Precisely why I had my block & skirt "shufflepinned" like the 911 block halves.
Hammer

 

John:

Thanks for the information. I've got a GTS "pingmaster" on my dyno as we speak. It is hooked up to the Sharktuner and we are trying to get it to work. I think Joe got some new firmware from you....whatever that is. I also had to get a new chip burner. My 1970 model didn't work. We're going to try again on Friday.

The GTS engines did indeed use a 8 counterweight crank. I'll see if anyone in Germany can give me an answer to why. In the high performance engines, we've found that the 6 counterweight cranks accelerate the engine significantly faster and the cars get out of the corners much quicker than the 8 counterweight cranks....with very similar engines. As I said, that one reason we use the 6 counterweight cranks, light rods, and light pistons.

I can't see any quality crankshaft breaking in 928 use, regardless of how many counterweights are on it. The engine simply doesn't spin high enough or make enough horsepower to be a problem. Now if one of those Chinese pieces of crap broke.....no one here would be surprised.

greg

 

Hello Greg
Joe may find that some datalogs of knock per cylinder while driving on the road are easier than on a dyno. Each car I have logged has a different knock pattern as to which cylinders knock first. This implies varying injector flow rates.

If Joe needs any advice he can call me on +44 1223 709915 We are at GMT local at present.

 

Could someone please give me a contact at Porsche might know about the development of the 928 and other blocks? I know that sounds like alot to ask but it would mean alot to me to have the opportunity to communicate with someone even if it doesn't lead to any revelations that would be helpful in my block reinforcement quest. I promise to be respectful of their time and only communicate with them as they see willing to, even a general contact would be appreciated.

 

Most of these guys have already retired from Porsche, although a good few of them attended Euro 928 in 2003 (?)

If you read "Project 928" this gives names of people in charge of various aspects of the project. It may be possible to contact these people through some contacts I have in Germany.

I do rememeber reading that the first couple of dyno runs ended early when water leaks started. This required strengthening of the block.

 

John, I ran accross in interesting quote from an Innovative engineer Klaus discussing WB datalogging and detonation:

"But when you see sudden lean areas that are not typical spikes from ignition misses and can't be explained by carb/injection events, high speed knock is something to consider. This is especially true for engines with factory knock sensors, as most factory ECUs don't listen to knock sensors above ~4k RPM anyway because engine noise masks the signal too much."

Do you have any thoughts on that? How does the 928 handle the knock signals and are they reliable on a modified engine at high rpm?

BTW, thanks for the book recommendation. That's an awesome read.

 

Some of those same engineers might be in 928 Club Germany meeting June 15-17th in Stuttgart.

 

Hello Mike
The 928 knock system is pretty good. That's why it needed a seperate processor to handle all the knock data and make sense of it. Couldn't do the LH stuff at the same time.

I've just set up an LH on the test bench with a SharkTuner, and I am running it at 5000rpm at high load, and it counts knocks reliablely and retards the igntion accordingly.

They are very clever with the filtering and sampling of the knock sensor signals.

I re-read "Project 928" yesterday and I see that it isn't much help on the block question. One problem is the rather poor German to English translation.

It would appear that the first failure was near the top of the block, and resulted in coolant leaking out and also getting into the oil.

The second failure appears to be in the lower ladder, which they refer to as the "lower block" .

The members of the engine development team aren't mentioned, but it would appear that Helmuth Bott was in charge of that team.

As Erkka says, it is likely some members of the origianl team will be at the 928 Club meeting in Stuttgart this summer.

 

Interesting. So, it just doesn't 'give up' after 4k rpm. How are you simulating the non-knock-related engine noise on your test bench? White noise? Sampled characteristic noise?

 

I didn't introduce simulated engine noise in this instance, but when Sharktuning EZKs on the road I have observed knocks and knock related ingition retard up to the red line.

 

Excellent!

 

John, project 928 gave me the impression that the first block crack was up top around the oil fill/water 'tower', it's hard to know though. It looks like the original engine didn't have the intermediate 10mm studs that production engines have but just the 12mm studs and the outter 8mm bolts, I wonder if that was the change after the lower cradle crack? Regardless of whatever problems they had I think it's safe to consider a 928 block as inherently weak and in need of reinforcement for high HP use which is hard to implement, I'm kicking around several ideas but there's just no easy fix.
BTW, You have me seriously considering a trip to Europe this summer. The hope of possibly meeting some original Porsche people is very tempting and my wife loves to travel, hmm...

 

What do you consider high HP? And I would say that it is important to differentiate how you are achieving this higher HP. Getting to XXX HP via stroking and/or more RPM is much harder on an engine than achieving the same HP through forced induction.

 

Anything over stock should be considered as pushing the limits of the block. Don't assume that a low rpm pressurized engine is safe from issues, the block is going to be stressed higher than it was intended to be and it sounds like it was near the limits all along.

 

Oh, I'm not saying that it is just as "safe" as stock. I'm just saying that it is less stressfull to the engine and I think that it is imprtant to differentiate the differences during this discussion. Tha is all. BTW, this is a great thread.