jagerocks

I have a 1990 C2. I just installed a 12lb lighten flywheel, now after you rev the gas the engine stalls, I was told to 1st try installing a chip (which I did but not tried yet) it was a chip for Euro RS cars with lightened flywheel, they say it should correct the problem. I have mixed feelings. I will know when I install DME in car again.
2nd was something about modifing the idle valve...???? ANYONE have more info on this procedure if needed?
3rd was to jumper wire in DME the a/c to trick the DME in thinking it was on. (I don't like that idea) If using the chip doen't work then I would like to try modifing the idle valve.
Thanks Jason

John Boggiano

Jason,

Take a look at the comments in this LWF thread. You'll find them very useful, I'm sure.

Adrian

The 964 Carrera RS uses a different timing ring on the LWF to what you have fitted on yours. I would recommend that you do not waste your money.
The only reliable solution is to use a 19lb single mass flywheel.
I strongly recommend you do not try any of what I would consider idiotic solutions somebody has provided for you.
Mess with the DME and its inputs and you will pay a price.
The air conditioning input is used by the DME for two purposes. First is to adjust the idle and second to calculate engine load which affects the timing.
The DME receives two other inputs from the air conditioning and heating unit as well and by trying to fool the DME by faking one input will be offset by the other two inputs that are not faked and the DME may not use the faked input and you are back to square one plus the DME now thinking there is a problem.
Ciao,
Adrian.

jagerocks

thanks, but the chip is now installed and the flywheel also. I bought the like this. I haven't even drive the car on the road yet. Does anyone know how to adjust the idle valve? I personaly woul dhave just left the whole thing stock!
Jason

JasonAndreas

Adrian,
The timing ring IS the flywheel (unless I'm thinking of something different), the RS has a slighter different starter ring but that is mounted a half inch over from the reference sensor that's used by the DME. How bad is the stalling problem in a euro RS?

Adrian

Dear Jason,
There no such thing has a Euro RS there is only one RS and that is the 911 (964) Carrera RS and it does have a slight stalling problem especially when hot. It is a ROW market car and is found all over the world except one place.
By using the word "Euro" people may think there is a US market Carrera RS version. There is not.
There is an EU Porsche version now, country code C71 but that does not apply to the 964 Carrera RS.
If you want to call the flywheel a timing ring I guess that is your choice.
I am sure that it will confuse people because there are same flywheels with different timing rings.
So to avoid confusion here is the full explanation.
A single mass flywheel is one solid piece of machined metal made to form a flywheel.
At the outer edge of the flywheel is what looks like a set of gear teeth. This is called the timing ring. This is what the DME uses to determine the engine rpm and the position of the crankshaft.
On some flywheels the timing ring is a separate piece which is fitted to the outer edge of the flywheel and for others they machine the timing ring into the flywheel.
There is only ONE genuine 964 Carrera RS flywheel and timing ring assembly. Porsche refer to them as separate entities for a very good reason as I do. Companies sell aftermarket RS LWFs. However they have the standard timing and not the RS timing ring.
This is why I say a RS chip will not work with these flywheels unless they have the RS timing gear. I have yet to see one.
Porsche also refer to the RS timing gear in their documentation even though technically it is a fixed part of the flywheel assembly.
Ciao,
Adrian.

JasonAndreas

I think this is were (my) confusion comes from because when you buy a genuine RS lightweight-flywheel from Porsche there is no separate timing ring, the gear ring is the flywheel.


Visually the timing teeth on a genuine LWF are exactly the same (count, spacing, size) as those on a DMF. I don't think I have a picture showing both in the same picture but I might have something similar, I know I compared them when I had everything apart. What is the difference supposed to be?

Adrian

Dear Jason,
To confirm exact details you will have to ask Porsche.
I do have the differences written down somewhere buried in my 964 stuff.
Off the top of my head (remembering) they were very small adjustments to the leading edge of the teeth and in the gap but this was done to make the sensor more responsive to the rapid changes in rpm caused by the lightweight of the flywheel.
I cannot remember if they changed the gap between the sensor and flywheel. The 89 C4 is 0.8mm and the DMFs are 1mm.
These changes are not in the training manual for the RS either. They were in the supplemental RS maintenance data that PAG sent me.
What I do know is that if you install that LWF you are going to have stalling problems and there is little you can do to fix it and installing a RS chip will not help you either.
Ciao,
Adrian.

jagerocks

Thanks Adrian,
All I know is the flywheel is 12lbs. The stalling prob is very bad! you can't rev up or even drive and then put clutch in, it stalls ALL THE TIME. In my words it's not worth the hassel or extra performance. Unfortunely the car came like this to me. I guess the bottom line is I have no money to screw around with this and installing the chip (what ever it is ) did nothing to help as you said. Can I jumper the A/C to adjust rev's? or turn up idle? I guess the prob is the idle drops way too fast then stalls. Just at idle it runs great, but you have to baby it to idle, no pressing the clutch in when pulling up to stop signs or lights. COMPLETELY STALLS. Nothing but a total hassel!!! I was told that modifing the idle valve will work ..?? heard of this?

Thanks
Jason

Adrian

Dear Jason,
I have heard of all the mods, everything on this subject and been involved with it for a very long time. None of them work.
In fact messing with things like the calculation for engine load will make things even worse.
The fundamental problem is that the DME cannot react fast enough to the change in rpm.
No matter what you do the reaction time will never really be improved.
The idle cannot be adjusted. It is not the idle that is the issue it is the rapid change of rpm caused by the lightweight flywheel.
The flywheel does not have the necessary mass to slow the rate of change of rpm when you come off the throttle so that the DME software can handle it. This data is just not programmed into it.
You have a 1990 model year which has the very early DME software as well which makes the situation worse. The RS LWF did not come into service until model year 1992. There was a new 964 series DME introduced earlier from which the RS DME was a further developement. You will I am sure have a 911 series DME.
Yours sounds really bad which also suggests other problems as well.
Did you not test drive this car before purchasing it?
I understand this is frustrating but I cannot understand why anyone purchases a car like this without a test drive.
Had you driven it you would never have purchased it like this surely?
Ciao,
Adrian.

Dunasso

There has been a bit of discussion on the problems w/LWFs. There also seems to be alot of negativety about the adverse effects of the LWF, on many levels of concern.

Adrian, maybe you could help us understand why I have experienced none of these problems?
My 964 was born in Aug of 91 and titled as a 92. Is it possible that the later DME is in my car, and that could attribute to the lack of problems?

Also, I should mention that months previous to the LWF, I had installed a Hot wire MAF, and chip. Could these have had a possitive influence aswell?
I had no intension, nor was I told to combine these products for the result which has been acheived.

In conclusion, the LWF was the next step toward a more powerful/resposive engine in a series of modifications to include MOTEC or some equivelant.
I was expecting to purchase the MOTEC in addition to the LWF, knowing that the stock DME was not going to handle the mods I had instore for the future. However, sense it has not YET been a neccessity for the MOTEC purchase, I 've been postponing, to do more reaserch on other performance engine management electronics.

Duncan

jagerocks

Adrian,
I bought the car cheap $$ as is from a friend, it needed a pass fender and headlight. When the fellow replaced the clutch with a 911 turbo kit he also so called upgraded to the LFW. GO FIGURE, ALL I WANT IS TO ENJOY THE CAR AND DRIVE IT.

Thanks Jason

jagerocks

Duncan,
TELL ME MORE!!! should I and can I change my DME to newer version? When you say "HOT WIRE" what do you mean?

Jason

Dunasso

Jason

I really do not know what the differences are between the 911 and 964 DMEs. A Hot Wire MAF, has no vane to read airflow for the DME, but instead uses a heated wire to read airflow. The wire is very thin and therefore has little to no restrictive values when the flow of air into the engine is concerned. Where-as, the vane type (like what is on your car now) uses a door or flap to measure airflow. This door opening is not very large when compared to the throttle body opening and adversely acts as a restriction.

I started with the mild mods, chip, K&N, bypasses, muffin, etc...like most people do. Then I was quickly bitten by the performance bug. Hey, I got a Porsche screw the piddly stuff make some big changes. At this point I decided to buy a Hot wire MAF, as the vane type is much more restrictive. The next step was a LWF, larger throttlebody, injectors, cup cams, headers, and a 3.8 conversion. But as fait would have it, I haVE to go back to school for a few years to get the promotions that I felt were due to me at this stage in life. So, everything has been put on hold until then.

Duncan

jagerocks

Duncan , can you change from motronic flap to Mass air meter? The car is basicly useless the way it is. You have to feather the gas so it would stall which is very hard to do. I have contact to get a mass air meter, but then what about the DME, it will have to be changed correct?
Sorry for all the questions I have been out of the porsche sene for a while.
Jason