The car seems to run well right now. it has a cartek stage II package which included pcm tuning. I installed a Findanza Alumn flywheel and gained a LOT of power.

But the car is giving me error codes now. Like PO172-po174 and stuff.

I just got an ls1 edit. And I need the car to have as much power as possible for the Nationals in Topeka KS next week.

Any thoughts and or suggestions on what I should/need to do?

 

You have to start by calculating the IFR table. There are some formulas for it maybe send horist a pm and he can steer you in the right direction

 

You need to find out what your LTFTs are and adjust your IFR table, accordingly, so the LTFTs are around zero. If you multiply the IFR table by a percentage greater than 100%, you'll be telling the pcm that you have bigger injectors and need less fuel, and vice-versa.

 

That works for the Maf table. If you multiply the IFR table by a number greater then 100% you are telling the car to add more fuel actually.

 

Wrong... greater than 100 leans it out less than 100 richens it up

 

Now that I think about it you are right. I was thinking that multiplying it by greater then 100% will increase your ltrims which is essentially leaning the car out in cruz mode but making it run richer in pe mode if your ltrms do not zero out. Thanks for pointing that out.

 

Basically the formula people seem to use is your new injector flow rate @ 3 bar / old injectors @ 3 bar

so depends on what kinda car you have and the year...

I'm not sure if the GM Injector ratings are 3 bar or 4 bar...

98, 01, and 02 F-Bodies were 28lb/hr
99 and 00 were 26 lb/hr

I'm not sure if GM did anything diff w/vettes

When I was scaling mine I took
42lb @ 3 bar, and then 26lb @ 3bar (00) and and came up w/a factor of 1.62

I tried it also assuming 26lb/hr was already 4 bar, and came w/a scalar of 19x% which caused the car to run like poop.. way too lean

the 1.62 * 100 = 162% scalar worked much better for me..

So I'd just do 30/old injectors as a starting point
so either 30/26 = 1.15 = 115%
or 30/28 = 1.07 = 107%

Use this as a starting point, then get your LTRIMS back down to 0

 

Exactly, you're telling the pcm that the SVO 30s are 100+whatever percentage larger than the stockers. In my case it worked out to x122%.

 

Just remember that the SVO 30lb injectors are calculated @ 30lb @ 43.5psi
Your car's default fuel pressure is 58 psi. That means your 30lb injectors are really 34.64 or (35lb) injectors now.

If you take a default 98 IFR Table:
0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 KPA
3.62 3.64 3.66 3.69 3.71 3.73 3.75 3.77 3.8 3.81 3.84 3.86 3.88 3.9 3.92 3.95 3.96


And modifiy it for the 30lb injectors @ 58psi:
0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 KPA
4.36 4.39 4.41 4.45 4.47 4.5 4.52 4.55 4.58 4.59 4.63 4.65 4.68 4.7 4.73 4.76 4.77

 

So what is the % difference in flow from 28.8 lbs/hr to 34.64 lbs/hr ?
Sorry my math sucks

 

start , programs, accessories, calculator

34.64/28.8 = 1.203
so the 34.64s are scaled 120% .. 20% larger than the 28.8s

that's assuming the 28.8 is 4 bar (58psi) and not 3 bar...

As I mentione dabove... when I scaled my IFR table, when I assumed my 26lb injectors were 4 bar, and my 42s were 3 bar... I converterd the 42s to 4 bar and did the calculation and it had me scaling by 190% ... when I put it in and logged the car was WAY lean... whereas 165% was a tad rich...

 

Well that is exactly the issue, we all know 01-02 injectors are rated at 28.8 BUT the question is at 3 or 4 BAR??

How can we be sure???? Who really has that info 100%?

I use a handheld that requires a % flow adjustment for injector swap.

So Horist, could you tell me 20% flow difference is on the ball?

 

According to the math ... and assuming both are rated at 4 bar... then yes... will a 20% increase in your IFR table result in a good tune? that I dunno and I don't know if 20% is on the ball...

The formulas are just simple mathmatics... % difference between 2 numbers...

i can give you what the formulas yield... but I dunno if stock injectors are rated at 3 bar or 4 bar... also even if you go by the formulas... that's a starting point... still requires logging and retuning... if the handheld unit only lets you adjust the IFR table... best you can do is start low and go high and see what yields the best results (still need a logger to get useful data) just remember the more you scale the leaner the car runs...

 

In addition to above IFR scaling I tried the injector offset scaling values presented by NoGo here :

https://ls1tech.com/forums/showthrea...ghlight=offset

and they worked great for more even ltfts. I also tried the excel sheet that has been around but the results sucked real bad. Most people scale the IFR table for ltft anyway, so what horist suggested for IFR is a good way to go. You will fine tune anyway.