The silver S4 got a new fuel filter and fuel pump.
Audi B5 S4 Fuel Filter Swap
Neither of these is a task I enjoy doing, and when the fuel filter started leaking gas after being tightened to the advertised torque I was not happy. Finding that I could not fit a wrench between the banjo fitting and fuel filter had me even more steamed. Unable to find a suitable wrench I had about resigned myself to shopping for a new wrench with a thin body when I thought I might be able to get a good grip on the fuel filter with an oil filter wrench.
That hunch turned out to be a successful idea and the extra little bit of tightening the banjo bolt stopped the gasoline leak.
This car is also receiving a fuel pump upgrade with a ProjectB5 setup. The fuel pump turned into a bit more effort than the “drop-in” name would suggest. For the life of me I could not get the pump holder to engage with the basket. This is the fourth time I have swapped pumps in one of these S4s and the first time I have had a hard time getting the pump in place, other than the first when I had not yet purchased the Schwaben fuel pump removal tool.
After 45 minutes of trying, and cursing, I decided to pull the pump out and try to figure out why the darn thing would not lock in. Comparing it to the recently removed stock unit I noticed that the sock on the bottom of the PB5 pump seemed to to extend a little further than the stock part. I pulled out the calipers to measure and sure enough the PB5 setup extended down 17 mm further than the stock part. While the location makes it hard to be conclusive about the cause, it seems likely that the added length is preventing the fuel pump holder from descending far enough into the basket for the notches to engage properly and hold the pump firmly in place.
The next hurdle was a do-over on my part as I forgot that Audi wires the fuel pump backwards, the RED wire goes to the negative post and the BLACK wire to the positive post. I wired up the normal way and got nothing when I tried to start the car. Out came the pump so I could swap the wires, but happily upon re-installation the car started right up.
The car is on the base tune but is looking pretty good thus far.
The Silver S4 I have worked on has the Brake Booster hose arrangement that joins the Accordion Hose, Intake Manifold, and Brake Booster by a 3-way junction.
Accordion to Brake Booster Lines
The new intake setup consists of the 034 silicone hose to replace the stock accordion hose thus doing away with the grommet that allows for the connection to the accordion hose. Like most places inside the engine compartment space is tight around where this hose is located so that leaving capped off parts is undesirable, as well as a potential source for leaks.
I set about modifying the hose to run direct from the intake manifold to the brake booster connection at the firewall.
Using a knife I removed the connecter that attaches one end of the stock line to the intake manifold, intending to reuse this part. The stock part that connects the line to the brake booster is not a check valve, but one is needed so that boost does not reach the Brake Booster.
The connector that goes to the Accordion Hose is a check valve and it could be re-used, but in this case the car has 150k miles on it and I prefer to put a new check valve in place.
Brake Booster Check Valves
The other part needed for this job is some hose. I felt the best option was this stuff as it consists of an interior rubber lining, a metal mesh wrap, and a fabric covering. Air tight and strong to withstand vacuum.
Brake Booster Hose
The part numbers are:
Brake Booster Check Valve –191611933F (Comes up as a part for a Porsche)
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”.
GP Turbos K03 Hybrid eBay Listing
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”.
“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:
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.
