159 Cruiser and
AO Silver Member
Join Date: Jul 2012
Location: United Kingdom
Both cause a drop in power/ response/ economy.
The EGR works by recyling exhaust gas through the engine. This gas is burnt fuel, and so low in oxygen. This means the freshly injected fuel will burn less efficently (however, it will result in lower NOX emissions which is its primary aim, this chemical reaction takes some of the energy from the burning process), meaning you will need more fuel to create the same energy (i.e reducing fuel efficiency). The air going into the engine will also be warmer, again reducing the o2 content, and reducing efficiency/ power!
The EGR also takes it's gas just before the turbo, meaning that the turbo takes longer to spool up, and is less efficient, again costing you . In the US truck industry, EGR introduction was directly related to a 3% drop in efficiency (against an average annual increase of 0.5%!)
Furthermore!!!! By putting soot through the system, it actually increases the soot production ( as soot forms on existing particles more easily), so it will also increase the likelyhood of DPF issues! The EGR not only clogs up the engine long term (which will reduce engine efficiency more, changes air flows, jammed EGRs etc), but will cause damage to the engine itself due to soot (eg broken swirl flaps).
The DPF slows the exhaust gasses leaving the engine, which in turn reduces the efficiency of the turbo (imagine blocking a hairdryer, will have the same effect), reducing the amount of power produced by the turbo, and reducing the 02 going into the engine.
So the DPF will reduce performance and efficiency during 'normal' operation.
Even more importantly, as you will be aware, the DPF regens by pumping unburnt fuel down the exhuast (injected during the non burning stroke of the engine), during this, you will see your MPG drop by at least 10MPG for 10mins or so, I reckon this reduces my MPG per tank by at least 2mpg.
The EGR was introduced in order to reduce Nox emissions, the by product of which was reduced MPG and increased soot production, which was resolved by introducing the DPF, which further reduced performance! My personal thoughts are you could probably get at least 5bhp (on the 1.9) more just by removing these two parts (especially below 2,000rpm, where almost all are reporting improved performance with blanking plates!).
Edit: Just realised the 5bhp works out at ~3%....the reduction in efficiency recorded in the US by the introduction of EGRs!
159 1.9JTDM Ti and Giulietta 2.0 Veloce
ex: Punto 55s, Golf Mk5 1.4FSi, A3 (8P) Sportback 2.0TDi SE, A4 (B8) 2.0TDI S-Line, 306 HDI Meridian
Last edited by giblets46; 12-06-13 at 16:04.