Rick Carter

Does it fit in an 85/86 4v head?

Bill Ball

So, what is it? I've been worried about making sure there was adequate oiling of the lifters and cam faces at high RPM. However, I gather the 944 valve is used to reduce EXCESSIVE oil flow to the head under race condition and oil loss via the breather system. I always thought there was something not right about the breather system and not the oiling to the head.

Kevin Johnson

Sorry to drop this in after calling a draw -- I think it is important to explain the machining process.

That's a good practice.

The edges of the rod and cap show the relative depth of the pieces clamped in a machining fixture. There are depressions that are somewhat U shaped on both sides of both parts. GKN was very proud of the fact that the parts emerging from the forging process could use these depressions as the standardized indexes for subsequent machining operations. That means the depressions and therefore the morphology would be held not only mutually parallel but on the same level.

For a part -- these surfaces that are to be even -- to show almost a 1.9mm shift to one side means they were not held in the same fixture at the same time. That is a huge shift for a precision operation.

Note that this does not mean you would end up with two parts with overall different widths -- it just means they were not in the same fixture at the same time. The fixture(s) could certainly shift or be adjusted at some point in production but the shift would be mutual for both the cap and beam.

There are two possibilities for the PF rod:

1) That it was a single forging that was machined, cracked in two and subsequently machined: the surfaces would be parallel and even.

2) That it was a combination of two separate forgings that were subsequently brought together and machined in the same fixture: the surfaces would be parallel and even.

No, the sizing is completed on the fixture before rod bolts are put in. In fact, in a recent patent application describing the prior art for all PF cracked rods one of the weaknesses stated was that the bolts were installed loose and could come apart easily and parts would then be mixed up.

People are confusing resizing operations or the manufacturing methods on non-PF components with the techniques used at GKN.

The mid 1970s Porsche 928 rods developed by GKN in the UK were the first volume production PF rod. This should be a bragging point for 928 owners more so than integrated flexible bumpers.

Kevin Johnson

I would be more worried about selecting an oil that has not been essentially stripped of its anti-wear package. That is a development since these tech tips were published. Mark could probably chime in here.

Jim bailey - 928 International

The rods could have easily been saw cut as well. Possibility # 3 The grooving and fracturing seems to be a later design element with the irregular fractured faces used to strengthen the joint. 928 rods show no evidence of a groove (stress riser) and the faces are machined. The problem of doing machining on an irregular shaped part was encountered the very first time anyone ever machined a part ! You have to cut one surface.....any surface and reference everything off of that. You can make a cube out of a sphere and the first surface cut makes no difference at all. The same is true of a roughly forged rod after it cools from 1,000 C while there is no flat true surface you create one and reference everything off that . I also believe that the rod caps are firmly torqued to the rod with bolts for the final machining of the rods on all but possibly the latest fractured rods. The primary advantage of the powder forging was ease of manufacturing , cost savings , limited waste , and less machining needed . Not so much that it makes a superior product although better than cast. Even with all their Porsche design and engineering they completely screwed up on the early GTS rods !

Bill Ball

I don't think that is an issue unless you pick one of the "energy efficient" oils. The SM or SL are still fine for antiwear and OK for our engines as long as they exceed Porsche's requirement of a HTHS of 3.5 cSt. Doug Hillary has covered this.

Kevin Johnson

Yes, you're absolutely correct.

Prior to that I believe an undulating surface was machined in (electron beam or laser -- cannot recall offhand).

This is not the case with the PF rods -- the as-forged formed surfaces were accurate enough to be held in a fixture. GKN cites that. I used to do precision lost wax investment castings. You can easily create an accurate area to fix a jig to. In a sense the reference machining you're thinking of was done in the mold and the process is accurate enough to carry it through to the forging. This is one of the things that makes PF rods attractive economically -- many saved steps -- as you mention below.


That does not agree with the prior art cited in the patent application I mentioned. You can look that patent up and then follow its citations back and check out the abstracts and descriptions and their prior art citations and so on. It's time consuming but worthwhile. That is what the patent examiners do.

Mr. Manfred Lerbs at GKN Hueckeswagen mentioned that "it was not generally known that a Krebsoege PF con rod went into the Porsche 944 engine used in the McLaren-TAG Formula 1 racing car, which in 1984 not only won 12 out of 16 races, but also secured the world championship for Niki Lauda the same year."

But I agree that there is a lot of room for improvement in the 928 rods. While the static balance may be accurate the dynamic balance would be off because of the variations in machining that I mentioned previously. They are what they are -- nothing more or less.

Kevin Johnson

Ok.

Bill Ball

too.

brutus

Before making any more comments about the TAG Porsche Engine being 944 based you might want to count the number of cylinders....here is a hint. In the mid 1980s, Team McLaren dominated Grand Prix racing with their carbon fibre MP4 chassis and their Porsche-built TAG Turbo engines. Between 1984 and ...
www.motorsportcollector.com/MEMtag.html - 10k - Cached - Similar pages

Kevin Johnson

You're an interesting guy. In the spirit of Easter, be nice... ok.

Here's something you may want to look into. The Suzuki G10 is based on the G13. The G10 has 3 cylinders while the G13 has four.

The engine in the 928 has 8 cylinders while the 944 has 4 cylinders. The 944 is known to be based on the 928 and the G10 is known to be based on the G13. Add a second bank with an 80 degree included angle.

Hans Mezger designed the P01 so you could always consult with him.

Much information about F1 engines is not common knowledge.

Fabio421

Following this train of thought, shouldn't we be able to claim that the TAG F1 engine is 928 based?

Kevin Johnson

Sure, but you can see lots of changes even from the 944.

I get caught by this fairly regularly, though. The G10 and G13 are examples where it is really obvious the block was truncated. Same with the Mopar 3.9 V6 versus the 318 LA. However, the SBC into the 4.3 90 degree V6 -- lots of changes at least in areas I had to pay attention to.

When BMW redesigned their sixes and fours they allowed (some) crank interchangeability.

I was surprised when the Ford and Datsun guys told me about how you can machine a Datsun crank to fit in a Twink.

Benneli Sei -- that's a Honda 500 with two extra cylinders tacked on.

Then there's the modular Volvos...

After a while you can even begin to recognize the style of the designers -- before I knew about the Volvo/Porsche connection the interior of the modular block just shouted "Porsche."

Gotta love engines.

blown 87

I was talking to Mike Grubber, who is the long time NHRA rep for Valvoline about this last week.

He says that Lucas Oil has a additive now that contains the missing anti wear additives and is made for just that.

I have no idea what the additive is called.

For what it is worth.

Greg Nettles

Vilhuer

Looks simple enough. This one is from 944 S head.



Oil enters in from the left and exits at the middle. Lower of the two o-rings keeps different pressure areas separated and upper one prevents 3bar pressure escaping to the head.