ECMlink DSMLink : MAFRaw vs. MAFComp

[zippyshoe]

The scenario would then be:

450/1000 - 1 = -55% global fuel (Both flow ratings at 43.5 base fuel pressure.)

This figure is pretty close to Bruce's actual global fuel value (-54%).

 

[oldman]

Both of you raised a very good point which implicates that the DSMLink manual is wrong, I want to get some test runs in before it gets too late, I will sit down and think about it some more later. In the meantime we need verification of whether 450s in a 1G is flow tested at 37 or 43.5 psi. Because of this, I'm going to hold off on re-calibrating my 2Gmas and only focus on AFR tuning tonight.

 

[zippyshoe]

I did some more researching on this issue and found that the 1G injectors are indeed flow-rated at a fuel pressure of 43.5psi, as eclipzed indicated. Hence, on a factory 1G, the "450cc" injectors are actually flowing at 415cc/min. What complicates matters is that somehow the 1G ECU accounts for the fact that the "450cc" injectors are operated at 37psi fuel pressure. So to calculate the global fuel value for a new injector size while maintaining stock fuel pressure, the following formula still holds true (for both 1G's and 2G's):

factory injector flow rating/new injector flow rating - 1 = global fuel value

So in the case of 1000cc injectors (flow-rated at 43.5psi fuel pressure), we have

450/1000 - 1 = -55%

This would be the value if the base fuel pressure were maintained at factory (37psi). But now if the fuel pressure is increased to 43.5psi, this yields

450/1000/sqrt(43.5/37) - 1 = -58.5%

This shows how the initial global fuel value is leaned-out a bit due to the increased fuel pressure. This value matches-up with the value that Bruce initially calculated. It seems that the situation is more complicated for 1G's because the injector rated fuel pressure differs from the fuel pressure they are actually operated at.

 

[oldman]

Damn it children.... Back to square one.

Did some test runs at 23psi, as soon as I go below 10.5:1, I start to see some knock between 1 to 2 degrees after 6500rpm. Oh well, tomorrow is another day, I'm getting too old for doing full 3rd pulls on the highway.

 

[2gGSX]

I always thought the manual was funky on that in that it doesn't account for the difference in base fuel pressure. However, if your LTFTs and STFT end up working out with the settings you had then I don't see any reason to change them--after all, that is your final goal in setting global and deadtime (and to some extent, the airflow readings).

 

[oldman]

I always thought the manual was funky on that in that it doesn't account for the difference in base fuel pressure. However, if your LTFTs and STFT end up working out with the settings you had then I don't see any reason to change them--after all, that is your final goal in setting global and deadtime (and to some extent, the airflow readings).

The manual is correct because 450 is flow tested @43.5psi.

I know that I'm good to go as far as global is concern, I just want to make sure I'm not compensating for incorrect airflow reading by short changing my injector size, 85cc is a lot, at least in my book. Remember my boostest is off comparing to my map, my WB readings is also slightly off comparing the 1G estimates on the fuel table (about 3-4 10ths leaner), everything seems to point to my 2G mas not reading correctly.

Let's pretend that my MAF is in fact reading less than actual across the board proportionally, it would account for lower global, lower boostest and leaner real AFR under WOT, wouldn't you guys agree?

 

[2gGSX]

Bruce, I just found your log (d'oh!).

The only time you have to be concerned about your BoostEst reading is when VE is at 100%, which should be ~5500. Based on that, and the assumption that your VE is at 100% above 5500 (due to your SMIM and 63mm TB), I would recommend adjusting your airflow at 1600 hz to +6% based on the data at t=7.61s.

Refer to this post if you want the reasoning: http://www.dsmlink.com/forums/showpost.php?p=148103&postcount=6

 

[oldman]

I don't like to just do things without fully understanding it, guess it's more reading for me....school sucks!!

 

[2gGSX]

Bruce, I also just noticed your TPS needs adjustment.

Scale should be 114%, TPS Offset should be -1. Put key on accessory power and play with the throttle while displaying RawThrotPos. With the throttle closed TPSvolts should be .63v and at WOT TPSvolts should be 5.00v.

Refer to: http://wiki.dsmlink.com/default.aspx/DSMLink/DSMLinkTPSAdjustment.html

Your fuel and timing maps do look a little weird, although your 70-90 time is 2.8 seconds which is roughly ~110 mph give or take about 5 mph.

Nothing else is too obvious to me, so I'll wait for the new WOT log when it comes.

 

[oldman]

Scale should be 114%, TPS Offset should be -1. Put key on accessory power and play with the throttle while displaying RawThrotPos. With the throttle closed TPSvolts should be .63v and at WOT TPSvolts should be 5.00v.

Refer to: http://wiki.dsmlink.com/default.aspx/DSMLink/DSMLinkTPSAdjustment.html

So I can either physically adjust my TPS so my TPSvolts reads .63 OR use the TPS dialog, is that correct.

Your fuel and timing maps do look a little weird, although your 70-90 time is 2.8 seconds which is roughly ~110 mph give or take about 5 mph.

Nothing else is too obvious to me, so I'll wait for the new WOT log when it comes.

That log was before any fuel tuning and boost was turned down to 17psi for the sole purpose of setting my VE table, I really want to experiment with MAF calibration first before I go all out on WOT tuning, I will post a new WOT log in a few days. Thanks for the help so far Tom.

 

[zippyshoe]

Not to beat a dead horse , but another way to think about the global fuel calculations as they pertain to 1G's is like this:

FIC 1000's at 37psi fuel pressure will actually flow:

1000cc/min*Sqrt(37/43.5) = 922.27cc/min

Since 1G factory injectors at 37psi fuel pressure actually flow

450cc/min*Sqrt(37/43.5) = 415.02cc/min

then the following formula could be used to calculate global fuel for FIC 1000's installed on a 1G:

415.02/922.27 - 1 = -55%

If we now increase the fuel pressure to 43.5psi, we get

415.02/922.27/Sqrt(43.5/37) - 1 = -58.5%

So we end up with the same results as my previous post.

That poor horse...

 

[zippyshoe]

Damn it children.... Back to square one.

Did some test runs at 23psi, as soon as I go below 10.5:1, I start to see some knock between 1 to 2 degrees after 6500rpm. Oh well, tomorrow is another day, I'm getting too old for doing full 3rd pulls on the highway.

Bruce,
I noticed in the DSMLink log included in the DSMLink post that the RPM-based timing sliders are not all zeroed-out - it looks like some timing is added in the upper RPM ranges. I was wondering if this was intentional? From what I hear, the 1G's have a pretty aggressive timing map compared to 2G's.

 

[2gGSX]

The way I did my TPS adjustment was first to make sure that the throttle plate actually physically opened all the way with the pedal pushed all the way down. After that, I just did the fine tuning in DSMLink's TPS adjustment so the ECU was seeing 100% reading.

The first time I did this in my last car (RIP), the plate would physically open all the way, but for some reason the ECU was only seeing 60% throttle with the throttle depressed (wiring? throttle cable too loose? alien hamsters under the hood?). Either way, after the adjustment I gained 3 lbs/min on an Evo 3 with NOTHING else changed.

Get going on that MAF airflow adjustment! If you have a real VE map of your setup you should be able to compensate for the not-100%-VE at the other points of BoostEst reading and calibrate the airflow sliders with those readings against your MAP sensor. You're best off asking Tom/Dave since I'm not sure anyone else knows the exact way VE is applied to the BoostEst calculation, although I suspect it's just a matter of multiplication.

 

[oldman]

Bruce,
I noticed in the DSMLink log included in the DSMLink post that the RPM-based timing sliders are not all zeroed-out - it looks like some timing is added in the upper RPM ranges. I was wondering if this was intentional? From what I hear, the 1G's have a pretty aggressive timing map compared to 2G's.

That was my poor attempt to try and keep an upward curve from 15* to 18* between 5-8k.

The way I did my TPS adjustment was first to make sure that the throttle plate actually physically opened all the way with the pedal pushed all the way down. After that, I just did the fine tuning in DSMLink's TPS adjustment so the ECU was seeing 100% reading.

I'm pretty sure the TPS diaglog adjustment via Link is for aftermarket throttle bodies as per Link manual. My TPSvolts is currently at .59 which is inline with the FSM adjustment, I have not touched my TPS since my mmcd days which showed 10.1 % with my old 1G logger.

Get going on that MAF airflow adjustment! If you have a real VE map of your setup you should be able to compensate for the not-100%-VE at the other points of BoostEst reading and calibrate the airflow sliders with those readings against your MAP sensor. You're best off asking Tom/Dave since I'm not sure anyone else knows the exact way VE is applied to the BoostEst calculation, although I suspect it's just a matter of multiplication.

It will have to wait a couple of days, I just started my Dodge B350 van suspension project, pitman arm, inner and outer tie rods, upper and lower control arm ball joints, all with hand tools on my driveway , I'll have my hands full for the next couple of days.

 

[2gGSX]

Aftermarket throttle bodies especially need TPS adjustment, however stock ones seem to go out of spec as well. It wasn't off by a wide margin like mine was, however it's something to keep in mind. RawThrotPos of 32 without touching the gas pedal, and 255 at WOT is what you want to aim for.