looking for someone with a bit of knowledge on the caliber srt4 platform. I have some questions and can't seem to get/find what i need.
looking for someone with a bit of knowledge on the caliber srt4 platform. I have some questions and can't seem to get/find what i need.
Just post up your questions, not everything you might need to ask is caliber specific
mg/stroke. what the heck is it, how can i convert it to another unit.how do i tune if i dont understand what mg/stroke is. My tuner was no help, he said to read a engine building book..... i have went through my histogram and changed the axis to psi but it gives me 30psi at wot throttle yet my boost guage only reads 23.
there are multiple tables that have mg/stroke but i can not adjust anything because no one seems to be able to tell me how to calculate/convert
Cylinder Volume (in Cubic Centimeters - Divide Engine Displacement in Liters by number of cylinders, then multiply by 1000) * VE * Weight of air (1.225 mg/cm3 @ Sea Level and 15*C - actual weight of air will change with elevation and temperature) = mg/stroke
So, quick example, take a 5.7L Hemi. Let's say that we need to adjust WOT timing for this Hemi due to noticing knock, and for whatever reason, we're unable to log mg/stroke through the PCM (which shouldn't be an issue for most platforms - but for the sake of argument, let's pretend such is the case). Let's say that this Hemi has a VE of between .85 to .90 at a 1.0 Pressure Ratio, and at an RPM range of 3000 - 5000. For simplicity sake, we'll also assume we're at sea level, and pretend we have an air temperature of 15*C, just so we don't have to account for anymore variables for the quick and dirty example I'm giving here.
Here's where the previously mentioned formula comes into play. Cylinder Volume (in Cubic Centimeters) * VE * Weight of air (1.225 mg/cm3) = mg/stroke
5.7 L / 8 cylinders = .7125 L per cylinder. Let's multiply by 1000 to make it mL (which, in terms of volume, translates directly to cm3). .7125 * 1000 = 712.5 cm3 per cylinder.
712.5 cm3 (volume of a single cylinder) * .85 (low end of the VE range) *1.225 mg (weight of air) = 742 mg/stroke
712.5 cm3 (volume of a single cylinder) * .90 (high end of the VE range) * 1.225 mg (weight of air) = 786 mg/stroke
So, with that, we would know that we need to adjust the timing in the range of 742 - 786 mg/stroke (I would expand that range to something more along the lines of 725 - 800 mg/stroke, just to cover your bases).
You start adding boost into the equation, you have to increase your air density by however many BAR of boost you're pushing through the motor, plus you have to account for changes in air density due to aircharge temperature. So, you would need to start looking at Ideal Gas Law to figure out where your actual air density is.
So the question becomes, with all the hassle that is involved in converting from mg/stroke to something more along the lines of typical speed density variables (MAP vs RPM and IAT) to correlate it to, why not just log your mg/stroke to determine where you need to make adjustments?
I wish it was that easy, when I go to add mg/stroke to the log there is no such option. So frankly I don't know what to do
Does it log any type of realtime airflow?
There should be something like "Air Load" or "Dynamic Cylinder Air" or something of that nature. I don't have my scanner with me now, but there should be a value like that available. If not, contact support to request it be added.
Jaime
ok ill look this evening. Thank you
being on e85 should allow me to run more timing from my previous tune on 93 correct? right now i have less timing than the 93 tune from what the tuner said, but wouldn't turn it up, said my motor would blow???? My thought is this.......If i was running more timing on 93 there should be no reason why i cant run at least the same amount on e85 correct?
it logs KPA.......but when i take that value and convert it to psi its only like 17 but my gauge says 23
217 kpa converted to psi is 31.47 - 14.7 for atmosphere = 16.77
What's your elevation?Originally Posted by bosstin87
P.S. 100 KPA is equal to 14.5 psi, not 14.7.
Last edited by B00STJUNKY; 09-27-2016 at 03:38 PM.
6.562' elevation
the 14.7 is referring to 1ATM (atmosphere) rounded up from 14.695. If i remember correctly map should read boost + 1ATM = absolute pressure right?
If this is the case 23psi (boost) + 14.7 (ATM) = MAP sensor reading.
Last edited by bosstin87; 09-27-2016 at 05:15 PM.
No, MAP sensors read in BAR, and 1 BAR is equal to 100 kPa. So, 217 kPa = 31.465 psi. From there, you subtract your atmospheric pressure to get your gauge pressure. Your atmospheric pressure is NOT 14.7, nor even 14.5. At 6500 ft elevation, your atmospheric pressure is only about 11.5 psi.
So, 31.465 psiA - 11.5 (atmospheric pressure) = 19.965 psi Gauge.
You're seeing 23 on the gauge, maybe you didn't catch the same glimpse on your log as you did visually on your gauge, or your gauge could just be off by a couple psi.
6.5 feet not 6500
Ah, well, that makes a little bit of difference. LOL
Your gauge pressure should be closer to 17 psi, then, assuming your MAP sensor is reading accurately.
spike 24 holds 22-23. there is no way I'm at 17psi, thats why i am so confused lol
Grab a log and make sure you capture your entire pull, including the spike and the full pull to redline.
ok so i got a full log, there is no air load or dynamic cylinder air to add to the table for the log, log doesn't see boost. i read it off my gauge only
What do you mean it doesn't see boost? Post up the log!
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