Why from 9K to 8K?

[bwturner1951]

I've just finished reading the Evolution of the S2000 thread for the 2nd time and still find it a great read. http://www.conceptcarz.com/vehicle/z...nda-S2000.aspx

When the AP2 came out in 2004 the North American market models had the new F22CI engine. I understand lenghthening the stroke (as opposed to larger pistons?) because of higher cylinder displacement but why was the redline reduced from 9K to 8K? Was it to maintain some kind of mechanical equilibrium or was it simply a choice that the engineers made for performance (or other) reasons?

I'm sure this was probably covered in Mechanics 101 but I think I was asleep during that session of class. :sleeping: :D

[S2K-F8]

I'm pretty sure it was due to piston speed.

I'm also pretty sure that others (more technical than myself) can give you a better, more in depth answer.

Scott-

[dc_35]

piston speed is a good answer :thumbsup:

[dc_35]

interesting list of piston speeds from different cars ... it would see most car manufacturers try to stay around the same place.

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"

[Billman250]

Here's the lowdown on the 2.2L:

Goal: modify the engine to withstand a one-gear mechanical over-rev.

step 1: Lower the redline to 8k. This way a mechanical over rev will bring the engine to 9700 or so...which it can tolerate. At 9k, it will go to 10700 or more, which it can not tolerate.

2: add .2 liters to the engine, to make up for the loss in power

3: add about 10 lbs to the flywheel, to keep the engine spinning in it's now shorter powerband (6k-8k) between shifts

4: add the delay valve to the clutch slave cylinder, to allow the heavy flywheel the extra time it needs to decelerate between shifts (to avoid clutch burning)

[bwturner1951]

Here's the lowdown on the 2.2L:

Goal: modify the engine to withstand a one-gear mechanical over-rev.

step 1: Lower the redline to 8k. This way a mechanical over rev will bring the engine to 9700 or so...which it can tolerate. At 9k, it will go to 10700 or more, which it can not tolerate.

2: add .2 liters to the engine, to make up for the loss in power

3: add about 10 lbs to the flywheel, to keep the engine spinning in it's now shorter powerband (6k-8k) between shifts

4: add the delay valve to the clutch slave cylinder, to allow the heavy flywheel the extra time it needs to decelerate between shifts (to avoid clutch burning)

Awesome! The light bulb went on for me. If 1700 rpms is what one gear roughly increases/decreases the engine speed and 9700 rpms is the safe upper limit to prevent engine failure, bingo, 8K redline. Thanks for a great post/answer.

Now this begs the question, why did Honda feel it important to redesign the engine to withstand a 1 gear mechanical over-rev? Was something going on with S2 owners that prompted this or was it a more proactive modification on Honda's part (maybe racing inspired)? I'm getting this nasty vision of drivers down-shifting at 9K and trashing their engines. :yikes:

[Chris S]

Here's the lowdown on the 2.2L:

Goal: modify the engine to withstand a one-gear mechanical over-rev.

step 1: Lower the redline to 8k. This way a mechanical over rev will bring the engine to 9700 or so...which it can tolerate. At 9k, it will go to 10700 or more, which it can not tolerate.

2: add .2 liters to the engine, to make up for the loss in power

3: add about 10 lbs to the flywheel, to keep the engine spinning in it's now shorter powerband (6k-8k) between shifts

4: add the delay valve to the clutch slave cylinder, to allow the heavy flywheel the extra time it needs to decelerate between shifts (to avoid clutch burning)

Where did that conspiracy theory come from? If that was the case, the F22C would have been rolled out worldwide. Truth is that it was in response to Americans' preference for more torque. BTW, your rationale for 3 and 4 contradict each other. :poke:

[Billman250]

Heavy flywheel will maintain a given RPM longer.

Hence, it will take longer to decel. without the delay in the clutch, the RPM would remain too high for the next gear. Example: You would engage an engine spinning at 8k with a disc spinning at 7k, and it would slip. The flywheel needs the extra decel time to equalize engine/transmission speed.

[dc_35]

I highly doubt honda ever want a mechanical over rev to be "safe", piston speeds of an f20 going to 10700 and an a f22 going to 9700 are nearly the same.

f20 @10700rpm = 5897 FPM
f22 @ 9700rpm = 5772 FPM

no way that is "safe"

[FF2Skip]

FWIW, I used to have my sc'd 2.0L at 11:1 CR at a redline of 10k set by my AEM EMS. Blew a head gasket long before any internal damage. Bill can attest to this. :LOL:

[repiv]

Wow. Some really good responses here. I don't have much more to offer. Looking at everything posted so far, I see merit in several viewpoints.
dc_35's list is spectacular. Thanks for this. :thumbup:
Billman has some very good points and I'm not one to argue with him. Afterall, he is one of the foremost S2000 experts in existence today. Now, whether or not Honda had these reasons for doing what they did, only Honda will know for sure. Nevertheless, the outcome is as Billman pointed out.
My only contribution at this point is that "piston speeds" is an important consideration but may only be part of the equation. Remember that at the end of each stroke, the piston/rod assembly has to suddenly change direction and go in the opposite direction. The faster the thing is moving at the time, the more force is exerted on all the parts involved. As speeds increase, the forces at work, friction, etc increase logarithmically, not arithmetically. The last 1000 rpm of an F22 may see stresses equivalent to or more than the last 1000 rpm of an F20. We always tend to talk in terms of the amount of change (be it increase or decrease) but we often times forget about the rate of that change.