01cherryreds10

iTrader: (9)

I finally had the chance to sit down and watch the Calibrated Success DVD and understand HPT a little bit more. It is a huge help and already feel motivated to get the wideband installed and start re-doing my tune.

I had my car re-tuned by the same guy who did it when I first built the car, I changed the intake, cam, converter, maf and injectors this time so it was alot of stuff to change. Well I sat down last night and looked at the injector data and compared it to the data I found for Bosch 36lb injectors, and it wasn't even close really. The tuner was having issues getting it to run correctly with the MAF originally until he was able to get a wideband on it.

My question is, should I change the injector values to what I have found online, and then re-do my MAF and VE tables accordingly?

I had a couple driveability issues which included the car wanted to die after doing a burnout at the drag strip, and would have a bucking feeling when cruising around 45ish when the converter would lock up

Thanks everyone

MUSTANGBRKR02

iTrader: (91)

The injector data in that DVD is not a end all be all.

Bowtie316

iTrader: (1)

I would want my injector data to be correct, all of the fueling calculations include flow rate so it will mean having to basically start over with the tune.

I will say that you need to be careful when looking at flow numbers online that you take fuel pressure into consideration. Sometimes advertised flow ratings are based at different pressures than what your combination runs at.

Tally TransAm

iTrader: (17)

agreed

edcmat-l1

iTrader: (10)

None of your issues are going to be caused by the injector data being off slightly. A 36 lb injector, you could tune on stock 28 lb injector data and it would run perfectly fine. The MAF and VE tables would be off by a certain percentage, but it would run just fine.

NicD

iTrader: (7)

This. Also some of that data doesn't appear to be all that accurate either for some of the injectors.

01cherryreds10

iTrader: (9)

The injector data for the Bosch 36lb injectors wasn't on the disc I received so I ended up going on the HPT forum and finding a thread with the data.

Any ideas what I should be looking at for the issues I'm having?


Here is the tune

jimmyblue

iTrader: (11)

Tuning lore has evolved over time. Used to be that people would
try to trick the MAF to get a desired AFR outcome. But that had
downsides such as it gets learned out in closed loop and jacks
WOT fueling, burns up A4s, and so on.

Then the conventional wisdom drifted to "mess with the injector
table instead, that only affects fueling". True in a sense, other than
that two wrongs seldom make a right.

I prefer to pursue realism, and things that are known or knowable
ought to be represented straight up. Injectors are one such.

But injectors are at the mercy of things like fuel pressure, which
is an embedded assumption. That wants checking, and a new fuel
filter before tuning is never a bad idea.

Alvin@PCMofNC

No kidding. The Injector data on that CD is FAR from right and should be labeled as an assumption at best in the first place. He makes the argument that injector data is provided by Ford so it is some simple math to get it to fit GM tables. That is far from the truth. The Injector data given by Ford does not include pressure regions or even albeit less importantly voltage regions that GM operates at.

I spent about a week building a spreadsheet that helps me extrapolate Ford data into GM regions. Extrapolate is a fancy word for best guess as to where data is headed. IE if you where given 2, 4, 6, 8, you would expect 10, and 12 to be next. It was tough and had I not had the math background I do it would have been just about impossible.


Anyway here are some snippets from how my excel sheet fits GM data into the 5 arrays that Ford injector data gives you. Notice I haven't even begun to talk about the 4 constants Ford gives you and how it fits GM data. That is a entirely different story.



The Ford Data as given is plotted as the baby blue lines. The maroon lines are where I best fitted the curves in GM data. Notice how in 4 of the graphs they do not even over lap? That is because Ford gives injector data between 20 psi and 60 psi. GM starts at 58 psi and goes to about 70 psi (injector pressure differential 80 kPa vac ~ 12 pounds.)



As a professional tuner this has been very valuable to me because it adds a tremendous amount of consistency in my tuning when injector data is correct. It helps our mail order tuning be as accurate as possible, which is very important, but for the simple DIYer fudges in the injector data will likely be soaked up into the VE table and MAF table and you will not even know it's off. What I'm getting at is it will not be the end of the world. If you run a sensitivity analysis on how the injector data errors would effect your tuning you would see that it would make a pretty big difference at idle, decel, and really light cruise. Beyond that it will not make much of a difference.

01cherryreds10

iTrader: (9)

Sorry guys, should have included this in my first post.

The injectors are Bosch 36lb injectors, and the data is not even on the disc of the CSI DVD. I found the injector data here:
http://www.hptuners.com/forum/showth...b-hr-injectors

I'm going to venture back over to the HPT forums with a log of the car wanting to die at a closed throttle situation along with my tune and hopefully someone can give me a good direction to go to. I wish the DVD spent less time with EFI Live and more time with driveability adjustments