early dyno results
02-17-2011, 02:36 AM
#271
Rennlist Member
Again, please tolerate my ignorance.
But, the engine by itself is not a pump. It requires input of external energy to become a pump.
That energy is typically burned fuel.
Turn that engine at 6000 RPM with an external power source and you will see something completely different.
If the engine is simply “turning”, there should be no build up of pressure in the crank case.
Every piston on the down stroke has another on the up stroke. Therefore, there should be no change in air volume within the crank case. Yes, there will be air movement, as different cylinders are “pushing air down” verses “pulling air up”. But, the end result should be “no displacement of air”.
And, yes, the oil pump enters into this since it is pumping and “changing the volume of the crank case”.
How much does the oil pump enter into this equation? Who knows? Is there too much oil pumped to the heads? Who knows?
Add in blow by, and, any other “chemically and/or heat caused” pressure increases, and now there may be a pressure differential problem.
Can someone spin an engine at 6000 RPM by external means? That really shouldn’t hurt anything since the oil pump will still be turning (other than “fuel lubricated items” and “opposite torque issues”).
If so, that would provide very valuable information on the direction required to solve this problem.
What if you used that positive crank case pressure to power a venturi effect oil return system?
But, the engine by itself is not a pump. It requires input of external energy to become a pump.
That energy is typically burned fuel.
Turn that engine at 6000 RPM with an external power source and you will see something completely different.
If the engine is simply “turning”, there should be no build up of pressure in the crank case.
Every piston on the down stroke has another on the up stroke. Therefore, there should be no change in air volume within the crank case. Yes, there will be air movement, as different cylinders are “pushing air down” verses “pulling air up”. But, the end result should be “no displacement of air”.
And, yes, the oil pump enters into this since it is pumping and “changing the volume of the crank case”.
How much does the oil pump enter into this equation? Who knows? Is there too much oil pumped to the heads? Who knows?
Add in blow by, and, any other “chemically and/or heat caused” pressure increases, and now there may be a pressure differential problem.
Can someone spin an engine at 6000 RPM by external means? That really shouldn’t hurt anything since the oil pump will still be turning (other than “fuel lubricated items” and “opposite torque issues”).
If so, that would provide very valuable information on the direction required to solve this problem.
What if you used that positive crank case pressure to power a venturi effect oil return system?
Last edited by depami; 02-17-2011 at 04:01 AM.
02-17-2011, 05:45 AM
#272
Rennlist Member
Thanks for the clarification!
I have a few german publications about the max moritz 928 racer and a few other.Maybe I scan the pages and mail it to you.
The other interresting point is a lot of GT engines grenade on fast autobahn trips.
My shop has every year one or two to fix with 2/6 main bearing.
His meaning was low oil level in engine and than Vmax for 10-15 min on the autobahn.
But after Gregs description of the problem we have here more than one problem.
Here in north germany you can drive at the right time on a few autobahn tracks very fast with long curves at high speed.
My 86.5 needs one litre and more oil after 100 km high speed.Driving fast on second grade streets around my town and you have the typical 1-2 litre oil per 1000 km.
A friend of me has a 928 s track car and the only modifications to the oiling system are a modified oilchannel to bearing 2/6 and very huge engineoilcooler and airinlets in the body.
The engine has ~300 rwhp.
This car is every weekend in the summer on the track and this for 4-5 years.Maybe this extreme oiling problem is a 32 v related problem?
Over the weekend I check my magazines for articles about 928 racers.After a quick read in one article they say the 928 gts racer use 968 oil valves with in the heads because the stock engines grenade in fast corners on the track.
The oil was in the heads and the oil pan was empty.
I have a few german publications about the max moritz 928 racer and a few other.Maybe I scan the pages and mail it to you.
The other interresting point is a lot of GT engines grenade on fast autobahn trips.
My shop has every year one or two to fix with 2/6 main bearing.
His meaning was low oil level in engine and than Vmax for 10-15 min on the autobahn.
But after Gregs description of the problem we have here more than one problem.
Here in north germany you can drive at the right time on a few autobahn tracks very fast with long curves at high speed.
My 86.5 needs one litre and more oil after 100 km high speed.Driving fast on second grade streets around my town and you have the typical 1-2 litre oil per 1000 km.
A friend of me has a 928 s track car and the only modifications to the oiling system are a modified oilchannel to bearing 2/6 and very huge engineoilcooler and airinlets in the body.
The engine has ~300 rwhp.
This car is every weekend in the summer on the track and this for 4-5 years.Maybe this extreme oiling problem is a 32 v related problem?
Over the weekend I check my magazines for articles about 928 racers.After a quick read in one article they say the 928 gts racer use 968 oil valves with in the heads because the stock engines grenade in fast corners on the track.
The oil was in the heads and the oil pan was empty.
02-17-2011, 06:12 AM
#273
Addict
Rennlist Member
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02-17-2011, 08:44 AM
#274
Rennlist Member
Here is my 2c - perhaps a bit of a backdrop and a few observations with regards to my race GT/GTS engines can help?
1st iteration - dry sumped blue-printed GT engine with standard GT breathing system. Zero oil ejection in the intake, until we mapped it to buggery and it destroyed 2 oil rings in the process. Oil tank and catch can in the boot. No oil in the catch tank
2nd iteration - dry sumped, blue-printed high compression GTS engine with alusil liners, 968 valves and massaged GT cams. The oil filler plate was blanked off, the four breather holes on the cam covers blanked off, all crank case/heads venting done via the oil tank at the back. Worked fine on UK circuits which are twisty and relatively slow. The minute the engine was tested at the Nurburgring, where the car would see 150mph + it started blowing out the oil dipstick. No oil in the intake - obviously, no smoke at WOT, no oil in the catch tank, but the oil smelled of fuel pretty strongly
3d iteration - same engine, but LHS cam cover breathers opened up, merged into a common hose via a T, which was then plugged into a catch tank sitting in front of the radiator. The oil ejection stopped, but the engine failed. It is worth pointing out that it happened at the only track in the UK except Silverstone where 140mhp+ is achievable. The track configuration was such that a shicane before the pit straight makes you go 2nd to 5th, then a 4th gear corner taken with a lift, then a 2nd gear corner and back on to another straight, which makes you go through the gears again... Not enough oil in the tank to start with (my bad) plus sustained high rpm in a heavy breathing motor...
The dry sump pump is a two-stage "pace products" - spinning 1:1 with the engine and sized to have 2 x the capacity of the pressure pump (engine's original oil pump). Used to run 12ltrs of oil, now will go up to 15ltrs...
Btw, the C6 Z06 guys were suffering from 1/5 and 2/6 simultaneous failures - turns out the 10ltrs of oil in the system was not quite enough for the LS7 either...
1st iteration - dry sumped blue-printed GT engine with standard GT breathing system. Zero oil ejection in the intake, until we mapped it to buggery and it destroyed 2 oil rings in the process. Oil tank and catch can in the boot. No oil in the catch tank
2nd iteration - dry sumped, blue-printed high compression GTS engine with alusil liners, 968 valves and massaged GT cams. The oil filler plate was blanked off, the four breather holes on the cam covers blanked off, all crank case/heads venting done via the oil tank at the back. Worked fine on UK circuits which are twisty and relatively slow. The minute the engine was tested at the Nurburgring, where the car would see 150mph + it started blowing out the oil dipstick. No oil in the intake - obviously, no smoke at WOT, no oil in the catch tank, but the oil smelled of fuel pretty strongly
3d iteration - same engine, but LHS cam cover breathers opened up, merged into a common hose via a T, which was then plugged into a catch tank sitting in front of the radiator. The oil ejection stopped, but the engine failed. It is worth pointing out that it happened at the only track in the UK except Silverstone where 140mhp+ is achievable. The track configuration was such that a shicane before the pit straight makes you go 2nd to 5th, then a 4th gear corner taken with a lift, then a 2nd gear corner and back on to another straight, which makes you go through the gears again... Not enough oil in the tank to start with (my bad) plus sustained high rpm in a heavy breathing motor...
The dry sump pump is a two-stage "pace products" - spinning 1:1 with the engine and sized to have 2 x the capacity of the pressure pump (engine's original oil pump). Used to run 12ltrs of oil, now will go up to 15ltrs...
Btw, the C6 Z06 guys were suffering from 1/5 and 2/6 simultaneous failures - turns out the 10ltrs of oil in the system was not quite enough for the LS7 either...
02-17-2011, 09:26 AM
#275
Nordschleife Master
response in Blue
I keep hearing you, about running the 944 pressure reduction valves, in the heads. I've used these before, in some engines.
You have any idea why they would not have run these in the GTS engines, from the factory, since they had to have them available and were obviously fighting with the oil control issues? Pretty obviously, they gave up on venting the crankcase through the oil filler neck and decided to vent the crankcase through the valve covers, in the '94/'95 models. They have to had run these engines on dynos and had to know that the heads filled up with oil...so you'd think they would have done this, if at all possible.
Well, if we look at the history on the GTS engine, and its high rate of oil consumption that some believe is reduced/eliminated by drilling out a few holes in the pistons. I think that we can safely say that they really stopped caring about eliminating the problems as they had already decided to discontinue the production of the car. So it is possible that they just left it as was. Why they chose to make and use the 944S2 valve and then not use it in the 968, or 928 is possibly the reason that Erkka pointed out. Maybe these motors require more oil pressure for the chain tensioners...
That said on the 928 motor I have not heard of the chain tensioners coming apart and grenading the motor. I have not heard of this on a 968 either. But I have heard of it on a 944S2. But they should be changed and inspected every now and then, and that should prevent their problem. Is it also possible that the higher pressure to the tensioner could be desired to maintain more chain tension, and therefor a more accurate timing on the intake camshafts?
This could also explain the failures on the S2 tensioner. If the chain is allowed to whip at any time, it could lead to failure.
Why would they run them in the 944S2 and then go away from them in the 968 engines? Seems pretty much like the same stuff....
I think it is pretty easy to say that no one can actually know what was running through their head at the time. Which is one of the reasons I am not afraid to change, or stray from factory. Technology has come a very long way since then, and if you have the ability why not!
My lifters are all DLC coated, and my cam profiles are very modern and thus require very light spring pressures, so I might be able to cut down on the oil supply and perhaps not have any issues...I just don't like that "perhaps" word, on my customer's engines.
Well, I will be home in the first week of march, and will be installing high lift/duration cams, springs, etc. It would not be hard for me to install 2 of the S2 valves into my heads (manual) at the same time and do a trial run. I will PM you on this.
You have any idea why they would not have run these in the GTS engines, from the factory, since they had to have them available and were obviously fighting with the oil control issues? Pretty obviously, they gave up on venting the crankcase through the oil filler neck and decided to vent the crankcase through the valve covers, in the '94/'95 models. They have to had run these engines on dynos and had to know that the heads filled up with oil...so you'd think they would have done this, if at all possible.
Well, if we look at the history on the GTS engine, and its high rate of oil consumption that some believe is reduced/eliminated by drilling out a few holes in the pistons. I think that we can safely say that they really stopped caring about eliminating the problems as they had already decided to discontinue the production of the car. So it is possible that they just left it as was. Why they chose to make and use the 944S2 valve and then not use it in the 968, or 928 is possibly the reason that Erkka pointed out. Maybe these motors require more oil pressure for the chain tensioners...
That said on the 928 motor I have not heard of the chain tensioners coming apart and grenading the motor. I have not heard of this on a 968 either. But I have heard of it on a 944S2. But they should be changed and inspected every now and then, and that should prevent their problem. Is it also possible that the higher pressure to the tensioner could be desired to maintain more chain tension, and therefor a more accurate timing on the intake camshafts?
This could also explain the failures on the S2 tensioner. If the chain is allowed to whip at any time, it could lead to failure.
Why would they run them in the 944S2 and then go away from them in the 968 engines? Seems pretty much like the same stuff....
I think it is pretty easy to say that no one can actually know what was running through their head at the time. Which is one of the reasons I am not afraid to change, or stray from factory. Technology has come a very long way since then, and if you have the ability why not!
My lifters are all DLC coated, and my cam profiles are very modern and thus require very light spring pressures, so I might be able to cut down on the oil supply and perhaps not have any issues...I just don't like that "perhaps" word, on my customer's engines.
Well, I will be home in the first week of march, and will be installing high lift/duration cams, springs, etc. It would not be hard for me to install 2 of the S2 valves into my heads (manual) at the same time and do a trial run. I will PM you on this.
02-17-2011, 11:47 AM
#277
Addict
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Installation is easy as long as stock ball cup agrees to come out from head. One way to remove it I have found works is to make threads to center hole with correct diameter long thread tool. Then its fairly easy to pull cup out with long bolt. Head dimensions are correct for installing valve once stock parts are removed.
02-17-2011, 12:07 PM
#278
Not the sharpest tool in the shed
Rennlist Member
Rennlist Member
If you run the 944 S2 oil check valves is it possible you introduce their cam chain tensioner failure issues as well because the oil drains back to the sump faster. Seems like you might be trading one failure scenario for another.
02-17-2011, 12:16 PM
#279
Three Wheelin'
Well it could be possible that the reason the 928 chain tensioner pads last a long time is because of the head getting flooded with oil, like shown on the video and what Greg experienced on the engine dyno. So trying to solve the problem of eliminating that much oil going up there and staying there could very well reduce the life of the chain tensioner system.
02-17-2011, 12:17 PM
#280
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Maybe but its lesser of two evils, by far. Something like $700 every 8-10 years or 40-50k miles vs total engine rebuild after few fast laps on track. If it really helps a lot.
02-17-2011, 12:56 PM
#281
The Parts Whisperer
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For those looking for a proven solution you can simply buy my race car. You'll get a 2600 lb 928 with 500 RWHP . The Greg Brown built engine is dry sumped with hundreds of proven track miles and a GTS transmission with the PSD removed and a standard diff installed complete with the factory oil pump.
http://www.928intl.com/race/index.htm
http://www.928intl.com/race/index.htm
02-17-2011, 02:09 PM
#284
Drifting
02-17-2011, 02:15 PM
#285
Archive Gatekeeper
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The numbers sound good but we need to work on the missing zeros