PedalFaster

Someone posted some fairly detailed Honda internal literature to S2000 Talk:
https://www.s2ki.com/forums/showthread.php?...25&pagenumber=2. The post is a goldmine of racing-relevant information. Highlights:

• More torque but lower redline
  
• Wider 17" wheels
  
• Shorter gearing (due to a numerically higher primary gear reduction)
  
• Rear sway bar softened
  
• Transmission, differential, and chassis strengthened
  
• Slower steering
  
• Incrementally higher curb weight

Details (quoted from the literature):

• "240-hp @ 7800 rpm, 161 lb.-ft. @ 6500 rpm"
  
• "there is more horsepower available at a lower rpm than the 2.0-liter engine, all the way to the new 8000 rpm redline. [...] Maximum torque output now reaches 161 lb.-ft. at 6500 rpm compared to the previous engine's 153 lb.-ft. at 7500 rpm. While this may only indicate an increase of 8 foot-pounds, in real-world driving, where the rpm generally hovers around 4500, the 2004 engine produces around 15 more foot-pounds of torque than the 2003 engine at the same rpm range."
  
• Low-resolution engine output chart on this page: http://flex.com/~slickyv/s2k6.jpg
  
• "The S2000 features P215/45 R17 87W front tires, mounted on new 17-inch x 7-inch alloy wheels. The rear tires are P245/40 R17 91W and are mounted on new 17-inch x 8.5 inch alloy wheels." (versus 6.5" and 7.5" on the '00-'03 models)
  
• "Transmission gear ratios:
  1st: 3.133 (vs. 3.133 on '00-'03 cars)
  2nd: 2.045 (vs. 2.045 on '00-'03 cars)
  3rd: 1.481 (vs. 1.481 on '00-'03 cars)
  4th: 1.161 (vs. 1.161 on '00-'03 cars)
  5th: 0.942 (vs. 0.971 on '00-'03 cars)
  6th: 0.763 (vs. 0.811 on '00-'03 cars)
  Reverse Gear: 2.800 (vs. 2.800 on '00-'03 cars)
  Secondary Gear Reduction: 1.208 (vs. 1.160 on '00-'03 cars)
  Final Drive: 4.100 (vs. 4.100 on '00-'03 cars)"
  
• "In 2004, in order to improve bump steer and cornering characteristics, the rear stabilizer bar was decreased by 1.8 mm to 25.4 mm while the front remains at 26.4 mm."
  
• "For 2004, the differential was strengthened by 20% and overall rigidity increased by 40%"
  
• "For 2004, the brass synchronize (sic) rings have been replaced with a carbon material. This has improved load capacity, abrasion resistance, reliability and overall shift feel."
  
• "The transmission case rigidity has been improved for 2004."
  
• "For 2004, structural reinforcements were added to the front frame end, the front upper arm support point, the front crossmember and the rear bulkhead."
  
• "Steering Wheel Turns, Lock-to-Lock: 2.6" (vs. 2.4 before)
  
• "Steering Ratio: 14.9" (vs. 13.9 before)
  
• "Curb Weight (lbs.): 2835" (vs. 2810 for the '03)

My editorial comments (slanted towards autocross):

• The shorter first gear will probably make shifting to first in autocrosses infeasible; hopefully the shorter second gear and increased torque will make it unnecessary
  
• The wider wheels should help, but extra weight is a concern, especially if there is no lightweight option (analogous to the '00-'03 JDM wheel) available
  
• A second reduction in rear sway bar stiffness (it was reduced in the '02 model year) coupled with the wider rear wheels may mean the giant 1.25" solid front sway bars currently in vogue for the '00-'03 cars will be too much for the new car; the optimal '04 setup may differ from the optimal setup for the earlier cars
  
• The diff and chassis strengthening should be a win given the failures documented on this forum
  
• The curb weight gain is small enough to be a wash

Overall, while the normal disclaimers about actually driving the car apply, the '04 model would seem to be an improvement to me, albeit an incremental one. Anyone else have thoughts?

Steve

PedalFaster

Replying to myself since no one else did...

For what it's worth, Tire Rack has a small selection of 17x7 and 17x8.5 wheels that fit the S2000: http://www.tirerack.com/upgrade_garage/Whe...0&autoYear=2001. They don't have any matching sets in the right widths, but they do have some O.Z. fronts that weigh 15.9 pounds each, and some BBS rears that weigh 17.5 pounds each. Compare these weights to 18.0/19.5 for the 16" USDM wheels, and 13.5/14.4 for the 16" JDM ones.

Not sure about the offsets on these, but spacers or some machining can do wonders there. Front brake clearance (after offset adjustments, if required) is likewise an open question.

Steve

matrix

This one is interesting - I find that to be quite a high percentage for only a small increase in torque....

matrix

I also find it interesting that the gear ratio for the first 3 gears has not changed. I think I would rather have the rpm range over the small torque increase. Only time will tell...

mgiang7

[QUOTE]Originally posted by PedalFaster
[B]Replying to myself since no one else did...

ultimate lurker

On paper I'd definitely say the 04 looks good for auto-x. For open track work, its a wash, unless Honda underrated the engine (which wouldn't surprise me to avoid pissing off existing owners).

The shorter gearing (thanks to the deeper reduction gear 1.2 vs. 1.16) and additional torque should provide improved off corner acceleration. Still shouldn't need to get out of 3rd gear in an auto-x. Combined with theoretically improved traction (wider wheels, etc.) that should help.

I would like to have the tranny and diff though. The tighter reduction gear means the standard 4.10 rear end will behave more like a 4.30. And the taller 6th means I could still drive to the track in some aural comfort. And more strength is a good thing.

UL

payneinthe

[QUOTE]Originally posted by ultimate lurker
[B]The shorter gearing (thanks to the deeper reduction gear 1.2 vs. 1.16) and additional torque should provide improved off corner acceleration.

matrix

UL (or anyone else), can you explain how the reduction gear works with the individual gears?

Windscreen

It's probably easiest to think of the reduction gear as a black box between the transmission and the differential. It is another gearset that reduces speed/multiplies torque. For the overall ratio between engine and wheels: gear ratio * reduction gear * differential ratio.

I believe the reduction gear design is due to Honda's familiarity with front wheel drive transaxle design, as applied to a longitudinal transmission. The reduction set is where the differential would be in a FWD transaxle, I think (but I'm not much up on FWD transaxle design).

PedalFaster

I'm not sure if this was intended solely as a response to the increased torque -- experience (others' experience, thankfully for me) at ProSolos and the drag strip seems to show that the original tranny's not strong enough to withstand the repeated high-rpm launches required to get an S2000 off of the line quickly.

Something doesn't quite jive, though -- Honda added a bunch of reinforcements and 17" wheels and the curb weight only went up by 25 pounds? I wonder if they removed weight elsewhere.

Offset must be within a quarter inch of stock. What I meant to say was that the wheels shown by Tire Rack are known to fit the pre-'04 S2000, but may not necessarily have offsets within 0.25" of the '04 OEM wheel. That can be corrected by adding spacers or alternately machining material off of the wheel mounting face, but the latter could place the wheel spokes too close to the brake calipers.

[QUOTE]Originally posted by payneinthe
[B]I've never been IN to 3rd gear at an auto-x.