RPM / redline over-rev codes

[nytehawk]

Do any of you know if the S2K's ECM (computer) stores information about how high the engine has been revved, if it has ever been limited by the rev limiter, and particularly if it has ever exceeded the rev-limiter? (Say, with one of those infamous 5 --> 2 downshifts...) If so, can those codes be accessed via a normal Can OBD II diagnostic tool, or can they only be accessed with Honda's proprietary Honda Diagnostic System?

Reason for asking is that my S2K has never hit the rev-limiter or been over-revved...as far as I know. But it did have just over 100 miles on it when I took delivery, so I'd like to know if my car has ever been rev-limited or over-revved because it must have happened before I purchased it.

I asked my dealer about this when I took the car in a while ago, but based on their response I don't think they really even understood what I was asking.

Thanks!

[Randy W]

how many miles do you have on the car now?
and what symptoms lead you to believe it was an overrev?

[My_yella_s2k]

the mechanical overrev is stored in the computer for as long as the CEL is on.
once the CEL is cleared, all memory along w./ it goes too.

[nytehawk]

Thanks guys for the quick responses!

how many miles do you have on the car now?
and what symptoms lead you to believe it was an overrev?

I expect to turn 3,000 miles today. No reason or symptoms leading me to believe the car was ever over-revved -- I'd just like to know for sure!

the mechanical overrev is stored in the computer for as long as the CEL is on.
once the CEL is cleared, all memory along w./ it goes too.

Okay, so the CEL will come on if the vehicle is over-revved, therefore chances are that it's never happened. (I have no reason to believe my CEL has ever come on or been cleared.)

Assuming the dealer did not clear my ECM prior to delivering the car, is there any way to check it to determine if the rev-limiter has been activated? (2007 S2k, AP2)

[Randy W]

If it was overreved, and caused damage, what happens is the valves will be bent, causing the engine to stutter, and sound not right at all. You can even feel the difference out of the exhaust.

If the CEL comes on from an overrev and then cleared, it will come right back if the damage has been done.

[My_yella_s2k]

Thanks guys for the quick responses!
Okay, so the CEL will come on if the vehicle is over-revved, therefore chances are that it's never happened. (I have no reason to believe my CEL has ever come on or been cleared.)

Assuming the dealer did not clear my ECM prior to delivering the car, is there any way to check it to determine if the rev-limiter has been activated? (2007 S2k, AP2)
That's what we're here for :thumbsup:

unfortinitly, there is no way to see if the rev limiter has been activated, and after looking at some info, i dont see a code for "mechanical over rev" either..... it should be
P0219 Engine Overspeed Condition

[Geo02s2k]

Thanks guys for the quick responses!



I expect to turn 3,000 miles today. No reason or symptoms leading me to believe the car was ever over-revved -- I'd just like to know for sure!



Okay, so the CEL will come on if the vehicle is over-revved, therefore chances are that it's never happened. (I have no reason to believe my CEL has ever come on or been cleared.)

Assuming the dealer did not clear my ECM prior to delivering the car, is there any way to check it to determine if the rev-limiter has been activated? (2007 S2k, AP2)

I wouldn't worry about the rev limiter. It is there to do exactly what it sounds like, limit the revs to a safe level by shutting off the fuel. As long as it wasn't mechanically over-revved (which it doesn't sound like it was), you're fine. (You've also still got 33,000 miles of warranty. ;) )

[My_yella_s2k]

(You've also still got 33,000 miles of warranty. ;) )
i believe 06 + has 50k powertrain warr.... or possibly 60, i forget...
but, like stated above, i wouldnt worry

[nytehawk]

Thanks again to all for the informative feedback! (And yes, my '07 has 5 yr / 60k mi powertrain warranty; don't know about '06.)

On a semi-related but slightly off-topic note...
Going into the dealer tomorrow for first oil change and diff fluid change at 3,000 mi. Thanks to information from folks on this forum, I ordered the diff fill/drain washers in advance so they would have in stock and don't reuse the existing ones (though I recall XViper says you can). Also verified that they are willing to use the Mobil1 75w90 that I purchased in advance - with no warranty voiding concerns.

Gave the dealer a simple test by calling the parts dept and asking what diff fluid they recommend for the S2k and both parts guys knew immediately from memory that it requires SAE 90 gear oil. This particular dealer carries 80w90 gear oil purchased in bulk from an unspecified mfr. After reading the concerns in this forum about dealers putting CR-V fluid in the S2k, it was good to hear these guys give the right answer without having to look it up.

[s2kobsessed]

doesn't the owners manual suggest that the original OIL be left in the engine for longer than normal change intervals?

something about more moly in the original oil or something? Could just be a farce too though.

[Geo02s2k]

doesn't the owners manual suggest that the original OIL be left in the engine for longer than normal change intervals?

something about more moly in the original oil or something? Could just be a farce too though.

This is what I've been thinking. Either way, 3000 miles is a bit early for either the rear diff or the oil. Just my :twocents:

[nytehawk]

Yeah, the owner's manual does say not to change the oil early. There are quite a few threads on this with many opinions offered in all different directions. I spoke with a Honda factory service rep from their Torrance (California) facility who did say I should leave the original oil in for at least 3k miles. I'm in a slightly weird situation in that the car was first delivered to a dealer in Jan '07, so my oil is 15 months old but only 3,000 miles old. So, I figured doing the first oil change at 3k miles was a good compromise between age and mileage. My oil minder currently says 50% oil life, but if I wait until 6k miles that means the oil will have been in the engine nearly two years at my current rate. Any thoughts?

Also, I think it was XViper who wrote in one thread on differential fluid that doing the very first change after 2k miles (then going to the recommended 15k mile interval) is a good idea to remove any initial wear-in debris. Yes, here's the thread: http://forums.s2kca.com/showthread.php?t=19839. Scroll down to repiv's post 12/19/07 at 09:07am.

[tomauto]

Yeah the yearly change interval should be fine for you. Good call on the early diff fluid change, you have been reading well. Lets hope you can change the oil a couple more times this coming year!

[repiv]

doesn't the owners manual suggest that the original OIL be left in the engine for longer than normal change intervals?

something about more moly in the original oil or something? Could just be a farce too though.
I don't believe the owner's manual states anything with reference to this, but if you find it, please let us know what page it's on.
This whole business about the first oil pertained to NOT switching to synthetic too early on AP1 engines due to the fact that many of them consumed oil during the break in period, which could last to 10K miles. Honda issued some sort of memo to dealers to advise S2000 owners to stay with "dino" oil till at least 7500 miles. At no time did they say you couldn't switch, only that switching to synthetic could prolong the break in process. This didn't mean it would harm the engine in any way and in fact, many owners started using synthetic early with no detriment to the engine. When the 2.2L engine came along in the AP2, Honda resolved much of this oil burning issue, but never rescinded the memo. It didn't really matter, because not switching to synthetic was not an issue, so Honda didn't push the issue. Over the years, dealers and S2000 owners alike, both got this concept all screwed up and bent out of shape and it evolved into some of the goofy ideas we hear about now.
Insofar as the high moly content in the factory fill, this was not an intentional addition for the sake of adding moly to the oil. It was simply the high moly in the assembly lube which all engines are put together with. There was NO special factory fill. Even Honda tried to put this notion out there to persuade early owners to not go synthetic too soon. I know for a fact that an S2000 engine that is rebuilt at a dealership, then have "off the shelf" oil put in will analyze with the same moly content as so called "factory fill". Guess what? It came from the assembly lube. There is NO magic Pixie Dust in factory S2000 oil. Again, this got bent and twisted by impressionable people over the years into thinking Honda put some kind of magic potion into their oils.
It might interest you to know that a couple of years ago, Acura division addressed this whole "factory fill" mythology and issued an official statement to say "THERE IS NO SUCH THING"!
As informed car enthusiasts, let's not perpetuate such myths as there will always be "impressionable" car owners arriving on the scene every day. Let S2000 owners be the smarter ones and set people straight.

[repiv]

Also, I think it was XViper who wrote in one thread on differential fluid that doing the very first change after 2k miles (then going to the recommended 15k mile interval) is a good idea to remove any initial wear-in debris. Yes, here's the thread: http://forums.s2kca.com/showthread.php?t=19839. Scroll down to repiv's post 12/19/07 at 09:07am.

Thank you for listening. Yes, that first rear diff fluid change is very important. It gets all that break in crud out. Your rear diff will thank you years down the road. Our cars have a very small diff for what it's asked to do. The fluid in it may be the only thing standing between a long life and premature extinguishment.

BTW, as far as I know, all S2000 prior to the ones with DBW did not record any codes for over-revs or rev limit hits. The latest models, I can't say for sure.

[Jasonoff]

If it was overreved, and caused damage, what happens is the valves will be bent, causing the engine to stutter, and sound not right at all. You can even feel the difference out of the exhaust.Not entirely.

The valve can check in the retainer and not show any symptoms for many many miles.

[Geo02s2k]

Thanks for setting the record straight, Dave. I have read many of the posts on this and the other forum, but apparently not the right ones. Good call on the fluid changes. I knew someone with more knowledge than I would chime in.

[nytehawk]

I don't believe the owner's manual states anything with reference to this, but if you find it, please let us know what page it's on.

Thanks Repiv for your replies regarding both the engine oil and diff fluid; I'm sure I speak for many when I say that your knowledge and wisdom are greatly appreciated.

The statement in my 2007 owner's manual about not changing the engine oil early is on page 110. Underneath the "Break-in Period" heading, it states that the break-in period is 600 miles, then says, "During this period:" and lists 3 bullet points. The 2nd of those 3 bullet points is, "Do not change the oil until the scheduled maintenance time." Now, does that mean don't change the oil during the 600 mile break-in period, or does it mean don't change the oil until the maintenance minder indicates it needs to be changed? I see how it could be argued either way...

However, I also recently purchased the official 2000-2007 Honda S2000 service manual published by Helm. In the maintenance section for the '06-'07 S2k, it states that if the maintenance minder does not indicate the need for service within 12 months (i.e. the car has not been driven enough miles to require it) that the engine oil should be changed every 12 months. (Also says brake fluid should be changed every 3 yrs regardless of the maintenance minder.) The maintenance instructions for '00-'05 S2k in this service manual also state that the oil should be changed (under normal, not severe, service intervals) every so many miles or 12 months.

Hence -- at least as best I can tell -- getting my first oil change this weekend at 3,000 miles and 14 months since the dealer received my S2k (5 months since I purchased it) seems about as reasonable as it's gonna get. And my diff fluid is definitely getting replaced with Mobil1 75w90 -- no question about that.

Thanks once again to everyone who has helped answer my questions!

[Geo02s2k]

In my original post, I didn't realize you'd had your car for as long as you have. The oil change interval is an either or between mileage and time. With 15 months on its clock, it's due. (I put 12-15k on my car every year, so time is NEVER a factor. :laugh: )

[repiv]

The statement in my 2007 owner's manual about not changing the engine oil early is on page 110. Underneath the "Break-in Period" heading, it states that the break-in period is 600 miles, then says, "During this period:" and lists 3 bullet points. The 2nd of those 3 bullet points is, "Do not change the oil until the scheduled maintenance time." Now, does that mean don't change the oil during the 600 mile break-in period, or does it mean don't change the oil until the maintenance minder indicates it needs to be changed? I see how it could be argued either way...

However, I also recently purchased the official 2000-2007 Honda S2000 service manual published by Helm. In the maintenance section for the '06-'07 S2k, it states that if the maintenance minder does not indicate the need for service within 12 months (i.e. the car has not been driven enough miles to require it) that the engine oil should be changed every 12 months. (Also says brake fluid should be changed every 3 yrs regardless of the maintenance minder.) The maintenance instructions for '00-'05 S2k in this service manual also state that the oil should be changed (under normal, not severe, service intervals) every so many miles or 12 months.

Hence -- at least as best I can tell -- getting my first oil change this weekend at 3,000 miles and 14 months since the dealer received my S2k (5 months since I purchased it) seems about as reasonable as it's gonna get. And my diff fluid is definitely getting replaced with Mobil1 75w90 -- no question about that.

Thanks once again to everyone who has helped answer my questions!

The "600 mile break in" more refers to watching your maximum rpm during that time. IE, don't exceed xxxx rpm and avoid constant rpm till you've put on 600 miles. This is pretty typical of Honda doctrines for their cars and motorcycles.
Honda also seems to have put a lot of credence upon their "oil minder" on their latest cars. This may be partly to do with marketing in that Honda wants everyone to know that they are producing very low maintenance cars. IMO, I see it as not so much "Don't change your oil", but more that "You don't have to change the oil till the oil/maintenance minder says so". Honda wants you to know that their cars are THAT good that you can trust the car to tell you when something is needed.
Most oils have a time constraint in that if the car isn't used enough to generate an "average" amount of miles, the oil should be changed at 12 months. This is getting back to the "mileage or time", whichever comes first. Realize that once oil is unsealed from the bottle and run in an engine (even for a short amount of run time), oxidation of the additives begins. I guess the current state of oil technology would indicate that 12 months is the time frame that the additives in oil reaches a critical level of viability that it can't be trusted any further, not so much for lubrication, but for things such as anti-corrosion and buffering capacities.

Some "experts" might tell you that you can change your engine oil too much. Whether you believe this or not is everyone's own choice. I've not seen any evidence to indicate that you can kill a car engine by changing the oil too much. Again, IMO, changing car oil a lot only wastes your own money and as far as what anyone else thinks, it's really none of their business. Having said this, I've also seen documented proof (used oil analysis) using "dino" oil in an S2000 that showed there was plenty of oil life left after 7500 miles. I used to be one of those who changed the oil every 3000 miles. I now change it once a year and I might put on 6000 to 7000 miles. If I've driven the car particularly hard for a significant period of time or if I plan on a lengthy road trip, I'll change the oil for peace of mind.

[repiv]

Not entirely.

The valve can check in the retainer and not show any symptoms for many many miles.

Then, for no apparent reason, go ............................. BOOM! Or, you'll have no problems, sell it and the next poor booger has it go BOOM!

Keep in mind that the valvetrain can technically survive short forays up to 11,000 rpm. On the other hand, it can sustain damage even if it never gets beyond 9000 rpm if the "rate" of sudden rpm increase is extremely rapid.

[Jasonoff]

Then, for no apparent reason, go ............................. BOOM! Or, you'll have no problems, sell it and the next poor booger has it go BOOM!

Keep in mind that the valvetrain can technically survive short forays up to 11,000 rpm. On the other hand, it can sustain damage even if it never gets beyond 9000 rpm if the "rate" of sudden rpm increase is extremely rapid.I believe the magic "valve float" number is 10,400 RPM on the AP1?

It's not all that hard to check your valves either. I will be checking mine soon when I do my adjustment so I can post a How To if there's not one already here.

[repiv]

I believe the magic "valve float" number is 10,400 RPM on the AP1?You have more precise info than me, J. I guess I rounded up to far.:duh:

[nytehawk]

Well guys, my S2k now has a fresh load of Honda 10w-30 motor oil and Mobil1 75w-90 synthetic in the diff so I'm ready to rev it up and go hit the twisties. They gave me both old diff washers and the remaining gear oil sealed in a plastic bag so it wouldn't get on the inside of my car; looks like they did a superb job! For any S2k owners in the Victor Valley region of Southern CA, I highly recommend service advisor JoAnn Macaluso at Valley-Hi Honda in Victorville. They have taken excellent care of me for all our Honda vehicles.

Back to the over-rev topic: does anyone know the "valve float" rpm for the AP2 motor?

[Jasonoff]

You have more precise info than me, J. I guess I rounded up to far.:duh:Is this what I get to look forward to when I get older? :p :poke:

[Jasonoff]

Back to the over-rev topic: does anyone know the "valve float" rpm for the AP2 motor?Right about where I shift in my car. :D

Valve float will be the same as AP1 since it's "pretty much" the same system. AP2 does have stronger springs so it "may" even be higher.

In the AP2 you don't technically need to worry about valve float since they can handle more RPM than your pistons can due to the larger stroke.

Search for some threads about people increasing redline in their AP2. I can't remember if it was here or s2ki that had a bunch of great info. Sorry I have an AP1 so I haven't taken much interest in it to know enough about it.

[dithersail]

Hey all apologies for dredging this thread up from the depths.

I was interested in how many of you hit the rev limiter (either intermittently or regularly. Accidentally or intentionally) and if anyone has suffered any ill effects from it - or suspected ill effects. Not a mechanical overrev. Understand the dangers of that certainly.

I have to admit that I hit the rev limiter on occasion during hard acceleration in first or second. Once today at a stoplight in first. Sometimes just a bit to hypnotized by the scream of the engine and Whoops! I have never given it a second thought, figuring that a 8K redline is there to be teased from time to time. I have noted that the ECU gives you a split second to shift after the red segment of the arc lights before the fuel shuts off. Honda's software guys intended it to be like a shift light, maybe? :devil:

You do have to go almost to the rev limiter to stay in vtec for the first 3 gears I have noticed. Probably 4 as well but by that point I am holding on for dear life and not watching the tach.

I don't think I pinned down if the ECU records these overrev events, though. Does it? Or just mechanical overs? Probably buried in a thread somewhere that I can't find.

I've never botched a shift from 5th to 2nd from 70, luckily, yet........

Very interesting.

[Coop]

I have hit the rev limiter once or twice :LOL:

but never an over-rev

[bwturner1951]

I've hit the rev limiter 3-4 times, all unintentionally. I find the fifth to fourth shift the most vexing for me and abashedly admit it as the cause of 1 of those over revs. :o I assume that the Honda engineers built in some safety tolerances and set the rev limiter at a point before any real damage could be done. Bad assumption maybe? :think:

Now, would someone kindly enlighten my mechanically challenged mind on what the difference is between a 'mechanical' over-rev and the 'other' kind of over-revs? :o

[repiv]

I've hit the rev limiter 3-4 times, all unintentionally. I find the fifth to fourth shift the most vexing for me and abashedly admit it as the cause of 1 of those over revs. :o I assume that the Honda engineers built in some safety tolerances and set the rev limiter at a point before any real damage could be done. Bad assumption maybe? :think:

Now, would someone kindly enlighten my mechanically challenged mind on what the difference is between a 'mechanical' over-rev and the 'other' kind of over-revs? :o
There is only one kind of "over-rev" (usually electronic but not necessarily so). Hitting the rev limiter by giving it gas is NOT an over-rev because it stops at the limiter. It doesn't go "over" it.
A "mechanical" over-rev is when you subject the motor to severe engine braking. This is caused when the drivetrain is all connected up (clutch engaged and tranny in gear) and the rear wheels drive the engine instead of the other way around. For example, if you are near or at redline while accelerating in 3rd and instead of going into 4th, you unintentionally throw it into 2nd. Because of the gearing, if you release the clutch and hook up the drivetrain, the rear wheels can spin the engine beyond its normal redline. In this case, outside forces are driving the engine instead of the engine doing the "driving".
When you over-spin the engine, things like valve springs can't keep up. They don't have enough strength to close the valve when the cam lobe no longer pressing down on the valve stem. The valve "floats". It stays in the cylinder long enough for the piston to come up and strike it. Additionally, the speed of the piston is so fast, that forces acting on things like wrist pins, "big ends", crank bearings, etc, exceed what they were designed to tolerate. Stuff wears and breaks.

I just realized that I need to put a condition on my explanation above. That condition is that we are talking about an S2000 or any modern day car with a built in "rev limiter". On cars without such a device, the engine can rev beyond the safe limits for engine speed because the manufacturer chose not to provide it. In this case, the engine would simply continue to rev as far as the amount of air/fuel is available. Such engines can and have been known to over-rev, float the valves and do some damage. In "non interference" engines (as opposed to "interference" engines where the top of the piston and the valve cup can occupy the same space under the right conditions like in valve float), damage is usually (but not exclusively) confined to areas subject to metal fatigue and those areas that are sensitive to excessive heat buildup where the oiling and cooling system can't dissipate it.

[dithersail]

So are either type recorded by the the ECU? Or does it just record excess RPM and not discern between the two?

[repiv]

So are either type recorded by the the ECU? Or does it just record excess RPM and not discern between the two?
It is my understanding that earlier S2000s did not retain such information but later S2000s did. I don't know when this happened. You'd have to ask someone with Honda.

[bwturner1951]

There is only one kind of "over-rev" (usually electronic but not necessarily so). Hitting the rev limiter by giving it gas is NOT an over-rev because it stops at the limiter. It doesn't go "over" it.
A "mechanical" over-rev is when you subject the motor to severe engine braking. This is caused when the drivetrain is all connected up (clutch engaged and tranny in gear) and the rear wheels drive the engine instead of the other way around. For example, if you are near or at redline while accelerating in 3rd and instead of going into 4th, you unintentionally throw it into 2nd. Because of the gearing, if you release the clutch and hook up the drivetrain, the rear wheels can spin the engine beyond its normal redline. In this case, outside forces are driving the engine instead of the engine doing the "driving".
When you over-spin the engine, things like valve springs can't keep up. They don't have enough strength to close the valve when the cam lobe no longer pressing down on the valve stem. The valve "floats". It stays in the cylinder long enough for the piston to come up and strike it. Additionally, the speed of the piston is so fast, that forces acting on things like wrist pins, "big ends", crank bearings, etc, exceed what they were designed to tolerate. Stuff wears and breaks.

I just realized that I need to put a condition on my explanation above. That condition is that we are talking about an S2000 or any modern day car with a built in "rev limiter". On cars without such a device, the engine can rev beyond the safe limits for engine speed because the manufacturer chose not to provide it. In this case, the engine would simply continue to rev as far as the amount of air/fuel is available. Such engines can and have been known to over-rev, float the valves and do some damage. In "non interference" engines (as opposed to "interference" engines where the top of the piston and the valve cup can occupy the same space under the right conditions like in valve float), damage is usually (but not exclusively) confined to areas subject to metal fatigue and those areas that are sensitive to excessive heat buildup where the oiling and cooling system can't dissipate it.

Very thorough explanation Dave. Thanks! Obviously, I need to get the 5th to 4th shift right from here on out. Sometimes I'm appalled by my own ignorance. :facepalm: But at least I know good teachers when I see (read?) them. :)

[bwturner1951]

The obvious follow-on question, for me anyway, is, how much tolerance did the Honda engineers build into the S2 engines to allow for a mechanical over-rev? This post by Billman250 from another thread may answer it assuming that the down-shift is done (accidentally?) at redline. Is that the correct underlying assumption? If so the answer to my question is 1700 rpm or is the answer more complex? :think:

<snip>
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.
<snip>

[mlc]

Wayne, do you know how fast you were going? I assume that you down shifted to second? How long was it before you pushed in the clutch?

Usually the biggest problem is the valve spring retainers will start to crack but not all the way. You drive several thousand miles and everything seems fine but the retainer is getting worse and worse and when it does let go it floats the valve and well bad things happen from there. Now the retainers on the AP2 like yours are MUCH stronger then on the AP1. As a matter of fact Billman250 recommends upgrading the AP1 retainer to the AP2. If you are really concerned then you can have the retainers inspected to see if they are cracked but have someone that knows what they are looking for do it, sometimes the cracks are hard to see for the untrained eye.

Kevin

[repiv]

The obvious follow-on question, for me anyway, is, how much tolerance did the Honda engineers build into the S2 engines to allow for a mechanical over-rev? This post by Billman250 from another thread may answer it assuming that the down-shift is done (accidentally?) at redline. Is that the correct underlying assumption? If so the answer to my question is 1700 rpm or is the answer more complex? :think:

<snip>
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.
<snip>
I believe we're dealing with 2 main issues here.
1. The rpm at which the S2000 valves will float. IE, the valve springs can no longer fully lift each valve before the cam lobe comes around and smashes it back down again, thereby sustaining a constant valve "open" state. Being in the "open" state at the wrong time in the engine's cycle causes the piston to try to occupy the same space as the valve cup at the same time. I've seen expert opinions that pegs this speed at around 10,500 rpm. This can vary with a stronger or weaker batch of valve springs.
You can calculate just how fast your engine was spun up by using a speed calculator such as this and extrapolating the engine rpm based on the speed at which you were going in the last gear your were in. This is assuming that you actually fully re-engaged the clutch so the driveline fully hooked up again.
http://www.turnzero.com/technical_resources.php?resource=gear_calculator
Just print the graph off and use a ruler to do the extrapolation.

2. I've always contended that it's not just the max engine speed that was reached but just as critical is the rate at which it got there. A mis-shift to a lower gear that doesn't go over redline can still do damage (on a more subtle condition) if the clutch was released suddenly without first blipping the throttle to better match revs. IE, you drive the engine to a much higher speed far more rapidly than it could normally drive itself. The accelerative forces of that rapid increase in rpm may be more than what the engine was built for. You may not float valves (or could you?) but you stand a good chance of fracturing metal parts (like retainers, bearings, etc.). Such damage may not manifest itself for a long time and many thousands of miles down the road.
Imagine you riding one of those single gear circus bicycles and your feet are strapped into the pedals. You are pedalling a slow and easy pace. Then your bike is propelled forward to the fastest that you could possibly pedal (and no faster) but it is done so rapidly that you don't have time to input any additional force. Sure, you're not having your legs move any faster than if you pedal like crazy on your own, but in this case, the pedalling is done for you and the change from slow to your max speed is very fast. Imagine what your knees and other joints are subjected to. You are not using your own muscles to "push" the pedals. The pedals are "pulling" your joints and bones and muscles instead. Do you suppose you could be injured?

[bwturner1951]

Wayne, do you know how fast you were going? I assume that you down shifted to second? How long was it before you pushed in the clutch?

Usually the biggest problem is the valve spring retainers will start to crack but not all the way. You drive several thousand miles and everything seems fine but the retainer is getting worse and worse and when it does let go it floats the valve and well bad things happen from there. Now the retainers on the AP2 like yours are MUCH stronger then on the AP1. As a matter of fact Billman250 recommends upgrading the AP1 retainer to the AP2. If you are really concerned then you can have the retainers inspected to see if they are cracked but have someone that knows what they are looking for do it, sometimes the cracks are hard to see for the untrained eye.

Kevin

My experience with a missed shift (5th to 2nd) happened last summer not long after I got the car and was experimenting with downshifting. I'm pretty sure that I was going between 55-65 mph in 5th so according to Dave's graph the lower end of my speed (55 mph) should have put me at around 7800 rpm and the upper end (65 mph) extrapolates to around 9230 rpm after the down shift. And, as Dave pointed out in his post, I always blip the throttle when I downshift so the rate of change should have been mitigated. But just to calm my fears, I'm tearing down the engine this Saturday and inspecting those spring retainers. Now where's that S2000 Repair for Dummies book? :D

Seriously guys, thanks for your very thorough responses to what I know are very elementary questions on this forum. :thumbup:

[bwturner1951]

I believe we're dealing with 2 main issues here.
1. The rpm at which the S2000 valves will float. IE, the valve springs can no longer fully lift each valve before the cam lobe comes around and smashes it back down again, thereby sustaining a constant valve "open" state. Being in the "open" state at the wrong time in the engine's cycle causes the piston to try to occupy the same space as the valve cup at the same time. I've seen expert opinions that pegs this speed at around 10,500 rpm. This can vary with a stronger or weaker batch of valve springs.
You can calculate just how fast your engine was spun up by using a speed calculator such as this and extrapolating the engine rpm based on the speed at which you were going in the last gear your were in. This is assuming that you actually fully re-engaged the clutch so the driveline fully hooked up again.
http://www.turnzero.com/technical_resources.php?resource=gear_calculator
Just print the graph off and use a ruler to do the extrapolation.

2. I've always contended that it's not just the max engine speed that was reached but just as critical is the rate at which it got there. A mis-shift to a lower gear that doesn't go over redline can still do damage (on a more subtle condition) if the clutch was released suddenly without first blipping the throttle to better match revs. IE, you drive the engine to a much higher speed far more rapidly than it could normally drive itself. The accelerative forces of that rapid increase in rpm may be more than what the engine was built for. You may not float valves (or could you?) but you stand a good chance of fracturing metal parts (like retainers, bearings, etc.). Such damage may not manifest itself for a long time and many thousands of miles down the road.
Imagine you riding one of those single gear circus bicycles and your feet are strapped into the pedals. You are pedalling a slow and easy pace. Then your bike is propelled forward to the fastest that you could possibly pedal (and no faster) but it is done so rapidly that you don't have time to input any additional force. Sure, you're not having your legs move any faster than if you pedal like crazy on your own, but in this case, the pedalling is done for you and the change from slow to your max speed is very fast. Imagine what your knees and other joints are subjected to. You are not using your own muscles to "push" the pedals. The pedals are "pulling" your joints and bones and muscles instead. Do you suppose you could be injured?

Clever and conclusive analogy Dave! :)

[mlc]

Here is a write up from Billman250 with some pics http://www.s2ki.com/forums/index.php?showtopic=483032&st=0&#entry10339300.

You might want to contact him and have a talk with him before hand. I am sure he can give you some good pointers on what to look for. He has probalby seen more cracked retainers then anyone else.

Good luck.

Kevin