Discussion and questions related to the course Practical Engine Building
Posting this topic to search for possible solutions to our bearing wear issue.
Engine: Ford 1.6 Ecoboost. Custom turbo with 34mm restrictor, added port injection, Titan dry sump system, MBE ECU.
First ran with stock engine block, 1.6bar boost, 270hp and 420Nm. Ran nicely for 350 SSkm until liners started to distort(common 1.6 Ecoboost issue). Oil temps reached up to 130C.
Went for dry sleeved block next, Wiseco pistons, PEC rods. 2.0bar boost, 300hp and 500nm@3500RPM. Everything ok in dyno. Failed on track after 5km, hole in the block, 2nd rod bearing failed, other 3 had serious wear due to oil starvation. Oil pump Ford OEM, which runs at 45psi constant pressure, not dependant on RPM.
Built up another dry sleeved block, lighter Omega pistons, lighter Saenz rods, Mahle Motorsport bearings. Decided to do stress testing by holding engine in dyno at peak torque for 5x 10 seconds, in 1min intervals. Checked the bearings after, serious wear on rods and even on mains. Oil pump Titan, 50psi pressure@3500 RPM(peak torque). Oil we used until this point was German made Addinol 5W50 Super Racing.
Changed rod bearings. Increased oil pressure to 60psi@3500 RPM. Changed oil to Motul 300V 5W40. Changed oil cooler location from scavenge side to pressure side. Same stress test, quite the same result, seriously worn rod bearings, although mains wear had not progressed any further(we didnt change them after the first stress test).
People with those engines are running stock oil pumps at 45 PSI constant pressure, although most peak their torque around 400nm. Ecoboost engine developer in UK just ran 4 days in dyno around 440nm, said everything looks like new. Using 5W40 oil, stock oil pump.
We are out of ideas, any thoughts would be highly appreciated.
On attached photos there is the upper rod bearing and then a comparison of the lower mains(current one vs the stock 350 SSkm one).
Could this extra 60+ Nm of torque really create such issue here, or are we missing something?
Are you sure the oil galleys in the crankshaft are not plugged (or leaking by missing a plug)? Normally the rod bearings are fed by oil that flows through the crankshaft.
Or perhaps a main bearing that is needed to feed the crank galley was installed backward preventing oil reaching the crankshaft oil galley.
Any chance your dry-sump installation has somehow prevented oil from reaching the crankshaft?
The crankshaft is the same (and same configuration) that we took out from the stock engine, which did not have this issue. Same for the dry sump installation, it worked just fine at lower power levels. We basically have gone through 3 different engine setups: stock with 1.6 bar boost and two sleeved ones with 2 bars of boost. Seems like oil struggles to keep between the journal and the bearing when we switch for the more powerful map, but the torque difference is really not that big.
We could go for another new set of bearings, test them with lower boost map, check the bearings and if they look fine, only option could probably be to add more oil pressure?
I do not think your issue is the power level, I think the problem must be some mechanical issue that hasn't been discovered yet.
Did you use plastigage to check your bearing clearance? Have you inspected the crankshaft journals (diameter, roundness, taper (although there are no signs of that issue), and the rods/bearing bores for size / roundness?
You are doing the right thing running the engine on the dyno then disassembling for inspection.
Good luck with your investigation...
We did not trust Plastigage enough, so we bought Mitutoyo bore gauges and micrometers for measuring everything reliably.
I wish we did this type of dyno testing before the first sleeved block blew up, as it took a lot more with it than just bearings- full block was scrap, turbo needed rebuild, new oil pump etc.
By the way, first sleeved block was assembled by a different experienced Ecoboost engine builder in the UK. Current block is our own assembly now. Basically only changes that we have in the whole system compared to stock: power output, sleeves, pistons, rods, bearings.
As for clearances, stock came out with 2 .1 thou, which is bigger than Ford's tolerance between 1-2 thou. I assume it got looser during its 350 competitive km-s.
The sleeved block that blew up came with tighter clearances around 1.4 thou.
Our current one is set at 1.9 thou.
Things that can cause this are -
Low oil pressure at the bearing (which is obviously different to where it is measured) - Should be OK at 60 PSI, unless you are getting a false/misleading reading and this isn't being reflected by the time it gets to the main/rod bearings. Try a head flow restrictor? are you running piston oil squirters?
Insufficient oil flow through the bearing - Unlikely with a decent oil pump.
Insufficient bearing clearance - Recheck, get a second opinion?
Too much bearing clearance - Recheck, get a second opinion?
Oil temperature far too high - Is this being measured?
Very poor quality or heavily contaminated oil - Unlikely (would have to be really bad over that short period of time) but worth checking
Very poor quality bearings - Anything OEM or better should be fine, but worth reviewing
Poor crankshaft journal finish - Get it checked/polished
To cross out a potential issue here- could wrong engine mapping cause quick rod bearing failure? Or is this a longer process in this case, also developing signs on the pistons?
Unlikely. You would melt or detonate a piston/plug/combustion chamber first.
Basically if everything is correct from tolerance aspect on mains and rods.,oil pump and pressure relief valve, etc etc I would consider changing the harmonic balancer. Bearings get beaten up by torsional vibrations. ATI DAMPER, Fluidampr etc...
You said in your earlier post that the pump was also beaten up...
I experienced quite the same thing once when used very aggressive ignition timing at hight load even without knock since i was using very high octane race gas. Basically i passed MBT point big time and it caused wearing of rod bearings very fast- just after 5 consecutive runs on the drag strip brand new bearings were done. I was lucky to decide checking them out after the event finding out major wearing out.
georg1970, your experience is something I am afraid of. With current situation we have the following data:
1) Stock engine, ran well when we did the disassembly at 350 SSkm. Rod bearing clearance 2 thou. Tuned by tuner1.
2) Sleeved engine with stock oil pressure pump. 1.4 thou clearance. Tuned by tuner1. Threw a rod after 5 SSkm, all other rod bearings were seriously worn as well.
3) Sleeved engine, Titan dry sump pressure pump with added oil pressure. 1.9 thou clearance. Did 3 series of stress pulls on dyno, each time took out dead rod bearings. Tuned by tuner1.
4) New sleeved engine, and as stock was the one that worked, tried to restore as many factors from it as possible. Stock oil pump, 2 thou clearance. Did 2 series of stress pulls, both showing healthy bearings. Has now done about 75 SSkm total with bearings still alive. Tuned this time by tuner2, who added lots of fuel to previous tuners map and pulled back a little ignition. And he got same power figures at 1.5bar boost instead of previous tuner's 1.9bar.
The map is now the source for our concern, as "the tuner" is one of the factors that would make sense now for our previous failures. Only thing against this is the stock engine running without issues with tuner1 tune.
Seems I need to give EFI tuning course a go to dig deeper...
Well, what i had done after finding my bearings being worn out was increasing bearing gap from 0.03mm to 0.07mm and change the engine oil to thicker one 0w60 to prevent it from happening again.