[V8] Father/Daughter V8s & 4.2L 5-Speed Programming

Mon Aug 15 17:14:48 PDT 2011

 Good post Allan...  With Audi offering a manual 4.2 in the v8, time might be better spent on the 4.2 harness and ecu than on the 3.6 harness 'adaptation'.  I know for a fact the 4.2 camshafts stock make the HP reground 3.6 camshafts look small, so the programming of the 3.6 tables will not be right for the 4.2 engine, in 3.6 stock trim or 3.6 ABT trim.  Tom, I'm not about cheap fixes, as that's not my business or interest.  I could care less if one 'wants' to do a 3.6 wiring/ecu swap onto a 4.2 motor, but it's certainly not necessary, nor rocket science, nor the 'only' option.  It's the internet entitled freeware way to make something work IMO.  Happy to be the guy that stands up and challenges 'because the other guy did it' thinking...  I've been on these lists a very long time, taking heat from folks that seem to feel my/all knowledge 'should' be free.  IMO, a DIY mod is  not all about price, it's about the value of the knowledge you gained doing a mod better.  Accepted practice for price, does not set a standard for value.

Food for thought, nothing more.  And it appears Allan found a 'better' way = progress.

Cheers

Scott J

-----Original Message-----
From: Allan Vega <allanvega at comcast.net>
To: Professor GT gmail <CavalloGT at gmail.com>
Cc: V8 at audifans.com <V8 at audifans.com>
Sent: Mon, Aug 15, 2011 10:00 am
Subject: Re: [V8] Father/Daughter V8s & 4.2L 5-Speed Programming

If you have access to the v8 wiring diagrams (everyone here should have a PDF 

version by now) it actually not difficult at all for the average 

do-it-yourselfer to figure out.

When originally did my 4.2 conversion, I went with the 3.6 harness and ecu for 

several reasons. 1. I already had it installed in the car. 2) it was already 

chipped with the abt software. 3) while reading through the 4.2 self training 

manual, I discovered that if I used the proper 4.2 harness and ecu found in the 

US spec cars (which only came in automatic) I would have an issue with the 

timing being retarded. You see, with the 4.2 auto ecu, it has additional imputes 

from the tcu. If the 4.2 ecu doesn't see this signal (which cannot be 

practically duplicated) it just retards the timing. This is why the 3.6 ecu 

harness and ecu has been used in most 4.2 swaps. That is also the reason the 4.2 

cars are much more responsive the the 3.6 cars. 

Now, let's forget about the sequential vs bank injection argument for a 

second(though valid) there is also the issue of proper fueling and timing for 

the hotter cams the 4.2 posses. The 3.6 ecu cannot take advantage of 

this,because it was not designed for it( though the abt chip 3.6 ecu probably 

makes up for it a little). 

So, what does one do in this paradoxal situation? Well let's see, where in the 

world can one find a proper 4.2 v8 quattro with a factory manual transmission ? 

That's right kids, Europe....more specifically, Germany. If somehow were able to 

get your hands on an ecu from a  

Factory 4.2 6-gang, you would solve the issue of not haveing proper fueling and 

timing with the 3.6 ecu, as well as solve the issue of having the timing pulled 

back because the euro ecu is not looking for the tcu signal ( remember, euro ecu 

must be from a manual car) 

So, how does one know if one is buying a true euro ecu from a manual 4.2 car? 

Easy, cross the part number in the European section of etka using the ATP 

feature( you should all have a copy of etka as well at this point.

Now for the easy part, the wireing. The beuty of the v8 engine harness, is that 

it's modular. It's a direct swap, plug and play between the two, the the 

exception of the o2 sensor. If you simply just repin this wire to the correct 

location, you would still have an issue. You see, on the 4.2 cars there was an 

o2 sensor relay added for the heated element. While the 3.6 cars had a constant 

ground, and power supplied the the fuel pump relay ( Read....heating element 

energized anytime car was running) the 4.2 cars had it's ground supplied and 

controlled by the ecu via a dedicated output. Power was still supplied by the 

fuel pump relay, but now the ecu could control when the heating element turns on 

and off, by killing or supplying a ground signal to the o2 sensor relay. 

Furthermore, this ground signal is current sensing( read: the ecu knows if you 

bypass the relay, and turns on the check engine light and retardsthe timing. 

BTDT. Make sure you wire this relay in using a standard au

 to relay and your 4.2 wiring diagram.

All of the above has been proven and done to my factory five speed, including 

the proper euro ecu.

For the record, motronic remapping has been available for a while here in CT( 

Tony Chick @ EPL) and for those who want to tune there motronic themselves ( I 

wouldn't recommend this option unless you know someone who knows how to tune) 

o34motorsport will be offering this option shortly

-Allan  

Sent from my iPad

On Aug 13, 2011, at 10:11 PM, Professor GT gmail <CavalloGT at gmail.com> wrote:

> Well I was finally able to find a good engine (3.6L) for my pearl white 91 

automatic V8 (16 yr old daughter's car) (thanks George), and I already have a 

good 92 donor 4.2L for my pearl white 91 5-speed (my toy) ( thanks Allan), so 

all I have to do now is start spinnin' wrenches!

> 

> Yep, made the trip today with my buddy and his flatbed (thanks Scotty N) to 

pick up a good running 90 automatic car, so I can make the white automatic car 

whole for my daughter - lucky kid, I wish I had someone to build me a nice car 

when I was 16.

> 

> Anyway, can't wait to hit the road with our Father/Daughter Pearl White Twins! 

Doubt they will be ready for sFest this year, but should be no problem for next 

year.

> 

> Gotta vet out the details of the 4.2 swap because it is true that to go 

backwards in technology from sequential fire to bank fire, while totally 

possible, on the surface just doesn't make good sense. That said, if the 4.2 

Motronic cannot be programmed to forget about the auto trans ......... Well it 

might be the only viable option without completely scrapping the Motronic 

control unit altogether and going with something else. 

> 

> Come on, there has to be a techie out there who can crack the Motronic code 

and make it work. The BMW boys seem to have figured it out. How about you Audi 

Gurus - what gives?

> 

> Thanks,

> 

> ProfessorGT

> (Sent from my iPhone4)

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