951S: What I can say is that I have blown 2 #2 rod bearings in 2 years sence I have been tracking 951's. My current car has way more HP and I have been runing this set up problem free for 3 years.

What was the oil-level when you realized the #2 blew?

mark944turbo: There is a reason why #2 fails first. When air gets sucked into the oil gallery, the first place for it to go is to #1. But, the mass ratio of oil to air causes #1 to get mostly oil even when air is being sucked up. Then the air goes to #2. I have seen #3 fail, but never #4. This is because #2 fails first, there is never time for the air to make it to #3 and 4, even when a lot is present. Actually, even if the air is making it to 3 and 4, it will always have been getting to #2 longer.

The rod bearings are fed sequenzly in a row one after annother right? If yes where is the logical point in your idea?

Why does no one help us? I am sure there is people who know the real problem - but maybe not how to fix it?

As long there is no proof for any solution I would do nothing described here. Once again Honda is running much higher rpm on let us say cheap cars and there is no problem at all. I don't know...
kind regards Frank

 

A little OT but..

Do 3.0L 16V engines suffer from the same rod bearing issues as the turbo/ na 2.5 engines?

 

Turbinek, what is my logical point???

My point is trying to explain why number 2 fails first.

Yes the 3.0 engines have the same problem.

 

Mark944turbo
The point I don't understand is:
oil -> #1 -> #2 -> #3 -> #4 -> and only #2 spins??

 

Yes, because when a small amount of air is sucked into the pickup, #2 is the place it is most likely to go. It would be number one if it was solid air, but it is usually a mix of oil and air, so the oil falls into #1 while the air makes it to number 2.

 

Well the oil is supplied more in parallel than in series.

The oil comes from the oil pump and into an oil galley for rod and main bearings. The galley supplies oil to all the bearings in a similar way as the intake manifold supplies air to the 4 cylinders.

Anyway this means the the #1 gets the first bit of oil and then #2 gets some as well. Then 3 then 4. but it is really different oil. The rods are feed through the mains such they are really down stream of the main bearings.

Here is an oil flow diagram of these engines.

 

I though that the firing sequence on out cars were 1-3-2-4 correct? which means that pistons 1 and 3 move together and 2 and 4 move together. If that is true, why in the diagram does it show fire sequence of 1-4-2-3? as in 1 and 4 are together and 2 and 3 are together?

 

Hey hosrum,
The diagram is correct.
Ignition sequence is 1-3-4-2

 

Are you sure? there is a dashed box around some bearings on the crankshaft (that should be the rod bearing right?) then, 1 and 4 are together, 2 and 3 are together. Or maybe i am seeing things the wrong way, it's late here

 

M758
Thank you very much - your chart really helps a lot!

I still doesn't make sense to me with this air hypothesis.
My engine blew 6 years ago - #1 o.k. #3 o.k. #4 o.k.
#2 bearing halfs b r o k e n and no longer in place (kind of messed in each other!!!!) 86' 951.

kind regards Frank

 

Yeah, that diagram is correct - as J Chen stated, correct firing order .s 1-3-4-2, putting 1-4 together and 3-2 together.

Sam

 

Here is my pan fresh back from Rennlister Bob Patterson who welded in a flapper door for me. Still searching for a crank scraper.

 

So how does the flapper door work? when turning is it supposed to move the opposite direction to hold the oil in place?

 

Hi hosrum,
The flapper door is in reality a baffle.
It's there to cut down the amount of
oil the will climb the oil pan wall when making high G left hand
turns. The flapper door is there to
releive oil back to into the pan.

 

You didn't mod the oil pickup tube? lindsey sells a kit 9which i am interested in) that comes with a flapper door and a band that welds around the pickup tube