Audi R4R

I was looking at a 2.0L GT25 Audi A4 with an SDS engine management system that had pretty much all the goodies I have in my car. But it had an auxiliary fuel tank along with another set of larger injectors (on another fuel rail, etc.). I was curious if someone could explain to me how something like that works. I wish I had more info, but I don't as of yet. But any explanation of the mechanics would be appreciated! TIA

Audi2ptzero

when to open, but it has to do so much sooner if the injectors are further up stream on the intake manifold runners. Most people dont like doing this because your just spraying fuel into the runner and not directly at the valves. This is why I went with larger(800cc) injectors.

StevenH

Here is the thread that it was discussed in. It should answer a lot of your questions. I still may do this further down the road when I upgrade turbos again.<ul><li><a href="https://forums.audiworld.com/performance/msgs/50676.phtml">https://forums.audiworld.com/performance/msgs/50676.phtml</a></li></ul>

xr4tic

That way it drives exactly like stock during part throttle, then under boost, it uses the auxilliary system to add the necessary amount of fuel.

I suppose if you keep it separate, you could fill it with race gas too.

There is a certain point where an injector is too large, and won't be able to allow the car to idle. This could be their workaround.

slowslc

Neuspeed's car (the BTCC Turbo) has also primary and secondary injectors.

They told me that if they go too big, the response time is slower and hurts low end performance..

Audi R4R

The car idles perfectly well &amp; drives pretty well. There's a fuel pump that came with a TAP Stage 6 kit (no clue what it is). There is a separate fuel tank as well.

What I don't get is how the transition can be seemless between high boost hard driving &amp; regular daily driving? TIA

Cheers!,

Steve

Audi R4R

cool! thanks for the link!

Audi2ptzero

this means the injector runs at a lower CC then doubles its size during boost, which means thd car runs smooth all the time and does not have idle issues. I will be running 800cc injectors on my setup.

Kevin K2

The beauty of this piggy back setup is that is can lay low during normal robust driving. But at the stock or chipped limits, when duty cycles max out, the secondary inj's can slowly be brought online to compenaste with 2D maps. say 5% at 4.5K at wot only, going up to 20% at max rpms. with 4 xtra inj's, could be located on the 4 runners!

aquamist aslo has a similar MF2 aic system.<ul><li><a href="http://www.sdsefi.com/eic.html">SDS-AIC</a></li></ul>