this is what its like using 87 octane
11-03-2002, 07:10 PM
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Thanks Michael...
...for a prompt, knowledgeable, and well-written reply.
I think the first few times at the track I'll stick with 91, and after I've gotten a sense for the baseline I'll try running higher octanes.
--James
Columbia, MD
Lemans Track
I think the first few times at the track I'll stick with 91, and after I've gotten a sense for the baseline I'll try running higher octanes.
--James
Columbia, MD
Lemans Track
11-03-2002, 07:53 PM
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Re: What about higher octanes
[QUOTE]Originally posted by commasense
[B]This would seem to be the place to ask the converse of the original question: what happens if I put in higher octane than 91? Do I get more horsepower, or do I just do a different kind of damage to the engine?
I'll be taking the car to the track a few times a year. Should I use the higher octane fuels available there (at only $4.00 a gallon or so!!!) for better performance? How do I determine how high to go? Is there a simple linear correlation between octane and power? Is it possible to go too high?
Are there any problems to be expected from using 91 most of the time and switching to higher octane for a day at the track every month or so?
Thanks.
--James
Columbia, MD
I have always put in the highest rated octane when I could get it. We don't have many stations in my state that carry 92 or 93, but I will gladly pay the extra for it. I drive my sports cars HARD. I always have and I don't intend to change now. I don't race, but I run to the redline often in the lower gears, 3rd especially to stay out of jail or get a $5 or 600 ticket. In my experience, there is no problem with higher octane for the street, and no problem in using it for racing; I would pay the $4 a gallon for 100 octane at the track or strip if I were racing. You don't want to buy much to minimize weight, so 1 or 2 gallons might be enough. The racers on this site would know better than I.
Going back to 91 octane isn't a problem, you will be using the recommended rating approved by the manufacturer. My 91 MR2T always liked 93 better, but ran to redline often with 91. I've never heard of running too high an octane harming an engine. If someone knows the answer, I would be interested to hear it.
Also, I have always heard stories about racers filling up their cars with Aviation fuel at 115 octane before racing but I don't know if thats bs or not. Ok, you guys who are racers help me out with this, please.?
Boomer
[B]This would seem to be the place to ask the converse of the original question: what happens if I put in higher octane than 91? Do I get more horsepower, or do I just do a different kind of damage to the engine?
I'll be taking the car to the track a few times a year. Should I use the higher octane fuels available there (at only $4.00 a gallon or so!!!) for better performance? How do I determine how high to go? Is there a simple linear correlation between octane and power? Is it possible to go too high?
Are there any problems to be expected from using 91 most of the time and switching to higher octane for a day at the track every month or so?
Thanks.
--James
Columbia, MD
I have always put in the highest rated octane when I could get it. We don't have many stations in my state that carry 92 or 93, but I will gladly pay the extra for it. I drive my sports cars HARD. I always have and I don't intend to change now. I don't race, but I run to the redline often in the lower gears, 3rd especially to stay out of jail or get a $5 or 600 ticket. In my experience, there is no problem with higher octane for the street, and no problem in using it for racing; I would pay the $4 a gallon for 100 octane at the track or strip if I were racing. You don't want to buy much to minimize weight, so 1 or 2 gallons might be enough. The racers on this site would know better than I.
Going back to 91 octane isn't a problem, you will be using the recommended rating approved by the manufacturer. My 91 MR2T always liked 93 better, but ran to redline often with 91. I've never heard of running too high an octane harming an engine. If someone knows the answer, I would be interested to hear it.
Also, I have always heard stories about racers filling up their cars with Aviation fuel at 115 octane before racing but I don't know if thats bs or not. Ok, you guys who are racers help me out with this, please.?
Boomer
11-03-2002, 08:01 PM
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octane
Originally posted by Michael-Dallas
The compression ratio, the ignition timing maps, the a/f maps, etc. are tuned for 91 octane. Yes, there is a detonation sensor (or two), but for it to work, it has to detect detonation. So you will get detonation for a (hopefully small) period of time. And when it does detect detonation, it backs down those maps, therefore, you lose hp.
Furthermore, the detonation sensor isn't completely idiot proof. On the Z32, the detonation sensor "listens" for a vibration frequency that is caused by detonation. Unfortunately, the detonation sensor is only good to 3000rpms so after 3000rpms, the detonation sensor does not work. And even still, detonation can produce a slightly different vibration frequency and the detonation sensor may not detect it.
If you want my advice: if you intend on running 87 octane, then I'd drive like grandma and try to stay at low rpms. The more aggressive you drive on 87 octane, the more aggressive maps the ECU will use.
You say you'd save $20/mo or $240/yr switching to 87 octane. A new short block should be around $3k and a new long block should be around $7k and that excludes labor and other parts. Do the math. How many years will you be rolling die?
Here's an excellent article on detonation (uncontrolled combustion after the spark) and pre-ignition (uncontrolled combustion before the spark AKA dieseling) that includes ignition timing and octane: http://www.streetrodstuff.com/Articl...e_Basics_I.php
Here's the gasoline FAQ that explains what octane is: http://www.seansa4page.com/resource/octane.html
QED.
Michael.
The compression ratio, the ignition timing maps, the a/f maps, etc. are tuned for 91 octane. Yes, there is a detonation sensor (or two), but for it to work, it has to detect detonation. So you will get detonation for a (hopefully small) period of time. And when it does detect detonation, it backs down those maps, therefore, you lose hp.
Furthermore, the detonation sensor isn't completely idiot proof. On the Z32, the detonation sensor "listens" for a vibration frequency that is caused by detonation. Unfortunately, the detonation sensor is only good to 3000rpms so after 3000rpms, the detonation sensor does not work. And even still, detonation can produce a slightly different vibration frequency and the detonation sensor may not detect it.
If you want my advice: if you intend on running 87 octane, then I'd drive like grandma and try to stay at low rpms. The more aggressive you drive on 87 octane, the more aggressive maps the ECU will use.
You say you'd save $20/mo or $240/yr switching to 87 octane. A new short block should be around $3k and a new long block should be around $7k and that excludes labor and other parts. Do the math. How many years will you be rolling die?
Here's an excellent article on detonation (uncontrolled combustion after the spark) and pre-ignition (uncontrolled combustion before the spark AKA dieseling) that includes ignition timing and octane: http://www.streetrodstuff.com/Articl...e_Basics_I.php
Here's the gasoline FAQ that explains what octane is: http://www.seansa4page.com/resource/octane.html
QED.
Michael.
Boomer
11-03-2002, 08:28 PM
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high altitude
Originally posted by ToddLuc
You should first ask WHERE these people live. In higher altitudes, such as here in Colorado, 87 octane is sufficient when 91 is required.
I, personally, will stick with 91, as I always have. My Toyota requires 86 octane, but I run 91. The cost is neglible.
You should first ask WHERE these people live. In higher altitudes, such as here in Colorado, 87 octane is sufficient when 91 is required.
I, personally, will stick with 91, as I always have. My Toyota requires 86 octane, but I run 91. The cost is neglible.
Boomer
11-04-2002, 10:40 AM
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Originally posted by Them Bones
I think it's far more rediculous to buy a car that requires 91 octane and ask if it's okay to use 87 (not this thread EXACTLY, but many others). How about "Pep Boys has four tires for $99. What do you guys think? Will I lose performance?". Duh!
It's just plain stupid to use the wrong gas in a relatively high compression engine. And intentionally too.
"Doc, I'm thinking about jumping off a bridge onto big rocks below. What do you think?"...is this thread.
Your example sounds more like "The shifter vibrates at 4500 RPM. Well, don't rev to 4500 RPM. Problem solved". That's far from what I was saying.
People frequently pull crap like this. Buy an older NSX for $20000, then cry when it costs $2000 to replace the clutch. Again, DUH.
If you can't afford to make payments, maintain, fuel this car, you SHOULD NOT HAVE BOUGHT IT! There are more important things in life than a car. Do you really want to spend every last cent you have putting gas in a Z? If so, I hope you're single, not in school, etc.
I was simply stating an opinion, not evoking some standard response like a politician or lawyer.
-TB
I think it's far more rediculous to buy a car that requires 91 octane and ask if it's okay to use 87 (not this thread EXACTLY, but many others). How about "Pep Boys has four tires for $99. What do you guys think? Will I lose performance?". Duh!
It's just plain stupid to use the wrong gas in a relatively high compression engine. And intentionally too.
"Doc, I'm thinking about jumping off a bridge onto big rocks below. What do you think?"...is this thread.
Your example sounds more like "The shifter vibrates at 4500 RPM. Well, don't rev to 4500 RPM. Problem solved". That's far from what I was saying.
People frequently pull crap like this. Buy an older NSX for $20000, then cry when it costs $2000 to replace the clutch. Again, DUH.
If you can't afford to make payments, maintain, fuel this car, you SHOULD NOT HAVE BOUGHT IT! There are more important things in life than a car. Do you really want to spend every last cent you have putting gas in a Z? If so, I hope you're single, not in school, etc.
I was simply stating an opinion, not evoking some standard response like a politician or lawyer.
-TB
This was an EXPERIMENT, newbie. No one said I couldnt afford it. Its for informational purposes, a lets see kinda thing.
11-04-2002, 10:53 AM
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I know several people that have run 87 octane in premium only cars since they bought the car. Guess what? Those cars have well over 100k miles. So if there are long term detrimental effects...when do you see them? 200k?! Big deal.
Forced induction of course needs higher octane...yes, you will blow up with too much psi and too low octane. For the Z, no, I heard no pre-detonation..and once again know people who never used it and are doing just fine.
Using higher octane in regular gas car will cause the engine to run hotter with no increase in HP. So please save your money!
Forced induction of course needs higher octane...yes, you will blow up with too much psi and too low octane. For the Z, no, I heard no pre-detonation..and once again know people who never used it and are doing just fine.
Using higher octane in regular gas car will cause the engine to run hotter with no increase in HP. So please save your money!
11-04-2002, 11:02 AM
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Re: high altitude
Originally posted by Boomer
I haven't been in the high country for awhile, is your 91 octane gasohol? I had a very bad experience with it once and I will never buy a gasohol blend again that says 91 octane. I will use 90 or 89 octane, which works fine in high country, no detonation above 4000 ft, and then fill up with 91 after I get below 4000. Nissan has some limits set on alcohol and methenol in their gasoline section and I wondered if you had any problems in your altitude.
Boomer
I haven't been in the high country for awhile, is your 91 octane gasohol? I had a very bad experience with it once and I will never buy a gasohol blend again that says 91 octane. I will use 90 or 89 octane, which works fine in high country, no detonation above 4000 ft, and then fill up with 91 after I get below 4000. Nissan has some limits set on alcohol and methenol in their gasoline section and I wondered if you had any problems in your altitude.
Boomer
Todd
11-04-2002, 11:23 AM
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Originally posted by roberto350z
I know several people that have run 87 octane in premium only cars since they bought the car. Guess what? Those cars have well over 100k miles. So if there are long term detrimental effects...when do you see them? 200k?! Big deal.
I know several people that have run 87 octane in premium only cars since they bought the car. Guess what? Those cars have well over 100k miles. So if there are long term detrimental effects...when do you see them? 200k?! Big deal.
Using your friends' experiences as a measure for success is as bad as saying that the sun revolves around the earth. I can see the sun rise from east and the sun set in the west so it must revolve around the earth, right? When all is said and done, you just can't cheat physics.
Using higher octane in regular gas car will cause the engine to run hotter with no increase in HP. So please save your money!
Michael.
11-04-2002, 01:15 PM
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the friends I refer to are high school students with preludes, RSX type-s and I think a high comp celica. Hardly doubt they are grandmas.
Two of the kids have diff year preludes acquired from parents who never used premium.
AND, I take back the comment about the engine running hotter with premium...for now. I checked the link of the page that claimed this, and that page is gone. I am unsure of the truth from first hand experience...
Two of the kids have diff year preludes acquired from parents who never used premium.
AND, I take back the comment about the engine running hotter with premium...for now. I checked the link of the page that claimed this, and that page is gone. I am unsure of the truth from first hand experience...
11-04-2002, 03:03 PM
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Originally posted by roberto350z
the friends I refer to are high school students with preludes, RSX type-s and I think a high comp celica. Hardly doubt they are grandmas.
Two of the kids have diff year preludes acquired from parents who never used premium.
AND, I take back the comment about the engine running hotter with premium...for now. I checked the link of the page that claimed this, and that page is gone. I am unsure of the truth from first hand experience...
the friends I refer to are high school students with preludes, RSX type-s and I think a high comp celica. Hardly doubt they are grandmas.
Two of the kids have diff year preludes acquired from parents who never used premium.
AND, I take back the comment about the engine running hotter with premium...for now. I checked the link of the page that claimed this, and that page is gone. I am unsure of the truth from first hand experience...
Nonetheless, if you insist on running 87 octane in your 350, then please, please, please follow this test: find an incline (the steeper, the better) and while in 6th gear @ 1000rpm w/ the A/C on, floor it (to at least 5-6k rpm). If you have a passenger and/or luggage, even better. If you hear any detonation, then I recommend switching back to 91 octane or adjusting your driving habits. The idea is to simulate a worst case scenario for engine load.
Also, bear in mind that detonation sensors aren't 100% reliable and do wear w/ age/mileage. It's like I said earlier. You're just rolling die. You may come out w/ a few extra bucks, but you may come out w/ an empty wallet.
Michael.
11-05-2002, 06:41 AM
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no, no, no...I do not insist in running 87. This was an experiment for informational purposes 
I do not plan to use 87 ever again...the loss of HP keeps me from that!
As far as FI. I ran a 300zx under 11psi with 87 octane for a while and never had any detontation (did the Z31 have sensors?) Do you think 11.0:1 is equivalent to 11 psi. All I know is that this chick with the RSX-s dirives *kinda* hard and uses 87 because...well shes the sort or girl who laughs at the prospect of spending her money on premium when 87 does "just fine."
ps granted, she rarely hits redline, but says she likes to "dust" other civics..
I do not plan to use 87 ever again...the loss of HP keeps me from that!
As far as FI. I ran a 300zx under 11psi with 87 octane for a while and never had any detontation (did the Z31 have sensors?) Do you think 11.0:1 is equivalent to 11 psi. All I know is that this chick with the RSX-s dirives *kinda* hard and uses 87 because...well shes the sort or girl who laughs at the prospect of spending her money on premium when 87 does "just fine."
ps granted, she rarely hits redline, but says she likes to "dust" other civics..
11-05-2002, 08:42 AM
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Originally posted by roberto350z
As far as FI. I ran a 300zx under 11psi with 87 octane for a while and never had any detontation (did the Z31 have sensors?) Do you think 11.0:1 is equivalent to 11 psi. All I know is that this chick with the RSX-s dirives *kinda* hard and uses 87 because...well shes the sort or girl who laughs at the prospect of spending her money on premium when 87 does "just fine."
As far as FI. I ran a 300zx under 11psi with 87 octane for a while and never had any detontation (did the Z31 have sensors?) Do you think 11.0:1 is equivalent to 11 psi. All I know is that this chick with the RSX-s dirives *kinda* hard and uses 87 because...well shes the sort or girl who laughs at the prospect of spending her money on premium when 87 does "just fine."
I just thought of something else. If you want to run 87 octane safely, then I recommend you retard the base ignition timing by a few degrees. You will lose power (may be marginally, may be significantly), but there's less chance of relying on the detonation sensor to detect detonation and retard ignition timing for you.
Michael.
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