Tech Series: New Wave 1.8T Swap Part IV

In parts one through three of this series, I have outlined why I originally felt the need to try a different approach to swapping a 1.8T engine into an older CE2-equipped Volkswagen. To summarize, I wanted an easier, less-expensive way to go about this swap then was currently available. I think I’ve succeeded.

I’ll be the first to admit I’ve not rewritten any rulebooks here, but then again, that wasn’t really my goal. My actual goal was to provide a new option for those folks not looking forward to dealing with wiring issues themselves, or paying someone else to do it for them.

Current options leave most people needing to purchase the necessary parts, perform complicated (for the average DIY-er) electrical work (or pay someone else to do it for them), install said parts, and then add the expense of a chip if they want more than stock hp numbers. So long as you start with a qualified candidate, my technique will avoid the complicated wiring aspects and the included chip will all at once provide beyond-stock horsepower. I would also expect that this technique will ultimately prove less expensive than more traditional methods, even though some additional parts such as the aforementioned chip, up-rated injectors and a boost controller are necessary. But even if for some people my technique does not save a great deal of cash, I firmly believe that the prospect of not having to integrate a non-modular MkIV wiring harness, ECU, immobilizer, cluster, etc. will be attractive enough to make this technique a viable one.

Up to now I’ve been having a little fun hiding the aspect of my swap technique that makes it all unique, but the truth is that what I came up with is surprisingly simple: I hung a distributor on the end of the cylinder head in place of the stock 1.8T camshaft position sensor.

As I was thinking about how exactly I was going to build my car, and knowing I was looking to avoid altogether the wiring nightmares I’ve seen so many other people go through, my logical thought process was this:

Q: Why can’t we just run the 20v motor with the Mk3 8v ECU?

A: Because there’s no way to fire the coil packs.

So, I took the coil packs out of the equation… and determined (obviously) that we needed another way to fire the plugs.

Q: Why do we need coil packs when the rest of the earlier 4-cylinder engines don’t use them?

A: There is no provision for a distributor on most 1.8Ts – only a camshaft reference sensor on the end of the intake camshaft that helps time the coil packs.

Hmmm. Well, the camshaft reference sensor for the Mk3 is in the distributor on the 2.0 cars, and that setup works just fine to fire the 2.0 plugs – why wouldn’t it work with the 1.8T?

Q: Would the ECU know the difference if all 2.0 sensors, including the distributor, were transferred to the 1.8T motor?

A: No, it wouldn’t – it would think it’s running a stock 2.0.

Q: What about the timing/fuel curves – would the stock 2.0 ECU maps run the 1.8T motor, especially under boost?

A: No, the maps would need to be completely different. However, C2 Motorsports has no trouble changing them, and after talking with owners Chris and Jeff, they said tuning wouldn’t be an issue for them, and that since we’re talking about a Mk3 2.0 ECU, the cost would be less than for a 1.8T ECU.

So I took a look at putting a Mk3 distributor in place of the stock 1.8T camshaft position sensor. I have a full machine shop at my disposal, so I did some dissecting, took a few measurements, and hit my lathe. It took a few tries to get everything just right, but eventually I did. I ended up making an adapter that on one end bolts to the head in the original camshaft reference position sensor bolt holes (so I didn’t have to modify the head at all), and on the other end, the stock Mk3 distributor bolts right in, and even uses the original distributor hold down clamp. The gear on the end of the distributor obviously had to be taken off because there was no counter gear to turn it, so I machined up a piece that pins onto the distributor shaft like the original gear, and lines up perfectly with the end of the camshaft.

Now I had a way to fire the plugs with the stock Mk3 2.0 ECU. All the other 2.0 sensors were direct fits onto the 1.8T, including the knock sensor, throttle body, etc. I made a plug-in extension for the MAF wiring so it could sit in the proper place in front of the turbo, and a longer coil wire so I didn’t have to relocate the MK3 ignition coil. I had to use a set of Mk2 16v plug wires because the original 8v wires were too short now due to the distributor relocation, but everything else was fine. Even the Mk3 oxygen sensors fit right into the stock Mk4 downpipe and plugged right into the original location. It really worked out well.

Once I had everything transferred to the 1.8T from the 2.0, including the distributor, I installed a chip that had been modified with a projected air/fuel curve that would hopefully be “safe” for my brand new motor. With everything now complete, it was time to turn the key and see what happened. I connected the battery and adapted the throttle body, then turned the key…

It fired first shot, and idled perfectly.

Now that I had a running 1.8T swap car, I rapidly turned it into a driving 1.8T swap car. I tied up a few loose ends, and took it for a rip. I decided to keep it at 5-lbs of boost while breaking in the motor, and also because I didn’t want to run the risk of running lean and blowing up my new motor. The maps I was running on ended up being a bit leaner than I liked, but I wasn’t detonating, so I decided not to worry about it until I wanted to turn up the boost. I left increasing the boost to Jeff when he had the car and was tuning it for real.

Even with such a base state of tune, the car runs beautifully. Full and part throttle drivability are very OE-like, and the car feels strong. As mentioned, the next step is to get C2 to program for me a chip more specific to this car and project and from there we’ll also set out to see just how much boost and power this technique can deliver. Also, if demand is there, I’d like to explore working with C2 to provide programming for OBD1 2.0 systems, as well as Digifant and CIS Motronic. I think you’ll agree it sure would be nice for owners of those vehicles to be able to bolt in a 1.8T with proper accessories, connect to their factory main harness, plug in an old-fashioned eprom, and drive off into the sunset. (Okay, it could never that easy, but you get my point…)

As for who can benefit from this kind of swap technique, I’ll allow that for now it is those owners with OBD2 Mk3 2.0 vehicles. But as mentioned, I do believe it’s just a matter of time and demand before a version is available for the vehicles listed above – basically, any car with a “chip-able” ECU. Keep in mind I only chose a Mk3 2.0 to test my theories and that I’m very much in the early stages of finding out all the possible applications for this technique and the work involved in getting them to work.

For more information, I’m providing a cursory FAQ list:

Q: What cars with what engines will this swap work on?

A: So far, this will work with any car that has OBD2 Mk3 2.0 management, whether it be an earlier Mk2 that had had the harness swapped in, a stock later model Mk3 2.0, or in my case an MK3 VR6 car that the 2.0 harness was installed in. Other earlier management systems are in the works beginning with OBD1.

Q: Let’s say I have a 1997 2.0 Golf – exactly what parts will I need to make this swap run?

A: To make it run, you’ll need the following from the stock 2.0: Throttle body, distributor, knock sensor, crank speed sensor, coolant temp sensors, intake air temp sensor – basically, everything to do with the stock 2.0 engine management is used. Everything is a direct fit onto the 1.8T, but you’ll need to make a bracket for a throttle cable. Nothing related to the stock 1.8T ECU is used. I also used 42-lb injectors, and a manual boost controller (remember, no N75 now to control boost), and had C2 tune the chip so I wouldn’t melt any pistons. A word of caution: If you decide to try this at home and use the stock 2.0 chip and injectors, you WILL melt pistons and blow your motor because the stock 2.0 maps are completely wrong for this application – it HAS to be custom.

Q: Exactly what, if any, wiring modifications will I need to do?

A: None, everything is plug and play. The only modification is removing the drive gear off of the distributor (which can be a pain) and installing the cam drive adapter.

Q: Is any 1.8T engine a good candidate, or should I look for a specific year/version? Will the distributor work with any 1.8T head and block?

A: Any will work, however, if you’re looking to use all OE pieces, a transverse application is best in my opinion, mainly because there is much less fitting/fabrication involved due to the turbo placement. I would also recommend one with a K03 Sport turbo just because it’s a bit larger and can make more power than the standard K03. I think it’s wise to go for the best bang for the buck right out of the box. You need to also get the accessories that fit the motor you choose… for example, the stock Mk3 2.0 accessories will bolt right up to the AEB block from an earlier Audi A4, but all the later Mk4 Jetta/Golf/New Beetle/TT motors require Mk4 accessories because the Mk3 2.0 stuff doesn’t fit. If you’re willing to look to the aftermarket for a transverse downpipe that will work with the AEB, then such a combo might be your best bet. You’ll have to choose which options work best for your particular swap and budget.

Q: Can I use my stock 020 transmission?

A: You can, but it’s not recommended because they were barely suited to handle the power from the stock 8v in any Mk2 or Mk3, and especially the Mk2 16v. It’s possible to build up the strength of your 020, but other VW transmissions are better suited for high hp applications.

Q: How can a 1.8T just plug into my factory harness?

A: Remember, the harness doesn’t know it’s connected to a 1.8T, it thinks it’s still the stock 2.0 motor because all of the 2.0 sensors, etc. got transferred to the 1.8T. All the sensors and throttle body, etc. fit right onto the 1.8T without any problems.

Q: Will I be able to bolt on a big-ass turbo?

A: Yes, I believe you will, but I cannot confirm this as of yet. I’m currently collecting parts to bolt one on myself so I’ll have the proper maps for the upper boost levels. You can do it now, just don’t go over the highest boost level that I have tuned for or you could have problems.

I will continue to provide VWvortex and its readers further updates on the progress I’m making with my Jetta, and rest assured the next installment will hopefully provide you with dyno charts and other performance-related information. Look for Part V sometime after Waterfest.

Part 1 through 3 of this series can be found here:

New Wave 1.8T Swap Part I

New Wave 1.8T Swap Part II

New Wave 1.8T Swap Part III

For more discussion on this story, click on the link to our discussion forums at the left.