Start to Finish: Building Our 50' Skater
11-19-2017, 10:13 PM
#1371
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How can you consider it lean? It is purely throttled by fuel. Take away fuel and power and rpm decreases. In a mechanical diesel the only thing that increases or decreases power and rpm is the amount of fuel injected. When you let off you're leaning it out to slow the engine down.
ive tuned many many duramaxes, several 5.9 and 6.7 cummins, add fuel egts go up, reduce timing egts go up, quite the opposite of a typical gas engine.
my own duramax made over 850hp with over 100lbs of boost, I could've redone the turbos and heads to make better use of the airflow and reduced pressure but it did everything I wanted and never "leaned out"
ive tuned many many duramaxes, several 5.9 and 6.7 cummins, add fuel egts go up, reduce timing egts go up, quite the opposite of a typical gas engine.
my own duramax made over 850hp with over 100lbs of boost, I could've redone the turbos and heads to make better use of the airflow and reduced pressure but it did everything I wanted and never "leaned out"
Last edited by Unlimited jd; 11-19-2017 at 10:20 PM.
11-19-2017, 10:19 PM
#1372
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How can you consider it lean? It is purely throttled by fuel. Take away fuel and power and rpm decreases. In a mechanical diesel the only thing that increases or decreases power and rpm is the amount of fuel injected. When you let off you're leaning it out to slow the engine down.
11-19-2017, 11:01 PM
#1373
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I don't know diesel (so, excuse this if you want
) but I do know they typically use piston oil squirters and I do know if the squirters aren't spraying enough oil then the pistons can overheat and melt pretty much like like a gas piston can from a lean a/f. Also, I'm sure fueling issues (timing of spray, inproper spray, etc) could cause this too...but....new motors right ?
) but I do know they typically use piston oil squirters and I do know if the squirters aren't spraying enough oil then the pistons can overheat and melt pretty much like like a gas piston can from a lean a/f. Also, I'm sure fueling issues (timing of spray, inproper spray, etc) could cause this too...but....new motors right ?
11-20-2017, 05:21 AM
#1374
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I'm no diesel mechanic, but i have played with my duramax a bit.
My understanding is you'd be building heat and ruining a piston possibly from a rich condition rather than lean.... a lean condition just equals loss of fuel and less power.
I dont think boost matters in the equation up until the point the parts cant handle the strain.
im glad to hear you didn't completely ruin the thing
keep at it, you'll get it.
My understanding is you'd be building heat and ruining a piston possibly from a rich condition rather than lean.... a lean condition just equals loss of fuel and less power.
I dont think boost matters in the equation up until the point the parts cant handle the strain.
im glad to hear you didn't completely ruin the thing
keep at it, you'll get it.
11-20-2017, 07:43 AM
#1375
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I have had this conversation with people before when they told me they leaned out a diesel and I said it cant be done. A diesel is know as a lean burn engine. That is the whole reason we are using them instead of a gas engine. It is not for the "reliability" of the diesel (so far none of the ones I have had built have lived yet) But the whole reason we are using them is because of them burning lean, getting good fuel mileage. That being said I have thought about it for the last couple of hours and I will change my stance on that you cannot lean out a diesel and I will say that yes you can lean it out too much. I know this will start a **** storm, but after thinking about it for a few hours I'm sure that it is possible to run my engine lean enough to burn up the pistons. I'm not saying that is what caused our problem because were not sure yet, but when its put back together we will find out.
Before people start fighting about that you cant lean out a diesel I will say that 99.99% of the diesels ever made you probably could not lean out enough to cause a problem and that any old time diesel mechanic that has worked on diesels for 100 years would probably fight till there death saying you could not lean out a diesel, but I like to think outside the box and I will say that with today's technology you can lean out a diesel to the point of melting pistons.
I have looked all over the internet on diesel forums and pretty much all of them say you cannot lean out a diesel. I am really going out on a limb here and I'm going to say all those people on all those forums are wrong. I know that in theory if you lean out a diesel you are just pulling throttle back and not making as much power but i will say that you can lean out a diesel and have the temp increase. But who do you "call" to find out? Who do you trust there answer? Just because they have built diesels for 100 years would mean nothing to me on if they are right or wrong. It just means they have lots of experience with what they have done but not that they know about something they have never tried.
So here is the question, who do we call to find out if you can lean out a diesel to the point of melting pistons?
Before people start fighting about that you cant lean out a diesel I will say that 99.99% of the diesels ever made you probably could not lean out enough to cause a problem and that any old time diesel mechanic that has worked on diesels for 100 years would probably fight till there death saying you could not lean out a diesel, but I like to think outside the box and I will say that with today's technology you can lean out a diesel to the point of melting pistons.
I have looked all over the internet on diesel forums and pretty much all of them say you cannot lean out a diesel. I am really going out on a limb here and I'm going to say all those people on all those forums are wrong. I know that in theory if you lean out a diesel you are just pulling throttle back and not making as much power but i will say that you can lean out a diesel and have the temp increase. But who do you "call" to find out? Who do you trust there answer? Just because they have built diesels for 100 years would mean nothing to me on if they are right or wrong. It just means they have lots of experience with what they have done but not that they know about something they have never tried.
So here is the question, who do we call to find out if you can lean out a diesel to the point of melting pistons?
11-20-2017, 09:19 AM
#1376
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I could see it running lean and melting pistons, I don't have a ton of experience with common rails but when we were into pulling trucks a few years ago (all 12V cummins) we would see a drop in EGT's just by putting in too large of an injector. this made no extra power and a ton of extra smoke but was something we used to lower EGT's. obviously you wouldn't want this on a boat but makes sense that less fuel could make more heat and melt pistons.
11-20-2017, 01:58 PM
#1377
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PAGE 130
(We had the low tune in the engine and it ran 103 MPH, was still gaining but we were in the little lake so did not have a lot of room.)
If the low tune has melted pistons so quickly there is no way these engines will make 1300 hp and hold together.
As I previously mentioned in this thread your water flow looks two restrictive and your heat exchanger looks way to small.
Did you have any data logging running at the time of failure?
What was the following:
Intake temps
Fuel timing advance
Water pressure and flow
To put this into perspective my Seatek 800-1200hp water flow is 250L/min through 2" pickups, strainers and hoses.
The heat exchanger/charge cooler core is 28"long and 9" diameter, Jabsco pump has a 4 1/2" impeller.
These high HP diesels need a lot more water to cool them than the equivalent gas motor.
(We had the low tune in the engine and it ran 103 MPH, was still gaining but we were in the little lake so did not have a lot of room.)
If the low tune has melted pistons so quickly there is no way these engines will make 1300 hp and hold together.
As I previously mentioned in this thread your water flow looks two restrictive and your heat exchanger looks way to small.
Did you have any data logging running at the time of failure?
What was the following:
Intake temps
Fuel timing advance
Water pressure and flow
To put this into perspective my Seatek 800-1200hp water flow is 250L/min through 2" pickups, strainers and hoses.
The heat exchanger/charge cooler core is 28"long and 9" diameter, Jabsco pump has a 4 1/2" impeller.
These high HP diesels need a lot more water to cool them than the equivalent gas motor.
11-20-2017, 02:47 PM
#1378
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If there is a way to do it, EGT probes on each cylinder, like an airplane, and you will see problems before they cause issues. Maretron makes hardware that can read all the sensors and put the data on a NMEA network, or maybe even easier to adapt some aircraft gauges that are made for 6 cyl engines. Just a thought I don't claim to be an expert.
11-20-2017, 08:19 PM
#1379
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I have had this conversation with people before when they told me they leaned out a diesel and I said it cant be done. A diesel is know as a lean burn engine. That is the whole reason we are using them instead of a gas engine. It is not for the "reliability" of the diesel (so far none of the ones I have had built have lived yet) But the whole reason we are using them is because of them burning lean, getting good fuel mileage. That being said I have thought about it for the last couple of hours and I will change my stance on that you cannot lean out a diesel and I will say that yes you can lean it out too much. I know this will start a **** storm, but after thinking about it for a few hours I'm sure that it is possible to run my engine lean enough to burn up the pistons. I'm not saying that is what caused our problem because were not sure yet, but when its put back together we will find out.
Before people start fighting about that you cant lean out a diesel I will say that 99.99% of the diesels ever made you probably could not lean out enough to cause a problem and that any old time diesel mechanic that has worked on diesels for 100 years would probably fight till there death saying you could not lean out a diesel, but I like to think outside the box and I will say that with today's technology you can lean out a diesel to the point of melting pistons.
I have looked all over the internet on diesel forums and pretty much all of them say you cannot lean out a diesel. I am really going out on a limb here and I'm going to say all those people on all those forums are wrong. I know that in theory if you lean out a diesel you are just pulling throttle back and not making as much power but i will say that you can lean out a diesel and have the temp increase. But who do you "call" to find out? Who do you trust there answer? Just because they have built diesels for 100 years would mean nothing to me on if they are right or wrong. It just means they have lots of experience with what they have done but not that they know about something they have never tried.
So here is the question, who do we call to find out if you can lean out a diesel to the point of melting pistons?
Before people start fighting about that you cant lean out a diesel I will say that 99.99% of the diesels ever made you probably could not lean out enough to cause a problem and that any old time diesel mechanic that has worked on diesels for 100 years would probably fight till there death saying you could not lean out a diesel, but I like to think outside the box and I will say that with today's technology you can lean out a diesel to the point of melting pistons.
I have looked all over the internet on diesel forums and pretty much all of them say you cannot lean out a diesel. I am really going out on a limb here and I'm going to say all those people on all those forums are wrong. I know that in theory if you lean out a diesel you are just pulling throttle back and not making as much power but i will say that you can lean out a diesel and have the temp increase. But who do you "call" to find out? Who do you trust there answer? Just because they have built diesels for 100 years would mean nothing to me on if they are right or wrong. It just means they have lots of experience with what they have done but not that they know about something they have never tried.
So here is the question, who do we call to find out if you can lean out a diesel to the point of melting pistons?
Tyson, I have been around diesel my entire life, have built some pretty high HP rigs. Those motors are not going to last long running the HP you want to run. Even if you can keep EOT, ECT under control the piston just cant handle that much HP for that long and will melt.
You could try Monotherms but those don't like high RPM for long periods either.
If and this is a BIG IF was my rig I would be running a high end data logger on those motor, monitoring EGT, Rail Pressure, Coolant Pressure and Temp. and be setting high limits so it shuts down when it gets there or your going to be out at II for yrs getting this right. It's one thing to run it on the dyno in a perfect world, but the Min you load those motors different then the dyno and your MAP isn't perfect your going to be buying new piston.
Mike
11-21-2017, 06:50 AM
#1380
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You need to stop thinking of diesels as a gas engine. That is true with gasoline, diesel is completely different. I personally would listen to the guy above and call Gale Banks for a quick discussion - he would know more than anyone in this thread.
