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Thread: Piston faliure 6.2 whipple 7psi

  1. #1
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    Piston faliure 6.2 whipple 7psi

    Hi guys......had my truck engine faliure after 6months of installation of the whipple running on 7psi of boost cylinder #8 running 12.4 afr 93 octane truck made 560whp.....and total advance of 13 deg
    ....
    Will post some pictures of the piston ringlands are broken.....having a feeling it could be a stuck injector from the first glance...

  2. #2
    Senior Tuner Lakegoat's Avatar
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    Isn't 12.4 a little lean for a pd blower? I'm at 11.4--11.5 with my Magnuson.

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    Tuning Addict 5FDP's Avatar
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    That AFR sounds too lean to me.
    2016 Silverado CCSB 5.3/6L80e, not as slow but still heavy.

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    yes 12.4 is very lean and not go in a truck on a stock motor, for a motor safe for forced induction very lean will not live long there at all.

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    Tuning Addict 5FDP's Avatar
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    I dunno where you read that but I wouldnt have listened that for sure.

    Sorry that the motor went boom but with that much power and boost, I'd have been running 11-11.5 at a minimum.
    2016 Silverado CCSB 5.3/6L80e, not as slow but still heavy.

    If you don't post your tune and logs when you have questions you aren't helping yourself.

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    the new motors like to run leaner maybe just defective motor I've never had any issues
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  8. #8
    Senior Tuner Higgs Boson's Avatar
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    Quote Originally Posted by 5FDP View Post
    I dunno where you read that but I wouldnt have listened that for sure.

    Sorry that the motor went boom but with that much power and boost, I'd have been running 11-11.5 at a minimum.
    are you referring to direct injection applications or traditional port injection stuff like LS motors?

  9. #9
    I guess it cld be a failed injector or stuck injector?

  10. #10
    Tuning Addict 5FDP's Avatar
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    I must have missed the GEN 5 section part, text is kinda small up there.
    2016 Silverado CCSB 5.3/6L80e, not as slow but still heavy.

    If you don't post your tune and logs when you have questions you aren't helping yourself.

  11. #11
    Advanced Tuner AutoWiz's Avatar
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    I have an exercise for anybody interested. promises to teach something. What you do is mount a bung in each exhaust primary, and one by one plug a wideband into each primary and compare with o2 sensor reading from the vehicle. What this exercise is meant to teach is that the o2 sensor value is an average of what 4 cylinders are doing. some leaner, some richer. we would all be wise to remember this as we try to get greedy with afr values. especially under boost. maybe 12.4 can be ok if all 4 cylinders are at 12.4 and not a few at 11.9 and a few or one at 12.9.

  12. #12
    Advanced Tuner Redline MS's Avatar
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    There is nothing wrong in running a DI motor in boost into the mid 12's.....that is IF the final AFR is just that. With the ability to move injection timing you can conceivably have the correct mass of air, the correct mass of fuel and have the final AFR out the cylinder be all messed up due to when the fuel is fired. Now......the next issue.....the engineering behind the combustion chamber in DI was very challenging...when air enters the combustion chamber its coming in swirling, tumbling and axially. This "charge motion" enters the chamber and very specifically moves around the chamber where an injector with a very uniquely designed spray pattern fires this mass of fuel. Its kind of like a bob sled going around a turn at a specific speed... its predictable how high it follows the curve based on X speed. Because the time to mix the fuel and air is so short it has to start mixing lightning fast. GM has a million hours into this chamber......FYI.....now we start blowing high pressure and volume through the intake port and we completely mess up this design (bob sled at XX speed) ....now there is fuel not being used and the "measured" AFR is rich.....so people keeping leaning out the calibration to hit there target when in actuality the air model was correct and we know the injector data is correct. This is where EGT probes start coming in handy...

    This whole analogy leads to an unstable fuel control that can cause bad swings in fueling. This is one scenario..

    The other issue with boost and a PD blower is "pre-igntion", another problem the OEM has been chasing with DI motors. As we know, DI motors run higher compression ratios for the benefit of efficiency. They get away with it because one of the benefits of DI design is cylinder quenching since fuel is fired directly into the chamber providing cooling. Now we add boost on an engine with a high compression ratio (higher cylinder pressure) and this combo raises cylinder pressure very high...ESPECIALLY AT LOW LOADS!. Pre-ignition is when fuel in the chamber auto ignites before its suppose to (not by spark). Like a diesel. Very much like detonation this raises cylinder pressure very high. This pressure spike is enough to blow gaskets and break pistons.

    On top of this the pistons in the LT motor (not including the LT4) are junk. Most likely if you have broken ring lands and not sign of detonation there is something to look at.

    Much to popular thought...you don't burn down engines with an AFR a point off of the optimal....they just lay over and make less power. Look at a pickup truck that runs at lambda at WOT for a minute so they don't waste fuel.....I remember Saleen Mustangs where calibrated the same way with a blower.

    This is a cylinder pressure problem...this is where injection timing becomes critical....
    Last edited by Redline MS; 09-17-2015 at 08:44 PM.
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    What i have seen on stock trucks it happened too.

    Where are all the guys i need more insight on this could be a tune defect motor the truck was driven daily no issues one more hint that the oil pan had too much fuel in it

  14. #14
    Senior Tuner Higgs Boson's Avatar
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    Quote Originally Posted by Redline MS View Post
    This is a cylinder pressure problem...this is where injection timing becomes critical....
    Can you elaborate on injection timing? I have found DI to run a lot better when SOI allows EOI to be at or before 180. With EOI happening on the upstroke (compression), they seem to run very rough. Therefore, I do not understand the min EOI at 5 or 10 degrees before spark, that seems WAY too close.

    It seems to me, the latest you can inject fuel and still be done before compression stroke, the better. The longest injection window that seems ideal is EVC to 180 degrees. If it has to be lengthened, should it push into compression stroke or pull back past EVC?

    I read the 4 cylinder guys try to keep pulse width to 7.3ms or less or fuel puddling becomes an issue....how much power could we make at 7ms with an injection window between 360 and 180? 750 at the crank? So obviously, the extra injection window has to open either up or down.....which way is it?

  15. #15
    Senior Tuner Higgs Boson's Avatar
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    Also, what about HPFP commanded pressures (assuming they can always be achieved)....

    What happens if one just commands, say, 12 MPa on the whole Desired table and adjusts the VE/MAF accordingly. Do you have a fixed rate fuel system?

    You can adjust SOI, tank pressure, HPFP pressure, and the airflow tables would affect injector output. How do you decide to alter one in relation to another to obtain the same net effect of more or less fuel?

  16. #16
    Advanced Tuner AutoWiz's Avatar
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    I just can't get over 12.4 under boost.
    Last edited by AutoWiz; 09-18-2015 at 09:02 PM.

  17. #17
    Advanced Tuner Redline MS's Avatar
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    Quote Originally Posted by AutoWiz View Post
    I just can't get over 12.4 under boost.
    why? Who decided that 11.5-11.7 is the best? The internet.....the reality is that much of the additional fuel (above what you would consider reasonable for a NA motor) is for cooling. DI blows un-vaporized fuel right into the chamber where it has a tremendous capability to quench (cool) the combustion temps. This allows the ability to run a leaner AFR then what we are used to in port fuel engines..

    The bottom line is there is a range that engines like to run at for good power but there are many factors that can effect what is really the best. Different fuels react differently, as well as how efficient a combustion chamber works. The GEN5 cylinder head is very efficient which is another reason you can run leaner. Unless you can spend enough quality time on a dyno its hard to find this.

    Higgs,

    The injection timing strategy with this controller is much more complex then what we have available with the current tables. We are getting ready to test an engine in which we installed EGT probes which will really give is some insight as to what direction we should be going and why. As stated earlier even the WB is not telling us the full story when it comes to what is going on it the chamber. EGT's will offer another "dimension" into what's happening. The math is driving me nuts as there has to be some other factors that offset timing based upon airflow changes.

    I'm still wondering if your LT4 fuel hardware changes require more that is in a LT4 OS that is causing some of your issues....
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  18. #18
    Senior Tuner Higgs Boson's Avatar
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    Me too.....I am wondering if I can just license an LT4 OS and Write Entire.

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    Quote Originally Posted by Redline MS View Post
    why? Who decided that 11.5-11.7 is the best? The internet.....the reality is that much of the additional fuel (above what you would consider reasonable for a NA motor) is for cooling. DI blows un-vaporized fuel right into the chamber where it has a tremendous capability to quench (cool) the combustion temps. This allows the ability to run a leaner AFR then what we are used to in port fuel engines..

    The bottom line is there is a range that engines like to run at for good power but there are many factors that can effect what is really the best. Different fuels react differently, as well as how efficient a combustion chamber works. The GEN5 cylinder head is very efficient which is another reason you can run leaner. Unless you can spend enough quality time on a dyno its hard to find this.
    This is key information for any tuner. All this "boosted cars need to be rich" crap is just dogma. It's all about maximum tolerable heat in combustion chamber without detonation. My car hit MBT at 20* (afr 11.5) and made 785rwhp. Not a peep from the knock sensors (working great), and spark plugs showed plenty of heat range left. Started leaning it out and making more and more power until I finally saw a small hint of KR at 13:1. Backed it off to 12.7:1 and made 856rwhp. 91 + meth. LS motor not DI.

    Now , 5000 miles of abuse later , I have the engine apart, everything looks new. Putting another motor in with higher compression.

    Just thought it was worth sharing
    Last edited by nkautz; 09-19-2015 at 07:11 AM.
    2001 Z06 : 856/830 : Built LQ9 403ci : D1SC 17psi : Self-built , self-tuned.

  20. #20
    Advanced Tuner Redline MS's Avatar
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    Quote Originally Posted by nkautz View Post
    This is key information for any tuner. All this "boosted cars need to be rich" crap is just dogma. It's all about maximum tolerable heat in combustion chamber without detonation. My car hit MBT at 20* (afr 11.5) and made 785rwhp. Not a peep from the knock sensors (working great), and spark plugs showed plenty of heat range left. Started leaning it out and making more and more power until I finally saw a small hint of KR at 13:1. Backed it off to 12.7:1 and made 856rwhp. 91 + meth. LS motor not DI.

    Now , 5000 miles of abuse later , I have the engine apart, everything looks new. Putting another motor in with higher compression.

    Just thought it was worth sharing
    Most certainly! Thanks! I think a big problem I see is a lot of people approach the calibration as if its an exact science yet everyone is running different setups. Of course the basic concept applies overall but when it comes to the fine details there are variables. DI has really shifted this as so much is going on at one time. There was a reason why GM went to a coefficient based processing system to handle all this. VE is infinite and constantly moving; then adding injection timing on top its like trying to hit a bulls-eye on a dart board that's swinging from a chain on wall during an earthquake.

    The minute we stuff a camshaft, swap heads, and put boost into it we just completely pissed into the wind. Now we have to reverse engineer to back solve how they got it working the first time. The advantage we have as a shop is we see these variations in combinations and how it effects the wind. Hat's off to guys like Higgs who is very intently focused on his build and has experienced a lot. We have seen a lot in the last 3 years of DI so the statements made are from the shear volume of exposure.

    I was hoping we would of had our engine dyno by now as that's when we can really buckle down and focus... in the mean time you have to combine the physics of engines and the reality of testing to really get through it!
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