blown 944

Todd when you get a chance maybe you could log some MAF voltage. I think would be cool to compare considering we have similar setups.

toddk911

Datalogging has been my top priority lately as I had to upgrade my old Zeit has been giving me wierd problems (had it for 8 years) and got the new model on the way.

I am also curious to use the maf V to compare to the cfm/hp based on my transfer function table I have. Not sure how accurate it will be as a means to calculate hp but fun to try. lol

I should be able to post some good data next week.

4.907V 1,741.36KG/HR 835.85CFM 557HP
4.639 1,474.92 707.96 472
4.443 1,302.05 624.98 417
4.248 1,145.04 549.62 366
4.053 1,002.62 481.26 321

blown 944

look at my sig

toddk911

Nice!! I know our transfer fuctions should be pretty close.

I dug up some old data logs I did and at about 19psi or so I was seeing about 4.4-4.5 give or take.

Based on the chart at 4.7 you would be about 480-490 at the crank. Does that sound right to any dyno's you have done?

toddk911

Wow, I just found this. So maybe my method is more accurate than I thought. lol

"Another note, since CFM is a direct relation to HP this is how a computer can/will calculate the torque the motor is making at a given RPM.(one way how torque management works/is calculated)

It takes 1.5 CFM to make 1 hp

Knowing this, you can take a mass air voltage/reading from your MAF and calculate how much HP your engine is making.(But again only if you know the meter and meter curve is accurate) .

Believe it or not this is how top fuel teams figure out how much HP their engines make(Hard to dyno an engine making 5000hp plus HP, no dyno can really read that high, until maybe the last couple of years) They measure how much CFM the engine is moving and then calculated that into HP."

blown 944

I havnt dynoed this car other than one where my ts crossover was being a brick wall and my BOV reference line was cracked. That one really doesn't count bc the MaF reading was only 4 volts and only made 315 hp. However that would seem to correspond to your chart. I plan on taking it back down pretty soon. On my other car at about the same boost (maybe a little more) it made 430 something. That didn't have the tb done though, which added a decent amount of voltage. Right now I'm just using the voltage to gauge the changes I make.

That was a good amount of voltage you were seeing at 19psi.

Rogue_Ant

Just a note: If you have a sharp transition from the Lightning MAF to a smaller diameter pipe, then the MAF will typically read a little bit high...
Not a huge issue, but might be a little misleading if you are trying to extrapolate HP from MAF voltage.

blown 944

Good to know. I suppose though, it doesn't matter if I am just using it for a reference for changes made on the same car?

toddk911

Sid: Sounds good! Also, are there maf voltage issues due to your elevation?

Josh: I was hoping you would post on this topic. lol. Your note might be why I am reading that high of v even at only 19psi? Or do you think I was about 420-440hp at the crank on 19-20psi which would validate those voltage readings as accurate.

Also, if I am getting slightly higher false v readings, how will that affect my tune?? Wouldn't I always be over rich?

Or is the variance of readings very small? i.e. .05 or something?

Rogue_Ant

Sid, you are correct. If you are using it to reference changes, then that will work great!

Todd, the only way to truely know the amount of variance would be to flow the MAF w/ intake pipe vs the MAF w/ 4" intake pipe... If I can get some time, perhaps we will do just that with Sids setup.
Most likely the amount of variance isn't large, thus it might run slightly rich, but not significantly.

Your reading of 4.4v should be about 43-44lbs/min worth of airflow. Which is right in-line with what I would expect your setup to make for HP.

blown 944

Todd I may be able to validate the last question pretty soon as I think I'm gonna grab a piece of 4" pipe today and make a new tree pipe. My turbo inlet is 4" so that should be a non issue. Probably have some results next week to show.

toddk911

Older logs @19-20psi:


11A/F 5592 4.41v
11 5620 4.39
10.9 5675 4.45
10.9 5675 4.33
10.9 5703 4.39
10.8 5731 4.39
10.8 5760 4.37
10.8 5760 4.43
10.7 5789 4.37
10.7 5818 4.41
10.6 5848 4.43
10.6 5878 4.41
10.7 5878 4.39
10.7 5908 4.37
10.7 5908 4.49
10.7 5938 4.45
10.7 5938 4.45
10.7 5969 4.39
10.7 5938 4.45
10.8 5938 4.51
10.7 5969 4.49
10.7 6000 4.43
10.6 6031 4.47
10.5 6031 4.45
10.5 6095 4.47
10.5 6063 4.61
10.4 6095 4.53
10.4 6128 4.55
10.3 6160 4.53
10.3 6160 4.51
10.3 6160 4.49
10.2 6194 4.49
10.2 6194 4.47
10.2 6194 4.51

86 951 Driver

Just curious how long have you guys been running C Tune? And has it been running well?

CyCloNe!

Well guys after hours of thinking I've realized my MAF Tree is a tad short and will have to finish up later (maybe tomorrow). I still have it connected to the j-boot and it runs great I also didn't have a filter and that was part of my problem, also when the fans kick on it messes with my MAF readings since the MAF is right there so once I get it on the right side it should be perfect from what I can tell.

blown 944

Ha ha, I've been running it for.... Well a long time if you consider Josh has worked with me for 3+ years. The lighting MAF I have had on for about a year I think.

It runs great!! I should not be the one to ask though since I've been involved. From what I understand though my tune now is the m-tune just using the lightning MAF.

What I can say though is this thing runs very smooth. Actually smoother than my bone stock talon.

Cyclone, I'm very sure that you were having issues due to not having a filter on. With tge fans right there I bet it was worse than mine was.