Pinging redline - how dangerous?

This is an embarrassing post about two driving mistakes in standards but I’ve wondered about one of these driving incidents for some time. 

1. Friend’s 97 Eclipse GS-T, new boost controller with too long of a vacuum hose let the boost hit at least 22 or so psi instead of the 18 dialed in. As soon as we got it hooked up he got sick from some bad lasagna and since he was taking suppositories to get some anti-nausea meds to stay in his system he offered the car for me to go out and enjoy. In the middle of racing a Terminator I went from 3rd to 2nd for just a moment but it was long enough to bleed probably 10mph before i got back on the clutch. Within four months he got a bad case of a bad crank bearing. IIRC it’s a common issue with those DSMs but what’s the likelihood that it was my fault?

2. Driving a manual 06 Miata I got the back end loose around a corner and while the tires were spinning it got up in the red. Not long and not under real workload but still it was up there. No known issues so far but does a blip like that cause damage?

The money shift, yes.

Hitting the revlimiter, not unless you do it all the time.

I banged rev limiter frequently on my Miata's 1.6L (and it was even a supposed timebomb Short Nose Crank) at autocrosses where it wasn't worth the time to click 3rd. Nothing bad ever happened. As long as you aren't sitting on the rev limiter for 45 seconds at a time frequently, I would say it's effect is probably realistically minimal. That's assuming that the rev limiter is set at a safe speed. I've seen some guys when tuning or setting up ECMs put their rev limiter at some absurd speed that the engine really shouldn't see. Some motors with long timing chains (like the Ford GT500 5.8L) I hear that frequent rev limiter abuse can cause chain stretch.

1:  A money shift generally lets you know immediately, and usually involves valve train coming apart. 

2:The ecu has a rev limiter in it.  Most modern stuff can be run up against the limiter quite regularly without issue.  

I think by '97 the 7 bolt 4g63 had the revised thrust bearing which cut down a lot on the infamous "crankwalk" issue. Either way I don't think that it would have waited 4 months to show up if you caused it. As far as the Miata, does the engine act like it's hurt? If not I would assume you're ok.

In reply to P3PPY :

Is said friend a member here or otherwise reading this post?

In reply to Streetwiseguy :

Exactly right. I've never heard of a mechanical overrev affecting bearings, but instead valve train failure. If you're just hitting the ECU controlled rev limit, it's unlikely to do any damage unless heavily abused.

It depends on the car but odds are you're fine occasionally banging up against the rev-limit.  Grabbing the wrong gear is riskier but as others have said you usually know how bad you messed up quickly.  Loosen your grip on the shifter, I don't know how hard it is to shift that particular car but a lighter touch will cause you to miss fewer shifts and you'll shift faster too.  

ebonyandivory said:

In reply to P3PPY :

Is said friend a member here or otherwise reading this post?

Not that I know of. I mean, if I did him wrong I’ll make it right, I’m not too afraid of him hearing bad news. 

Valve train is all I ever hear about with the miss-shift but it sounds like we do have at least one vote for it being my fault

the Miata I drove exactly that one time. The owner is not likely to ever repeat something like that so from what I’m hearing the car should be good. *phew*

In reply to P3PPY :

The truth is, you’ll never know.

I mean, if you let an old woman cross the street In front of you, is it your fault if she trips on the curb and hits her head and dies?

Know what I mean?  You’ll never really know.

1. My understanding, at least on BMWs, is that a money shift results in valve train issues, not crank bearing issues, and you normally notice it right away. That said, it's probably impossible to really know.

2. The Miata is fine. I see people regularly bang against rev limiters for 3 plus seconds, multiple times per autocross. There is an Evo in my region driven by a national champ that BANGS the rev limiter so hard for so long it's terrifying. Violent stuff. Engine is fine as far as I know.

What's a terminator?

Terminator sounds like the new edge 03-04 mustang

aw614 said:

Terminator sounds like the new edge 03-04 mustang

Yes. 

(I know I know, that’s like a V6 but I couldn’t find an actual SVT pic)

money shift and banging rev limiter are two very different things.  

Running a car up against the rev limiter by throttle application, while not advised to do it regularly, at least in stock form is set by engineers as a means to prevent damage.  So bumping it isn't really hurting anything, as it is within the rotating assemblies design parameters.   

The money shift on the other hand is mechanically forcing the engine to over-rev beyond the redline.  Anyone I've known who did this effectively while actually trying to upshift near redline has resulted in valve train destruction immediately.  

I used to bounce a 4AGE 20 valve against the rev limiter daily.  In the 80 or 90K miles I put on the used motor, never had a problem.  Didn't have a tach, so that's kinda how I knew it was time to shift.  That's Toyota, though.

Another vote for: 

1. Money-shift, in my experience, is immediately evident. I did it in my integra a million years ago at TGPR. “Sounds like the old man is cutting the grass in the infield again. OH E36 M3 - THAT’S MY CAR!”

2. Though not intended as a “shift indicator,” rev limiter is there for a reason.

Rev limiter is not to be used as cruise control, it's strictly a safety device.  Timing chain engines hate it when you lean on the rev limiter, too, can cause all sorts of money to fall out of your wallet.  The shock loads can actually cause the links to fail, it's not pretty at all.

Bouncing the rev limiter is also the fast way to kill a rotary.  You're better off overrevving than hitting a limiter under load.  The stationary gears hate it.

Mechanical overrev doesn't just hurt valvetrain, it can also hurt rods.  Either in the form of instant failure or weakening them so that they'll fail in otherwise normal driving some hours later.  I haven't heard of it hurting bearings, though.

I’ve seen 4G63’s survive money shifts a few times. Some with loggers connected, reading a maxed out 9999 rpm! I’ve seen them overreved to the point that the power steering belt expanded and flew off, without damage. With that said, the most likely damage would be from valve float, where the piston kisses the valve that can’t close quickly enough. The second form of failure would be a broken rod. I don’t think it’s likely to hurt the bearings. 

Which bearing failed on the car? The issue on the 2G was the thrust bearing, and it wasn’t as common as people think and as mentioned above, fixed by ‘97.

Now, detonation can hurt the rod bearings, especially chronic detonation. Overboosting once is not likely to do it though, unless you stayed on it for a long pull while pinging. Wouldn’t hurt the main bearings though.

Shoot I can’t remember Which main bearing. Not on the ends

Kinda surprised about all the valvetrain comments. In my mind the big worry is rod failure. 

I think in either case (to different degrees) it's a case of yes, it does something, but you're unlikely to be left holding the bag unless you keep the car on the road forever and when it finally lets go it'll have been long enough that it's impossible to say that 'the event' was a direct cause. 

I tend to think of a lot of things in terms of 'well that probably took 5000 miles off the life of an engine that should have lasted 250k, 245k now cry me a river'. Or something along those lines. I've owned a couple of expensive engines i felt differently about, but not many! 

Also FWIW I have misshifted a 1.8 miata to 8800 rpm (via datalog), no ill effect on said car a couple years later. I also did a 3-2 instead of a 3-4 on my dodge spirit while on a dragstrip. The flywheel bolts came loose (sounded nasty, thought i broke the crank!), so i replaced them and that engine was still running fine when parked other than the piston i melted later. 

For a money shift, the first point of failure will depend on the engine.  Some will float the valves right into the pistons before the rods let go (or the resulting force from piston / valve impact is what hurts a rod).  With others, the valvetrain can handle much higher RPM than the engine revs to (or the valves float but don't hit the pistons), so you can run it right up to rod failure. 

Bearings generally won't be hurt from an overrev, as high RPM / insufficient oiling for that RPM type bearing damage doesn't happen that fast. 

This is a CTS-V that died at a track day, but this was a not uncommon sight for people who did LS1 swaps in RX-7s for track duty.  It's kind of hard to tell what went first due to the extreme carnage, but generally one of the pistons will be "missing", the cylinder wall will be annihilated, and at least one of the valves will be headless.  If the rod had let go first, the top end wouldn't be so comprehensively damaged and usually the piston stays intact.  If a valve comes apart, however, it will wreck the piston, the cylinder wall will get destroyed, and the rod will eventually flail itself apart.  "Eventually" happens pretty quickly at 6500 rpm.

Thanks for the explanations. My plan of action now is to:

1. Say nothing

2. Say nothing

Oh I'm snitchin' . Don't even worry about that.