Can any one explain how a harmonic dampener on a V8 works? Is it tuned to the natural frequency of the crankshaft? Does it dampen the torsional twist of the crank from the power pulses? Why does one dampener work for cast/steel cranks? How can sprint car motors run with out one? Thanks!
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Harmonic Dampeners 3
- Thread starter steve383
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I understand the dampener, but we also intend to internally balance the engine and I feel that this cnc part aproach will hopefully eleminate the need to balance the crankshaft. Other parts will need to be balanced as well. I appreciate the recomendation. I'll contact them and see what they have to say.
patprimmer
New member
I always thought roller bearings had durability problems when subjected to shock loads from detonation.
Diesels run in a state of constant detonation?
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pat pprimmer@acay.com.au
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Diesels run in a state of constant detonation?
Regards
pat pprimmer@acay.com.au
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the cylinder pressure trace from a typical diesel doesn't look all that much different (to the eye) from that of a gasoline engine - the biggest difference is that the diesel has a much higher peak pressure. The general shapes of the curves are very similar (no step changes in pressure or anything like that).
These engines are all four cylcle. We will be using pilot injection and that helps with the detonation issue. The bearings are 4" od full compliment needle bearings. We are not completely sure that this will work but the force is being spread accross two of these bearings with each combustion event. 7 mains on six cylinder.
Mike
Thanks,
Mike
Mike
Thanks,
Mike
IME the pressure traces for diesel can be higher, but not necessarily so in general. For example, I try to limit the 900+hp turbo v6 SI engine I have to about 1600-1700psi max. It shows no signs of undo duress at this pressure in a 1/4 mile drags application. Yes I do have cyl pressure gear for home use 
One of the 4 cyl project turbo diesels I worked on was limited to 1800 psi max, per the mfgr. This was an emissions reduction project and we had full authority electronic control over injection timing and quantity, exh backpressure, etc, while also always monitoring cyl pressure in real time, etc (dedicated analog scope). Depending on injection timing and such, there can be a noticable step as the cylinder pressure transitions from primarily compression pressure to heat release pressure. One can also readily hear the change in how the engine "hammering" sound changes as the pressure curve changes shape. I sat there for many weeks at a dyno cell and tuned this particular engine for power targets, NOx + HC emissions tradeoffs etc. And of course no, diesel combustion is not detonation An interesting topic, sorry to stray off the orginal damper topic for a moment...
TurboTR
One of the 4 cyl project turbo diesels I worked on was limited to 1800 psi max, per the mfgr. This was an emissions reduction project and we had full authority electronic control over injection timing and quantity, exh backpressure, etc, while also always monitoring cyl pressure in real time, etc (dedicated analog scope). Depending on injection timing and such, there can be a noticable step as the cylinder pressure transitions from primarily compression pressure to heat release pressure. One can also readily hear the change in how the engine "hammering" sound changes as the pressure curve changes shape. I sat there for many weeks at a dyno cell and tuned this particular engine for power targets, NOx + HC emissions tradeoffs etc. And of course no, diesel combustion is not detonation An interesting topic, sorry to stray off the orginal damper topic for a moment...TurboTR
PS we also ran pilot injection on some other project diesel engines. Really an amazing quieting effect available from it- we even had an on/off switch to dramatically demo the effect. I can't wait until it catches on with all the annoyingly loud, clattery diesel p/u trucks around here, lol... And for emssions restriction to tighten on them as well <gack>. Anyway, basically pilot injection spreads the heat release curve out and greatly reduces the "hammering" clatter effect resulting from rapid heat release. Since direct diesel injection occurs right near the start of the power stroke, a diesel is constrained to getting all the fuel in and getting it burned rather quickly. It must all get into the cylinder within milliseconds in an intense, high pressure shot, depending on the load, rpm, etc of course. A port EFI engine otoh can have fuel squirting at the intake valve for 720 degrees of rotation if need be
TurboTR
TurboTR
I agree, 1750 is probably getting high for SI. Our engine supplier stated clearly that 1800 was the limit on this engine. 3100 psi- wow!!! If we had say a 4" bore, that would be a peak force of over 38,000 lbs pushing down on the piston (!!) The equivalent of having 11 average weight cars stacked up on top of it...
TurboTR
TurboTR
patprimmer
New member
Like I said, even if for the wrong reason, very high point pressures on a roller bearing.
Regards
pat pprimmer@acay.com.au
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Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
Regards
pat pprimmer@acay.com.au
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
An interesting article -nice color diagrams also.
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