RA Notice: High Octane
chuethao: my friend told me that the higher the octane the better it is there was a RX7 93 pushing about 300HP and they put in 107 octane in it and it pushes well over 600HP i dont know if it is true but who knoes?
Originally Posted by chuethao
my friend told me that the higher the octane the better it is there was a RX7 93 pushing about 300HP and they put in 107 octane in it and it pushes well over 600HP i dont know if it is true but who knoes?
-N
Evolved Member
Joined: Apr 2002
Posts: 2,167
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From: TB, FL
Well, this debate has been raging all over the world probably since the invention of gasoline.
Here are some of my experiences since I have driven cars froms POS chevettes to 240's to celica GTS to my current Talon TSI. Take it as you will.
Rule
1) every cars within their time periods react different to certain gas octane
2) manual reacts differently to auto tranny
My experiences
1) For my second car, I had an olds cutlass ciera (4 banger and slushbox). I always used 89. One day, I used 93, and the car felt faster. How? When I merged onto the interstate, I didn't feel the usual lag in an old man car. As for MPG, I didn't take the time or effort to even verify my obeservations. To me, it felt like there was a timing advance a bit.
2) Years later, I bought my LS coupe. I had put enough fuel and air mods and controlled it w/ a S-AFC. For stocK on 89 octane, I averaged 22 MPG. If I had a brick foot, I suffered an absmal 18 MPG! After mods and tuning, I averaged 28-32 MPG in the city from brick foot to granny speed.
Now for the 93 octane issue, I know for a FACT my car after tuning pulled harder and faster between 4200 to 5500 rpm (+10 to 12%) since I tuned it for 89. In the end, I couldn't find my electrical gremlins causing the CEL (after +1.5 yrs of modding it) and a somewhat dead O2 sensor (replaced the problem . . . temp solution because it came back). Soon, the ecu didn't want to advance timing a bit, so I used 87.
3) For my 89 240sx, it only had an ebay airfilter and cheapo rusty exhaust w/ auto tranny. This beater had close to 140K on the motor and bit more on the chassis. I definately used 87. When I put 93 octane, it advanced its timing again as expected on my observation (not much, maybe as high as 4% increase).
4) Driving my 95 plymouth voyager w/ a 6 banger and slushbox. I always put 87 octane. One day, I needed to gas up the TSI and didn't feel like switching the pumping after filling the red plastic bottle. I tanked off the minivan.
When I left the gas station, I normally expected severe lag from the 6 banger trying to haul butt onto a state road w/ all that weight. HOly crap, I chirped tires for a good 2.5 secs and hauled up to 60 mph with somewhat ease. It felt like an increase timing up to 8%. Then, I tried it w/ another friend who has enough experience sitting in the battle wagon and confirmed it as I had done w/ the past 240 to the LS. In both cases, the latter pulled much harder.
Critics:
1) How do I know how much timing advance from butt dyno? It's inaccurate as hell!
Good point. Forgot one thing. When you have tuning experience on an AFC for over 2.5 yrs, you tend to know how the car feels to certain values. You can feel and see lean and rich condition.
Now, I have a pocketlogger. I have already seen what advance timing going polar opposite to knock count. I have already based tune a 1g GSX w/ a VPC and a 20g TC. Eventually, the owner found the motor had bad CAS and replaced it . . . didn't want to advance timing at WOT.
2) Dyno is the best way to prove everything!
I do see such point, but it can be skewed. How? Perfect example is the 4g92 MIVEC. Mitsu put some kind of racing fuel and dynoed it to about 175 HP flywheel. Around the world, people with gen 1 and 2 MIVEC would dyno their cars with bolt-ons. They would only garner close to the factory output in flywheel.
This was proven on a test track when the cyborg MIVEC gen 2 went against the Civic SiR2 (or something to that effect). In everything sprinting test, it lost to the civic (about 170 flywheel HP) by .3 sec. How in the world, when the cyborg is lighter too. Maybe different different driver error or gear ratios or just like doubters in the US and around the world believed the g92 pumps out around 155-162 flywheel HP, not the factory claims of 175.
Next, dyno tuning doesn't put real world experience into the equation. The outside world isn't a perfect lab-like conditions on a dyno. On the 1/4 mile tuning brings out the worst in the car. It's even more narrow than dyno tuning.
Dyno = baseline expectation
1/4 mile tuning = Just WOT. You don't driving WOT 90% of the time on the road.
Here are some of my experiences since I have driven cars froms POS chevettes to 240's to celica GTS to my current Talon TSI. Take it as you will.
Rule
1) every cars within their time periods react different to certain gas octane
2) manual reacts differently to auto tranny
My experiences
1) For my second car, I had an olds cutlass ciera (4 banger and slushbox). I always used 89. One day, I used 93, and the car felt faster. How? When I merged onto the interstate, I didn't feel the usual lag in an old man car. As for MPG, I didn't take the time or effort to even verify my obeservations. To me, it felt like there was a timing advance a bit.
2) Years later, I bought my LS coupe. I had put enough fuel and air mods and controlled it w/ a S-AFC. For stocK on 89 octane, I averaged 22 MPG. If I had a brick foot, I suffered an absmal 18 MPG! After mods and tuning, I averaged 28-32 MPG in the city from brick foot to granny speed.
Now for the 93 octane issue, I know for a FACT my car after tuning pulled harder and faster between 4200 to 5500 rpm (+10 to 12%) since I tuned it for 89. In the end, I couldn't find my electrical gremlins causing the CEL (after +1.5 yrs of modding it) and a somewhat dead O2 sensor (replaced the problem . . . temp solution because it came back). Soon, the ecu didn't want to advance timing a bit, so I used 87.
3) For my 89 240sx, it only had an ebay airfilter and cheapo rusty exhaust w/ auto tranny. This beater had close to 140K on the motor and bit more on the chassis. I definately used 87. When I put 93 octane, it advanced its timing again as expected on my observation (not much, maybe as high as 4% increase).
4) Driving my 95 plymouth voyager w/ a 6 banger and slushbox. I always put 87 octane. One day, I needed to gas up the TSI and didn't feel like switching the pumping after filling the red plastic bottle. I tanked off the minivan.
When I left the gas station, I normally expected severe lag from the 6 banger trying to haul butt onto a state road w/ all that weight. HOly crap, I chirped tires for a good 2.5 secs and hauled up to 60 mph with somewhat ease. It felt like an increase timing up to 8%. Then, I tried it w/ another friend who has enough experience sitting in the battle wagon and confirmed it as I had done w/ the past 240 to the LS. In both cases, the latter pulled much harder.
Critics:
1) How do I know how much timing advance from butt dyno? It's inaccurate as hell!
Good point. Forgot one thing. When you have tuning experience on an AFC for over 2.5 yrs, you tend to know how the car feels to certain values. You can feel and see lean and rich condition.
Now, I have a pocketlogger. I have already seen what advance timing going polar opposite to knock count. I have already based tune a 1g GSX w/ a VPC and a 20g TC. Eventually, the owner found the motor had bad CAS and replaced it . . . didn't want to advance timing at WOT.
2) Dyno is the best way to prove everything!
I do see such point, but it can be skewed. How? Perfect example is the 4g92 MIVEC. Mitsu put some kind of racing fuel and dynoed it to about 175 HP flywheel. Around the world, people with gen 1 and 2 MIVEC would dyno their cars with bolt-ons. They would only garner close to the factory output in flywheel.
This was proven on a test track when the cyborg MIVEC gen 2 went against the Civic SiR2 (or something to that effect). In everything sprinting test, it lost to the civic (about 170 flywheel HP) by .3 sec. How in the world, when the cyborg is lighter too. Maybe different different driver error or gear ratios or just like doubters in the US and around the world believed the g92 pumps out around 155-162 flywheel HP, not the factory claims of 175.
Next, dyno tuning doesn't put real world experience into the equation. The outside world isn't a perfect lab-like conditions on a dyno. On the 1/4 mile tuning brings out the worst in the car. It's even more narrow than dyno tuning.
Dyno = baseline expectation
1/4 mile tuning = Just WOT. You don't driving WOT 90% of the time on the road.
Last edited by bahamut; May 4, 2004 at 10:42 PM.
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