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2.5 TFSi engine tuning

Guide to the VAG 2.5 TFSi engine

The 2.5 TFSi is the VAG Group 5 Cylinder turbo engine, as fitted to the TTRs RS3 TSQ3 and the Quattro concept.

Voted engine of the year 5 times in a row (2015) we start to see that this is a very special engine indeed. It is a chain driven DOHC, with variable valve timing.

The Block is aluminum Alloy with a DJV-450 vermicular graphite cast iron cylinder block. The firing order is 1-2-4-5-3 and it runs at a 10.0:1 compression ratio thanks to the knock resistant inlet design and direct fuel injection.

These blocks were designed to tolerate power figures in the region of 700bhp so make a great base for a tuning project.

FSi injection running at upto 1770psi on a common rail. The ECU is a Bosch Motronic MED unit and it uses two knock sensors, allowing it to manage each cylinder separately.

Engine Codes CEPA on the early engines, later engines from mid 2011 were CEPB.

CEPA in Aug 2010 had some revisions to the engine crankcase, new pistons, sealing flange and oil spray jets.

355bhp 332lb-ft - RS3 TTRS
355 bhp & 343 lb-ft TTRS plus
306bhp 343lb-ft - RS Q3
363bhp  343 lb-ft RS3 from 2015

Interestingly VAG managed to squeeze 402bhp and 354 lbf-ft from this engine in the Audi Quattro concept.

Many of our forum members report that gains of 70bhp are possible with just a remap alone, combine this with a turbo upgrade and you'll have a potent engine.

Upgrading the downpipe will allow the turbo to spool up more quickly and releases some extra HP. The GTX3576R works well on this engine, allowing you to see a 100bhp+ power gain on standard low octane fuel. There is an APR conversion around which wil realise 665bhp on 104RON fuel!

ttrs-engine

When upgrading to the GTX3576R turbo you should add a higher pressure fuel pump, uprate the intercooler and we would also recommend some exhaust upgrades namely a high flow downpipe and sports catalyst. There may be additional pipe/mounting point work required to site this turbo depending on whether you purchase it in a kit for the 2.5TFSi.

These engines really do appreciate high octane fuel, timing, fueling etc are adjusted to fully realize the potential of the higher octane and you will see more power and greater economy. For most drivers the extra miles per tank will cover the cost of the higher price of the fuel.

Problems and issues

Carbon build up is still an issue on these engines, although significant improvements have been made. Avoid problems by using good quality fuel, adding a good quality cleaner to your fuel like BG44K and run the engine hot and use the full RPM range when warm. You should get over 70,000 miles on an engine before carbon build up can cause a problem on these although if you only do short runs this will happen much sooner.

When there is significant carbon build up you'll lose power and a full intake clean will restore this lost power immediately.

There was  brake squeal recall in 03/2013 where a modified brake caliper has removed this issue.

Please submit your tuning tips, comments and details of common faults below so we can update this article and keep it current.

To discuss tuning these and the full range of VAG engines in more detail please join our very friendly international car forums.

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