early dyno results
#241
Rennlist Member
Excuse my ignorance, but if it is pressure differential between the CC and heads, couldn't you just plumb those "top center" openings to the cam covers to equalize things?
#242
Track Day
Join Date: Nov 2010
Location: Yokohama, Japan
Posts: 19
Likes: 0
Received 0 Likes
on
0 Posts
umm, if the CC is highly presssurized
tying the CC to the heads will equalize the pressure but will, most likely, lead to massive oil leaks from the cam covers, end caps etc. The vents in the cam covers are there to provide a slight negative pressure to stop the oil seals from leaking.
If you look at the size of the oil return passages and remember that they inclined at 45 degrees (effective incline angle is increased/decreased by cornering) you can see that the oil has little inclination to return.
If you look at the size of the oil return passages and remember that they inclined at 45 degrees (effective incline angle is increased/decreased by cornering) you can see that the oil has little inclination to return.
#243
Race Director
My car does have an accusump. Does it solve all of the problems, no it does not. We are on our 3rd iteration of the oil pumping issue fix and while better it is not solved.
Hopefully I am incorrect but I assume the prayer part of your comment has to do with your dislike & disrespect for its builder . I really try to stay out of this kind of crap, but 4 years of successful campaigning in ORR @ over 200 mph is not accomplished with a prayer, although I do say one before every run and sometimes in the middle too. If I have misinterpreted your comment I apologize in advance.
Hopefully I am incorrect but I assume the prayer part of your comment has to do with your dislike & disrespect for its builder . I really try to stay out of this kind of crap, but 4 years of successful campaigning in ORR @ over 200 mph is not accomplished with a prayer, although I do say one before every run and sometimes in the middle too. If I have misinterpreted your comment I apologize in advance.
Do you have data logging? Something that shows the amount of time spent at WOT during a run? I would guess its a fairly high % of time on course?
#244
Under the Lift
Lifetime Rennlist
Member
Lifetime Rennlist
Member
You don't want a closed circuit here. The inherent blowby in the crankcase needs to get out of the motor, not into the heads. I crudely calculated about 75L blowby per minute in a 5L motor at 6000 RPM. That's assuming an effective 1% blowby. So, at that rate you would need to evacuate over a liter per second. Feel free to critique that.
#246
Under the Lift
Lifetime Rennlist
Member
Lifetime Rennlist
Member
I need to back up for a moment...
Greg, you've built and I presume dyno'd bunches of these motors. What's different here that produced such a pronounced problem? Is it simply that you had 4 extensions on the cam cover breathers this time?
Greg, you've built and I presume dyno'd bunches of these motors. What's different here that produced such a pronounced problem? Is it simply that you had 4 extensions on the cam cover breathers this time?
#247
Addict
Lifetime Rennlist
Member
Lifetime Rennlist
Member
Right you must vent the blowby but figure out how to keep the oil in the sump so the oil pump has something to pump. Who was it who plumbed into the exhaust used a angled fitting to create a vacuum then on a group dyno run fogged up the shop which oil vapors ???
#248
Addict
Lifetime Rennlist
Member
Lifetime Rennlist
Member
Bill this was the FIRST engine dyno runs where you can load it and hold it at high RPM. All the dyno jet runs are over in SECONDS . Even Greg's chassis dyno can not dissipate heat fast enough for a sustained run.... So the HUGE delta is the dyno and extended running ....like an open road race or California auto club Speedway !
#249
Under the Lift
Lifetime Rennlist
Member
Lifetime Rennlist
Member
Understood, and nothing I have seen so far keeps the oil from traveling out the breathers. The oil vapor and droplets in the high-speed stream just fly around the various diverters. The copper mesh people have added probably just makes it worse once it gets saturated as there is no way for the oil to go backwards against flow as long as you are on the throttle.
#250
Former Sponsor
My car does have an accusump. Does it solve all of the problems, no it does not. We are on our 3rd iteration of the oil pumping issue fix and while better it is not solved.
Hopefully I am incorrect but I assume the prayer part of your comment has to do with your dislike & disrespect for its builder . I really try to stay out of this kind of crap, but 4 years of successful campaigning in ORR @ over 200 mph is not accomplished with a prayer, although I do say one before every run and sometimes in the middle too. If I have misinterpreted your comment I apologize in advance.
Hopefully I am incorrect but I assume the prayer part of your comment has to do with your dislike & disrespect for its builder . I really try to stay out of this kind of crap, but 4 years of successful campaigning in ORR @ over 200 mph is not accomplished with a prayer, although I do say one before every run and sometimes in the middle too. If I have misinterpreted your comment I apologize in advance.
It was just my belief that he never got very far in solving the oil issues, with these engines.
As I mentioned, I've got engines with Accusumps on them...and I believe that is the only salvation, for these engines. Certainly, your engine is also going to pack oil into the cylinder heads and thus not have much oil "left" for the oil pump...it isn't much different than all the other 928 engines...except it is bigger. The Accusump is able to provide enough of a "buffer" to keep things supplied with oil.
I don't think is the "cure", I think this is a "patch" (which I've used) to keep these engines "alive". If anything goes wrong with the Accusump, I'm sure that disaster would follow, very quickly. There's enough to "pray" about, right there!
Clearly, a lot of things have changed, since Marc built your engine....development on these engines has made that technology very "old school". The current pieces barely resemble the pieces that Marc used. We have finally gotten to the point where we've worked through a lot of the problems that these engines have had, but there are still some nagging problems that are left over (oiling is one.)
However, it is great that your engine still runs well and still satifies your needs. That is a testimony to the careful assembly work that Marc did!
#251
Archive Gatekeeper
Rennlist Member
Rennlist Member
The day before SF10 we did more than a dozen separate Sharktuning runs over four hours with Mark's racer on Greg's Mustang dyno. If I open all the plots and count all the WOT dots in all those runs, I get about 1300. Since we're logging at 10/sec, that means that there was a combined WOT time of 130 seconds. And anyone that was there can vouch for the amount of smoke that was coming out of the dyno's cooling vents.
130 seconds of WOT on the engine dyno takes, uh, 130 seconds.
130 seconds of WOT on the engine dyno takes, uh, 130 seconds.
#254
Former Sponsor
#255
Former Sponsor
Only if tested by dropping from a C-130 Hercules...it is New Mexico...and Lord knows there's been more than one thing dropped, out there!