BillyBobJoe

a little while back i got my XCal2 in and installed the 93 octane tune. It was needless to say, friggin awesome as I did a one wheel peel leaving the driveway. Anyway, i shortly noticed a rather annoying rattle occuring between 1400RPM and 2200RPM under nay type of load, whether its cruising or WOT. First thought was a losse bolt in the tranny pan from when I installed the shift kit, but it sounds fine without using the tune. Next thought, maybe the exhaust flange. Jack up the car, try to torque up the bolts a little, but they are tight as hell. So right now, I'm back to my stock tune so i dont have to deal with the rattle. I've been emailing Brent over at brenspeed and he's trying to help me figure out the problem. I'm thinking maybe the gas I'm using isnt up at 93 octane and is causing the rattle. I'll refill at a different gas station this time and see what happens. For now, I've got half a tank of 87 octane for my stock tune to use first. You guys have any ideas or heard of anything similar to this?

raz54

Man if that is detonation you are hearing you are on the verge of blowing it up. One way to tell is put in 4th gear as soon as you can then punch it (if it's a stick). If it's detonation it will rattle till you let off the gas.

l_shizzle_l

i wouldn't base that fact only on that procedure

raz54

If he does that with the tune and it rattles then if he does it without the tune and there is no rattles there is nothing else it could be. I did forget to mention he should be going about 30 mph when he trys it and put in either high octain gas or octain booster first.

eddiev22

no,i have a stock3.8 5 speed+cai, same RPM ranges i get a rattling sound.. not sure what it is either, but it doesn't occur consistently, not sure what the variable is. Maybe rain?

raz54

If it was detonation it will normally only do it in a hard pull. That's why I said put in 4th at a low speed and punch it cause it will rattle then if it's detonation. Since your rattle is not constant I don't think that's your problem.

BillyBobJoe

i've got an auto, as the sig states,. but basically, its just right at that RPM range and its not even under heavy load. Brent told me to try and back the timing off next time i fill up. Since for now I'm back to the stock tune and 87 octane. But in a couple days I'll try it again. I prolly will pull out the plugs, if they're burned to hell, then that would help tell a story.

raz54

It's going to be hard to read the plugs now and get an accurate reading of how it was then. You could put in a new set though when you try it again, then if it rattles you can see if it's too lean or too hot.

TruXter

chevron has the highest octane in texas.

cominus

Which is? The gas station by my house has 93 octane and it's "valero" previously....maverick, texico, circle k........