High Lead in 1.8T stroker Motor 25k mi; Redline 5w-40 5k mi

[Kevin C]

What does 122 pmm of lead mean? As a reality check I worked it out. My understanding is the the PPM is mass based (not volume).

Given that:

The engine holds 4.5 quarts or 4257ml. If the density is .866 g/ml I have 3686.6 grams of oil. If the lead is at 122 ppm, then there is at least 0.45 grams of lead missing from the rod bearings. Lead has a density of 11.43 grams per cc.

11.34*X = 0.45, X = .0397 cc's or 3.9 mm^3

There are four bearing sets that are about 18.8mm wide and they are about 48mm in diameter.

The surface area of one bearing is:

3.14*D*Width, 3.14*48*18.8= 2833mm^2

Four bearings: 11334mm^2

How thick a layer do I need to remove to account for 3.9mm^3 of lead in the oil? Assuming that all surfaces eroded evenly (I know that's not going to happen but I'm just trying to get an understanding of magnitude).

I get 0.000344mm. ACL says that the top layer is 0.013 thick. So its possible to get a 122 ppm reading and not have a large increase in clearance.

What happens if it was just one bearing and half of what was lost off of the bearing got trapped by the filter?

Now we have 7.8 mm^3 of lead missing from one bearing. That's a .0028 mm thick layer, so the shell would still have a 0.0102mm of lining left before the crank hits the nickel barrier layer that is behind the top surface.

The running clearance would have changed .0001".

My take is the I need to swap the bearings out, they are used up. I will inspect the rest of the engine, while I have it out and make a few minor upgrades.

King Bearings has a lot of good information of what fatigued bearings look like and what might be happening to mine.

 

[Pablo]

I love your graphics and your work, I would almost say you are overthinking it, but you aren't and that would be trite.

I will just state - and it was tangentially brought up earlier - you are likely 100% correct on where the lead is coming from, but it probably was doing this to some much lesser degree all along. But different oils will carry lead to be detected in a simple UOA much better than other oils. Redline seems to have this ability. The assumption here seems to be Pb is in solution. It isn't. Certainly this does NOT explain why the first run showed zero lead though! It definitely spiked up.

Maybe run a different oil, see what happens, I mean if you are going to tear into the engine aanyway.

 

[SubieRubyRoo]

Im gonna make a recommendation just before things get really crazy. Take another sample, and send it to a REPUTABLE lab. Not only has Blackstone made themselves infamous for questionable ppm counts, they are also pretty notorious for mixing up reports between customers.

Send off a sample to WearCheck in NC of your current oil. If it’s got elevated lead then at least you’re not tearing the engine down only to determine that everything was absolutely fine. The $35 for WC is a mere pittance compared to the time, energy & expense of an unneeded disassembly of an engine. JM2C…

 

[kschachn]

Prior to switching to Redline I had been running Mobil 1 and had noticed copper glitter in the oil (the lab test showed 9ppm). I switched to Redline with the expectation that it would have better film strength. On the next change there were no visible signs of copper, it looked like everything was perfect.

The oil isn't going to cause that. Mobil 1 isn't going to generate "copper glitter".

 

[Kevin C]

The oil isn't going to cause that. Mobil 1 isn't going to generate "copper glitter".

In general I agree. That said I was pointing out correlation and as we know that does not determine causation.

The reason for the changes was that Redline has a higher 100°C viscosity (double check but it should be 15.6 cst, VS Mobil 1 5W-40 at 13.2. The intention was to get use an oil that should have a higher film strength at temperature.

The other option was to go to an XW-50 oil. For this run I went with 5W-40 but one that was at the higher end of the range.

I agree that on a sample of 1 there is no way to determine causation (or draw a conclusion), that said there was an observable change.

One follow-up note, I did take a look at what was left in my drain pan and found tiny fleck of a bearing material with a low melting point. I seperated a couple of them out using a microscope and I was able to melt them using a soldering iron.

 

[Nathan]

Detonation has a way of hammering bearings. If oil pressure is/was good, perhaps look at your injectors for cylinder to cylinder evenness and check the plugs for peppering. I like to put the highest flowing injector in hole #3 (usually the hottest) on a 4 banger.

 

[Kevin C]

Detonation has a way of hammering bearings. If oil pressure is/was good, perhaps look at your injectors for cylinder to cylinder evenness and check the plugs for peppering. I like to put the highest flowing injector in hole #3 (usually the hottest) on a 4 banger.

A very good point. I did get confirmation from ACL that that the top bearing layer is about 85% lead (they were very responsive to my questions). I have have started to order the long lead parts (Cometic head gasket is one) and I will keep an eye on the metal levels. Plug inspection will be on the weekend.

The tin levels don't quite match up so I will follow up with a test from another lab and a filter inspection.

The tear down looks to be a over the holidays project.

I apricate the help and good suggestion from everyone.

 

[Mainia]

Any UPDATE to your findings?????

 

[Kevin C]

Any UPDATE to your findings?????

The plan was to pull the motor out and inspect it over the Christmas holiday. The engine still runs great, no strange noises.

On December 22nd I got rear-ended by an uninsured, unlicensed driver (or his girlfriend it was not clear who was driving). Between insurance and that its hard to get replacement A4 ultrasport bumpers, the car was tied up for two months waiting for parts. It was a pretty good hit and fortunately the damage was limited to just the bumper and the structure behind it. Minor damage to the chassis, but every part of the bumper system was trashed. The car was an easy fix but cost for repair run up pretty quickly.

I worked with the body shop to keep it from being a technical total. The shop did an awesome job and it looks perfect. About the same time the car developed a mystery water leak.

That kept it in the shop for a few more weeks. Once we found the source it was an easy fix. Basically, I stopped driving the car for a few months. In the process the headliner was pulled and replaced as was all the trim above the belt line (color change from grey to black). The interior update looks great.

I have about 2500 miles on it since I got the the report with the high lead reading. I plan on tearing it down in a about three weeks.

 

[Kevin C]

This week I finally pulled the motor apart. The source of the lead was one wiped out rod bearing. The bearing had overheated and smeared, flaked and cracked but had not spun. The bore on the rod was blue from heat, the bearing journal on the crank showed no discoloring and measures out like nothing ever happened.

The other three rods look fine. All of the main bearings (bi metal aluminum) show fatigue wear (flaking).

The motor gets put back together with a fresh set of rods and rod bearings with a bit more clearance. The mains get upgraded to coated tri-metals. What is interesting is that the mains were not holding up, but I was not seeing a spike in aluminum in the oil.

I have a few other changes planned including DLC Coated lifter buckets, higher grade exhaust valves, (sodium filled Inconel) a better intake cam, larger intercooler, chamfer the cranks oil passages, oil temperature monitor, real oil pressure gauge and warning and perhaps drop the redline down to 7000 rpm. I am checking for any signs of detonation. There was a surprising amount of deposits in the pan above the oil line.

Good vs bad @ 30,000 miles.

 

[KEVINK0000]

I’m surprised this was not noisy before teardown.

 

[ScottyB]

This week I finally pulled the motor apart. The source of the lead was one wiped out rod bearing. The bearing had overheated and smeared, flaked and cracked but had not spun. The bore on the rod was blue from heat, the bearing journal on the crank showed no discoloring and measures out like nothing ever happened.

great save! out of curiosity, which cylinder # bearing took the beating? was it the one furthest from the pump?

7000 does seem to be a pretty stout number for a stroked engine like yours. will the cam upgrade be able to help fatten the curve a little lower down so you can work with the drop in max RPM? that would be a pretty nice way to make lemons out of lemonade.

I had a '99.5 A4 1.8TQ 5spd years ago that unfortunately succumbed to oil sludge despite regular oil changes. its nice to see your A4 still kicking with such a unique block/head combo.

 

[thastinger]

This week I finally pulled the motor apart. The source of the lead was one wiped out rod bearing. The bearing had overheated and smeared, flaked and cracked but had not spun. The bore on the rod was blue from heat, the bearing journal on the crank showed no discoloring and measures out like nothing ever happened.

The other three rods look fine. All of the main bearings (bi metal aluminum) show fatigue wear (flaking).

The motor gets put back together with a fresh set of rods and rod bearings with a bit more clearance. The mains get upgraded to coated tri-metals. What is interesting is that the mains were not holding up, but I was not seeing a spike in aluminum in the oil.

I have a few other changes planned including DLC Coated lifter buckets, higher grade exhaust valves, (sodium filled Inconel) a better intake cam, larger intercooler, chamfer the cranks oil passages, oil temperature monitor, real oil pressure gauge and warning and perhaps drop the redline down to 7000 rpm. I am checking for any signs of detonation. There was a surprising amount of deposits in the pan above the oil line.

Good vs bad @ 30,000 miles.

View attachment 296198

That's a lot of work and headache for 320HP...but any time you get to 3HP per CI...you're going to have trouble.

 

[Kevin C]

That's a lot of work and headache for 320HP...but any time you get to 3HP per CI...you're going to have trouble.

More trouble than I had expected. This is not an aggressive target for this engine, lots of builds target 500+ hp, also this is WHP, not CHP. That said, I got five years of driving out of it and the crank is still good. The rod bearings that look good say its possible.

great save! out of curiosity, which cylinder # bearing took the beating? was it the one furthest from the pump?

7000 does seem to be a pretty stout number for a stroked engine like yours. will the cam upgrade be able to help fatten the curve a little lower down so you can work with the drop in max RPM? that would be a pretty nice way to make lemons out of lemonade.

I had a '99.5 A4 1.8TQ 5spd years ago that unfortunately succumbed to oil sludge despite regular oil changes. its nice to see your A4 still kicking with such a unique block/head combo.

It was the #2 bearing. The cam upgrade shifts the power band a bit to the right. One issue I have had is the low rpm torque comes up so quickly its hard to drive smoothly, it even causes the cruise control to surge going up grade, this is a very mild change. I think the low end TQ may have been a factor on the mains.

7000 does sound high, but I think it manageable if I open the clearance up a bit. The more aggressive builds are running 500+hp 8000+ rpm in street trim. The first 25,000 miles were fine, it was good until it wasn't.

If is was not sending the oil out for analyses I probably would have lost the crank. This was a fun experiment, fix up my A4 and upgrade it VS buying something different. There are definitely cheaper ways to go fast, but I have been having fun with this. The new build gets DLC coated lifter buckets to go with the new cams and a few other goodies.

At some point I will need to get a different daily driver, my signifigant other has dropped a couple of hints that its time. Most of this is I like building cars and experimenting a bit.

 

[Kevin C]

I’m surprised this was not noisy before teardown.

Me too, based on its looks it should have been noisy. The running clearance had opened up to about .003". The remaining surfaces still feel very slippery, like the polymer coating is still there. This is the first wiped out rod bearing that I have pulled from an engine that feels slippery.

No good explanation, just a mental note that this was odd.

 

[twX]

The motor gets put back together with a fresh set of rods and rod bearings with a bit more clearance. The mains get upgraded to coated tri-metals.

If the issue was related to fatigue cracking, you'll want the new bearings to have a higher load carrying capacity than the old ones.

and perhaps drop the redline down to 7000 rpm.

What did you have the rev limit at before, and what's the limit for the stock engine that uses this crankshaft?

Here's an example of how quickly the load on a rod bearing increases with rpm. Lowering the rev limit by even a small amount can make a big difference.

The bearing at the top of your photo has two wear spots that are off towards the sides. This seems to be characteristic of wear that occurs at high inertial loads (high rpm), at least for the cap side of the bearing.

Another issue with high rpm is that the MOFT decreases, the bearing runs hotter, the oil film viscosity goes down, and the lower viscosity causes higher peak bearing loads which can lead to fatigue cracking.

The higher the engine revs, the more oil pressure is required to maintain enough flow to keep the bearings cool and maintain adequate MOFT. This relationship isn't linear. If you increase the rev limit by 10%, you should increase the oil pressure at redline by at least 15%.

You mentioned that the engine had a higher displacement oil pump. If it doesn't also have a higher pressure relief setting, it might not actually be providing much more flow and pressure than the stock pump at redline. If that's the case, I'd upgrade to a pump with a higher relief setting, or shim the spring to increase the relief pressure.

Above a certain rpm, the oil pump will lose so much efficiency that the oil pressure will start dropping as revs increase, and this might end up being be a limiting factor for how high the engine can safely rev.

Looser clearances will help reduce bearing temperature, but if they're too loose, the opposite will happen. A looser clearance might also require more oil flow to maintain adequate pressure, which could be an issue depending on the oil pump. So there's no guarantee that looser clearances alone will prevent the bearings from failing again. I'd lower the revs or increase the oil pressure, or both.

 

[Kevin C]

If the issue was related to fatigue cracking, you'll want the new bearings to have a higher load carrying capacity than the old ones.


What did you have the rev limit at before, and what's the limit for the stock engine that uses this crankshaft?

Here's an example of how quickly the load on a rod bearing increases with rpm. Lowering the rev limit by even a small amount can make a big difference.

View attachment 296428

The bearing at the top of your photo has two wear spots that are off towards the sides. This seems to be characteristic of wear that occurs at high inertial loads (high rpm), at least for the cap side of the bearing.

View attachment 296429

Another issue with high rpm is that the MOFT decreases, the bearing runs hotter, the oil film viscosity goes down, and the lower viscosity causes higher peak bearing loads which can lead to fatigue cracking.

The higher the engine revs, the more oil pressure is required to maintain enough flow to keep the bearings cool and maintain adequate MOFT. This relationship isn't linear. If you increase the rev limit by 10%, you should increase the oil pressure at redline by at least 15%.

You mentioned that the engine had a higher displacement oil pump. If it doesn't also have a higher pressure relief setting, it might not actually be providing much more flow and pressure than the stock pump at redline. If that's the case, I'd upgrade to a pump with a higher relief setting, or shim the spring to increase the relief pressure.

Above a certain rpm, the oil pump will lose so much efficiency that the oil pressure will start dropping as revs increase, and this might end up being be a limiting factor for how high the engine can safely rev.

Looser clearances will help reduce bearing temperature, but if they're too loose, the opposite will happen. A looser clearance might also require more oil flow to maintain adequate pressure, which could be an issue depending on the oil pump. So there's no guarantee that looser clearances alone will prevent the bearings from failing again. I'd lower the revs or increase the oil pressure, or both.

The main bearing upgrade is going from bi-metal to ACL Trimetal, so its a significant upgrade. I am considering revising the tune to reduce boost under 3500 rpm. The stock rev limiter on the engine is 6800 rpm, I upped it to 7400. The pressure relief was shimmed to add an extra 10 psi.

I am opening up the clearance on the rod bearings. .0005" of extra clearance will increase the flow area by about 33% (.0015 clearance to .002"). In retrospect, that is what I should have started with. It was a new crank and new ACL racing bearings. I had not heard of issues with people running the stock clearance on built engines; lots of builds with people just running a set of drop of rods and bearings.

I agree on the loading mark on the rod bearing.

Thanks for the input.

My learnings so far are.... Add a bit more clearance, shift sooner and run trimetals on the mains.

 

[twX]

The main bearing upgrade is going from bi-metal to ACL Trimetal, so its a significant upgrade. I am considering revising the tune to reduce boost under 3500 rpm. The stock rev limiter on the engine is 6800 rpm, I upped it to 7400. The pressure relief was shimmed to add an extra 10 psi.

I am opening up the clearance on the rod bearings. .0005" of extra clearance will increase the flow area by about 33% (.0015 clearance to .002"). In retrospect, that is what I should have started with. It was a new crank and new ACL racing bearings. I had not heard of issues with people running the stock clearance on built engines; lots of builds with people just running a set of drop of rods and bearings.

I agree on the loading mark on the rod bearing.

Thanks for the input.

My learnings so far are.... Add a bit more clearance, shift sooner and run trimetals on the mains.

I was only really addressing the rod bearings in my post, but yeah, the main bearings won't care so much about rpm or oil pressure. Switching to a stronger bearing is the only thing that comes to mind for the mains, aside from tuning changes. An extra 10 psi over stock should be about right for the rod bearings. As far as I can tell, you know what you're doing.

How thick a layer do I need to remove to account for 3.9mm^3 of lead in the oil? Assuming that all surfaces eroded evenly (I know that's not going to happen but I'm just trying to get an understanding of magnitude).

I get 0.000344mm. ACL says that the top layer is 0.013 thick. So its possible to get a 122 ppm reading and not have a large increase in clearance.

I've done the same calculations for some different engines. Plugging the numbers for your engine into my spreadsheet, I get a clearance increase of 0.00364 mm, which is almost exactly 10 times higher than your figure. One of us must have a decimal in the wrong place. My figure equates to around a 10% increase in clearance. This isn't accounting for uneven wear or unmeasured wear metal, so a much higher clearance increase in reality.

 

[AEHaas]

I wonder if the oil was too thick and resulted in starvation from lack of flow. Low flow also results in poor cooling of the bearing that increases the chances of over heating. Is there pitting in the bad bearing, it could be from cavitation.

High RPM may "thicken" the oil in the bearing from the formation of an oil wedge. This can be good or bad.

Have you ever run the engine to high RPM with the oil not up to normal operating temperature? I end up doing this often and one of the reasons I run thinner oils in my high HP motors.

ali