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    • Just how much does direct injection carbon buildup hurt? B7 RS4 gains 42 wheel horsepower after 034Motorsport carbon cleaning

      One of the downsides of direct injected motors is carbon buildup. Over time carbon builds up on the intake valves cluttering them up and having a detrimental effect on an engine's performance. Oil and fuel essentially gets on there and this creates a circular problem of more and more oil and fuel clinging to the deposits and the thickness of the deposits around the valves increases. Just how bad can this be? Just take look at how much material was removed from a B7 RS4.


      That is quite a bit of material, isn't it? There is no way anyone could expect an engine to function as it should with it being gunked up with that much carbon. This car had 69800 miles on it and did not have any aggressive modifications only a rear section exhaust and filter.

      As for the effect on performance, the baseline on a Mustang all wheel drive dyno before the cleaning showed 287 horsepower to the wheels and 240 pound-feet of torque to the wheels. After the cleaning these figures change to 329 horsepower and 266 pound-feet of torque. A night and day difference.

      There are measures that can be taken to minimize carbon buildup such as oil catch cans and methanol injection but this will be an issue no matter what and one owners of direct injected engines should monitor. A good cleaning can make the car feel like new especially if one gets the impression it has become sluggish over time.

      Valves before the cleaning:


      Valves after the cleaning:


      Dyno:

      This article was originally published in forum thread: Just how much does direct injection carbon buildup hurt? B7 RS4 gains 42 wheel horsepower after 034Motorsport carbon cleaning started by Sticky View original post
      Comments 25 Comments
      1. AlexQuattro's Avatar
        AlexQuattro -
        Click here to enlarge Originally Posted by leo985i Click here to enlarge
        The N54 is an engine that runs very very dirty too. My last N54 had to get cleaned at 50k cus it couldn't even do a pull at 13psi without coughing like a bad smoker leading to SES lights all the time. My 2nd N54 is up for a clean up, the car is now sitting at 61k miles, I can't even imagine how bad the valves look already, but this maintenance is not cheap, which sucks even more.
        Do you have a catch can?
      1. alex@ABRhouston's Avatar
        alex@ABRhouston -
        I've done about 100 N54 walnut blasts.

        We've done a dyno pull- left the car on the dyno, walnut blasted it and did another pull immediately afterwards.
        no change in power, just a curve shift. that was it.

        I've seen some REALLY nasty ones too…. super nasty.
      1. George Smooth's Avatar
        George Smooth -
        I may need to eat my words. I contacted some clients and asked for before and after dyno runs on the RS4 and the one had phenomenal results. Both cars are in the region of 90,000km with no prior clean.

        This is a stock car on a 4wd dyno power at the wheels 5600ft altitude.

        Attachment 36428
        This car is running decated exhaust system with software. Same altitude.

        Attachment 36429

        In regard to the N54 and turbo charged cars its a different kettle of fish. I will try dig up some graphs from the past. My findings with a stock car is the spool up is much quicker and boost target is met far sooner but its no task for the turbos to reach DME stock boost request albiet the car might get it a bit sooner. Timing is not affected.
        On high boost cars there is a big difference low down where boost request is usually at max and in some cases have seen as much as a 50nm gain in the lower rpm range i.e. below 3000rpm. High up once the target is met which is usually earlier its remains and the drop of is far slower at the high rpm. I have also noticed the car can hold more timing and a car that had previous drop outs sometimes the car can hold the power. I have a feeling this is due to the air getting poluted as it passes the carbon on the valve lowering in affect either the oxygen content of the air or created a "octane" affect.
        The best cars to do are the JB cars on autotune. The cars immediately request 1.5 psi and a large gains are found across the board.
      1. chrisisnapping's Avatar
        chrisisnapping -
        Click here to enlarge Originally Posted by fastgti69 Click here to enlarge
        I really need to get on this before the single or something. @alpinedevil335 This looks like a nightmare.
        i know steelcurtain had a "how to" on mk5/mk6 on carbon cleaning the TSI engine. i assume it's nearly identical to the n54, sans 2 cylinders.

        Lately 90% of my driving has been 1-5 miles, glad I have meth, but I still can't imagine what my valves will look like in another 20k.
      1. George Smooth's Avatar
        George Smooth -
        Click here to enlarge Originally Posted by chrisisnapping Click here to enlarge
        i know steelcurtain had a "how to" on mk5/mk6 on carbon cleaning the TSI engine. i assume it's nearly identical to the n54, sans 2 cylinders.

        Lately 90% of my driving has been 1-5 miles, glad I have meth, but I still can't imagine what my valves will look like in another 20k.
        Here is a TSI with a KO4 conversion. The TSI builds up slower than the TFSI although my findings have been similar in results regardless of what the build up looks like. The crusts around the rear of the port actually create a negative vortex reversing airflow either directly into the valve causing major turbulance. We must remember that we are flowing air only and not air that has atomised with fuel so its easier to affect the flow. This car has been running high boost most of its life so this decreases build up. I will try get a pic out of my archives with the valves open. Some TSI also have the ball that forms around the valve pretty low which drastically affects open valve port size as the valve opens and the ball moves directly in the opening.

        Attachment 36433

        Here is a stock Scirroco at 110,000km and it give you the difference of the affects of boost (see the fluffyness. In this pic you can see a piece getting ready to dislodge at 3 o clock on right valve.

        Attachment 36434