Engine build progress

[TTM]

Closing the valve only after being pulled over, or even only after entering a crowded area is plain stupid as it will raise suspicion. This irresponsible attitude ruins the benefit of such a mod that actually avoids adding more to the "noise environment" of other people. Of course the added value of such a device may depend on where people live. My neighbourhood consists of dead empty country roads linking small villages in a hilly environment. Whenever I slow down entering a village or a town I am yet to see people turn their heads to me in sign of irritation, that is when people even notice me passing by. Naturally I won't be pushing my luck and do not intend to even try leaving the valve open in urban environments at all. As in the old saying "Pour vivre heureux, vivons cachés". Oli, you may find that a valve such as the one you're looking at won't let gases flow well even when cruising. Sly tried a similar one on his 3" exhaust and reported that the engine really didn't "work well at all".

 

[George Elliott]

If my car was standing on its front bumper, you could drop a tennis ball into the tailpipe, and it would stop at the turbo outlet flange. [8|] 3" minus 1.5mm wall thickness all the way, and stainless. The jetex stainless back box is good at keeping the noise in check. anyway, back to Finland and the Diamond Blue diamond George 944t

 

[Sly]

Hello all, At my last engine rebuilt I use a cometic head gasket, to avoid cylinder 4 problem with the original gasket. After 20000km at 21psi, some track days, and one year, the cometic gasket was leaking compression gaz in the coolant... The gasket is cut on each cylinder and looks worn at the top of the cylinders... I think this is because our engine aren't closed deck and the cylinder vibrate too much for this gasket. Some pics[]

 

[333pg333]

This is what we've all been experiencing when using Cometic head gaskets and higher boost. Especially on the track under sustained loads. The benefit is that if it happens at the track you can usually turn the boost down and still drive home, unlike the stock head gasket. Could be a number of causes or even a combination. Open deck, head lift, old head studs, high boost, high cylinder pressure, detonation....take your pick. There are a number of remedies too...but I'm not sure that anyone can quantifiably state cause and solution just yet.

 

[Sly]

Any experience with closed deck ? To complete informations - 1.5 years old - 21psi boost - less than 5 track days - a lot of highway driving - stud not new for the cometic but it was only the second tightening My old stock head-gasket blown at 21-22psi on track and I bend a rod. I will stay with a reasonable 18psi until I acheave my new engine...

 

[George Elliott]

Sly I think there are only a few people with closed deck experience, unfortunately I am not one of them [8|] as Patrick says, it seems to be a known problem, what I would add is perhaps its a good thing - like a fuse in a way. If it did not fail what would fail next / instead? Of course you may require 30psi qualifying boost[8D] Can I ask you what bhp / lb/ft difference you see at 18psi and 21psi? I run a less highly tuned car than yours, but it is sweeter at 1.2 bar (17.5psi), than 1.4 bar (20.5psi). Also better on FQS number 6 than FQS number 2. (timing retarded) Do you see any knock activity with your knock view? Can you retard the ignition? I would guess that knock would be very damaging to the CHG as it involves peak heat and cylinder pressure, but I am not qualified in the area, Hans Mezger would know the answer, he mentions this problem in his book ref the 944t at Le Mans. (2.5 16v)[] and I would guess open deck. good luck George 944t

 

[333pg333]

I don't believe Porsche used a closed deck with these cars during their time racing them...but you never know? I have used a closed deck and have a motor or two with them, but not in my possession. Along with the closed deck are larger headstuds which in theory should provide better clamping. Dowelled girdle and line bored as well. All these things should help resist head lift, block twist but they need to work in conjunction with a well tuned ECU and good fuel. Reading knock with E85 is meant to be more difficult as it is more knock resistant but also doesn't give such an early warning as regular fuel. Hoping one day to be able to speak with more first hand experience.

 

[barks944]

Patrick, is that a plate machined to fit into the top of the 944's block? How is it fixed in place?

 

[333pg333]

Yes it is. Having seen it in the flesh/metal, it is done very well and appears ex Factory. I don't know how thick it is nor how they actually attach it. My personal belief is that this should go a long way to remedying failure of headgaskets at higher boost and ign levels. It was also tapped to run thicker ARP headstuds. From distant memory I believe these are 9/16" in diameter.

 

[barks944]

Wow, it looks to be extremely accurately made. I wonder if they cut a step into the outside top of the bores and inner top surface of the outer casing and then drop the plate in.

 

[os951]

Friend made one closed deck block here in Finland. They went quite far to ensure it works OK. Deck was made from aluminium bar which was melted from some used 944 engine blocks.... Bars were also forged. This was mainly done to be sure deck material will work (heat expansion) exactly the same way as engine block.

 

[George Elliott]

Olli am I correct to assume the closed deck you refer to in Finland did not use steel liners? The factory Alusil cylinders remained? That would be an impressive unit with the correct Alusil material in the deck. Did it produce a lot of power? thanks George

 

[os951]

Yes it was without the steel lineres, a pure Alusil engine. Actually block was for 928.... I suppose this engine is not yet ready.

 

[Sly]

ORIGINAL: George Elliott as Patrick says, it seems to be a known problem, what I would add is perhaps its a good thing - like a fuse in a way. If it did not fail what would fail next / instead? Of course you may require 30psi qualifying boost[8D]

At 21psi, the stock gasket isn't good, I will reduce the boost to 19psi.

ORIGINAL: George Elliott Can I ask you what bhp / lb/ft difference you see at 18psi and 21psi? I run a less highly tuned car than yours, but it is sweeter at 1.2 bar (17.5psi), than 1.4 bar (20.5psi). Also better on FQS number 6 than FQS number 2. (timing retarded)

Don't know the difference in bhp, I never mesure it. But the engine has some more bhp with 21psi, it's an evidence when you drive it an compare to other cars. 21psi is the max that my turbo can do with no drop in presure at high rev. The engine is more brutal at 21psi under boost and I prefer that []

ORIGINAL: George Elliott Do you see any knock activity with your knock view? Can you retard the ignition?

I've a little knock but not a lot more than at 18psi. The ignition on fqs is in stock position.

 

[George Elliott]

Thanks Sly Interesting but I cannot help with the problem, 21psi is massive compared to the std boost which the car left the factory with - which I agree was not high enough[] Dont melt it[8|] The FQS may assist you with reducing knock, it certainly helped with my car. good luck George 944t

 

[Sly]

Hi Georges, I've tried retarded ignition with fqs, there was no visible difference for knock, my exhaust temp was higher and the engine under 3000tr wasn't as smooth as the stock position []

 

[TTM]

Quick update. So the tappet noise that my engine has suffered from since the beginning seems to be on its way out since I replaced the crappy Ti valve spring retainers with standard retainers. For now I have to make do with the camshaft and lifters that were used with the Ti retainers that probably slightly damaged them, but chances are the noise will fully disappear when I fit another camshaft and good lifters. Since Sly cracked the exhaust manifolds on his 2.5 (the brazing between tube 2 and 3 broke) we both decided to go on without any wrapping. Both our engines work great. Now that I am not seeing anymore knock at reasonable boost levels (1.0 bar) even with slightly lean mixture (AFR of 12.5) I suppose I will be able to increase the boost to 1.2 bar and see if it holds together - touch wood! Also, after 2 years of looking at ebay almost daily, I eventually sourced the right Audi gearbox with the right gearsets that will allow me to build a 6-speed gearbox that should allow me to crack 200 mph at 6200 rpm, not sure if I will try it out in fear of taking off and end up in a tree but at least it should return decent mpg on the motorway, as the engine at the moment drinks fuel at an annoying rate. The beefier diff bearings of the 968 gearbox should hold the torque of the 3L engine better too, as the standard AOR gearbox on the car now makes uncomfortable noises on decel.

 

[Sly]

Need to carrying some 944 gearbox or engine without dirtying your new 944.

[]

 

[George Elliott]

that will allow me to build a 6-speed gearbox that should allow me to crack 200 mph at 6200 rpm,

Have just read this and have to say WOW, what a prospect: 150mph @ 4500 100mph @ 2250 I often feel my car could pull another gear - but not quite the two tonne You will have a "951 yellow bird" TTM keep us posted George 944t

 

[TTM]

I probably found out why the front end gets so light at speed : the 968TS rear wing combined with the standard S2/turbo diffuser add too much downforce/rear drag. Since the 968TS has not diffuser at the back, I suppose I should have figured this earlier... On the very bright side of things it would appear that the faulty Titanium valve spring retainers messed up so much with the lifters that the software would understand the resulting extra valve train noises as knock and/or odd valve openings would cause (hopefully minor) detonation. Since I don't get "fake knock" anymore triggering the boost cut on the way, I have been able to make good progress with the settings of the closed loop boost control and I'm confident the car will be at last about fully tuned within a month. If I had found this out earlier it would probably have saved me the rather costly ECU upgrade and I would still be running the Vitesse MAF... but I would have still certainly come to an aftermarket ECU eventually, and looking back to it now, even if it has required some homework it offers great flexibility and has been an interesting new thing to learn, perhaps at the cost of having turned yet a bit further into a tuning geek! [8|] [] Last Sunday was the first time I drove the car at a constant 1.2 bar and I still can't believe how much faster the thing goes than at 1.0 bar. A difference of 0.1 bar on a 3.0 contains quite more oomph than on a 2.5. Not only have I eventually found back this supremely satisfying sentiment of confidence in a powerful and healthily-performing engine that I had missed since the 2.5 but it also looks like a genuine 400 bhp I heard many people boast about are well within reach, even if I had always doubted that kind of figure. Happy days at last... with both hands holding a huge stick of wood []