Detonation and broken piston rings
04-13-2002, 11:22 AM
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Detonation and broken piston rings
During a trip to Le Mans in France I damaged my newly renovated motor (20,000 Km) by driving fast 220 + Km/h (135 + M/h) during several hours in Germany and France.
I bought a 1984 car with a minor traffic damage from Switzerland with only 108,000 km on the clock, and installed this motor in my car.
The new motor is M28/22 with electronic injection (LH-Jetronic) and the old is M28/12 with mechanical injection (K-Jettronic)
Now I open the old motor:
Three pistons are damaged no 3,4 and 8 - I.e. the piston rings are broken, the upper one, broken into small pieces (down to 2 mm) and the pistons are broken in-between the rings in some places.
The cylinder no 4 has a tiny scratch, but not more than it will be possible to make a reasonable motor out of it (spare motor) if I get three new pistons.
No doubt, that's due to knocking (detonation).
In my new motor I installed the Devek modification (baffle) (standard from Porsche from model S4)- And I am now using Valvoline oil. (See the below Devek article)
Of course I want to find the reason, and think the theory from Devek can be the answer, but how can I be sure, and feel safe when driving fast in future?
I am very interested to hear from you if you have ideas or maybe same (bad) experience.
Regards from Erik in Denmark
928 S(2) - 1980/84 - Euro - Aut.
Copy from Devek technical support (You can see this on <a href="http://www.devek.net" target="_blank">www.devek.net</a>
The Devek theory:
Oil driven detonation: The 928's chronic oil lifting behaviour at higher rpms dumps oil into the induction system, causes smoke in the exhaust and, detonation of the engine at its peak output. That's because oil mixing with the injected fuel lowers the effective octane rating and hence the
detonation threshold. Detonation damages pistons, valves, and rings, and forces rebuilds before the 928's 200,000+ mile engine life has been ttained. Some racers use two-cycle engine oil in the crankcase because that oil is formulated to be burned and is specially blended to be compatible
with fuel.
The Fix:
Install DEVEK's oil control modifications at the next engine disassembly.
At the next oil change, fill with Red Line or Valvoline synthetic oils. Porsche tested a broad range of oils for fuel compatibility and found Valvoline synthetics to reduce detonation when mixed with fuel and burned in an internal combustion engine. The Red Line synthetic oils are
blended for compatibility with the higher octane fuels recommended for
Porsche engines.
techsupport@devek.net
I bought a 1984 car with a minor traffic damage from Switzerland with only 108,000 km on the clock, and installed this motor in my car.
The new motor is M28/22 with electronic injection (LH-Jetronic) and the old is M28/12 with mechanical injection (K-Jettronic)
Now I open the old motor:
Three pistons are damaged no 3,4 and 8 - I.e. the piston rings are broken, the upper one, broken into small pieces (down to 2 mm) and the pistons are broken in-between the rings in some places.
The cylinder no 4 has a tiny scratch, but not more than it will be possible to make a reasonable motor out of it (spare motor) if I get three new pistons.
No doubt, that's due to knocking (detonation).
In my new motor I installed the Devek modification (baffle) (standard from Porsche from model S4)- And I am now using Valvoline oil. (See the below Devek article)
Of course I want to find the reason, and think the theory from Devek can be the answer, but how can I be sure, and feel safe when driving fast in future?
I am very interested to hear from you if you have ideas or maybe same (bad) experience.
Regards from Erik in Denmark
928 S(2) - 1980/84 - Euro - Aut.
Copy from Devek technical support (You can see this on <a href="http://www.devek.net" target="_blank">www.devek.net</a>
The Devek theory:
Oil driven detonation: The 928's chronic oil lifting behaviour at higher rpms dumps oil into the induction system, causes smoke in the exhaust and, detonation of the engine at its peak output. That's because oil mixing with the injected fuel lowers the effective octane rating and hence the
detonation threshold. Detonation damages pistons, valves, and rings, and forces rebuilds before the 928's 200,000+ mile engine life has been ttained. Some racers use two-cycle engine oil in the crankcase because that oil is formulated to be burned and is specially blended to be compatible
with fuel.
The Fix:
Install DEVEK's oil control modifications at the next engine disassembly.
At the next oil change, fill with Red Line or Valvoline synthetic oils. Porsche tested a broad range of oils for fuel compatibility and found Valvoline synthetics to reduce detonation when mixed with fuel and burned in an internal combustion engine. The Red Line synthetic oils are
blended for compatibility with the higher octane fuels recommended for
Porsche engines.
techsupport@devek.net
04-21-2002, 03:36 PM
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Burning Brakes
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Dear all Porsche experts,
I am disappointed, after one week no answers or comments. Will taht means I am the only one with that problem?
Regards freom Erik in Denmark
I am disappointed, after one week no answers or comments. Will taht means I am the only one with that problem?
Regards freom Erik in Denmark
04-21-2002, 04:22 PM
#3
Erik,
I think no has given you feedback because your question is not an easy one nor is it a technical question. My best advise to you is make sure you have a working knock sensor in your engine.
Other than that, you sound as if you have solved your problem and taken the best steps to solve the issue. As far as making you feel more secure about your car, you might want to see a therapist because the 928 is not a Saturn and there will always be an unknown with any internal combustion engine and that unknown is especially pronounced with the 928.
Jim Nowak
I think no has given you feedback because your question is not an easy one nor is it a technical question. My best advise to you is make sure you have a working knock sensor in your engine.
Other than that, you sound as if you have solved your problem and taken the best steps to solve the issue. As far as making you feel more secure about your car, you might want to see a therapist because the 928 is not a Saturn and there will always be an unknown with any internal combustion engine and that unknown is especially pronounced with the 928.
Jim Nowak
04-21-2002, 04:37 PM
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Hi Jim,
Thank you for your response. Your advise with the knocking sensors is very good, but up to 1987 no knocking sensors on Euro cars - Maybe on US cars?
If you know how to install knocking sensor on 1984 Euro, I will be more than happy.
I visited all possible experts in Denmark and one in Germany, even I consulted Porsche factory.
Regards from Erik in Denmark
Thank you for your response. Your advise with the knocking sensors is very good, but up to 1987 no knocking sensors on Euro cars - Maybe on US cars?
If you know how to install knocking sensor on 1984 Euro, I will be more than happy.
I visited all possible experts in Denmark and one in Germany, even I consulted Porsche factory.
Regards from Erik in Denmark
04-21-2002, 06:54 PM
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Eric-
To the best of my recollection, the Knock Sensors are onbly installed on 87+ models (hence the EZ-K ignition designation).
I am curious as to how the rings became broken though. I guess I shoul'd take the time to re-read you original post.
To the best of my recollection, the Knock Sensors are onbly installed on 87+ models (hence the EZ-K ignition designation).
I am curious as to how the rings became broken though. I guess I shoul'd take the time to re-read you original post.
04-21-2002, 07:15 PM
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I used to have an 84 when I was living in Germany and I used to drive it from Munich to Hamburg every other week, which is a 950 km trip (~600 miles). My best time was about 4.5 hours, getting the speedometer over 280 kmh at times. I never had a problem. These cars are built to run at full throttle for a full tank of gas. BUT I used to fill it up with 97 octane "Super Verbleit" (leaded gas). I am not sure if leaded gasoline is still available in Europe. Running it hard on unleaded gas might cause you these problems without knock sensors.
regards,
Sab. <img src="graemlins/beerchug.gif" border="0" alt="[cheers]" />
regards,
Sab. <img src="graemlins/beerchug.gif" border="0" alt="[cheers]" />
04-22-2002, 02:36 AM
#7
Erik,
I'd have to agree with Jim Nowak.
There are an incredible number of things that can go WRONG with a sHARk engine and usually a couple of things will join forces to do us in.
Please check the Nichols site: <a href="http://nichols.nu/tips." target="_blank">http://nichols.nu/tips.</a> htm
Look under engine.
Really, it could be anyting from bad plug wires, faulty injectors, one of the dist. belts jumping torn regulator diaphragms, bad fuel, a hinkey brain, injector harness....
The best you can do is back track and try to find out what initiated the mess.
You could have been 'pinging' but at 135mph just didn't hear it.
Good luck and best wishes.
John S. & Pattycakes
I'd have to agree with Jim Nowak.
There are an incredible number of things that can go WRONG with a sHARk engine and usually a couple of things will join forces to do us in.
Please check the Nichols site: <a href="http://nichols.nu/tips." target="_blank">http://nichols.nu/tips.</a> htm
Look under engine.
Really, it could be anyting from bad plug wires, faulty injectors, one of the dist. belts jumping torn regulator diaphragms, bad fuel, a hinkey brain, injector harness....
The best you can do is back track and try to find out what initiated the mess.
You could have been 'pinging' but at 135mph just didn't hear it.
Good luck and best wishes.
John S. & Pattycakes
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04-22-2002, 09:56 AM
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Burning Brakes
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Jim, Jay, Sab and John
Thanks to all of you for your comments and advises:
Jim,
Correct, the question is not an easy one, but I believe some-one have the answer, and some-one have experience with the Devek baffle theory
I found one 'poor man' like me in Australia, but up to now I did not hear from him - See topic: Early 928 race engines from July 2001
Regarding the therapist, I visited several Porsche 928 experts who tested the car just after repair, and said OK
If the Devek theory is correct, the problem is, that comes suddenly - like a blitz - without overheating, and with top speed you cannot hear the knocking
Jay,
Yes you are right regarding the knock sensors was introduced in S4 model 1987
No dough, if you want drive fast with a 928 better to buy a 1987 + model with knocking sensors - But too expensive in Denmark due our tax level!
I will be happy for your comments after re-reading
Sab,
I think you are a man who are driving faster than me - 4,5 hours from Munich to Hamburg, that must have been many years ago or in the summer-night, today simply too many trucks on the highway in Germany!
But I am happy to hear that you did in a 1984 model - that what I have today after rebuilding.
Were it new when you made this world record?
You said "Super Verbleit" (leaded gas) - Now prohibited in Europe, they add MTBE to get the octane requirement + other additives for substitute of lead - Maybe that's some of the answer!
John,
I checked all these things as you mentioned, specially the second time I repaired the engine - Even the amount of gasoline per nozzle were checked, and the test result was sent to Porsche technical department in Germany.
But I missed to get it checked on a Dymo-meter, only I got it cheched on a Bosch rolling bench (Checking the CO all the way up, but without load)
I have a background as car mechanic when young, and later mechanical engineer and plus this I had some experts as consultants - But you are right many things can be the reason and I did not found the important one - But still I want to find it, and now I can do it relaxed, the old motor is only for 'my museum' and maybe spare if/when needed one day.
Remember the 1980 Euro model is with CIS - J-Jettronic mechanical injection
You are right at 135 mph you did not hear, maybe you can feel, but actually a freind of mine was the driver when happen, and was sitting beside.
I hope to get more input, and promise to send the answer - As a total story - if/when I find it
Regards from Erik in Denmark
Thanks to all of you for your comments and advises:
Jim,
Correct, the question is not an easy one, but I believe some-one have the answer, and some-one have experience with the Devek baffle theory
I found one 'poor man' like me in Australia, but up to now I did not hear from him - See topic: Early 928 race engines from July 2001
Regarding the therapist, I visited several Porsche 928 experts who tested the car just after repair, and said OK
If the Devek theory is correct, the problem is, that comes suddenly - like a blitz - without overheating, and with top speed you cannot hear the knocking
Jay,
Yes you are right regarding the knock sensors was introduced in S4 model 1987
No dough, if you want drive fast with a 928 better to buy a 1987 + model with knocking sensors - But too expensive in Denmark due our tax level!
I will be happy for your comments after re-reading
Sab,
I think you are a man who are driving faster than me - 4,5 hours from Munich to Hamburg, that must have been many years ago or in the summer-night, today simply too many trucks on the highway in Germany!
But I am happy to hear that you did in a 1984 model - that what I have today after rebuilding.
Were it new when you made this world record?
You said "Super Verbleit" (leaded gas) - Now prohibited in Europe, they add MTBE to get the octane requirement + other additives for substitute of lead - Maybe that's some of the answer!
John,
I checked all these things as you mentioned, specially the second time I repaired the engine - Even the amount of gasoline per nozzle were checked, and the test result was sent to Porsche technical department in Germany.
But I missed to get it checked on a Dymo-meter, only I got it cheched on a Bosch rolling bench (Checking the CO all the way up, but without load)
I have a background as car mechanic when young, and later mechanical engineer and plus this I had some experts as consultants - But you are right many things can be the reason and I did not found the important one - But still I want to find it, and now I can do it relaxed, the old motor is only for 'my museum' and maybe spare if/when needed one day.
Remember the 1980 Euro model is with CIS - J-Jettronic mechanical injection
You are right at 135 mph you did not hear, maybe you can feel, but actually a freind of mine was the driver when happen, and was sitting beside.
I hope to get more input, and promise to send the answer - As a total story - if/when I find it
Regards from Erik in Denmark
04-22-2002, 01:43 PM
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Eric,
The oiling issue only exists at 5800/6000+ rpm and is very dependent on the oil used. Some syntehtics are better than others and one company, Redline, admitted that their oil has a low octane rating, but would not elaborate.
The result of the oil ingestion is knocking and the expected result of light knock over time is broken top ring lands. We have seen it on both lightly supercharged and turbocharged engines.
The pistons are extrememly birttle, but they have very low CTE and run very tight clearences of .0008" piston to wall or .02mm.
Keep oil out of the intake, and you will have no problems.
Good luck,
Marc
DEVEK
The oiling issue only exists at 5800/6000+ rpm and is very dependent on the oil used. Some syntehtics are better than others and one company, Redline, admitted that their oil has a low octane rating, but would not elaborate.
The result of the oil ingestion is knocking and the expected result of light knock over time is broken top ring lands. We have seen it on both lightly supercharged and turbocharged engines.
The pistons are extrememly birttle, but they have very low CTE and run very tight clearences of .0008" piston to wall or .02mm.
Keep oil out of the intake, and you will have no problems.
Good luck,
Marc
DEVEK
04-22-2002, 05:07 PM
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Burning Brakes
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Marc,
Thank you for your useful comments - What you said that's exactly what happen, broken top rings and top rings lands.
Now I have installed the Devek oil baffle, using Valvoline synthetic oil (I have never seen Redline oil in Denmark) and rebuild my 1980 model to a 1984 model
The 1980 model's speed at 1000 RPM was app. 44 Km/h (28 mph) and the 1984 model's speed at 1000 RPM is app. 50 Km/h (48 mph)
I.e. 1980: 5800 RPM/1000 x 44 Km/h = 255 Km/h (160 mph) and 1984: 5800 RPM/1000 x 50 km/h = 290 Km/h (181 mph) - I.e. now I can never run above your max limit, due to the max speed of the car is app. 250 Km/h (156 mph)- And if the car can run faster, I will fell the 250 to be sufficient. And in lover gears, I will not go higher than app. 5500 - I promise!
Thank you for your comments, now I fell more confident.
Regards from Erik in Denmark
Thank you for your useful comments - What you said that's exactly what happen, broken top rings and top rings lands.
Now I have installed the Devek oil baffle, using Valvoline synthetic oil (I have never seen Redline oil in Denmark) and rebuild my 1980 model to a 1984 model
The 1980 model's speed at 1000 RPM was app. 44 Km/h (28 mph) and the 1984 model's speed at 1000 RPM is app. 50 Km/h (48 mph)
I.e. 1980: 5800 RPM/1000 x 44 Km/h = 255 Km/h (160 mph) and 1984: 5800 RPM/1000 x 50 km/h = 290 Km/h (181 mph) - I.e. now I can never run above your max limit, due to the max speed of the car is app. 250 Km/h (156 mph)- And if the car can run faster, I will fell the 250 to be sufficient. And in lover gears, I will not go higher than app. 5500 - I promise!
Thank you for your comments, now I fell more confident.
Regards from Erik in Denmark
05-22-2002, 11:36 AM
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Hi,
Just for up-dating you, what I am doing to prevent more problems with my engine, due to oil from the breathing system entering in-to the combusting chambers, lowering the octane ratio resulting in detonation and broken piston rings.
1. I already installed the Devek oil baffle
2. I am using Valvoline synthetic oil
Now I am doing/making/installing:
3. One more oil separator - A replica of the original cyclone
4. Evaluating the possibility of installing an Engine Knock Alert system from MSD (www.msdignition.com - look under tools) and connect this with an optocoupler unit to the EZF ignition computer, who has two small wires, who have to be connected, for driving with low octane gasoline - When connected, the ignition will be retarded app 3 degree (See shop manual page
28-64)
I will inform you, when I finished these two project (3 and 4)
Regards from Erik in Denmark
Just for up-dating you, what I am doing to prevent more problems with my engine, due to oil from the breathing system entering in-to the combusting chambers, lowering the octane ratio resulting in detonation and broken piston rings.
1. I already installed the Devek oil baffle
2. I am using Valvoline synthetic oil
Now I am doing/making/installing:
3. One more oil separator - A replica of the original cyclone
4. Evaluating the possibility of installing an Engine Knock Alert system from MSD (www.msdignition.com - look under tools) and connect this with an optocoupler unit to the EZF ignition computer, who has two small wires, who have to be connected, for driving with low octane gasoline - When connected, the ignition will be retarded app 3 degree (See shop manual page
28-64)
I will inform you, when I finished these two project (3 and 4)
Regards from Erik in Denmark
