Quick intro

So even if the subject is getting rather old and “outdated”, it seems interesting to some – but highly challenging – to get decent information on the matter of Audi 10V turbo tuning.

Ah, “tuning”. I am not so overly fond of that terminology either. The forced induction 10V will probably sit with the same aspects of any other build: if you upgrade and exchange enough parts, physics and dynamics will change, and so the nature of the power potential at hand.

So for the sake of this page, I simply want to try my best, fetching information from different sources, trying to make a holistic view of what is possible with enhancing any 10V turbo motor sticking to it’s mechanical fuel management – the Jetronic on Hitachi MAC control units.

I think this will probably one of the longer pages here on ableitet, and please note it will be my best attempt to gather information from multiple sources to provide some sort of idea what really is the potential in the mechanically managed 2.1 and 2.2T motors. Page is subject to changes (of course).

Disclaimer: And remember, all actions on own risk!

Oh behold those references!

I have not done it all, and I will not take credit for any extensive exploration with a proven result to back it up. However, I find it reasonable to draw you the picture of some points of reference from the 80s:


Walter Treser was a man running Audi Sport for a period, before “hastly exiting” and starting his own tuning and styling company. Treser Quattros sported a fuel distribution unit for 8 cylinders, blocking off some and supplying via the 5 only needed.

Treser packages were marketed as 245, later 250 hp.


Okay! So Lehmann is probably not the first name you’d think off in the modern day, in terms of VAG performance upgrading. Its not so surprising, as Lehmann is a bit of a more hardcore supplier: he is practically the royal supplier to Audi (and somewhat rest of VAG) of race engines, as has been for decades.

A fresh setup from him is claimed at 240 hp.


I know Rolf Nothelle has had a Quattro on hand since the early days, and is a company still going on VAG youngtimer tuning.

Looking up old marketing material, package is markted as 240 hp, utilizing a 280 degree camshaft.


Used as a reference in Dave Pollard’s book too, Facebook sometimes surprices; Recently a post was made in the international urquattro group, and I will cite the Superchips info page (physical, not this HTTP stuff).

Early Quattro coupe: This car gains 65 BHP and 70 lbs ft of torque (95 Nm) at 3700 rpm using 1.25 bar boost pressure or an absolute manifold pressure of 2.25 bar. … The real power gains are in the mid range …

200 Quattro and Automatic: These cars have a different engine and engine management system to the Coupes as it incorporates a higher compression ration and knock sensor to retard the ignition in case of detonation. The car runs a lower boost pressure as standard and we increase it from 0.5 to 0.75 bar to give an extra 30 – 50 bhp …

Later Quattro Coupes: From January 1988 to mid 1989 these cars used the early engine with a revised cylinder head and a sophisticated ignition computer with knock sensor. We increase the boost pressure on these cars from .7 bar to 1 bar tog et an extra 65 bhp. The performance figures are very close to the early quattros but with vastly reduced tubro lag and increased driveability.

Superchips ltd promotion/info sheet

I really cannot speak for the end result that Superchips found themselves, but I make note of a claimed 265 hp on 1.25 BAR boost for the 2.1T ‘WR’, ‘GV’ and ‘WX’, and 1.0 BAR boost for the 2.2T ‘MB’.

Chiptune the Jetronic (MAC)

So we have the Quattro, the 100 turbo and the 200 all sharing the usage of the 10V turbo motor in slight variations. For all of them, the Hitachi MAC-unit (ECU) management can probably be best described as this:

It basically is a mechanical fuel system, and the ECU is only somewhat controlling the fuel pressure to run within the lambda-area, in addition to the ignition timing. If it senses signs of boost peaks, it will retard the ignition until the tendencies ceases.

Anders nordman, Audinsane.se

In essence, these eary cars does not see the same possibilities as with the more modern Motronic, pinpoiting fuel, boost and timing all together.

Makes sense then, why no works rallye Quattro featured the same setup as road cars…


Basic intro made, now it’s time to cover an understanding of approaches: modified control unit and hardware changes.


Considering the features of a turbocharger, a swap of the old K26 unit found on the majority of old 10V turbo application may be worth considering, especially as some or more or less bolt-ins on the same flange on the manifold. Water or oil cooling worth familiarizing with.

For some, changing into the K24-7000 (alike 2.2T ‘MB’ Quattro or S2/S4/S6) may prove useful, as it still will cope a delivery of 1 BAR boost, but enhances spool and response somewhat = driveability.

Dave Pollard mentions in his book the usage of the RS2 turbo (K24-7200, which is a K26 base) delivering boost in the range of 1500-7000 rpms.

Classic tuning

Any 10V basis will benefit from any classic workmanship done to the components. I personally find Techtonics Tuning as a provider with a good selection of valve-technique at offer.

But you don’t have to exchange parts. The counterflow header benefits of valve cutting, porting and polishing, so optimizing existing components is more than adequate (within these frames).

Boost regulation aka “Bleed-kit” – in progress

Here I really just leave it up for a loose translation of the old article on 10V turbo tuning found at Audinsane.se, by Anders Nordmann.

I have also somewhat rearranged the structure, as his article is somewhat patched. Just remember that when optimizing the mechanical 10V turbo, you need to embrace two aspects:
I. increase the system’s boost pressure
II. adapt so the ECU’s boost safety threshold can be surpassed

Does it feel like your 100/200 turbo 10V is a bit sluggish at times, compared to other turbo cars? You’re probably right…

Audi charges these engines with only 0.35~0.39 BAR, which essentially is low pressure in question. Usually turbo applications are running 0.6 BAR upwards. Say, if your knock sensor is a bit acting up, the ECU will retarad the boost pressure above the wastegate spring, leaving only the spring pressure left (grundtryck), meaning a 0.25 BAR and estimated 140-145 hp if a healty engine.

Regardless, Audi left in quite the complexity for their low boosting applications:

  • Watercooled turbo
  • Double knock sensors (1989-)
  • Oilcooling of pistons
  • Oil cooler
  • Turbo timer
  • Cooling of injectors

210-220 hp from these are doable through a uprated air filter and new chip, and last well too.
But what does this chip do?

In principal, two things: the pressure threshold for when the ECU cuts the fuel pump or retarding the ignition , and/or allowing more boost over the wastegate.

Please note the usage of mechanical fuel distribution, and that the ECU only controls the fuel pressure somewhat within a range of the Lambda-sensor, and it will limit/safeguard the application by retarding the ignition.

An alterntive way to adjut the boost – by valves!
What is known as bleed-valve setup has been used since the first SAAB turbo applications. It functions well, exactly due the fact it is a simple, mechanical fuel injection.

Does your car have an automatic gearbox? Then you should play it safe, especially if in combination with quattro drivetrain due the increased grip. Rule of thumb is to run it safely at 0.6 BAR.

(I leave out the section on boosting up until the ECU threshold.)

Is there a way to allow for boost above the ECU threshold? Yep!
We need to make a workaround to prevent the ECU sensing system boost above the threshold value, by installing a pressure regulator on the blue #40 hose running between plenum and ECU.

Pressure hoses, Aud 10V turbo

Hang on, what are we inflicting now?
We retain all electronic management of the engine up until the threshold boost, beyond that the lambda sensor should regulate towards 14:1 lambda (A/F). But, we’ve taken away the ECU’s ability to prevent over-boost if anything happens.

A safety tip could be to put a safety pressure valve in parallel with the adjustable valve, i.e. if you have regulated for running 0.9 BAR, it bypasses if 1 BAR system pressure happens and triggers the ECU’s safety measures.

Building more boost
The injection of these engines can cope with up to 1 BAR boost. At 1.2 BAR boost you need to strap tight the intercooler, to prevent the tanks from popping off.

Higher octane fuel is then also needed (98 instead of 95), and connecting a proper boost gauge to see – and adjust for – the plenum’s actual system pressure makes sense. Connect it at green #9 or at blue #40 prior to any valve.

What do we want to achieve? We want – controlled – to increase the boost pressure, thus achieveing a bigger output from the engine. It can be done by first putting a limitator on the hose going to the wastegate, så the pressurised air cannot freely pass, before allowing a little of it to escape through a valve (behind the limitator). I.e. if system boost is 0.6 BAR, and we relieve 0.3 BAR, 0.3 BAR is left to open the wastegate.

These valves are intended to be mounted on the red #28 hose, seen above.”

Disclaimer: I am by no means a highly capable engine person, but my impression of Anders’ article is that he did not explicidly state how this will be done:

Whilst we manipulate the percieved system pressure towards the ECU, the actual system pressure is the result of increasing at what point the wastegate bypasses exhaust gasses from the turbo.

Meaning that any increased counter pressure (uprated wastegate spring) and/or reduced trigger pressure (reduction in pressure coming from plenum in hose #28) will define the total system boost.
Minimum system pressure will always follow the wastegate spring.

Manipulating ECU – resistor mod

Please note, this section is a somewhat clean copy of an old Word-document I found on one of my harddrives. I will however section out parts related to the Zener diode mod further down.

Sadly I am not able to tell who made this writeup (please correct me!), but it does also make a cite from Ben Swann – more from his side further down on Software section.

In order to run higher levels of boost, some adjustments need to be made. This is the infamous ECU resistor mod that fools the ECU pressure transducer into thinking that the level of boost has not exceeded the factory specifications and prevents the computer from turning off the fuel pump.

You need some basic soldering skills, a soldering iron, some resin core solder, a little nerve (ECU=$$$), a resistor of the appropriate specifications and about an hour.

Be Warned!!
This Mod can cause you to destroy your engine if used alone – the Schrapnel Knob Mod is a safety feature designed to protect against over boosting. I also use Sunoco Premium 94 Octane fuel with STP Octane boost in every tank-full to prevent knocking and keep the engine together. [Remember to compare with octanes norms in Europe.]

Refer to the instructions on Ben Swanns site at: http://www.homestead.com/Ben_Swann/boostin.html  for complete details and also check out Scott Mockrys site at http://www.sjmautotechnik.com to make sure everything is in tip-top shape BEFORE you start pushing the limits of performance on these engines! (I know – I blew a head gasket and burned three pistons – ouch!!)

The resistor mod has a suitable resistor instead of the diode, the lower resistance the higher the boost without fuel cut… A suitable resistor, typically 475 ohms, is placed between pins 1 and 10 on the ECU pressure transducer, which fakes the ECU into getting the value for a lower pressure.

This 1) make the fuel pump shutoff at a much higher point, somewhere around 2.7 Bar, and 2) will advance timing across the board.

I have modified mine so I can set the value a bit higher as the timing with 475 ohm tends to be a little to much advance, especially on a hot day under load.  A fixed value closer to 600 ohm may be a better bet.

The resistor mod is simply soldering a resistor between pin 1 and pin 10 on the Pressure Transducer.

470 ohm is typical and the lowest value to consider using, as anything less will cause too great of a timing advance. Other values may be considered suitable depending upon boost being obtained.

470 ohm is good to about 25 PSI (over 2 Bar). A value closer to 600 ohm may be more suitable for more moderate boost levels, and less likely to incur detonation and let the fuel pump kick out if boost levels around 2 Bar are reached, should a problem occur, such as a torn wastegate diaphragm or leaky hose.

Since this modification also advances the engine timing over the entire RPM range, which may induce hard starting, and worse, detonation at high boost levels – it will also cause the digital boost readout to be incorrect. However, the upside is the advanced timing generally gives better performance, especially at lower RPMs. It is imperative to have the knock sensor fully operational. Detonation will typically occur at 18 PSI and higher, depending upon engine load and ambient conditions and quality of the fuel. I never use under 92 octane, unless absolutely necessary. …

I have been using the resistor mod for boost pressures to about 16 PSI for over a year now.  Other than the intercooler the only weakpoint I’ve uncovered in the system is the hose going from the intercooler to the throttle body, which is often referred to as the “Michelin Man” hose. This hose tends to blow out at the bottom. Always carry duct tape as these types of things may occur, but the tape will get you home.

I highly recommend referring to Scott Mockry http://www.sjmautotechnik.com/ fabulous web site for great information on increasing performance and boost and general troubleshooting as well.

I also would refer anyone not proficient in electronics, soldering, and general mechanical abilities to have these modifications performed professionally by Scott or one of the others mentioned in this writeup.

Ben Swann

Here is the ECU in situ; (this is a MAC-14 in my 1990 200Q – door panel is off in case you were wondering)

Unplugged and spun around;

Internal view of the inside showing all components – pressure transducer is on the upper right of the board with the black tube leading out;

Close-up of said transducer;

Here is the back side of the main board with the 470 ohm resistors (sourced from your local Radio Shack) needed for this mod;

The bottom left is where the resistor must be attached, here are the before and after shots;

Close it up – put it back in place, and combined with the “Schrapnell Knobben Mod” you will have plenty of opportunity to blow the doors off your buddies – or your engine if you get too carried away!!

Zener diode mod & voltage diverter

From the same doc referred to under the resistor mod-section, there are some specific comments against both zener diode mod or running a voltage diverter.

I will quote and agree with Steve Buchholz’s comments here that, “The zener clamps the input to the A/D so that the ECU never thinks it sees a pressure above that point and thus does not activate the overboost shutdown mechanism. Many people swear by this mod, claiming many miles of trouble free service, but personally I would not recommend doing it. As long as all is well it may be fine, but be sure to keep all of the car in tip top shape at all times, because if you get something like a tear in the WG diaphragm things may change in a hurry.

Steve also states, “I would also like to speak against the thought of putting some sort of an adjustable voltage divider in the boost signal to the A/D on the ECU. The whole reason the ECU is there is to take inputs on manifold pressure, engine RPM and throttle position and determine the operating parameters of the engine … ignition timing, WGFV position, and yes if the fuel pump should be shut off. By scaling the voltage you are causing the ECU to think that the engine is running at a different point in the maps than it really is. This may not be that bad a thing, but it is not likely that the timing parameters will be better at this operating point than they would have been if the engine really knew where it was operating. Realize that I don’t have a problem with scaling the voltage out of the pressure transducer to increase the active range available to the ECU, but if it is done, the code in the ECU should have a commensurate change so that it “understands” the new calibration.

I tend to agree with Steve overall, and suggest erring on the side of caution if using the resistor mod. I have never really agreed with the zener diode mod, as it seems to do no more than cutting the wire which disables the fuel pump shutoff, a definite “no no” in my opinion.

Ben swann


Regardless of the limited possibilities there are within the MAC units, there still is some room for electronic optimization/alteration that can be put into a EPROM.

This is seemingly a very advanced field of competence, and I’m not holding that. But I am trying my best to bring forward some sort of insight and history here.

QLCC & Ben Swann

State-side the beforementioned Ben Swann and other profiles (Dave Lawson, Steve Eiche, Paul Timmerman, Graydon Stuckey, David Kavanaugh, Steve Buchholz, …) seemingly had a community joint-venture in the mid-90s for coming to grips with the EPROM’s engine instruction structure. They jokingly called it the Quattro List Chip Club.

To my understanding they shared decrypted instructions and parametres, R&D test results and programming developments between themselves. What they then brought to the “Audi optimization scene” was probably subject of individual tweaks and intentions.

What does it do?

In a thread on AudiWorldforum, one can get a somewhat (if as little skilled as me) understanding:

The EPROM in the ECU contains both data and the actual instructions … The actual uP instructions are used to monitor the engine parameters and then set the timing and fuel (frequency valve duty cycle), … premium timing maps

‘boxerfan’, on QLCC history

Sitting in Europe, I can only relate to seeing offerings from Ben Swann, both for 10V and 20V. A short while back, by coincidence, I came across a ‘MC’ upgrade kit from Ben (EPROM, wastegate spring and his original instructions) for €150 – which made sense to collect.

Overview of Audi MAC ECUs

80-87Quattro ‘WR’01A035*C0.8 ?
85-88Quattro ‘WX’, ‘GV’020.6 ?
100 ‘MCv1’06A035*R0.6 ?
100 ‘MCv1’11C035*T
88Quattro ‘MB’12B0.8 ?
90200, 100 ‘MCv2’14447*L0.8 ?
90-91200 incl autom.15447*M0.8 ?
Attempted correlations of Audi models and MAC units
* is the OE fill of “xxx 905 383 x” VAG format

Please note: this table really have to be considered a work in progress, as I am truly not confident in their exact specifications or correlations.

Highly generalized, these engines seems to be low (162~165 hp) vs high power (182-200 hp), old version or new version incl. double knock sensors.