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Re: Pump gas compression
[Re: 6pkScamp]
#1424792
04/24/13 11:54 AM
04/24/13 11:54 AM
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Joined: Jan 2003
Posts: 6,266
Renton Washington
Triple Threat
master
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master
Joined: Jan 2003
Posts: 6,266
Renton Washington
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I ran 92 octane pump gas in my 11.3:1 390" small block stroker. Edelbrock heads and 263/268@.050 solid FT cam.
I never measured cylinder pressure.
-Dustin
67 Dart, 9 second, 392" G3 Hemi
68 Barracuda 340 F/SA
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Re: Pump gas compression
[Re: 383man]
#1424794
04/24/13 12:26 PM
04/24/13 12:26 PM
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Joined: Dec 2006
Posts: 1,178
Indy
FlyFish
super stock
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super stock
Joined: Dec 2006
Posts: 1,178
Indy
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410 stroker, edelbrocks, 10.89:1 compression, 248/254 @ 0.050 solid roller and it runs on premium pump gas.
67 Barracuda street car, 408, e85, 1.38 60', 6.44 @105.9 in the 1/8 mile, 10.19 @130.5 in the 1/4...so far....
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Re: Pump gas compression
[Re: 6pkScamp]
#1424795
04/24/13 01:25 PM
04/24/13 01:25 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 have 512"kit, 12.42 Eddy heads,street roller cam,pumps 185# pressure on 93 pumpgas.I think the pumping pressure is the key.No gain with 110 racegas,no gain from 33* or 36* on the timing.308*/.575" cam installed@ 106*.
Last edited by bentwheel43; 04/24/13 01:28 PM.
Section 8 Racing We are nuts about racing.
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Re: Pump gas compression
[Re: 6pkScamp]
#1424796
04/24/13 03:17 PM
04/24/13 03:17 PM
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Joined: Jun 2003
Posts: 52,972
Romeo MI
MR_P_BODY
Master
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Master
Joined: Jun 2003
Posts: 52,972
Romeo MI
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Your cam will dictate alot of your question(when the intake valve really closes is when you start making compression) but on my 416 with W-5 heads and a static compression of 10.7 and 260/270 105 lsa installed at 105 and the timing at 39*... it made 550 hp on 93 octane and if I pull 2* or 3* it will run on 87 no problem 
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Re: Pump gas compression
[Re: 6pkScamp]
#1424797
04/24/13 04:24 PM
04/24/13 04:24 PM
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Joined: Feb 2007
Posts: 6,295
U.S.
moparniac
master
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master
Joined: Feb 2007
Posts: 6,295
U.S.
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I only crank at 170psi. Probably why my car is such a dud.
Mopar Performance
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Re: Pump gas compression
[Re: moparniac]
#1424798
04/24/13 07:44 PM
04/24/13 07:44 PM
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Joined: Oct 2009
Posts: 1,267
North, Alabama
D-50
pro stock
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pro stock
Joined: Oct 2009
Posts: 1,267
North, Alabama
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My stroker small block, 394 cubic in.is 10.9 to one has a 255/266 at .050 cam, cylinder pressure is in the 190's. Run it on 93 octane. 35* timing.
1.33 60 ft,6.21 at 110.59 in the 1/8, pump gas small block,2950lbs,drag radials,mufflers and driven to track ...
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Re: Pump gas compression
[Re: Dunnuck Racing]
#1424801
04/24/13 11:02 PM
04/24/13 11:02 PM
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Joined: May 2011
Posts: 625
Oakville, Wa
HOTMOPR
mopar
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mopar
Joined: May 2011
Posts: 625
Oakville, Wa
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Is there a general rule of thumb that says with a certain compression you should be running a certain octane gas? I always wondered how much you could push it. Such as a 9-1 motor on 8 psi is almost 14-1 total compression. Give or take.
67 Barracuda, 470" B, Glide, FuelTech FT600, Precision, Ptc, QA1, Calvert, Smith racecraft, Afco, Dana 60. 275 radials
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Re: Pump gas compression
[Re: HOTMOPR]
#1424802
04/24/13 11:12 PM
04/24/13 11:12 PM
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Joined: Jun 2003
Posts: 52,972
Romeo MI
MR_P_BODY
Master
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Master
Joined: Jun 2003
Posts: 52,972
Romeo MI
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Quote:
Is there a general rule of thumb that says with a certain compression you should be running a certain octane gas? I always wondered how much you could push it. Such as a 9-1 motor on 8 psi is almost 14-1 total compression. Give or take.
There are still the other factors that have been said..
the static compression number is just that... its
a mathematical figure of what the area is with the
piston up and down.... if the intake closes when the
piston is half way up verses if it closed with the
piston at the bottom they both still have the same
static compression value but they sure wont be the same
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Re: Pump gas compression
[Re: Thumperdart]
#1424804
04/24/13 11:24 PM
04/24/13 11:24 PM
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Joined: Feb 2011
Posts: 4,302
Nebraska
72Swinger
master
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master
Joined: Feb 2011
Posts: 4,302
Nebraska
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I just had a thread about my struggles with my 10.2.1 iron headed BB when I switched from auto to manual trans. I used to run fine on pump 91 and 37 degrees total with a converter that flashed to 3500. And with the manual trans it was a ping fest until went to 35 total, a lighter spring in the dizzy and one step colder plugs. I can get it to ping still a little if I'm in 3rd and stand on it at 1500 rpm so I just don't do that.
Mopar to the bone!!!
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Re: Pump gas compression
[Re: 72Swinger]
#1424806
04/25/13 02:37 AM
04/25/13 02:37 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:
I just had a thread about my struggles with my 10.2.1 iron headed BB when I switched from auto to manual trans. I used to run fine on pump 91 and 37 degrees total with a converter that flashed to 3500. And with the manual trans it was a ping fest until went to 35 total, a lighter spring in the dizzy and one step colder plugs. I can get it to ping still a little if I'm in 3rd and stand on it at 1500 rpm so I just don't do that.
I'm also of the belief you can run higher compression with a higher stall converter as you are removing the load at low RPM, where ping is usually at it's worst.
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Re: Pump gas compression
[Re: 572charger]
#1424810
04/26/13 05:58 AM
04/26/13 05:58 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:
my pumpgas hemi is 12.1 to 1 comp but its a big roller cam/ only has 185#s cranking comp it goes 2 tenths SLOWER on 112 race gas !!  all the wedges i build with aluminum heads i shoot for 11 to 1 comp on pump gas its pretty safe with a good cooling system !![aluminum radiator ] 
OK, so what compression would you run an alloy head 484ci Hemi at with a roller cam 268*/264* @ .050 & .637"/.634" street strip E-Body, pump gas here in NZ is 95-96 but some stations have 98 Cheers
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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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