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That is correct, Porsche 944S 87-88 only 2.5 liter 16V - "Cams are free".
Answering your 1st question, yes, that would be legal, cannot even see how it could be deemed even controversial as it uses a stock pan as a base.
This is similar (I said opened to more creative baffling) to what I was trying to explain in the post above, except even the pickup tube, suction channel in the block/girdle could be deleted if the suction side of the front oil pump was tapped externally and a hard line was run alongside the pan to a simple fitting that lead to in-pan baffling.
Your solution looks great though, especially since it removes the factory suction foot that is probably the source of vibration cracks in the tube.
Now, if you don't mind, I have a question, no hurry in response.
The configuration as per stock for the main bearings, which ultimately feed the rods, uses a grooved upper bearing in the crankcase and a "plain" lower bearing in the girdle.
With exception to the #3 main which doubles as thrust, all of the main journals have two holes at less than 180 degrees apart. It seems to me that,
1) since each bearing half covers 180 degrees and one is "plain", there is a measurable time interval when there is no feed at all.
2) since the feed to the rods is traded between the two opposing feed holes as they pass from grooved to plain bearing, there is an oscillation happening at the intersection where the two feed holes meet in the main bearing's center.
I understand that at the speed the crankshaft is spinning and oil under pressure, that the supply to rods may never be interrupted even though the spacing of the holes leaves a +180 degree interval but what about the knifing effect of the oil supply oscillation by the plain bearing....?
Shouldn't we be running grooved bearings on both the crankcase upper and the lower (girdle) which would give simultaneous full time feed and remove the back and forth feed oscillation ....?
T
It is common for engines to have gutter style main bearing shells on one half of the journal, always on the upper side if that is where the oil supply is coming from. However, I have not really studied this part of the 944 engine in depth.
The idea is to have a greater volume of oil available always. A “pressurized tank” right at the journal.
I will take a more detailed look at this in the coming days. This does bring up the need to understand why the surface finish on the crank journals is so important. The clearances the oil is pushed through are so small any tiny imperfection affects the amount of oil and its movement around the bearing surface. The trade off is less bearing surface to support the all-important oil film.
There are many mods done to these engines that are not in the best interest of reliability and performance. Without sounding condescending and elitist, some are just plain wrong. In situations where the overall costs are significantly lower, you always find more “shade tree” engineering. Much of it based on, “if it doesn’t break its ok”.
One of the biggest no no’s in these engines is the removing of the balance shafts along with “knife edging" the crankshaft counterweights. They are there for a reason and an important one. You may gain as slight increase in engine acceleration not having to turn the shafts, and less weight rotating, but the engine will suffer increasingly from its secondary imbalance and this imbalance will increase at the square of engine speed.
Cam timing goes all over the place made even worse as the cam(s) are driven via a flexible rubber belt. I can assure you, you will lose less performance when running the shafts and a non-knife edged crankshaft. The slim faced counterweights are done as this is thought to help the counterweights pass through the oil with less resistance. This would be true if the oil was in the pan but at speed all the oil is stacked up on the side of the block and pan. The crankshaft rotates in an oily mist typically.
I can understand why doing lightening work to these crankshafts is done, they weight as much as a house and not a race worthy part. But make sure you fully understand the reasons for why and if any mods are done, what are the consequences.
The work we are about to start on modifying the stock crankshafts for a couple of customers will allow us to show how we do this modification. It will give me the reason to consider the oiling in more detail and see if there are further mods that could help.
I will try to put more info and photos relevant to the 4 cylinder engine up on our web site. This will keep this forum clear of further long winded explanations.
One of the biggest no no’s in these engines is the removing of the balance shafts along with “knife edging" the crankshaft counterweights. They are there for a reason and an important one. You may gain as slight increase in engine acceleration not having to turn the shafts, and less weight rotating, but the engine will suffer increasingly from its secondary imbalance and this imbalance will increase at the square of engine speed.
question on this...
common wisdom over the years has been "leave the B-shafts alone otherwise you risk cracking the oil pickup tube".
with a trick oil pan fitted like the one you posted previously, with what looks to be a totally new oil pickup, what is the next risk of B-shaft deletion?
I will try to put more info and photos relevant to the 4 cylinder engine up on our web site. This will keep this forum clear of further long winded explanations.
Don't sweat it, this is all about long winded posts and explanations.
In the transmission world, which is a leap so far forward in oil control when compared to engines, that engines bore me. Until I started racing myself, then further onto building race cars/engines for my son.
On your point of retention of oil on the bearing surface, when there's an issue proven out by warranty claim failures, manufacturers don't want to pay unlimited claims so they revise. You may have a part, that depending on Julian date, may have 1st, 2nd and even 3rd designs in one single calendar year.
Here's an on topic example,
The original plain bushing's width was decreased to make room for wider pump gears (another on topic issue) and as a result, the surface reduction was not able to support a film width that could support rmps of the torque converter hub.
The bearing seized to the hub and spun in the casting, covered the drainback hole and pushed the front seal out. The revision added dimples which retained more usable oil and is till used today in that application.
I have seen countless revisions by major manufacturers that actually made problems worse.
The 944/968 engine lived long enough to have revision of it's own, oil pans, pressure regulator, etc., etc.
It'd be interesting if the factory had kept up development as to where it'd be given 10 more years of life but we can see where they were going to know what some of the problems were. Lower crankcase inserts that kept oil drum from climbing a high as the cylinders, windage porting the upper main bearing saddles, etc.
It's up to people with experience, knowledge and understanding to take the engine further.
When looking this over, it's very important - these engines don't really suffer rod bearing failures. They suffer #2 rod bearing failure.
question on this...
common wisdom over the years has been "leave the B-shafts alone otherwise you risk cracking the oil pickup tube".
with a trick oil pan fitted like the one you posted previously, with what looks to be a totally new oil pickup, what is the next risk of B-shaft deletion?
He mentioned one already but I think in context, it's coupled with lightening the crank as well in a search to lighten rotating mass, i.e., persons who would knife a crank would also delete the balance shafts as step b in lightening mass.
In relation to the crank.
Cam timing.
It's an end to end torsional issue with the crank driving the cam belt.
Porsche had this problem (with cams) on the flat 12s IIRC, there was so much twist front to rear, the rear cylinder's cam timing was off several degrees.
I think what better answers your question though is the harmonics Neil mentioned. Imagine that your crankshaft (the entire engine) is ringing like a bell.
This effect is very hard on bearings and can be seen in the wear pattern as chatter, not to even mention the crank itself cracking like a glass that's shattered when a singer hits a high frequency note.
Albert Broadfoot had offered a race tested balance shaft modification where he removed only one of the counterweights. He must have had some data that proved this sufficient but then again, he offered lightened, knife edged cranks....
I think it's totally safe on a street car to knife a crank, especially the turbo 1) they power through the gears on just a few pulls and the goal is to get to the full boost threshold a quick as possible. 2) they don't live at 4-7200 rpms for 1.5 hours like a race engine.
I shipped to them today, an hour south down the road from you and forgot to toss your AOS in the truck. I'll get that out to you next week.
Terry...
any of your autoboxes come with a 52mm ID, 2 piece dimpled bearing, maybe about conrod width...
LOL, nope. But if he pops back in, I think Neil will agree that the reduction in surface to accommodate the dimples would be experimental.
In surface level adhesion of intake valves (swirl etc), dimples are being experimented with also to actually keep a surface turbulence that has been proven to increase flow.
People are experimenting with dimpled porting also for the same reason, it breaks air flow's ability to adhere to the port surface...again, increasing flow for the same sized port.
My current race car build has a rock guard-like surface on the nose for this same reason. That surface turbulence is the reason a golf ball can fly straight.
It's actually more aerodynamic.
It's an end to end torsional issue with the crank driving the cam belt.
Porsche had this problem (with cams) on the flat 12s IIRC, there was so much twist front to rear, the rear cylinder's cam timing was off several degrees.
I think what better answers your question though is the harmonics Neil mentioned. Imagine that your crankshaft (the entire engine) is ringing like a bell.
This effect is very hard on bearings and can be seen in the wear pattern as chatter, not to even mention the crank itself cracking like a glass that's shattered when a singer hits a high frequency note.
Albert Broadfoot had offered a race tested balance shaft modification where he removed only one of the counterweights. He must have had some data that proved this sufficient but then again, he offered lightened, knife edged cranks....
the crank ringing/twisting wouldn't directly be affected by the presence of B-shafts or not though - that's what the 2.5S and 3.0S2 got their crank damper "harmonic balancer" for..? aside from the loading of the crank nose required to spin the B-shafts in the first place.
light B-shafts can make sense if the pistons/rods are sufficiently lighter than the stock ones (since the stock B-shafts were presumably designed around the stock piston/rod weight)...or maybe he just wants to sell people stuff for hundreds of dollars, that takes him 30 seconds on the bandsaw to make
if a new oil pan/pickup would maybe allow deletion of the B-shafts, i could repurpose the BS gear on the crank to a toothed-belt SC drive...
question on this...
common wisdom over the years has been "leave the B-shafts alone otherwise you risk cracking the oil pickup tube".
with a trick oil pan fitted like the one you posted previously, with what looks to be a totally new oil pickup, what is the next risk of B-shaft deletion?
Typically the weakest part fails first.
You can repair that part but the next in line can fail. You have to eliminate the cause not so much keep fixing the failures, going up the chain.
What you are seeing is the failure of a weak part caused by the intense and high frequency non-sinusoidal vibrations that are not being dampened or countered by the balance shafts. The balance shafts are there to counter the non-sinusoidal imbalance with a sinusoidal force.
4 cylinder in line engines have pistons that travel from TDC to BDC through 180° of crankshaft rotation. They "fire" or reach TDC compression without any other piston doing the same within 180° of crank rotation. This is commonly called an over lapping sequence. This non happening event means that the piston accelerates and travels further from TDC to 1/2 stroke than it does from 1/2 stroke to BDC.
I will cover more of this in detail on the web page.
Suffice to say, broken pick up tubes are the obvious failure as a broken part can be seen, felt and touched. What you are not seeing is the effect the crankshaft and its movement is having on your cam timing. I would hazard a guess the issue is somewhat dampened by the use of hydraulic followers in the valve train, but those using solid followers will probably be having a worse time controlling the valve train dynamics.
You do as your own risk assessment allows. There are no rules here, just solid engineering and common sense.
the crank ringing/twisting wouldn't directly be affected by the presence of B-shafts or not though - that's what the 2.5S and 3.0S2 got their crank damper "harmonic balancer" for..? aside from the loading of the crank nose required to spin the B-shafts in the first place.
light B-shafts can make sense if the pistons/rods are sufficiently lighter than the stock ones (since the stock B-shafts were presumably designed around the stock piston/rod weight)...or maybe he just wants to sell people stuff for hundreds of dollars, that takes him 30 seconds on the bandsaw to make
if a new oil pan/pickup would maybe allow deletion of the B-shafts, i could repurpose the BS gear on the crank to a toothed-belt SC drive...
I agree with what you're saying but my point was, for what they perceive as a performance advantage, people who would delete balance shafts would also knife edge a crank. Harmonic effects on a light knife edged crank is not a risk I am willing to take on a $10K NA engine even if it were legal.
I went 7 years with a HP DE engine that went to full racing for 5 years....a lot of races and laps. Replaced it with one a few steps closer to the edge.
Unrelated to choices, second race, a lean condition caused expanded piston to seize, snap a rod and lost the block too.
I built a second exact duplicate, fixed the fueling problem and have two years on the engine.
You have heard the old saying, fast/cheap/reliable, pick any two.
Well, fast is a given, I have the rare opportunity to help a driver that's at the top of the heap.
Reliable, I have to have reliability, no ifs ands or buts.
I rarely work on a car after we load it. I am at the track to enjoy it, watch my son kick everybody's a$$, trouble free.
Which leaves the last part. The price.
Again to the first point, I can do without that last risky 10% power and enjoy a 10% headroom in reliability.
My driver makes up for it....
This is where me and performance shops have a bit of a disagreement.
Their philosophy is "level of performance enhancements is proportional to how fast you want to go".
You can't buy speed based on skill that can overcome a 10-20% performance disadvantage....
But,,,,back on topic.
It's evident these guys know their stuff, if somebody is peeping in here looking for a unique proven engine after this refresh, this is the one.
Why don't you blow off the super charger fallacy and jump on it. No shipping involved, you could ride right down the road and scoop it up.
Why don't you blow off the super charger fallacy and jump on it. No shipping involved, you could ride right down the road and scoop it up.
the dollars just aren't there...in actuality, or mentally.
could never bring myself to spend 10k on "just" an engine.
probably not even 5k.
hell, i've been putting together a boost-ready 16v engine (note i didn't call it a 16v turbo ) that admittedly will be "shade tree" in concept but all the components are proven already and aside from yet-to-be-purchased wear items (head gasket set, belts and WP) i'm hovering around $1500 for everything so far.
Shouldn't we be running grooved bearings on both the crankcase upper and the lower (girdle) which would give simultaneous full time feed and remove the back and forth feed oscillation ....?
944 main bearings are actually 3/4 groove so there's some overlap which may dampen any oscillation.
I also wanted to point out that the cam sprocket on the 944 is a bit heavy, so it acts like a mini flywheel to smooth out the cam rotation. Even the ignition rotor has a counterweight and it's just 43 grams of plastic turning at half speed!
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Some good stuff here, just to make sure all get the point - balance shafts have nothing to do with crank balance or crank lightening. They are there to (somewhat) attenuate vibrations caused by an inherent in line 4 dynamic balance issue. For some the issue becomes a little more obvious when you look at the location of the pistons when the crank is half way between TDC and BDC - most would think that the pistons woudl be at the mid point in travel between top and bottom - they are not. They are all below the mid point due to the angle of the con rods. This means that the piston traveling from TDC to 90 degrees is traveling faster than the piston going from BDC to the same point, creating an imbalance. this imbalance cannot be solve with any mods to the crank, rods, pistons or any thing attached to the rotating or reciprocating mass.
The amount of force created by the balance shafts is relater to the mass of the pistons and about 1/3 the mass of the connecting rods - so if you lighten the pistons (which they desperately need!) you might think bout modding your balance shafts.
Just for entertainment - here is a graph I put together to show the effects - I have a spreadsheet to calculate the effects of moving the upper or lower belt one gear. this can be used to reduce the magnitude of the cancellation forces.
As a point of interest for those that care my co-worker gave me a technical paper that I am trying to find the digital copy....I posted a few years ago on.
One can determine the torque on an inline 4 cylinder due to the fact where you mentioned the piston speeds differing between TDC and 1/2 stroke and 1/2 stroke and BDC.
I pretty sure I did post the paper on here. Very tech paper that probably only a few people on here would even bother reading but I thought it was pretty interesting. I will try and find it on my work laptop.
Originally Posted by Performance Developments
Typically the weakest part fails first.
You can repair that part but the next in line can fail. You have to eliminate the cause not so much keep fixing the failures, going up the chain.
What you are seeing is the failure of a weak part caused by the intense and high frequency non-sinusoidal vibrations that are not being dampened or countered by the balance shafts. The balance shafts are there to counter the non-sinusoidal imbalance with a sinusoidal force.
4 cylinder in line engines have pistons that travel from TDC to BDC through 180° of crankshaft rotation. They "fire" or reach TDC compression without any other piston doing the same within 180° of crank rotation. This is commonly called an over lapping sequence. This non happening event means that the piston accelerates and travels further from TDC to 1/2 stroke than it does from 1/2 stroke to BDC.
I will cover more of this in detail on the web page.
Suffice to say, broken pick up tubes are the obvious failure as a broken part can be seen, felt and touched. What you are not seeing is the effect the crankshaft and its movement is having on your cam timing. I would hazard a guess the issue is somewhat dampened by the use of hydraulic followers in the valve train, but those using solid followers will probably be having a worse time controlling the valve train dynamics.
You do as your own risk assessment allows. There are no rules here, just solid engineering and common sense.
the dollars just aren't there...in actuality, or mentally.
could never bring myself to spend 10k on "just" an engine.
probably not even 5k.
hell, i've been putting together a boost-ready 16v engine (note i didn't call it a 16v turbo ) that admittedly will be "shade tree" in concept but all the components are proven already and aside from yet-to-be-purchased wear items (head gasket set, belts and WP) i'm hovering around $1500 for everything so far.
Yup, preachin' to the choir re. budget builds.
Donor engine, preferably a tolerance 0 or 1.
If the cylinders look very good, I bead blast the stock pistons and have them coated +.004" with Swain PC9, have my machinist do the last 2 steps in cylinder prep as per manual. I'll use tolerance 2 pistons in a 0 or 1 block to give me more machinable material if cylinder are scratched.
$40 per hole machine work, $125 for PC9 + ceramic tops = $285
New Mains + Swain Moly = $250
MM bearing mod (comes with bearings) $350
New valve springs = $200
Total seal custom ring set = $120
Gaskets/seal = $250
Stock header wrapped, with my own scavenge design after the 2 into 1.
I port match all gaskets and run a 2" flex hone in the intake runners running under a varsol solvent feed as cutting fluid.
$1500 race engine for Spec 1 or 2.
This new engine has to be a mighty mouse though bumping up a class for SP3. It has to compete at a disadvantage in displacement to the 3.0 S2 and 968 and a torque disadvantage to the 944T and 944TS.
I have to rev this engine past stock redline and take advantage of the free cams. Cams alone are $12-1500 and by the time you dump dollars in trying to make it reliable at +500 to 1000 revs, new valves, new lifters, new rods, new tuned header specific to application, new pistons (forged in place of budget build cast), it adds up quick.
$10k was a guess, but I'll have $5-10K in it.
07-28-2017 | 04:53 PM
) that admittedly will be "shade tree" in concept but all the components are proven already and aside from yet-to-be-purchased wear items (head gasket set, belts and WP) i'm hovering around $1500 for everything so far.
