Governor mod spring

[Dean Erickson]

New to this fourm but not VW diesel engines. I have been looking at the old posts about the gov mod. There are a few diffrent views on what spring to shim and how much. What is the concensus on which spring to manipulate. From what I have read it's the main spring that needs to be changed or shimed ( the large one). Is there a stronger bosch spring that could just be changed out?  I am working a on a 1985 1.6 TD engine. This is my car a few of you may know me from VWdieselparts.com.

[rabbitman]

I've heard of quite a few people that are unhappy with the gov mod.

IIRC it's the medium spring that gets shimmed, check in the FAQ though I could be wrong .

[maxfax]

I've been very pleased with the gov mod on my N/A....  I kept it fiarly modest though.. Been too long for me to remeber exactly which spring I shimmed, but it wasn't the small idle (?) spring..  At least it wasn;t the second time I tore the top off the pump...

[Rabbit TD]

I don't know about the spring but that sure is a nice looking car you have, it is a Rabbit isn't it

[Dean Erickson]

Yes A 1981 Rabbit I changed to round headlights and put in a 1.6 TD from a 85 Jetta. Just finished painting a few weeks ago. I have to change my clutch it's slipping so I will weight to do the gov mod. I am going to shim the main spring because that is the one the effects the upper rpms. I am also going to call my local Bosch service dept. an see if I can get a stronger spring. Here is a pic when I changed the front to round head lights.

[theman53]

You want to do the main "heavy" spring. I didn't do the intermediate spring, but others have and they say that there is drivability issues with the intermediate spring. I have done the main spring on 2 N/A s and have been very pleased. Not a hard mod, but not easy to compress that spring. I put about 1/4" of washers in mine, but I think you could go more if you wanted. I wouldn't do less than 3/16 or 1/4 though.

[maxfax]

I put about 1/4" of washers in mine, but I think you could go more if you wanted. I wouldn't do less than 3/16 or 1/4 though.

Hmm me thinks I need to try some more washers... I was pretty conservative, I probably just barely have 3/16". Still some noticable improvement though...

[8v-of-fury]

So doing the governor mod.. you are fooling the pump in to thinking it is theoretically spinning faster then it really is
(because that's how it does its junk, is to base fueling on spring compression, which is based on centrifical force. correct?) to make it pump more fuel at an earlier time in the RPM range? is that what is pretty much taking place?

It seems like it is a pretty easy to do mod with pretty good gains from something that anyone can do for practically nothing but a little time eh? I think i will do it on my pump once i get the diesel in there

[vanbcguy]

The "Main" spring is fully extended at all times under "normal" driving, it doesn't start to compress until you spin above 4K RPM.  Once it starts to compress it cuts fueling FAST which is why these cars seem like they hit a wall around 4200 - 4500 or so depending on the particular pump.

Shimming the spring is basically the same thing as using a stiffer spring.  In my mind a stiffer spring would be better, but shims are a heck of a lot easier.  What you are doing is increasing the RPM required to provide enough force to start compressing the spring.  Adding a few washers can push the limit up to over 5000 RPM pretty easily.

The tough part is you can't really "choose" what RPM you want to have the pump cut fueling at unless you have a test bench to do it on!

[8v-of-fury]

The tough part is you can't really "choose" what RPM you want to have the pump cut fueling at unless you have a test bench to do it on!

Add one or two at a time and see what happens no? lol

[maxfax]

And when it blows up, back up one step!

[Rabbit on Roids]

i shimmed my main spring with 2 little nuts that fit on the shaft like a glove. my car spins some hellacious RPMS now. and BLOWS the black smoke. but yea, about a quarter inch of shims/spacers gives great results. and my pump is turned up to where i actually adjust the idle with the fuel screw, so its pretty much turned all the way up. but it was amazing the difference it made. anyone debating on doing this, should definitely do it. way worth the time.

[maxfax]

How thick were those two nuts Rabbit on Roids???   Tryin to get an idea of how far I wanna shim when I get the tiem to tear the top back off my pump...

[Dean Erickson]

Here is what I did for the mod. I put a nut on and compresed the spring. The nut is 5 MM thick. I have the clutch out of the car right now so I will report the results later.

[maxfax]

Hmm...  I need more shims..