What the F*#*
10-01-2010, 02:59 PM
#26
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Re: What the F*#*
I understand what you're all saying but actually the search engine in here eats so much donkey ******* that I've found old threads bumped on topics I searched for hours for so while I don't want stuff with no pics from 1997 coming to the top it has been helpful
10-01-2010, 03:51 PM
#27
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Re: What the F*#*
I went with a bigger cam to make the compression more "pump gas" friendly, i understanding changing the DCR and SCR.
Dynamic compression really refers to the amount of trapped air/fuel in the cylinder when the INT valves close,from what i thought dynamic compression is just static compression corrected for IVC.
Kindof like boosting alot, a boosted engines SCR will be significally higher then a n/a's motor.
Dynamic compression really refers to the amount of trapped air/fuel in the cylinder when the INT valves close,from what i thought dynamic compression is just static compression corrected for IVC.
Kindof like boosting alot, a boosted engines SCR will be significally higher then a n/a's motor.
DCR, however, is the volume in the cylinder when the valve closes divided by the volume in the cylinder at TDC. Without degreeing the cam, you will not know at what crank degree the valve closes so you can n ot accurately calculate DCR. Obviously, DCR will be lower than SCR. Some experts have said about 9-9.5:1 is the max DCR for pump gas, but that is really only a general rule of thumb as some engines have proven differently.
A boosted engine's SCR and DCR will be the same compared to a NA motor because it only accounts for volume. A boosted engine only traps more mass of air per volume of air, which is not DCR, but the volumes stay the same so the compression ratios stay the same.
10-02-2010, 10:51 AM
#28
HT White Ops
Re: What the F*#*
All Motor, you really did go a little crazy with this man. If there are threads you think are truly valuable, feel free to PM me or Jimmy with a list of them and we will see about adding them to the FAQ thread stickied at the top of the forum.
10-03-2010, 12:10 PM
#30
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Re: What the F*#*
The pro2's bleed off compression..
s2s2's aren't as big as the pro2's..
Do the math - 12.8 CR rollerwaves with a GSR head stock - my head is milled .050'' with a 3layer hg, and skunk2's new high compression valves puts me right around 13.4's or 13.3 with the pro2's i should be around 13:1 13:0 give or take..
s2s2's aren't as big as the pro2's..
Do the math - 12.8 CR rollerwaves with a GSR head stock - my head is milled .050'' with a 3layer hg, and skunk2's new high compression valves puts me right around 13.4's or 13.3 with the pro2's i should be around 13:1 13:0 give or take..
85x89 - RL(5.394") chambercc(41.60)(gsr head) remember, .050'' removed from the head, using a GE 3layer 85mm HG.
piston cc is 7.75
Comp. Height 1.180"
I've done it like 10 times.. you'll come out to around 13.0 or 13.1
I went with a bigger cam to make the compression more "pump gas" friendly, i understanding changing the DCR and SCR.
Dynamic compression really refers to the amount of trapped air/fuel in the cylinder when the INT valves close,from what i thought dynamic compression is just static compression corrected for IVC.
Kindof like boosting alot, a boosted engines SCR will be significally higher then a n/a's motor.
piston cc is 7.75
Comp. Height 1.180"
I've done it like 10 times.. you'll come out to around 13.0 or 13.1
I went with a bigger cam to make the compression more "pump gas" friendly, i understanding changing the DCR and SCR.
Dynamic compression really refers to the amount of trapped air/fuel in the cylinder when the INT valves close,from what i thought dynamic compression is just static compression corrected for IVC.
Kindof like boosting alot, a boosted engines SCR will be significally higher then a n/a's motor.
10-03-2010, 12:51 PM
#31
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Re: What the F*#*
Seriously, I'm not the smart guy here, but this guy is always saying TONS OF BULLSH*T... And often using DonF's name in his bla bla.
The thing is, people believe his crap, and think he is the best around. I did believe him in the past, but now I'm try to listen the ones who actually know what they are saying.
The thing is, people believe his crap, and think he is the best around. I did believe him in the past, but now I'm try to listen the ones who actually know what they are saying.
10-03-2010, 01:01 PM
#32
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Re: What the F*#*
Everyone makes mistakes. Its only when you don't learn from them that you've really done something stupid. He just got the two terms confused...no biggie.
10-03-2010, 02:08 PM
#33
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Re: What the F*#*
Agreed. Seems the same bored/tried info keeps coming up. Good info that has been on the top for awhlie could do this section some good. Tired of seeing HELP!!!! ENGINE WON'T START!!!! and WHAT WILL THIS DYNO AT?
10-07-2010, 01:58 AM
#36
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Re: What the F*#*
I thought the term dynamic compression ratio was incorrect and the correct term was effective compression ratio.
I spent about 2 hours at work one day reading a big article on the subject and it really intrigued me because I had a stock cr ls motor with big cams in it and from what I read I could bump up my effective cr by retarding my intake cam to close the valves sooner. so I did, and it ran harder
I spent about 2 hours at work one day reading a big article on the subject and it really intrigued me because I had a stock cr ls motor with big cams in it and from what I read I could bump up my effective cr by retarding my intake cam to close the valves sooner. so I did, and it ran harder
10-07-2010, 06:09 AM
#37
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Re: What the F*#*
Even "dynamic" compression doesn't really tell the whole story because it doesn't account for VE values or compression and rarefaction waves from sonic or pressure signals in the induction system.
That's besides the point. The bumped threads are lame, but who cares cause you can ignore them.
That's besides the point. The bumped threads are lame, but who cares cause you can ignore them.
10-07-2010, 06:41 AM
#38
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Re: What the F*#*
What's incorrect about the term dynamic CR?
I don't think any single measurement is going to tell the whole story on any engine, but I think DCR is only a piece of it.
I don't think any single measurement is going to tell the whole story on any engine, but I think DCR is only a piece of it.
10-07-2010, 07:02 AM
#40
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Re: What the F*#*
If you were referring to my post, I didn't mean for it to sound as if dynamic compression is incorrect, or not useful. Just that even dynamic compression isn't going to mean that you can run X octane or that Y engine will make more torque, etc. I was probably agreeing with you, if anything.
10-07-2010, 07:15 AM
#41
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Re: What the F*#*
If you were referring to my post, I didn't mean for it to sound as if dynamic compression is incorrect, or not useful. Just that even dynamic compression isn't going to mean that you can run X octane or that Y engine will make more torque, etc. I was probably agreeing with you, if anything.
10-07-2010, 10:32 AM
#42
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Re: What the F*#*
I just remember reading a article, I think it may have been by rocket, idk its been a year or two, but they explained how the term dynamic was incorrect and actually it had something to do with v.e. as well as when the intake valves close.
10-07-2010, 10:45 AM
#43
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Re: What the F*#*
But VE has nothing to do with Dynamic Compression Ratio.
10-07-2010, 05:13 PM
#46
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Re: What the F*#*
this is when we need rocket to shine the light on the topic, or gives us a clue and we search for it lol
10-07-2010, 05:32 PM
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10-08-2010, 06:29 AM
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Re: What the F*#*
Well I would take the term dynamic compression ratio, as it's most commonly used, to be a numerical representation of IVC and static compression together. It is just ratios in that case.
VE, and actually even more so air speed, will greatly affect that number when the engine is actually running. For example very well developed small port 2 valve per cylinder engines (like NHRA super stock) do a large amount of their cylinder filling after BDC. In some cases with these engines they will actually INCREASE running cylinder pressure by retarding the camshaft, at least at higher RPM. I mean that's sort of obvious because anyone who has ever advanced or retarded camshafts on an engine has seen the power curve move up or down generally shifting around torque peak.
So maybe someone wrote an article saying that VE affects dynamic compression because to them dynamic compression actually means running compression or actual cylinder pressure.
This is so off topic it's ridiculous. Just ignore the guy bumping stuff and maybe he will stop.
VE, and actually even more so air speed, will greatly affect that number when the engine is actually running. For example very well developed small port 2 valve per cylinder engines (like NHRA super stock) do a large amount of their cylinder filling after BDC. In some cases with these engines they will actually INCREASE running cylinder pressure by retarding the camshaft, at least at higher RPM. I mean that's sort of obvious because anyone who has ever advanced or retarded camshafts on an engine has seen the power curve move up or down generally shifting around torque peak.
So maybe someone wrote an article saying that VE affects dynamic compression because to them dynamic compression actually means running compression or actual cylinder pressure.
This is so off topic it's ridiculous. Just ignore the guy bumping stuff and maybe he will stop.
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