Thought exercise - Would accusump have saved this engine?

https://youtu.be/Lmcj_JuN7lE

I was watching this video, and just was wondering if an accusump could've saved the engine or if he came to the wrong conclusion on what caused the failure? 

I ask as an interested party since I'm going to add overboost protection to the Exocet soonish and if overboost saves the engine at the cost of the engine ... you get it.

*edit*

For those who can't/won't watch the video here's the order o' operations.

1.6 Miata motor.
0) In the video @ 4:11 he ups the boost, but doesn't up the overboost control in MSPNP
1) While @ WOT he hits the boost cutoff in MSPNP and says they saw a severe drop in oil pressure for a split second (this is the point that I wonder if an accusump would've filled the gap?) because of the hard cutoff.
2) Engine starts ticking - he thinks (hopes) it's a hydraulic lifter failure.
3) 1 Hour later on the way from the dyno, car chucks a rod - catches on fire.
 

What's the youtoobe doode saying (summary)?

Overboost will keep your motor from blowing up if there's too much boost.  Accusump will keep your motor from blowing up if there is no oil available at the oil intake of the oil pan, such as in prolonged severe cornering.  It can also pre-lube the motor.

Looks like accusump or even a dry sump wouldn't have saved it. Something (possibly the violence of overboost protection kicking in) weakened a rod which later let go, all the consistent oil supply in the world would do nothing to prevent that. It's still better to have overboost protection than not.

Edit: If this were a lubrication problem he would've heard hellacious rod knocking noises for at least a couple minutes before the rod ejected.

The dood is TheCarPassion channel on Youtube - pretty well respected 'ootoober in the miata realm

0) In the video @ 4:11 he ups the boost, but doesn't up the overboost control in MSPNP
1) While @ WOT he hits the boost cutoff in MSPNP and sees a drop in oil pressure because of hard cutoff.
2) Engine starts ticking - the thinks (hopes) it's a hydraulic lifter failure.
3) 1 Hour later on the way from the dyno, car chucks a rod - catches on fire.

In reply to GameboyRMH :

Even though he claims they saw a severe drop in oil pressure at WOT because of the overboost hit?

GameboyRMH said:

Edit: If this were a lubrication problem he would've heard hellacious rod knocking noises for at least a couple minutes before the rod ejected.

They immediately heard a tick start, but it wasn't full on knocking yet.

accordionfolder said:

In reply to GameboyRMH :

Even though he claims they saw a severe drop in oil pressure at WOT because of the overboost hit?

Well imagine what would've happened if the overboost protection wasn't there - probably a hole in a piston, which is less of a catastrophe in itself, but the overboost protection left him with an engine that was still running and could've been salvaged through a teardown and inspection. And again if this were any kind of lubrication-related failure, there should've been rod knocking noises from the lack of lubrication before the rod left the block. Not just ticking.

GameboyRMH said:

accordionfolder said:

In reply to GameboyRMH :

Even though he claims they saw a severe drop in oil pressure at WOT because of the overboost hit?

Well imagine what would've happened if the overboost protection wasn't there

He didn't actually overboost - he just forgot to up the electronic boost protection in tandem, but your vote seems squarely in the 'no' realm.  

The oil pump is driven off the crank shaft in almost all applications.  OK, dry sump, it could be driven off an accessory belt that's connected to the crank, but short of that, driven off the crank shaft internally, or maybe driven off a cam shaft that is driven off the crank shaft.  Overboost in MS is going to do what?  Cut spark and fuel?  Cut spark, fuel and open the waste gate?  That's not going to stop the motor/crank shaft from spinning and making oil pressure.  Even a sudden, total power loss is still going to have the crank spinning and the oil pump running as the car coasts down.  I think something let go when he overboosted it and that caused something funky in the oil pressure, if he was charting that.

In reply to Dr. Hess :

Great points. Hmmm, I wonder if he has the data logs still.... This is an older video. I'm just all for learning from other's pain. 

**edit, it's a 1.6 miata motor btw.

Also worth noting (mentioned above). He didn't actually overboost, he just forgot to raise the electronic boost control in tandem (so it wasn't 30 psi or something, he just bumped it from 17-18 or something like that)

Accusump wouldn't have done anything except maybe dump an extra 2 quarts onto the fire.

Maybe it's just my imagination, but compared to the first run, the run that begins at 3:47 sounds...off.  Some kind of staccato exhaust note that shouldn't be there.  Also some oil smoke at 1:22.  

He knew he was pushing it. Maybe the power loss and momentary oil pressure loss was a rod or main bearing seizing up?  I applaud the effort and candor.  

My experience with a 1.8l Miata engine. 

Turned boost up for a national championship event. Using launch control (two-step) heard the engine start ticking after a launch and it sounded like a lifter. 

Continued running it for the rest of the event and towed it home. A couple weeks later drove it to an event 2 hours away (still ticking) and it blew up 15 seconds into the first run. 

After tearing it down and looking at the pieces, one of the rods was bent, the other was non-existent. It looks like the rod that let go (#1) got bent and the piston was tapping against the crank counterweight and eventually the piston broke up and jammed everything before throwing it out the side of the block. 

The bearings all looked good. In my case at least (and likely this case as well) the accusump would have done nothing to help. 

Roger - so it sounds like the working theory right now is he already had broken the engine or was nearing the breaking point and they just happened to coincide? My motor has rods done on it already, and I'm not going for 300 hp (only 230ish). 

Keep in mind, I'm just catching up with that channel, so later on he might go into more detail and I just haven't watched that video.

Hitting a hard cut under power is never a good thing.   You are much better off dumping excess fuel or pulling timing so that the engine stops making so much power FIRST.

I'm trying to think of a mechanism where it could momentarily uncover the oil pickup (what an Accusump will correct) and I can't think of anything that would be more stressful, oil-in-the-pan-wise, than accelerating or decelerating or cornering.

  When you hit a rev limiter, all sorts of bad things happen inside the engine harmonic-wise, like shredding timing chains or making belts jump time.  But the oil pump is driven off of the nose of the crank.

I am wondering if it didn't get momentary detonation when it came back on at high boost because there was more air in the chamber than normal (residual exhaust gases flushed out) which means you will have insufficient fuel AND too much timing for that cylinder at that time.  Maybe it detonated so hard it rattled the main caps and the oil in the gallery blew out for a moment?  Very thin, but it's the only thing that makes sense.

EvanB said:

My experience with a 1.8l Miata engine. 

Turned boost up for a national championship event. Using launch control (two-step) heard the engine start ticking after a launch and it sounded like a lifter. 

Continued running it for the rest of the event and towed it home. A couple weeks later drove it to an event 2 hours away (still ticking) and it blew up 15 seconds into the first run. 

After tearing it down and looking at the pieces, one of the rods was bent, the other was non-existent. It looks like the rod that let go (#1) got bent and the piston was tapping against the crank counterweight and eventually the piston broke up and jammed everything before throwing it out the side of the block. 

The bearings all looked good. In my case at least (and likely this case as well) the accusump would have done nothing to help. 

The scenario does sound a lot like what happened to yours, doesn't it?

I'm all but convinced that you cracked a piston or a wristpin, and it just took that long for all hell to break the rest of the way loose.

I still kinda wish that the broken rod was removable from the crank (the big end still spun freely!  But the bolts/nuts were mangled) to look for any telltale detonation signs in the upper shell.

Tyler H said:

Accusump wouldn't have done anything except maybe dump an extra 2 quarts onto the fire.

I lol'd

In a later video, he takes the blown engine apart.  The rod was broken in the middle but the big and small ends looked OK. In my experience, an oil issue usually results in the end of the rod turning black/blue from heat due to friction from a lack of lubrication.  Since we don't see that, it doesn't look like a lubrication issue.  I don't think an accusump would have helped at all.

In reply to Titan4 :

I'm wondering if he looked at the main caps too.  If they are a loose fit in the registers and/or there's obvious frettng on the block or cap faces, they were getting pushed down off the block.

The factory "block brace" is more of an NVH thing to keep everything better in line side to side under normal loads.  The kind of forces involved when rattling the caps would laugh at that little sheetmetal thing.

Titan4 said:

In a later video, he takes the blown engine apart.  The rod was broken in the middle but the big and small ends looked OK. In my experience, an oil issue usually results in the end of the rod turning black/blue from heat due to friction from a lack of lubrication.  Since we don't see that, it doesn't look like a lubrication issue.  I don't think an accusump would have helped at all.

this. Broken/bent rods are not usually a lubrication issue but a pressure issue. If the bearings had let go, then maybe. But my gut tells me this engine was not long for this world at the levels it was being pushed. 

Without knowing what the overboost was programmed to do it’s just a guess, not even an educated one. But I’ll make an uneducated one anyway  

If it just cut spark then it could have continued to dump fuel into the cylinders leading to a bent rod from build up of liquid fuel. 

Detonation or misfire during recovery from the overboost could have resulted in an overpressure situation, or caused a piston to try going back down when it should have been coming up  

Without knowing how the timing belt routes in a Miata, could sudden cut in power allowed piston and valve contact?

In reply to No Time :

Hydrolocking a running engine with fuel is just about impossible.  The fuel blows right out the exhaust, it doesn't stick around.

Anyway, if you do this, you run the (significant) risk of spinning the turbo up HARDER as the air and fuel ignite in the exhaust manifold. 

If we think the overboost proteftion itself cycled/overloaded the rods, what's a better method?  I understand the difference between a hard vs soft rev limiter - is it more or less the same approach for overboost?

I've never tuned a fuel injected car before, but I'll need to get smarter about forced induction megasquirt tuning next year (if all goes well..).

Don't think it has anything to do with hydrolock, meaning a buildup of liquid in the cylinder. Do believe there was a momentary loss of rotation that caused the oil pressure drop. Now that cause could be numerous but believe the closest term would be pressure lock. A build up of excessive pressure inside the cylinder before a valve open to relieve the pressure. Only has to happen in 1 cylinder once and the other cylinders momentum would continue to spin the engine after that extremely short moment. Damage done and a ticking time bomb before catastrophic failure.

Similar to what we call in airplane/helicopters terminology a sudden stoppage. Props/Rotors going through something like a tree or bush or anything solid and not appearing to stop the contact is the extremely short moment of stoppage and momentum continues the rotation. A moment of reverse pressure on the drivetrain.

I don't think it was anything to do with the overboost.  Hitting it feels violent, but it's not really any more so than lifting off the gas at that high a rev, it's just that you're not expecting it.  Also, Miatas lose oil pressure under hard braking at the track all the time, it doesn't pop motors.

Conventional wisdom on miataturbo.net is that the limit for stock rods lies somewhere between 200 and 250 rwtq (note:  torque, not horsepower).  If you run it that high, a little bit of detonation can push the rods over the edge into failing, so that's my suggestion.

Not gonna lie, I didn't read the whole thread. I just came here to say that the only thing your oil pump cares about is rpm, not load. Momentarily cutting ignition or fuel on a spinning engine doesn't appreciably lower its oil pressure.  So regardless of what else was said, that whole concept is bunk. 

One of the implied meanings behind the words 'bolt on', 'kit', and 'plug and play' is "you don't actually need to know how an engine works to install this", so i can see how some MSPNP users might come up with some.. interesting theories as to how their stuff mysteriously breaks.