The ALH engine is regarded as one of the best diesel engines that Volkswagen has put out. This engine was in production from 1999-2006 and was found in the New Beetle, MK4 Jetta, MK4 Jetta Wagon, and MK4 Golf. They put down 90hp and 155lb-ft of torque. Although this doesn’t seem like a lot, vehicles with the ALH were quite quick and got great gas mileage, and weighed less than 3,000 pounds. This engine came with two transmission options: a 4-speed automatic and a more reliable five-speed manual. The aftermarket industry for the 1.9TDI ALH is thriving so much so that mods are pretty affordable.
5 Best 1.9TDI ALH Performance Mods
- Injector Nozzles
1. Upgraded ALH Injector Nozzles
The factory injector nozzles for the ALH, like many other factory parts, are extremely restrictive limiting the fuel delivered to an engine. A simple injector nozzle upgrade can increase power by 15-20hp. Injectors inject fuel directly into the engine where combustion is then created. The more fuel that goes into the engine, the more power that is created. Therefore, getting larger nozzles will pump more fuel into the engine. As you may have guessed there are many different options to choose from.
We advise going with the Bosio DLC 1019 and then make sure to get an injector calibration service to ensure the most ideal performance and efficiency from the upgraded nozzles. These nozzles support power outputs of 120-190hp with the correct supporting mods. However, if you are an enthusiast that is trying to push for 200hp or more, the DLC Race 520 nozzles are the way to go.
2. 1.9 TDI ALH Flash Tuning
A tune and nozzle upgrades will provide the biggest bang for your buck when you are upgrading an ALH engine. A factory tune is designed for comfort, efficiency, and everyday drivers. An aftermarket tune, without upgraded nozzles, can add up to 30hp alone. On top of increased performance, an ECU reprogram can increase fuel efficiency, and provide a better running engine in general.
Again, there are many tuning companies out there, but Kerma provides custom tuning with their easy-to-use Q-Pro+ Flash Programmer for only $549. The tune stores the factory tune and up to two different modified tunes. The Q-Pro+ connects straight into the diagnostic port to communicate with the ECU.
3. Clutch & Flywheel Kit
A reliable clutch is crucial for an engine to use the power it has. Once upgrades start piling up on the 1.9TDI, the factory clutch will start to slip. The factory clutch was not built to withhold up to 100hp. A clutch connects the shaft coming from the engine to the shaft that turns the wheels. What does it mean when a clutch slips? Essentially it is when the clutch engages then disengages resulting in no power being delivered to the wheels and the car not moving. This can be the most annoying thing, especially when people spend a lot of money on mods and the clutch doesn’t support it.
Sachs G60/VR6 Clutch & Flywheel Kit is what we suggest for a moderate clutch upgrade if you aren’t trying to go crazy with the upgrades, like adding a bigger turbo. This setup is rated for 300lb-ft of torque. If you are looking to get a bigger turbo, we would suggest looking into the Silent Design South Bend Clutch Stage 2 Endurance (5-speed) with 22lb Single Mass Flywheel as it will hold a minimum of 350lb-ft of torque.
Sachs Price: $314.95 (New)
South Bend Price: $813 (New)
4. TDI ALH Mufflerectomy
You may be reading this and wondering what the heck is “mufflerectomy”. Essentially “mufflerectomy” means is removing the muffler from the exhaust of the 1.9tdi ALH engine. Now, this is not something that has to be done because the performance benefits may not warrant it, but the sound will. If you’re like us, you want people to turn heads when you drive by. If you are in a state or country that takes emissions seriously, this is not recommended.
There are many options when it comes to this. Most of the time people will just remove the muffler and straight pipe it from there. However, we like to go with tried and true aftermarket mods, like the KermaTDI 2.5″ TBE (Turbo-back exhaust) system. We think this warrants a video clip, so we linked one below!
Bonus Mods for the Ones Who Want More
This is where the real power comes from, but this is also is where more money is spent and engine reliability decreases.
5. Upgraded Turbo
The factory turbo on the 1.9tdi ALH is a VNT-15 that puts out 90hp and 155lb-ft of torque as listed above. If you are wanting to get more boost and more power in general, you’ll have to upgrade the turbo. There are many turbos to choose from, but from scrolling, it looks like the most popular was the 17/22 turbo. However, from the looks of it, this turbo has been discontinued. Kerma found a substitute that is actually better than the 17/22, and it’s the VNT17+ or 17plus.
The 17+ increases compressor burst resistance, allows higher shaft speeds, and runs up to 25psi reliably. Something worth mentioning is if you choose to go the upgraded turbo route, you will want to upgrade your cams, turbo inlet pipe, and intercooler to run this setup as efficiently as possible.
6. Upgraded MAP Sensor
This may seem like an unnecessary mod, but believe us you will want to do it. The factory 2.5-bar MAP sensor only allows up to 18psi of boost. If you purchase the above turbo, that’s 7psi of boost you’re missing out on. The sensor provides intake manifold pressure info to the engine. This process determines how much fuel is required for perfect combustion. An upgraded 4-bar, or even 3-bar, MAP sensor is a MUST to get the most out of your turbo. The 3-bar will hold about 23psi of boost, while the 4-bar will more than that. Since it is a relatively inexpensive part and it’s easy to put on, why not.
Conclusion – 1.9TDI ALH Mods
To conclude this mod guide, the Volkswagen 1.9TDI ALH engine is one of the most reliable diesel engines to date. If you are just looking for a little more zip out of the engine at a relatively low cost, go with upgraded nozzles, tune, and an upgraded clutch. However, if you are looking to go 150hp+, you’ll have to do upgraded nozzles, tune, clutch, turbo, and MAP sensor. Unless you know exactly what you’re doing when DIYing, we would advise taking it to a professional to ensure the engine is running as efficiently as possible.
If you want to read more about the 1.9TDI engine, here is our write-up on The 6 Most Common 1.9TDI Engine Problems.