Forgive my ignorance, but how can "decent custom mapping" get around the hardware limitations of the factory J538 PWM controller being unable to power a heavy electrical load that is the TTRS pump?
I suppose you could lower the requested pressure so that the pump is driven at a lower duty cycle which will result in less current being supplied by the J538 controller and so prevent it from damage, but then you aren't really using your TTRS pump at its maximum potential which begs the question of what was the point of getting this pump in first place?
Also, the only other proper way to power a TTRS pump is with a TTRS J538 Fuel Pump Module Part No. 8J0-906-071-A, which sells for $438 (
https://www.ecstuning.com/ES2213697/) and is definitely not plug and play.
Hi Rick,
As you can see,there have been a number of issues around fuelling an S3 (or other similar car) beyond the limits of the stock fuel pump.
The system VAG have used is quite crafty in doing away with the feed/return system such as with a set of Bosch 044 pumps,and using a demand system with a PWM controller.
One way around it is the USP auxiliary pump system(which is boost triggered,and when active,reduces the duty cycle of the stock pump,and together can fuel for over 600bhp)and another was the short-lived APR aux pump system which used the LP rail pressure to trigger it,and do the same thing.
Using an RS pump will also fuel for over 600bhp,but as you say,and others have found,can lead to overheating the S3's PWM controller.
The whole point as you've also said,has to be getting the S3 fuelled adequately for over 440bhp,where the stock pump maxes out,and if you can't run the RS pump beyond that level,there is no point.
I'm fortunate in having the USP system,and another solution in the shape of the new ECU I have,but for others,finding the right drop in pump is the first step,and then running it correctly is the next.
I do think that for the TTE420 and other hybrids,not running beyond 440bhp,that a bigger capacity pump may not always be a requirement.
We certainly didnt run into fuelling issues until we hit 440bhp,on a GT3071.