mrosenq1

Correct, 2.8 cant use 2.6 pistons. It would be possible to use a Hella ECU on a 2.8 (Im doing it on my car). You need a standalone rpm switch, available from any engine tuning company, or can easily be soldered together by yourself. A nice thing with this is that you can adjust the switchoverrpm. The hella ECU and MAP almost never fails, the only thing that breaks on these Hella systems are the lambda probes otherwise its bulletproof.

However, to make full use of a hella ECU on a 2.8 you need to adjust the fuelling, either by a software change or a fuelpressure adjustment.
Another possibility is to at WOT change the resistance of the coolant temperature sender with a relay to increase the fuelling.

Lago Blue

<center><img src="http://www.12v.org/engine/images/2_6.jpg"></center><p>
...What is it in particular that causes the 2.6 to be burning more fuel than a 2.8? Its' engine management perhaps or your just right foot trying to keep up?

What are some details of the "fuelling tweaks" used to improve its' mileage and/or performance?

There is scant information about the 2.6 at 12v.org (image above found there), a favourite site for many readers here, perhaps you are familiar with it? There, they are also asking for any further data on this particular version of the engine. The fellow who is responsible for that site often posts hereabouts.

Lago Blue

...in the 2.6.

Just for fun; 2.6 is 92% of 2.8. The 2.8's 174 h.p./250 N.m. minus 8% for a displacement reduction gives 160 &amp; 230. Yet the 2.6 has only 150 &amp; 225. Backs up what you said. Thats about 2.2% torque and 6.3% power expected, missing at peak, due perhaps entirely to the missing variable length manifold.

The idea of a (possibly faster winding?) 2.6 engine with <i>2.8 sized and equipped everything else</i> on it sounds quite appealing!

Why do you think Audi provided different pistons for the 2.6 and yet lowered the compression, does that small reduction (10.0 vs 10.3 to 1) allow you to more safely run a lower grade of fuel? What octanes and rating methods are available to you overseas?

Are the lambda probes (O² sensors) you're using specific to the Hella ECU?

Are software changes to the Hella ECU available?

I like your idea of WOT enrichment, perhaps it could be hooked to the switch on an automatic's throttle body?

independent77

just saying.

mrosenq1

Audi/VW has traditionally used the same size rods in most engines and varied the pistions, why I dont know.
In europe the 2.6 is specified for 95 RON and the 2.8 for 98 RON so there is probably a part of the difference.
The lambda probes are the same BOSCH for Hella and Hitatchi.
There are software changes available, if they are any good Im not sure. Most tuned V6 in europe uses a piggybacksystem or standalone ECU (like Haltech and so on)
The fuel enrichment on WOT works good, I have used it on several different cars, on idle and partial load the lambda regulation of the original system corrects for the engine changes and on WOT you use a wideband O2 tool to determine what resistance that is suitable. Most cars have a WOT switch that can be used.

I have no experience on automatics, we dont use them in europe

I run my car with 2.6 block and ECU and 2.8 I/M and I would say that it has a definite happier rev character than a 2.8. Some grunt below 2000rpm are missing though.

mrosenq1

I use 12v.org a lot!

In europe most cars with V6 are C4 Avant cars, and the 2.6 is just slighty to small to be enough for that car =&gt; you use a lot of right foot.
Secondly, due to the fixed IM you have a worse efficency of the engine.

There is one big downside of using MAP as your main source of load, once you reach atmospheric pressure nothing happens. This means that the ECU has NOOO idea that you have changed the TB, ported the IM, changed the cams and so on. Therfore you need to tell the ECU this, by altering fuel (and iginition) maps. The best (and correct way) is to change in the software. Most of us cant do that in the factory ECU.

2 Options:
1. Buy standalone ECU = problem solved
2. Cheat the original ECU to fuel the engine differently.

Before going any futher, number 1 is the best way to go, myself i like Haltech E11, but there are other brands just as good.

On the V6 my experiece is this:
1. Raise the fuelpressure, 0.5-0.8bars, this will give enough extra fuel upp to IM changeover on a tuned V6 (lambda regulation will fix the correct mixture on non-WOT).
2. Put in a relay that changes the coolant temerature sender resistance when 2 conditions are fulfilled: 1. WOT and 2. &gt;4000rpm.

All this must of course be tuned in using a wideband 02 tool.

Lago Blue

...Thunk! Apple hits head. Oops I stand up a little dazed but corrected. Thanks!

independent77