dougn

i like my RS LWF and don't have stalling issues. i have 3 eproms....the stock one and two done by steve wong. i can tell you there is definately a difference between the EPROMs with regard to stalling....

with regards to acceleration you can feel the difference in 1'st and 2'nd for sure.

Steven C.

So you are happy with Steve's work?

Heirsh

Geoff,

Perhaps one day! I'll add it to my years long list of projects!

Never enough time.

dougn

yes, I have switched back and forth between chips a few times and have dynoed my car a few times. i can feel the difference between chips at part throttle and i think at full throttle. i am pleased with the dyno results also. i'm going back to the dyno soon. hope to exceed 250 RWHP on a dynojet 248D

as far as the flywheel is concerned, the second chip I got from SW works much better than the first. he raised the rpm at which the fuel turns on as jason was mentioning

Red rooster

Jason,
I would have prefered not to have the rubber center but there wasnt time to investigate other options . I still wonder if a spring centre plate would have done just as well !
Maybe a quick look at overrun timing + basic idle timing as well as shutoff rpm + ISV dwell would ensure success in fixing the stalling issue ?

All the best

Geoff

Lorenfb

So, there still appears NOT to be a real solution, i.e. a u-code rewrite of the idle algorithm,
other than kinda work-arounds, e.g. raising the fuel shut-off point. It shouldn't be too
difficult to "work back" from the idle output (P1.X) of the u-p and then determine the
existing u-code requiring modification. It's basically a modifcation of the rate of change
of the idle valve duty cycle.

JasonAndreas

With the spring centered clutch I think you definitely would have had noise/vibration working its way into the passenger compartment? The MY89 flywheel and the LWF are basically the same thing. So the only differences are the increased weight of the MY89 pressure plate and the rubber centered clutch disc. If you aren't hearing anything with your install then it might be worth it for me to look into adding a rubber centered clutch to my LWF? I don't have heat in my garage so it will have to wait until spring (unless something breaks).

There are 3 main functions for controlling idle and all they basically do is table lookup (I think I may have even posted them at one time). There are barely any calculations taking place (same thing with MY96+ 993 ECU idle routines). So I can't really think of any reasons why I'd want to rewrite them.

There are maps for controlling that (and I modified them) but you still need to raise the RPM point that fuel is turned back on. One won't work (to cure the stall) without the other.

Lorenfb

"There are maps for controlling that (and I modified them) but you still need to raise the RPM point that fuel is turned back on. One won't work (to cure the stall) without the other."

So, if each must try a different EPROM for each different car, then there's no real general
solution and raising the fuel shut-off isn't the "fix all".

"There are 3 main functions for controlling idle and all they basically do is table lookup (I think I may have even posted them at one time)."

Then, as I said, the idle algorithm needs to be re-written to properly solve the problem.
The idle system operates as a servo system, i.e. it has feedback, thus the algorithm can
"know" the real time RPM and its rate of change, e.g. adding "waits" before the idle
duty cycle is changed as the RPM de-accels.

Red rooster

The relevant ignition timing maps are a major function in the overrun idle equation. Altering the reverse slopes etc will seriously contribute to a universal fix .
No code rewrites are required.

Geoff

Lorenfb

"The relevant ignition timing maps are a major function in the overrun idle equation."

Where did this come from? Hopefully it's from not from the VERY basic approach VW
used in the early '80s to control the idle, i.e. They advanced/retarded the ignition
timing to stabilize the idle.

The solution is proper control of the idle valve during de-accel.
Case in point:

1. Disconnect the idle valve connect and fix the position of the valve
so it's fully open. Start the engine and let it de-accel, no undershoot
of the idle occurs but the idle is too high.
2. Next use a smaller object to fix the idle valve to less of an opening.
Start the engine and let it de-accel, no understood of the idle occurs
but the steady state idle is now less but still too high.
3. Re-iteration of the process indicates control of the idle valve is a viable
and general solution to eliminate idle undershoot and/or stalling.

Therefore, there exists an intermediate idle valve setting/settings (duty cycles)
which will prevent an idle undershoot AND which can then be re-adjusted
for the non-transient conditions and a return to a normal steady state idle.

Red rooster

Loren,
Thanks for the simplistic solution !
Unfortunately the idle valve position on its own is not enough. Resetting the Idle valve dwell/position will help but the other control functions need to be reset .
A quick look through the functions used will reveal all.
All the best

Geoff

Lorenfb

"Unfortunately the idle valve position on its own is not enough"

It's very obvious that with a statement like that, you lack an understanding of how the
idle valve operates & how it can affect the RPMs, especially when the throttle plate is
closed. Try and put a scope on the idle valve signal or better yet drive the valve with
a square wave & see how the RPMs can be changed to values beyond 1000 RPMs.
Hope that's not too simplistic!

I'm sure Jason will find a solution.

Red rooster

Loren,
Simplistic.Have you real life experience in this area ?

Geoff

Chris M.

I had the pleasure of meeting BostonU today and driving his car. This is the first car I've driven with a LWF and the responsiveness is very obvious. The clutch pedal is heavier than mine (both cars have new clutches) and the travel is much shorter. It's very easy to drive and wouldn't be a problem to drive everyday. No stalling issues whatsoever.
Also, the exhaust on this car is awesome. It's a Monty muffler with Dansk cat bypass (secondary deleted) and is louder than my car with secondary bypass and open airbox but very reasonable inside the car with no resonance. Check out a clip HERE.
It was great to meet you Chris. Hope we can get out on the road again soon.

993inNC

no just the disconnect, may actually go back to 4 wheel. Just did it so I can do some dyno time (no 4 wheel dyno's in town). It has so much more power to the wheels that I tend to break the rear end free MUCH more than I'd like to , so going back to 4 wheel is the only thing that will keep that in check.