I noticed on a previous post that GM makes a product (top Clean) to clean carbon from an engine. How would some one use this product on the 928? and would it be safe to use on our cars?

Dan 1990 928 GT

 

its injected into the engine through the fuel lines usually, sprayed in through the injectors, and left to sit for some amount of time, ive heard 2 hours or 12 hours depending on wether its a home application or shop doing it. You then run the car, get a bunch of black "crap" out of the exhaust and youve supposedly freed some of the carbon from the compustion chamber. I think this could be potentially fatal to a CAT but i have heard from others that its completely safe.

Ive heard mixed results doing this.

 

Thanks for that, I have no Cat's so I should be ok in that department , but what about the rest of the engine???


Dan 1990 928GT

 

Not even close. It can be poured the throttle body,drawn in through a vacuum hose or sprayed in the throttle body. There are two types spray and liquid. With the liquid it should sit for 15 to 20 mins.

 

I suspect that I am the originator of the "GM Top-end Cleaner" mentioned above from Blown87's TBF thread. The reference to the product is drawn from Another Forum wherein blown87 and I participate from time-to-time. Regardless, the GM product in question is injected down-stream of the Mass-Air Sensor; The MAS does not need that stuff on its itsy-bitsy wire. I cannot offer recommendations for how it is used on a 928 as I haven't BTDT (yet). However, I suspect that it should be drawn into the intake system via a breather hose under vacuum. On an S4 the line on the left side that runs around the throttle linkage assembly and provides vacuum to the vacuum reservoir is the most likely candidate.

As for 'safety' AFAIK the GM product, if injected down-stream of the MAS and used in a manner consistent with the directions I see no reason it should not be safe. The Other Forum's subject is a car with similar architecture and air/fuel system to the 928 (e.g. hot-wire MAS, etc.)