Is the ko4 Turbo upgrade worth it for your 1.8T?

The ko4 turbo tuning applications

The ko4 turbo upgrade can be applied to a wide range of Volkswagen and Audi models, but you really need to know if ” bang for the buck” it is worth it. What I mean here is; what kind of investment is needed per every Hp you will get. As I always say, there is no better investment for starters than a properly developed performance software. Let me explain! Let’s take a 1.8T engine for the sake of this example. Installing a performance software will give you an extra 50hp on your 1.8T engine and let’s say you spend $600 with installation for this software. So your cost per horsepower is $600 divided by 50hp = $12/hp which is a total deal.

New Genuine Turbo Exact Fit Turbocharger for 1997-2006 Volkswagen Passat & AUDI A4 Quattro…

Let’s continue with this example. Imagine you wanted to get a full length 3″ stainless steel exhaust including a downpipe, a cold air intake and a performance software to complement these modifications. These tuning options would cost you more or less $2500 and you would gain about 65 horsepower. If we do our little calculation, we get $38/hp. It starts to get more expensive. Keep in mind that I didn’t calculate the cost of installation, but rather only the cost of the parts. Let’s keep going on to the next level of Tuning.

The Ko4 Turbo Kit for the 1.8T Mk4

Bringing your car to 265hp and 300lbs or torque may sound like fun and in the same time please take the time to consider the following. In order to get to that level of performance, you will need the ko4 turbo kit, Audi TT225 OEM injectors, at least a 3″ downpipe (Full length 3″ exhaust recommended), the Audi TT225 MAF housing (use your original MAF sensor), a cold air intake, an aftermarket diverter valve and some minor shop hardware. Some may forget, but you will also need to do some transmission work in order to hold this power together. Once you are done, your car will definitely be fast and fun to drive and you would have spent about $5000 with a ratio of about $58/hp. Once again, the cost of installation is not included in the price. Also, I recommend getting a front mount intercooler which I didn’t include in the price.

BILLET KO4-015xl K04-015xl Upgraded K03 Turbo VW Passat Audi A4 1.8T 2yr wrnty

What I think is a much better option “bang for the buck” and to also have a super fast car, is the following. Get yourself a GT28rs turbo kit also called the eliminator kit or the disk potato turbo. You will also need the following:

1- 440cc injectors or the Bosch Green Giant 415cc Injectors
2- Audi TT225 MAF Housing (some tuning companies offer Mafless software)
3- Cold air intake
4- Iron cast Exhaust Manifold for the 1.8T engine (Longitudinal and transverse options are available)
5- 3.5bar Fuel Pressure Regulator
6- Full length 3″ Exhaust with downpipe if not included in the turbo kit
7- Upgraded Front Mount intercooler kit (don’t get the side mount intercoolers, they are not efficient enough)
8- Upgraded Diverter valve
9- Shop Hardware
8- Clutch/Flywheel/pressure plate

This setup, without installation will cost you about $6500 and will bring your car all the way up to 350hp. That’s a massive 170hp gain from its stock 180 hp mark! And once we do our little ratio analysis, we end up with $38/hp which is a bargain for this huge power upgrade. It is actually cheaper per HP to do the Gt28rs turbo upgrade than the Ko4 turbo kit. Please keep in mind that installation cost may vary in price, this is why didn’t included it in our evaluation.

A question that comes up pretty often, is weather or not to rebuild the engine when doing the GT28rs turbo upgrade. And my answer is this; you don’t have to rebuild the engine or put rods at all if you make sure to run 20psi of boost or less. I do recommend it for long term durability and if you choose to do it, you only need to get a good set of H-Beam Rods that are good for 400Hp+. I also noticed that installing a limited slip differential made the car much more drivable, so if you have the extra cash, get one installed.

If you have more coins and want the ultimate 1.8T setup then you can go a step further and get the GT3071R with 630cc injectors. I talked about this setup in my other article called “The Volkswagen Mk4 Obsession” Go and check it out if you are interested, otherwise the GT28rs is not only economical but will turn your car into a ragging beast.

All these tuning options do apply to your Audi A4 as well. Some may consider an audi a4 turbo kit and once again, I think that your best option is either a simple software upgrade of the GT28rs setup. If you are on a budget, you can also choose to go progressively which at the end will cost you more money but will allow you to get the intake, the exhaust and all the other small modifications before dropping in the big turbo or the ko4 turbo.

For those of you that still want to get a ko4 Turbo kit, I do believe it is a safe and reliable choice. It allows you to keep your car looking OEM and gives you that huge increase in power out of your Volks or Audi while avoiding going into larger modifications.

Why Should you choose the Borg Warner Ko4 Turbo?

I had the opportunity to test and try a wide range of ko4 turbo’s and the best ko4 turbo specs and results are and have always been until today with the Borg Warner Ko4 Turbo. They are properly engineered and design to last a long time even when boosted up. So please save yourself some time and money and avoid the mistakes I made by spending a little extra and getting the Borg Warner Turbo. You will do as you want and if you think that Chinese ko4 turbo’s will do the job, then try it out for yourself and you will soon end up having to change your turbo again. Chinese Ebay turbo’s are not an option if you are serious about your tuning! Just avoid the hassle and go with what was tested and what works!

Small reminder, Audi’s and Volkswagen’s have both 1.8T engine with small variations and different engine bay positioning. When ordering your ko4 turbo kit, you want to make sure your kit is designed for your specific car for proper fitment.

Enjoy your new Beast!

K03 KO3 Turbo Rebuild Kit Turbo Lab America K03 KO3 KO4 K04 Mini Cooper Turbo Rebuild Kit

  • Upgrade 360 Degree Thrust Bearing with 3 Oil Ports
  • Fits Audi A4, A6, S4, Avant,
  • Fits VW 1.8T, VW Passat 1.8T, Jetta 1.8T
Scroll to Top