I've had a set of flow matched 24 lb lt1 injectors sitting in my garage for over a month now and my 350 has been running like crap since i put it in earlier this year - the plugs fouled out last week - according to datamaster my car is running way rich at lower rpms and lean as i climb over 4000ish (which i expected with the stock 19 lb injectors) anyway i ordered my pocket programmer today so i've finally (after fearing this board since i got my car in late 97) have decided to become apart of it...

my question pertains to gmecm edit and something odd i encountered with inj flow rate and a few bins - the 305 bins i have come upon so an inj constant of 3.11 grams a sec. 1 pound = 453.59237 grams - so that would be roughly 24.7ish (not 19) lbs per hour - i look at the 350 bins and they are 2.77 grams per sec which equals 22 lbs (which is right). 3.02 would equal about 24 lbs a hour so would it be right to set it as so?

also i should change the cylinder size if what i infer from readings is correct - though for the life of me and many hours now of combing the program along with clever search entries here, i can't seem to find where i do that. I have a feeling that this is very simple and im overlooking it - please take my noobness to heart.

I'm also going to plug in the VE tables and such from a 90-92 l98 bin - then the tuning begins .

any other words of advice would be much appreciated - I hope my plan of attack is both sound and practical.

 

Glad to see you've got over your "PROM board phobia"

I'm not familiar with the setup you're working on (it would be good if you could post the .BIN, the ECM number and the .ECU file or Tunercat file your using- but others here will know these anyway I s'pose).

What I have found is that the L/gram per second injector constant is really K*Cylinder litres/ flow rate in g/s, and you've got to back-calculate the K. For example my 1.8 L 4 cylinder using '808 code has KINJFLOW = 0.1 with approx 22 lb/hr injectors.

I've found the best thing to do is just proportion the injector constant from the original known injector flow rate and cylinder size. If your injector constant is in Litres/ g/sec, not just in g/s (and I don't know whether or not that's the case), then your new constant would be 3.11*(19/24)*(305/350) = 2.146 (this is only true if your constant is NOT 3.11 g/s, but 3.11 L-sec/g.)

So anyway, let me know what Bin/ ECM / ECU you're using so that if I'm wrong, I can check it for myself as well as seeing what the comments to follow say . If you're really lucky, you might see Grumpy bark at me :lala:

John

 

The injector flow constant is based on sec/gram of flow, the inverse of grams/sec:

CNST = (1 / grams_sec) * 256 * 5

Cylinder size constant:

RBob.

 

I was wondering where the cyl vol was too. AUJP BTW
It's not listed in my ECU - 7730v3 from Mansur's site.
I'm assuming it's missing other things too. Things I don't know I need to change yet.
Is there a more complete ECU available or does everybody make there own?

So w/GMECMEdit, you just add an ECU item correct?
How do you know the element size?
The address thing threw me for a sec.
It's actually 86DD-8000 correct?
The calculated value came up 159 so I assume it's correct.

Do I need to change the injector flow constant also when swapping injectors?
What's the address?

Edit: 41C... Never mind, didn't realise that GMECM Edit did the inversion for me,
I'd already switched to 36lb injectors and thought I needed to do something else.

 

element size is the size of the item you're adding in bytes. 1 = 1 byte, 2 = one word (two bytes).

address is the offset of the first byte in the item in reference to the *beginning of the chip* in hex.

 

ecu file i'm using is 7730v3.ecu

with DIY-efi down i had to get my bins from

http://www.eecis.udel.edu/~davis/z28/

AXXD

and

AXXC

are the ones i've decided to go with since all the manual jagon is intact

i was going to pull the tables out of AUJP

 

ok i got the cylinder size and inj constant right thanks guys