Originally Posted by uke
Hey guys, I got referred to this thread from another car forum.
A few things pop into mind when looking at this:
1. What kind of gas are you using? I didn't see it brought up, but you ARE using premium fuel in this car, right? Anything less than premium *will* have a significant impact on performance.
If you are using premium, what BRAND of gas are you using? Have you tried switching to different brands in diagnosing the issue? I know that many LS2's have been finicky in what gas they're using, especially in fuels with the 10% ethanol blend in it. It's been known to cause some knock retard (KR), which can affect performance (more on that later). Have you tried switching brands? I know around me, Shell and QT have 10% ethanol blend gas, so I've shyed away from them.
2. Your wider, heaver wheels are affecting performance more than you think. I don't care what your friend in the 350Z "felt", but the laws of physics do not lie.
Here's an experiment you can try. Stand in the middle of a room, with your arms tucked into your body, and spin around as fast as you can.
- Now do the same thing with your arms outstretched.
- Now do it again with 5 lb dumbells in each hand.
What happened? It got harder to spin around each time, right? The EXACT same principle applies to your car's wheels. When you make the wheel wider and heavier, the engine has to work that much harder to get that wheel spinning. And I guarantee that the difference is probably a good bit more than you think.
Larger, heavier wheels will ALWAYS negatively affect performance. It is not possible to circumvent this principle. You can't have your "bling" and your "zing" as well.
3. Is there anyone in your area who can hook up a Predator or other car scanning tool up to your car and see what the engine is doing. Chances are, you are getting knock retard (KR) from something, which means less power.
For those not in the know, Knock Retard is where your car's onboard computer detects conditions that are favorable to knock (i.e. pre-detonation), and pulls timing from the engine in order to prevent knock from occurring.
Note: you cannot HEAR knock retard, so "I can't hear my engine pinging, so it must be fine" is not a valid argument. Only way to see if you have KR is to hook up an onboard scanner and do some WOT pulls.
Anyway, when the car's computer pulls timing in the form of KR, that loss of timing = a loss of power.
Several things can cause KR in a stock car, the biggest culprit being bad gas (from point 1). Also, hot weather can cause more KR than cold weather. What were the outside conditions when you performed these tests?
4. Has anyone yet hooked up an HP Tuners suite to these cars to see how restrictive the Torque Management is on these vehicles? Not much I can say on that unless someone's actually done the work to see if TM is holding the auto's back. If TM is an issue, a simple retune could fix that.
Anyway, hope this helps in figuring out what the issue may be.
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