[V8] 5 spd conversion: 3.6 vs 4.2

J örgen Karlsson jorgen.m.karlsson at home.se
Sat Mar 6 23:23:20 EST 2004


Since there was a few opinions on which injector the 3.6 and the 4.2 has I checked it with Bosch. When I checked witch cars had 0280150424 was used in I got:

 AUDI - A6 (4A, C4) - S6 4.2 quattro   
 AUDI - A6 Estate (4A, C4) - S6 4.2 quattro   
 AUDI - V8 (D1) - 4.2 quattro   
 AUDI - 100 (4A, C4) - S4 V8 quattro
 AUDI - 100 Estate (4A, C4) - S4 V8 quattro

 0280150416 gave me:
 AUDI - V8 (D1) - 3.6 quattro 
  04.93-02.94  -11.93  180  245 
 AUDI - V8 (D1) - 3.6 quattro 
  10.88-02.94  -11.93  184  250 

For the hell of it I also checked 0280150441 which gave me:
 AUDI - A8 (4D2, 4D8) - 3.7
 AUDI - A8 (4D2, 4D8) - 3.7 quattro
 AUDI - A8 (4D2, 4D8) - 4.2 quattro
Unfortunally I could not get flow information from Bosch's site. The only source I have is that I flowed the 441's yesterday and this pdf:
http://www.student.kun.nl/p.oonincx/downloads/echt_alle_injectordata.pdf which indicate 150cc, 173cc and 203cc respectively.

The 173cc injector seem to small to provide a decent full power mixture for 300hp at 3bar fuel pressure, but to get it's flow up to that of the ABZ 203cc injector we can increase the fuel pressure to  3bar*(203/173)*(203/173)=4.13bar. Is the fuel pressure on the ABH and PT 4 bar?

When renting the expensive Autronic wideband lambda meter to tune the Autronic SMC I use for the ABZ I found that the 203cc ABZ injector wasn't big enough to provide the 12.7:1 AFR I wanted to maintain at WOT (the ABZ fuel pressure is 3bar).

I must say that I am very impressed by the 330-370 hp figures calculated from timeslips! Is it really low to mid 13's or is it only calculated from trap speed?

Given the size of the injectors Audi must run the ABZ a bit lean of 'max power', if they do the same with the other V8 engines I would expect that a 3.6 ECU would increase the power of the 4.2litre a bit since it will run a slightly richer mixture compared to the 4.2 ecu that know of the bigger injectors.

If this is true a similar increase in power should be seen if 4.2 injectors is fitted on a 3.6 litre. Or if ABZ injectors is fitted on an ABH. I would be interested in the results if someone tries this. ATR performance has adjustable billet fuel pressure regulators that should fit the PT and ABH fuel rails.

Jörgen Karlsson
Audi 80 4.2Q

-----Original Message-----
From: DasWolfen at aol.com
To: CoultL at aol.com, ekellock at adelphia.net, v8 at audifans.com
Date: Fri, 5 Mar 2004 18:03:00 EST
Subject: Re: [V8] 5 spd conversion: 3.6 vs 4.2

In a message dated 3/5/04 4:32:22 PM Eastern Standard Time, CoultL writes:

> "while retaining the 3.6 electronics"
> Did you use the injectors from the 4.2?  I cant imagine the 3.6 units could 
> flow enough fuel for 330hp.  Just curious.

 4.2 injectors are the same size as 3.6 injectors. In normal useage they're 
not even large enough for 300hp..but...

 ......V8's run ridiculously high fuel pressures for some strange reason. Put 
enough pressure behind any injector and it will pass the fuel you need.

 As for supporting 330hp..... John J's 93 is approaching 370hp with stock 
injectors. =0)

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