George and Rich still alive....189mph 928-S4? Flatline...
06-19-2007 | 02:38 PM
#211
Rennlist Member
Joined: Feb 2003
Posts: 29,817
Likes: 185
From: saratoga, ca
Ketch, go see post 162. all the discussion was based on this. subsequent comments were very clear to point out that the load on the car was the issue. Certainly you are right if somethign failed, it could have been do to the engine making more HP and using that extra HP vs a car like mine, but that was not the original comment. If you want to dig into anthing ive said here, PM me.
Somethings are lost in the translation, but most all of the things ive posted here is pretty simple stuff. Its a web forum. we are dealing with a lot of people with varied backgrounds and education. When i go over some of this stuff, i dont have a white board, there is no discussion. its one dimensional. The written word, which much up for interpretaion, unless you are real good, and im not!
Please please please, tell me of the direct questions i never answered.
Mk
Here was Hacker's original message that i commented on post #162:
I said after reading Hacker's post :
That i simply not an issue. WOT is WOT no matter what the car is fighting.
if you are max hp WOT, you may take longer to get to some top speed in any gear, but the engine doesnt know the difference. I remeber a discussion i had on the SpeedGT board that started out something like this, where the guy was telling us that the heavier cars with extra ballast, had more load on their engines. Again, same kind of thing, not true. if you are at max HP, then you are at max power. doesnt matter whether you are on a dyno wheel, running up a hill, in 1st gear or 5th gear in a 100mph headwind going 200mph.
the ONLY thing working harder in your senareo below,would be the forces on the gear box, and ironically enough, those forces are greater in the lower speeds and in the lower gears. (the transmision and CV joints are exposed to greater forces in lower gears due to mechanical advantages)
To the fellows point on the GT board, the only extra force or wear on the engine with a car with greater weight, woudl be the extra time it would spend producing max HP, but much of that could be offset by the fact that it would be braking earlier to make the upcoming next turn . (all other things being equal, which most would be)
mk
Quote:
Originally Posted by Hacker-Pschorr
I think many are overlooking the load on an engine fighting the air for an extended periord of time at these speeds.[U] An engine is working a hell of a lot harder to reach 6,000rpm in 5th vs. 4th (on the 5-speed cars).[/U]
I would at least do a refresh on a motor with that many miles, head gaskets & rod bearings for starters.
Mk
Somethings are lost in the translation, but most all of the things ive posted here is pretty simple stuff. Its a web forum. we are dealing with a lot of people with varied backgrounds and education. When i go over some of this stuff, i dont have a white board, there is no discussion. its one dimensional. The written word, which much up for interpretaion, unless you are real good, and im not!
Please please please, tell me of the direct questions i never answered.
Mk
Here was Hacker's original message that i commented on post #162:
I said after reading Hacker's post :
That i simply not an issue. WOT is WOT no matter what the car is fighting.
if you are max hp WOT, you may take longer to get to some top speed in any gear, but the engine doesnt know the difference. I remeber a discussion i had on the SpeedGT board that started out something like this, where the guy was telling us that the heavier cars with extra ballast, had more load on their engines. Again, same kind of thing, not true. if you are at max HP, then you are at max power. doesnt matter whether you are on a dyno wheel, running up a hill, in 1st gear or 5th gear in a 100mph headwind going 200mph.
the ONLY thing working harder in your senareo below,would be the forces on the gear box, and ironically enough, those forces are greater in the lower speeds and in the lower gears. (the transmision and CV joints are exposed to greater forces in lower gears due to mechanical advantages)
To the fellows point on the GT board, the only extra force or wear on the engine with a car with greater weight, woudl be the extra time it would spend producing max HP, but much of that could be offset by the fact that it would be braking earlier to make the upcoming next turn . (all other things being equal, which most would be)
mk
Quote:
Originally Posted by Hacker-Pschorr
I think many are overlooking the load on an engine fighting the air for an extended periord of time at these speeds.[U] An engine is working a hell of a lot harder to reach 6,000rpm in 5th vs. 4th (on the 5-speed cars).[/U]
I would at least do a refresh on a motor with that many miles, head gaskets & rod bearings for starters.
Mk
Originally Posted by Ketchmi
Mark, you just don't get it. I was in fact comparing a 420hp engine to a 320 hp engine, that's the just of this whole discussion. This is not a theoretical numbers application, this is trying to solve a real world problem. We are not discussing the loss of the 9th planet, we are discussing George's engine. Not your engine, not some engine that doesn't exist, not some towing application, very specifically this thread is about George's engine and this specific application. Please either keep it somewhat aligned with what we are attempting to resolve or kindly step aside quietly and we can get back to George's application. Road racing rotational forces are in fact very different than THIS APPLICATION as you are not under the same connecting rod loading for the same amount of time. You are accelerating and de-accelerating constantly rarely spending much time actually at the rpm's that George is let alone your car cannot generate the loads that George's superior horsepower can achieve. If you cannot grasp the fact that we are discussing George's specific engine and operating parameters, please feel free to start your own theoretical thread involving rocket engines towing block walls.
If you would open your mind a bit you would see that we are now agreeing on several points, amazing how your posts change from your initial stance. It's also amazing how you will never answer any of my direct questions. Please step away from any personal "high level of ignorance" statements unless you want me to start with them also...
If you would open your mind a bit you would see that we are now agreeing on several points, amazing how your posts change from your initial stance. It's also amazing how you will never answer any of my direct questions. Please step away from any personal "high level of ignorance" statements unless you want me to start with them also...
06-19-2007 | 02:56 PM
#212
Drifting
Joined: Sep 2001
Posts: 2,050
Likes: 6
From: Bountiful, Utah
Mark, this whole discussion was based on what happened to George's engine... the thread shouldn't have been steered off on the path you took it. As I said before, thanks for keeping George's thread near the top but at least keep it relevant to what we are trying to resolve. Comparing your car and or rocket engines and or another forum's discussion that has nothing to do with George's engine failure doesn't apply. I believe we have found a new way to destroy 928 engines and would like to keep the thread along those lines.
06-19-2007 | 03:07 PM
#213
Rennlist Member
Joined: Dec 2001
Posts: 25,152
Likes: 87
Originally Posted by Ketchmi
I believe we have found a new way to destroy 928 engines and would like to keep the thread along those lines.
06-19-2007 | 03:20 PM
#214
Rennlist Member
Joined: Feb 2003
Posts: 29,817
Likes: 185
From: saratoga, ca
This was my question before. if the sustain forces are not able to be supported, then stronger rods would have to be use. However, what was the cause, that is the question. we know the forces are easily supported by the 480rwhp engines out there. devek ran much faster for longer and didnt ever have a failure. Anderson and fan have been racing in 4 hour enduro races, 1 hour speed GT races where engine speeds are at above 5000rpm to 7000rpm and at WOT for much of the time.
If this is a oiling issue, what caused it. amzoil was used, so we have good oil. oil pressure was noted to be good, so, what failed? It kind of points to the bearings failing first and then starting to lock up the crank when other parts started to fail. oil contamination due to the cracked block could certainly cause this. especially since all the rod bearings were a little cooked, not just #2/6 as we see in the other failures.
maybe its just risky to run our engines at max output for long periods of time. however, how long was George really at max power. is the run really at WOT the entire time? i know the speed changed from 145ish to 170ish for much of the run, the 189 was only for a few seconds.
the forensics are pretty complicated. It sure would be interesting and helpful to George to really know what failed first and why.
MK
If this is a oiling issue, what caused it. amzoil was used, so we have good oil. oil pressure was noted to be good, so, what failed? It kind of points to the bearings failing first and then starting to lock up the crank when other parts started to fail. oil contamination due to the cracked block could certainly cause this. especially since all the rod bearings were a little cooked, not just #2/6 as we see in the other failures.
maybe its just risky to run our engines at max output for long periods of time. however, how long was George really at max power. is the run really at WOT the entire time? i know the speed changed from 145ish to 170ish for much of the run, the 189 was only for a few seconds.
the forensics are pretty complicated. It sure would be interesting and helpful to George to really know what failed first and why.
MK
Originally Posted by BrendanC
Assuming clean and non-aerated oil, what would the fix be? Thicker oil, higher pressure (it already high), larger or smaller bearing clearances? Custom "Harder" rod bearings?
06-19-2007 | 03:24 PM
#215
Three Wheelin'
Joined: Aug 2006
Posts: 1,765
Likes: 1
From: Atlanta
Well if the crank cross drilling is indeed the problem here than a thicker oil would make it even more difficult for the oil to overcome the centrifical force and get towards the crank center and up the passage heading up to the rod journal. Interestingly the oil pressure gage would read full under those conditions but no oil could be getting to the rod. Higher oil pressure would help. Has anyone ever modified the 928 crank oiling passages?
06-19-2007 | 04:09 PM
#216
Nordschleife Master
Joined: Sep 2004
Posts: 9,429
Likes: 2
From: Not close enough to VIR.
Mike, other than a small increase in drag going through the passages, I don't see why a thicker oil would influence this problem. Also, assuming that the passages are equal diameter, the rod passages are longer than the main passages meaning they would hold a greater mass of oil. The greater mass would exert more force and siphon the oil in from the mains. That is if I'm understanding correctly what you are theorizing as the problem.
06-19-2007 | 04:21 PM
#217
Addict
Rennlist Member
Rennlist Member
Joined: Apr 2002
Posts: 2,197
Likes: 54
From: SF Bay Area
Mike,
The 2/6 bearing failure is a know weakness in the 928 engine. People have attempted
to overcome this weakness by cross drilling the crank and "upgrading" the oil delivery
system (dry sump or accusump). The failures usually occur when the car is in sustained
high g left hand turns at high rpm. I had hoped that my application (low g, high rpm) of
the engine would avoid this situation. I have been able to run 14 events on this engine,
the last 9 with the supercharger, and the last 5 at 160 mph average. So I don't know if
it's an accumulated stress/wear situation, or a momentary lack of oil to the bearings. I
will be cross drilling the next crank. Dave is making arrangements at this moment.
The 2/6 bearing failure is a know weakness in the 928 engine. People have attempted
to overcome this weakness by cross drilling the crank and "upgrading" the oil delivery
system (dry sump or accusump). The failures usually occur when the car is in sustained
high g left hand turns at high rpm. I had hoped that my application (low g, high rpm) of
the engine would avoid this situation. I have been able to run 14 events on this engine,
the last 9 with the supercharger, and the last 5 at 160 mph average. So I don't know if
it's an accumulated stress/wear situation, or a momentary lack of oil to the bearings. I
will be cross drilling the next crank. Dave is making arrangements at this moment.
06-19-2007 | 04:35 PM
#218
Rennlist Member
Joined: Feb 2003
Posts: 29,817
Likes: 185
From: saratoga, ca
i have many sustained, high rpm left hand turns in my racing. i have over 90 hours of actual race time on the holbert engine now.
im wondering if under WOT, if the oiling system can not keep up with the demands under sustained high rpms
how long are you at 160mph. how long at peak speed, 189mph? what were the rpms you were recording at those speeds?
maybe the rpms are high enough that the oil film cant be replaced fast enough by the pump we have stock. maybe a drysump is needed for this kind of oil flow and sustained engine rpms. Or, is it possible that the block cracked first?
mk
im wondering if under WOT, if the oiling system can not keep up with the demands under sustained high rpms
how long are you at 160mph. how long at peak speed, 189mph? what were the rpms you were recording at those speeds?
maybe the rpms are high enough that the oil film cant be replaced fast enough by the pump we have stock. maybe a drysump is needed for this kind of oil flow and sustained engine rpms. Or, is it possible that the block cracked first?
mk
Originally Posted by jorj7
Mike,
The 2/6 bearing failure is a know weakness in the 928 engine. People have attempted
to overcome this weakness by cross drilling the crank and "upgrading" the oil delivery
system (dry sump or accusump). The failures usually occur when the car is in sustained
high g left hand turns at high rpm. I had hoped that my application (low g, high rpm) of
the engine would avoid this situation. I have been able to run 14 events on this engine,
the last 9 with the supercharger, and the last 5 at 160 mph average. So I don't know if
it's an accumulated stress/wear situation, or a momentary lack of oil to the bearings. I
will be cross drilling the next crank. Dave is making arrangements at this moment.
The 2/6 bearing failure is a know weakness in the 928 engine. People have attempted
to overcome this weakness by cross drilling the crank and "upgrading" the oil delivery
system (dry sump or accusump). The failures usually occur when the car is in sustained
high g left hand turns at high rpm. I had hoped that my application (low g, high rpm) of
the engine would avoid this situation. I have been able to run 14 events on this engine,
the last 9 with the supercharger, and the last 5 at 160 mph average. So I don't know if
it's an accumulated stress/wear situation, or a momentary lack of oil to the bearings. I
will be cross drilling the next crank. Dave is making arrangements at this moment.
06-19-2007 | 04:50 PM
#219
Addict
Rennlist Member
Rennlist
Site Sponsor
Rennlist Member
Rennlist
Site Sponsor
Joined: Jul 2001
Posts: 11,542
Likes: 3
From: Anaheim California
Mark you still believe that your Holbert/Porsche hand built engine has a stock bottom end ??? Also , The stock oil pump moves about 65 Liters per minute at 5,250 RPM so it is not the pump.
06-19-2007 | 05:06 PM
#220
Rennlist Member
Joined: Mar 2002
Posts: 1,617
Likes: 1
From: California
we spent on average over 2 minutes at peak hp..or over 200 mph, at a time. RPMs between 5800-6000.
One on run, Susan had a head wind and ran for 3-5 minutes at a time at 5800...but we had a drilled crank.
Marc
One on run, Susan had a head wind and ran for 3-5 minutes at a time at 5800...but we had a drilled crank.
Marc
06-19-2007 | 05:18 PM
#221
Rennlist Member
Joined: Feb 2003
Posts: 29,817
Likes: 185
From: saratoga, ca
I do 
no accusump, probably not a drilled crank either, but we will see when it comes time to see. 90 hours of racing so far, and over 5.5 full racing seasons. It could be a testimonial to Amzoil. The engine could be something unusual too. Things were hand built on the engine, but things like the cams were stock-like, as proved by the identical performance with the 85 cams after install to fix the toothless custom cams.
so if oil quantiy is not a factor, then it must be related to the sustained rpms and centrigual force of the crank not alowing the oil to feet the bearings, but i thought the oil went from inside the crank out, so it would seem that high rpms would help feed the bearings. maybe in road racing conditions, the short 6000 to 6500rpm engine speeds that starve the bearings get fed again when rpms drop for a shift to 4500rpm. This type of engine use might be fostering lubrication enough to keep things well lubricated.
mk
no accusump, probably not a drilled crank either, but we will see when it comes time to see. 90 hours of racing so far, and over 5.5 full racing seasons. It could be a testimonial to Amzoil. The engine could be something unusual too. Things were hand built on the engine, but things like the cams were stock-like, as proved by the identical performance with the 85 cams after install to fix the toothless custom cams.so if oil quantiy is not a factor, then it must be related to the sustained rpms and centrigual force of the crank not alowing the oil to feet the bearings, but i thought the oil went from inside the crank out, so it would seem that high rpms would help feed the bearings. maybe in road racing conditions, the short 6000 to 6500rpm engine speeds that starve the bearings get fed again when rpms drop for a shift to 4500rpm. This type of engine use might be fostering lubrication enough to keep things well lubricated.
mk
Originally Posted by Jim bailey - 928 International
Mark you still believe that your Holbert/Porsche hand built engine has a stock bottom end ??? Also , The stock oil pump moves about 65 Liters per minute at 5,250 RPM so it is not the pump.
06-19-2007 | 05:24 PM
#222
Rennlist Member
Joined: Mar 2002
Posts: 1,617
Likes: 1
From: California
IDEA....
Mark, is your Rennlist sponsored engine ready to go?
If so, maybe George can "use" it for a few of his events ... a stroker supercharger will do really well with just a few pounds of boost...say 7 or so? both are rennlist sponsored and built by MOTORSPORTS...right??
Thoughts!!
Mark, is your Rennlist sponsored engine ready to go?
If so, maybe George can "use" it for a few of his events ... a stroker supercharger will do really well with just a few pounds of boost...say 7 or so? both are rennlist sponsored and built by MOTORSPORTS...right??
Thoughts!!
06-19-2007 | 05:38 PM
#224
Addict
Rennlist Member
Rennlist Member
Joined: Apr 2002
Posts: 2,197
Likes: 54
From: SF Bay Area
One of the things we found when we opened the hood was that the dip stick was sticking up
about 6 inches and that the oil had blown out of the dipstick tube all over the front of the engine.
I was assuming this occurred after the engine blew because of excess pressure in the crank case.
If it had occurred first, the engine would have spit out a few quarts of oil, lost pressure while
still spinning 6000 rpm, then dropped oil pressure when the pick up couldn't find any oil. This
would have taken about 6-8 seconds (from memory and the video). Would the loss of oil for this
period be enough to destroy the bearings? Again, I don't know for sure what the sequence of
events were, so this is just more speculation as to the cause.
about 6 inches and that the oil had blown out of the dipstick tube all over the front of the engine.
I was assuming this occurred after the engine blew because of excess pressure in the crank case.
If it had occurred first, the engine would have spit out a few quarts of oil, lost pressure while
still spinning 6000 rpm, then dropped oil pressure when the pick up couldn't find any oil. This
would have taken about 6-8 seconds (from memory and the video). Would the loss of oil for this
period be enough to destroy the bearings? Again, I don't know for sure what the sequence of
events were, so this is just more speculation as to the cause.
06-19-2007 | 05:41 PM
#225
Addict
Rennlist Member
Rennlist Member
Joined: Apr 2002
Posts: 2,197
Likes: 54
From: SF Bay Area
Originally Posted by Jim bailey - 928 International
It is NOT CROSS DRILLING !!! it is drill it like a Chevy and feed 2/6 from the other main bearing. Stock 928s are cross drilled.
but yes, the new crank will be "drilled like a Chevy".