L99 / LS3 Fuse Mod. Why Not Try it?

[PQ]

Originally Posted by camarossrs2150

all i know is my car relearned how to beat a 645 bmw conv after pulling fuses .that works for me .

Originally Posted by GTAHVIT

GM is taking action... This stuff doesn't happen over night. As of now GM has only had 3 TAC cases on this issue.

Part of the blame for ignorace of this problem falls on us for not followng the directions Scott gave us to open TAC cases....

The good news is thanks to the members here GM is now fully aware of the problem and working to get it right...

Scott, rpepka, and me. Surely it's been more than that.

There are hundreds if not thousands of people out there that have a problem and don't even know it. We've shown PROOF that Scotts and MY car were running slow. What are the chances that we were 'in the miniscule few' and everyone else had no problem. There have obviously been a bunch of claims on here that they too were slow and we have NO reason to doubt them.

But for the sake of argument, Me and Scott are the only ones to my knowlege that have proven it. So if two guys from lower Alabama who both ordered early and both are on the same site both have had the issue. Then there are one hell of a lot more than that.

Only 3 TAC cases on this? No wonder GM is slow on this problem. You'd think that more people would have mentioned it. Shows ME that most people won't recognise it. Those cars will 'feel' strong but won't be fast.

[SGOS252382]

Originally Posted by irpq11

Scott, rpepka, and me. Surely it's been more than that.

There are hundreds if not thousands of people out there that have a problem and don't even know it. We've shown PROOF that Scotts and MY car were running slow. What are the chances that we were 'in the miniscule few' and everyone else had no problem. There have obviously been a bunch of claims on here that they too were slow and we have NO reason to doubt them.

But for the sake of argument, Me and Scott are the only ones to my knowlege that have proven it. So if two guys from lower Alabama who both ordered early and both are on the same site both have had the issue. Then there are one hell of a lot more than that.

Only 3 TAC cases on this? No wonder GM is slow on this problem. You'd think that more people would have mentioned it. Shows ME that most people won't recognise it. Those cars will 'feel' strong but won't be fast.

I'm glad you have found some performance. I for one am suprised. I've known about the fuse pull "trick" for years with other cars. Guys would do it at the track (stock cars) for a little extra HP. But with these cars, the results didn't last very long (sometimes only a few miles).
But these car weren't stuck in a "slow" mode. They were just normal cars looking for a little exta HP.

What's weird is, I can't believe the "low octane tune" on the L99 is that bad. I guess the fuse pull mode gives the computer a chance to start over with the "high octane tune," which appears to be light years better than the "low octane tune."

GM has probably fixed this without telling anyone. They've probably re-written the low octane tune to prevent this problem?

[BigMatt]

What's a break in period

[SoloSK71]

Originally Posted by SSOOCH

If you use 91 octane (it's the highest available in my area) will the computer use the high octane tables? Anybody?

Originally Posted by brandotron

I'd also like to hear someone's take on this. 91 is the highest available (other than 100+ race fuel) here in California.

The car uses the tables based not truly on octane rating but on how the car behaves while being driven. So you could have a situation where it would use the higher table while running 87 or 89 if conditions were right.

Having said that, when tuning the cobalt 87 would always default to the lower table while 91 and up always used the higher table.

89 could go either way depending on conditions.

- SK

[Warr3nc]

This came from the GM SI service manual:

Knock Sensor

The knock sensor system enables the engine control module (ECM) to control the ignition timing for the best possible performance while protecting the engine from potentially damaging levels of detonation, also known as spark knock. The knock sensor system uses one or two flat response 2-wire sensors. The sensor uses piezo-electric crystal technology that produces an AC voltage signal of varying amplitude and frequency based on the engine vibration or noise level. The amplitude and frequency are dependant upon the level of knock that the knock sensor detects. The ECM receives the knock sensor signal through two isolated signal circuits for each knock sensor.

The control module learns a minimum noise level, or background noise, at idle from the knock sensor and uses calibrated values for the rest of the RPM range. The control module uses the minimum noise level to calculate a noise channel. A normal knock sensor signal will ride within the noise channel. As engine speed and load change, the noise channel upper and lower parameters will change to accommodate the normal knock sensor signal, keeping the signal within the channel. In order to determine which cylinders are knocking, the control module only uses knock sensor signal information when each cylinder is near top dead center (TDC) of the firing stroke. If knock is present, the signal will range outside of the noise channel.

If the control module has determined that knock is present, it will retard the ignition timing to attempt to eliminate the knock. The control module will always try to work back to a zero compensation level, or no spark retard. An abnormal knock sensor signal will stay outside of the noise channel or will not be present. knock sensor diagnostics are calibrated to detect faults with the knock sensor circuitry inside the control module, the knock sensor wiring, or the knock sensor voltage output. Some diagnostics are also calibrated to detect constant noise from an outside influence such as a loose/damaged component or excessive engine mechanical noise.

The system is supposed to retard and advance the timing on a continual basis as needed. IMO the problem is just a programming issue, which is normal for brand new vehicles. I saw on another thread that there could be up to 16 degrees timing loss between the low octane and high octane tables. Definitely noticeable.