Tay-Z

I have an 06 Enthusiast and thinking I was putting the best gasoline in it, I have been using Amoco Ultimate 93 octane sold at BP. When I put a load on the engine, it sounds like its knocking. It dosent sound like that under normal acceleration but when you push it, I hear what sounds like detonation. Anyone else experience this with premium gas?

LeMans 05

iTrader: (1)

I have no answer as to 'why' it's knocking, but I always use Mobil 1 93 octane, and don't have this problem

bailey bill

You should never hear audible knocking on the Z, or almost any modern EFI-equipped car.

The Z has knock detector, and and a correction loop that retards timing that should correct any knock before it is ever audible.

bill

PL510_Z33

In the real world detonation can rear its ugly head before some knock sensors have a chance to retard timing. I HAVE heard it on modern cars with EFI, new and older on hot days under load off idle... thought I MAY have heard it on my Z once...but it might have been the popcorn my old lady was chew'n!

j!

bailey bill

Well, I can't speak for all cars, but...Just FYI-

My '91MR2 turbo had a knock sensor/response loop (forced induction cars are very susceptible to detonation). I could often feel the ECU adjusting timing, but never heard knock. And that was early '90s technology.

Modern engine management systems should definitely be capable of correcting knock long before it reaches the audible stage.

bill

abyss

Should, and are is a very fine thread. Problems arise everywhere with 'technology'

Tay-Z

Thanks for the good info Bill.
I'm going to try a different brand of premium gas next fill-up anyway, just in case.

bailey bill

Just FYI, from a Toyota tech training manual:

"When the ECU judges that detonation is taking place, it retards ignition timing until the knocking stops. Timing is then advanced back to calculated value or, ir detonation begijns, retarded again until detonation is stopped. In this manner. the ignition system can be operated at maximum efficiency, on the borderline of detonation, while avoiding the audible "ping. "

More detailed info can be found at:

www.autoshop101.com/

See Articles 24 and 25

bill

PL510_Z33

Hmmm shrug of the shoulders then...what do you think I AM hearing Bill?
j!

bailey bill

Well, I 've only had my Z about 2 1/2 weeks. There are still a lot of things I haven't learned yet, so I really don't have any good guesses. I haven't drivne in the mountains on a hot July day, yet, but I really would NOT expect to get knock from this engine. As I said, the system on my '91 MR2 turbo performed flawlessly.



You don't think think my '91 Toyota worked better than my new Z do you??

bill

PL510_Z33

No, I suppose not...Or HOPE not! But I still swear I heard it on properly running new cars for a second on hot days...
Agree to disagree
j!

newzee

I've had the same problem. It's annoying as hell. I finally had the dealership advance the timing 2 degrees, which is apparently the biggest adjustment that the ecu will hold. That seemed to work for the most part. At least it reduced its severity, but I still hear it a little. It never does it when the engine is cold. It's only later in the day that it appears. Now I noticed its burning oil like mad. WTF! I don't think there could be a correlation though. Ok, now I'm gonna go and sulk for a bit. Good luck

Black_Sunshine

This topic has been discussed ad nauseum. My '06 knocks on 91. I'm surprised you have this problem with 93 though. I mixed 75/25 91 and 100 (for a roughly 93 octane mix) and that took care of it, albeit temporarily.

Montez

My 350 did it and our 03 Max and 05 G35 do it from time to time when its hot and we use 93 octane as well. I notice it when driving through the alley as I pass by fences, its something with the 3.5........

sofa king

iTrader: (25)

have you already surpassed the break-in period in 2 1/2 weeks?

bailey bill

What does this discussion have to do with the break-in period? As my comment about mountain driving suggest, knock is most likely to occur under high load/low RPM conditions.



bill

Tay-Z

I'm going to fill-up with Chevron next tank. Since it was blended with 10% ethanol, the octane went from 92 to 93.