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Re: Dynamic compression
[Re: 416challenger]
#2282982
04/05/17 07:26 PM
04/05/17 07:26 PM
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Joined: Jan 2003
Posts: 15,439 Val-haul-ass... eventually
BradH
Taking time off to work on my car
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Taking time off to work on my car
Joined: Jan 2003
Posts: 15,439
Val-haul-ass... eventually
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I don't know that I'd take it as The Final Answer, but I suppose it may give you some idea of what may be possible. EDIT: This is from David Vizard .
Last edited by BradH; 04/05/17 07:32 PM.
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Re: Dynamic compression
[Re: 416challenger]
#2283299
04/06/17 12:16 PM
04/06/17 12:16 PM
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Joined: Oct 2007
Posts: 4,206 New York
polyspheric
master
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master
Joined: Oct 2007
Posts: 4,206
New York
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IMHO DCR over-rated as a limit. With enough gear and stall speed, it almost doesn't matter.
Boffin Emeritus
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Re: Dynamic compression
[Re: polyspheric]
#2283336
04/06/17 01:48 PM
04/06/17 01:48 PM
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Joined: Jan 2003
Posts: 15,439 Val-haul-ass... eventually
BradH
Taking time off to work on my car
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Taking time off to work on my car
Joined: Jan 2003
Posts: 15,439
Val-haul-ass... eventually
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IMHO DCR over-rated as a limit... There are enough people way smarter than I am who have beaten this subject into the ground on SpeedTalk that I don't even take it into account for my own builds. Even if it is a valid predictor of fuel octane requirements (and that has been a key issue in the ST debates from years back), you can't even get two people to agree on what valve- or cam-lift measurement establishes the IVC point.
Last edited by BradH; 04/06/17 01:54 PM.
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Re: Dynamic compression
[Re: 416challenger]
#2283376
04/06/17 03:03 PM
04/06/17 03:03 PM
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Joined: Jan 2005
Posts: 12,419 Kalispell Mt.
HotRodDave
I Live Here
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I Live Here
Joined: Jan 2005
Posts: 12,419
Kalispell Mt.
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The IVC point will matter at different RPMs, what I mean by that is inertia supercharging will affect it more or less as the RPM changes.
The chart above is ok to give you just an idea but will be different with different engine combos with quench or without, port desighn, how cod the intake air is or is not, runner length, reverse flow or standard cooling... many other things but strictly temperature speaking gives you a rough idea how it will be effected just by coolant temp.
For the most part polys statement is true, especialy with ethanol as it seems people are running very high static and dynamic compression with it and I never heard anyone with detonation issues. I have heard of at least one guy running 16.5 on e85 but I imagine the %15 gas was not ordinary 85 octane like the e85 at the pump.
I am not causing global warming, I am just trying to hold off a impending Ice Age!
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Re: Dynamic compression
[Re: BradH]
#2283671
04/06/17 11:47 PM
04/06/17 11:47 PM
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Joined: Feb 2005
Posts: 4,314 Prospect, PA
BSB67
master
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master
Joined: Feb 2005
Posts: 4,314
Prospect, PA
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IMHO DCR over-rated as a limit... you can't even get two people to agree on what valve- or cam-lift measurement establishes the IVC point. Right, and right. I've seen three different intake closing points used for the same formula. My fairly light 383 Dart with a much higher CR, 3.91 gear, and 4 speed got by much better on pump gas than my heavy weight, lower CR Charger with 3.23s, std converter, and no part throttle kick down.
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