half-n-half

iTrader: (7)

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

half-n-half

iTrader: (7)

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

txhorns281

iTrader: (12)

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:

half-n-half

iTrader: (7)

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

Russ K

iTrader: (1)

My 2001 ZO6 cam/header car with 404 rwhp is .80 g/cyl at 1800 ft altitude.
Lower altitude = more g/cyl. Lower IAT temp is denser, so more g/cyl air.

Russ Kemp

jimmyblue

iTrader: (11)

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.

silverTA2002

iTrader: (1)

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.

txhorns281

iTrader: (12)

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.

RedWS6 00

I get about 0.60 g/cyl, is there something wrong with my car?

RedWS6 00

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?

joecar

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...)

RedHardSupra

iTrader: (1)

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.

ringram

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)

RedWS6 00

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?

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.

RedWS6 00

Thanks for the idea, my ECT was reading was 178*F on both days.
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.

RedWS6 00

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.