Tom W

Steve provides GIAC chips. While not a 964, the GIAC chip I bought from Steve did little to nothing for the stalling with my 993 (it was programmed for CA gas, and the LWF) - it did provide about an 8 hp improvement.

Cupcar#12

"911 Carrera & 964 C2/C4 '84-94 $450-

Chips programmed to European spec, CUP level, RS, and beyond.

Here are just a few of the DME's that are supported:

0.261.200.078 0.261.200.082 0.261.200.450
0.261.299.473 0.261.200.474 0.261.200.483
0.261.203.070 0.261.203.163 0.261.204.674
0.261.203.677 0.261.203.679 0.261.204.376

Special programs:

0.261.200.473 911 C2 chip for Mass air/Throttle body conversion kits. Silky smooth idle (common problem on these kits is a cycling lumpy idle), no more check engine lights.
"
from http://www.rennsportsystems.com/1aa.html
i believe he also provides customer 964 DME chips as well

JasonAndreas

So far the stall is winning 5-0 against the aftermarket chips that are supposed to have been specially written for the LWF but we still haven't heard from anyone with a Protomotive chip. Having personally dumped and disassembled two of them and looked at a disassembly provided by another Rennlister I think I might know why, they don't do anything to the two most important idle correction arrays I know of (idle control by RPM and idle fuel enrichment by temperature, there are probably more/others but I haven't gotten that far)
Cupcar, did the cupcar originally come with a LWF and if so have you ever had any stalling issues? The RS owners that have answered the poll don't seem to have any stalling issues.

Cupcar#12

The US cup car came with the RS flywheel - no stalling issues
full specs ont he site in my Sig

Lorenfb

"as far as custom Chips go" - Cupcar#12 -

It's not as simple as changing ignition or fuel maps. Basic idle algorithms have to
be changed which usually requires changes assembly language routines and NOT
just modifying tables.

jagerocks

I did clean my ISV today, it was a little stiff. Ans I made a adjusting screw with a "t" handle on it so I can adjust the ISV if needed to correct this problem as other have told me it might.
I hope it will make a difference. I will let you all know this week end. Stay tuned!!
Jason

Lorenfb

0.261.200.078, 0.261.200.082
These above are 911 3.2 DMEs.

0.261.200.450, 0.261.299.473, 0.261.200.474, 0.261.200.483

All the above boxes are basically the same with the exception of the EPROM used in the 964.

0.261.203.070, 0.261.203.163, 0.261.203.677, 0.261.203.679

These boxes are used in the early 993 and are a single board DME with more LSI integration.
They also have intergrated alarm functions.

0.261.204.674, 0.261.204.376

These boxes implement the OBDII functions & have additional VLSI functions used in '96-'98 993s.
Some have mask ROMs and the later ones use Flash memories.
These also implement "Drive-Block" (true immobilizer).

Bottomline: Few, if any of the above, have been modified for TOTAL idle undershoot correction!
Many claims, little to NO results.

For more info check out ( www.systemsc.com/Parts.htm )

Adrian

Dear Rob,
The USA edition of the Carrera Cup did come with the RS LWF but it did not come with the RS DME software. It was shipped with the Carrera Cup software level and who knows what Andial did to these cars' DMEs when converting them to road use.
I do not consider the Carerra Cup a valid example for this thread.
The results of using RS and Carrera Cup DMEs in a standard DMF Carrera 2 are in my book.

I also would like to bring to the attention of the ISV adjustment crowd.
The 993 has quite a very different ISV to the 964. The 993 version has two motor windings one for opening the other for closing with a 3-pin plug.
The 964 uses just one motor winding and a 2-pin plug.
Why 2 motor windings? To improve the response time.
Another significant difference between the 993 and the 964 is in how the DME is kept informed of the accelerator pedal position. In the 993 a potentiometer is used monitoring pedal position at all times.
In the 964 2-microswitches are used and the DME does not know where the pedal is for most of the time.
The long and the short of it is: You cannot defeat physics.
A light weight flywheel causes the engine to accelerate and to decelerate outside the capacity of the standard 964 engine sensors to react.
Since first getting involved with the 964 in 1998 I can honestly say that those people I have helped with this issue have NEVER properly been able to resolve it without radical and expensive surgery.
The stalling issue can be minimised by reverting to a more aggressive racing style software level which makes daily driving difficult or by just living with the problem.
I have never seen any company come out with an aftermarket chip to fix this either.
Lots of claims as Loren says but no real fixes. A thread very similar to this one with a seriously similar set of problems is buried in the archives.
Ciao,
Adrian.

Steve Weiner-Rennsport Systems

Hi Tom:

A clarification is in order. Indeed, I am a GIAC dealer however I do a lot of custom software that's not available anywhere else. Some of them are done on the premises,......


Now,.....a word about the stalling issues,.......

Virtually all of these cars (964 & early 993's) exhibit variations in their intake systems, components, and setups. While others like Adrian and Loren have provided some good information here, I will tell you that some of these cars have no stalling issues with the factory LWF and some stall like crazy no matter what we change. Honestly, I wish I knew why some handle these LWF's with aplomb and that's something further to learn.

Some cars can be "fixed" with a SMALL adjustment or modification to the ISV and if done correctly, will NOT result in a 1000-1200 RPM idle. Its a question of degree. Some cars respond to software changes as Loren outlined.

In some cases, a particular car will just not respond to software changes or ISV mods and a change in driving technique is required. Quite obviously, the decision to install the LWF becomes a judgement call.

There is no question that the RS LWF is not for everyone and I'm careful who we recommend these to. however in most (not ALL) cases the potential stalling problem can be minimized.

Like judging people, its inaccurate and unfair to characterize the LWF as an inherently problematic component in operation. Just like people, some cars handle it better than others,....

Adrian

Dear Steve,
A LOT of people have paid for the privelege of not ever getting a fix.
At least hundreds of dollars spent and for others a whole lot more ending up with a very bad feeling about Porsche and the 964 in particular.
They then sell their problems onto somebody else and the whole story and problem is recycled.
What you have said in your post is that you MIGHT or you MIGHT not be able to minimise the problem. Notice the useof the word minimise.
You and I both know you cannot eliminate this problem completely.
My advice is and remains unless a 964 owner is going racing do not try the RS LWF because it IS problematic and from your own admission some cars (I would add most normal road cars) you just cannot do anything with.
The list of failures worldwide exceeds the success stories by a long and wide margin.
In the end it is up to the individual owner and if they want to take the financial and frustration risk.
Do you give the customer their money back if you cannot fix the problem?
Most companies do not.
Ciao,
Adrian.

Computamedic

Adrian,

Given the obvious problems that the installation of the RS 12lb flywheel gives it seems that the '89 C4 19lb solid flywheel is a much more reliable solution - even though it's weight differential might not give the same crisp response as the 12lb unit. However, it seems the DME can cope with the 19lb unit much more reliably so it would seem, for someone who wanted to get away from the issues of the DMF (particularly the older design - if any are still left) the '89 flywheel/clutch might be the better bet.

Regards


Dave

PS Mine's an 89 C4 anyway so I don't have the problem.

Adrian

Dear Dave,
My personal opinion is that unless you REALLY need that kind of engine acceleration (not necessarily any major improvement in actual car acceleration) provided by a LWF I would retain the DMF.
The 993s all have DMFs including the RS and GT-2s (apart from the Clubsports).
There are much more productive ways in my opinion to spend your money.
To be quite honest and being an old racer myself I cannot imagine apart from on the race track, why in the hell anyone would want a RS LWF in the first place.
You just get to engine redline faster that is all and what does that prove on the road?
Constant velocity variable noise.
Ciao,
Adrian.

PS: Changing the gear ratios, remembering there are a number of different sets of 964 gearbox ratios, would be a more reliable bet. Everyone talks about the RS LWF but never mentions the G50/10 gearbox that goes with it.

Cupcar#12

Adrian, i was simply responding to a question in the post above. The Cup usa edition used a custom "chip" from Andial/Porsche motorsports, however i do not believe all of the series used this chip or have them today. This is due to the fact that the un-covered cars never made it to Andial (they stayed at the Port).
I did not state that it used the RS "chip".
it is probaly not the best example for this issue since the cars are somewhat of a special breed.

Adrian

Dear Rob,
I was not saying you were saying anything.
Your car is a very special breed and not a converted C2 but a purpose race car converted to road use but really still a track car you can drive to and from the race track.
My point though is that when special cars such as yours enter the fray people think "Well it works on that car" yet they have no understanding what "that car" is.
The RS is a case in point in itself. It is a special car designed for clubsport track racing.
It has many special parts which as a whole creates the Carrera RS package.
People take one little piece of this special car and stick it into a standard 964 and then expect an RS. It simply does not work that way.
This is something I have never understood especially seeing as there are no performance gains to be had for the normal 964 owners for doing such things.
Lightweight flywheels are designed to get your rpm up into the power band quickly as you know already. They serve no other purpose but what goes up quickly also comes down quickly and hence the problems with a standard car because nothing else is designed nor setup to handle the rapid drop in rpm.
However one can lead a horse to water but you cannot make them drink it.
If people want to spend their money on such things then that is their choice but they should take the hit. There is more than enough information available to say that the RS LWF is NOT a good idea for normal daily driving type 964 owners.
Ciao,
Adrian.

Cupcar#12

Point taken and agreed.
i also agree with you on the LWF issue - i personally would not use one unless i was prepared for the issues that go along with it.