80s to 125 injectors now very lean

[jpwalt1987]

I just swapped out a set of 80s for a set of 125 Bosch injectors from TT. I made the changes to the injector pph setting on the parameters page. The car would start but as soon as it would fire off and run for just a few seconds. I saw that it was going extremely lean on the AFR. I verified fuel pressure was at 45 line off. To get the engine to stay running I had to increase the injector offset number from 28 to 49 and then i also had to increase the VE table in the idle area of 50kpa. I went from 47 on that area to 57 just to get it to idle with zero Air fuel correction. I took a drive and the AFC was pegged at +30% almost the whole time. It doesnt seem right to have to raise the VE numbers up so high to make the AFC come in line. This is an SD2 chip that was burnt for E85 and 80s, the only change now being swapping to 125s. Are there parameters hidden in the background of the program that cant be changed by the end user regarding injector behavior? Any advice is appreciated. The car went 11.58@125 at BG last week on E85 and Alky. I went to the 125s to get away from having to use the alky as a make up fuel.

Thanks!!

 

[EricM]

You will need much more injector offset for those injectors. You will need to enter the data manually in the extra tables.
First, set the injector offset parameter to "5".
Then go to the Tables section, and scroll down to "InjOffst". Enter the info below (the ms numbers):

V ms
0.0__3.500
1.5__3.500
3.1__3.500
4.6__3.500
6.2__3.500
7.8__2.600
9.3__1.980
10.9__1.550
12.5__1.330
14.0__1.260
15.6__1.190
17.2__1.100
18.7__1.100
20.3__1.100
21.9__1.100
23.5__1.100
25.5__1.100

 

[EricM]

You can bump the numbers up or down (the ones around 12.5 to 14.0 volts) until your VE is back where you had it.

 

[jpwalt1987]

Thanks so much Eric!!! I figured there was more to it than just the PPH input on the parameters page. I'll try your instructions and see how it works out.