Dynotech Tuning

iTrader: (12)

I don't do a great deal of SD tunes these days but I started to dive into more this week so I can get a better grasp on things.

I did notice today that if I change the injector scaling, it seems to change the MAP sensor VE calibration I had dialed in (load vs KPA, not the RPM VE table). Anyone know why the injector scaling would have any direct connection to this?

-Jamie

Spec-Ops1

iTrader: (38)

I would assume that the ecu uses injector scaling to calculate base IPW, and it changes VE much like it changes fuel trims on the maf...

211Ratsbud

iTrader: (1)

Sd creates a fake maf signal right?

Dynotech Tuning

iTrader: (12)

I'm not talking about the fuel VE table, I mean the load you see from the MAP sensor. I dialed in the SD map using the same injector scaling as the MAF rom. Before I made the switch, I recorded a 5mb log of me cruising to get a good load/kpa comparison, as well as Airflow HZ. I then matched the SD tune to mimic the exact same load characteristics as the MAF produced.

The car runs amazing but the rpm VE table was near 150% so I lowered the injector scaling and the VE table to 100%. With the same fuel trims, the simulated LOAD shifted down from 30 at idle to 18. I then went halfway back to my original settings and the load went halfway between the two. Clearly, the same IPW is happening in both scenarios.

Does anyone else seem to have to lower their injector scaling more than their MAF tune?

-Jamie

Dynotech Tuning

iTrader: (12)

If there is a table that says "this kpa value equals this LOAD value", one would think that nothing should change.

-Jamie

charlie.tunah

iTrader: (7)

Did the car in question have a large amount of maf scaling done to it previously? And maybe the SD isnt using that scaling anymore so the load shifts?

03whitegsr

iTrader: (8)

Sounds like you changed the MAP VE table from ~150% down to 100% and then changed injector scaling by 33% (1500cc down to 1000cc for example)?

This then changed the load by about 40% (30 to 18)?

Dynotech Tuning

iTrader: (12)

Basically, yeah.

-Jamie

charlie.tunah

iTrader: (7)

Arent the rpm and map ve tables used together to simluate MAF airflow as 211 said above? (after your clarification, my questions above are irrevelant...) And if that is the case, wouldnt you expect to see a load change when changing either table? Your response above seems to indicate one is used for load and one is used for fueling. And is a rpm ve of 150 a reason to suspect something is not setup right?

FWIW...Ive never used previous maf logs in any of the SD tunes Ive done on my car or my buddy's, so I cant comment from experience. Just trying to understand the intricacies of it all.

JohnBradley

iTrader: (30)

FWIW-

I set up SD with know MAF injector scaling. I leave the RPMVE more less the same for all setups except at idle and above 7k where most turbos start to fall off. MAPVE is also more or less the same at WOT. I set it up so that load equals psi, so 200 is 20.0, 300 is 30.0, etc.

I havent noticed the scaling drastically affect load though especially when I take a 2.0L and adjust the scaling for lets say a 2.4 (20% difference) or E85 (30%).

Aaron

wreckleford

iTrader: (2)

Maybe I am missing something, but if you lower RPM VE, wouldn't you expect load to go down also since RPM VE is also used in the load calculation?

Dynotech Tuning

iTrader: (12)

I assume the VE table is nothing more than an IPW multiplier? I guess the better question to ask is what parameters are used to calculate LOAD and how do the SD patch items connect to this calculation directly?

-Jamie

JohnBradley

iTrader: (30)

I have noticed MAPVE has far less effect on changing load than RPMVE. I normally max the RPMVE values at no more than 105. On one car I had them up to 130 (early days, mind) and the load at 25psi was 354-365 instead of what I see now around 250. The other thing that was odd was that the IDCs were 160% at an 11.0.

I think scaling is like in the AEM, micro-sec bit or a base IPW and then as you commented the others are multipliers with varying affect.

I guess if I mathed it out I would know, but I am willing to short hand it being a direct percentage increase.

Dynotech Tuning

iTrader: (12)

Basically, the way I have been tuning it with good results is by making sure the logged load matches the KPA curve I recorded with the MAF. s long as they follow the same path, I haven't had any drivability issues at all with it, identical to MAF. I just tweak the MAPve table to hit my mark and that seems to get me where I need to.

-Jamie

03whitegsr

iTrader: (8)

MAPVE and RPMVE calculate load and they both have an equal part in the equation. Upping MAPVE 10% is the same as upping RPMVE 10%...more or less.

Load and injector scaling are then used to calculate IPW.

If you drop the VE table 50%, and then reduce the size of the injector scaling by 50%, yes, it will keep IPW (mostly) the same while having a huge change on load.

Your method of matching SD Load to MAF Load is a good plan. If you greatly change the loads seen, it will move you around in the fuel and ignition tables. Also, below a load of about 90, there are lots of little calcs going on and if the load is out side of an expected window, it can have erratic results.


To answer your question though, changing injector scaling does not change the MAPVE scaling, persay. It simple changes the fuel delivered at a given load, which then means you have to go change the VE table to correct for it. SD in this case is kind of superficial as the ECU is not calculating a fuel requirement table based on true engine VE. You are simple adjusting the VE tables to get the AFR you want.

The stock ECU has several tables in it though that could be used to make the setup very VE based though. Like an injector linearity table for pulse width requests under 2ms.