gc

You might need to check or replace the crank position sensor. First check the connector to make sure there isn't any corrosion, it's one of the two connectors just above the front engine mount bracket. If that doesn't work you might want to replace the sensor, it bolts up to the front of the engine block with a small m6 bolt. I believe that is one of the few signals that the engine management system absolutely must have in order to run. Most of the other sensors have either default values or other solutions so the engine will run but not as well as it would normally. GC

It's my understanding that the vacuum tube was used for the mpg calculations only in the early Corrado model years, at least that's the case here in the US. I believe it was used until some time in the middle of model year 1992 when they went to the fully electronic system I mentioned above. I presume the same applies in Europe. This does raise an interesting possibility I had not considered before, the mpg feature might work if you use the clocks from an early VR6 car that used the vacuum tube system and simply run a vacuum line off the intake manifold. I'll have to see what information if any the Bentley has regarding this system. Presumably if the 24v engine has the same displacement as the original VR6 then the clocks should provide a reasonably good mpg estimate. GC

I'd be interested in finding out how to get the mpg display working on my 24v conversion if possible as well (assuming I ever finish the project). I know that on the VR6 Corrado the ECU sends a signal to the clocks which is used for the mpg calculation. I presume the clocks use this signal and the speed signal to estimate mileage. I'm not exactly sure about the nature of the signal sent by the ECU, whether it is an analog voltage proportional to the fuel flow or if it is a digital pulse at the same frequency as one of the injectors and the clocks have a built in assumption on injector flow rate it uses to infer a fuel flow rate based on the injector pulse width. The early mk IV cars (pre-CAN-BUS) also have a discrete wire from the ECU to the clocks for the mileage information (terminal 81 on the 121 pin connector at the ECU according to my Bentley manuals). That terminal on the ECU connector is not used on the CAN-BUS enabled engines. I have been trying to find out if the ECU still outputs an appropriate signal to that terminal and it's just not used on the CAN-BUS cars. I have inquired about this with a company here in the US that does mk IV tuning programs but have not received any response. Perhaps one of the tuning companies in the UK knows the answer. If one of you has any contacts at a tuning company and could find out, I'd appreciate it. I'm not sure if any of this would apply to a mk V based swap. GC

I'm not sure that the 12v brackets would fit on the 24v block. The top of the 12v alternator and ac compressor bracket interferes with the intake manifold of the 24v engine. I also seem to remember that some of the mounting bosses on the 24 block and brackets are shifted relative to where they are on the equivalent 12v component. Progress on my swap has been glacial so my memory of the details from when I tried this could be incorrect. If someone has actually made it work I would appreciate seeing the details. GC

I'm not certain but I assume that the 4motion bracket and the FWD bracket are the same, in which case the AC compressor will interfere with the front cross member. Most of the solutions I have seen involve cutting out a section of the cross member and then reinforcing it with thicker plates on the bottom. The most innovative solution I have seen and probably the one that I will try and copy for my conversion is to use spacers to lower the cross member. I found this on a thread about converting a mk3 to a 24v engine. The mk3 cross member design is slightly different but I think the basic idea would still work. Here's a link to that thread: http://www.vask.org.nz/index.php/topic,5877.165.html GC

Not sure about using the mkIII air-conditioning parts but you will have to modify the front cross member to be able to fit the air conditioning compressor with the 24v engine as it sits further away from the engine block than on a 12v.

There may not be an existing wire that emerges from pin 9 on the orange connector depending on build date and options. According to the Bentley diagrams, cars that were built after April 2002 do not use this wire to provide the clocks with the RPM signal and so this wire isn't there on the passenger compartment side of the harness. This is the case with my harness so I'm going to run my own wire from the connector to the Corrado fuse box. The exception is if the car had the climatronic system in which case there would be a green and brown wire from terminal 9 to the climatronic control unit. GC

Based on the 93 SLC diagram I've been using to research my conversion, I think you need to run a wire from terminal 9 on the orange 10 pin connector of the mk IV harness to terminal 12 of the G1 connector on the Corrado fuse box. This should essentially replicate the way the rpm signal gets to the Corrado clocks with the stock 12V system. Connector G1 should be the 12 point white connector with the alignment pin on the edge of the connector. Have any of you attempted to do a hybrid Corrado/mkIV set of clocks? Specifically keep the Corrado speedometer, tachometer, and fuel/coolant temperature gauges but replace the Corrado LED display with the mkIV displays. I am currently planning on keeping the bare circuit board from the mkIV clocks so I can retain the immobilizer feature. Since the board is there it seems like it should be possible to place the LCD display from the mkIV cluster in the Corrado cluster and run some wires between the circuit board and the LCD to allow it to work. This would then keep some of the convenience features (mileage tracking etc...) that would otherwise be lost when the 12V system is removed. I'm curious to see if anyone has attempted this. GC

Here is a thread on upgrading from the original 3 channel Corrado ABS system to a later 4 channel one from the Passat. It should give you a rough idea of what is involved. http://www.corrado-club.ca/forum/viewtopic.php?t=5943

Thanks, I was afraid recoding the ECU might not work. I'll try and get hold of Custom Codes, but since I'm in the States their software might not work for me.

Have any of you run into issues with the ECU not allowing the engine to go beyond 4000 rpm unless the mkIV ABS module is present? I am in the process of gathering the parts to do this swap and have seen this problem mentioned a few times on VWVortex, (I'm not sure if this is only a problem on US/Canadian versions of the 24v ECU). I was under the impression that the ECU could be recoded so that it assumed that ABS was not an available option using VAG-COM, but have not been able to get anyone to confirm that this works. If anyone knows anything about this I'd greatly appreciate the help.

Check out this web site it might help with installing a switch in the console. http://www.gti-vr6.net/wiki/index.php?t ... to_console