Nitrous jetting and SCT tunes, with Zex or NX wetkits...
 

Hey guys,

I've done three cars now on the dyno using nitrous and found that when you use a SCT tune with the nitrous that the jetting specs from Zex or NX are one size to small on the fuel jets.

For example, when using a 75 shot this weekend we used the recommended 26 fuel jet and 40 nitrous and it gave us a A/F ratio of 12.8-12.2 which in my book is too lean. When we used the next step up fuel jet, the 30 fuel, we ended up with a nice 12.0-11.0 a/f ratio.

Like I said before this has happened on every Nitrous application that I've loaded a tune onto at the dyno. So from this information I would recommend that if you are using a SCT tune and haven't had the a/f checked then I would run the nitrous jet for the recommended shot you want to use and the fuel jet for the next size up. This will bring you down to a proper a/f ratio, maybe a bit rich but its better to be rich then lean.

Now this information doesn't replace the need for a dyno session to check a/f ratio's with nitrous. I would always recommend this.

Below is a dynochart from this weekend with a 75 shot, the first run with the recommended jets and the second with the larger fuel jet. I've tested this all the way up to a 150 shot, I couldn't find the dyno runs but he made 420 rwhp with it. I've got a email into the dynoshop for the runs.

Thanks, Doug.

Same power with a better A/F !!! Can't beat... I need to place a call to you Doug for a tune on my wifes A/T 06 GT...

Good work...

Most of my auto owners with FI report nearly a 2-3 tenth gain with my tunes. Gotta love my converter lock up scheduling :)

I'll be calling you soon... :metal:

some of us N/A guys have picked up a ton with your tune also!
best before doug=12.62 @110 with doug's tune 12.29@110!!!!!!!!:hail: and that was just my first time out with doug's tune in it. thanks to bamachips my 11 sec n/a auto goal is within reach...maybe this spring.:metal:
thanks doug!