BC

'G96
said:

I don't agree with this part:
quote:
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It will happen more frequently and sooner on a S4 then on an early engine
with the same cornering capability due to the fact that there are less
places for the oil to stay in the head and the paths in the head are
smaller. So more oil stays in the pan.
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Unless he's describing the early engine that will leave more oil in the pan, not the S4.

..To Clarify - yes, I am describing an early 928 engine with the "2v" heads, or as you would like, the "944-like heads". The oil drains back alot more easily. MOre oil in the pan, less oil-pickup uncovering.


...I also think a good point was made. The situation has never come up on some highwinding engines. What did they do right? We just have to figure that out and do it.

Brendan
<img src="graemlins/burnout.gif" border="0" alt="[burnout]" /> <img src="graemlins/burnout.gif" border="0" alt="[burnout]" />

Huntley Racing

Going back to the original Tech article I wrote for the 944 rod bearing failure issue. I added in these posts a very telling fact, we have personally seen the oil pressure drop on a 944 simply running on a stationary dyno. This occured for several reasons: The car had been running on the dyno for some time and the running temps of the oil were very high (like on the track), the car was being tuned which required running the car to redline (high RPMs), and the owner had followed the 'incorrect' advice to run 1/2 quart of oil over the top of the dipstick causing undue windage. Again we could see this happen as soon as the RPMs got up above 5000 RPMs or so and get worse as they went up. The #2 rod bearing fails more often first because is is farthest from the high pressure oil source. However all the bearings can and will eventually fail from this if they are used in the DANGER conditions mentioned.

Bri Bro

What my interest in this? I am in the middle of pulling bearing and replacing seals. I measured the connecting rod journals and they were at "new" specifications. I still don't know why #2 rod goes first but I don't see a problem yet. Still looking...

My rod bearing (14-Feb-02) 125K miles.

aka 951

Do you have a chip (increased rpm) or do you ever autocross or race your car? And how long have you had it? Thanks for the info. Looks like your rod bearings are in almost new condition apart from the minor galling.

Bri Bro

I got the car out of Texas about a year ago, It had the AutoThority stage 2 with a Lindsey boost enchancer. The last owner did a couple of Drivers Ed a year. I spent most of the summer getting rid of some nasty electrical problems (that why I got the car for $6k) so it wasn't on a track. I would run it up whenever I had the road to do it and I touched the rev limiter several times before I got the feel of the boost.

Jerry

I agree with at least one thing aka951 said:there is no reason to rev past 6K as you can go faster by shifting into a higher gear somewhere between 5K and 6K. In 5th gear 6K is 140 or 150 mph. I admit is's more fun to high rev and it sounds nicer but I do many DE's per year with my 88 chipped 944ts and it has 170K miles without re-building the head or replacing any bearings yet. I plan to put new bearings very soon before my luck runs out, but I'll still stay under 6K.

Danno

Yep, why bother revving it out when your car makes more torque at 4500rpm than at 6000rpm+ anyway? And on modified cars, the torque-curve drops off even faster!

smokey

Thanks Mike B re how to post pictures. I just finished having my '86 951 engine rebuilt by Henri Costa of Refined Motorsports in Toronto, and I thought I'd share what I have discovered about the No. 2 rod bearing. Henri worked on the Rothmanns Turbo Cup cars in the mid-1980's, and he said that they never had a problem with the No. 2 rod bearings in any of the engines. These cars were prepared by the factory for about 300 rwhp, and they rebuilt the engines after each season. He worked on Richard Spenard's car, among others. Henri's view is that the main reason for the damage to the No.2 bearing is low oil level, and this has some logic.
Almost all of the engines that have the No.2 rod bearing spin have high mileage, and they use a lot of oil. My car had 100k miles, and it used a liter of oil per driver ed day, or for about 80 minutes on the track. I had to monitor it very closely. Each time the oil is a little low, the number 2 bearing is starved because it is the last in line. It seems to happen very gradually. My No. 2 rod bearing had a lot of copper showing and was loose in the rod, so it was just a matter of time. Henri carried out a number of modifications in the rebuilt engine to delay the problem, and I plan to limit revs to 6k and continue to check the oil religiously. I drive to and from the tracks, so I need reliablity.
The modifications consist of an added baffle with a trap door to control the uphill oil surge on left-hand turns, and a collar around the oil pick-up to reduce aeration. The crank is knife-deged to reduce windage, and cross-drilled. If I had read this thread before cross-drilling, I would have gone for the radial hole suggested here earlier. Anyway, here are the pictures of the modified sump and oil pick-up.
[img]smokeysump.jpg[/img]
[img]smokeypikup.jpg[/img]

smokey

Hope this works.

smokey

Ski

Is that the Powerhaus option,,David sells the "trap" door and modified pick up,,,it is 295 exchange.

smokey

It's basically the same idea as the Powerhaus modifications. Milledge offers something similar , including modifications to the oil passages. Mine were done by a local machine shop. Short of a dry sump system or Accusump, this seems to be the best safeguard. Overall, we have to remember the golden rule: check the oil level before every run. And change the rod bearings every XX miles.