4722 replies to this topic

[fezzasus]

 

Thanks

 

No problem.

 

Essentially metallic bearings have stayed the same design for decades, they've been reactive in limiting and finally reducing lead in OEM bearings (all pass. cars won't have lead in now), some have stayed conservative and just changed it to antimony, while smaller engines with less torque have allowed for more experimentation, moving to polymer bearings - this will be interesting and does allow for significant differences in bearing brands, however is unlikely to impact aftermarket bearings for a long time to come.

[FLD]

Thats interesting as (some time ago) I had some bearing shells coated with a special 'low friction coating' via one of the NW's coating companies.  What a disaster that was!  Peeled off in use and bunged the damn thing up with black plastic.  Looked like a bin liner had been shredded and dumped into the sump.

[fezzasus]

 special 'low friction coating' 

 

Sounds like DLC. Not suitable for bearings, actually no coating is suitable for bearings, typically a tin flashing is used to prevent corrosion before being installed, but that's it.

[cnrandall]

Interestingly enough I had an aftermarket set of mahle bearings 'delaminate' on me on a customers cars and a I thankfully found it before any damage was caused.  Since then I just use the stock bearings which have the benefit of coming in a good range of sizes.  I've not had any bearing problems since running up to 410ft lb at the hubs.

[cnrandall]

 

 

Mahle lead copper bearings used in Nev,s engine same spec used in more powerful clet and zlet engines. Lack of lubrication causes bearings to fail. The Pikes Peak RS200 EVO uses similar spec bearings but are narrower and that has 600ft/lbs torque and 850 bhp. Steve

  Steve, i'm aware of bearing modes of failure, and there are plenty more than just lack of lubrication.   Do you have any explanation as to why there wasn't sufficient lubrication? The valve train will see oil starvation before the bearings, is there any excessive wear there? Were the oil levels low, or had the oil pump failed? With any aftermarket build I would be looking at poor installation before looking at the lubricant, simply because the tools and the quality control used aren't up to the OEM standards.   Oil pressures, and bearing diameters will be different with the Pikes Peak RS200 EVO so not really a fair comparison. Bearing diameter also has a significant impact on bearing durability and power handling. Secondly this car will have much more regular maintenance/rebuild schedules than a road car.

 

Bearing sizes both width and diameter are very similar as are minimum and maximum oil pressures although different lubrication set ups. I guess there could be any/or several problem with the lubrication. Oil not returning to the sump quick enough, engine will have been held at full throttle for longer whilst strapped to the rolling road. Oil dilution. Low oil level. Oil pump cavitation. Oil contamination. Oil pump problem. I have just unshrouded the oil pick up strainer (and baffled the sump)on a Renault Clio F4R I do wonder if something similar is needed. I am really just guessing. Usually with hydraulic followers low oil pressure can be heard, with Nev's engine it is solid lifters so you would not hear it rattle (hydraulic follower not fully filling with oil) The installation is quite simple so as long as everything was clean and checked during assembly it should have been ok, Nev did the best part of 8k miles before without lubrication problem. Nev changes the oil regular also. I cannot explain why it has started smoking again, as after deglazing the bores and fitting new pistons and rings there was no sign of any smoke. I would like to know myself what has happened even if Nev decides to take the engine elsewhere to be rebuilt/repaired or does it himself. Steve

 

 

Given that this car has had very little mapping work but lots of changes made to the engine I would say oil dilution would have to rank pretty high on your list.  

[joshua]

There's a lot of sealant on those parts - might be worth checking the oil galleries are clear.

[Nev]

Just spent another 1.5 hours stripping the engine down. Got the sumps off and was just taking the cams out when my arse annoyingly decided it wanted to visit the porcelain throne. 

 

I can't say I am enjoying taking the thing apart. Another hour of work should get the head and rods out/off to visually inspect it all.

[jameso]

Keep plugging away nev

[Nev]

Spent another hour in the garage and got the head off. Looking at the cylinder bores my initial views are:

 

1. Cylinders seem uniformly worn.

2. Fairly uniform burn on the piston crowns (all spark plugs were a nice even brown), though one cylinder showed less contaminants on the crown.

3. The non-thrust side of the walls seemed to have more wear than I'd expect.

4. The thrust side of the walls seems moderately worn, but have some patches of hatching still on them even at the top.

5. No sign of "blobs" of glaze on the walls anywhere.

 

I've posted up a load of pics, any comments from people who know what they are talking about please?

 

 

 

 

 

 

 

Edited by Nev, 08 December 2013 - 04:36 PM.

[cnrandall]

From the pics those bores look very worn although its difficult to say from pictures.  You need to measure the bores.  Looking at those honing marks, was that honed on a honing machine last time around or just a hand hone?

[Nev]

I've taken a couple of high res close up shots, one of the thrust face and the other of the exhaust side. Both on cylinder #3, which is perhaps the worst worn.

 

 

Exhaust Side:

 

 

Inlet Side:

 

Edited by Nev, 08 December 2013 - 05:14 PM.

[steveboyslim]

From the pics those bores look very worn although its difficult to say from pictures.  You need to measure the bores.  Looking at those honing marks, was that honed on a honing machine last time around or just a hand hone?

The bores were 'glaze busted' rather than honed, then measured. Less than half a thou bore wear was measured, bores were round and parallel. Steve PS where are the pictures on your web site ?

Edited by steveboyslim, 08 December 2013 - 05:20 PM.

[Nev]

These are the pics Steve - I didn't put any on my own website. Those last 2 are about as good as I can get with my camera I'm afraid.

Edited by Nev, 08 December 2013 - 05:25 PM.

[alanoo]

 

 special 'low friction coating' 

 

Sounds like DLC. Not suitable for bearings,

 

 

Try to tell that to all F1 teams

[alanoo]

About the pistons, can't remember precisely which pistons you got, were they skirt coated ? How much was the piston to skirt clearance ? Don't look that bad to me and definitely should not be an issue

[steveboyslim]

About the pistons, can't remember precisely which pistons you got, were they skirt coated ? How much was the piston to skirt clearance ? Don't look that bad to me and definitely should not be an issue

Pistons made by Omega Pistons Ltd, in Nev's case pistons used in a finished bore size of 86.5mm. Pistons skirts not coated. Steve

[vocky]

that could be bore wash, possibly too much fuel has washed away the engine oil and thus you have piston to block contact 

[fezzasus]

The polishing is very high, i'm also concerned about the scoring. both could be due to fuel dilution. Get the cylinders properly honed next time, the lack of proper honing will also exacerbate wear.

[fezzasus]

 

 

 special 'low friction coating' 

 

Sounds like DLC. Not suitable for bearings,

 

 

Try to tell that to all F1 teams

 

 

Very different running conditions. If anyone has the time to strip and rebuild an engine every two hours then they can run much more exotic materials which would, in normal conditions, lead to premature failure. 

[alanoo]

 

 

 

 special 'low friction coating' 

 

Sounds like DLC. Not suitable for bearings,

 

 

Try to tell that to all F1 teams

 

 

Very different running conditions. If anyone has the time to strip and rebuild an engine every two hours then they can run much more exotic materials which would, in normal conditions, lead to premature failure. 

 

 

F1 engine are not striped every 2 hours since (10+) years... they now do at least 3000km each, very close to LeMans engines in fact.

DLC coating is in fact the main reason they work so well and do not loose power even near their end of life.

 

Btw, DLC is used on production engines too... on low end ones in fact (stupid CO2 rules)

 

In truth, my point was there is no way someone can have something DLC coated, especially bearings, for an acceptable cost; tooling and process costs are just immense for small production parts. There are loads of other bearings coatings used by Clevite/Mahle and so on on production and aftermarket bearings which are way more likely what have been done