Christer

Jason

The altitude sensor fits under one of the seats, and one uses a code plug to tell the DME to use a non-cat fuel map. That way the DME does not look for a lambda input.

My mechs tell me that they have had no stalling issues with LWF converted cars unless there was a problem with the car. They said that very occasionally when cold the LWF cars will stall when cold but never when warmed up. Sounds to me that bears out the suggestion that the stalling issues are in fact myth - no chip needed?

jonfkaminsky

Sorry to revive this...but I;m closer to the clutch replacement. I'll try to ask the same questions another way.

1. Did Porsche allow the 964's with LW flywheels (RS or RS America) out the factory door with a stalling problem? If not, why couldn't one just obtain the bits and pieces required from those cars and convert a normal C2 to the LW flywheel without a stalling problem?

2. Can anyone with a stock RS America or 964 RS tell me whether they have stalling problems or not?

Thanks much

Jon

Rob W.

Jon, I am a late joiner to this thread, but can confirm that I had the RS clutch and flywheel fitted to my 1990 C2 recently and cannot recommend it highly enough. No stalling, no re-mapping just a very very responsive pick up, the revs drop off as alarmingly quickly as they pick up, which can necessitate a blip on the downchange to keep things smooth.

RobW

Cupcar

I have an American Carrera Cup (similar to lightweight 964RS) that I have owned since new that came with the LWF. I only very occasionally have stalling problems during brainfades at the stoplight and no more than with other stickshift cars I own. This with a higher 3.154:1 first gear that came in my car (instead of the normal C2's 3.5:1 first gear) which should make drive off harder in my car. My car does weigh a few hundred pounds less than a normal C2 and this should make drive off easier. My guess is the two balance out and my car is about as easy to drive off as a normal C2 from the standpoint of overcoming inertia.

I think the difference is that my car does not have air conditioning and that this drag on the engine is a major cause of stalling with a LWF that I do not have to deal with. Also my car has the RS brain which may be programed a little different and help the stalling issues.

BTW The factory equipped all the "Lightweight RS" and Carrera Cup cars with the LWF and the "Touring RS" cars all had dual-mass, so RS cars had both flywheels depending on model. <img border="0" alt="[typing]" title="" src="graemlins/yltype.gif" />

Patrik S

Jon, I have a 964RS with no stalling problems when warm.

It is a little more prone to stall if the engine is cold. The revs also hunts up and down some on idle. I do not know if this is do to the LWF? But many RS do this.
It is very sensetive and you do need a little more revs starting off in first gear compared to my 964 Turbo.
I can drive my RS in town and in stop and go traffic jams with no problem. But I am not sure I would go for the LWF if I did most of my driving on the street (with a lot of traffic....:-(. If you use your car as track car I would go for the LWF.

When cruising I miss the sophisticated and more comfortable ride of my Turbo. I sometimes even miss a stereo.....:-)

jonfkaminsky

Thanks guys. Thats the feedback I was looking for. We don't need air conditioning up here in the Northwest US (at least I don't need it) so perhaps that concern can be dispensed with. I also don't commute anywhere where stop and go traffic is an issue. I drive year-round on non-rainy days primarily when I have someplace to go other than the 10 miles to work. Sounds like my car would be a good candidate for a LWF.

Anatol

Hi
I have a 1991 C2 with RS LWF and clutch plus a Roock chip.
With the aircon switched on it does stall when you shift into idle from high to mid revs before a traffic light. But else there is little to complain, unless, of course, anything else is wrong with the car. When my cylinder head started to leak, there was severe stalling at idle.
The major advantage is electric "revability" and a contribution to 290 hp at the (LW) flywheel.
Hope this helps to convince you.

Patrik S

Anatol, "a contribution to 290 hp" if this is the case why does Porsche quote the RS to 260 hp?!
I do know of some RS´s having an output of 280 hp when clubracers tested their car when new (1992).
It is probably a case of Porsche modest hp quotes

Adrian

Dear Jon,
Some of this stuff has been mentioned but we have to have all the facts on the table here. You cannot compare a US C2 to a basic or NGT 964 RS.
The RSs are fitted with blue-printed motors. They are fitted with a LWF with special timing ring. They are fitted with a specially programmed DME. They are not fitted with air-conditioning. They are fitted with limited electrical systems to relieve engine load. They are fitted with their own special gearbox.
RS Americas were ALL delivered with DMFs.
There is a comfort model of the RS called a Touring version. This is fitted with a DMF.
RSs do have a stalling issue and Patrik indicates this. I have only driven Basics so I do not know about the NGT and touring models. The RS basic require constant monitoring of rpm. Again as Patrik says not unlike driving a Turbo especially in traffic. Remembering that RSs were designed to be driven to and from the track. They are club sports models not daily drivers.
I made a failure some time ago in suggesting that the timing ring can be changed. It cannot.
So in summary to convert the DMF C2 into a LWF C2 you need the following,
Remove air-conditioning.
Install correctly programmed DME or aftermarket chip which can be guaranteed to act as a full RS system. Remember that the programming change has to include all new timing maps, flywheel speed maps etc. A higher rpm setting is not much help.
Ciao,
Adrian
911C4

Adrian

Dear Jon,
I forgot something. Subtle but very few people do it. The DME receives three inputs from the aircon and heating control unit. These directly affect idle rpm. If you install a LWF and do not deal with the aircon and heating issues you will stall because of the lack of rotating mass and the idle rpm will drop too low and the inputs from the control unit cannot compensate.
I would also advise removal of the normal heating system and just run the heating bypass pipe.
Ciao,
Adrian
911C4

914und993

Patrik -

Perhaps Anatol is referring to calculated flywheel "horsepower" after doing a rolling road dyno with a LWF equipped car.

Because of the lower rotating mass of the LWF, the car will accelerate faster than one with a standard DMF - and this will be most apparent in the lowest gears. Since rolling road dynamometers really measure acceleration, in order to come up with a horsepower number they have to make assumptions about the rotating mass of the engine and drivetrain (they know the rotating mass of their dynamometer).

A car with a LWF will therefore give a higher calculated horsepower number than one with a DMF, since it will accelerate faster. This effect will be minimized if the test is conducted in higher gears.

The engine's actual horsepower is unchanged, of course, and this would be confirmed by finding no difference in steady state top end speed between a car with a LWF and one with the DMF.

Anatol

Apart from the RS LWF and the Roock chip, my car also has a larger throttle body, sports cat, K&N, drilled airbox and Cup pipe installed. The 290 hp are calculated according to DIN. At the wheels my car gives 215 hp at 6570 rpm. Torque was 323 at 5000 rpm.
Even though the LWF may not increase hp it makes the power far more accessible, especially in combination with my 993 6-speed gearbox.
My car still has the aircon and standard heating. The heating is no problem as far as stalling is concerned. And the aircon can be switched on on the open road or highway. No problem at all. However, I do not use it in town because then the engine frequently stalls.
Overall, with a good starter engine, the benefits from the LWF are certainly bigger than the negative aspects. Just compare the lazy behaviour of a standard engine with the eager revving of an engine with LWF and if you are into sporty driving, then everything is clear.

Adrian

Dear Anatol,
Not if you use the 964 as a daily driver and drive in town.
One has to differentiate. LWFs are for the 964 owner who spends his time on the track. They are no good for the daily driver. They are offer little if any advantage on the autobahn. Their main use is to provide more rpm more quickly. The stalling issue and other problems are major negatives for the average 964 owner.
One another issue, your figures above are showing a 26% loss of HP from the flywheel to the rear wheels. This is very high for a C2.
I am doing some research to see if the 1989 C4 single mass flywheel might be a better lighweight installation into the C2s.
I do not agree with your statement about the lazy standard engine and we will have to go out again and see. My C4 versus your C2. I will contact you soon so we can have another drive. You know where.
Ciao,
Adrian
911C4

Anatol

Dear Adrian
I am looking forward to the comparison. My car has evolved since our last meeting and I would be happy to let you drive it.
I will also bring my dyno print outs along. Incidentally I plan to have Sportec customise an RS chip for my modified engine.
Maybe I am a bit race oriented, however, I rarely ever use my car for anything else than fast alpine road driving where revving is essential.
Cheers!

Adrian

Dear Anatol,
I am still concerned about the loss of HP across the transmission shown by your dyno reports. I am interested in looking at this a little deeper for my own interest.
Torque is also very useful when climbing the mountains.
What is your rpm limit?
Has it been raised?
If you check out my new post on the 964 Turbo forum you will see what my C4 will turn into when I can afford it.
Ciao,
Adrian
911C4