I am not responsible for any damage that could occur to your pump, engine and car before, during and after this modification.
There's a lot more to IDI tuning that this. I suggest you educate yourself about IDI engines before you do any mods to your pump/engine.
Ah the infamous governor mod! IDI's achilles' heel. It's amazing how such a simple (relatively speaking) procedure can yield such impressive results.
What does it do and how it works
The governor is used to control RPMs and fuel delivery. When reaching full throttle, fuel gradually cut by 80% and RPM limited to about 5500. Modding the governor means a LOT more fuel in most of the RPM range and higher revs (some people have taken their 1.6 to 6000 and more).
The governor is a simple device. Three springs and a cage. There's the Idle, intermediate and main spring. When you rotate the throttle on the IP, the governor pulls on a lever inside the pump. This lever increases RPM and fueling to a certain point. That certain point is determined by the governor. I stretches when pulled. Once the throttle reaches the stop screw, the governor has stretched enough to cut fuel by 80%.
Starting from the left: Idle (small), intermediate (medium) and main (long) spring. The shaft on the right is the throttle shaft.
How the mod works
The mod will prevent the governor from stretching by replacing the intermediate spring with something solid and shimming or replacing the main spring. I chose the remove the intermediate and shim the main spring. The small idle spring is left UNTOUCHED.
This is what it will look like when modded. The intermediate spring was replaced with three thin washers and the main spring was shimmed with a thin washer and a thick one.
What you need to know
The engine should be in top shape and correctly timed.
First and foremost, increasing fueling will yield higher EGT (exhaust gas temp). An EGT gauge is highly recommended. To use this fuel, you'll need to up the boost. Blocking the BOV on the intake, installing a manual boost controller and adding a boost gauge is necessary.
Second, to keep EGTs down you'll want an intercooler. Ebay is a great source for cheap coolers, aluminum tubing and silicone couplers. If you're doing this to a NA engine, water injection might be something to look into.
Third, the stock exhaust simply won't cut it. 2.5" front to back is a good size. Straight pipe (no mufflers) is ok, it shouldn't be too loud.
Fourth, headgasket. Since you'll be upping the boost, the stock HG might not last long. If you have to replace it, now would be a good time. Here's a link to the metal HG upgrade for hydrolic 1.6 engines: https://forums.vwvortex.com/zerothread?id=3099455
Fifth, you might want an RPM gauge if you don't have one.
If you can, remove the pump from the engine. It'll make the job a lot easier. Clean the injection pump really good. Brake cleaner works nicely. You don't want crap to fall into the pump, it has very tight tolerances. If you can get your hands on pump rebuilt kit it would be best as you'll have to replace one or two seals. Work in a clean area and lubricate everyting with clean diesel fuel.
This it the test subject. An old seized pump I kept for spare parts. I didn't bother cleaning it since its governor will be installed in a working pump.
Note the position of these springs before disassembly and mark the orientation of the throttle lever.
Unhook the spring from the throttle lever and remove the top 10mm nut. Gently tap the lever and pry it off the shaft. You don't need to separate the two levers like I did.
remove all the springs and their seat from the shaft. Keep them in order (mine will go back from right to left).
There are four allen bolts holding the cover on. One of them is under one of the throttle lever's stop screw. If you can't remove the stop screw easely, unscrew the locking nut halfway. Take the throttle lever's top bolt, thread it on the stop screw and resting it against the locking nut. They should lock together and enable you to move the stop screw. If one of the allen bolt strips, use a bigger torx bit and hammer in in the bolt. You can see the stop screws on the right in this picture.
Once the bolt are off the cover will pop up. Unhook the spring on the left (don't lose it) and gently tap on the throttle shaft to slide it out of the cover.
This is what you'll see when the cover is off. The small spring you unhooked is used by the cold start advance. The rectangular seal on the cover will have to be replaced along with the small rubber o-ring on the throttle shaft. The governor is attached to the throttle shaft.
Grab the governor and rotate it so the notch on the shaft clears the notch on the lever.
Governor removed. You can clearly see the small rubber o-ring you'll have to replace on the throttle shaft.
To disassemble the governor (note that you cannot remove the throttle shaft, it is riveted onto the governor), press on the grey spring seat to compress it and slide it out of its cage.
This is what you end up with. Notice the intermediate spring seats. The gap between the left one and the left EDGE of the right seat need to be filled.
Remove the small circlip using a small flathead screwdriver.
Pull out the idle spring parts and the intermediate spring an seat. Discard the intermediate spring and the larger washer. Slide on your shims, then the spring seat and the idle spring parts. This is what it looks like with the itermediate spring removed.
Remove the small circlip at the other end of the governor. You'll have to slightly compress to main spring to get it off using a small flathead screwdriver. Be careful as the spring and seat could fly out in your face.
Remove the spring seat and the intermediate spring. Use the appropriate washers to shim the spring (pre-loading it) or something that doesn't compress if you plan on completely removing it. When reassembling the intermediate spring, you'll have to compress it to fit the seat and it's circlip onto the shaft. It might be hard to compress due to the shims. Be careful and make sure the circlip is fully engaged into its groove. Here's the governor with all it's shims.
Slide it back into the cage. It'll will be hard to compress to make it fit so take your time and be careful. Make sure it's completely seated and that everything is in its appropriate order.
Reassembly of the pump is the reverse of dissasembly. Clean the governor and the mating sides of the pump and cover. Replace the cover seal and the throttle shaft o-ring. Slide the governor back into place into its notched lever. Lube the inside of the throttle hole on the cover and the throttle lever and o-ring with clean diesel (don't use any kind of grease). Carefully slide the throttle lever into the hole in the cover. Don't force anything. Don't worry if it's not in completely, you can pull on it from the top. Next, hook back the cold start spring to its lever.
Torque down the allen bolts on the cover (don't go crazy, they're steel bolts threading in aluminum). Reassemble the throttle levers making sure they are in the same orientation as before.
Now go out there and have fun with your newly found power. Don't forget, modding is a step by step thing. Don't go out modding every setting on your pump all at the same time. Tune one setting and see what it does then move on to the next.
Modified by Black Smokin' Diesel at 4:29 PM 3-3-2007
Modified by Black Smokin' Diesel at 4:30 PM 3-3-2007
Modified by Black Smokin' Diesel at 4:33 PM 3-3-2007
Modified by Black Smokin' Diesel at 4:38 PM 3-3-2007