Engine teardown results

[icepenguin66]

While I understand where you're coming from icepenguin, I have no intentions of going down that road at all. Already in speaking with my engine builder he's mentioned a couple of potentially undetectable - but illegal - tricks that could net me a few ponies. While I'm intruigued from an engineering point of view, I'm not interested.

Here's the way I look at it - I do this because I enjoy competition. I want to win because I'm the best driver, not because I cheated and didn't get caught. If - and this is a big if - I were to perform well at the National level with an illegal car, that would always be in the back of my mind, and it would forever taint the victory in my memory.

I'm sure there are other people out there cheating. They have their consciences to live with. I have mine, and I intend it to be clear.

I'm on the same page as far as cheating and performance gains. I just see this as a reliability issue not a performance/power mod.

[altiain]

So Altiain, was the only damamge in the engine on the 2 & 4 journals?? What was the condition of the rest of the engine??

So far, so good. The crank journals are going to need some minor refinishing due to the rod bearing damage, but other than that the engine was in good shape.

icepenguin, I'm not going to go so far as to suggest that there is an inherent flaw in the engine. As General Default pointed out, I did experience a lower than expected oil pressure reading at a particularly hot event, and that reading was - as near as I can recall - around the same time the noise started. At this point I'm willing to suggest that overfilling the crankcase by half a quart or so, couple with diligent monitoring of the oil level and pressure during events should probably stave off any damage. I'll probably even try Royal Purple or some other single weight oil just to see if the oil pressures are more stable during events with a single weight oil.

The rest is just supposition. There is probably a higher possibility of oil foaming in an autocross environment than street or open track use, but that's just a guess on my part based on my (limited) understanding of what goes on in the crankcase during high frequency, high G maneuvers. I have no real evidence to base that theory on.

[gabkwong]

I'm willing to suggest that overfilling the crankcase by half a quart or so, couple with diligent monitoring of the oil level and pressure during events should probably stave off any damage.

Iain,

1. Will that increase the possibility of foaming by overfilling?
2. Will the overfilling rob a couple HP?

Little cricket wants to know

[altiain]

Iain,

1. Will that increase the possibility of foaming by overfilling?
2. Will the overfilling rob a couple HP?

Little cricket wants to know

1. Shouldn't (foaming is caused by sloshing the oil, not the quantity of oil).
2. Shouldn't (Oil quantitity shouldn't interfere with engine losses, but higher viscosity might rob a fraction of a horsepower).

[Titus]

Will that increase the possibility of foaming by overfilling?

Funny... I was going to ask the same thing. I thought I remembered reading a warning to that affect somewhere on the pointy board garage, but I can't find the reference now.

[gabkwong]

Funny... I was going to ask the same thing. I thought I remembered reading a warning to that affect somewhere on the pointy board garage, but I can't find the reference now.

I read this from the Grass Root Motorsport. It was in one of the tech article a few months back. Perhaps I didn't understand what they were saying.

[Majik]

I have heard that overfilling can cause foaming because the crank "whips" at the oil. This is complete and total hearsay. I have no idea if it applies to Miatas or not. Just another viewpoint from someone who has heard of this. The counter point is that both Altiain and I both know what happens when the engine is under filled. Me personally, I now overfill my engine around 1/2 quart before autoXing.

[black roadster]

While it is certainly curious that two AutoXers have experienced similar engine damage I have a hard time believing it is a problem with AutoXing Miatas.

How many people AutoX Miatas? Tens of thousands? Now how many people have had this issue? We know of two.

The cracked swaybar mounts are a problem since so many folks have experienced it but I don't recall any stories of blown motors due to oil starvation while AutoXing.

Good theories and it could have some truth but I seriously doubt it's a pandemic problem.

[Majik]

My problem did happen on the street. I was 20 or so and alot less lets say maintnence prone. I took an agressive turn on an empty road going to a friends house as I came out of it I heard the very agressive knock. Not something that I could wait a few months to figure out what it was like Iain. I would be interested to know if mine was much worse.

[MadMerv]

1. Shouldn't (foaming is caused by sloshing the oil, not the quantity of oil).
2. Shouldn't (Oil quantitity shouldn't interfere with engine losses, but higher viscosity might rob a fraction of a horsepower).

Actually both of them will, to some degree, because now the crank is running in more oil, as the level has increased slightly.

[trackdog]

Yes Marc, yours was a lot worse than Iain's. Iain's engine looks like it was at the beginning of rod bearing failure. The #2 and #4 were loose in the rod journals, but were not spinning. On yours Marc the bearing surface was egg shaped, so you had been running this for sometime. Iain looks like he caught it early, so to say. I have not evaluated your motor's rods to see if they can be reused, but Iain's were an excellent shape.

I looked at the oil pan and the normal oil level. At the full mark you oil is only about a 1/2" in the section of the oil pan that does not extend down toward the front of the engine. With the windage tray installed there is still about a 1/2" space. Adding a 1/2 a quart of oil or even a little more is not going to put the oil into the crank rotational area. I have seen several brands of oil pans and I can say Mazda did a good job of baffling around the pickup area, I don't see any room for improvements.

As for oil types, when I was using synthetics on the track I would notice that when I came in and the engine was idling the oil pressure was lower that when I went out. This was 10W30 at that time. Since then I have switched back to mineral oil, 10W40 and do not see the oil pressure dropping as low. My theory is that synthetics, although they may be superior in some areas, thin out more as they get hotter. There is probably some horsepower in the thinning oil, but how much is measurable?

Running a car as hard as a lot of us do means we change the oil often. With FI engines you contaminate the oil a lot early from running rich mixtures that you require. I change my oil about every 2000 miles or when I see the oil getting dark. It does not make since to use synthetics when you change oil so often. I do use synthetics in my family cars because I do drive a lot of miles between oil changes, but don't see it necessary for track use.

Gary

[Mark52]

I typically pour in 5, yes 5, quarts when I change the oil. I have never seen any evidence of foaming, at least as would show on the dipstick immediately after a hard run. I think with autocrossing it's not a bad idea to keep the level above normal.

[trackdog]

We sell an oil pressure kit for upgrading the Miatas that do not have actual readings. We have not had a request, but could easily setup a kit that has an alarm output and inlude a buzzer that would let you you know when you lose pressure momentarily. If that would be of interest let me know.

Gary

[POS Racing]

How high up in the pan is the oil normally??



Were the oil passages clear on your motor Altiain? Would there be any advantage to boar them out to get more oil to the bearings?

[MadMerv]

Not very high with it on it's side...........