TiAL 605 Turbo Kit

After having the APR Stage 3 setup for several years I decided to jump onto the TiAL 605 Turbo Kit.  With promises of substantially more horsepower and negligible loss of response as compared to K04’s they sounded like a great upgrade.  This was one of those cases where I soon discovered that the product didn’t quite live up to the hype, despite being a solid product.

The details of the installation are covered here,  while I work on completing this page.

Note: What follows is a compilation of partially completed write-ups that I did in conjunction with installing the TiAL 605 kit.

The Idea:

A full replacement of my APR Stage 3 kit had not been something I had given any serious consideration to until it was suggested that I might be able to sell the kit and receive in exchange sufficient funds to pay for a major revision to my S4’s hardware. I began to keep my eyes open for a ‘want to buy’ listing on various S4 forums and in surprisingly short order I found somebody looking to buy exactly what I was interested in selling.

The TiAL 605 kit had been made available through EPL a short while prior to all of this and was the system I was primarily interested in. I found appealing the cost to performance gains, the responsiveness, as well as the integration with the S4’s stock components.

Simultaneously I began to contact EPL about acquiring a TiAL 605 kit while I provided the prospective buyer of my APR Stage 3 kit specific information about the kit I had. In fairly short order money was changing hands and I was settling on a timeline to remove the APR kit and install the EPL/TiAL kit.

The Plan:

Because I had begun upgrading my car nearly from the moment I drove it from the dealership’s lot I had observed significant development of aftermarket parts over the years. The APR Stg3 kit alone was on my car for five years, and the cars exhaust, suspension, and intercoolers all pre-dated the Stg3 kit. I viewed the move to the EPL/TiAL kit as an opportunity to revisit decisions I had made in prior years and consider alternative components that weren’t available at the time I had made past choices.

This wasn’t going to be a break-the-bank upgrade session where I tried to install the best of everything, my goal would be to make changes where a modest gain could be anticipated, or I could leave the door open to do such an upgrade in the future, being mindful of costs.

The cost component necessitated that this phase of upgrading would be a DIY effort. Paying for an engine pull was not within the budget. Fortunately I had some very savvy local expertise to assist with the project.

The Upgrades:

I had recently replaced my RS4 clutch due to a premature failure, and had chosen to go with a Southbend Stage 3 setup. The clutch is probably near its limit with the TiAL 605 kit. I felt early on that I would need to hold back some from what the TiAL turbochargers were capable of due to other component limitations, and the clutch was one component I was concerned about, but not willing to upgrade any further at this point in time.

With my RS4 fuel pump scheduled to be removed to go out with the APR kit I decided to go with the Bosch 044 Motorsport fuel pump. I figured that if I was going to replace the fuel pump I ought to do so with one that wouldn’t have any problems keeping up the fuel injection system.

The spool-up of the TiAL 605 turbochargers as compared to the BW K04’s was a point of concern for me. The 605’s were advertised as “quick spooling” and “responsive” but I felt it would be wise to have the other components on my car helping to make this quick spool a reality. Because of this I chose some additional modifications that I hoped would help with the TiAL turbochargers producing boost quickly. The first change was to replace my stock exhaust manifolds with the VAST ported & polished exhaust manifolds with a black thermal coating. Hopefully by clearing the exhaust path slightly, and by helping to retain heat within the exhaust gasses prior to reaching the turbine wheel, there would be slightly more energy available for turning the turbocharger.

After the turbochargers I also made a change, replacing the AWE 400 cpi cat downpipes with the Autospeed 200 cpi cat DP’s. Without any solid flow bench testing to consider, this decision was mainly one of faith, that a 200 cpi circular cat will outperform a 400 cpi more traditional shaped catalyst. The fact that I was able to acquire a set of ASP DP’s at a discount and sell my AWE DP’s at a reasonable price made the gamble worth the risk.

Since the motor and transmission were going to be out of the car I decided I would replace a few other components that would be easy to get to and not very costly. The only component that fell into this category that could be considered a performance item was the transmission mounts. I decided to replace the stock units with the 034 Motorsport street density mounts.

The EPL/TiAL kit is designed to function with the stock S4 y-pipe. Having used and measured the RS4 y-pipe that the APR kit comes with, which I was now getting rid of, I was having difficulty believing that going to the markedly smaller stock y-pipe would be a good thing. Measurements that I made of the inlet area versus the combined outlet area showed that the RS4 outlet capacity was almost 20% greater than the inlet. This made me feel that the RS4 y-pipe would not cause any unnecessary flow restriction. On the other hand the S4 y-pipe outlet area was about 12% less than the inlet. I believe this would lead to a greater pressure loss through the y-pipe. So, I decided to pick up an RS4 y-pipe and some appropriate silicone reducer hoses to work in conjunction with the TiAL inlet piping.

Because my S4 is a 2001 model year it has the older intake manifold design. This seemed like a good time to correct that situation by acquiring an intake manifold with the revised design. I also figured while I was at it I might as well pick up a set of phenolic intake manifold spacers. Of the choices available I decided to go with the 034 Motorsport offering which is 5mm in thickness. I chose these over some other offerings that are 10mm in thickness because I was concerned with how much the intake manifold would be raised relative to the APR bipipe and how the connection from the RS4 y-pipe to TiAL inlets would be impacted. I was also not convinced that phenolic spacers do all that they are advertised to, so I wasn’t keen on paying nearly twice the price for the thicker spacers.

What I decided not to change. With an upgrade such as this there are numerous opportunities to make changes to the car and I had decided to draw the line at swapping parts that were reasonably inexpensive, or where I had a like aftermarket part that I could sell to defray the cost of a new component. The most significant components that I left untouched were the intercoolers, cat back exhaust, connecting rods, and water injection system.

Replacing my AWE intercoolers was not something that I would do if I could not accomplish the swap for nearly no additional cost. I don’t believe that under normal operating conditions there is going to be a meaningful performance difference between these IC’s and any other top-performing product. To pay a premium to gain little to no performance did not make sense.

The Supersprint exhaust has been a very satisfying product to own. The stainless steel design has held up very well and the tone remains aggressive yet unobtrusive. During development of APR’s Stage 3 software this car put down very respectable numbers on the dyno, and in FATS comparisons has matched up well against other APR Stg3 cars. While there may be power levels where this exhaust begins to become a limitation for the car, thus far that has not been the case. Since my car serves as a daily driver, keeping it livable is a significant consideration.

EPL and TiAL report that the stock S4 connecting rods are the weak link that limits the horsepower that the 605 kit can produce. Unfortunately connecting rods are expensive, and replacing them is more involved than what I was prepared to do. EPL describes their kit as bolt-on, and my aim was to get the APR kit off, and the EPL/TiAL kit back on as quickly as I could.

Lastly, the Aquamist 2D water injection system that my car uses is no longer the top of the line product as it used to be. It is still a very capable system that in several respects is just as capable as the most recent offerings from Aquamist. I was tempted to replace the system with the new HFS-3 for the failsafe capabilities and added fluid flow rate, but unless I got around to having EPL produce a tune specifically for my car with the water injection running, there was not a good reason to purchase the failsafe capabilities that the HFS-3 has when the 2D functions just about as well in the role that it serves on my car, which is primarily as an added safety buffer.

Collecting Parts:

Bringing all of the parts together for the project was complicated by the fact that there was somebody that needed my APR Stg3 parts to begin their build. I didn’t have the luxury of taking several months to pull things together. I contacted EPL on February 7th to see what components I would need to accompany the 605 kit, along with the availability of the kit. I also made initial contact with VAST about the modified exhaust manifolds. Thus began the initial process to execute the conversion, and what follows hereafter is a daily summary, day referring to days that have passed since the start, of the progress and hurdles.

Click here to go straight to the results section. (I need to complete this still)

Day 2: I contacted Avalon Motorsports about the cost of a new RS4 y-pipe. At close to $800 I decided to forgo the RS4 y-pipe unless I could find a used one at a lower price. I also began discussing the installation with Dave to see if he could lend a hand as well as some tools, such as his engine hoist.

Day 4: Receive word from EPL that TiAL has some turbo’s available and they can ship a kit out immediately. Make initial contact with 034 Motorsport about the Bosch 044 Motorsport drop in fuel pump. Inquire with VAST about the turnaround time on a set of exhaust manifolds.

Day 5: Purchase kit from EPL. Also contact AR Design to find out the cell per inch count of their downpipes, they use 300 cpi metal cats. Contact VAST and order the modified exhaust manifolds.

Day 8: I begin searching for a stock ECU to use with EPL software and VAST estimates one week to have the manifolds ready to ship out.

Day 9: I see a used RS4 y-pipe come up for sale on a forum and my offer to purchase is accepted. EPL notifies me that the TiAL kit has been ordered and will arrive at their shop for wastegate adjustment in a few days. I make an initial inquiry about a set of ASP downpipes that I see listed for sale on a forum. Purchase a used M-box ECU that I plan to use with the EPL software.

Day 10: I begin looking into a silicone hose reducer to join the RS4 y-pipe to the TiAL inlets. The TiAL inlets are designed to work with the stock S4 y-pipe so the hump hoses are too small to join with the larger RS4 y-pipe outlets. Purchase the set of ASP downpipes. Discover that the M-box is chipped with GIAC software so I inquire if anybody with a stock H-box would like to trade their stock ECU for this chipped ECU. Contacted by an interested part and sale is made. EPL receives the TiAL turbochargers, fueling kit parts will be arriving separately later.

Day 12: TiAL turbochargers arrive.


Day 13: Friday, I begin to disassemble my S4 in preparation for removing the engine and turbochargers the following day. Spend about x hours getting it prepared.

Day 14: Begin inquiring about phenolic spacers. Spend all day with Dave removing the engine and then removing the turbochargers, exhaust manifolds, fuel injectors and other small items.

Day 17: EPL receives all components for the fueling kit minus the RS4 accordion hose. Shipment will also include turbo to downpipe gaskets and oil feed line crush washers that the kit oddly does not include. Order a set of phenolic intake manifold spacers and the 034 street density transmission mounts.

Day 19: Contact EPL with a number of questions concerning the fueling kit, notably the absence of a fuel pressure regulator as listed on the kit description, absence of a MAF sensor, only a MAF housing was provided with the kit, discrepancies between the TiAL install guide and what has arrived in the kit, coolant hose length, lack of hose clamps for recirculation hoses,

Day 20: Friday, exhaust manifolds arrive in the afternoon from VAST. Contact Dave and plan to install the turbo’s and reinstall engine the following day. Begin to do a test fit of the turbochargers and discover one step of the installation is to replace the turbine inlet seal rings with new parts, which are not supplied with the kit.

Day 21: Contact Dave to let him know the days events are on hold due to the need for turbine inlet rings. Local Audi dealer does not have them in stock; a local foreign parts specialty store will be able to get them in within 2 days.

Day 23: Contact EPL for further clarification on the installation guide as well as to express my frustration at losing a weekend due to the absence of the inlet rings from the kit.

Day 25: Order the Bosch 044 drop-in fuel pump kit.

Day 27: Friday, begin ramping up for final weekend of project. Install EPL flashing software onto my laptop but cannot locate any flash file for my car. Contact EPL to see about where the file is. Begin installation of turbocharger and discover turbo coolant line banjo bolt will not fit underneath wastegate actuator bar. Contact EPL again, via phone, and they instruct me to remove the retaining clip off the end of the wastegate arm so that the arm can be raised far enough that the bolt can fit. Later in the evening while attaching the oil return line I discover that the bolts supplied with the kit are too short and I cannot attach the return line to the turbo. Drive to Lowes in hope of finding a suitable replacement bolt but am unsuccessful. Decide to cannibalize similar sized bolts from other components that I can replace later. Lose about two hours in the process. Shortly after midnight I have only attached the drivers side turbo but still have the compressor signal and wastegate lines to attach. Finished for the night.

Day 28: Dave arrives and we continue the installation. Shortly after finishing the driver’s side we discover that the passenger side compressor signal port has not been adequately tapped and the connector will not thread. Drive to a hardware store in search of a proper sized tap to try and correct the threading problem. Find a suitable tap and return to continue the install. Dave points out that the oil return line gaskets don’t match up well to the flange but we press on. Break for lunch and contact Johnny Bravo to discuss the issues we’ve encountered thus far. Mention that the driver’s side coolant line is very taught, to the point it is pinched going over a coolant hard pipe. After reviewing my notes and email’s to EPL I realize this was something I noticed upon the kit arrival and brought to EPL’s attention but they had told me that the install guide dimension was incorrect. Realize it will be necessary to remove and replace the driver’s side coolant line with a proper length hose. Drive to an automotive parts store to obtain a replacement coolant hose. Resume the install. Have difficulty plumbing the passenger side compressor signal and wastegate lines. I had anticipated completing the turbocharger install around noon, it took until 7 pm.

Day 32: Replace the timing belt, water pump, and other associated items prior to the upcoming weekend when the motor will hopefully be put back in the car.

Day 34: Friday, compile a checklist of items to accomplish the following day when Dave comes over for the re-install.

Day 35: Dave returns for another go and we spend the day getting the engine back in along with the new fuel injectors and a new slave cylinder and the new tranny mounts. Dave solders the new MAF sensor connector in place as the last item of another long day.

Day 36: Begin putting all of the remaining parts back in place. Bleed the slave cylinder and refill various fluids. By late in the evening I am finally ready to flash the ECU and try starting the car. Connect the laptop and find that the EPL flash file will not load.

Day 37: Monday, contact EPL for help trying to get ECU flashed. I am unsuccessful getting the ECU to flash with my Vag-Com cable so EPL is sending an OBD cable from their shop.

Day 38: Realize while trying to re-install the air intake snorkel that it won’t fit due to interference with the TiAL DV recirculation hose. Bring this point up to EPL and they tell me this is something they are aware of, though not mentioned in the install instructions, and the part has been left off all of the cars using this kit. The idea of sucking in air from the engine compartment doesn’t sit well with me so I start looking into a way to modify the intake to draw in cooler air.

Day 39: EPL cable arrives but I have no luck loading the ECU with it.

Day 41: Friday March 19, ship my ECU to EPL to have them load the software.

Day 47: March 25, contact EPL to express my concerns about some of the problems I have encountered. It turns out I am the first person to contact EPL about the missing seals, gaskets, clamps from the kit. These are considered standard shop consumables and their absence is apparently standard in most cases when installing any aftermarket turbo kit. Unfortunately for me I previously had the APR Stg3 kit that did include all of these things so my expectation was that this kit included “all pieces needed for a smooth trouble free installation” as it was marketed.

The requirement to cut out the bottom of the airbox I learn is something that has zero issue for the hundreds if not thousands of S4’s that have apparently done this. (Later I discover on my own that cutting the bottom of the airbox allows the filter paper to become soaked when driving in the wet giving me concern that zero issues may be a very optimistic assessment.) Also, I learn that the dirtiest airboxes are found on cars with stock intake systems, not ones that are modified with a gaping hole above the wheel well.

I also mention how missing parts, improperly sized parts, and parts that are not properly configured have caused me additional unplanned costs and I propose a solution. This concern for the added costs is not acknowledged in the reply that I receive from EPL.

Day 55: April 2, get the car running. Runs rough and throws DTC’s.

Day 57: Send EPL more data logs.

Day 59: Send EPL more logs and comparison data of my car on K04’s.

Day 63: Cannot flash ECU with revised software from EPL server.

Day 66: Flash file and record data but show no changes from previous file. Contact EPL to see when new file will be made available.

Day 67: Hear back from EPL that new file is available.

Day 68: Send email to EPL but get out-of-office response.

Day 69: Send an email to EPL outlining what my expectations are with regards to support for the product I have purchased. This is prompted by unanswered email correspondence that I have sent to the shop that fails to get a reply throughout the workday. While I am waiting, I find members of EPL are making posts at various Audi forums.

A new file is made available for flashing, but I continue to experience problems getting my ECU to take a flash and quickly exhaust the ‘two credits’ I have available for downloading. I will have to wait until the following day to try again. I complain about the low number of credits I have for trying to flash my ECU given the difficulties I am encountering.

Day 70: EPL adds two more credits, explaining that they feel this number is more than adequate.

Day 71: Try flashing the ECU, but once more neither attempt will take and I have exhausted my credits. I will have to wait until the next business day to try again.

Day 73: April 19, EPL sends me some questions about my setup. Nothing appears to be out of the ordinary.

Day 76: I try and conduct an intake pressure test and discover that the TiAL inlets will pop off with as little as 5 psi of pressure applied to the intake side. I also find that not three weeks after asking EPL to apply a $250 credit toward a custom tune, to offset the unexpected costs I was incurring due to kit anomalies, which they did not agree to do, they are now offering a free custom tune, valued at $500, to anybody that buys one of their fueling kits. I am not very pleased by this development, but after inquiring EPL does agree to allow me to take advantage of this offer.

Day 82: Still troubleshooting an issue where Idle Long-Term Fuel Trim gets rich and throws a DTC. Also learn from EPL that 1 bar of boost around 3700 rpm is a good reading.

Day 98: May 14, send revision 3 data to EPL.

Day 105: EPL is working on a revised file and makes mention of some 100 octane gas that I used as throwing the tuning off. This was a misunderstanding on the part of EPL, there was no 100 octane gas in the car when they began tuning, but this subject will resurface several months later when EPL points out all the issues with my car and what I have done to hamper the tuning process.

As background, the topic of 100 octane fuel entered the picture because prior to swapping in the 605’s I had run a tank of 100 octane. I was planning to swap fuel pumps and so had run down to less than a quarter tank of gas. When EPL sent their base file and I got the car running on April 2 I was running very rich and getting excessive knock counts and over the course of several days of troubleshooting used the remaining 100 octane gas and refilled with 93 octane. Over the next couple of weeks I continued to troubleshoot on 93 octane gas. By the end of April EPL sent me the first software update. When the subject of having 100 octane in the car came up in mid-May, EPL erroneously concluded that the initial tuning they were doing was on 100 octane fuel.

Day 123: June 8, ongoing days of troubleshooting is getting no place so I take the car into a local independent Audi shop that is experienced in modified cars. They believe there is probably a small intake leak someplace but don’t have time to tear into the car to find it. They also point out that the driver’s side wastegate actuator rod is very close to the side of the car.

Day 151: July 6, I was hoping to be able to bring the car up to EPL so that they could look it over but that isn’t going to work out.

Day 161: July 16, my car is returned from the shop. I decide that since they will be pulling the intake apart this is the time to add some phenolic spacers and switch to the updated intake manifold. I had also come across a used set of ER intercoolers so I purchase them to swap out with my AWE intercoolers. Later I will learn that swapping between these two intercoolers requires an ECU software change. I had also come across a used Milltek Superdual exhaust system and decide to swap out my Supersprint for a larger system.

Day 166: Send EPL software revision 5 data for post maintenance evaluation.

Day 172: Next revision to the software is made available, EPL comments that they have numbed the IAT correction because the car is enriching with high IATs. They also point out that “unfortunately it doesn’t look like your intercoolers are up to the task.”

Day 186: August 10, still encountering challenges when I try to flash my ECU. I’ve got a routine down where I need to remove the USB driver from my computer and then reinstall it which seems to work most of the time. Unfortunately on my second attempt I learn I only had one credit and I’m out of luck.

Day 188: I learn that the revised file I am now loading on my car made 450whp at EPL’s dyno on another customer’s car.

Day 189: I get results very similar to some of the old files I tried. Unfortunately the naming convention EPL uses on their server is not very clear about which file is the latest, and the fact that EPL had made a valet file available for me, and left it on the server further confuses the issue. Turns out I had loaded an old file rather than the latest revision.

Day 196: August 18, EPL provides me feedback on my latest logs, commenting that if I have ER intercoolers on my car that they are performing poorly. It is at this time that I am also putting my data logs on an Audi car forum. Some interesting comments from EPL are generated at this point.

Somebody suggests I could get a second ECU to try a different tune, EPL replies with: “Or he can drive up for use to review hardware and dyno tune if at no charge….”

Somebody raises the point about whether my substandard performance is driven by hardware or software issues, EPL replies with:

“The first tune was a base map. The next 3-5 tunes had an air leak at the TB and different….. intercoolers.

At least one of then tunes at 100 oct in the tank with out us knowing.”

Remember I said 100 octane would come up again, here they are bringing it up and calling me out, erroneously, as being the cause for why the tune was not being productive. What comes next is the crux of the down on power discussion, which will ironically come back up months later and will lead to me look at alternative turbo’s

“Its not the tune. I think Jeff even believes that at this point. He’s missing a HUGE amount of power. Even if the tune was “off” its not like the car would be done ~80 hps.

Please stop pointing figures at the tune…”

EPL then provides a dyno plot from a car that was tested on their dyno with my tune in shop temperatures exceeding 90F where the car made 450 whp.

I inquire what type of Intake Air Temperatures this car is experiencing but my question is not responded to.

Day 208: August 30, in the continuing pursuit to discover why my car is down on power I have a compression test performed by a shop, and I perform a leak down test. The shop gets consistent numbers in the middle of the range the Audi Bentley manual specifies for the motor. This is deemed less than satisfactory by EPL, even though I have leakdown numbers that are very good. EPL suggests that the compression numbers being about 15% less than what they feel a good S4 motor should produce is perhaps not so coincidentally the same 15% that my car is down on power from where it should be and that we should start to accept that the motor is the cause of the low power output.

Day 209: I contact EPL to ask what further troubleshooting I can do, EPL’s reply is: “At this point, I think you have proven the engine isn’t healthy.”


Day 217: I decide to conduct a second compression test, ensuring the engine is hot. I obtain very solid readings and contact EPL with the results. The reply from EPL is: “Thanks for performing a second test… You are aware thats these results are now basically above factory new on an engine with many mile…correct?”

Day 287: November 22, making final preparations to take the car to EPL. They plan to do a compression test there and will put in my new sparkplugs that I bring along with prior to tuning the car.

Day 301: December 6, drop my car off with EPL for the tuning. It is bitter cold in Connecticut and the baseline runs that EPL does on the street turn in performance far better than any I have recorded. I have been using the same software revision and no hardware changes for the past 4 months and not seen anything close to this level of power. EPL looks over the data that they collect and inform me that the car is doing just what is expected, and that they don’t think there will be much more that they can do with it.

Day 302: EPL remarks on the compression test results “psi for psi this is one of the stronger 605 cars we have ever tested.”

I’m concerned about the very favorable temperatures producing results that will only be replicable in similarly frigid temps. EPL feels the shop temps in the mid-60’s are very normal.

Day 303: Tuning on the 93 and 100 octane files is completed. Dyno results are here: (I need to still add this)

Day 312: Pick my car up from EPL. Before I depart they replace the 93 octane fuel that was removed when the 100 went in. They take the car out to do another street log and decide to make another software revision based upon the results. I inquire about getting the data log but they indicate that they don’t want to give it to me since the software was changed after collecting the data. I drive the car home.

Dyno Charts:

93 Octane – No WMI

TiAL 605 Dyno Chart
25 PSI – 93 Octane – No WMI

100 Octane – No WMI

TiAL 605 Dyno Race Gas
26 PSI – 100 Octane – No WMI

Assessing the kit:

Over the course of the roughly five months that I was driving what was effectively the final state of tune for the TiAL 605 setup I was able to assess the kit under various conditions. I say final state of the tune because in August 2010 when I loaded software revision number 9, that revision remained on the car until I dropped it off with EPL for the dyno tuning.

The performance of the car when it was initially delivered to EPL, prior to any tuning, was assessed by EPL to be what was expected from the 605 kit. It was thought that little more was to be gained in terms of performance. Following the tuning at EPL, and return of the vehicle, the subsequent performance that I measured was no different than prior to the tuning, confirming that the revision I had spent much of my time driving was little different from the version I had following the dyno tuning.

My qualitative assessment of the kit, made in comparison to my recollections of the APR Stg3 K04 setup that I had previously, was that the TiAL 605 kit made more power, and did so later during the rev range with a slightly delayed onset of power as compared with the K04’s.

This was confirmed by comparing data collected while on the road which showed the TiAL 605 setup to have a substantially greater amount of power once past 4000 rpms. I found it interesting to note how close the performance of the 605’s was to the K04’s even in the lower rpm regions. After a closer look it is evident that the tune with the 605’s has more timing advance in the lower rpm region, offsetting what would otherwise be a more decisive power difference for the K04’s in that area. The subjective feeling still is that from an rpm region of 2000-2800 rpm there is some turbo lag. Not to such extent that the car is unpleasant to drive, but in comparison to the difference between K03 and K04 turbo’s, this change was more noticeable. Given the way these turbo’s were marketed, as a “quick spooling, responsive” system I was disappointed in the delayed boost onset that I was experiencing.

As I discovered over time, the 605 turbo’s are significantly affected by the atmospheric air temperatures. For several months during the summer I was chasing ghosts, trying to determine why my car was apparently so far from the mark for a 605 equipped car. EPL had concluded that there must be issues with my car, because the software tuning had run its course, and the software in my car was being loaded directly into other customer’s cars and performing as expected. When I delivered my car to EPL in the middle of the winter, and the performance met their expectations, my suspicions that temperatures were the root cause began to be validated. After receiving the car back from EPL, and collecting data in slightly warmer temperatures, I saw a drop in performance. The affect of temperature on the 605’s in the configuration my car is in can be seen here.

Despite the wide variation in performance arising from different intake temperatures I enjoyed driving the car with the 605 turbo’s very much. The nature of the car for around town driving was decidedly different than what I was accustomed to, but not something that couldn’t be overcome by changing one’s driving style. On the highway and roads where the speed was 50 mph and up the car was really in it’s element. It’s really fast once it hits 4000 rpm.

Assessing the tuners:

Throughout a major project such as this there are numerous vendors that a car owner can deal with, that was the case for me. The following summarizes my experiences, with some tuners having additional critique elsewhere in order to keep the content here concise.


The majority of my experience with EPL was positive. I had a similar series of events dealing with APR in 2005 when I installed their Stg3 kit and determined that the APR software was flawed. The customer service provided by EPL was on the whole better than what I received from APR. EPL was generally helpful in their replies to my questions and I had a sense that they were genuinely interested in seeing my car perform to the level that was expected. They were of great assistance in getting my car to the shop and helping me with returning it home. I also felt that they were able to get from the setup all that could be expected. They also provided good advice on what to look for while I was troubleshooting.

On the downside, it was not uncommon for me to send an email to the shop in the morning or the night prior to a work day, and not receive a reply all day, while personnel with @EPL after their username were posting online at various Audi enthusiast forums. When your car isn’t running right, and you’ve handed a shop a sizeable sum of money for the kit that’s not running right, spending time posting to the internet is not where I like to see a vendor’s energy being spent.

I also found EPL to have thin skin when it came to the product and my concerns. I found myself being rebuffed by members of EPL when I would raise issues I had with the car to other Audi owners.

Finally, what I would best describe as nickel and diming. As a result of several problems that I had with the kit I ended up spending well in excess of what I had planned for on the upgrade. My requests for some form of compensation were deflected to Jonathan Cohen, despite EPL having sold me the kit. Later when I was arranging to take my car to EPL the statement was made that they would look the car over at no charge to try and determine what was at fault. Upon picking the car up, following the assessment and tuning, I was asked to pay for the diagnostic work. I don’t mind paying for work, so long as the expectation has not been made that the work will be done at no charge.

The final annoyance is the spin EPL gives to this product. Of course it isn’t surprising that a vendor touts their own product, but EPL refused to provide me with the data logs from my car on the dyno, and they wouldn’t give me the logs from the car on the road. They claimed that because they had revised the software just prior to my car leaving the shop that the logs were no longer representative of how the car performed. Fair enough, and I would accept that, except for the fact that the Dyno numbers that they were flaunting on the various Audi forums as well as their Facebook page were produced with the software version that was no longer valid.

All-in-all though I cannot say that I would not do business with EPL again, because I do feel that they do good work and they do support the products they sell. I certainly would not steer anyone away from doing business with them.

VAST Performance

I contacted VAST Performance about obtaining a set of ported and polished exhaust manifolds. The decision on my part to install this component was made after I had begun work swapping kits and thus I was on a tight timeline. When I first inquired about the manifolds it did not sound like the availability of the part would meet my time requirements, but I was assured that the parts could be obtained in time. This proved to be harder than expected, and required overnight, costly, shipping to get to me in time. VAST offered to cover the additional shipping costs, but when it came time to send me a core refund, they withheld half of the shipping charge. I had to provide evidence from our email exchange to prove that I wasn’t obligated for the shipping, and then it took a few weeks to get a refund, but I still surrendered $25 towards the shipping because VAST was complaining about the overnight shipping cost so much.

I would still do business with VAST again.

INA Engineering / 034 Motorsports

I was in touch with INA Engineering and 034 Motorsports for four components, a Bosch 044 drop in fuel kit, the 034 3.5” exhaust system, phenolic spacers and transmission mounts.

The fuel pump and exhaust were not simple items, and each of these boondoggles is so drawn out as to be worthy of their own separate discussions:

Bosch 044 Drop-in fuel pump
034 Motorsports 3” DP’s and 3.5” exhaust


Wicked Motorsports was selling a used set of ER intercoolers at a very attractive pricing, one that made the switch from the AWE intercoolers a possibility. This was a simple transaction, and everything went smoothly.

HB Motorwerks:

Is my local Audi shop. It’s too bad small independent outfits that aren’t all over the Audi forum’s don’t get a lot of respect. The people at HB Motorswerks have pretty well nailed it each time that it came to diagnosing a problem. The discovery that the wastegate actuator arm on the driver’s side turbo was close to the engine compartment wall was made by HB Motorwerks. They also discovered the small intake leak which resolved problems I was having with the car.

Jonathan Cohen:

Jonathan is rare because he is receptive to constructive criticism. He’s also very serious about customer service. When I received the 605 kit I had been in talks with Jonathan about the kit. He gave me his cell phone number and offered to take my calls any day of the week, at any time, just try to be respectful of when he’s gone to sleep. I ended up taking him up on his offer several times, and his familiarity with the kit helped to get me get back making progress quickly.


I hadn’t intended to have any dealings with A.M.D. During the process of trying to diagnose the performance my car was returning I had contacted another S4 owner to see if I could take a look at the data results their car had made. They’d informed me that AMD had the data from their car, and they would contact AMD to see about getting me the data I had requested. The initial request this person made to AMD went unacknowledged, so I contacted AMD to inquire about the data from the other person’s car. The response I got from AMD was to laugh at my request and tell me I didn’t need to make any comparisons between my car and this other customers. Never having dealt with AMD before it was extremely disappointing to see a business conduct itself in that manner.

Audi B5 S4 Information and Testing