Horsepower/Torque VS CylAir (g/cyl)

[slo895.0]

Sorry if this has been asked before, but i cannot seem to find a clear answer.

Is there a correlation between and engine HP/TQ and CylAir (g/cyl)? Meaning Higher CylAir (g/cyl) = higher HP or TQ, or is there a better way to monitor performance gains/losses in the scanner...?

I ask because i have made some minor changes in my setup recently such as length of intake, and different injectors and seen a change in my CylAir (g/cyl). My current CylAir (g/cyl) max is 2.25 and i see an average of 2.15ish during a 4th gear pull.

The "curve" of my CylAir (g/cyl) seems to match/mimic a torque curve for what that's worth.

Car in question is a 2010 CTS-V with Heads, Cam, Pulleys, & E85.

Thank you

[schpenxel]

There are some really rough values out there that you can use for ballparking HP from MAF or VE airflow, but they are truly rough estimates only. The problem is running leaner/rich or more/less timing doesn't change the result of these formulas at all, so it's really a ballpark estimate at best.

I doubt there's an accurate way to do it by airflow. There's no way for that to take into account fuel and spark, which both have a significant effect on output

[slo895.0]

Thank you schpenxel, i wasn't looking for a way to calculate my HP/TQ from CylAir (g/cyl) but more of a confirmation that it does correlate to HP/TQ. Meaning if that value goes up, then my HP/TQ has increased and vice versa... make sense?

[slo895.0]

I feel if the CylAir (g/cyl) value correlates to HP then it is a useful tool when street tuning a car. Long story short i lengthened my intake tube to place my air filter in a "better" location (in front of the brake duct) and my CylAir (g/cyl) values dropped to and average of 1.95 average from 2.15 average. this was after adjusting my MAF calibration table.

Also does using the "multiplier" method of inputting injector data larger than 127lb/hr (e67 ecu) affect the CylAir (g/cyl) reading seen during a data-log?

[schpenxel]

Depends what you mean by multiplier method.. if you mean doubling stoich/halving IFR, then no, shouldn't effect airflow values. If you mean scaling all of the airflow tables, etc., then yes

It's a tricky thing to get precise results from. I messed around with what you're doing a while back but it's tough to say whether the changes in g/cyl that you're seeing are because the air is hitting the MAF different, MAF calibration is different, or it really is just more airflow

Can't hurt to keep messing with it and learning though.

[mowton]

g/cyl defines the mass of air that is "determined" to be entering the cylinder. I say "determined" because there isn't a sensor for cylinder charge, rather it is calculated from several other parameters, the major one being the Mass Air Flow sensor or in Speed Density the VE/Coefficient table. After all the filters and adjustments, the final answer is called Dynamic Airflow (DAF). In my training I recommend developing a new Cylinder Airmass equation which substitutes MAF for Dynamic Airflow or Dynamic Cylinder Airmass (DCA). This is essentially a corrected g/cyl based on the final calculated Airmass calculation and is what the PCM ultimately uses for spark and other Cylinder airmass referenced tables.

Over all, the higher the cylinder airmass, the higher the power should be. Attached is a page from our tutorial which shows how the PCM can calculate the G/Cyl and you can see MAF, Dynamic AF, VE etc all form a part of its equation.

Ed M

[slo895.0]

i am referring to the method of inputting larger injectors (FIC1300's for example) by using say FIC 1000's flow data in the flow rate vs pressure table. Then you divide 1300 flow rate by the 1000's flow rate and input that value in the flow rate mult vs volts.

Example input 14.399 (1000's flow rate @ 58psi) in the flow rate vs pressure table. Then input 1.243 into the Flow Rate Mult. vs Volts table. 17.896 (1300's flow rate @ 58 psi)/14.399 (1000's flow rate @ 58 psi)=1.243
This of course assumes you are using a boost/vacuum referenced FPR.

[slo895.0]

Thank you Mowton

[mowton]

You can not get the PCM to operate any higher than 127 lb/hr and using multipliers won't increase that hard coded limit. This will throw off all your airmodels as you "fudge" (or do a partial scale) to get the Air/fuel ratio correct. The PCM will lock its flow values to the hardcoded 127 limit....As Carson has said, you can either Double the stoich/half the IFR and IVT Terms, or do a complete re-scale.

Ed M

[slo895.0]

You can not get the PCM to operate any higher than 127 lb/hr and using multipliers won't increase that hard coded limit. This will throw off all your airmodels as you "fudge" (or do a partial scale) to get the Air/fuel ratio correct. The PCM will lock its flow values to the hardcoded 127 limit....As Carson has said, you can either Double the stoich/half the IFR and IVT Terms, or do a complete re-scale.

Ed M

thank you again, i do not currently use this method, but i have in the past ... That does answer a another question i had been wondering about, if the aforementioned method actually worked in increasing the computers ability to read injectors larger than the hard coded limit, so thank you.

[schpenxel]

I agree with Ed. No matter how you try to do it, the absolute max injector flow rate (after all the multipliers, vacuum, boost, etc. are applied) value that the computer can use is still the same.. so that method will not work in this case. You'll still be limited to whatever the max your inj flow rate table says is the max. Now, you could do say 50lb/hr injectors and put the multiplier at 2 and that would work.. but only because you're still under the 127 limit.

Easiest way to use large injectors (imo anyways) to just double stoich to 29.x and cut the real injector flow rate in half. Cut the IVR term tables in half as well and you are done..