APS

Hi Guys,

There's been lots of discussion lately about the strength and suitability of the stock Niassan con rods to handle forced induction safely.

It's been on my mind for some time and after viewing many pictures of damaged con rods from FI VQ engines this started to get the better of my curiosity as we at APS have not seen or experienced a con rod failure to date.

After carefully viewing pics of many damaged rods I have come to the conlusion that many of these rod failures have been caused by bearing failure (big end bearing spun/spinning in the con rod big end).

You see if the big end bearing spins then this causes the con rod to seize momentarily and then the con rod either bends or breaks as you would expect.

The best quality after market con rods are not designed to cope with a big end bearing failure, at this point you will either destroy the crankshaft journal or break the con rod, so now we are at the point of my post, what causes the big end bearing failure ?????

I firmly now suspect either oil starvation or very high oil temperature is the real cause of the bearing failure (hence most con rod failures) and I intend investigating this issue at much greater length now.

APS designed and produced a larger Hi Volume air cooled oil pan with much improved baffling around the oil pick up, I suspect that this had reduced if not eliminated the oil starvation problem and hence why APS have not experienced con rod failure at sensible power and boost levels.

In any event as this was on my mind (I could not sleep last night thinking about this issue) I thought I would share my thoughts with you guys, I welcome any input or feedback from you and I hope that we are onto the real cause/diagnosis of con rod failure with FI engines.

Thanks

Peter


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BriGuyMax

iTrader: (4)

Finally a thread with some actual sense besides all the standard "stock con rods are cr@p" threads.

Seriously though...people are so quick to jump out and make assumptions that it just makes me sick. EVERY person that I've talked to that actually KNOWS THEIR WAY around a VQ motor has said that the stock internals are plenty strong.

Brandon@Forged

Are you sure it isn't the C&CAS wire?

Brandon@Forged

Peter, how long has APS been using the shielded wire?

Znitro

This is something I said when I first did the tear down of my 8lb Stillen SC motor with 3k on the ODO

The attached photo shows how the rod bearings were being "pounded" at the center of the cap and main rod body mainly due to rod stretch while over reving or possibly oil related issues.

BTW Peter,
I just dropped my car off at BrainStorm today for the APS TT !!

APS

Thanks, I just trying to make sense of this con rod issue.

I'm nearly sure this is a real lubrication/oil starvation issue on the VQ engine causing significant crankshaft and con rod damage.

I believe it's more likely an oil starvation issue as the stock oil pan is very ordinary and does not have much provision against oil surging (oil running away from the main oil pick up).

Thanks

Peter

APS

This crank angle sensor issue was causing intermittent detonation (scattered timing) and certainly does not help the issue, though I now believe the con rod failure issue is more likely caused by oil starvation after looking closey at many pics of failed rods and damaged crankshaft journals.

Thanks

Peter

APS

All production APS Twin Turbo systems have the improved crank angle sensor loom.

Peter

Brandon@Forged

ALL? Every one of them since the first one? Oh, I assumed since you didn't post anything about it until fairly recently that APS had just found out about it (which telling everyone was very kind of APS).

phunk

iTrader: (21)

Peter, I agree with your thoughts. My engine held up to a lot of power and abuse for a long time... had I seen the stock internals before hand, I would have pushed it even harder... but at that point I was listening to all the things everyone else was saying about how bad the stock rods are.

Upon taking apart my engine, I noticed the rods to be pretty damn good for a stock rod... the rod bolts a little small, but HP doesnt really break a rod bolt... thats RPM.

There was only one part of my internals that even looked PARTIALLY worn after all that abuse (not only was it making the proven power, but I drive the thing like i stole it... flooring it at every light, burnouts, donuts, street racing, long duration high speed)... was the top shell rod bearing.

It was the only worn part at all... Matter of fact, why dont I go take a little picture... BRB.

phunk

iTrader: (21)

unfortunatly i have no idea how to use a digital camera to take good pics...

phunk

iTrader: (21)

i guess a good question would be how much oil is actually in the sump when the engine is running... that is if we are going to consider the oil pickup and lack of baffles in the stock oil pan

i would also wonder if it was surging from oil leaving the pickup... wouldnt the head starve first being further away? I noticed no abnormal wear to the lifter surfaces or cam journals... I would think the high speed of rotation of the crank would help feed the rod bearings well with the centrifigal "throwing" of the oil towards the rod journals

APS

To be frank it never entered my mind to discuss the crank angle sensor issue, it was no big deal at APS. I would have thought that the other companies producing FI systems would has identified this issue during development, obviously not.

Thanks

Peter

APS

That's good to hear Charles and I think we are onto the real issue hear regarding con rod failure.

Correct and I also noticed that the big end bearing were in good shape when we stripped our engine for inspection, I think this is due to the extra oil capacity and oil cooling delivered by the APS oil pan, we have much improved baffling around the oil pick up which helps to reduce oil starvation.

Well with that the top bearing shell worn it's most likely from very slight detonation though (maybe it's also related to oil starvation), thanks for your input Charles, let's hope we are on the right trail to solve this bearing/con rod problem.

Thanks

Peter

APS

Charles I suspect that the engine oil runs away from the oil pick up with the stock oil pan under certain road conditions, hence the oil starvation to the bearings.

I guess this depends on what gets the oil supply first, is the head lubricated first (which is very unlikely) and then a particular crankshaft journal last or vice versa, I would need to have a good study of the oil lubrication circuit to know for sure.

I've seen some funny oil lubrication circuits over the years such as the subaru WRX engine which supplies oil to the cyl heads before the rear main bearing. The number 4 big end bearing is always the first big end bearing to fail as it's the very last component to receive oil lubrication.

Thanks for the pic Charles, very interesting, by the way how many miles had that engine done before you stripped the engine?

Thanks

Peter

kosmic

Just a quick post so that I can get subscribed to the thread. Maybe FI will be in my future after all! (spending 18-20k for a built motor / fi just never sounded appealing to me)

Peter, do you think synthetic oil would also help in addition to the APS oil pan? Upgraded oil pump maybe? Oil cooler? (That's all I can think of at the moment...) Might as well over-insure the oil supply for a extra grand or so, eh? It's a lot cheaper than a full engine build up.

Thanks

jeffw

Seems like a good test for your theory would be to find someone that had a stock engine plus APS TT kit, but has since torn down to do an engine build-up. Then, see how their bearings look. Of course, you want someone that didn't run other forms of FI before going with APS TT (and maybe even someone that hasn't ever been to a race track).

Do you think potential customers fearing grenading their engines is cutting into TT sales?
--
Jeff

BriGuyMax

iTrader: (4)

Anyone know what the big end rod bearings are MADE OF? I'm still N/A, but I've been to the "real" track a few times and had an oil analysis done. I wanted to know if my slight excess of aluminum wear is possibly the rod bearings or something else.

gersteinp

iTrader: (1)

Peter-- Do you think that the extra quart of oil enabled by the JWT oil pan spacer will help prevent the oil starvation issue by both reducing peak oil temp and
preventing oil surge? At $100, this would be a pretty cheap fix.

westpak

iTrader: (19)

So what does this mean for guys doing engine rebuilds, unless they address the oil issue they could still lose their engine, even thought the rods would take more, then the crank shaft would be next in line, either way they would still be incuring high engine wear and tear.