a question about airflow...
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a question about airflow... hey guys i am curious what kind of dynamic cylinder air a strong running car moves...
My trex car with mods in sig is saying that it moves .77g/cyl...
That for some reason does not seem like that much.. but the car pulls like the crazy...
Any info?
Thanks
Louie
My trex car with mods in sig is saying that it moves .77g/cyl...
That for some reason does not seem like that much.. but the car pulls like the crazy...
Any info?
Thanks
Louie
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i just checked an older log with my stock cam and it was moving .87 grams/cyl with stock cam and same mods...
am i missing something...
Also my logging frames are much longer now and i am not getting a real precise reading like before.
edit something else i just though of... before IATs were 37 degress F...now they are in the 90s F...
Thanks
Louie
am i missing something...
Also my logging frames are much longer now and i am not getting a real precise reading like before.
edit something else i just though of... before IATs were 37 degress F...now they are in the 90s F...
Thanks
Louie
Most stock cars I've seen pull around .6, most bolt on cars can get up to the deep .7s, most cam-only cars I've seen pull between .8 and 1.0 g/cyl. I suppose it all depends on the motor, here's a few to compare:
My stock Z06:
My old H/C/90mm TA:
My stock Z06:
My old H/C/90mm TA:
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ok that is cool...but how greatly does the IAT affect that...i am sure that it is a lot. I konw that my car makes a ton more power than it used to...yet says it is taked way less air...but at 100F what can i expect?
Louie
Louie
And all of this is just derived values from the sensor
data (MAP*VE(), MAF), so any tuning there can add
some degree of uncertainty.
I saw mid-.8 values before headers, but with a clean
intake tract and gutted cats, SLP Y & CME exhaust
(stock cam). At sea level.
IAT should be a minor player, affect the SD airflow
calcs only, at (T1+273)/(T2/273) ratio (gas law).
Kelv9in / centigrade basis. 30 degrees C making
about a 10% difference.
data (MAP*VE(), MAF), so any tuning there can add
some degree of uncertainty.
I saw mid-.8 values before headers, but with a clean
intake tract and gutted cats, SLP Y & CME exhaust
(stock cam). At sea level.
IAT should be a minor player, affect the SD airflow
calcs only, at (T1+273)/(T2/273) ratio (gas law).
Kelv9in / centigrade basis. 30 degrees C making
about a 10% difference.
I have honestly no idea what it really means, but....
With just headers I pulled .73 max
Heads/cam/headers .76 max
Recent tune after tuning SD, no MAF I saw .80 at only 4k rpms. I haven't exported a wot log to excel recently.
With just headers I pulled .73 max
Heads/cam/headers .76 max
Recent tune after tuning SD, no MAF I saw .80 at only 4k rpms. I haven't exported a wot log to excel recently.
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g/cyl is calculated from the VE function as jimmyblue said, higher VE values make higher g/cyl. In tandem with that, higher airflow efficiencies will raise VE values, which in turn shows higher g/cyl. I suppose this is why we see g/cyl increase as we modify our motors ability to "breath." IAT is one of the variables in the VE function, but other variables will make a bigger impact on VE calculations as they move around.
Last edited by txhorns281; May 22, 2006 at 08:24 PM.
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How strange, justed look back through some old logs and I have reached 0.8g/cyl, about 4 months ago, since then I have changed the headers.
Does it look like I have an intake leak after the MAF or something?
My VE has changed a little so my fueling os pretty spot on now. Could changing the VE effect the g/cyl as much as 0.2?
Does it look like I have an intake leak after the MAF or something?
My VE has changed a little so my fueling os pretty spot on now. Could changing the VE effect the g/cyl as much as 0.2?
Last edited by RedWS6 00; Jun 15, 2006 at 02:20 PM.
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So for example, how much difference would headers make to the g/cyl compared to stock...?
After installing headers, what differences in VE would you expect...?
(...I am trying to sanity check myself...)
After installing headers, what differences in VE would you expect...?
(...I am trying to sanity check myself...)
headers i've seen make changes from 0.03 to 0.08g/cyl in the midrange, and next to nothing up top. on the VE table it's much more visible tho, i've seen 10 points + change on stock -> LT's on a 224 cam in midrange.
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This is one of the values I am using to gauge my tune and power. I used to get 0.80 stock with bolt on's with a pretty beefy tune. Cam and heads now Im at 0.87, Im aiming for 0.95 or so with my girly cam (+20% power over stock)
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Okay my car was reading .80 g/cyl at WOT @ 5500 RPM back in Feburary, the MAF reported 26lb/min of air.
Done a run last night, the most I get is .60 g/cyl @ WOT @ 5500 RPM, MAF still reading about 26lb/min of air.
Why has my g/cyl gone down, how is it calculated?
I'm trying to think what mods did I do at the end of Feb, I beleive I played with the IFR table buy that cant be it surely. I havn't touched the MAF table. The VE table seems the same in that area since Feb.
I'm puzzled why my g/cyl has dropped so much.
I have desreen the MAf and no calibration afterwards, could this be the cause?, if so, why am I still seeing the same lb/min as always?, isn't g/cyl worked out from lb/min?
Done a run last night, the most I get is .60 g/cyl @ WOT @ 5500 RPM, MAF still reading about 26lb/min of air.
Why has my g/cyl gone down, how is it calculated?
I'm trying to think what mods did I do at the end of Feb, I beleive I played with the IFR table buy that cant be it surely. I havn't touched the MAF table. The VE table seems the same in that area since Feb.
I'm puzzled why my g/cyl has dropped so much.
I have desreen the MAf and no calibration afterwards, could this be the cause?, if so, why am I still seeing the same lb/min as always?, isn't g/cyl worked out from lb/min?
Last edited by RedWS6 00; Jun 16, 2006 at 09:44 AM.
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Might depend on your charge blending etc. Its a lot warmer now. IAT is probably in the 30 or 40*c whereas in feb you might have had 10*C etc.
Warm air is of course less dense. Hence why cold air intakes etc are so important amongst other things.
Going from 0*C to 25*C makes about 10% difference in air density.
Check out the calculator half way down this page http://wahiduddin.net/calc/density_altitude.htm
Mind you, thats about 30% out, check your IAT at the time.
Warm air is of course less dense. Hence why cold air intakes etc are so important amongst other things.
Going from 0*C to 25*C makes about 10% difference in air density.
Check out the calculator half way down this page http://wahiduddin.net/calc/density_altitude.htm
Mind you, thats about 30% out, check your IAT at the time.
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Originally Posted by ringram
Might depend on your charge blending etc. Its a lot warmer now. IAT is probably in the 30 or 40*c whereas in feb you might have had 10*C etc.
Warm air is of course less dense. Hence why cold air intakes etc are so important amongst other things.
Going from 0*C to 25*C makes about 10% difference in air density.
Check out the calculator half way down this page http://wahiduddin.net/calc/density_altitude.htm
Mind you, thats about 30% out, check your IAT at the time.
Warm air is of course less dense. Hence why cold air intakes etc are so important amongst other things.
Going from 0*C to 25*C makes about 10% difference in air density.
Check out the calculator half way down this page http://wahiduddin.net/calc/density_altitude.htm
Mind you, thats about 30% out, check your IAT at the time.
IAT in Feb was 54*F at the time of reading .80 g/cyl @ 5000 RPM @ WOT
IAT yesterday was 59*F at the time of reading 0.56 g/cyl @ 5000 RPM @ WOT
i tihnk I descreened my MAF around that time, I'm beginning to think that is the cause. Havn't rescaled the MAF, as after the SD tune and plugging in the MAF the AFR%Error didn't really show up any error.
Last edited by RedWS6 00; Jun 16, 2006 at 10:44 AM.
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Just done a short log. Still maxed out at .56 g/cyl. Looked at 5000rpm, measures 23.90lb.min.
I took the MAF off, looked at it, and its has quite a bit of black dust over it. I rubbed it very carefully with my finger just to get some of that stuff off.
Run another short run, it maxed out at .68g/cyl, measured 27.02lb/min at the same speed/RPM, IAT was 4 degrees warmer too.
So thought I'd post my findings, if you get low g/cyl, check your MAF is clean. I have cleaned it throughly now, and will try to do a log tommrow, hopefully I'll be back uo to measureing .80g/cyl.
I think there may have been a small air leak between the air box and the MAF, therefore unfiltered air getting in.
I took the MAF off, looked at it, and its has quite a bit of black dust over it. I rubbed it very carefully with my finger just to get some of that stuff off.
Run another short run, it maxed out at .68g/cyl, measured 27.02lb/min at the same speed/RPM, IAT was 4 degrees warmer too.
So thought I'd post my findings, if you get low g/cyl, check your MAF is clean. I have cleaned it throughly now, and will try to do a log tommrow, hopefully I'll be back uo to measureing .80g/cyl.
I think there may have been a small air leak between the air box and the MAF, therefore unfiltered air getting in.