9000 rpm, unknown damage??

[AJKS]

So I was doing a dyno run with Nitrous with my 2002 NSX. In 4 th gear I reached 8000 rpm (end of dyno pull) with some tire spin on a Mustang Dyno. Not thinging any harm would come, like I have done 20 times in the past, I let go of the gas still in 4th gear. The tumblers on the dyno were spining faster than the tires, so when I let off the gas my NSX went to 9000rpm. I took it out of gear and did not notice any problems. I went out and drove the NSX for about 5 minutes and brought it up to 8000 RPM a few times and the NSX ran like a top. Any ideas of if there may be unknown damage?
The Dyno numbers were
274.3hp no Nitrous
Never got a good Nitrous pull it would spin everey time, but past runs have been 385hp

 

[NSX/MR2]

From the experiences that I have of my NSXes at over 8,000 rpm is like this: It will not hurt it as long as you don't do it continuously. Accident, but not on purpose. I have got a couple of mine passed 9,000rpm. However, like I said, "don't do it on purpose!" Because if you do it too much. One of these days, it will go passed 10,000 a COUPLE OT TIMES (not in one,) and that, my friend, above 10,000, that will hurt. Over all though, the NSX is stout. Freaking strong!

 

[satan_srv]

It's not really about being strong it's more about how good the valvesprings are. When you over-rev you risk floating the valves and then damaging them with the piston. If the car idles fine and powerband is smooth then you are likely fine. You could inspect the valves to be safe...but 9000rpms is likely fine...its 10,000 you gotta worry about

 

[Arata]

The tumblers on the dyno were spining faster than the tires, so when I let off the gas my NSX went to 9000rpm

How can the "tumblers" run faster than the car wheels are turning them??

 

[EndlessNA1]

Honda Motors are on of the most bulletproof motors. Before I upgraded the valvetrain on my motor I over reved to about 9k many times on the track downshifting and when I changed my valves and retainers there was no valve lash at all.

 

[EndlessNA1]

How can the "tumblers" run faster than the car wheels are turning them??

You could be accelerating hard on the dyno and before you reach redline you push clutch and take it out of gear, while that is happening the drums are still accelerating. Simple Physics.

HOWEVER

You should never remove from gear and then engage it again AT A HIGH SPEED. The car can hop off the dyno and there can be a serious accident as it puts more stress on the chasis straps. Instead wait until it slows down and start accelerating from a lower gear to do another pull. Or just take it out of gear and let the drums come to a complete stop. I've seen some scary stuff when the dyno has been used improperly

 

[Arata]

You could be accelerating hard on the dyno and before you reach redline you push clutch and take it out of gear, while that is happening the drums are still accelerating. Simple Physics.

So when you accelerating on the road and you push the clutch in, using the same "simple physics" the car will continue to accelerate?

 

[EndlessNA1]

So when you accelerating on the road and you push the clutch in, using the same "simple physics" the car will continue to accelerate?

sure... try it in first gear, accelerate hard and push in clutch. the car will still accerate to a certain mph then just continue rolling then start slowing down

 

[Autophile]

sure... try it in first gear, accelerate hard and push in clutch. the car will still accerate to a certain mph then just continue rolling then start slowing down

Sorry, but according to the equation F=MA, acceleration only occurs when there is a FORCE applied. All of the acceleration you think you get for free actually came from your engine while the clutch was engaged, simple enough.

 

[nsxprimetime]

quote:Originally posted by EndlessNA1

Actually, you're BOTH right.

If the clutch is depressed while the car is accelerating, it will continue to accelerate in NEUTRAL....that's because acceleration is a rate of change(of which speed is a derivative). If you're accelerating at a rate of, say, 10mph per second at the moment you pressed the clutch...the car WILL continue to accelerate because it HAS to pass through every possible rate of change between 10mph/sec and 0mph/sec before it can decelerate. If the rate of change was discontinuous, you would feel and incredible jolt when you pressed the clutch and began "decelerating".
So, the second you press the clutch, the car does continue to accelerate, but the RATE of acceleration begins to decrease IMMEDIATELY because, as AUTOPHILE said, there is no longer any FORCE being applied. A second or so later, the rate of change passes below zero and deceleration begins.

 

[RP-Motorsports]

PM "brahtw8" here on Prime, he just had his motor fixed in his NSX for a over-rev on the track.

 

[Larry Bastanza]

The weakest link is the oil pump gears. This is why Comptech makes the billet versions. There has been a few "overreved, now I have no oil pressure" sutiations, mostly at the track. aka the "MoneyShift".

My $.02,
LarryB

 

[EndlessNA1]

Actually, you're BOTH right.

If the clutch is depressed while the car is accelerating, it will continue to accelerate in NEUTRAL....that's because acceleration is a rate of change(of which speed is a derivative). If you're accelerating at a rate of, say, 10mph per second at the moment you pressed the clutch...the car WILL continue to accelerate because it HAS to pass through every possible rate of change between 10mph/sec and 0mph/sec before it can decelerate. If the rate of change was discontinuous, you would feel and incredible jolt when you pressed the clutch and began "decelerating".
So, the second you press the clutch, the car does continue to accelerate, but the RATE of acceleration begins to decrease IMMEDIATELY because, as AUTOPHILE said, there is no longer any FORCE being applied. A second or so later, the rate of change passes below zero and deceleration begins.

Couldn't have said it better.

 

[W]

The above does not explain why the rpm went to 9000.

I understand the continuous argument, but it doesn't apply to what we are talking about.

 

[NoSeX4U]

...it also doesn't explain how they get the caramel into a Caramilk bar...will mysteries never cease?!?

 

[EndlessNA1]

The above does not explain why the rpm went to 9000.

I understand the continuous argument, but it doesn't apply to what we are talking about.

Its not really a mystery. On the dyno there is a air brake. The brake can be set to a % of braking power during a pull, so the car basically accelerates likes its on the street. So if the brake has a low % then the wheels and drums will continue to "free spin". On a dyno the car doesn't have to pull its weight, just spin the tires.

 

[brahtw8]

PM "brahtw8" here on Prime, he just had his motor fixed in his NSX for a over-rev on the track.

I should PM you and tell you to stop bringing up bad memories . . .



T Bell is correct. My car saw approx. 10,500 RPM for a split second after a 3-2 shift at 110 MPH. The gear did not engage fully, and I caught it with the clutch in time to save the oil pump gears from shattering and the engine dropping its guts on the track.

On the way home I noticed a slight idle vibration and ticking noise. I had the car flatbedded to AoB and a top end rebuild ensued, to the tune of $4400 ($5400 w/o discount, and including a gearbox rebuild to replace a worn hub selector in 4th, among other things, which contributed to my driver error, call it 50% gearbox problems and 50% driver error/red mist).

So far so good on the rebuild. I wish you luck.

Quite frankly, if it had been another car I may not have been so lucky. Had the engine dumped its oil/contents, the car would likely have gone into a violent spin on the main straight at RA. Not fun.

 

[nsxtasy]

Speaking of bad memories...

a gearbox rebuild to replace a worn hub selector in 4th, among other things, which contributed to my driver error, call it 50% gearbox problems

The problem with a worn hub selector is documented in further detail in this topic and again in this topic.

The same hub selector is used for third gear and for fourth gear. If it gets worn, and the teeth are not as "squared off", one of the symptoms you will feel is a crunching when you upshift from second to third.

The solution is to open up the transmission and replace the hub selector. Opening up the transmission is a major job (typically 8 hours or more), so if and when you do it, you should also replace any other synchros and gears that are worn. It would be a good time to do any other transmission work you've been considering - such as swapping for short gears or R&P, replacing the snap ring and upper transmission case for cars in the snap ring range, etc. And note the date and mileage on your maintenance records, because you're changing the transmission fluid at the same time, so you won't have to do it again as soon as the mileage and/or time would otherwise require.

 

[Arata]

Its not really a mystery. On the dyno there is a air brake. The brake can be set to a % of braking power during a pull, so the car basically accelerates likes its on the street. So if the brake has a low % then the wheels and drums will continue to "free spin". On a dyno the car doesn't have to pull its weight, just spin the tires.

On the Mustang dyno site I could not find a dyno that uses an "air
brake" They do use an "Eddy Current brake" as many dynos do, the other common type of brake is a water brake, more common on older dynos. The Eddy current brake was Air cooled.

There are many types of Mustang dynos, but most used heavy drums 2000 lbs and more, so the car does have to pull more than "its weight, just spin the tires" It is acellerating a 2000 lb drum even without the load from any kind of brake.

Mustang dyno site

 

[EndlessNA1]

On the Mustang dyno site I could not find a dyno that uses an "air
brake" They do use an "Eddy Current brake" as many dynos do, the other common type of brake is a water brake, more common on older dynos. The Eddy current brake was Air cooled.

There are many types of Mustang dynos, but most used heavy drums 2000 lbs and more, so the car does have to pull more than "its weight, just spin the tires" It is acellerating a 2000 lb drum even without the load from any kind of brake.

Mustang dyno site

Sorry I did not read that it was a Mustang Dyno and I thought it was a chasis dyno jet or even a engine dyno similar to the one I have at my shop. For this I do not know because I have no experience with a Mustang nor their dynos lol.

 

[NSXTech]

Bottom line on the engine damage is oil pressure and compression test. I have operated on over a dozen 10k+ shifts over the years, and the oil pump is ALWAYS the first to go because the outer ring of the the cycloid type pump can't take the centrifugal forces. At 9k, you may not see any any damage to the outer gear, but it may be cracked and being held together by the housing, as opposed to breaking up and dumping all the pieces down the oil pimp pick up tube as they pass it by.
Also, I would do a compression and/or leak down to see if the inertia of the valve train caused any valves to over extend.

If you're gonna look at the the o.p gears, give the ring a good stiff push down (by hand) over one half whule the other half is supported on a tables edge. Keep doing this at every pump bump
(ryhme for gear teeth) or if you are very high tech, get it x-rayed or if you are very flush, just go for the billet gears. I believe SoS has a set available any day now, so you are not at CT's mercy on pricing.

Lastly, if you are a serious DIY'r, pull #2 rod bearing cap and plasti-guage it. Its the first sighn of overrevving engine deep down failure. Remember you will need a turning angle tourqe guage in addition to a low range accurate (14 ft lb plus about 95 degrees. (CHECK the manual!!)

Good Luck,
MB

 

[ScienceofSpeed]

Thanks for the mention Mark. Here is a direct link:

http://www.scienceofspeed.com/products/engine_performance_products/NSX/ScienceofSpeed/oil_pump_gear/