mark kibort

I dont like it, but its not a deal killer. I burned about 1 quart all weekend, so its not bad, but I dont like it. There is always a risk in developing something unproven. I dont want to do anything that can backfire and get me blackflaged for leaking oil, smoking, etc. Ill probably try something simple before Laguna, like maybe first just the oil breather like at the oil filling area. Im still investigating this for a change soon!

mk

hacker-pschorr

Ok - can you explain your current breather system?

Bill Ball

It looked stock to me. And from my experience the source for oil loss is the oil filler neck breather line that goes to the throttle housing.

Jim bailey - 928 International

The oil breather system is marginal for a stock street driven S-4 , the GTS added breathers on the other cam cover. Mr Ott and other stroker engines have many variations of breathers ,catch cans ,etc. to limit the amount of oil being blown/pulled into the intake and burned....Joe Fan has had some issues with oil filling his catch can , his car is not dry sumped.

AO

I forgot to add this to my post above.

https://rennlist.com/forums/928-forum/298550-rennlist-928-sponsorship-opportunity-let-s-buy-mark-kibort-a-new-motor-100-each.html

Bill Ball

What I saw of Joe's breather system looks like he has the breather hoses from the filler neck going into his catch can. That's where some further thought needs to be given. In Mark's case, he still has the filler neck breather feeding the throttle housing. A catch can would be a better temporary endpoint. It would be best to temporarily catch can both the oil filler and the cam cover breathers and see where the oil is really coming from. In my car, it's all filler neck.

Jim bailey - 928 International

Joes's upper "catch can" is linked to an additional catch can out in the fender.....plus he vents both cam covers as well.

mark kibort

Now, we have to put the names, Rennlist etc on the car as well!

How about a place right on the side for a big Rennlist sticker with a list of names?

Mk

mark kibort

It looks as though Joes catch can picks up vapors and they condense in the can. If it overflows, it goes to a second can in the fenderwell. I think if i remember, then if that can overflows, it flows back to the oil pan through a fitting on that plate that is not used on the front/top of the oil pan.

with my breather neck. Im thinking a can like Joe has, and then just an overflow back into the oil pan. Or, why cant you just have one small container near the oil filler cap, with a tube leading back to the oil filler tube. Im thinking that way, the oil vapors condense or the raw spash oil fills the can, and then gravity fed back to the oil filler via a second tube located mid oil breather container. thougths?

All we are doing now, is burning the oil vapor and condensed oil that accumulates in the intake and mixes it with the fuel air load. Did you see the video of the blue puffs of smoke on upshifts and after downshifts, when the power is applied? I havent checked the plugs, since the 1st practice session , but Ill have to see what they look like.

mk

hacker-pschorr

And increasing your chances of detonation.

svp928

Mark, you need negative pressure in the sump for anything connected to the oil pan to "drain" back- or it will just blow stuff out of the pan and up the drain pipe.....

mark kibort

It looked like Joe had this set up on his oil venting system.

I'm just a little leary of trying anything that can really backfire on me and end a race! Is the difference between the old motor and this motor, more blow by potential due to the engine having more power, not nessarily more compression?
On decel, there might be greater negative pressure in the intake which could draw more vapor and oil in on decel

Based on what i saw over the 2 race weekend and a good solid flogging of the engine, i dont see much more than a need for a small catch can, as i only used about 1 quart of oil over the weekend.

so, maybe starting out with the oil filler breather hose routed to a catch can might be the best starting point to test.

mk

hacker-pschorr

One thing we have proved over and over on the dyno (with stock 928's and with Todd's car) is detonation is one cause of blow-by.

I am 100% sure you are detonating that motor, so is Todd and I'm sure quite a few people reading this thread and choosing not to post anything.

Todd's motor with almost 30psi of intake pressure has no blow-by.
Why? He has tuned out all detonation. This is with a stock crank, rods, and rod bearings.
Rachel’s car (Tim’s black auto) is also blow-by free since being extensively shark tuned on the dyno.

I'm not trying to say you can "tune out" all blow-by, since a race motor is under a lot more stress then a street motor. But detonating the engine will make it worse and gets progressively worse as the stock breather feeds this oil back into the motor.

We have yet to see a stock 928 on the dyno that was not knocking even a little bit. “just a little knock” is too much in my book. On a race car it’s not acceptable and made worse by feeding oil blow-by back into the combustion chamber.



I am one of the nay-sayers, I still stand by my words. Your motor is NOT tuned, not even close. You are detonating the engine (I don’t care how little) and you are feeding motor oil into the combustion chamber effectively lowering the octane making any knock even worse.
Don’t even try and tell me you cannot hear the knock. On the dyno, standing next to the motor (with the hood open) we could not hear the knock that was being detected by the computer.

Charley B

It's pretty safe to say that the human ear is not the best instrument to detect pre-ignition. It's virtually impossible to eliminate it in a hot race engine, but for any expectation of longevity it's critical to "tune it" out, as much as possible.

hacker-pschorr

Ok, don’t chastise me for this, I’m going from memory here. It’s been a while since I attended any tuning classes on this stuff.

I don’t think Mark is seeing any pre-ignition. Pre-ignition is far more dangerous then “after the spark” detonation.
Pre-ignition (or as some call it dieseling) happens when the combustion chamber is so hot, the air / fuel ignites before the spark goes off. Usually this means the engine is toast since every ignition event gets sooner and sooner as the engine heats up, to the point where parts start to melt. Carbon buildup can help this happen, another reason why the boosted guys run short or non projected spark plugs since they can turn into glow plugs and cause pre-ignition.
Turning back timing to stop this process has little to no effect since the combustion is happening without the spark plug.

Detonation (what Mark’s and most 928’s are seeing) happens after (or during) the spark. Reason why it can be safely (usually) dialed out with timing.

The EFI class I attended by Ben Strader, he had a simple way to describe this. Pre-igniton melts parts, detonation blows them up.


Please do not beat me up for mixed up words. You get the idea (I hope) and my memory is a bit fuzzy on this.