Thanks for the learning

 

Hey Folks!

I just got my first oil change on my S2000 yesterday. Out of curiosity, because of all the "is there any difference between the MY00-MY03 and MY04+" cylinder head / valves / springs questions, I went to the parts counter and asked the guy to look up the part numbers on the MY03 and MY04 valve springs and cam shafts.

FYI, the MY03 and MY04 intake valve springs and intake cams are not the same part number. Obviously, the parts guy couldn't tell me what the technical spec difference was, only that the 2.0 and 2.2 engine don't call for the same part numbers. This may or may not mean there's an actual difference between the components. It wouldn't be the first time that a manufacturer superseded a part number. I didn't think to ask if that might be the case. OTOH, it might be a good reason to be absolutely sure of what you're doing before trying to spin a 2.2 engine to 9k!

FWIW!

Drive Safe,
Steve R.

 

2003 S2000:


205775 (<----part #) 005 8 SPRING, IN. VALVE

2004 S2000:


1301526(<---- part #) 005 8 SPRING, IN. VALVE (WHITE) (NIPPON HATSUJO)



however the valves themselves have the same part numbers. i'm guessing that honda chose to use less resistant valve springs since the redline was brought down to 8k(for 2004+ models).

 

Ok so I recall that the cams had been changed on the MY04 before. This was a while ago so I'm not 100% sure of this(i.e. someone pipe in if they know), but if I recall, the MY04 cams were changed to alter the flow characteristics(can't say optimize but it wouldn't surprise me). The MY00-03 cams were designed to take advantage of 'swirling' at certain RPMs and the took this out for the MY04 because they didn't need too(and I assumed the cam changes allowed it to flow better at other RPMS)

I'm sure someone else knows more since I thought that this came up here before.

 

Which is something I speculated about in my first post to this conversation!

Drive Safe,
Steve R.

 

actually they changed the cam profiles which may have required a change in springs to properly actuate them. It's not clear that the springs are weaker/stronger or the same.

I would be willing to argue that they are the similar responsive springs for the following reason. One additional advantage of the 8.2K limit is that in the event of an overrev, the valvetrain must be overrev further to cause a valve float. If float still occurs at 10.7K then you have 2.5K of overrev instead of just 1.6K for the 2.0L

While overrev isn't a specific cost since it is 'owner abuse', it does play into the image of reliability of the car. If they can eliminate overrevs then the S2K's reliability reputation will be enhanced.

 

Remember when Toyota lowered the redline in the Celica GT-S because EVERYBODY was over-reving the engines? Kinda sucked for the ones with newer cars...

 

Good point, Crazy!

You may well be right. OTOH, if Honda felt that a 1.6k buffer was good enough for the 2.0, they "might" think it's good enough for the 2.2 and get another .5% (*) increase in engine efficiency due to less restrictive valve springs. Honda worked hard to reduce internal friction on the 2.0 so it would be more reliable at engine speeds between 8-9k rpm. I don't think it's a leap to consider that Honda would jump at the chance to improve the 2.2's internal friction numbers with a relatively easy change such as lightening the valve springs. The problem is, the only one that can "really" answer this question is Honda itself.

Hey Honda, care to shed any light??

Drive Safe,
Steve R.

(*) for clarification, .5% is just a number I made up to use as an example. This whole point could be (and probably is) totally moot!