Re: Octane/knocking information
Thread Starter
Joined: Sep 2000
Posts: 4,728
From: City of the Fallen Angel, CA
Posted by ScreamingVQ from:
http://forums.maxima.org/showthread.php?threadid=31152
Fuel recommendation is Unleaded premium gasoline with an octane rating of at least 91 AKI (Anti-Knock Index) number. If unleaded premium gasloine is not available, unleaded regular gasoline with an octane rating of at least 87 AKI can be used. However, for maximum vehicle performance, the use of unleaded premium gasoline is recommended. In most parts of North America, you should use unleaded gasoline with an octane rating ot at least 87 or 91 AKI number. However, you may use unleaded gasoline with an octane rating as low as 85 AKI number in these high altitude areas [over 4,000ft] such as Colorado, Montana, New Mexico, Utah, Wyoming, northeastern Nevada, southern Idaho, western South Dakota, western Nabraska, and that part of Texas which is directly south of New Mexico. Using unleaded gasoline with an octane rating lower than stated above can cause persistent, heavy spark knock. (Spark knock is a metallic rapping noise.) If servere, this can lead to engine damage. If you detect a persistent heavy spark knock even when using gasoline of the stated octane rating, or if you hear steady spark knock while holding a steady speed on level roads, have your dealer correct the condition. Failure to correct the condition is misuse of the vehicle, for which NISSAN is not responsible. Your vehicle is equiped with knock sensors. Some people have the wrong meaning of what this is. Knock sensors are NOT designed to compensate for low octane unleaded gasoline. They are designed for different brand of gas of the same AKI number, different road conditions, weather, car/engine load. Knock sensors hear pinging in the cylinder, after the pinging has taken place (which will damage your engine), and retards ignition timing. Incorrect ignition timing will result in knocking, after-run or overheating. This in turn may cause excessive fuel consumption or damage to the engine. However, now and then you may notice light spark knock for a short time while accelerating or driving up hills. This is no cause for concern, because you get the greatest fuel benefit when there is light spark knock for a short time under heavy engine load.
Nissan recommends a premium unleaded gasoline (91+ AKI number). It even says so on the gas cap. No one knows your car better than Nissan. You can use 87, but if your engine starts to have servere spark knock and/or showing signs of damage, its not Nissans fault and is not covered under warranty.
http://forums.maxima.org/showthread.php?threadid=31152
Fuel recommendation is Unleaded premium gasoline with an octane rating of at least 91 AKI (Anti-Knock Index) number. If unleaded premium gasloine is not available, unleaded regular gasoline with an octane rating of at least 87 AKI can be used. However, for maximum vehicle performance, the use of unleaded premium gasoline is recommended. In most parts of North America, you should use unleaded gasoline with an octane rating ot at least 87 or 91 AKI number. However, you may use unleaded gasoline with an octane rating as low as 85 AKI number in these high altitude areas [over 4,000ft] such as Colorado, Montana, New Mexico, Utah, Wyoming, northeastern Nevada, southern Idaho, western South Dakota, western Nabraska, and that part of Texas which is directly south of New Mexico. Using unleaded gasoline with an octane rating lower than stated above can cause persistent, heavy spark knock. (Spark knock is a metallic rapping noise.) If servere, this can lead to engine damage. If you detect a persistent heavy spark knock even when using gasoline of the stated octane rating, or if you hear steady spark knock while holding a steady speed on level roads, have your dealer correct the condition. Failure to correct the condition is misuse of the vehicle, for which NISSAN is not responsible. Your vehicle is equiped with knock sensors. Some people have the wrong meaning of what this is. Knock sensors are NOT designed to compensate for low octane unleaded gasoline. They are designed for different brand of gas of the same AKI number, different road conditions, weather, car/engine load. Knock sensors hear pinging in the cylinder, after the pinging has taken place (which will damage your engine), and retards ignition timing. Incorrect ignition timing will result in knocking, after-run or overheating. This in turn may cause excessive fuel consumption or damage to the engine. However, now and then you may notice light spark knock for a short time while accelerating or driving up hills. This is no cause for concern, because you get the greatest fuel benefit when there is light spark knock for a short time under heavy engine load.
Nissan recommends a premium unleaded gasoline (91+ AKI number). It even says so on the gas cap. No one knows your car better than Nissan. You can use 87, but if your engine starts to have servere spark knock and/or showing signs of damage, its not Nissans fault and is not covered under warranty.
I have an intermittent detonation problem. It seems to occur whenever it damn well wants to. I sent the following e-mail to Phuong, but perhaps you'd be willing to comment as well. Thanks.
"Hi Phuong --
Well my detonation problem between 2,000 and 3,000 rpm is still alive and well. Damn thing is, it happens intermittently. And it doesn't matter whether I'm easy on the engine or hard on the engine. Whatever's causing the detonation seems to have a mind of its own.
I'm not sure what's going on, but I've got some info that may provide a clue. To get rid of the detonation, all I have to do is pour a bottle of Chevron Techron Concentrate in my gas tank. That stuff works every time. My guess is that the Techron is acting as an octane booster and overcoming the problem. And I can buy Chevron Pro-Gard Fuel Injector Cleaner (basically, Techron with a mild injector detergent) at Costco for $2.50 a bottle and use it every 1,000 miles. But I'd rather not rely on a fuel treatment as a long term solution.
The only engine mods I have are the OSCAI conversion, a Random Technology Hi-Flow Cat, a 2.5" mandrel-bent catback system, and a Magnaflow muffler. Lots of the guys at Maxima.org have many more mods than this (PRCAI, Y-pipe, S/C) and never encounter detonation. I'm guessing . . . and mind you, this is just a guess . . . that my engine is running lean from time to time. If I'm correct, I wonder if I could overcome the problem by installing a fuel pressure riser or something like a Super AFC that allows me to adjust the A/F ratio. I realize I'd have to get my car dyno'd to get the settings right. But I'm hell-bent to get rid of this detonation.
Any suggestions?"
Originally posted by y2kse
OK, ScreamingVQ. You've definitely got my attention. I created a new post because I felt your reply was worthy of its own thread. So here's my issue.
I have an intermittent detonation problem. It seems to occur whenever it damn well wants to. I sent the following e-mail to Phuong, but perhaps you'd be willing to comment as well. Thanks.
"Hi Phuong --
Well my detonation problem between 2,000 and 3,000 rpm is still alive and well. Damn thing is, it happens intermittently. And it doesn't matter whether I'm easy on the engine or hard on the engine. Whatever's causing the detonation seems to have a mind of its own.
I'm not sure what's going on, but I've got some info that may provide a clue. To get rid of the detonation, all I have to do is pour a bottle of Chevron Techron Concentrate in my gas tank. That stuff works every time. My guess is that the Techron is acting as an octane booster and overcoming the problem. And I can buy Chevron Pro-Gard Fuel Injector Cleaner (basically, Techron with a mild injector detergent) at Costco for $2.50 a bottle and use it every 1,000 miles. But I'd rather not rely on a fuel treatment as a long term solution.
The only engine mods I have are the OSCAI conversion, a Random Technology Hi-Flow Cat, a 2.5" mandrel-bent catback system, and a Magnaflow muffler. Lots of the guys at Maxima.org have many more mods than this (PRCAI, Y-pipe, S/C) and never encounter detonation. I'm guessing . . . and mind you, this is just a guess . . . that my engine is running lean from time to time. If I'm correct, I wonder if I could overcome the problem by installing a fuel pressure riser or something like a Super AFC that allows me to adjust the A/F ratio. I realize I'd have to get my car dyno'd to get the settings right. But I'm hell-bent to get rid of this detonation.
Any suggestions?"
OK, ScreamingVQ. You've definitely got my attention. I created a new post because I felt your reply was worthy of its own thread. So here's my issue.
I have an intermittent detonation problem. It seems to occur whenever it damn well wants to. I sent the following e-mail to Phuong, but perhaps you'd be willing to comment as well. Thanks.
"Hi Phuong --
Well my detonation problem between 2,000 and 3,000 rpm is still alive and well. Damn thing is, it happens intermittently. And it doesn't matter whether I'm easy on the engine or hard on the engine. Whatever's causing the detonation seems to have a mind of its own.
I'm not sure what's going on, but I've got some info that may provide a clue. To get rid of the detonation, all I have to do is pour a bottle of Chevron Techron Concentrate in my gas tank. That stuff works every time. My guess is that the Techron is acting as an octane booster and overcoming the problem. And I can buy Chevron Pro-Gard Fuel Injector Cleaner (basically, Techron with a mild injector detergent) at Costco for $2.50 a bottle and use it every 1,000 miles. But I'd rather not rely on a fuel treatment as a long term solution.
The only engine mods I have are the OSCAI conversion, a Random Technology Hi-Flow Cat, a 2.5" mandrel-bent catback system, and a Magnaflow muffler. Lots of the guys at Maxima.org have many more mods than this (PRCAI, Y-pipe, S/C) and never encounter detonation. I'm guessing . . . and mind you, this is just a guess . . . that my engine is running lean from time to time. If I'm correct, I wonder if I could overcome the problem by installing a fuel pressure riser or something like a Super AFC that allows me to adjust the A/F ratio. I realize I'd have to get my car dyno'd to get the settings right. But I'm hell-bent to get rid of this detonation.
Any suggestions?"
Originally posted by yo_its_ok
I wonder if I could overcome the problem by installing a fuel pressure riser or something like a Super AFC that allows me to adjust the A/F ratio.
FPR or S AFC won't do you much good. The Maxima engine works great w/o the FPR or S AFC cause its not a speed density system, like a Honda. A MAF can compensate for more airflow. The MAF is a nicrome wire that is heated and depending on how much air is flowing past it it creates a signal to get the right amount of fuel for the incoming air. I tried the FPR with no gain, S AFC, after installing in a MX6, didn't do much til he was boosting and juicing.
As for the symptoms mentioned about detonation problem, its very strange. Is your "SERVICE ENGINE SOON" light on ?
If the car is detonating, the knock sensor is supposed to retard timing before you even feel or hear it. Another problem that could be looked into is your ignition system. Check each individual coil, and inspect the wires leading to the coils. There could be a problem with one of your injectors as the voltage may be dropping in one of your 6 injectors that it doesn't supply the needed fuel to one cylinder. I'm not too sure if an oxygen sensor would cause a condition like this, but have the car brought to Nissan and check the signals coming from all sensors and if the symptoms can be mimic'd while stationary it would help out Nissan Techs alot to diagnose the problem.
-Good Luck
I wonder if I could overcome the problem by installing a fuel pressure riser or something like a Super AFC that allows me to adjust the A/F ratio.
FPR or S AFC won't do you much good. The Maxima engine works great w/o the FPR or S AFC cause its not a speed density system, like a Honda. A MAF can compensate for more airflow. The MAF is a nicrome wire that is heated and depending on how much air is flowing past it it creates a signal to get the right amount of fuel for the incoming air. I tried the FPR with no gain, S AFC, after installing in a MX6, didn't do much til he was boosting and juicing.
As for the symptoms mentioned about detonation problem, its very strange. Is your "SERVICE ENGINE SOON" light on ?
If the car is detonating, the knock sensor is supposed to retard timing before you even feel or hear it. Another problem that could be looked into is your ignition system. Check each individual coil, and inspect the wires leading to the coils. There could be a problem with one of your injectors as the voltage may be dropping in one of your 6 injectors that it doesn't supply the needed fuel to one cylinder. I'm not too sure if an oxygen sensor would cause a condition like this, but have the car brought to Nissan and check the signals coming from all sensors and if the symptoms can be mimic'd while stationary it would help out Nissan Techs alot to diagnose the problem.
-Good Luck
Thread Starter
Joined: Sep 2000
Posts: 4,728
From: City of the Fallen Angel, CA
Thanks guys. I'll also post Phuong's response for reference.
"By using an external product, you're just hiding the root of the problem. Since it's intermittent, it'd be tough for a Nissan Consult test to show anything unless it detonates while being tested. My guess is something in the electronics, like your detonation sensor, throttle position sensor, or mass air flow sensor. If you haven't run an ECU diagnostic yet, do so. It may have an error code stored.
The mods you have on should not affect anything. The mass air flow sensor should be able to read & adjust for any airflow changes and dump in more fuel accordingly."
"By using an external product, you're just hiding the root of the problem. Since it's intermittent, it'd be tough for a Nissan Consult test to show anything unless it detonates while being tested. My guess is something in the electronics, like your detonation sensor, throttle position sensor, or mass air flow sensor. If you haven't run an ECU diagnostic yet, do so. It may have an error code stored.
The mods you have on should not affect anything. The mass air flow sensor should be able to read & adjust for any airflow changes and dump in more fuel accordingly."
Thread Starter
Joined: Sep 2000
Posts: 4,728
From: City of the Fallen Angel, CA
Originally posted by yo_its_ok
Didn't I say that ?
Didn't I say that ?
Thread Starter
Joined: Sep 2000
Posts: 4,728
From: City of the Fallen Angel, CA
Originally posted by Y2KevSE
I thought the ECU keeps a pending code even though the light hasn't gone off yet.
I thought the ECU keeps a pending code even though the light hasn't gone off yet.
Originally posted by y2kse
Are you sure, Kev? I don't want to waste $40.00 on a diagnostic if there's no chance that something may show up. BTW, it happened again today. The engine started missing as I was going up a hill. I stopped and gunned it in neutral a couple of times. Then I put it in gear, started giving it some throttle again, and it began to detonate. So I backed off for a couple of minutes and then gave it some throttle again. The detonation went away. Can you believe it?
Are you sure, Kev? I don't want to waste $40.00 on a diagnostic if there's no chance that something may show up. BTW, it happened again today. The engine started missing as I was going up a hill. I stopped and gunned it in neutral a couple of times. Then I put it in gear, started giving it some throttle again, and it began to detonate. So I backed off for a couple of minutes and then gave it some throttle again. The detonation went away. Can you believe it?
My suggestion, bring the car to the dealer.
Thread Starter
Joined: Sep 2000
Posts: 4,728
From: City of the Fallen Angel, CA
Originally posted by yo_its_ok
STOP DRIVING YOUR CAR IF ITS DETONATING, Check your spark plugs I'm pretty sure their shot by now. Go to Nissan it might be a coil but stop driving your car.
STOP DRIVING YOUR CAR IF ITS DETONATING, Check your spark plugs I'm pretty sure their shot by now. Go to Nissan it might be a coil but stop driving your car.
I'm going to take your advice and have my dealer pull the plugs. One way or the other I intend to get to the bottom of this.
BTW, I spoke to Dave Burnette at Southpoint Nissan about my condition. He said he checked with his techs and they told him that they have to replace ignition coils on 5th Gen Maximas all the time. What's more, he said that there's been such a run on coils that they're currently on backorder. What does that tell you?
Originally posted by y2kse
The problem is, it doesn't detonate all the time. Most of the time my engine runs just fine. But I assume that since it actually has detonated, and detonated more than once, there should be some sort of telltale signs on one or more of the plugs.
I'm going to take your advice and have my dealer pull the plugs. One way or the other I intend to get to the bottom of this.
BTW, I spoke to Dave Burnette at Southpoint Nissan about my condition. He said he checked with his techs and they told him that they have to replace ignition coils on 5th Gen Maximas all the time. What's more, he said that there's been such a run on coils that they're currently on backorder. What does that tell you?
The problem is, it doesn't detonate all the time. Most of the time my engine runs just fine. But I assume that since it actually has detonated, and detonated more than once, there should be some sort of telltale signs on one or more of the plugs.
I'm going to take your advice and have my dealer pull the plugs. One way or the other I intend to get to the bottom of this.
BTW, I spoke to Dave Burnette at Southpoint Nissan about my condition. He said he checked with his techs and they told him that they have to replace ignition coils on 5th Gen Maximas all the time. What's more, he said that there's been such a run on coils that they're currently on backorder. What does that tell you?
I hope you get this fixed.
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