mytrplseven

Just got off the net with Bill Burris, the 944 tech expert with Panorama magazine and as we were discussing halting acceleration issues, he mentioned that Porsche has a procedure using crushed walnut shells to blast carbon build-up off of the exhaust valves.

I called my local dealership about it and since the girl at the desk was new and not totally adept on stuff like this, she's going to look into it and call me back.

Anyone out there familiar with this process and to what extent the engine is disassembled to do it. It's supposed to be done with the head still attached but not sure if the entire intake has to come off or just the throttle body.

Verrry Interesting, Ja?

SpeedyC2

AFAIK, this is a somewhat common practice (maybe pioneered by BMW?) particularly used to clean carbon deposits off valves in DFI engines, where this issue can be a problem.

I don't know the extent of disassembly required.

pontifex4

I soda blasted mine. It was slow work, though. Walnut shell would have been a better media.

42 yrs w/porsche

Audi used the same procedure on all their 5000 models that had hesitation problems back in the late 80's. After removing the intake manifold there was a device that bolted to the head, air pressure was applied and the back of the valves were blasted. It had a positive effect but I would think you could accomplish the same thing by adding BG 44K to a couple of tankfuls of gas. My 2 cents.--Dave

Taymar

I believe the BMW and MINI tool attaches right to the individual intake port, and has a small hole for the media blast wand and a larger fitting further back to hook up a shop vac or vacuum source to extract the used media and carbon.

I'm wondering if it might be difficult to get good enough access to the exhaust ports of a 944 if the engine is still installed in the car (assuming you'd be blasting the exhaust valves via the exhaust ports). I would think with a blast wand made to the right shape it could work though.

I think the buildup on the DI cars deals with the intake valves since they don't have fuel constantly washing the deposits off the valves. I'm not sure how much more stubborn (if any)the carbon on an exhaust valve would be.

pontifex4

I should have clarified that I removed the head to clean my valves.

mytrplseven

I read your notes and did about an hour of research on this stuff including comparisons with Redline, Seafoam, Techron, etc. and the reviews were eye-opening. I ordered two cans off Ebay, since no-one around here sells it over the counter. One can should suffice for two tankfuls of gas on the Porsche and the other for my rough idling Dodge Truck (which I can't seem to fix, either). Thanks in advance for your info.

MAGK944

The thing that concerns me with all these bottled chemical cleaners is what happens to all the carbon? It has to go somewhere. I can imagine that the stuff works however I would rather the carbon stays stuck where it is rather than being loosened and flying around the combustion chambers.

Dougs951S

Its gets burned and goes out the exhaust, I would assume?

MAGK944

Yes I'm sure that's where it ends up after it has been worked loose from the piston and lodged itself in the top ring and scored your cylinders for a while.

Sorry but I'm not convinced.

Voith

Deposits do not burn. Carbon deposit is the hardest material known to me.

MAGK944

Yep, diamonds are carbon and are the hardest material known, but black carbon is still right up there, about twice the hardness of aluminum. It will f#ck your engine if you let it loose in there. imo best leave it there undisturbed and clean it off next time the engine is rebuilt or when the head comes off.

mytrplseven

From what I've ascertained from other posts online regarding the BG 44K cleaner is that the carbon doesn't come off in pieces. It seems to slowly liquify and slowly ablates away. One poster poured a little on a piston head that was carboned up and the next day he hosed the stuff off like it was a liquified sheen and not in pieces. Interesting stuff and from all I read, there were no negative reviews, but a bunch of enthusiastic comments based on positive results. Hopefully, that'll prove the answer to my acceleration issues. I've replaced everything else chasing this problem.

V2Rocket

Take your car out and drive the p*ss out of it for a few hours and most of the carbon should be taken care of.

This reminds me of the GM tech bulletin about oil consumption on the Northstar engines...old ladies would drive the car at 6mph and never go above 2000rpm and the rings would basically stick in place from carbon buildup. The Cadillac recommendation to the techs was "drive the car for an hour or so and give it WOT several times for extended acceleration periods" to unstick things and burn it off.

bonus12

I havent used seafoam on my 944 but I think it dissolves carbon deposits, kind of like acetone dissolves lacquer. I can't see how it would dislodge dangerous chunks. Isnt seafoam made of acetone anyway? ...can't quite remember. Besides, auto stores sell as much seafoam as paint wax, and no cylinder scoring has been reported.