Walnut shell blasting.
08-27-2018, 12:40 PM
#1
Three Wheelin'
Thread Starter
Walnut shell blasting.
Has anyone tried walnut blasting to de-carbonize their 997 ? I just wonder if its feasible as a DIY procedure with the appropriate equipment.
08-27-2018, 01:14 PM
#2
Drifting
I know this is a common fix for BMW DI engines, but I haven't heard about our Porsche DI engines having problems with carbon build up. I am curious--are you having issues with build-up?
If so, what are the issues and how do they present? What is your mileage, details on your car, etc.?
If so, what are the issues and how do they present? What is your mileage, details on your car, etc.?
08-27-2018, 01:26 PM
#3
Three Wheelin'
Thread Starter
My is a 997.2 CS2 with 50K miles. I haven't had any symptoms of carbon buildup, but from reading all the post regarding HPFI engines, it seems to be a common issue. As part of the regular maintenance right after I bought the car, I changed the spark plugs and coils. There were no history of the spark plugs were ever changed so I examined the old plugs and at 40K miles, they were in very good condition. No oily deposits, no carbon buildups, just a coating of greyish color that only a heathy engine gives. However, I do get a bit of sooty tailpipe on the left and from all I've read it seems normal. My curiosity on the walnut shell blasting is just to be aware of what it takes. I dd t to my BMW e90, aided by some video it was not difficult at all and the result was spiffy clean on the intake system. However, on the Porsche there is hardly any information whether it is recommended or how to go about doing it.
08-27-2018, 02:17 PM
#4
This is not something that is done on Porsche Carrera 997.2.
These cars are not built in the same way as BMW or AUDIs, which are both notorious for requiring a clean-up every 30K miles or so.
Refrain from doing it, and enjoy your car. To understand why, try to find a drawing showing the Direct Fuel injection system on a Carrera. It may explain why this is not required.
Yves
These cars are not built in the same way as BMW or AUDIs, which are both notorious for requiring a clean-up every 30K miles or so.
Refrain from doing it, and enjoy your car. To understand why, try to find a drawing showing the Direct Fuel injection system on a Carrera. It may explain why this is not required.
Yves
08-27-2018, 03:01 PM
#5
Drifting
Of course, since you don't have to worry about carbon fouling, I'll mention that a sooty tailpipe is sometimes a symptom of a faulty air/oil separator or scored bore--which are both occasional issues with our cars.
I didn't want to leave you with nothing to worry about.
Then again, sooty tailpipes are common with our cars and the best fix is soapy water and a wash mitt--so don't worry unless you have to.
I didn't want to leave you with nothing to worry about.
Then again, sooty tailpipes are common with our cars and the best fix is soapy water and a wash mitt--so don't worry unless you have to.
08-27-2018, 04:09 PM
#7
SO! You want to deal with de-carbonizing your direct injection motor! Congratulations!
You now hate life itself.
The issue with DI is that the top of the valves do not get fuel wash, leading to excessive carbon build up. This is caused specifically by the feed from the EGR (Exhaust Gas Recirculation) system, which feeds exhaust back into the intake path. Without fuel wash, these elements do not get burned off as they would in MPFI cars. If your car is running well with no problems and no random misfires, the wisest thing to do is to just leave it alone. Seriously. Do NOT mess with it. SERIOUSLY. Porsche engines are subject to the exact same problems as everyone else, this is a fact. HOWEVER, if the resultant exhaust gases do not contain the right mix of elements, or do not land on the valves certain ways, you do not have coking problems. Simple as that. If the EGR gases contain only trace amounts of carbon and silica and other stuff (it's a scientific term,) then you don't have carbon coking build up at the same rate, and you don't need to clean the top end. Certain manufacturers just went "eh, whatever, who cares we can cheat emissions with it this way" and dump just... the worst crap possible.
If you aren't symptomatic, just don't do it.
Now that said, you specifically asked about walnut shell blasting. My response to that is: please don't. Does it work? Sure. Does it cause more headache than it's worth? Oh hell yes. The best solution for a top end clean is to follow the manufacturer recommendations for a heavy-duty solvent based cleaning agent. In other words: if Porsche says "use our top-end cleaner," use only theirs. Do not use Seafoam (it is not a solvent) do not pour crap in your tank (won't get there anyway) do not spray random chemicals down the throat. Do. What. The. Manufacturer. Says. This will also be significantly cheaper, because it's performed without taking off any part that is not strictly necessary and the engine in the car.
The main reason Porsche doesn't have much information on it, is because A) this is not something you should do yourself generally, because seriously. Solvents. Nasty ones that eat electrical parts and sensors in addition to carbon. B) There simply isn't a need for it often enough. Onyxia doesn't need it at 60k, so you definitely don't at 40k. Some DI systems can go 100k+ before carbon build-up is meaningful.
edit: Drawing of Porsche system, very helpful, but glosses over things significantly. Fuel spray on top of the valve = bad because less fuel in cylinder = less power. So you don't get the wash you do versus MPFI (where the injector is located above the valve so all fuel travels over it.) You also do not get wash on the exhaust valve, but, this is not a bad thing generally. The exhaust is less sensitive to it (because duh.) The real advantage is in a different EGR mix, lower EGR rate, better airflow over the valve (basically not letting stuff settle on it,) adding up to a better fuel-air mix and more complete combustion including the harmful crap (scientific term!)
You now hate life itself.
The issue with DI is that the top of the valves do not get fuel wash, leading to excessive carbon build up. This is caused specifically by the feed from the EGR (Exhaust Gas Recirculation) system, which feeds exhaust back into the intake path. Without fuel wash, these elements do not get burned off as they would in MPFI cars. If your car is running well with no problems and no random misfires, the wisest thing to do is to just leave it alone. Seriously. Do NOT mess with it. SERIOUSLY. Porsche engines are subject to the exact same problems as everyone else, this is a fact. HOWEVER, if the resultant exhaust gases do not contain the right mix of elements, or do not land on the valves certain ways, you do not have coking problems. Simple as that. If the EGR gases contain only trace amounts of carbon and silica and other stuff (it's a scientific term,) then you don't have carbon coking build up at the same rate, and you don't need to clean the top end. Certain manufacturers just went "eh, whatever, who cares we can cheat emissions with it this way" and dump just... the worst crap possible.
If you aren't symptomatic, just don't do it.
Now that said, you specifically asked about walnut shell blasting. My response to that is: please don't. Does it work? Sure. Does it cause more headache than it's worth? Oh hell yes. The best solution for a top end clean is to follow the manufacturer recommendations for a heavy-duty solvent based cleaning agent. In other words: if Porsche says "use our top-end cleaner," use only theirs. Do not use Seafoam (it is not a solvent) do not pour crap in your tank (won't get there anyway) do not spray random chemicals down the throat. Do. What. The. Manufacturer. Says. This will also be significantly cheaper, because it's performed without taking off any part that is not strictly necessary and the engine in the car.
The main reason Porsche doesn't have much information on it, is because A) this is not something you should do yourself generally, because seriously. Solvents. Nasty ones that eat electrical parts and sensors in addition to carbon. B) There simply isn't a need for it often enough. Onyxia doesn't need it at 60k, so you definitely don't at 40k. Some DI systems can go 100k+ before carbon build-up is meaningful.
edit: Drawing of Porsche system, very helpful, but glosses over things significantly. Fuel spray on top of the valve = bad because less fuel in cylinder = less power. So you don't get the wash you do versus MPFI (where the injector is located above the valve so all fuel travels over it.) You also do not get wash on the exhaust valve, but, this is not a bad thing generally. The exhaust is less sensitive to it (because duh.) The real advantage is in a different EGR mix, lower EGR rate, better airflow over the valve (basically not letting stuff settle on it,) adding up to a better fuel-air mix and more complete combustion including the harmful crap (scientific term!)
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08-27-2018, 06:06 PM
#8
RL Community Team
Rennlist Member
Rennlist Member
2009 C2S 127K miles
I have never heard of anyone needing or getting any treatment to clear the backsides of their valves. Lotsa speculation as to why Porsche engines don't need it, but no one really knows. I am kinda surprised given all I read about DFI engines in general, but these cars are 9-10 years old now... and nothing.
Peace
Bruce in Philly
I have never heard of anyone needing or getting any treatment to clear the backsides of their valves. Lotsa speculation as to why Porsche engines don't need it, but no one really knows. I am kinda surprised given all I read about DFI engines in general, but these cars are 9-10 years old now... and nothing.
Peace
Bruce in Philly
08-27-2018, 09:21 PM
#9
What Bruce (and others) said. 116K miles on mine with only standard maintenance and still going strong. Just drive and enjoy.
08-28-2018, 10:36 AM
#11
Three Wheelin'
Join Date: Mar 2010
Location: Calgary, Alberta
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2009 C2S 127K miles
I have never heard of anyone needing or getting any treatment to clear the backsides of their valves. Lotsa speculation as to why Porsche engines don't need it, but no one really knows. I am kinda surprised given all I read about DFI engines in general, but these cars are 9-10 years old now... and nothing.
Peace
Bruce in Philly
I have never heard of anyone needing or getting any treatment to clear the backsides of their valves. Lotsa speculation as to why Porsche engines don't need it, but no one really knows. I am kinda surprised given all I read about DFI engines in general, but these cars are 9-10 years old now... and nothing.
Peace
Bruce in Philly
08-28-2018, 01:11 PM
#12
Three Wheelin'
Thread Starter
Thanks for all the inputs. I guess the need for de-carbonizing the DFI engine is not an issue. I'll take the advice to leave it alone.
08-28-2018, 06:29 PM
#13
SO! You want to deal with de-carbonizing your direct injection motor! Congratulations!
You now hate life itself.
The issue with DI is that the top of the valves do not get fuel wash, leading to excessive carbon build up. This is caused specifically by the feed from the EGR (Exhaust Gas Recirculation) system, which feeds exhaust back into the intake path. Without fuel wash, these elements do not get burned off as they would in MPFI cars. If your car is running well with no problems and no random misfires, the wisest thing to do is to just leave it alone. Seriously. Do NOT mess with it. SERIOUSLY. Porsche engines are subject to the exact same problems as everyone else, this is a fact. HOWEVER, if the resultant exhaust gases do not contain the right mix of elements, or do not land on the valves certain ways, you do not have coking problems. Simple as that. If the EGR gases contain only trace amounts of carbon and silica and other stuff (it's a scientific term,) then you don't have carbon coking build up at the same rate, and you don't need to clean the top end. Certain manufacturers just went "eh, whatever, who cares we can cheat emissions with it this way" and dump just... the worst crap possible.
If you aren't symptomatic, just don't do it.
Now that said, you specifically asked about walnut shell blasting. My response to that is: please don't. Does it work? Sure. Does it cause more headache than it's worth? Oh hell yes. The best solution for a top end clean is to follow the manufacturer recommendations for a heavy-duty solvent based cleaning agent. In other words: if Porsche says "use our top-end cleaner," use only theirs. Do not use Seafoam (it is not a solvent) do not pour crap in your tank (won't get there anyway) do not spray random chemicals down the throat. Do. What. The. Manufacturer. Says. This will also be significantly cheaper, because it's performed without taking off any part that is not strictly necessary and the engine in the car.
The main reason Porsche doesn't have much information on it, is because A) this is not something you should do yourself generally, because seriously. Solvents. Nasty ones that eat electrical parts and sensors in addition to carbon. B) There simply isn't a need for it often enough. Onyxia doesn't need it at 60k, so you definitely don't at 40k. Some DI systems can go 100k+ before carbon build-up is meaningful.
edit: Drawing of Porsche system, very helpful, but glosses over things significantly. Fuel spray on top of the valve = bad because less fuel in cylinder = less power. So you don't get the wash you do versus MPFI (where the injector is located above the valve so all fuel travels over it.) You also do not get wash on the exhaust valve, but, this is not a bad thing generally. The exhaust is less sensitive to it (because duh.) The real advantage is in a different EGR mix, lower EGR rate, better airflow over the valve (basically not letting stuff settle on it,) adding up to a better fuel-air mix and more complete combustion including the harmful crap (scientific term!)
You now hate life itself.
The issue with DI is that the top of the valves do not get fuel wash, leading to excessive carbon build up. This is caused specifically by the feed from the EGR (Exhaust Gas Recirculation) system, which feeds exhaust back into the intake path. Without fuel wash, these elements do not get burned off as they would in MPFI cars. If your car is running well with no problems and no random misfires, the wisest thing to do is to just leave it alone. Seriously. Do NOT mess with it. SERIOUSLY. Porsche engines are subject to the exact same problems as everyone else, this is a fact. HOWEVER, if the resultant exhaust gases do not contain the right mix of elements, or do not land on the valves certain ways, you do not have coking problems. Simple as that. If the EGR gases contain only trace amounts of carbon and silica and other stuff (it's a scientific term,) then you don't have carbon coking build up at the same rate, and you don't need to clean the top end. Certain manufacturers just went "eh, whatever, who cares we can cheat emissions with it this way" and dump just... the worst crap possible.
If you aren't symptomatic, just don't do it.
Now that said, you specifically asked about walnut shell blasting. My response to that is: please don't. Does it work? Sure. Does it cause more headache than it's worth? Oh hell yes. The best solution for a top end clean is to follow the manufacturer recommendations for a heavy-duty solvent based cleaning agent. In other words: if Porsche says "use our top-end cleaner," use only theirs. Do not use Seafoam (it is not a solvent) do not pour crap in your tank (won't get there anyway) do not spray random chemicals down the throat. Do. What. The. Manufacturer. Says. This will also be significantly cheaper, because it's performed without taking off any part that is not strictly necessary and the engine in the car.
The main reason Porsche doesn't have much information on it, is because A) this is not something you should do yourself generally, because seriously. Solvents. Nasty ones that eat electrical parts and sensors in addition to carbon. B) There simply isn't a need for it often enough. Onyxia doesn't need it at 60k, so you definitely don't at 40k. Some DI systems can go 100k+ before carbon build-up is meaningful.
edit: Drawing of Porsche system, very helpful, but glosses over things significantly. Fuel spray on top of the valve = bad because less fuel in cylinder = less power. So you don't get the wash you do versus MPFI (where the injector is located above the valve so all fuel travels over it.) You also do not get wash on the exhaust valve, but, this is not a bad thing generally. The exhaust is less sensitive to it (because duh.) The real advantage is in a different EGR mix, lower EGR rate, better airflow over the valve (basically not letting stuff settle on it,) adding up to a better fuel-air mix and more complete combustion including the harmful crap (scientific term!)