I swapped from a 3.4 to a 3.2" pulley and put in my new mail order tune. The truck seems to fall flat on its face from 2000 to 3000rpm and then recovers after that. I have a Flex Fuel 5.3 Tahoe. This truck comes with 38#? injectors and a different fuel pump than a normal 5.3. I did not replace injectors or install an additional fuel pump when the radix was installed because it wasn't required. I am wondering if the new pulley is causeing me issues with either running out of injector or the fuel pump can't keep up and has to recover for a second in the 2 to 3K rpm range? The truck feels as if it looses power or bogs down and then jumps back to life. No logging software to check.

 

you changed the boost level when you changed the pulley....now you need a new tune for that xtra boost...you should still be ok with the 38# injectors for right now

 

Bottom line.....YOu can not tune for boost via the mail....Take it to a dyno shop.

 

The dyno/street tune is in the near future. I'm just concerned I could be running dangerously lean and don't know it. If its a tune issue I can handle that but if it's a fuel flow problem then I need to order some parts and get to work. The tune I have is set up for the extra boost. I was asked if I was running a nearly empty tank after installing the new tune. Not sure what that has to do with it Does anyone know if the stock pump and injectors can handle a 3.2 pulley (9#'s) on a flex fuel setup? Does Allen Nelson ever vacation in Pensacola?

 

I believe that if you are running on a low octane timing table, the PCM attempts to reset after a refueling. So, for example, if you encountered some knock (because of some bad gas, or if the old lady puts in 87 instead of 91 or 94 ), your tune would revert to the low octane table, which is set up to pull timing. Once you refill, the PCM attempts to restore to the higher table with more timing. Perhaps this is why you were asked this question.

I'm with Brian on this, I don't think I would get a mail-order tune for anything other than a stock vehicle, or something lightly modded. There are too many variables in the equation to contend with when you're boosted. One mistake, miscalculation, or overly-aggressive number and you're toast. If I were you I would put the stock pulley back on, revert to the old tune, and drive to a trusted shop for a real tune. Even if it's 7-10 hours away, it's worth it to have a truck that's just blown, and not blown-up.

 

This is very true. I had the octane table spread to accomodate 87-93 because of gas prices. I was running on a straight 93 tune prior. This was a actual PCM swap not just an update to the previoous tune through a laptop. It may have been setup to start at the low octane table. I was on fumes so I put half a tank of 93 in it yesterday (we are limited on how much gas we can buy at once) so maybe after a day or so the PCM will pick up on this and adjust. The dyno tune guy is about 2 hours away, getting an appointment and getting off work is the issue more than the drive or the $$.