[banditsc]

You could theoretically replaced it with a spring centered clutch and get rid of the flex plate. I know Bob has had those thoughts rattling around in his head at one time. 

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[Rap]

I like the idea of Dan racing his tip!

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[968Syncro]

You could theoretically replaced it with a spring centered clutch and get rid of the flex plate. I know Bob has had those thoughts rattling around in his head at one time. 

Yeah, there are discussions about this in other threads.  He did look into it, but part of the problem is the time it would take.  Design something, install it, test it, maybe make changes, install again, test, make changes, install again.   Each R&R is probably a 6-8-10 hour process, pretty daunting time commitment.  I just looked again at the broken one I saved in the garage, the rubber is very hard, i was wondering how a solid disk would perform?   Simple CNC aluminum using the dimensions of a new rubber one.  Probably more vibration, but would that be dangerous for other items in the drivetrain?   Some day there will be no more NOS flex plates and something will have to be done.

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[flash]

besides the obvious pain of the development, the vibration is exactly the reason i bailed on that project.  when i was trying to come up with a damped clutch disk, i discovered just how much damping the DMF did, and what kinds of vibrations there are without it.  the tip already vibrates a lot more than the 6 speed, and i didn't want even more.  if i could fit a DMF in there, and still retain its abilities, it might have been worth checking out.  however, the bell housing is not the same, and i don't think there is enough room in there.

 

another 944 idea that doesn't seem to want to translate.

 

but, it looks like we found out just how much power the flex damper can take.

 

i think the key here is going to be in adjusting the trans so that it does not kick down 2 gears

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[jfrahm]

If you are staying a bit light on the throttle to avoid downshifts, as one does in an automatic, I'd be worried you'd also be out of WOT and boosting in closed loop.  IMO it is not safe to boost in closed loop, not enough fuel.  If the software has been modded to overfuel at cruise in anticipation of this I am not sure if it'd pass smog and it might poop the O2 sensor over time.

 

Look at a Saab or 944 Turbo and you see boost and knock controlled spark, they can pull spark when they see boost rather than getting knock and pulling spark too late.  I learned from boosting Saabs that I could have a system that works but for a really hot day or some bad or bogus gas and then something that worked 330 days of the year was in serious distress.  The car would get all thin and... it's hard to describe but it'd feel like small dog that'd had a bad day and been teased too much, getting ready to bite someone.

 

The cool thing about the Saab setup was that it'd dump your boost due to knock so you could see on the boost gauge that something was not right.  I could use manual boost control except for the dog days of summer when I had to plug the electronic controller back in for safety.  It's pretty easy to hear knock when it is really bad but the controllers would detect it much much earlier.

 

For the 968 my thought is that if one is serious then use an afrermarket ECU that is boost and knock aware and get tons of spark authority from CoP ignition.  Short of that, a system with several logic elements:

1 - Electronic re-circulation valve

2 - WOT switch or TPS based controller

3 - Water/methanol pressure/flow switch

4 - Knock detection

 

Allow boost only when at WOT and water "boost juice" flow is detected, kill boost with knock events.  Run a wideband and knock counter.  Clean living and prayer.

 

One might get some boost with the recirculation valve wide open, I think my car boosts a bit at midrange and under a bit of vacuum but it has a big blower on it.

An intercooler would help if for no other reason to provide a lot of effective manifold/plenum volume and reduce the rate of change of the boost.  Water injection is pretty magic in my climate also.  In a Saab with knock sensitive boost I could see the boost drop when the water tank was dry.  With the water working I could get really crazy with boost.  Superchargers are tricky though since they are always spooled, you have to prevent rather than react.

 

-Joel.

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[flash]

you keep harping on this issue of being in closed loop and boosting at the same time.  that may a problem with your kit, as all you have is an old school rising rate regulator, but not mine.  frankly, that is one of the reasons i didn't buy that kit.  i am telling you that what you are talking about is IMPOSSIBLE with my programming.  i rewrote the programming to take care of this, and i'm not talking about just fiddling with fuel and timing maps.

 

it passes smog perfectly too, even here in california.

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[94SilverCab]

This is above my technical level, but I know that the D1R kit is CARB certified....

 

Jay

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[flash]

lol - yeah - the secret was in the new coding.  not sure, but i think i am the only one to ever do what i did for ANY kit.  it was a major pain in the butt, and expensive, but well worth it, as it eliminates the issue jfhram is talking about, and one that i harped on with the maker of his kit back before i started developing mine, and one of the major motivators in me going forward with development, after going back and forth for over 5 years prior on the decision to make a kit.  it is a well known and common issue.  i knew about it, and would not install a kit that did not properly deal with it, as i knew it was going to be a ticking time bomb.  that is exactly why i spent so much time and money coming up with a real solution, just like the factories do when they do forced induction.  i actually used the same idea and developed and incorporated it into this ECU.

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[jfrahm]

I think it's fair to say that I have heard you say that you solved it, but not how.  I do not see how that can be compelling.  

IMO there is not an adequate software fix for the issues that do not have unwelcome side effects.   You say it's been solved because <secret magic>.  Fine whatever.

I stand by my advice above for supercharging a 968 motor, unless maybe the 968 DME has a MAP sensor I am unaware of.

The lack of *hardware* to *measure* boost and *control* boost electronically IMO make it necessary to increase the safety factors for safe street operation, or better still build in a way to prevent boost in unfavorable conditions.

 

I suspect the common supercharged motors on the market nowadays use DBW throttle control for protection, and I see the Audi 3.0T has an electronic bypass valve.

I am not aware of any 968 supercharger kit that has that sort of protection and thus a tank of fake premium and a hot day and a heavy foot is likely not going to end well.  You can assume this risk, which is reasonable for an aftermarket supercharger kit, or try to mitigate it.

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[ds968]

Out of about 50 D1R SCs in 968s out there, many of which are tracked regularly, I haven't heard of a single street use one ending up with a blown up engine ( and there is a separate 968 SC faction to which I belong, so I would have certainly heard of any mishaps ..)  As for cars which are tracked, I think there may have been a couple which have had engine failures, but whether of not those failures can be attributed to the above theory remains  questionable.I drive my six speed like a bat out of hell, always taking it to near redline when shifting, and even when cruising  it's around 4000 rpm +.   No problems there.  However, having said that , to my knowledge this is only SC'd Tiptronic 968 on the planet, so there must be something inherently riskier associated with automatics, and I'm not talking just about the flex plate issue, but the way the Tip computer may be designed / programmed, which I have to believe is materially different vs the six-speeds. So one can try to mitigate as much as possible by reprogramming the mixtures and whatnot at multiple levels across the band and a variety of styles of acceleration , decelleration ,and so on but maybe it has a point beyond which, unlike the six speeds ECUs, it limits just how much can be reprogrammed.   No idea, just speculation form someone who is mechanically clueless ..                  

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[PorscheG96]

The only major differences with the Tiptronic DME are lower RPM engine idle to be kind to the torque converter and briefly retarding the timing when changing gears to make the shifts smoother & reduce shock to the driveline.

 

Can you ask the engine builder what condition the oil pickup tube was in? Thinking out loud here but the potential side effects of the DME controls above are lower idle oil pressure and more vibration which could theoretically reduce the life of the oil pickup which is already prone to cracking. One of the main reasons I'm eager to build and install my high-RPM 968 engine into the blue car is that it spent the first 55k miles of its life as Tiptronic and I hear lots of unhappy hydraulic lifters after a few autocross runs. Guessing that my pickup tube could be compromised but I haven't confirmed it yet.

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[ds968]

Will ask him re the pick up tube condition.

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[flash]

jfrahm - i haven't said how, because it is proprietary.  if i gave away the secret, anybody could do it.  it cost me thousands to get it right.  i'm not giving that away.  there is adequate hardware to tell the ECU what is going on (though yes, a MAP sensor would be better), and the new programming takes advantage of the hardware and prevents closed loop during boost. period.

 

pretty sure the tip idle is actually higher, not lower.  880 vs 840

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[ds968]

I set my idle at about 1100 to mitigate that annoying vibration.  

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[flash]

oof - that will be hard on things over time

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[ds968]

I lowered it a little after the new motor mounts installation, probably around 950 or so. That was less than a week before the engine blew up,  Hmmm, wait a minute , THAT HAS TO BE what caused this still mysterious disaster .  These engines are not meant to run smoothly and the lack of vibration throws every balance out of whack causing piston rings to break and who knows what else !  That's my theory and I'm sticking to it !               

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[banditsc]

How did you bring the idle up? Thru the cable?

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[Bulti]

There is an idle adjustment screw, but normally you are not supposed to adjust it. It is factory set.

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[ds968]

It's a " reverse " screw right under the throttle body lever . So you can't use a screw driver to adjust it because you can't get to its head, but with pliers you can grasp and twist the screw's stem to adjust the idle . Unfortunately it can't be done with the engine running ( and gauge it by ear or feel ) because you have to lift and hold the throttle lever wide open while you do that , so you end up adjusting it once, going back in the car to turni the engine and see the result of the RPM level, then off again and back to more adjustment, repeat, repeat , repeat... all of that until you get the RPMs where you want them .


BTW - no reply yet from the builder re the oil pick up tube ..still trying to get a hold of him ..

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[ds968]

Oil pick up tube is in " excellent " condition.

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