in cylinder pressure wave form thats got me baffled

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Jayman
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in cylinder pressure wave form thats got me baffled

Post by Jayman »

Ram_1500_2013_20230326-0001.psdata
in cylinder wave form
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Good day!!!! Heres a wave form of a 2013 ram 1500 5.7L hemi with lifter tick/clunk in cylinder pressure at idle and im baffled to what could be going on in the first 180* rotation prior to exhaust stroke!! Theres no engine codes or misfires or anything to point me to anything really truck runs fine other then lifter noise after it warms up!!! Any insight or analysis of this would be most appreciated Thanks kindly

tintoverano
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Re: in cylinder pressure wave form thats got me baffled

Post by tintoverano »

most probably broken exhaust valve

check it with a boroscope

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Jayman
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Re: in cylinder pressure wave form thats got me baffled

Post by Jayman »

I guess it could be! but on every cylinder? i thought out of time at first but truck seams to run fine other then the dreaded lifter noise on both banks! cam and lifters were just done due to the notorious hemi cam lifter issue. truck fires up decent no long cranks no misfire data!!! this ones really got me confused!!!

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Jayman
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Re: in cylinder pressure wave form thats got me baffled

Post by Jayman »

here is a shot of bank1 cylinders and one on bank 2 to confirm its on both banks!! Again any input is better then no input so pls chime in :)
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Ram_1500_2013_20230326-0005.psdata
bank2
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Ram_1500_2013_20230326-0004.psdata
bank1
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Ram_1500_2013_20230326-0003.psdata
bank1
(4.11 MiB) Downloaded 101 times
Ram_1500_2013_20230326-0002.psdata
bank1
(1.72 MiB) Downloaded 106 times

picowight
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Re: in cylinder pressure wave form thats got me baffled

Post by picowight »

That's an interesting one - this is at idle I assume from the intake vacuum.
I would say a leak between cylinders as the pressure starts to increase at 60 ATDC when all the valves are shut (or supposed to be) that can only come from another cylinder. If an exhaust valve was open it would decrease - or not build pressure in the first place.
The only other thing would be a change in volume caused by a sloppy bearing - but then I would expect it to level out not increase.

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Jayman
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Re: in cylinder pressure wave form thats got me baffled

Post by Jayman »

So i got a capture from another 2014 pick up with a 5.7 hemi and its very similar!!! So im not so concerned so much any more but pls feel free to explain if anyone knows whats happening here!!
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vasek
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Re: in cylinder pressure wave form thats got me baffled

Post by vasek »

Hi.
.
Very similar to this signal :
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HONDA FIT.PNG

jueja
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Re: in cylinder pressure wave form thats got me baffled

Post by jueja »

I've seen similar shaped waveforms from this specific engine with a two plug per cylinder design on a working cylinder where the second plug was not disabled from sparking. The peak pressure obviously was significantly higher but the contour of the capture looked almost identical. It calls my attention that the example Vasek shows is also from an engine with dual plug design.

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Jayman
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Re: in cylinder pressure wave form thats got me baffled

Post by Jayman »

Awesome observation!!! im going to further look into it over time to just get to potentially see why its like this!!! seriously thank you everyone who has inputted some theory behind the capture and by all means if someone has definitive info pls share!!!! :D


edit: so your saying that because the engine is firing on the other plug we will get this type of wave form?

wiki38andy
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Re: in cylinder pressure wave form thats got me baffled

Post by wiki38andy »

Combustion takes place in cylinder.
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Screenshot 2023-03-31 193942.png

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