Crank scrapers, pan spacers, Accusumps ?
06-21-2010, 11:20 AM
#31
Racer
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Here's my understanding of what's going on:
For piston-guided rod setups, like in many of the modern imports or serious race engines, the rod is located by the piston-to-rod small end clearance. In those case the rods can't stack or bunch right next to each other.
For crankshaft-guided rod setups, it's my understanding that the oil pressure from the rod bearings will center the rods on the crankshaft journal. Suppose that the rods were about to "stack" in one end of the crank pin. Now, the oil temporarily can't escape freely and the oil pressure will push the rods away from each other and the crank fillet until it can. The oil pressure centers the rods.
For a piston-guided engines, one can slot any number of squirter slots to the rods. For crankshaft-guided engines, the slots reduce the effectiveness of one of the centering mechanisms.
When sending out random piston slotted rod pictures, it would be useful to note with each of them whether they are from a piston-guided or crankshaft-guided engine.
For piston-guided rod setups, like in many of the modern imports or serious race engines, the rod is located by the piston-to-rod small end clearance. In those case the rods can't stack or bunch right next to each other.
For crankshaft-guided rod setups, it's my understanding that the oil pressure from the rod bearings will center the rods on the crankshaft journal. Suppose that the rods were about to "stack" in one end of the crank pin. Now, the oil temporarily can't escape freely and the oil pressure will push the rods away from each other and the crank fillet until it can. The oil pressure centers the rods.
For a piston-guided engines, one can slot any number of squirter slots to the rods. For crankshaft-guided engines, the slots reduce the effectiveness of one of the centering mechanisms.
When sending out random piston slotted rod pictures, it would be useful to note with each of them whether they are from a piston-guided or crankshaft-guided engine.
The presence of these wear marks on a used part answers whether contact is made. If you look carefully at the Honda rod picture you can see them there as well.
06-21-2010, 11:24 AM
#32
Rennlist Member
On the dry sump issue, I would just like to say that the design is critical and I have been working on that recently, I can understand why some systems don't work. I think also we should start to divide the dry sumps into two. Ones that work on the dry sump principle and the other type that also pulls a vacuum with a proper engine breather system.
Greg
Greg
MK - I regularly run my engine for 40mins + races at 4bar max when hot with Castrol Edge 10W60 for M-engines and my bearings look as good as new... I don't think you really need higher than 3 bar to run our engines. Btw, I do have oil restricting valves in the heads...
06-21-2010, 11:27 AM
#33
Nordschleife Master
It is probably more useful in this situation for me to reach over and pick up the 928 rod and piston assembly sitting next to my desk and look at the polished wear marks on each of the rod side faces. This means that it is virtually certain that every sort of stacking situation arises in the stock motor. These wear marks were present on all the other rods as well.
Do you think grinding a lot oil squirter slots to the rod big end is going to help or hurt the rod "stacking" problem in a crankshaft-guided rod setup?
06-21-2010, 11:28 AM
#34
Nordschleife Master
Out of curiosity, what crankshaft do you have and what rpm are you running?
06-21-2010, 12:09 PM
#35
Rennlist Member
The GT engine started to smoke because of worn crap non-OEM rings, when pulled, the 2/6 and 4/8 were pristine. As if they have never worked - they had done 00000s of hard miles on the track
06-21-2010, 12:13 PM
#36
Rennlist Member
yep, just finished another race weekend. no oil pressure problems, chalk up 2 fulll race seasons on this motor now! no mods at all. RPM in the 6500rpm range for shifts, but after looking at the HP curves again, I might back it down to 6200 to 6300rpm from now on for max performance.
06-21-2010, 12:17 PM
#37
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I think the rod stacking problem happens regardless. I think the bearing shell temperature and the underside of the piston temperature is a lot more important than the side face of the rod in a racing engine.
06-21-2010, 01:12 PM
#38
Nordschleife Master
So it was oil control issue and resulting ring flutter then. Sounds like a pleasant surprise, all things considered.
06-21-2010, 01:24 PM
#39
Nordschleife Master
Piston-guided rod design allows one to make the rod big end slightly narrower and thus lighter with a given crank and bore spacing. This will indirectly allow for narrower bearings, but that's pretty minor. With a clean-sheet engine design, pretty much the only benefit is reduced friction.
06-21-2010, 01:29 PM
#40
Rennlist Member
https://rennlist.com/forums/928-foru...ml#post7550686
Last edited by Cheburator; 06-21-2010 at 01:39 PM. Reason: add link to another post
06-21-2010, 10:30 PM
#42
Race Director
interesting thread...with lots of great technical data... however when you look at the facts regarding track-race driven 928's there are certain trends that indicate the need for a better oiling system.... This is highly debatable & its carried on at great lengths on here....
Here is my 2 cents...& I would say they are probably worth less than that!
If you look at long living 928 race engines (other than Kibort) the longest lasting ones are strokers with cross drilled cranks, dry sump or accusump...these are proven and last a long time...Doc Brown has built many of these and there are plenty around that still last years on track ( I would estimate the rebuild time around 100+ hours on track, quite good for race engines) However these engines are essentially "sprint" engines...that run in 20 minute or so stints... NOT endurance racers...which is a whole different type of event. Since they are strokers they do turn slightly less RPM....I would say 6500 max, but the owners can give their experience
In my "endurance" racer (the Lemons Estate) I ran it two ways:
Bone stock 4.7L USA with plenty of leaks and 150k+ mileage..it blew up in 16 hours...yes it ran amsoil for about 1/2 that time, until it leaked out and was replaced with walmart special 20-50...it would come in after 2 hours on track and be 3 quarts down (thats a hint there is a problem)....just for reference all breather was rerouted and not injected back to the intake...it was open to atmosphere through a K&N filter at the filler
Version 2.0: Same engine with a quoted 117k miles (who knows really) that did have better compression #'s than the last engine, rod bearings looked great (didn't check old ones) with a 3/8th pan spacer kit and the "OB" oil pan.....this engine currently has 30 HOURS on track....it burns very little oil (same breather setup as before) its oil analysis comes back perfect, even with 18 hour oil change intervals & it burns around a qt every 4 hours or so...... as a precaution it is NOT rev'd past 6000.... On R comps it can pull 1.5g in corners and brake at well past 1g.....
I built this car to run 8+ hours per day non stop.....yes in theory it is $500 crap can....but it flat runs around the track....I am confident it could finish the 25 hour with minimal prep work....
I'll be at Thunderhill this Friday chasing down "real" racers!!!!
With that said.....will my next race 928 have a 928 engine.....NO WAY.......its just not worth the weight-expense vs the HP you get......the next one I build will have an LS engine....why you ask.....COST.. A LS engine that is 100+lbs lighter than a 928 engine can make the same HP for less than 1/2 the cost....
Here is my 2 cents...& I would say they are probably worth less than that!
If you look at long living 928 race engines (other than Kibort) the longest lasting ones are strokers with cross drilled cranks, dry sump or accusump...these are proven and last a long time...Doc Brown has built many of these and there are plenty around that still last years on track ( I would estimate the rebuild time around 100+ hours on track, quite good for race engines) However these engines are essentially "sprint" engines...that run in 20 minute or so stints... NOT endurance racers...which is a whole different type of event. Since they are strokers they do turn slightly less RPM....I would say 6500 max, but the owners can give their experience
In my "endurance" racer (the Lemons Estate) I ran it two ways:
Bone stock 4.7L USA with plenty of leaks and 150k+ mileage..it blew up in 16 hours...yes it ran amsoil for about 1/2 that time, until it leaked out and was replaced with walmart special 20-50...it would come in after 2 hours on track and be 3 quarts down (thats a hint there is a problem)....just for reference all breather was rerouted and not injected back to the intake...it was open to atmosphere through a K&N filter at the filler
Version 2.0: Same engine with a quoted 117k miles (who knows really) that did have better compression #'s than the last engine, rod bearings looked great (didn't check old ones) with a 3/8th pan spacer kit and the "OB" oil pan.....this engine currently has 30 HOURS on track....it burns very little oil (same breather setup as before) its oil analysis comes back perfect, even with 18 hour oil change intervals & it burns around a qt every 4 hours or so...... as a precaution it is NOT rev'd past 6000.... On R comps it can pull 1.5g in corners and brake at well past 1g.....
I built this car to run 8+ hours per day non stop.....yes in theory it is $500 crap can....but it flat runs around the track....I am confident it could finish the 25 hour with minimal prep work....
I'll be at Thunderhill this Friday chasing down "real" racers!!!!
With that said.....will my next race 928 have a 928 engine.....NO WAY.......its just not worth the weight-expense vs the HP you get......the next one I build will have an LS engine....why you ask.....COST.. A LS engine that is 100+lbs lighter than a 928 engine can make the same HP for less than 1/2 the cost....
06-22-2010, 01:29 PM
#43
Rennlist Member
You cant exclude my data, because it includes over 5 engines that I have been responsible for,and they are still running today, or ran for a good long time on the track. 
Remember, Im runnning near 10 seconds faster a lap with 305s on all four corners at a ride hight of 110mm, so the g loading is greater and so are all the accelerations. remember, i could run my 928 without even any brakes, faster than the estate runs now. (or in one boggey gear). The point is, for most applications, the 928 engine is hardly working, as long as you are in the right gear, have enough oil and the oil isnt something that will water down at race temps.
I do believe that there is a real issue at 7000rpm, but anderson has not seen a problem with his drilled crank set up, similar to mine and Joe fans, who also havent seen any failures. So, if one was to look at the HP curve of their engines, is there even a requirement or need to run over 6400rpm? in most all cases, no. Now, if you pump up a 5 liter like dennis, then you do, and then you start using the engine not how it was designed to be used and you could have a grenade. So, instead of spending all the money on valves, port work, special cams and tuning, why not just build a stroker with minimal mods, like mine. its kind of like restrictor racing, but it makes sense. you dont blow up transmissions and clutches, you have plenty of power (360rwhp on tap at any post shift rpm which compares very well to the pumped up, more common 420rwhp of the higher strung engines) and you get reliability of a stock engine because you are hardly using the engine hard. right now, my shifts technically can be at 6000rpm and with very little gain shifting over. In fact, ive been banging off the rev limiter for 3 years now, and really didnt need to be. engine is in great shape, still has the same power, no wear patterns based on oil analysis, etc. (also no coolers, spacers, accusumps, or any mods at all, just amsoil)
so, I think the stock set up is just fine for how we all use the 928. even Joe and Mark A. have proved this as well. drill the crank if you can, if not, use the stock stuff and use the right gears around the race track. warm up your engines well before beating on them and use a good oil, that does not have a the letter M or a 1 in the name.
Remember, Im runnning near 10 seconds faster a lap with 305s on all four corners at a ride hight of 110mm, so the g loading is greater and so are all the accelerations. remember, i could run my 928 without even any brakes, faster than the estate runs now. (or in one boggey gear). The point is, for most applications, the 928 engine is hardly working, as long as you are in the right gear, have enough oil and the oil isnt something that will water down at race temps.
I do believe that there is a real issue at 7000rpm, but anderson has not seen a problem with his drilled crank set up, similar to mine and Joe fans, who also havent seen any failures. So, if one was to look at the HP curve of their engines, is there even a requirement or need to run over 6400rpm? in most all cases, no. Now, if you pump up a 5 liter like dennis, then you do, and then you start using the engine not how it was designed to be used and you could have a grenade. So, instead of spending all the money on valves, port work, special cams and tuning, why not just build a stroker with minimal mods, like mine. its kind of like restrictor racing, but it makes sense. you dont blow up transmissions and clutches, you have plenty of power (360rwhp on tap at any post shift rpm which compares very well to the pumped up, more common 420rwhp of the higher strung engines) and you get reliability of a stock engine because you are hardly using the engine hard. right now, my shifts technically can be at 6000rpm and with very little gain shifting over. In fact, ive been banging off the rev limiter for 3 years now, and really didnt need to be. engine is in great shape, still has the same power, no wear patterns based on oil analysis, etc. (also no coolers, spacers, accusumps, or any mods at all, just amsoil)
so, I think the stock set up is just fine for how we all use the 928. even Joe and Mark A. have proved this as well. drill the crank if you can, if not, use the stock stuff and use the right gears around the race track. warm up your engines well before beating on them and use a good oil, that does not have a the letter M or a 1 in the name.
06-22-2010, 05:33 PM
#44
Race Director
MK
I am not discounting the success you have had with your engines (including Scotts)....
BUT you are the ONLY one in the world that can drive a stock S4 oiling system and not blow the engine in around 10 hours on track..... Many of us have tried and have blown engines to show for it...I personally have blown 3, but I would say 2 were due to the oiling problems.... I can go on and on about guys who track 928's on the exact same tracks we drive at the similar lap times that have grenaded multiple engines..... The list is long and scary....
GTS's blow on the autobahn at high rpm high G (kinda anyway) corners.... track 928's all over the world blow quickly with stock oiling.....the only ones (except yours) that survive have significant mods to the oiling system.
I would say the least expensive mod that seems to work is the spacer + OB pan I run on the lemons racer.....I wouldn't say its perfect, but seems to work fine in the sub 6000rpm range I run...
I am not discounting the success you have had with your engines (including Scotts)....
BUT you are the ONLY one in the world that can drive a stock S4 oiling system and not blow the engine in around 10 hours on track..... Many of us have tried and have blown engines to show for it...I personally have blown 3, but I would say 2 were due to the oiling problems.... I can go on and on about guys who track 928's on the exact same tracks we drive at the similar lap times that have grenaded multiple engines..... The list is long and scary....
GTS's blow on the autobahn at high rpm high G (kinda anyway) corners.... track 928's all over the world blow quickly with stock oiling.....the only ones (except yours) that survive have significant mods to the oiling system.
I would say the least expensive mod that seems to work is the spacer + OB pan I run on the lemons racer.....I wouldn't say its perfect, but seems to work fine in the sub 6000rpm range I run...
