Bore/Stroke: 3.19" X 3.43" (Edit: 81.026mm x 87.122mm)
Redline: 8200rpm
Piston Speed: 4687.67 Ft/min

8. Saleen S7
Engine Code: N/A
Bore/Stroke: 4.13" X 4.00"
Redline: 7000rpm
Piston Speed: 4666.67 Ft/min

9. Acura TSX
Engine Code: K24A2
Bore/Stroke: 3.43" X 3.90" (Edit: 87.122mm x 99.059mm)
Redline: 7100rpm
Piston Speed: 4615 Ft/min

10. Suzuki Hayabusa Sport Prototype
Engine Code: W701
Bore/Stroke: 3.19" X 2.48"
Redline: 11000rpm
Piston Speed: 4546.67 Ft/min

11. Honda Civic Type R
Engine Code: B16B
Bore/Stroke: 3.19" X 3.03" (Edit: 81.026mm x 76.961mm)
Redline: 9000rpm
Piston Speed: 4545 Ft/min

12. Toyota Celica GTS / Matrix XRS 2001
Engine Code: 2ZZ-GE
Bore/Stroke: 3.23" X 3.35"
Redline: 8100rpm
Piston Speed: 4522.5 Ft/min

13. Honda Prelude Type S (JDM)
Engine Code: H22A
Bore/Stroke: 3.43" X 3.57" (Edit: 87.122mm x 90.678mm)
Redline: 7500rpm
Piston Speed: 4462.5 Ft/min

14. Acura RSX Type S
Engine Code: K20A2
Bore/Stroke: 3.38" X 3.38" (Edit: 85.851mm x 85.851mm)
Redline: 7900rpm
Piston Speed: 4450.33 Ft/min

15. Ferrari 360 Modena (incl. Challenge, Stradale, etc)
Engine Code: N/A
Bore/Stroke: 3.35" X 3.11"
Redline: 8500rpm
Piston Speed: 4405.83 Ft/min

16. Lamborghini Murcielago
Engine Code: N/A
Bore/Stroke: 3.43" X 3.42"
Redline: 7600rpm
Piston Speed: 4332 Ft/min

17. McLaren F1
Engine Code: N/A (BMW V12)
Bore/Stroke: 3.39" X 3.43"
Redline: 7500rpm
Piston Speed: 4287.5 Ft/min

18. Renault Clio 2.0 RS 2003
Engine Code: F4R
Bore/Stroke: 3.26" X 3.66"
Redline: 7000rpm
Piston Speed: 4270 Ft/min

19. Porsche 911 GT3 RS 2004
Engine Code: N/A
Bore/Stroke: 3.94" X 3.01"
Redline: 8500rpm
Piston Speed: 4264.17 Ft/min

20. Pagani Zonda C12S
Engine Code: M120 7.3 AMG
Bore/Stroke: 3.6" X 3.64"
Redline: 7000rpm
Piston Speed: 4246.67 Ft/min

21. Peugeot 206RC 2004
Engine Code: EW10 J4 S
Bore/Stroke: 3.35" X 3.46"
Redline: 7300rpm
Piston Speed: 4209.67 Ft/min

22. Porsche Carrera GT
Engine Code: N/A
Bore/Stroke: 3.86" X 2.99"
Redline: 8400rpm
Piston Speed: 4186 Ft/min

23. Acura NSX-T
Engine Code: C32B
Bore/Stroke: 3.66" X 3.07" (Edit: 92.964mm x 77.978mm)
Redline: 8000rpm
Piston Speed: 4093.33 Ft/min

24. BMW M5 2002
Engine Code: S62
Bore/Stroke: 3.70" X 3.50"
Redline: 7000rpm
Piston Speed: 4083.33 Ft/min

25. BMW M5 E60
Engine Code: S65 (?)
Bore/Stroke: 3.62" X 2.96"
Redline: 8250rpm
Piston Speed: 4070 Ft/min

26. Nissan Primera W20V
Engine Code: N/A
Bore/Stroke: 3.39" X 3.39"
Redline: 7200rpm
Piston Speed: 4068 Ft/min

27. Ferrari Enzo
Engine Code: F140
Bore/Stroke: 3.62" X 2.96"
Redline: 8000rpm
Piston Speed: 3946.67 Ft/min

28. Ferrari 575 Maranello
Engine Code: 650 V21
Bore/Stroke: 3.50" X 3.03"
Redline: 7750rpm
Piston Speed: 3913.75 Ft/min"
 

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i noticed the TSX with a red line at 7100 is at 4615 ft/pm what would it be at 7500 rpm and is this the same as k24a1??? just wanna know how high i can go with my build since its all stock oem bottom end and i plan on using a2 head on top. i already know i cant take it to 8200 reliably and have it last but i WANT to keep it for a while
 

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i noticed the TSX with a red line at 7100 is at 4615 ft/pm what would it be at 7500 rpm and is this the same as k24a1??? just wanna know how high i can go with my build since its all stock oem bottom end and i plan on using a2 head on top. i already know i cant take it to 8200 reliably and have it last but i WANT to keep it for a while

A lot of people rev to 8k regularly without problems (so they say). At that point, it's not your bottom end that limits rpm, it's the oil pump. The stock k24 pumps will cavitate at a lower rpm than a type s oil pump will. I'm not sure what the limit of the bottom end is (I think the rods are the weak point), but it's definitely higher than the limit of the k24 oil pump
 
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