K03 Hybrids from GP Turbos

June 17, 2018 Jeffrey Jones

A discussion on the AudiSRS forum posed a question about experience with a set of K03 Hybrid turbochargers from GP Turbos in the UK. The product is not shown on the page of the GP Turbos website dedicated to the Audi product line, but there was a link to an eBay listing provided in the discussion with the title “Audi S4 RS4 B5 2.7 T GTX Billet hybrid 385+bhp Pair Turbos 5316 970 0016 / 0017”.

Curious to learn more about the product, as nothing had been provided in the forum discussion I sent an inquiry to the email address given on the Contact Us page of the GP Turbos website.

After about a week I had not heard a reply so I used the contact form on the same page to send my question again, but I also noticed the Facebook symbol on this page so I followed that to see if I could send a Message via Facebook to the company. This was a possibility, so I sent a message through the Facebook messenger.

After two days I had not heard a reply back to my question from the contact form but I did get a response back via Facebook. My question to learn some more about the K03 Hybrid for 2.7T engine was responded with, “What information do you require”.

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I sent a reply back with a series of questions;

“If I understand the advertisement, these are rebuilt BorgWarner K03’s with the compressor housing machined to accept a larger compressor wheel. Are the wastegate canisters new K03 units or does it use the existing ones from the rebuilt turbo? What size is the compressor wheel? Stock is 36/50. The ad mentions they are high flow compressor wheels, what is the maximum lb/min that they support? The trimming of the turbine shaft, what is the purpose? Load carrying capacity was not reduced with the removal of material? Is the turbine wheel the original K03 design? The ad mentions these have great spool and response, do you have any boost data to illustrate how these compare with an unmodified K03? To what speed are the turbo’s balanced? The ad mentions that No Returns Accepted, does that mean there is no warranty period on the product? Thank you”

My questions were viewed about half a day later but no response came back after more than a day passed.

With idle time I decided to see what I could dig up on GP Turbos. I first looked into the domain name, GP Turbos.com and found that it was created in August of 2017, only 10 months ago, a mark against the business.

I then looked into the business registry data to see what I could find. There was a record of the company incorporating in 2013, a positive sign, but then for two years from 2014 to the end of 2016 there are “Accounts for a dormant company” – that doesn’t seem good. Then in November of 2017 there are a series of changes noted. As a reminder, this is now a couple of months after the internet domain name was registered.

The eBay account selling the K03 Hybrids is for “gti1000bhp” and was established in 2005. It is not listed as being for a business seller.

The Facebook page for GP Turbos first mentions the K03 Hybrid for the 2.7T engine in January of 2018. Aside from the one post the product is never mentioned again.

Based upon what I have found thus far it appears to me that GP Turbos was started several years ago doing something that never panned out or was not done seriously, and then last year a renewed effort began. The website was developed and they appear to be using the owner’s personal eBay account to also sell the products. The company is likely producing the K03 Hybrids for the B5 S4 and never tested them on an S4.

Turning to the product, what do I know about it? Not a whole lot. According to the GP Turbos eBay listing their product has the following features:

GTX Billet compressor wheels.
High flow compressor wheel
Capable of up to 385+bhp
Great spool and response
Upgraded bearings

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After several days I received a reply back to my series of questions:

Q. Are the wastegate canisters new K03 units or does it use the existing ones from the rebuilt turbo?

A. The Actuators are tested existing ones from the rebuilt turbos, these are optimized and setup 2 psi above standard

Q. What size is the compressor wheel? Stock is 36/50.

A. The compressor wheel is 38/51 billet design

Q. What is the maximum lb/min that they support?

A. They flow approx 26lb/min

Q. The trimming of the turbine shaft, what is the purpose? Load carrying capacity was not reduced with the removal of material?

A. Turbine wheel has had trim to increase maximum flow while maintaining most of low down efficiency

Q. Is the turbine wheel the original K03 design?

These are new slightly thicker blade but original design based wheels

Q. The ad mentions these have great spool and response, do you have any boost data to illustrate how these compare with an unmodified K03?

A. Unanswered

Q. To what speed are the turbo’s balanced?

A. All assemblies are dynamically balanced to Motorsport specifications to within 5mg

Q. The ad mentions that No Returns Accepted, does that mean there is no warranty period on the product?

A. Warranty is 6 months as they are motorsport items

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I now feel more strongly that these turbochargers were not tested on a B5 S4. There is an absence of data on the company website, the eBay listing, the company Facebook page announcing the product, and my question about having data was the only question that was not answered.

The question any end user ought to be asking, “what change in performance am I purchasing with a product?” remains a mystery.

Upgrade Work

XS-Power, Not Impressed

June 16, 2018 Jeffrey Jones

The Silver B5 S4 that I’ve been working on, referred to as “pig pen” on account of the extensive covering of sandy oil that nearly every surface in and around the engine compartment has, arrived with a few new parts to be installed from XS-Power.

Audi B5 S4 Engine Compartment — “Pig Pen”

Starting off was the XS-Power Diverter Valves. They’re shiny but not confidence inspiring. With the separable components and multiple spring options they struck me as an opportunity for failure compared to the tried and true 710N.

These stayed in the box and a pair of 710N’s went onto the S4.

The next part was the XS-Power bipipe. I had hopes this part would work out, but the fit was not good. With the part not fully seated on the throttle body the pipes were contacting the cam covers.

The separation beneath on the bottom side was greater.

Not only did the pipe not fit against the cam covers, the 3 Bar MAP sensor adapter sleeve would not fit into the hole in the XS-Power bipipe.

There was going to be no playing around to try to bend the pipes to make them work, straight to the classified listings I went in search of a used APR Bipipe. A week later I had an APR bipipe installed and the MAP sensor adapter fit into it as expected – hooray for APR.

XS-Power turbo inlet pipes were next. A quick test fit onto the compressor housing, with o-rings installed, showed that there was a little side to side play in the pipe. I saw an intake air leak coming if they were installed as delivered, so out came the saw and off went the ends of the inlet pipes. A silicone adapter was used to join the inlet pipe to the turbocharger.

At the other end I found that if the support bracket was bolted to the valve cover that on the driver side the inlet sat too low, causing the Y-pipe to also sit low. So I did away with the bolt and adjusted the inlet pipe as needed.

While the inlet pipes required some work, they were usable.

The last of the XS-Power parts was the full exhaust. I was pleasantly surprised to find the downpipes fit well, although they are not a full 3″ design but a tapered design so there’s some more room to work with around the transmission mount brackets.

The rest of the exhaust was less pleasant to install. The rear parts of the exhaust pipe slide over each other which is an okay concept but hard to implement. The alignment has to be spot on and there is not a whole lot of overlap available. The outer pipe does not have any relief cuts in it, so the front and back halves fit together very tightly. So tightly that I was afraid to pound them together for fear of not being able to separate them later if needed.

So the exhaust will need more attention, most likely from a shop specializing in exhausts with the tools to make corrections to this system.

Overall I wasn’t particularly impressed with the XS-Power products.

Flow Tests

Silly Rabbit Motorsport and White Dog Racing Intercooler Matchup

June 12, 2018 Jeffrey Jones

As mentioned a few posts back, I have access to a pair of the latest SRM side mount ICs for the B5 S4 along with the White Dog Racing side mount intercooler option for the B5 S4.

Silly Rabbit Motorsport and White Dog Racing Side Mount Intercoolers

Yesterday I took the opportunity to measure the Silly Rabbit Motorsport IC on the flowbench. Before taking similar flow measurements on the White Dog Racing side mount ICs I took some dimension measurements of the two products to see how they compare.

The table below summarizes how the specs match up:

Silly Rabbit Motorsport & White Dog Racing IC Specification Matchup

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Deciding upon a standard arrangement to test these two intercoolers with was not entirely straight forward. Each is supplied with a hose kit that differs substantially from the other. The SRM ICs are delivered with a set of silicone hoses and the WDR ICs have a set of metal inlet pipes along with silicone hoses. The silicone hoses between the two vendors differ in shape and length.

Because I had already measured the SRM intercoolers I chose to utilize the SRM hoses with the WDR intercoolers. As the goal was to determine how the intercoolers compared, keeping a standard hose arrangement seemed to be the best way to measure on a level playing field.

The two configurations I chose for comparison were first with the core having no inlet pipe and the SRM hump hose connecting the core to the flow bench.

White Dog Racing Audi B5 S4 Side Mount Intercooler on Flowbench

Then the second setup was with the same silicone hose on the outlet, with the addition of inlet piping. The inlet piping consists of the hose that joins the hard pipe with the turbocharger compressor housing outlet, the hardpipe, and the SRM silicone hose.

Silly Rabbit Motorsport Cast End Tank Intercooler

All tests were done on the driver side intercooler and inlet piping.

Under these standard arrangements the following results were measured:

The White Dog Racing intercooler produced slightly greater airflow in each test case. The gains in each are approximately 4% over the SRM intercooler.

Conclusion:

As mentioned when I first saw the SRM IC with cast end tank, I liked the way the tank had smoother edges than the previous end tanks, but the reduced cross section of the inlet and outlet piping was concerning. It cannot be determined from these tests what design differences led to the outcome, but a reduced cross section into and out of the intercooler versus the competitor is not going to help.

Airflow is an important aspect of intercooler performance, but the device is called a ‘heat exchanger’ for a reason – in the future I plan to assess how well the WDR intercooler cools.

My Audi S4

K03 Hybrids from GP Turbos

XS-Power, Not Impressed

Silly Rabbit Motorsport and White Dog Racing Intercooler Matchup

Audi B5 S4 Information and Testing