SD2 tuning

[good2win22]

Brad, you could get this.  Larry, I'll defer to Steve on those questions.

Here's a log of a quick test drive this evening.  3rd gear pull with alky sprayingand I have the boost controller backed all the way out and the actuator arm just sliding over the puck arm..  This is the lowest boost I can go with unless a get a weaker actuator.

As you guys can see, there was a slight bit of KR when I pulled the tranny down into D and then it went away.  Converter locked at 91, I had it set at 90, and that thing felt like a rocket.  AFR correction was adding some fuel but not much and I can adjust that since I'm still on the default fuel parameters.

This is kind of fun again!

Almost forgot to tell you guys.  To view the log in the SD mode, select 768 grams on the config page and open up the tune page

[TexasT]

Couple questions. I unloaded the file into the plc window and there it was already set to the 768gr/sec. I ran it back n forth a couple times. I'm guessing the maf reading is a computer calculated gr/sec as there is no maf. I did notice it never got to half of 768. Only about 360 or so. I guess that gets to 720 calculated.

Next i got the tune thing to come up. It has several tables including target afr, ve and spark. I'm guessing the top row is rpm and the left column is for the calculated half of the gr/sec. Also there is a football shaped thing that moves around I think showing where the computer is using the table at the time.

Am I close?Pretty cool stuff. I'm hoping to understand much of this powerlogger when I'm able to afford one. Im still having fun with the new to me scanmaster.

[Steve Wood]

yes, the maf numbers are calculated...

In the mass air flow cars we have maf flow and rpm from which we can compute Load (lv8)

As we have no maf in the speed density cars, we have manifold pressure and rpm....

I suspect that Eric is backing an equivalent maf number out and using that to compute LV8

I suspect a really reliable map sensor is a benefit in order to have consistency.

Fueling is a 3d process as Load is not consistent with any one thing so we must come up with a means to vary fuel depending upon need since it is not linear with rpm And we need to be able to vary it with conditions...T hat's the reason I complain when guys are trying to tune their cars at part throttle for wide open throttle conditions.

[good2win22]

Drove the car up to Fort Worth yesterday for Charlies service and noticed something on the way back with the MAP numbers. Vacuum increased on the way home. As in at an idle it was a higher negative number and was cruising at a higher negative number. Before at idle I was pulling 15-17. Now it's pulling 17-18. cruising vacuum was higher as well. I don't mind the increase except that it affects the fuel pressure and thus affecting the AFR correction. It's not a pain but I had spent some time going thru the VE table setting the individual cells for drivability at cruise and part throttle to get the AFR correction to +/- 5%.  Now all those corrections are jacked up. Will have to do the individual cells again.


Any thoughts on why the MAP numbers changed?

[Steve Wood]

When the weather changes tomorrow, or the underhood heat is different, you may get another set of readings.

Are you watching your analog boost gauge numbers vs your PL numbers?

[good2win22]

When the weather changes tomorrow, or the underhood heat is different, you may get another set of readings.

Are you watching your analog boost gauge numbers vs your PL numbers?

Watching every guage I have Steve. Analog vacuum matches the PL. Last night I was experimenting with the cooling fan on and off during highway cruise.  Then noticed the increased vacuum numbers. Ambient temps were in the high 70's coming home. Not a real huge difference in density altitude from driving up in the mid 80's.

[TexasT]

If the be table gets to need different settings for more temp, how does the factory adjust its table to compensate for change in the temp? I guess this feature isn't includes in the sd2 software?

[nocooler]

vacuum numbers shouldn't matter - once you tune those cells I'd think it'd be good. vacuum changes at cruise so you tune those cells and move on. Its a process. It's not the fuel pressure moving around. 45psi base is 45 base it doesn't matter if you are in vacuum or boost.

[good2win22]

vacuum numbers shouldn't matter - once you tune those cells I'd think it'd be good. vacuum changes at cruise so you tune those cells and move on. Its a process. It's not the fuel pressure moving around. 45psi base is 45 base it doesn't matter if you are in vacuum or boost.

I agree that base fuel pressure set with the vacuum line off is constant but when the vacuum line is connected back to the FPR, would you agree that fuel pressure drops?  I have seen the fuel pressure drop as much as 8 psi at idle when the vacuum line is connected. I have also seen fuel pressure drop as much as 10 psi when in a deceleration configuration. As in letting off the throttle and coasting without depressing the brake pedal. Look at your vacuum guage the next time you coast.  I've seen mine as high as 22 when coasting.


With the increase in vacuum, the SD2 is now running in different cells on the VE table at varying speeds, MAP, tps voltage and at a lower fuel pressure.  With that being said, I can either adjust the quick tune BLM cell for low and mid boost levels which may or may not adjust the AFR correction in that particular cell to my preferred correction tolerance or I go and adjust each cell on the VE table individually to get my preferred AFR correction. It is a process either way.


With the explanation above, I would have to disagree and say that it does matter when you're in a vacuum condition and agree that it doesn't matter as near as much when under boost.

[Steve Wood]

Obviously, fuel pressure drop depends on the amount of vacuum under varying conditions.

However, the amount of fuel variation to maintain a desired light throttle A/F due to your variation in vacuum is very small given the lean A/F and the low air flow.

I think you are looking at the science and forgot the size of the reality   One can get really discouraged if one pursues the science without considering its importance given the reality.  I might change my mind if your goal is the Mobil Mileage run

[nocooler]

You need to think about both sides of the injector. The fuel pressure drops on the regulator, but there is more vacuum in the manifold pulling on the injector. It all equals out.


The entire VE table will need to be tuned, and once it is - you'll be good.

[Steve Wood]

You need to think about both sides of the injector. The fuel pressure drops on the regulator, but there is more vacuum in the manifold pulling on the injector. It all equals out.


The entire VE table will need to be tuned, and once it is - you'll be good.

Yep, that is the most salient point.  The injectors are constantly held in balance with reference to the hose off setting.

[good2win22]

You need to think about both sides of the injector. The fuel pressure drops on the regulator, but there is more vacuum in the manifold pulling on the injector. It all equals out.


The entire VE table will need to be tuned, and once it is - you'll be good.

Didn't think of the opposing side.  Good point. That coincides with what Bison was saying about the increase in compression means an increase in MAP behind the throttle blades.


Would the ideal ambient conditions to tune the VE table be at sea level and 15 C?

[good2win22]

Sure would be nice if you were able to select a primary cell, adjust it and then have the cells around it adjust accordingly. Maybe it's just wishful thinking....

[Steve Wood]

Only so much memory in the chip