Bigger injectors...what do I need to change?


May 30, 2001
I recently upgraded my injectors from 55lb to 84lbs. I changed the injector setting in the Speed Pro program. Is there anything else I should change as well....(I obtained the original program settings from a friend with a similar set-up). Do I need to mess with the VE table or any other table for that matter?


You may need to raise or lower your injector opening time, and I would expect that you will need to do some minor tweaking on the VE table as well. It really shouldn't take a great deal of work to get the car dialed back to where you had it with the 55 pounders.

Thanks for the reply Craig...

As always, you are a great help:)

I played with the V/E table a bit and also tweaked on the injector opening time. I had read bigger injectors tend to take a little longer to open so I changed the reading from 1ms to 1.5ms. The idle became noticeably choppier. I returned it back to 1 ms and it smoothed out.

I went to bigger injectors due to a data logg showing the 55lb going 98 % on duty cycle (although I was getting a good a/f ratio of 11.5 to 1 at full boost). Did I do the right thing?

Again thanks for the reply!!

Yup... sounds like you made the right move upgrading the injectors. You were all done with the 55 pounders.

As far as making the changes in the software to tune the car, just give it what it wants. If you read somewhere that they "should" be set to a 1.7 mS opening time but the car runs better at 1.0 mS, you are again doing the right thing by leaving it at 1.0 mS.

Happy tuning,