Hi All,
Just to explain my initial post re. Passat TDi 130 de-cat...........
Firstly, there is no Milltek de-cat pipe available for longitudinal engine TDi’s (Passats, A4’s,A6’s, Superbs) so not sure who advised you get one of those??? They only make them for transverse engine TDi’s.
Supersprint (Italian company) do appear to have an ‘off the shelf’ de-cat pipe under development, it is actually listed for Audi A4 but the exhausts are identical ;-)
http://www.supersprint.com/USP000auda430.aspAnyway, the cost is 230 euro + delivery for the supersprint pipe which in my opinion is pretty poor value considering the actual gains you get from it on an otherwise mechanically standard car.
The other option is to have one custom made in T304 Stainless which from experience will be the cheapest option provided you find somebody with good TIG skills who can make a Jig to get the flanges clocked correctly – there’s not a lot of room where the downpipe flange meets the start of the centre section making it extremely difficult to try and make it is situ – if they get it wrong you’ll have vibration issues as the flange itself sits less than an inch from the bottom of the bulkhead and needs to be spot on.
Anyway, back to my initial point:
For most people the negligible gains you will get from a de-cat on a TDi 130 are not worth the money/effort unless you are going to do some more substantial mods at which point the de-cat actually will be beneficial.
PROS:
SLIGHTLY (and I mean slightly) more area under the curve as far as torque goes – you can actually get more of a delta between hot and cold days LOL!
SLIGHTLY faster turbo spool up – Again this is borderline detectable using the seat of your pants. VNT17’s spool so quickly anyway you can go from 0 – 1.5Bar+ in no time at all with the Cat still in place!
SLIGHTLY reduced back pressure however the main ‘choke point’ in the 130TDI is not the CAT, it is 100% the VNT mechanism in the exhaust side of the turbocharger. That is why the limit for any VNT17 based hybrid turbo is around the 220HP mark. When we are going for more than that we have to use a custom made tubular exhaust manifold to allow us to fit something non VNT17 based ;-)
Interestingly, we’ve also logged EGT (exhaust gas temperature) on a previous extremely high power VE-Pump project – de-cat had no impact whatsoever on EGT’s – the only thing that significantly reduced EGT’s was water/methanol injection (Knocked nearly 300 deg off!) but that’s another story for another day ;-)
FYI: EGT is the single most important factor to monitor when tuning a diesel hard.
CONS:
COST – Significant considering the minimal gains.
Increased visible exhaust smoke – not been mentioned yet by anyone else but you will get increased visible smoke from the exhaust with the cat removed – not massive plumes and mainly on spool up but worth mentioning anyway.
So......... to reiterate my initial post – In my honest opinion based on personal and customers experiences a de-cat on an otherwise mechanically standard car isn’t worth the cost/effort.
I hope the above gives a good, unbiased overall picture of the pros and cons of fitting a de-cat pipe to a diesel. In addition to this I would welcome comments/experiences of others that have fitted de-cat pipes to their diesels and I’m sure we would all be very interested to have more detailed first hand experiences from others to help Adi make up his mind.
Also, FYI Adi we too have custom made software for various PD130 hardware configurations from mild to wild made by us on our own Dyno Dynamics rolling road.
Hope the above is useful to all,
Kind Regards,
Nick
www.carbon-chiptuning.co.uknick@carbonst.com
07825 215 003