jpitman2

And whats wrong with torsion bars as a springing medium? Lots easier to adjust than coilovers, can be made to have different characteristics easily (round bars, laminated flat strip etc), take up little space.....
jp 83 S AT 47k

Nicole

There were a few engineers from the factory who raced a 928, but I'm not sure, if that was sanctioned by the factory. I'd have to find the story agan...

I think, Porsche might have known about rod bearing failures, and at some point decided that it happens so rarely in street applications that there is no point in throwing heavy R&D money at a fix, when they had the 911 race cars.

What did Anatole Lapine say at one point? "The 911 is like an arrow that you are trying to shoot backwards" Yeah, it only goes straight becaue of the wheels and electronic stability control and blah blah.

Why did Sterling put in cast iron sleeves? I didn't understand from looking at the linked page on his website...

heinrich

gbyron, agreed to disagree .... no offense at all. Now, let's talk about the 924GTR, GTP and GTS .... phenomenal Porsches, and not that different from our beloved 928 ..... As Curt (thank you Dude) points out (and I had not read the article in Excellence) ... the factory was very specific about why. Makes sense to me. On the other hand, maybe they THEMSELVES underestimated the potential of the 928 engine ... just ask Kibort and Anderson, riiiight?

Fastest928

1 Open decks are superior to closed deck blocks for many reasons...efficiency, cooling, cylinder concnetricity integrity over heat ranges, etc. No one has ever had a "open deck related" failure under any non boosted conditions unless corrosion or other culprit was the cause

2 The reason they consider it unsuitable for racing is simple, weight of block, lack of internal dry sump capacity (Prosche does not consider external dry sumps viable for obvious reasons), and many design criteria conflicts with building a fantastic street engine.

Marc
DEVEK
550 rwhp

GlenL

Maybe it's real simple:

Porsche used flat "boxer" engines in their race cars and the 928's V8 was designed to power a GT car. What could be done with it was a seperate issue, but they never intended it to be a race engine.

Frankly fairly heavy and then there's the oiling issues.

Lagavulin

I agree that they'll do just fine in our typically low hp/L engines.

I assume that you're referring again to the 928 and it's low hp/L output in any current configuration, supercharged included.

If you take a look at the guys making some real hp/L, (..the Honda guys) they've had all kinds of problems with their open deck blocks. However, they have successfully solved their problems by closing the deck using varying methods.

2V4V

Marc,

As Lag very astutely points out, the Honda fellers have been 'fixing' their open decks for a couple of years now.

I'm love to hear the argument for concentricity - the engineers I know (and simple mechanical logic and experience) say that any cylinder that free floats at one end is more likely to deform when stressed. (Clamped down via the headgasket does not count as locating.) If open deck were more accurate and cool better, why is it not everywhere by now? It IS cheaper, somebody surely would have glommed on to the idea.

In the low output world of N/A, you can get away with open-deck. But in the high output world of forced-induction, there just are not open deck scenarios that I've ever seen.

This is a different engineering exercise than wet liners, one might be able to make the concentricity case a bit better in that scenario.

I would certainly agree with you the 928 block is way too heavy. Weighs almost as much as a 350 GM pushrod pig. Porsche coulda done a much better job on later iterations, but no investment= no results.

Porsche did an open deck design for one reason only - it's cheaper. It's a design flaw that needs to be corrected for a really serious high HP car. I think Mahle did the subcontract on the 928 block. Ask them why an open deck...

Yes Marc, ~100BHP/L is darn good for a streetable all-motor car. However, that's just not a terribly impressive HP figure when you go up against cars making 200+ BHP/L.

Even half-brained blown domestics (hey, that didn't sound quite right) will put out in excess of 600 WHP and not frag, with the correct setup.

Perhaps open-deck can be made to function in a N/A environment. It seems to work for your app. Cool. But, once you boost and get some serious HP, you need a closed deck.

Greg

Ben Allison

One way the Honda world has fixed the open deck problem is "block guards"

Here is a link to one:
http://www.prostreetonline.com/pso/p...0Block%20Guard

Basically it is tapped into the water jacket before cylinder boring (it can distort the centerline of the bores so it's a good idea to re-bore after installing).

Wonder if something similar could be made for our blocks? Since it would potentially also fit in the 944 blocks, I'm sure it would be worth someone's while to tool up and make one.

SHRKBIT

I think the vast consensus is that coil springs offer better handling and response than torsion bar suspensions can. I suspect the coilover type makes for simpler suspension design, too.

As to adjustment, my 928s have all had adjustable spring perches. I think most do.

Rich9928p

This is a strange discussion. Here we have a car that bone stock will do, depending upon model year, 130 to 170 mph range out the show room door. The 928 pretty much out performed any car of the day except exotics that cost even more. I'd say Porsche did a pretty good job ... at the time there was no CAD, it was all done by hand or by slide rule computations. Street racing, 1/8 or 1/4 mile was not the design target. Porsche had less than 2500 employees at the time the 928 was designed, quite a small company compared to GM, Ford, Chrysler, and thier European competition.

Fastest928

I thought this discussion was related to why the 928 engines was not considered by Porsche to be a racing engine. I do not recall any discussions about a drag engines, etc.

The FACT of the matter is described in the SAE study #880142 which discusses ring seal and block design.

100hp/l at 6000 rpm in NA from is not just good, it is the holy grail of efficient engine design! Find me those engines that run on pump gas and make more than 100hp/l at 6000 rpm? Where are they.....???

"all-motor"...what is this saturday night at the drags

200hp/l is no big deal in the boosted world...get real, more like 300 hp/l as in Supra, or 40 year old Offy...or better yet, how about Audi and their 1000 bhp 2l, or 500 hp/l...that is impressive! Sure they use closed decks, but they are extremely inefficient with BSFCs in the order .5-.6 lbs/hp/hr. Not a good "racing" engine is it if you have to fill up every lap!

Bob Norwood built 1000 rwhp 3.0 liter engine almost 7 years ago...a perfect blend of "all-motor" technology coupled with boost!

Always keep in mind, the more efficient and higher specific power output of the base engine, the greater the gain from a given boost....or an equal gain from less boost!

I prefer the later....

Oh yea, some of the Honda guys use a solid block with no water/cooling!


Mard
DEVEK
550 rwhp "all motor"

Donald

Wonder in what context Peter Falk was speaking in 1984- when he said "racing", did he mean Porsche Cup, or racing as in IMSA & 962?
I think the point re: mid-engine was lost in the muddle, having the engine mass behind the rear wheels is never a good idea from the viewpoint of handling.
What is the design superiority of flat opposed cylinders if F1 are using V-s (and mid-engine) even in narrow rpm band applications?
Nicole- IIRC Sterling did not put in cast iron sleeves. In addition to decking the head, he reduced the cooling passage by casting cement halfway up the cylinders. This is a drag racer's trick where cooling is less important than cylinder stability.
I was at Norwood's a couple of year's ago and saw his billet ricer block, as Marc noted, no cooling whatsoever. Stage it, run 5 or so seconds and shut down.

Normy

From what I read in my studies, we were becoming an issue, Porsche worked out all angles, and decided that since their largest market was the US, then they should tailor their ships as such as would recieve them.

N

Nicole

Ooops... I must have misread it then.

Wasn't the 1988 928 Club Sport also meant for racing? Why did then not do a club sport racing series? Political or technical? I do think it might have been both...

slate blue

Peter Falk didn't he also play a TV detective, Colombo or something.

Some good points have been raised here though. I think that a closed deck interference option would be nice, I think someone posted something about that already. I agree Marc that the more effecient the engine to start with the better it will take boost and use it in an productive way. I think I would like an egine that could rev to a max of 7500 but use 7250 like McMerc and use only about 15 psi and produce in the order of 650 hp. They have almost all there torque at 2200 rpm. It is one the reasons the McMerc was almost as quick around around a race circuit as the Carrera GT. 1.19 versus 1.20. Also remember that the McMerc is an auto and weighs 400 kilos more.