jonfkaminsky

I know this has been covered here and there, but I have not discovered the definitive answer I am looking for.

When "upgrading" say, a 1991 964 C2 to a lightweight flywheel (e.g. the RS version), I understand that there is a stalling problem. Chip tuners attempt to make corrections here and there. These corrections for the most part trick the system into believing that all the options are turned on along with AC, which apparently allows the engine to maintain idle, etc. From what I have read, this hack is only a partial solution.

So what is the real deal?

1). What is so different about using a LW flywheel in a non-RS C2 that does not allow for a correct fix? I have read just using the original motronic timing ring solves the problem...but IF so, why all the chip tuning?

2). Further, did the RS America have a LW flywheel, and was it the same LW flywheel as the Euro RS?

3). Why can't you just take the necessary parts from the RS and fit them to the US C2?

I'm asking because I believe I am due for a new clutch and I would like to look into this further, but I am not at all attracted by chip hacks that poorly solve the problem.

Thanks for all input,

jon

Bill Gregory

Jon,

RSA's had the same drivetrain as normal C2's, with the DMF.

The problem associated with the LWF on 964's is a hardware problem with the idle positioner, and software can't keep up with rapidly dropping revs. Porsche did fix it on 993's, so if someone just back engineered the fix to our 964's....

I asked about the Andial semi-light flywheel recently, and they still have them in stock. I believe Randall has one, and has no stalling problems. So that's another option.

David K.

Here's the parts for the RS Light Flywheel and Clutch:

964 102 239 31 Flywheel
964 116 011 61 Disc
964 116 028 90 Pressure plate
944 116 080 01 Bearing
950 116 813 30 Tube
964 114 143 31 Ring
931 102 111 00 Bearing
928 102 151 01 Bolt
n 014 715 3

To stabilize the idle all you need is a Cyntex Chip. Cyntex's chips work. You will not have idle fluctuation or stalling problems even with the A/C on. Cyntex's phone # 610-738-8804.

David Katz

Alan 91 C2

Jon,

I recently, removed a LW flywheel. In addition to the annoying stall problems with the A/C on, I found the engine easy to stall when starting off at a red light, particularly with high noise around. The light flywheel makes for spirited driving but the spirit wears thin when your in stop and go traffic with a few stalls thrown in.

Alan

914und993

This is my reasoning, it doesn't carry any credentialing to back it up:

Part of the reason it is difficult to keep the engine with LWF from dying when it has a load on it (A/C) or is cold has to do with pollution control/fuel economy.

When you take your foot off the accelerator, and the engine is well above idle rpm, the DME completely cuts off the fuel injectors. If the A/C is on, you are at 2000 or so rpm and up, and your foot is off the accelerator, the engine is getting no fuel. If you then declutch, the rpm drops so fast that the idle circuit is unable to kick in with fuel quickly enough to keep the engine from dying.

In my C4, I had an Autothority chip that was supposed to help. I think it did no more than set the idle a couple hundred rpm higher, but it did not cure the stalling problem - this was 5 years ago. I too found it annoying enough to be part of the reason I sold the car and bought a 993. I haven't heard how the 993 handles this differently.

If there is a 964 chip that solves the problem, they should have a money maker. I wonder how they do it? Easiest thing to do would be to always have the fuel injectors putting out a minimum amount of fuel - I imagine that the appropriate amount of idle air is still coming in anyway with the throttle closed.

Chip

Randall G.

I'm a member of the used-to-have-a-LWF, couldn't stand it, replaced it with the LUK club. That said, back in '95, when I was going through all my agony, I wasn't aware of any band-aids. Thus, I haven't tried any of the purported fixes.

Sorry Bill .... no Andial semi-LWF on my car. But, as far as I know, they have no idle problems whatsoever. Also, I know of one '95 993 owner that cured his chronic, LWF-induced stalling problem with Andial's semi-LWF.

'95 993s struggle with a LWF just like 964s. It's the 96+ OBD-II cars that do well with a LWF, no mods required. Lots of guys on the 993 board with OBDII 993s have installed LWFs with no trouble. I think I read of one person that had an idle problem, but it turned out to be a problem somewhere else that was exacerbated by the LWF.

Another fix that has worked for many '95 993 owners w/LWF is the self-mod performed on the ISV (check the archives). Probably the same mod that vendors charge some $150 for when they sell you a LWF-supporting ISV.

It seems like some people have luck with idle band-aids on their 964, other people don't. After my own experience, I would be real hesitant to install a LWF on a 964--I could be one of the unlucky ones. Perhaps if you have a confident mechanic that's willing to replace the LWF with a DMF and eat the labor if the LWF doesn't work out?

Jeff Curtis

The problem with the flywheel, to answer your question directly Jon, is lack of rotational mass.

This in turn causes rapid deceleration and the fuel injection/DME setup in a 964 can't keep up with it...this is why OBDII systems were developed with 4 oxygen sensors...to sense rapid changes and deal with it.

Adding the Andial weights to your flywheel just puts you back towards having a HEAVY flywheel again...adding rotational mass, so now WHY would you have a lightweight flywheel??

I know, your flywheel is still lighter than a LUK or Freudenburg with the weights, but still!??

The proper fix is one arguable topic:

1) Program the stalling issues out with a chip.

2) Upgrade your ISV to an adjustable one.

I, for one...plan to use BOTH!

Bill Gregory

</font><blockquote><font size="1" face="Verdana,Tahoma,Arial,Helvetica,Geneva">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Arial,Helvetica,Geneva"><strong>2) Upgrade your ISV to an adjustable one.</strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Arial,Helvetica,Geneva">Jeff,

I'll be very interested in how you upgrade the 964 ISV. I haven't looked into it much, but the notes and articles that discuss how to alter the ISV seem to be 993-only, and the 964 and 993 have different parts.

Please take pictures and keep us informed!

schubee

I just visited Andial to pick up some brake parts and since this was a topic discussed today, I decided to further educate myself. The flywheel they sell is a LWF with an added weight. Pete showed me the difference. After adding the weight to the LWF, it's only a 7 pounds difference with a total weight of 19 pounds. I believe the total weight of the DMF is somewhere around 30 pounds. Here are some prices he quoted me with:

AND 114 001 00 Flywheel Kit - $760.00
Extra weight - $411.00
Disc - $298.00
Pressure Plate (optional) - $428.00

He did mention to purchase the disk they supply which would work best with their semi-LWF.

Jeff Curtis

Bill, all the ISVs are adjustable, it's just that the factory sets them and puts epoxy in the hole where the adjustment screw is.

...and they do a pretty damned good job of it too! <img border="0" alt="[grrrrrrr]" title="" src="graemlins/cussing.gif" />

I've cleaned out the hole where the screw resides but can't seem to get the screw to turn. I'm guessing I should read the 993 post, there's probably some good info. like heating it up or something crazy that loosens up the epoxy.

John, nice work on the Andial info. - it just seems crazy to me that someone would spend $411 to add 7lbs back into a clutch assembly that just saved you 19lbs...when that $411 could buy you the pick to get the epoxy out of your ISV to make it adjustable AND buy a performance chip that programs most of the stalling issue out.

Christer

Just one idea that might work for folks who do not need a lambda sensor, or catalytic converter. Recently my car was diagnosed as having a 'slow' lambda sensor, in fact it was so slow that when revving the engine up to say 3000rpm standing still, it was hardly catching the revs before it stalled etc. Recently I got rid of my CAT anyway and my mechs suggested that I use an altitiude sensor instead of the lambda sensor, firstly because the lambda was on the way out but more importantly because the altitude sensor reacts far faster than the lambda sensor does full stop. Now, the throttle response and idle is far better than it has ever been, and I thought it might be a solution for *some* people. I can have a word with the people that did this on my car to see what they think - a chip may not be necessary...

Bill Gregory

Jeff,

The 993 ISV adjustment post is <a href="http://forums.rennlist.com/forums/ultimatebb.php?ubb=get_topic&f=3&t=002968" target="_blank">here</a>

jonfkaminsky

Thanks guys for the informative replies. So, apparently this was offered an option on the RS (I am assuming Euro) or did the Euro RS come stock with the LWF? If either case is true, how could Porsche let these things out the door with stalling issues and what not? If not, I guess what I am driving at is that if it worked correctly on some version of the 964, can't that HW and SW configuration be copied over to a normal 964?

Christer

Jon

The RS came stock with LWF. I think when the cars were new the LWF was not so much of a problem. The stalling issue has surfaced when a lot of older cars have the conversion done and their sensors and whatnot are slower than when they were new. I am not saying that every case is like that, but who converts to LWF and replaces all their electronics bits and pieces at the same time? As I said above, my throttle response is 3 times better than it has ever been. Obviously switching to an altitude sensor is not for everyone because of emissions, but having experienced a lambda sensor, not failing but getting slow wakes one up to the possibiluty that Porsche did not ship cars out of the door that were prone to stalling.

All IMHO.

Edit: BTW, I am aware that the RS had a different DME and timing ring which presumably helps matters, but I think ageing electronics can play a part.

JasonAndreas

</font><blockquote><font size="1" face="Verdana,Tahoma,Arial,Helvetica,Geneva">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Arial,Helvetica,Geneva">Originally posted by Christer:
<strong>Obviously switching to an altitude sensor is not for everyone because of emissions, but having experienced a lambda sensor, not failing but getting slow wakes one up to the possibiluty that Porsche did not ship cars out of the door that were prone to stalling.
</strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Arial,Helvetica,Geneva">Where in the car and how was an altitude sensor hooked up to your car/dme?