What's your favorite compression ratio for boost or N.A.?
12-28-2017, 09:05 AM
#1
What's your favorite compression ratio for boost or N.A.? If you could pick one target ratio for boost and another for N.A. (plus a light hit of spray maybe) on your street/strip vehicle, what would it be? 9.0, 9.5, 11, 11.5? In this forum, most would be in the 60-65cc chamber range usually.
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12-28-2017, 09:17 AM
#3
I'd shoot for 9.5:1 on boosted applications unless running race grade E85 or straight methanol, where even 10.5:1 can work well
NA seems to be more responsive with 11.5:1 specifically when running larger/higher duration camshafts......plus juice just means knocking the timing back and running proper octane as well.
And if budget or time forces a compromise and "desired" compression can't be obtained; well then the most efficient head (flow per volume) is always a GREAT band aid..........
And Trick Flow stuff has always been top notch....
NA seems to be more responsive with 11.5:1 specifically when running larger/higher duration camshafts......plus juice just means knocking the timing back and running proper octane as well.
And if budget or time forces a compromise and "desired" compression can't be obtained; well then the most efficient head (flow per volume) is always a GREAT band aid..........
And Trick Flow stuff has always been top notch....
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12-30-2017, 10:39 AM
#10
FormerVendor
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Density Ratio & Ignition Accuracy Hi TFT, the fuel used by the engine has the most effect on designed C.R. choice.
We have customers that use my controllers/coils in Paris, TX. that run 12:1 CR at WOT, 1800 RPM for 25K hours with LS. (constant operation )
The fuel used is Natural Gas.
My record for a Test Engine is the use of a Subaru EJ-20 with 14.5 C.R. (14 .lbs turbo boost) bench dyno ran, used to teach others about E-100 (E-fuels)
The second greatest race in the world is Pikes Peak with the start at 9,000 ft to 14,000 ft.
This application, N/A, requires a 18:1 C.R. as common, another example. (my customers)
My Method : Turbo C.R. Selection = Static Ratio x Density Ratio.
Example of 14 .lbs = a 1.5 Density Ratio = 9.5 x 1.5 and is a 14.25 C.R.
Next is Spark Accuracy with the GM58x @ .25 degree OR the GM 24xe @ 2 degrees. (2500 RPM Acceleration Rate)
THINK of this EXAMPLE: A LS Turbo with the 24xe, automatic shift (1st-2nd) with drop of 2K RPM, the WOT Spark Instant WILL ADVANCE by TWO DEGREES !
THUS my answer is NONE
Lance
We have customers that use my controllers/coils in Paris, TX. that run 12:1 CR at WOT, 1800 RPM for 25K hours with LS. (constant operation )
The fuel used is Natural Gas.
My record for a Test Engine is the use of a Subaru EJ-20 with 14.5 C.R. (14 .lbs turbo boost) bench dyno ran, used to teach others about E-100 (E-fuels)
The second greatest race in the world is Pikes Peak with the start at 9,000 ft to 14,000 ft.
This application, N/A, requires a 18:1 C.R. as common, another example. (my customers)
My Method : Turbo C.R. Selection = Static Ratio x Density Ratio.
Example of 14 .lbs = a 1.5 Density Ratio = 9.5 x 1.5 and is a 14.25 C.R.
Next is Spark Accuracy with the GM58x @ .25 degree OR the GM 24xe @ 2 degrees. (2500 RPM Acceleration Rate)
THINK of this EXAMPLE: A LS Turbo with the 24xe, automatic shift (1st-2nd) with drop of 2K RPM, the WOT Spark Instant WILL ADVANCE by TWO DEGREES !
THUS my answer is NONE
Lance
12-31-2017, 09:20 AM
#13
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That's because my times suck because of no traction and having the 10 bolt. Never got a decent nitrous run, but running n/a it ran 12 at 121 with a 2.0 60ft. It's a heavy pig as well at about 3850 lbs with me in it. Once I change the rear i'll throw a good tire on and let her rip
Now from a roll it's a beast. Was barely edged out by a turbo f-body that traps 138, and I beat a 650 rwhp KB 03 Cobra that traps 131. It's got the power I just need to hook it up
Now from a roll it's a beast. Was barely edged out by a turbo f-body that traps 138, and I beat a 650 rwhp KB 03 Cobra that traps 131. It's got the power I just need to hook it up
12-31-2017, 03:15 PM
#14
The most important number to look at is your dynamic compression ratio. For pump gas NA you need to keep this under about 8.75. There are good programs out there that help you calculate that. Once you know your static compression ratio, you can play with cam timing to keep this number reasonable.
01-01-2018, 06:38 PM
#16
Originally Posted by farmington
Like asking what's the best brand of gasoline.
11.5 NA (includes spray) - because that is about the max you can get away with on pump gas.
9.5 FI - because that is what my 4.8 is stock and I have no intention of replacing anything internally.
01-01-2018, 07:47 PM
#17
The masses will use gasoline and have mild builds, it's obvious they are looking for a general rule of thumb mass production compression ratio. They aren't going to cut an off the shelf mass head for 30 different setups.
Some of y'all are acting like it's Trick Flow's first day on the job and doesn't know fuel, DCR etc are all important lol.
Some of y'all are acting like it's Trick Flow's first day on the job and doesn't know fuel, DCR etc are all important lol.
01-01-2018, 08:01 PM
#18
The masses will use gasoline and have mild builds, it's obvious they are looking for a general rule of thumb mass production compression ratio. They aren't going to cut an off the shelf mass head for 30 different setups.
Some of y'all are acting like it's Trick Flow's first day on the job and doesn't know fuel, DCR etc are all important lol.
Some of y'all are acting like it's Trick Flow's first day on the job and doesn't know fuel, DCR etc are all important lol.