early dyno results
02-25-2011, 10:52 AM
#466
I've mentioned this in a previous post in this thread, but my track car (essentially stock 91 S4 engine) has both passenger side oil vents plumbed into a "T" and then one line goes to the base of the oil filler neck. The other port on the oil filler neck is blocked off (this is the one that "used" to run back to the MAF boot). I used one of Louies oil filler cap vents (on loan from ATB) and from there it runs in a clear hose up in front of the rad to the Mann air/oil separator. I've had the track car at Spokane raceway two or three times, and I really push it hard down the front straight. I don't know exactly what rpms I shift at; however, it's just over 6K...and it's WOT all the way down (over a mile) before I brake and down shift... I nurse it through turn 2 (sharp "U" turn) keeping an eye on the oil pressure.. it does dip..depending on how hard I turn in...but instead of going through there in 3rd (track car has a GT transmission)..I lug in 4th...just because..(I'm not racing to kill my engine just yet LOL). During those track event, I do not ever find oil in the air/oil separator or even any oil in the tube (clear) leading to the air/oil separator. I run Royal Purple 20/50.
I believe the oil pressure drop is likely a combo of volume and entrained air (foaming) issue (like Greg/Louie have suggested).but I haven't seen the oil ejection that Greg was getting either. Maybe there is a fine line between 6krpm and 6500 rpm..that creates that slug...coming out of the cam cover vents???
anyway..thought I would throw out that unscientific data point...
I believe the oil pressure drop is likely a combo of volume and entrained air (foaming) issue (like Greg/Louie have suggested).but I haven't seen the oil ejection that Greg was getting either. Maybe there is a fine line between 6krpm and 6500 rpm..that creates that slug...coming out of the cam cover vents???
anyway..thought I would throw out that unscientific data point...
02-25-2011, 02:38 PM
#468
Rennlist Member
02-25-2011, 02:57 PM
#470
Rennlist Member
I run very long straights,
peg the engine to 6600rpm almost on all shifts where traction is possible
run amsoil
no breathers
no baffles
no spacers
no screens
no accusump
all stock stuff, no mods at all.
no problems!
what am i doing to avoid issues?
you think its the tracks? Ive run Road America, Willow springs, Thunderhill, buttonwillow,*6 different configs), Laguna and Sears point. Its not the long straights! its the oil!
peg the engine to 6600rpm almost on all shifts where traction is possible
run amsoil
no breathers
no baffles
no spacers
no screens
no accusump
all stock stuff, no mods at all.
no problems!
what am i doing to avoid issues?
you think its the tracks? Ive run Road America, Willow springs, Thunderhill, buttonwillow,*6 different configs), Laguna and Sears point. Its not the long straights! its the oil!
02-25-2011, 03:11 PM
#471
Mark, you've stated on numerous threads that you short shift in the turns to keep the rpms down.
So which is it now?
So which is it now?
02-25-2011, 04:51 PM
#476
Rennlist Member
Some Cliff Notes (or a Stalker's Log?)
Kibo, I believe the oil can make a difference!
However, you also indicated "no breathers". Does that mean stock breather set up, or have you eliminated the stock venting set up to the cam covers? If so, how? This, in combination with the oil, may provide some further clues.
There seem several variables at play here, coming at us from:
1. driving, and dyno, conditions, and
2. different motor configurations
Instead of a single cause that fries the 2/6 rod bearings, it seems a combination of unfortunate design compromises for these street cars (crankcase breathing limitations, proximity of crank to oil, oil pan profile) comes together under certain circumstances (high rpm, g-forces other than hard braking, motor configuration) to result in the frying.
What circumstances cause these design compromises to create the toasted bearings, and how they do it, is elusive, because of all the variables involved. Although, Mark A. seems to have some notoriety for replicating the event, for a variety of motor configurations
I seem to have a morbid curiousity about this. Here are some cliff notes of sorts on specifics about the dyno run which jump out at me, and help me understand what may have been coming together to generate the telling result that Greg experienced:
From Post #63:
From Post #127:
From Post #148:
From Post #159:
From Post #161:
I could be wrong, of course, but I keep looking at that temporary oil filler vent set up (pic below), created for this engine dyno, and wonder if it did not play an important role in helping us see how our motors can easily mis-behave (when provoked) ?
I believe the oil can make a difference! However, you also indicated "no breathers". Does that mean stock breather set up, or have you eliminated the stock venting set up to the cam covers? If so, how? This, in combination with the oil, may provide some further clues.
There seem several variables at play here, coming at us from:
1. driving, and dyno, conditions, and
2. different motor configurations
Instead of a single cause that fries the 2/6 rod bearings, it seems a combination of unfortunate design compromises for these street cars (crankcase breathing limitations, proximity of crank to oil, oil pan profile) comes together under certain circumstances (high rpm, g-forces other than hard braking, motor configuration) to result in the frying.
What circumstances cause these design compromises to create the toasted bearings, and how they do it, is elusive, because of all the variables involved. Although, Mark A. seems to have some notoriety for replicating the event, for a variety of motor configurations
I seem to have a morbid curiousity about this. Here are some cliff notes of sorts on specifics about the dyno run which jump out at me, and help me understand what may have been coming together to generate the telling result that Greg experienced:
From Post #63:
I combined these cams with a high tech llifter coating. The result was such low friction that we had to completely shut off the oil cooler, on the dyno, just to get the oil to warm up enough to run the engine. Even during the higher rpm loading, we barely had the water to the oil cooler cracked.
From Post #127:
We ran a "928 International" oil deflector plate in the filler neck location. We did not have enough room to run the stock filler neck, so a 5/8" chunk of aluminum was machined down to fit. Into this, we installed an oil filler and vent fitting into the far right hand (1-4 cylinders are right) rear corner. We then attached a -10 hose to this vent fitting and ran it back and up, into the air filter box. Total rise of the vent hose was about 10 inches.
[...]
Problems with this vent occurred at 4,000 rpms and everything higher. After approximately 60 seconds of running, at these higher rpms, this vent turned into a pretty much steady stream of oil ejection.
[...]
Problems with this vent occurred at 4,000 rpms and everything higher. After approximately 60 seconds of running, at these higher rpms, this vent turned into a pretty much steady stream of oil ejection.
From Post #148:
On this engine, I elected to run all four available breathers from the valve covers to the intake "box". I've been building special aluminum extentions, that sit down inside the head, which are smaller in OD than the factory plastic extentions, that are normally attached to the valve covers, for quite some time. I attach these onto additional valve cover "elbows". I remade the larger factory extentions (NLA) in aluminum (these are brand new pieces, developed and tested for and in this engine.) All four of these extentions, which were designed to keep oil from "splashing" out of the elbows, have additional oil separation built into each of them (new design for this engine.) These "breathers" effectively eliminate any of the oil that normally comes out of the stock elbows, under normal operating conditions....and would make a great addition to any engine that uses the the right rear elbow hooked up to the intake system (all '87-'95 engines.) This piece virtually eliminated all of the oil vapor coming from this elbow...up to a point.
[...]
When running the engine at sustained high rpm's (starting at 5,000 rpms) these four "breathers" would all "eject" massive quantites of oil, into the open plenum, surrounding the air horns! I'm not talking about a "bit" of oil vapor, I'm talking about a massive ejection of oil and air. I have no idea what would happen if we continued running the engine, the oil ejection was so huge that we immediately shut the engine down. We made changes.....but nothing we did would stop this massive ejection!
Note that the oil pressure drop occurred before this ejection! This is very important.
Here's the really interesting thing. After we removed the valve covers and did some measuring...the breathers don't get "covered" up and even have the opprotunity to "eject" until there is over 2.5 quarts of oil, in each head!
Yup, you got it....our engines "pack" oil up into the cylinder heads at high rpms! The drains back to the cylinder heads can't deal with the volume of oil. Once these drains are plugged and the single crankcase breather is a "solid slug" of oil...the crankcase can't breathe...at all. Pressure in the crankcase rises...which further impedes the return of the oil from the head drains.
[...]
My extra "extention breathers" allowed me to visually see this oil build-up way earlier than I could have seen it, if there were no "extra" extentions. If I left the two smaller OD extentions off, I would have not seen the oil build-up in the heads... and would have had no clue why the oil pressure was dropping like a rock. And if I had not been running the engine with a "direct" oil pressure line...and had been using the stock oil pressure dampening through that tiny, tiny hole...I might not have seen the oil pressure drop, at all.
[...]
When running the engine at sustained high rpm's (starting at 5,000 rpms) these four "breathers" would all "eject" massive quantites of oil, into the open plenum, surrounding the air horns! I'm not talking about a "bit" of oil vapor, I'm talking about a massive ejection of oil and air. I have no idea what would happen if we continued running the engine, the oil ejection was so huge that we immediately shut the engine down. We made changes.....but nothing we did would stop this massive ejection!
Note that the oil pressure drop occurred before this ejection! This is very important.
Here's the really interesting thing. After we removed the valve covers and did some measuring...the breathers don't get "covered" up and even have the opprotunity to "eject" until there is over 2.5 quarts of oil, in each head!
Yup, you got it....our engines "pack" oil up into the cylinder heads at high rpms! The drains back to the cylinder heads can't deal with the volume of oil. Once these drains are plugged and the single crankcase breather is a "solid slug" of oil...the crankcase can't breathe...at all. Pressure in the crankcase rises...which further impedes the return of the oil from the head drains.
[...]
My extra "extention breathers" allowed me to visually see this oil build-up way earlier than I could have seen it, if there were no "extra" extentions. If I left the two smaller OD extentions off, I would have not seen the oil build-up in the heads... and would have had no clue why the oil pressure was dropping like a rock. And if I had not been running the engine with a "direct" oil pressure line...and had been using the stock oil pressure dampening through that tiny, tiny hole...I might not have seen the oil pressure drop, at all.
From Post #159:
I could be wrong, of course, but I keep looking at that temporary oil filler vent set up (pic below), created for this engine dyno, and wonder if it did not play an important role in helping us see how our motors can easily mis-behave (when provoked) ?
Last edited by hernanca; 02-25-2011 at 06:47 PM. Reason: Less Fog; More Wit.
02-25-2011, 07:39 PM
#477
Rennlist Member
Watch the videos, there is no short shifting going on. I use the gear that fits the turns, i dont use the "wrong gear" to travel around a turn. thats where you might have been confusing what I had "stated".
the holbert engine was shifted at near redline on every shift, unless I wasnt racing anyone or there was no need to push the car, which was rare.
Thunderhill last years race:
http://www.youtube.com/watch?v=TpZfeUKP8ns
the holbert engine was shifted at near redline on every shift, unless I wasnt racing anyone or there was no need to push the car, which was rare.
Thunderhill last years race:
http://www.youtube.com/watch?v=TpZfeUKP8ns
Last edited by mark kibort; 02-25-2011 at 08:11 PM.
02-25-2011, 07:43 PM
#479
Under the Lift
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OK, I have never seen this warning when driving ever on any 928. I know the sensor trips at 5 quarts. It's a simple float switch. It would seem it should trip a lot if monitored while driving as there are many times when you would expect the level to be below the float, such as hard acceleration.
02-25-2011, 07:45 PM
#480
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Ok..this WAS a good thread, lets keep the amsoil...shift point..venturi..contact patch..gear ratio...Tq/HP stuff out of it.
OIL TYPE has nothing to do with the what Greg is seeeing with this motor. It would puke the same amount of baby oil if it could run with it. .
OIL TYPE has nothing to do with the what Greg is seeeing with this motor. It would puke the same amount of baby oil if it could run with it. .