borland

I recently purchased and tested one of the FGSSwitch.com First Gear Start modules on my 90' S4. This may not work on your car, but you can buy these modules direct from the web site or on eBay.

The FGSSwitch module works by monitoring the car's speed and automatically energizes the transmission kickdown solenoid valve when the vehicle speed starts or drops below the programmable speed setting.

This product was developed for Mercedes cars utilizing the 722.3 four-speed transmission; the same transmission that the Porsche developed for our later 928s.

If your GTS or S4 starts in first gear with the kickdown solenoid energized (by using a throttle Kickdown Switch Modification), then you might want to consider one of these units installed on your car. Before considering buying the unit, however you should first confirm your car will start in first gear with solenoid being energized.

I have no knowledge of any 928 that has one of the FGSSwitch.com modules installed.

I must say that my 90' S4 automatic doesn’t start in first gear with the kickdown solenoid energized, so this unit doesn't work as intended on my car. I can place the selector in position '2', and the car will start in first gear. I can also press down hard on the throttle and it will kickdown to first gear, but that's the way it works without the module installed. I didn't want to tighten the bowden cable, as I felt it is already properly adjusted. So, until I can find a valve body way to make this happen with slow throttle, I'm going to pass on installing the module on my car. I already have the GTS dynamic kickdown modification installed.

Here's the link for more information about this product from Ireland:

http://www.fgsswitch.com/english/products_eng.html

Just a warning….my English language e-mail communications with fgsswitch.com were very poor.

The unit works as advertised. All setup programming is done using a PC with Windows OS and its standard RS232 serial port. Once the module is programmed, the unit operates without supervision. The unit also includes a function/feature that records elapsed times for acceleration testing, however I can't see this feature as being very useful.

Here's the basic electrical install. I created these diagrams using MS Paint from the provided with the FGSSwitch.com First Gear Start module user manual.




Here's a more advanced install. Note the added circuit eliminates the solenoid activation during starting or idling in Park or Neutral. The transistor/resistor/diodes is my own design, so something else could be improvised.




I did my module testing using test leads, so nothing was permanently wired for my tests. I didn't even use the coaxial cable, just a insulated wire to the speed sensor circuit.

Here's some model specific electrical connection options that I mapped out.

Connection Points, 1990-1995 Porsche 928 GTS/S4 (USA)
1. Power +12V (Pink Wire)
CE panel connector ‘O’ (pin 23 Black/Violet) {from ignition switched power bus 15 }
2. Solenoid Activation (Blue Wire)
CE panel connector “N” (pin 23 Gray/Brown)
3. Vehicle Speed Signal – (Coax Connector)
a. Speedometer ‘A’ Digital Output
CE panel connector N (pin 25, Black/Red)
b. Differential speed sensor (1990 model only)
Rear harness at connector T19 (pin 4 Brown/Red)
c. ABS
not advised
4. FGSSwitch Winter Mode (Purple Wire)
Transistor Switch with +12V & diode split inputs:
‘3’ Selector - Rear harnesss at connector T19 (pin 15, White)
‘D’ Selector - Rear harness at connector T19 (pin 17, Black/White)
5. Ground
Ground terminal behind/above CE panel


Connection Points, 1989 Porsche 928 S4 (USA)
1. Power +12V (Pink Wire)
CE panel connector ‘B’ (pin 14 Black/Violet) {from ignition switched power bus 15 }
2. Solenoid Activation (Blue Wire)
CE panel connector “G” (pin 25 Gray/Brown)
3. Vehicle Speed Signal – (Coax Connector)
a. Speedometer ‘A’ Digital Output
CE panel connector L (pin 25, Black/Red)
b. Differential speed sensor
Rear harness at connector T19 (pin 4 Brown/Red)
4. FGSSwitch Winter Mode (Purple Wire)
Transistor Switch with +12V & diode split inputs:
‘3’ Selector - CE Panel connector 'L' (pin 11, White)
‘D’ Selector - CE Panel connector 'L' (pin 12, Black)
5. Ground
Ground terminal behind/above CE panel

Connection Points, 1987-1998 Porsche 928 S4 (USA)
1. Power +12V (Pink Wire)
CE panel connector ‘B’ (pin 14 Black/Violet) {from ignition switched power bus 15 }
2. Solenoid Activation (Blue Wire)
CE panel connector “G” (pin 25 Gray/Brown)
3. Vehicle Speed Signal – (Coax Connector)
Differential speed sensor
Connector T19 (pin 4 Brown/Red)
4. FGSSwitch Winter Mode (Purple Wire)
Transistor Switch with +12V & diode split inputs:
‘3’ Selector - T27 under Instrument Cluster (pin 1, White)
‘D’ Selector - T27 under Instrument Cluster (pin 3, Black)
5. Ground
Ground terminal behind/above CE panel

Here's a couple photos of connector T19. I disconnected the battery and removed the LH and EZK controllers to gain access to it.










Diagram showing the labeling of the connectors 'N' and 'O'.




On the setup software….I used my laptop with it's USB port and a USB/RS232 adapter configured as COM9. That worked well. You configure tires size and pulse rate.

The pulse rate setting for our 928 is '8' because Porsche installed 8 magnets on the differential carrier which gives 8 pulses per rear wheel rotation. If you were to use ABS as a speed sensor, then the setting would be 45 pulses. This is different than on the Mercedes cars, which have their speed sensor at the transmission, and use a calibrator based on the differential final drive ratio; so for the Mercedes there is a calculation that needs to be done which accommodates the final drive ratio.

The speed parameter slider only goes to 12 mph, however there's a workaround, you can double the pulse rate setting to 16 and the speeds will then double to 24 mph or double what's shown.

AO

Wow. That seems like a lot of work. I simply put mine in the gear I want then mash the gas. Mine even goes to 5.


Actually, Borland, I could see us using this for other things like possibly traction control, launch control... etc. Not sure how to do that, but I'm sure some smart cookie might be able to figure it out.

SMTCapeCod

More on first gear starts,taken from a benz forum:

MB-EXOTENFORUM - Sonderkarossen/Umbauten/Tuning

W126 722.3 First Gear Start
antworten

» I don't speak German, but does anyone know of instructions to modify these
» transmissions to have first gear start. I know about shifting into 2 and
» then back to D.
»
» Thanks
Warren,I think I have it in my PC somewhere. You need the early W126 380 (etc ) trans module. There is a white wire running to the module,you tap into this with a feed from the power side of the kick down switch . It tells the trans to start in first all the time.

Found it!

SMTCapeCod

THis seems pretty smaht, too. COming to a stop..step on the brake..triggers parallel kickdown...start in first...

"Our car started in 2nd and my ex-wife told Steve she would not drive it if it did not start in first.

They took a hot lead off of the brake light and connected it to the same destination as the "kick-down" switch. Whenever the brake was activated the "kick-down" switch was activated. If this occurred while driving the foot was either on the gas OR the brake (unless you use two feet to drive) and the "kick-down" being activated at speed without the throttle engaged was not a problem.

When you came to a stop and stepped on the brake the "lick-down" switch would drop the tranny to 1st. It was a big improvement and the ex drove the car for most of the next 10 years.

It has been well over 20 years since this was done. I was not as involved with MB and DIY and my memory may have some flaws but I'm fairly certain that the hot from the brake and the "kick-down" switch was used. I do not remember if any other components were involved.
"

SMTCapeCod

And a Benz part number..though I don't know the W124/W126 applicability..

"teh only V8 gearbox between 1980 and 1995 to come with first gear start from factory was the 380 engines fitted in the w126.

To achieve first gear start, the MB module can be used (002 545 4132) or an aftermarket one like Bergwerks.

The MB FGS module can be found under the dash on pre 86 w126 cars. Easy to wire up, takes 3 inputs : ground, +12V, speedo pulse and output is +12V to the kickdown wire. First gear is engaged at standstill and upshift is at 7mph unless WOT, where it will stay to redline.

The first gear that is achieved via the 'S' mode is not true first gear start....with that, gearbox is idling in 2nd and 'kicksdown' to first on brisk acceleration. True first gear start is where you actually have the gearbox iding in first. The only way to achieve this is either manually selecting 'B' then back up to D, or have a module do this for you."

dr bob

For those playing along at home, a datapoint: the modules like BergWerks did NOT work on my '89 car. Apparently, pulling in the shift/kickdown solenoid isn't enough on its own to get a first-gear start.

blown 87

Took just a minute for that to soak in, just like the Coke on my laptops key board.

SMTCapeCod

That's helpful. Unfortunately, my wiring diagrams are in Mass and I'm not. I wonder whether the Benz module is compatible with the 928 arrangement? The brake circuit approach in liue of a momentary switch, seems to make sense to me, but some little voice is whispering that there's a drawback that I'm not thinking of.

FredR

Not wishing to knock this sytem or this interesting post in any way, but I am at something of a loss as to why one would perceives a need to make such modifications when we have very simple and effective measures open to us.

Indeed the 928 auto was designed to set off in 2nd but it is an absolutely awful system for anyone vaguely interested in performance. Now admittedly most new owners were invariably [but not exclusively] over weight cigar smoking middle aged [aka between 45 and 65 years of age - the 65 figure is under constant review] business men. My perception is that most of these characters were more image conscious junkees than performance oriented drivers and probably did not give a toss what gear the car started in. As these cars get older they become more and more available to different owner types.

When I purchased my first 928 in late 98 [the 90 S4 that I later lost] I did not really have any options about transmission as there was only 1 manual in this country [my good friend now owns it]. So, if I wanted a 928 it had to be an auto. My first perfomance car was a 3 litre Ford Capri- 3 speed auto- hated it [the gearbox that is]. My second performance car was a BMW 528 with 5 speed manual -loved it. I then moved to the ME in 1990 and had to settle for a company car. After re-establishing myself financially, I then purchased the S4 in late 98. It was Guard's red and it seemingly punched all the right buttons. Horror of horrors within a week of purchase I hated it- because of the auto gearbox. The main problem was the second gear start- urrgh! At that time we had only just had our first internet connection and it took a while before I found Rennlist. When I did achieve this breakthrough some kind soul advised me to tighten the kick down cable by approximately 3 turns. After doing this first gear starts became viable. Changed my perception of the car overnight. When the local service manager drove it his first reaction was "what have you done?". He thought I had made an engine performance modification. Later on folks started talking about kickdown switch mods- fitting a remote engagement switch. I simply cut the cables feedling the switch, fitted a spade connector then played around with the kickdown cable the 2 cents spade connector enabled me to short out the switch at my discretion. I then played around with the kick down cable some more until it reached a point where it could cruise on the highway at 70 mph and accelerate slowly with light throttle pressure but- with a slight dab it would then drop down and go for it. I run my current 928 like this and more to the point, I cannot bear to drive it any other way.

Fair enough, it may not appeal to everyone but it is easy to do, costs nothing and makes the car feel well and truly alive. I can do nothing about the palty 4 ratios but for most day to day scenarios it is adequate.

Knowing what I know and have done for over 10 years, I am left wondering why do anything else? I may be missing the point here but surely this is the optimal solution to this fundamental problem?

regards

Fred