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Re: Pump gas compression
[Re: 572charger]
#1424812
04/26/13 08:51 AM
04/26/13 08:51 AM
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Joined: Feb 2011
Posts: 159
australia
charger410
member
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member
Joined: Feb 2011
Posts: 159
australia
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I'm all for running as much comp as you can but I would think 12-1 would be the limit as long as that camshaft had plenty of overlap. like over 100deg, Like MR P Body touched on. Don't beat up on it unless you mix in a bit of race fuel and you should be good  Also make sure that the pump fuel is always fresh. No more than afew weeks in your tank. Pump fuel is not like race fuel in that its probably already dropped a point by the time you've bought it, and goes off quickly. 
Peter. Australian Charger, alloy block injected 410in, w9 na 9.03@148 leafs 3000lb
1967 barracuda 605 hemi Stage5 millennium 8.2@170
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Re: Pump gas compression
[Re: charger410]
#1424813
04/26/13 12:09 PM
04/26/13 12:09 PM
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Joined: Mar 2009
Posts: 1,058
bigfork mn
dragram440
super stock
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super stock
Joined: Mar 2009
Posts: 1,058
bigfork mn
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I always wonder about this subject with mine. If I ever have to could I drive it on the street with 92 in a bind or something. Its alum. head 499 with 12.52-1 but only has 185 psi cranking compression. I run 36 degrees of timing with 110 and have never had a issue with detonation. Could I run 92 with say 32 degrees of timing if Im not taking it easy or is that just dumb?
67' charger 499 RB
10.57 at 127
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Re: Pump gas compression
[Re: dragram440]
#1424815
04/26/13 02:06 PM
04/26/13 02:06 PM
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Joined: Nov 2006
Posts: 635
mississippi
bentwheel43
mopar
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mopar
Joined: Nov 2006
Posts: 635
mississippi
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I say yes with 185# pumping.Mine burns better 33* on timing with 93 pumpgas.And I bet if we were to hit them with a 100 shot and 110racegas we would get more than 100 added HP on 500" or 512"!!
Last edited by bentwheel43; 04/26/13 03:32 PM.
Section 8 Racing We are nuts about racing.
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Re: Pump gas compression
[Re: dannysbee]
#1424816
04/26/13 09:54 PM
04/26/13 09:54 PM
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Joined: Nov 2009
Posts: 520
New Zealand
nz383man
mopar
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mopar
Joined: Nov 2009
Posts: 520
New Zealand
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Quote:
Quote:
95 -96 octane i would not be afraid to run 12 to one compression depending on cranking comp also, 98 octane thats great wish we had that here im only runnin 93 octane
. he probably needs to do some research on how they come up with the ratings in his country. Our ratings are figured by using the figures from two different methods and averaging them together. I know one of the methods is the motor method. I can't remember the other.
I hear what you are saying about advertised octane ratings vs actual ratings. I know a guy that works for the technical devision of Shell so I'll contact him & see what they use to justify their claimed octane ratings here in NZ.
Research Octane Number (RON)
The most common type of octane rating worldwide is the Research Octane Number (RON). RON is determined by running the fuel in a test engine with a variable compression ratio under controlled conditions, and comparing the results with those for mixtures of iso-octane and n-heptane.
Motor Octane Number (MON)
There is another type of octane rating, called Motor Octane Number (MON), or the aviation lean octane rating, which is a better measure of how the fuel behaves when under load, as it is determined at 900 rpm engine speed, instead of the 600 rpm for RON.[1] MON testing uses a similar test engine to that used in RON testing, but with a preheated fuel mixture, higher engine speed, and variable ignition timing to further stress the fuel's knock resistance. Depending on the composition of the fuel, the MON of a modern gasoline will be about 8 to 10 points lower than the RON, however there is no direct link between RON and MON. Normally, fuel specifications require both a minimum RON and a minimum MON
I see there are sensors available to test ethanol blends such as the Flex fuel sensors
http://www.haltech.com/flex-fuel-sensor/
It's a shame it's not quite so simple for testing actual octane ratings. 
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Re: Pump gas compression
[Re: quickd100]
#1424817
04/26/13 10:07 PM
04/26/13 10:07 PM
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Joined: Jan 2007
Posts: 7,664
IN
ahy
master
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master
Joined: Jan 2007
Posts: 7,664
IN
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Quote:
I like to er on the conservative side. Your better off 1/2 a point lower than possible than have to pull all the timing out of it. You also have to remember you may not be able to find 91-3 octane fuel everytime you have to fill it up. Dave
Me too. You have to finish the race to win. Also, it depends on application. A short blast down the 1/4 or putting around town does not build a lot of heat. Sustained hard running does and can cause detonation. I'm at 10.2 on a 496 with 243@.050 cam and 108 LSA. Tight quench also.
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Re: Pump gas compression
[Re: dannysbee]
#1424819
04/27/13 03:18 AM
04/27/13 03:18 AM
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Joined: Nov 2009
Posts: 520
New Zealand
nz383man
mopar
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mopar
Joined: Nov 2009
Posts: 520
New Zealand
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Quote:
Our octane ratings are an average of the two ron plus mon divided by two. You would need to see how they figure yours to see where your at. I just wanted to make you aware there might be a difference in ratings.
From what I have found out so far ours (NZ) could just be a RON measurement only, that's probably why the octane ratings look so high. 
I might have to lower my sights a bit to be on the safe side.
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