Thursday, 22 February 2024 / Published in Carbon Clean with Walnuts, Engine Work, Fault Diagnosis

Audi S5 V8 Manual – Walnut Blast & Injector

The Audi S5 is a high-performance variant of the Audi A5 coupe, like all Audi “S” cars, they are only available with Audi’s quattro four-wheel drive (4WD) system, which in the S5 uses a Torsen-based centre differential. This example was particularly appealing as it featured a manual gearbox !

The Audi S5 is powered by a 4.2-liter V8 engine. This naturally aspirated engine produces 354 horsepower and 325 lb ft of torque. With the 6-speed manual transmission it provides a far more engaging driving experience for enthusiasts.

The first issue at hand was it was currently a V7 – we’d identified a misfire on Cylinder 3 that was clearly a failed injector (after confirming it wasn’t spark plug, coil pack or lack of compression). There’s no point firing the parts cannon until you know what is broken!

*Audi S5- severe oil leak from the o-rings under the oil filter housing*

It also had a rather nasty oil leak as you can see. It looks like the engine has rather hot in its life, and doesn’t look like it has received the requisite care and attention that a vehicle of this nature needs. The rubber O-rings that we replaced had degraded and turned hard and brittle.

audi v8 showing filter housing o-ring location — *Audi V8 showing filter housing o-ring location*

Next job was to walnut blast the intake valves and ports and clean the port dividers…

audi port before walnut blast — *Audi inlet port before walnut blast – pretty grim in there*

1 port divider cleaned - 7 more to go — *1 port divider cleaned – 7 more to go..*

audi port with port divider removed look at the amount of carbon — *Another Audi V8 port with port divider removed – look at the amount of carbon!*

clean port and valves — *That looks a whole lot better !*

a different port from a different angle — *A different port from a different angle – ready to flow some serious air..*

Just how much air did it flow? If the engine hadn’t been running on 7 cylinders when it came into us, we would have done a before and after airflow figure. Roughly speaking 10lb of air in 1 minute is 100HP. After cleaning this S5 recorded peak airflow of 40lb in 1 minute….roughly 400HP – we think judging by the way it goes it’s possibly been remapped and also has a free flow exhaust. It’s also possible the airflow meter is a little optimistic. For accurate HP figures a rolling road session will be required.

Customer is pleased with all the extra horsepower, unfortunately there is a slight oil leak remaining between the cam carrier and the head – this means oil is entering the spark plug well – to fix this means engine and gearbox out, and then gearbox split. While you’re at it you’d replace the cam chains which are at the back of the engine – no easy job..