7427 upgrade tuning help understanding

[dave w]

daily driver in my case. Well my truck see's maybe 5-6000 miles a year. 90% is highway miles and the motor is 2yrs old. ultimately this will be a toy almost at that point maybe 1 more year. Then a saturday fun driver and the track. only see's 93 octane since I built this motor and usually see 13-15mpg depends if I go past 50% throttle.
I am looking on the site and around the web is there a 7.4L bin for $0D so I can do a compare with my bin just for the throttle body air difference between the stock and the 50mm bored one I have. I have seen a few but $0E so can't use the compare function.

$OD is for the 4L60E, $OE is for the 4L80E

The factory did not use the 4L60E with the 7.4 liter.

Using two instances of TunerPro (side by side) is required to compare a $OD .bin file vs. $OE .bin file. Parameters from a $OE .bin file can be copied / pasted into a $OD .bin file.

dave w

[typhoonss92]

so after reading about tbi injectors and their vast difference in flow rates for the same injector size and thinking about the 65# injectors I have. even though the place I bought them said the flow is 73 @ 12.5, I rethought this and tried 70@13psi with the bump up to 21psi is about 88. I put that in the injector flow in the chip and it makes a huge difference, I also now get 75dc% at max rpm over 60dc% I was getting. I still think I need a little more fuel pressure but debating on how I will go about that since there is no spring between 23-27psi range, bigger injectors or external vfpr. The only thing I see kinda odd is idle map at 50-60 maxes out the ve table, actually above but it wont go that high. The other thing I am working on now is dfco. It seems to surge off throttle in deaccell. Is there any advice on the closed throttle timing table or should it be the saame as the open throttle table.

[brian617]

I still think I need a little more fuel pressure but debating on how I will go about that since there is no spring between 23-27psi range, bigger injectors or external vfpr. .

I'm running the 94-95 big block spring @ 22 psi with the matching pump in the tank.

[typhoonss92]

besides the injector flow being changed when you up the psi or put in bigger injectors is there any other perameters or tables that need to be changed

[brian617]

Obviously you will have to fix your VE table, but generally you can get it close fast by lowering or increasing the whole table to counter the pressure difference. I my experience with using TBI injectors at higher than normal pressures, AE acceleration enrichment needs work.

[typhoonss92]

thanks Dave and Brian.
Yes I have had to up the AE which made considerable difference and also PE a little. I have worked and reworked the VE tables as I make changes. I test, datalog run the log in history tables see what needs changed, then put csv into daves excel change the idle and off idle ve tables from the wbo2 sensor data, check for actual knock that has pulled timing, these knock sensors are very sensitive.
I have the 65pph copcar injectors and the site I got them from sayd they flow at 73@12.5 which I think is bs. That is why I had my injector flow at 98 which calculated for the HP I am putting out would be correct, but I was only getting 65% injector duty cycle and 5200rpm 100kpa. which lead me to believe they do not flow that high. I changed my cacluations to 70@13psi with my fpr at 21 so I made the injector flow rate 90. this made a huge difference no skipping at high rpm just riped thru the rpm and dropped almost 2 sec off my 0-60 but injector duty cycle was only 75% which leads me to believe they really flow 65@13psi aproxx. I tried dropping down to 85 for the injector flow and it was so rich at idle it was trying to stall so I put the prior chip backin. The only place I am maxing out the VE table is at or right off idle 800-1000 rpm then everything else is fine. Not sure why it would want more fuel at idle than anywhere else. well guess I will tune and test and repeat.

[Kitch]

Something doesn't sound right, I don't think you should be maxing out your VE table just off idle and then requiring less VE under higher load/RPM.

If I was setting up for a larger sized injector or different fuel pressure I'd nominate a value that I'd want as max DC% under W.O.T and max RPM, say 85% and then carefully test run to make sure the Wideband AFR at 95-100 Kpa/max RPM were around 12.2- 12.5 range.
That establishes a baseline for max fuel requirement, once I had the VE adjusted to achieve that AFR (VE's in that range around the mid 90's rather than 100%) I'd then work back tuning the rest of the table from there.
That's just how I'd look at doing it anyway.

[dave w]

besides the injector flow being changed when you up the psi or put in bigger injectors is there any other perameters or tables that need to be changed

The Injector Offset Tables are parameters that are important for tuning.

The screen shot below shows injector offset tables from 94 Pickup with a 4.3 $OD and a 94 Pickup with a 7.4 $OE. There is "Internet" information the 94 7.4 (28 PSI) uses the same injectors as the 94 4.3 (13 PSI). If the "Internet" is correct, then the fuel pressure difference between the 13 PSI 4.3 injector vs. the 28 PSI 7.4 injector would account for the differences in the injector offset tables?

dave w

[dave w]

The Injector Flow parameter is one of the most import parameters to determine in the tuning process.

What an injector is rated to flow vs. what an injector is actually flowing vs. the injector flow parameter programmed in the chip are not always the same flow number.

When a VE table correction is calculated to be greater than 100, one tuning option is to correct the injector flow parameter. The injector flow parameter is used by the computer to determine the injector Base Pulse Width (BPW). The larger the BPW value the more fuel the injector is spraying into the engine (for example a BPW of 6.3 milliseconds is spraying more fuel than a BPW of 4.4 milliseconds). When the VE table correction value needs to be greater than 100 the BPW needs to be larger so the injector will spay more fuel into the engine.

The downside to changing the injector flow parameter when tuning, is ALL the previous "Tuning" is invalid and the "Tuning" process has to start ALL OVER again. Increasing the fuel pressure regulator spring has the same effect on the "Tuning" process as changing the injector flow parameter.

The example below is a "Perfect Injector" that is rated to flow 72 lbs / hr, actual flow has been measured @ 72 lbs / hr with E10 fuel, and the .bin file is programmed for 72 lbs / hr. The perfect injector does not exist on any known make / model / year vehicle!!! The perfect injector is a MYTH!!

A common "Tuning HACK" to correct for an IMPERFECT INJECTOR, is to trick the computer to increase the BPW by changing the injector flow programmed into the chip.
Lowering the injector flow from 72 lbs / hr down to 70 lbs / hr will INCREASE BPW.

The injector flow "HACK" has limits of about + / - 4 of the rated injector flow. For the example above the injector flow hack limit is between 68 lbs hr to 76 lbs hr. Injectors with lower rated flow will have a lower hack limit, example an injector rated to flow 22 lbs / hr will be about + / - 2 lbs / hr.

dave w