Battery voltage/ PW offset - SRT Forums

duster360 · 08-28-2009, 03:47 PM

Do you guys make sure you change this table too when swapping injectors or using a different calibration that would use a different injector?

Is this table a pw(us) adder?
Im thinking it is since you'd need more pw at lower volts, because the injector solenoid is slower to react.

Every different injector(03, S1, S2) shows a different pw adjustment vs battery voltage. Which makes sense, since they should react slightly differently.

I scaled mg/pw from my original 03 to match the S1 I've been using. (Yes, I double checked the values,3 times)The wot A/F became much leaner than I had anticipated. It change a good 1.0-1.3 A/F leaner. Also closed loop LTFT is trending more positive then i think it should.(+10-+15%, max of +30% but only between shifts)

Not only is the Batt/Pw table not quite right for the injectors, I also bumped the Alternator voltage up to ~14.2v, which throws this off a bit more.

I'm just trying to judge the impact of having this table different.
I know you guys have never seen a 03 pcm so i'll post a pic

2003 5029242AI

S1 for refference

**Mana4real** · 08-28-2009, 05:25 PM

Hmmmm... I never changed that... I wonder what it would do to my tune now

TDSAaron · 08-28-2009, 05:48 PM

I change it for the injectors that I have good data on like RC750's and some others. Some cal id's have a hissy fit if you even touch that table. I'm not positive why but I'm guessing maybe it's template related.

When tuning Ford's via SCT (which I've done for years) and GM's via EFI Live I always change the battery offset tables to match the injector being used.

apexcrazy · 08-28-2009, 05:53 PM

Im using rc650cc injectors on a stage 2 code , flows roughly 10% more than stage2 . That , and I am running an e85 mix at 33% , requireing a 10% increase in flow . Although these changes sorta nullify each other , I still had to pull fuel out in closed loop , & adjust power enrichment to get a 12.0 AFR at WOT . I did notice a lean condition during tip-in & spool up , so I adjusted my "accelerator pump" tables , which seemed to help .
I did not adjust batt.volt/pwm tables . If we were to adjust this table , would we pull a % of pwm out account for the bigger fuel charge ? If so , would the same % as injector rescale be a good # to start with ?
Now that you bring it up , I would think e85 would require an adjustment to account for the extra fuel needed . We rescale the injector PWM to flow more fuel , but should we rescale batt.volt/PWM for ethanol as well ?
I guess it comes down to knowing if the batt.volt/PWM calculation happens before or after the fuel charge / PWM calculation happens , when the ECU is determining ultimate fuel charge .
My AFRs seem great right now , but if the ECUs "model" is off , I would like to correct it , then re-adjust my injector scaling & enrichment tables to match what the more accurate model wants .
BTW Im self taught at this stuff , so please correct my ignorance , if possible .

nutz · 08-28-2009, 06:47 PM

i dont know if it helps but AEM did some extensive data testing on a ton of injectors you may be able to interpolate the data

**Mana4real** · 08-28-2009, 07:00 PM

Quote: Originally Posted by nutz

i dont know if it helps but AEM did some extensive data testing on a ton of injectors you may be able to interpolate the data

Do you have anymore information? Or do you have any idea where this info is posted?

nutz · 08-28-2009, 07:08 PM

Quote: Originally Posted by Mana4real

Do you have anymore information? Or do you have any idea where this info is posted?

down load the EMS pro software and look at the injector wizard

AEM EMS Software

TDSAaron · 08-29-2009, 07:48 AM

Here's a good list. I've used some of these before and they come in pretty close.

Injector-Rehab - Lag Times

**Mana4real** · 08-29-2009, 12:02 PM

Awesome information guys!!! Thank you very much for sharing!

duster360 · 08-29-2009, 11:54 PM

Thanks guys,,,

It sounds like the consensus is, at least by practice and less by theory, that rarely anyone changes these values.

So my abnormaly odd shift in LTFT and wot A/F might NOT be due to these values being off a bit.

SpecJ · 08-30-2009, 03:06 PM

taking a look at that data from injector rehab, it seems to be pretty far off from the PCM's actual data as the voltage increases.

EDIT: I can't even modify this table. My prp seems to be getting an error.

duster360 · 09-01-2009, 08:19 AM

Here's DS/Brian's take on this table:
(guess I should have checked the tuning guide first,,thats right PRPers, DS offers up a tuning guide)
Just for kicks I'm going to make sure it matches my injectors.

Quote:

Functions>Fuel Injector will be Fuel Injector Offset Vs. Battery Voltage
This will be one of the most important tables to modify for engine response in relation to throttle percentage. Unfortunately the only place these normally come from are the manufacturer of the fuel injector. Bascially what this table does is give the variance for pulsewidth compensation at different voltages. Meaning when the voltage is low how much to add to keep the injector flow the same because it take more pulsewidth for a 1000cc/min injector at 10 volts than it does at 12volts where it’s designed to operate same with higher voltages. This table is strictly for the PCM but it will impact off-idle and part-throttle response quite a bit.

**If there is no Offset values available it’s best to start out with about 25% of your multiplier. Say if you had multiplier like we just calculated then you would take 200*.25=50% that I would start by adding to that table until you can get the proper offsets

You will also need to get the minimum pulsewidth from the manufacturer as well it is located in Scalars>Fuel Injector
If you can’t get that like the offset you can take your multiplier that you used for your injector calculation and apply that to Cranking pulsewidth vs. Fuel Mass and Minimum pulsewidth

(oh man SpecJ is going to have a field day) lol

SRT-What? · 09-01-2009, 10:18 AM

*off topic*
Can we get access to this tuner guide on the DS forum or we need an special account ?

*back to topic*
Could that also explain the lean spike at low rpms ?

duster360 · 09-01-2009, 10:57 AM

Quote: Originally Posted by SRT-What?

*off topic*
Can we get access to this tuner guide on the DS forum or we need an special account ?

*back to topic*
Could that also explain the lean spike at low rpms ?

Sounds like it'll cause some tip in issues

Sorry info is CMR only.

SebringLX · 09-01-2009, 01:23 PM

I have about a half dozen 2003 PT Cruiser's that I've tuned, many of them run the Stage 1 injectors. I have always matched batt/pw tables on the 03 code to the S1 code, never tried it without matching them.

I did the same on an '04 PT that added Stage 2 injectors and 3 bar sensors, made the batt/pw table match what is in the Stage 2 code.

The only thing I haven't done, is adjust this table when going to any injector that was not available as either stock or with a stage kit (i.e. when going to 750's).