knocking sound when using low octain fuel
Registered User
Joined: Oct 2010
Posts: 157
From: Richmond,VA (USA)
Rep Power: 22
...and if you engine cylinders have nikasl plating (I think the 928 did), using less than 92 Octane will trash your motor. It'll washout the linings and thus, no compression.
Mostly used in racing engines; however, 80s and 90s Jaguar owners found this out the hard way.
USE 92+
Mostly used in racing engines; however, 80s and 90s Jaguar owners found this out the hard way.
USE 92+
This is a topic of much debate, research, and opinion. If you really want to learn more, search for pre-ignition, and detonation. Entire books have been written about the subject!
In a nutshell, the metalic clacks you hear are the more harmless variety of "improper" ignition (providing you have a computer that back back off timing each second as required). This is detonation and the sound is caused by multiple flame fronts. The flame fronts take place at "roughly" the correct time and sorta compliment each other.
Those typically not heard are detonation events and if bad enough or often enough, bend connecting rods, spins bearings, breaks rings, melts holes in pistons, etc. This is pre-ignition and the pre-ignition front is far earlier than is needed and this flame front forces the piston downward before it is ready. Think of a hammer hitting the piston when it is still on its way up in the compression stroke. Bad Bad Bad.
Maximum heat/pressure occurs at peak torque. Theoretically, after around 3800 rpm, the pistons are moving so fast and spark events taking place so quickly, that detonation pre-ignition is no longer a big concern.
Enjoy!
In a nutshell, the metalic clacks you hear are the more harmless variety of "improper" ignition (providing you have a computer that back back off timing each second as required). This is detonation and the sound is caused by multiple flame fronts. The flame fronts take place at "roughly" the correct time and sorta compliment each other.
Those typically not heard are detonation events and if bad enough or often enough, bend connecting rods, spins bearings, breaks rings, melts holes in pistons, etc. This is pre-ignition and the pre-ignition front is far earlier than is needed and this flame front forces the piston downward before it is ready. Think of a hammer hitting the piston when it is still on its way up in the compression stroke. Bad Bad Bad.
Maximum heat/pressure occurs at peak torque. Theoretically, after around 3800 rpm, the pistons are moving so fast and spark events taking place so quickly, that detonation pre-ignition is no longer a big concern.
Enjoy!
Registered User
Joined: Feb 2010
Posts: 707
From: Alaska
Rep Power: 51
I can only get 90 octane premium up here even though we make the stuff! During my drive up the Alcan many of the gas stations only had 87 octane. Mine has never pinged but I have seen variance in my gas mileage.
I would hesitiate to put in any additives due to placing the MAF sensors at risk. At $800 each, I'd not risk the pair.
I would hesitiate to put in any additives due to placing the MAF sensors at risk. At $800 each, I'd not risk the pair.
Registered User
Joined: Mar 2010
Posts: 505
From: SoCo.....in austin texas
Rep Power: 38
2006 and above models should have the Anti Knock sensor............so you may have an older model. Hence it will Knock if you dont put in the proper Octane.
Besides, these cars run like poo without high octane.........cost of doing bidness........
off topic, I dont want to see another propspective TT owner asking about fuel costs.......go big or go the F home.
Besides, these cars run like poo without high octane.........cost of doing bidness........
off topic, I dont want to see another propspective TT owner asking about fuel costs.......go big or go the F home.
Last edited by cordsig79; Oct 13, 2010 at 11:14 AM.
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