PF

The same to you! Fantastic that these although vastly improved old cars can match modern cars at that level!

And thanks to people like Mr Mount and their knowledge we can keep doing it and hopefully keep our little engines in one piece.

Voith

Well forgive me for not living anywhere near a decent racetrack. I don't think It would be that hard to rebuild a stock engine in a hurry with a stripped out 951 and the super dominating bearing killer aftermarket ledas installed.

I don't have a use for such a racer so instead I am trying to build something spectacular and I have time to do it and elaborate everything to death in the meanwhile.

Please explain in technical terms the difference between Leda and Turbo cup's original Bilstein suspension, I'm sure there are some pretty big advancements in there somewhere for 2-5 seconds faster X lenght lap.

Gas shock is a very simple peace of technology that was invented by Bilstein and havent changed all that much in 30 years, the only difference is how good is it set up for the given task.

Raceboy

Having better bearings is good (at least bearings that don't desintegrate with normal use) but to be honest I would rather choose oil that has the best shear resistance possible in order to prevent bearing contact with crank journal. Because that's how this is designed to work.

If oil pressure is dropping during dornering then that needs to be addressed, simple.

For a street car that sees no track time there's hardly any good reason to use dry sump, but if you have twice the power of factory 944 Turbo then good oil cooler is a necessity.
And regarding oils, agree 100% with Michael, only todays racing oils are on par with premium oils from 30 years ago.
I exclusively use Motul 300V Le Mans 20W60, ester based oil that is in fact used by real race teams in Le Mans etc.
My 2.5 16v turbo motor doesn't seem to care that I rev it to 7000rpm running 1.3-1.4 bars of boost

PorscheG96

Are the premium oils like Swepco and Brad Penn that everyone loves so much considered true racing oils in this debate?

951and944S

Pretty tough call and oil is as controversial as any topic where someone's preference is always "the best".....Ford vs. Chevy, Chocolate/Vanilla.

The thing is, all companies have test methods and data and claim that their additive packages are best.

For instance, some would say that at least some detergent or corrosion/rust preventative necessary and other companies state that any additive that displaces the quantity of other additives is not correct.

So....again, if you have experience with Motul or Swepco and it works for you, then you'd be prone to stick with that.

The myth that there's one correct oil is nonsense because the choice depends on factors like target operating range, temperature, engine clearances, etc.

Back on topic with the MM rod bearing mod, I think not only is the bearing a higher quality, but when you read about oils, and the forces that oil designers are faced with, you'd learn that it's the center of the rod bearing that's under the most load because as oil is "squished", it travels the only path it has, outwards to the side clearance. Knowing that these bearings are narrower, it seems logical that there's more a quantity of oil where the shell used to extend across the entire cap and big end. There's a term for this oil, it's "hydro" wedge or something or other and I think this could play a part in prolonging the life of the bearings at high rpm and also deliver more expended splash to the cylinder walls.

Either way...., I'm not changing horses in mid stream. gonna stick with the Swepco and inspect these bearings again after this season is complete.

If all's good, it'll definitely be a proven winning formula.

T

gruhsy

Question for Michael on the bearings. How well would you think the H-bearings and the ACL's would stand up to a temporary low oil condition compared to the Glyco's? Eg. fast leaking seal or gasket.....oil light comes on and you shut down engine kinda situation. Hypothetically speaking.

michaelmount123

First, understand that NO bearing will stand up to a loss of oil film. The rotating rod rides on an oil film, and it is that film that provides separation and prevents metallic contact with the bearing. Since the oil is incompressible, tremendous loads are transferred to the bearing and that's why the bearing construction is critical. The H bearing's value is in the beating it can take - but only if there is that critical film of oil.

Will the bearing survive in a low oil pressure situation (oil light comes on)? If the engine is shut down before the oil film goes away, then yes. Keep in mind that RPM, load, duration all contribute to how long the film will protect the bearing. The H bearing is far tougher than the Glyco, so it may survive a bit longer, but do try not to go there!

michaelmount123

Here's another important consideration in protecting your rod bearings: It's not only oiling system issues that can take out a bearing. Your tune is just as important as lubrication. Detonation, mild or worse, can easily cause a rod bearing failure. What happens is the uncontrolled combustion beats on the piston and squeezes the oil film out of the rod bearing. Many who lose a bearing will presume the root cause was the oiling system, when it was the tune that caused the damage. Those that experience constant bearing issues should look into their tune-up.

Further, you have to look past the tune at WOT. Those long sweepers where you're on the edge and modulating the throttle to save your life... Now you're in an often neglected area of tune: partial throttle, high RPM, high load. Is your tune correct in this situation? Your timing and fuel may be golden at WOT, and way off at partial throttle. Think about it.

mikey_audiogeek

Hi Michael, interesting point.

Is there anything about cyl #2 that makes it more prone to high cylinder peak pressures? (detonation etc)

Cheers,
Mike

951and944S

Unfortunately I can vouch for this......, fueling problem, bad lean misfire in several corners near end of an enduro in the lead and I instructed my son to go for it. Newly ceramic topped pistons burned to ash on top, #2 & 3 bearings wiped, #2 piston scored and rod came out the block. Engine made it to finish and let go several laps into the next sprint.

Michael....., I've been in the transmission business most of my life....., some bushings in automatics have divots like a golf ball that act as small reservoirs to hold the oil longer on it's way out.

Is there a reason these type surfaces aren't used on main and rod bearings...?

In some of the positions these bearings are used, say in a bolt on tail section for the output yoke, they aren't even pressure fed and last 20+ years and are sometimes in spec , still original from the 60's and 70's.

As anyone who has ever slung a drive shaft on a launch knows, there's no shortage of force on an output yoke.

T

333pg333

Interesting idea. Wonder if it affects the integrity of the bearing with less material? Surface area would be decreased on the absolute face but increase overall. You'd have to assume that someone would have thought of this somewhere along the time of bearing manufacturing.

951and944S

Was looking around on the KS site this morning for an actual engine bearing where this type surface is used. I remember seeing it there a year or two ago and thinking to myself that engines have finally caught up with transmission technology....LOL.

In all honesty, engines are boring compared to automatic transmissions.
There is a lot to learn in autos because companies introduce new models (sometimes they are forced if competition introduces a new 6 speed for example), sometimes before they are really ready. There are failures not long after sale and they have to be addressed quickly and correctly or the car manufacturer will take a huge hit in reliability reputation, not to mention the warranty claims losses.

You wanna learn about lubrication, control, distribution, etc. Look at automatics. Some overdrive planetaries spin at 10,000 rpms and are fairly large by engine parts comparisons ...so, a lot of centrifugal force sling.

Lube dams, varying orifices, specially designed bearing races, bushing surfaces, etc., all designed to capture, hold and make the most of available lube.

Found this on the web though just for an example of the lube retention surface.....,





I had mentioned in another thread, another relation to automatics...., the oil pump design and how automatics had left the gear type behind years ago due to their inefficiency compared to rotor/vane types.

While I was looking around at the KS site for the divot surface engine bearings I know I had seen there before, I came across this, which is pretty good evidence that these type pumps way outperform a gear-gear positive displacement design.

http://cdn.kspg.com/fileadmin/media/...brennung_e.pdf

I do believe that the 944 pump could be converted to a rotor/vane pump since the both work in a recessed pocket but I am still not convinced that the 944 and 928 oil pump isn't up to any race task as long as it's fed a reliable source of oil.

T

michaelmount123

I agree with your statement (above), T. The pump design is not new and historically proven reliable. I'd only add the word "suitable" before the last word. Well said, BTW.

Your oil retention bearing is interesting. I'd be curious what a Mahle/Clevite or ACL engineer would have to say about it. Conceptually it seems valid.

gruhsy

What about adding a second electric oil pump plumbed into the system?
The yellow turbo 968 that belongs now to soloracer has a pump...belt driven, to oil the turbo
The engine was built by Jon Milledge....knows a little bit about these engines

refresh951

A Honda engineer who specialized in oil systems did some preliminary analysis a few years back and he believed the 944 oil pump worked "to good". His belief was that the pump resulted in cavitation on the input side starting at about 5500 rpm. As I recall oil viscosity played a significant role as to how early the cavitation begins. I would be interested in your thoughts on this theory.