replica

I changed over to the 93 octane Brenspeed tune a few days ago after filling up with some 93 octane gas. I've noticed under load around 4,500 RPM and up I'll get a quick rattle/tapping sound that seems related to the RPMs. It doesn't quite sound like an exhaust rattle. Can I pull data from the SCT tuner that will show me if the motor is knocking?

Another question. With Brenspeed tunes, do they just load on an "off the shelf" tune they're already written for cars with the same mods? My tune is for a bone stock GT, which matches my car currently. Also, are Brenspeed tunes known to run lean or require adjustment on some applications? What's the air/fuel ratio for a typical brenspeed tune? Is there a little fuel left over for changes in temperature and so on? How conservative is Brenspeed with their tunes?

timmbo

I had the same problem on a 93 from them as well when I first went from stock tune/intake to a CAI. The next tune I had them do was after my cams and had them write it for 91 octane. No pinging now. May be the gas in your area. Try a tank of Shell and see if that helps. I think I would ask for a 91 tune anyway just because of the fluctuations of 93 quality gasolines.

replica

I guess I'll step down to the 91 tune. Bummer.

ski

Also, if you had been using a lower octane gas prior to filling up with 93 octane and installing the 93 tune, then some of the lower octane stuff may have been in the tank. Drop the timing until the pinging disappears, use up the current tankful, and refill with 93.
If no luck, then try different brands of 93.
If that doesn't work, then there may be some carbon build up in the cylinders. See if dumping a can of Seafoam in the tank helps.

replica

I'd like to know how lean Brenspeed's tunes are first before I do all that.

Nuke

Definately run the tank down and then fill-up with a different brand fuel from a different station first. It's not unusual for some fuel to be a tad shy. After that, Brenspeed will adjust the tune if the pinging doesn't get resolved.

replica

I'll give it another tank. I gave it some beatings at lunch and there's a fizzing rattle for just a second during WOT. My wife said it sounded like it was under the car, not from the engine bay.

Is there any easy way for me to just data log it and see the knock on a graph or whatever the visual output is for the SCT tuner? Like on a Honda, with Hondata the check engine light will blink when the knock sensor goes off.

americaniron

When I first got my Brenspeed 93 tune, I had the same problem. I switched to using a different gas station, and the problem disappeared. I honestly believe that the station I used to go to sold a lower octane as 93. I haven't had the problem since.

ShaneM

I had the same exact issue with the 93 tune, i contacted Brenspeed about it and they basically said they use the same tune for everyone with the same mods and pointed the finger at the fuel. They told me their tunes are very octane specific. i don't even bother with the 93 tune, if one bad tank is going to cause issues it seems to be too highly tuned to me, but what do i know.

ski

Nah!
You first eliminate of all of the problem's common causes first, which in your situation include leftover low octane gas in your car's tank, a bad load of 93 octane gas, carbon build up, and a loose CAI connection(Forgot about that one). If none of those are the cause, then you look at the tune.
If you blame the tune as the possible culprit right off the bat, then you may wind up with an adjusted tune that will needlessly lower your engine's power output.